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  • gene expression
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  • 2025-2025
  • 1985-1989  (3,171)
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  • 1
    Electronic Resource
    Electronic Resource
    Heart anatomy and developmental biology (1988)
    Springer
    Cellular and molecular life sciences 44 (1988), S. 910-919 
    Details
    ISSN: 1420-9071
    Keywords: Heart embryology ; developmental biology ; differentiation ; morphogenesis ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The subject of heart development has attracted the interest of many embryologists over the last two centuries. As a result, the main morphologic features of the developmental anatomy of the heart are already well established. Although there are still some controversial points, and there is probably much descriptive work yet to be done, emphasis is currently being placed on developmental mechanisms rather than simply on descriptive facts. The availability of new techniques and the overall advances in biological research are placing heart embryology in a new perspective. Today, we do not simply ask whether one or another embryonic structure arises further right or further left; instead, we are studying how cells, tissues, and their microenvironment interrelate at the several levels of biological organization (from the gene upwards) so as to give rise to a mature organ with a distinct shape and well-established functions. This paper attempts to review some of the basic aspects of the developmental anatomy of the heart. Descriptive embryology is used here as a tool. Emphasis is placed on developmental mechanisms, and on the present knowledge of how these mechanisms are related to the structural development of the heart.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01939884
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  • 2
    Electronic Resource
    Electronic Resource
    A molecular view of cardiogenesis (1988)
    Springer
    Cellular and molecular life sciences 44 (1988), S. 930-936 
    Details
    ISSN: 1420-9071
    Keywords: Cardiac development ; embryogenesis ; gene expression ; complementary DNA ; molecular methodologies ; myocardial contractility ; myosin ; atrial natriuretic factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cardiac development involves a complex integration of subcellular processes into multicellular and, finally, whole organ effects. Until recently it has been difficult to investigate the genetic control of this organ level differentiation of the heart. The proliferation of molecular biology methodologies has provided mechanisms to directly investigate the control of these processes. This article focuses on molecular lines of research on two key areas in cardiac development: the regulation of expression of sarcomeric contractile and regulatory proteins, and atrial natriuretic factor. Molecular approaches are described which have allowed investigators to begin to determine the tissue and stage-specific expression of genes, to locate those genes in the genome, determine their sequences, and to directly investigate the mechanisms controlling their expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01939886
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  • 3
    Electronic Resource
    Electronic Resource
    Aberrant protamine 1/protamine 2 ratios in sperm of infertile human males (1988)
    Springer
    Cellular and molecular life sciences 44 (1988), S. 52-55 
    Details
    ISSN: 1420-9071
    Keywords: Human sperm ; human protamine ; protamine 1 ; protamine 2 ; protamine 3 ; infertility ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Protamines were extracted from the sperm of fertile and infertile human males and the relative proportion of protamines 1, 2, and 3 were determined by scanning microdensitometry following electrophoresis of total protamine in polyacrylamide gels. The proportion of the three protamines was found to be similar in sperm obtained from different normal males. The distribution of protamines in sperm obtained from a select group of infertile males producing an elevated level of large sperm heads, in contrast, was different from that of the fertile males.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01960243
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  • 4
    Electronic Resource
    Electronic Resource
    Post-castration rebound of an androgen regulated prostatic gene (1988)
    Springer
    Molecular and cellular biochemistry 84 (1988), S. 3-15 
    Details
    ISSN: 1573-4919
    Keywords: prostate ; androgens ; gene expression ; in situ hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary After castration, the rat dorsolateral prostate M-40 mRNA initially decreased then rebounded to precastrated levels. The cellular site of M-40 expression and its renewed expression after castration was defined by in situ hybridization histochemistry. In situ hybridization with either a 32P-labeled or biotin-labeled M-40 cDNA probe demonstrated that M-40 mRNA levels were higher in the lateral than dorsal prostate. A second androgen regulated gene, RWB, also was highly expressed in the lateral prostate. The biotinylated cDNA probes provided microscopic resolution of the expressing cells, revealing two distinct morphologies of lateral epithelium which expressed both the M-40 and RWB mRNA. These morphologies appeared in ducts which contained either epithelial cell sheets that were highly convoluted or thinner epithelial cells with a minimal degree of convolution. The RWB mRNA decreased in both cell populations in response to androgen withdrawal. The decline and reappearance of M-40 mRNA also appeared in both epithelial cell types. These data demonstrated that after castration the M-40 mRNA initially decreased as expected for an androgen sensitive gene and then progressed to a fully inducible state. The mechanism of this progression remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235188
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  • 5
    Electronic Resource
    Electronic Resource
    The cat hemoglobin polymorphism: Southern blot analysis of theβ-globin gene region from cats of various Hb A/Hb B phenotypes (1988)
    Springer
    Biochemical genetics 26 (1988), S. 239-248 
    Details
    ISSN: 1573-4927
    Keywords: cat hemoglobins ; polymorphism ; DNA ; restriction endonuclease ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The molecular basis for the genetic control of variable proportions of the two cat hemoglobins Hb A(α2β 2 A ) and Hb B (α2β 2 B ) was investigated. Ratios of Hb A/Hb B vary between 50/50 and 90/10 among members of the mongrel cat population, with clusters around 50, 35, and 10% Hb B. Genomic DNA from cats of 50/50, 70/30, and 90/10 phenotypes were cut by restriction endonucleasesHindIII,EcoRI,BamHI,Bg1II,and Pst1 and hybridized to a fragment of the human β-globin gene. The results of the Southern blots suggested a pattern of homozygote, heterozygote, homozygote for the respective cat phenotypes, 50/50, 70/30, and 90/10. Therefore, the cat hemoglobin polymorphism seems to result from the possible combinations of an allelic gene pair.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00561463
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular cloning of two isoinhibitor forms of chymotrypsin inhibitor 1 (CI-1) from barley endosperm and their expression in normal and mutant barleys (1988)
    Springer
    Plant molecular biology 10 (1988), S. 521-535 
    Details
    ISSN: 1573-5028
    Keywords: barley ; chymotrypsin inhibitor ; gene expression ; endosperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Full-length cDNA clones for barley chymotrypsin inhibitor 1 (CI-1) have been isolated from an endosperm-specific cDNA library. Hybridization and nucleotide sequence analyses indicate that these cDNAs represent two distinct types of CI-1 mRNA which we have called CI-1A and CI-1B. Both mRNAs encode polypeptides of 83 residues (M r=8790 and 8960) which differ at eleven positions. The full-length cDNA sequences do not predict N-terminal signal peptide extensions indicating that CI-1 is synthesized in the mature form in contrast to the homologous proteinase inhibitors of tomato and potato. Northern hybridization experiments show that the CI-1 genes are under strict developmental and organ-specific control. CI-1 transcripts were first detected in the developing barley endosperm between 12 and 14 days after anthesis but no CI-1-related sequences were detected in the RNA preparations from shoots, leaves or roots. The expression of CI-1 was also studied in the high-lysine barley mutants Hiproly, Risø 56 and Risø 1508. Approximately 15-fold (Hiproly) and 4-fold (Risø 56 and 1508) higher levels of CI-1 mRNA were detected in the mutant endosperms compared to normal barley. These results correlate well with the increased deposition of CI-1 in the high-lysine lines and show that the differential expression is controlled mainly at the level of transcription or stability of the mRNA. Using Southern-blots of barley DNA we estimate that there are three copies of CI-1 per haploid genome in both normal and mutant barley lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033607
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  • 7
    Electronic Resource
    Electronic Resource
    Isolation of an alfalfa histone H3 gene: structure and expression (1988)
    Springer
    Plant molecular biology 11 (1988), S. 641-649 
    Details
    ISSN: 1573-5028
    Keywords: codon usage ; gene expression ; histone H3 gene ; Medicago sativa ; somatic embryos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A histone H3 gene was isolated from a dicotyledonous plant, alfalfa (Medicago sativa). The sequence analysis of this gene revealed no obvious GC preference in its codon usage. Apart from containing most of the typical consensus sequences found in both animal and plant histone genes, the alfalfa H3 gene exhibits distinct structural features such as (1) the unusual location of two GATCC motifs in its 5′ flanking sequence, (2) the existence of a CGCGGATC on the nonsense strand at position −232, (3) the existence of a long palindromic structure, and (4) several polyadenylation signal-like sequences in the 3′ flanking region. There are about 160 copies of histone H3 gene in alfalfa tetraploid genome. Using the alfalfa H3 gene as a probe to study the pattern of histone H3 transcripts in the alfalfa, we found that the H3 RNAs are undetectable in leaves, more in stems than in roots, and highest in somatic embryos. Moreover, the RNA products of H3 genes in all alfalfa tissues tested show unusually long nontranslated region compared to those of animal histone genes. An additional high molecular weight species of H3 transcript was detected only in somatic embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017464
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  • 8
    Electronic Resource
    Electronic Resource
    Tissue-specific expression of a pea legumin gene in seeds of Nicotiana plumbaginifolia (1988)
    Springer
    Plant molecular biology 10 (1988), S. 203-214 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium ; gene expression ; legumin (Pisum) ; Nicotiana ; seed storage protein ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 3.4-kilobase genomic DNA fragment from Pisum sativum L. containing the LegA gene, which encodes a major legumin storage protein, was transferred to Nicotiana plumbaginifolia using an Agrobacterium tumefaciens strain containing the Bin 19 binary vector system. Northern hybridisation analysis of legA-transformed plants demonstrated that legumin-specific RNA was present in developing seeds but not in developing leaves. Legumin protein was immunologically detected in the mature seeds of legA-transformed plants, and was present as the correct-size protein composed of disulphide-bonded polypeptides. It is concluded that the transferred pea genomic fragment contains all the information necessary for seed-specific expression of the legA gene, and for correct processing of the primary transcript and the precursor legumin protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027397
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular cloning and analysis of four potato tuber mRNAs (1988)
    Springer
    Plant molecular biology 11 (1988), S. 255-269 
    Details
    ISSN: 1573-5028
    Keywords: potato ; patatin ; proteinase inhibitor ; cloning ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tuberization in potato is a complex developmental process involving the expression of a specific set of genes leading to the synthesis of tuber proteins. We here report the cloning and analysis of mRNAs encoding tuber proteins. From a potato tuber cDNA library four different recombinants were isolated which hybridized predominantly with tuber mRNAs. Northern blot hybridization experiments showed that three of them, pPATB2, p303 and p340, can be regarded as tuber-specific while the fourth, p322, hybridizes to tuber and stem mRNA. Hybrid-selected in vitro translation and nucleotide sequence analysis indicate that pPATB2 and p303 represent patatin and the proteinase inhibitor II mRNA respectively. Recombinant p322 represents an mRNA encoding a polypeptide having homology with the soybean Bowman-Birk proteinase inhibitor while p340 represents an mRNA encoding a polypeptide showing homology with the winged bean Kunitz trypsin inhibitor. In total, these four polypeptides constitute approximately 50% of the soluble tuber protein. Using Southern blot analysis of potato DNA we estimate that these mRNAs are encoded by small multigene families.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027383
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  • 10
    Electronic Resource
    Electronic Resource
    The chloroplast-located glutamine synthetase of Phaseolus vulgaris L.: nucleotide sequence, expression in different organs and uptake into isolated chloroplasts (1988)
    Springer
    Plant molecular biology 11 (1988), S. 191-202 
    Details
    ISSN: 1573-5028
    Keywords: cDNA sequence ; chloroplast protein import ; gene expression ; glutamine synthetase ; nitrogen metabolism ; Phaseolus vulgaris L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Work using a full-length cDNA clone has revealed that the plastid-located glutamine synthetase (GS) of Phaseolus vulgaris is encoded by a single nuclear gene. Nucleotide sequencing has shown that this cDNA is more closely related to a cDNA encoding the plastidic GS of Pisum sativum than to cDNAs encoding three different cytosolic GS subunits of P. vulgaris. The plastid GS subunits are initially synthesized as higher M r (47000) precursors containing an N-terminal presequence of about 50 amino acids which is structurally similar to the presequences of other nuclear-encoded chloroplast proteins. The precursor has been synthesized in vitro and is imported by isolated pea chloroplasts and processed to two polypeptides of the same size as native P. vulgaris chloroplast GS subunits (M r 42000). Experiments with fusion proteins show that the N-terminal 68 amino acids of this precursor allow the cytosolic GS subunit β also to be imported and processed by isolated chloroplasts. Polyadenylated mRNA specifically related to the plastidic GS gene is most highly abundant in chloroplast-containing organs (leaves and stems) but is also detectable in roots and nodules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015671
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  • 11
    Electronic Resource
    Electronic Resource
    Molecular basis for the overproduction of 5-enolpyruvylshikimate 3-phosphate synthase in a glyphosate-tolerant cell suspension culture of Corydalis sempervirens (1988)
    Springer
    Plant molecular biology 11 (1988), S. 215-220 
    Details
    ISSN: 1573-5028
    Keywords: glyphosate ; herbicide ; 5-enolpyruvylshikimic acid 3-phosphate (EPSP) synthase ; enzyme overproduction ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell cultures of Corydalis sempervirens adapted to growth in the presence of 5 mM glyphosate [N-(phosphonomethyl)glycine] display a 30- to 40-fold increase in the cellular content of 5-enolpyruvylshikimic acid 3-phosphate (EPSP) synthase, the target enzyme of the herbicide. Translatable mRNA activity as well as transcript levels for EPSP synthase were increased 8-to 12-fold in the adapted (glyphosate-tolerant) as compared to the non-adapted (glyphosate-sensitive) cultures. Northern blot analysis revealed a single 1.8 kb transcript after hybridization with an oligonucleotide probe deduced from the N-terminal amino acid sequence of the enzyme. No significant differences in the relative abundance of EPSP synthase-specific DNA sequences could be detected, however, in Southern and dot blot analyses of restricted DNA isolated from the two cultures. We conclude that the overproduction of EPSP synthase in glyphosate-tolerant C. sempervirens cells is not based on the amplification of the corresponding gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015673
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  • 12
    Electronic Resource
    Electronic Resource
    Cloning and characterization of a cDNA encoding a mRNA rapidly-induced by ABA in barley aleurone layers (1988)
    Springer
    Plant molecular biology 11 (1988), S. 495-506 
    Details
    ISSN: 1573-5028
    Keywords: abscisic acid ; barley aleurone layers ; cDNA cloning ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) inhibits the gibberellic acid induced synthesis of α-amylase in barley aleurone layers, yet ABA itself induces more than a dozen polypeptides (Lin & Ho, Plant Physiol 82: 289–297, 1986). As part of our effort to elucidate the molecular action of ABA in barley aleurone layers, we have isolated and characterized an ABA-induced cDNA clone, pHV A1. This cDNA clone hybridizes to an RNA species of approximately 1.1 kb from ABA-treated barley aleurone layers. The level of this mRNA is tripled within 40 minutes after ABA treatment, reaches a peak at 8–12 h, and is present up to 48 h. The induction of this mRNA responds to concentrations of ABA as low as 10-9 M, but higher ABA concentrations induce higher expression of this mRNA. The products of hybrid-select translation and in vitro transcription/translation with pHV A1 comigrate on SDS gel as a 27 kDa polypeptide. However, the sequence of pHV A1 indicates that it has an open reading frame encoding a 22 kDa protein. This size discrepancy is probably due to the high content of the basic amino acid, lysine. This notion has been confirmed by two-dimensional gel electrophoresis showing that this polypeptide is one of the most basic proteins in ABA-treated barley aleurone layers. The deduced amino acid sequence of pHV A1 contains nine imperfect repeats 11 amino acids long which share homology with cotton Lea 7 protein (Baker, Steele & Dure, Plant Mol Biol, in press). The identity and function of the encoded product of pHV A1 is under investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039030
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  • 13
    Electronic Resource
    Electronic Resource
    CG Dinucleotides of class II MHC genes are mutation hot-spots (1988)
    Springer
    Cytotechnology 1 (1988), S. 133-138 
    Details
    ISSN: 1573-0778
    Keywords: CG suppression ; DNA methylation ; gene expression ; MHC ; mutation hot spots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract DNA methylation of human class II genes of the Major Histocompatibility Complex (MHC) was correlated with gene expression and methyl-related CG → TG and CG → CA changes. It was found that cytosine methylation of the CG dinucleotides of MHC class II genes should be involved in generating a fraction of nucleotide polymorphism, rather than in controlling transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146813
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  • 14
    Electronic Resource
    Electronic Resource
    Nicotiana chloroplast genes for components of the photosynthetic apparatus (1988)
    Springer
    Photosynthesis research 18 (1988), S. 7-31 
    Details
    ISSN: 1573-5079
    Keywords: Nicotiana ; chloroplast genome ; photosynthesis ; NADH dehydrogenase ; protein structure ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to understand more fully chloroplast genetic systems, we have determined the complete nucleotide sequence (155, 844 bp) of tobacco (Nicotiana tabacum var. Bright Yellow 4) chloroplast DNA. It contains two copies of an identical 25,339 bp inverted repeat, which are separated by 86, 684 bp and 18,482 bp single-copy regions. The genes for 4 different rRNAs, 30 different tRNAs, 44 different proteins and 9 other predicted protein-coding genes have been located. Fifteen different genes contain introns. Twenty-two genes for components of the photosynthetic apparatus have so far been identified. Most of the genes (except the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase) code for thylakoid membrane proteins. Twenty of them are located in the large single-copy region and one gene for a 9-kd polypeptide of photosystem I is located in the small single-copy region. The gene for the 32-kd protein of photosystem II as well as the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase have strong promoters and are transcribed monocistronically while the other genes are transcribed polycistronically. We have found that the predicted amino acid sequences of six DNA sequences resemble those of components of the respiratory-chain NADH dehydrogenase from human mitochondria. As these six sequences are highly transcribed in tobacco chloroplasts, they are probably genes for components of a chloroplast NADH dehydrogenase. These observations suggest the existence of a respiratory-chain in the chloroplast of higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042978
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  • 15
    Electronic Resource
    Electronic Resource
    Structural gene regions of Rhodobacter sphaeroides involved in CO2 fixation (1988)
    Springer
    Photosynthesis research 19 (1988), S. 63-71 
    Details
    ISSN: 1573-5079
    Keywords: CO2 fixation ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From studies conducted in both our laboratory and by Gibson, Tabita and colleagues, as well as drawing on the recent studies with Alcaligenes eutrophus, we describe two genetic regions which have been identified on the chromosome of Rhodobacter sphaeroides which code for a number of enzymes involved in CO2 fixation. One region was found to contain the genes coding for fructose 1,6-bisphosphatase (fbpA), phosphoribulokinase (prkA), a 37 kDa polypeptide (cfxA), and form I ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL, S). These genes appear to be expressed in the same transcriptional direction and are tandomly arranged. A second, apparently unlinked region of the chromosome contains a duplicate (with respect to functionality of gene products) but not identical set of these same four genes. Although the gene order in both regions is apparently identical, there is approximately 4 kb of DNA separating the 3′-end of prkB and the beginning of cfxB. The specific genetic organizations and proposed roles of these two genetic regions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00114569
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  • 16
    Electronic Resource
    Electronic Resource
    Protein synthesis by isolated chloroplasts (1988)
    Springer
    Photosynthesis research 19 (1988), S. 129-152 
    Details
    ISSN: 1573-5079
    Keywords: chloroplast biogenesis ; gene expression ; ribosomes ; transcription ; translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated chloroplasts show substantial rates of protein synthesis when illuminated. This ‘in organello’ protein synthesis system has been advantageously utilised to elucidate the coding capacity of chloroplast and the regulation of chloroplast genes. The system is also being used recently to transcribe and translate homologous and heterologous templates. In this mini-review, we attempt to critically ecaluate the available literature and present the current and the prospective lines of research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00114572
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  • 17
    Electronic Resource
    Electronic Resource
    The chloroplast genes encoding subunits of the H+-ATP synthase (1988)
    Springer
    Photosynthesis research 18 (1988), S. 205-222 
    Details
    ISSN: 1573-5079
    Keywords: ATP synthase ; chloroplast ; evolution ; gene expression ; operon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three CF1 and three CF0 subunits of the chloroplast H+-ATP synthase are encoded on the chloroplast genome. The chloroplast atp genes are organized as two operons in plants but not in the green alga, Chlamydomonas reinhardtii. The atpBE or β operon shows a relatively simple organisation and transcription pattern, while the atpIHFA or α operon is transcribed into a large variety of mRNAs. The atp genes are related to those of cyanobacteria and, more distantly, to those of non-photosynthetic bacteria such as E. coli, suggesting a common origin of most F1F0 ATP synthase subunits. Both the chloroplast and cyanobacterial ATP synthases have four F0 subunits, not three as in the E. coli complex. The proton pore of the CF0 is proposed to be formed by the interaction of subunits III and IV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042985
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  • 18
    Electronic Resource
    Electronic Resource
    Synthesis and assembly of bacterial and higher plant Rubisco subunits in Escherichia coli (1988)
    Springer
    Photosynthesis research 17 (1988), S. 145-157 
    Details
    ISSN: 1573-5079
    Keywords: Carbon fixation ; enzyme assembly ; gene expression ; recombinant DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The synthesis in Escherichia coli of both the large and small subunits of cereal ribulose bisphosphate carboxylase/oxygenase has been obtained using expression plasmids and bacteriophages. The level and order of synthesis of the large and small subunits were regulated using different promoters, resulting in different subunit pool sizes and ratios that could be controlled in attempts to optimize the conditions for assembly. Neither assembly nor enzyme activity were observed for the higher plant enzyme. In contrast, cyanobacterial large and small subunits can assemble to give an active holoenzyme in Escherichia coli. By the use of deletion plasmids, followed by infection with appropriate phages, it can be demonstrated that the small subunit is essential for catalysis. However, the small subunit is not required for the assembly of a large subunit octomer core in the case of the Synechococcus enzyme; self-assembly of the octomer will occur in an rbcS deletion strain. The cyanobacterial small subunits can be replaced by wheat small subunits to give an active enzyme in Escherichia coli. The hybrid cyanobacterial large/wheat small subunit enzyme has only about 10% of the level of activity of the wild-type enzyme, reflecting the incomplete saturation of the small subunit binding sites on the large subunit octomer, and possibly a mismatch in the subunit interactions of those small subunits that do bind, giving rise to a lower rate of turnover at the active sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047686
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  • 19
    Electronic Resource
    Electronic Resource
    Expression of theunc genes inEscherichia coli (1988)
    Springer
    Journal of bioenergetics and biomembranes 20 (1988), S. 19-39 
    Details
    ISSN: 1573-6881
    Keywords: E. coli unc operon ; H+-ATPase ; subunit stoichiometry ; gene expression ; codon usage ; translational initiation ; Shine-Dalgarno sequence ; recombinant DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Theunc (or atp) operon ofEscherichia coli comprises eight genes encoding the known subunits of the proton-translocating ATP synthase (H+-ATPase) plus a ninth gene (uncI) of unknown function. The subunit stoichiometry of the H+-ATPase (α 3β3γ1δ1ε1a1b2c10–15) requires that the respectiveunc genes be expressed at different rates. This review discusses the experimental methods applied to determining how differential synthesis is achieved, and evaluates the results obtained. It has been found that the primary level of control is translational initiation. The translational efficiencies of theunc genes are determined by primary and secondary mRNA structures within their respective translational initiation regions. The respective rates of translation are matched to the subunit requirements of H+-ATPase assembly. Finally, points of uncertainty remain and experimental strategies which will be important in future work are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762136
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  • 20
    Electronic Resource
    Electronic Resource
    Expression of the gene for the atrial natriuretic peptide in cardiac myocytes in vitro (1988)
    Springer
    Cardiovascular drugs and therapy 2 (1988), S. 479-486 
    Details
    ISSN: 1573-7241
    Keywords: Atrial natriuretic peptide ; cardiac myocytes ; gene expression ; hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Primary cultures of neonatal cardiocytes expreses the gene for atrial natriuretic peptide (ANP). In general the levels of expression follow the rank order: atrial 〉 ventricular ≫ nonmyocardial cells. Following the initial dispersion cardlocytes require 48 to 72 hours before ANP seeretion and ANP mRNA accumulation approach a new steadystate level. In situ hybridization analysis indicates that ANP gene expression is concentrated in a subpopulation of cardiocytes in both the atrial and the ventricular cell cultures. These findings suggest that these primary cultures may be of value in defining the faciors governing the expression of the ANP gene in the cardiac cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00051186
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    Gene expression during CAM induction under salt stress in Mesembryanthemum: cDNA library and increased levels of mRNA for phosphoenolpyruvate carboxylase and pyruvate orthosphosphate dikinase (1988)
    Springer
    Photosynthesis research 17 (1988), S. 159-171 
    Details
    ISSN: 1573-5079
    Keywords: Crassulacean acid metabolism ; gene expression ; Mesembryanthemum crystallinum ; mRNA levels ; soil salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mesembryanthemum crystallinum responds to high salinity in the soil by shifting the mode of carbon assimilation from the C3 mode to Crassulacean acid metabolism (CAM). Several enzymes of carbon metabolism have increased apparent activities in the CAM mode, including phosphoenolpyruvate carboxylase (PEPcase) and pyruvate orthophosphate dikinase (PPDK). We have identified cDNA clones for PEPcase and PPDK by immunological screening of a cDNA library constructed in the protein expression vector lambda gt11. The clones were characterized by immunoblotting and RNA blotting techniques. RNA blotting showed that during CAM induction the steady-state level of mRNAs for both PEP case and PPDK increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00047687
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  • 22
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    The puf operon region of Rhodobacter sphaeroides (1988)
    Springer
    Photosynthesis research 19 (1988), S. 39-61 
    Details
    ISSN: 1573-5079
    Keywords: Bacteriochlorophyll-protein complex ; gene expression ; light-harvesting complex ; reaction center ; Rhodospirillaceae ; transcriptional control ; translational control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The puf operon of the purple nonsulfur photosynthetic bacterium, Rhodobacter sphaeroides, contains structural gene information for at least two functionally distinct bacteriochlorophyll-protein complexes (light harvesting and reaction center) which are present in a fixed ratio within the photosynthetic intracytoplasmic membrane. Two proximal genes (pufBA) specify subunits of a long wavelength absorbing (i.e., 875 nm) light harvesting complex which are present in the photosynthetic membrane in ≃15 fold excess relative to the reaction center subunits which are encoded by the pufLM genes. This review summarizes recent studies aimed at determining how expression of the R. sphaeroides puf operon region relates to the ratio of individual bacteriochlorophyll-protein complexes found within the photosynthetic membrane. These experiments indicate that puf operon expression may be regulated at the transcriptional, post-transcriptional, translation and post-translational levels. In addition, this review discusses the possible role(s) of newly identified loci upstream of pufB which may be involved in regulating either synthesis or assembly of individual bacteriochrlorophyll-protein complexes as well as the pufX gene, the most distal genetic element within the puf operon whose function is still unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00114568
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  • 23
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    Die stereoisomeren Sinensiaxanthine und Sinensiachrome: Trennung und Bestimmung ihrer absoluten Konfiguration. 7. Mitteilung über Rosenfarbstoffe6. Mitteilung, s. [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 24-30 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoisomeric Sinensiaxanthins and Sinensiachromes: Separation and Absolute ConfigurationThe so-called sinensiaxanthins and sinensiachromes, important apocarotenols from various fruits, have been separated into 2 and 4 stereoisomers, respectively, and their absolute configurations have been determined: (3S,5R,6S)-5,6-epoxy-5,6-dihydro-10′-apo-β-carotene-3,10′-diol (2), its (9Z)-stereoisomer 7, the (8R)- and (8S)-epimers of (3S, 5R)-5,8-epoxy-5,8-dihydro- 10′ -apo-β-carotene-3, 10′-diol (4 and 5), and their (9Z)-stereoisomers 3 and probably 6. Thus, sinensiaxanthins are cleavage products from (Z/E)-isomeric antheraxanthins or violaxanthins (scission at C(9′)-C(10′)) and sinensiachromes analogously from mutatoxanthins or auroxanthins.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710103
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  • 24
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    Enantioselektive Verseifung der Diacetate von 2-Nitro-1,3-diolen mit Schweineleber-Esterase und Herstellung enantiomerenreiner Derivate von 2-Nitro-allylalkoholen (chirale Verknüpfungsreagenzien)Kurzmitteilung mit ausführlicher Beschreibung der Isolierung und Anwendung von Schweineleber-Esterase Rohpräparaten, s. [1].Teilweise erwähnt in einem Übersichtsartikel über EPC-Synthesen unter C,C-Verknüpfung mit Hilfe von Enamine, s. [2]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1-23 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective Saponification of Diacetates of 2-Nitro-1,3-propanediols by Pig-Liver Esterase and Preparation of Enantiomerically Pure Derivatives of 2-Nitro-allylic Alcohols (Chiral Multiple-Coupling Reagents)The reproducible enantioselective saponification of open-chain and cyclic diacetates of meso-2-nitro-1,3-propanediols (see 4b-13b) with pig-liver esterase (PLE) gives monoacetates (see 4c-l3c) of 〉 95% enantiomeric excess. The Re enantiotopic acetate group appears to be saponified preferentially, as proved by the X-ray crystal structure analysis of three camphanoates 4d, 6d, and 7d. Elimination of H2O or AcOH from the hydroxy acetates thus available gives derivatives of nitro-allylic alcohols (see 20-24, 27, and 29) which are subjected to diastereoselective Michael additions or SN2′ substitutions.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710102
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  • 25
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    New Pterocarpinoids from Dolichos marginata ssp. erecta (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 72-76 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four new pterocarpinoids, sphenostylin A, B, C, and D (1-4), have been isolated from the CHCl3 extract of the root bark of Dolichos marginata ssp. erecta (Leguminosae) by preparative liquid chromatography. The structures have been established by spectroscopic methods (UV, 1H-NMR, 13C-NMR, EI-MS, DCI-MS, CD) and chemical transformations. The isolated compounds showed weak antifungal activity against Cladosporium cucumerinum.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710109
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  • 26
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    Condensed Heterotricycles. Synthesis and Reactions of b-Fused 1(2H)-Isoquinolinones with unusual enaminic propertiesContribution No. 822 from Hindustan Ciba-Geigy Ltd., Research Centre. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 77-92 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homophthalic acid (1) undergoes reaction with 1,2-, 1,3-, and 1,4-diamines to give condensed 1(2H)-isoquinolinones like 2, 4, 13, and 25, which exhibit marked enamine character. These are attacked by electrophiles at the N or C terminus. Some notable reactions of imidazoisoquinolone 2 are those with maleic and acrylic acids to form the tetracycles 48 and 51, respectively. With propiolic acid, 5 underwent an interesting reaction to form the benzimidazonaphthyridine 53. An equally interesting behaviour was elicited from 2 in its reaction with formaldehyde, when in addition to the expected methylene-bridged molecule 59, the novel spiro derivative 60 was formed by the dimerisation of a presumed azadiene intermediate 63.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710110
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  • 27
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    The dimeric and polymeric anhydride of 2,3-O-isopropylidene-β-D-ribofuranose. An NMR study (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 120-123 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H- and 13C-NMR data of the dimeric anhydride 1 of 2,3-O-isopropylidene-β-D-ribofuranose are reported together with the 1H-NOE values. The data show that the products of the polymerization of 1,5-anhydro-2,3-O-isopropylidene-β-D-ribofuranose are α- and β-D-ribofuranans and not an α-D-ribofuranan and a β-D-ribofuranan and a β D ribo-pyranan as claimed before [2] [3].
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710114
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    Complexes with a Pincers. 2,6-Diphenylpyridine as Twofold-Deprotonated (C ∧ N ∧ C) terdentate ligand in C,C-trans-, and as mono-deprotonated (C ∧ N) chelate ligand in chiral C,C-cis-complexes of platinum(II) and palladium(II). Preliminary communication (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 130-133 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,6-Diphenylpyridine forms, as twofold-deprotonated, terdentate ligand, complexes with Pt(II) and Pd(II), having two adjacent five-membered metallocycles. As mono-deprotonated, bidentate ligand, it forms cis-bis-complexes having a chirality axis. Pt(II) complexes undergo thermal and photochemical oxidative addition reactions, yielding stable Pt(IV) compounds. Pd(II) complexes yield substitued 2,6-diphenylpyridine in photochemical reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710116
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  • 29
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    Silicon-Directed Nazarov Cyclizations. Part V. Substituent and heteroatom effects on the reaction (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 168-194 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability to incorporate alkyl, alkenyl, aryl, and heteroatomic groups into substrates for the silicon-directed Nazarov cyclization and their subsequent reactions has been investigated. In general, most of the groups are compatible with the conditions for the cyclization and do not interfere even when directly attached to the divinyl ketone. The influence of substituents on the rate of the cyclization has been addressed and is consistent with a simple mechanistic picture. O- and N-Containing functions are tolerated except when attached to the α-vinyl C-atom of the divinyl ketone. The diastereoface-directing effect of a fused cyclobutane is discussed.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710120
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    Synthesis of Aristotelia-Type Alkaloids. Part III.Part II: [1]. (3R,4R)- and (3R,4S)-1-p-menthene-3,8-diol and the corresponding racemates: Preparation and assignment of configuration (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 209-217 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 1:1 mixture of the racemic trans- and cis-1-p-menthene-3,8-diols ((±)-3 and (±)-4, resp.) was readily prepared in 3 steps starting from 3-methyl-2-cyclohexen-1-one. The relative configuration of the diols, purified via the corresponding cyclocarbonates, was assigned by 1H-NMR spectroscopy and found to be at variance with tentative claims in the literature. Optically active samples of 3 and 4 were prepared by resolution of the racemates with (R)-1-phenylethylamine. The absolute configuration of the resulting diols was determined by chemical correlation with standards of known absolute configuration.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710122
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    Herstellung enantiomerenreiner, α-alkylierter Lysin-, Ornithin- und Tryptophan-Derivate (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 224-236 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Enantiomerically Pure, α-Alkylated Lysine, Ornithine, and Tryptophan DerivativesThe imidazolidinones 9 and 10 as well as the oxazolidinone 18a were prepared in several steps by known methods from lysine and ornithine with an overall yield of ca. 20%. After double deprotonation with LDA, the corresponding dianionic derivatives could be diastereoselectively alkylated with electrophiles (MeI, C6H5CH2Br, C6H5CHO, CH3CHO). Acid hydrolysis led to the two enantiomeric 2-methyl- and 2-benzyllysines and to the enzyme inhibitor (S)-2-methylornithine. Several α-alkylated tryptophan derivatives were obtained through alkylation of the heterocycles derived from various amino acids with 1-(tert-butyloxycarbonyl)-3-(bromomethyl)indole (26). Alkaline hydrolysis of the five-membered auxiliary ring of 30b followed by treatment with HCl afforded (S)-2-methyltryptophan (31).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710124
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    Hydrogénation de sels de flavylium: formation de composés heptacycliques; structure radiocristallographique du [tétrahydro-10b,10c,16,16a-diméthyl-16,16a-méthylène-10b,16-5aH-di(benzo[1]pyranno)[4,3-b:3′,4′,-c;2,3:2′,3′]-benz[1]oxépinyl-5a]-2-phénol (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 254-257 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of Flavylium Salts: Formation of Heptacyclic compounds; X-Ray Crystal Structure of 2-[10b,10c,16,16a-Tetrahydro-16,16a-dimethyl-10b,16-methylene-5aH-di[1]benzopyrano[4,3-b:3′,4′ -c; 2,3:2′,3′][1]benzoxepin-5a-yl]phenolThe hydrogenation of flavylium salts 1 either by catalytic reduction or by chemical reduction afforded the unexpected heptacyclic compound 2, the structure of which was determined by X-ray analysis. The latter was confirmed by 1H-NMR and mass spectra.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710128
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    Konformationsanalysen von Modell-Tripeptiden: Der Einfluss von α,α-disubstituierten α-Aminosäuren auf die Sekundärstruktur. Teil II. Röntgenstrukturanalyse und Konformationsenergie-Berechnungen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 268-273 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational Analysis of Tripeptide Models: The Influence of α,α-disubstituted α-Amino Acids on the Secondary Structure. X-Ray Analysis and Conformational Energy CalculationsThe X-ray analysis of tripeptide Z-Ile-Val(2-Me)-benzocaine (1f) reveals the presence of a type-III β-turn. Moreover, MMP2 calculations on tripeptides, e.g. Z-Ile-Aib-benzocaine (1c), Z-Ile-D-Val(2-Me)-benzocaine (1g), Z-Ile-Gly(2,2-Pr2)-benzocaine (1h), Z-Ile-Gly-benzocaine (1a), and 1f, fit well into the frame of NMR and CD investigations. They allow considerations on the relative stability of different types of β-turns depending on the peptide sequence, e.g. the kind of α,α-disubstituted amino-acid moieties.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710130
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    Synthese von (-)-(R)-Nephthenol und (-)-(R)-Cembren A (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 292-297 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (-)-(R)-Nephthenol and (-)-(R)-Cembren AStarting for L-serine,(-)-(R)-nephthenol((-)-2) and (-)-(R)-cembren A((-)-3) were synthesized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710133
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    Low-Temperature X-ray Crystal-Structure Analysis of the Thermally Unstable Lithiated 2-Butenyl tert-Butyl Sulfide: A comparison with model ab initio MO calculationsPart of the projected Dissertation of Th. M., ETH Zürich. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 299-311 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single crystals of the N,N,N′,N′-tetramethylethylenediamine (TMEDA) complex 6 of the title compound have been isolated. Compound 6 decomposes in the crystalline state above -20°. From the bond lengths and angles obtained by X-ray crystal-structure analysis (data collected at -70°), compound 6 is best described as a (E)-1-(tert-butylthio)-1-lithio-2-butene with the double bond acting as an additional ligand on lithium (unsymmetrical allylic group). The S-atom is in a cisoid arrangement in a common plane with the four C-atoms of the butenyl system. The t-Bu group and the Li-atom are located above and below this plane. The structure is discussed with respect to the reactivity of 6 (α/γ reactivity). The gross structure is reproduced surprisingly well by an ab initio SCF MO calculation of the model lithiopropene-1-thiol 7(HS instead of t-BuS, CH2 instead of CHCH3, no solvation of Li). The prominent difference is the symmetry of the allyllic moiety in the calculated structure.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710202
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    Notiz zur Synthese Eines Optisch Aktiven Ace-Hemmers mit Amino-oxo-benzazepin-1-alkansäure-Struktur mittels enantiokonvergierender kristallisationsinduzierter Racemat-Trennung (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 337-343 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Note on the Synthesis of an Optically Active ACE Inhibitor with Amino-oxo-benzazepine-1-alkanoic-Acid Structure by Means of an Enantioconvergent Crystallization-Based ResolutionAn enantioselective synthesis of the potent angiotensin-converting enzyme inhibitor (1′S,3S)-3-[(1′-(ethoxy-carbonyl)-3′-phenylpropyl)amino]-2,3,4,5-tetrahydro-2-oxo-1H-1-benzazepine-1-acetic acid hydrochloride (3) is described which user a crystallization-based resolution of a racemic amino intermediate with concomitant racemization of the unwanted enantiomer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710205
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    Polycyclopentane Als Steroid-Analoga (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 363-368 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polycyclopentanes as Steroid AnalogaThe synthesis of linearly annellated pentaquinanes from a readily available triquinane is reported.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710209
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    Synthese Eines Optisch Aktiven Penem-Zwischenprodukts Mittels Asymmetrischer Amidoalkylierung (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 395-403 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of an Optically Active Penem Intermediate by Asymmetric AmidoalkylationThe amidoalkylation of an optically active, cationic glycine derivative with methyl acetoacetate furnishes an intermediate 10a (Scheme 2) that is transformed in six steps to the optically active, silyl-protected 4-acetoxy-3-(1-hydroxyenthyl)-2-azetidinon 18a, a well known intermediate in penem synthesis.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710213
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    Circular Dichroism of Planar, Exocyclic S-cis-Butadienes Remotely PerturbedInteraction between non-conjugated chromophores, Part 29. Part 28, see [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 419-428 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically pure 5,6-dimethylidenebicyclo[2.2.1]hept-2-yl derivatives have been prepared. The sign of the Cotton effects associated with lowest-energy transition of 2-(dicyanomethylidene)-((-)-(1S,4S)-15), (E)-2-(methoxyimino)-((+)-(1S,4S)-16), (Z)-2-(methoxyimino)-5,6-dimethylidenebicyclo[2.2.1]heptane ((-)(1S,4S)-17), and 2,3,5-trimethylidenebicyclo[2.2.1]heptane ((-)-(1R,4S)-18) is opposite to the chirality constituted by the coupling of the electric transition moments of the two homoconjugated π-chromophores (Kuhn-Kirkwood dipole-coupling mechanism). When the substituents at C(2) are not π-functions, no general rule can be retained for the chiroptical properties of the 5,6-dimethylidenebicyclo[2.2.1]hept-2-yl systems as shown for dimethyl acetal (-)-(1S,4S)-19, ethylene acetal (+)-(1R,4R)-20, exo and endo methyl ethers (+)-(1R,2S,4R)-21 and (+)-(1R,2R,4R)-22, and for spirol[5,6-dimethylidenebicyclo[2.2.1]heptane-2.2'-oxiranes](-)-(1S,2S,4S)-23 and (-)-(1S,2S,4S)-24.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710215
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    Ferroelectric Liquid Crystals. Part 2.‘Ferroelectric Liquid Crystals’, Part 1: [1]. Chiral phenyl benzoates incorporating a trans-1,4-disubstituted cyclohexane ring (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 451-460 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: About forty novel phenyl benzoates also incorporating a trans-1,4-disubstituted cyclohexane ring and a chiral centre have been prepared. The dependence of the liquid-crystal transition temperatures of this new class of compounds on lateral substituents, diverse central linkages, chain lengths, and position of the chiral centre has been studied systematically. The synthesis and liquid-crystal transition temperatures of these new compounds are described in detail.
    Additional Material: 7 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710218
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  • 41
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    [4 + 2]-Cycloadditionen von α,β-ungesättigten Hydrazonen. Teil 1. Pyridin-2,3-dicarboximide aus 1-(Dimethylamino)-1,4-dihydropyridin-Derivaten (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 486-492 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [4 + 2] Cycloadditions of α,β-Unsaturated Hydrazones to Pyridine-2,3-dicarboximides via 1-(Dimethylamino)-1,4-dihydropyridine DerivativesThe [4 + 2] Cycloaddition of α,β-unsaturated hydrazones of type 1 (1-aza-1,3-butadienes) with 2-halogenomaleimides 4 affords 1,4-dihydropyridines 6 which, after treatment with an acid, yield highly substituted pyridine-2,3-dicarboximide derivatives 7 (Scheme 1).
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710222
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  • 42
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    Photochemistry of 2,2-Dimethyl-2H-Furo[3,4-b]Pyran-4,7(3H, 5H)-Dione (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 498-501 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation (λ 〉 340 nm) of the title compound 2a in t-BuOH affords 3,3,10,10-tetramethyl-2,8-dioxatricyclo-[4.3.2.01,6]undecane-5,9-dione (3) via photoextrusion of 2-methylpropene and subsequent photocycloaddition of 2a to the alkene. The same regioisomer 3 is formed selectively and in much higher yields on irradiating 2a in the presence of excess 2-methylpropene. Irradiation of 3 (λ = 300 nm) in t-BuOH in the presence of the same alkene gives a 6:1 mixture of spirooxetanes 7a and 7b but not α-cleavage products. In 2-propanol, 2a is photoreduced to a 2:1 mixture of diastereoisomeric hydrodimers 9.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710224
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  • 43
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710301
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  • 44
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    Une synthèse générale des tétraazamacrocycles mono-C-fonctionnalisés (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 602-608 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A General Synthesis for Mono-C-Functionalized TetrazamacrocyclesA new synthesis, under usual conditions of concentration, medium, and temperature, of a series of mono-C-functionalized tetraazamacrocycles is given. The method may easily be generalized. The new procedure allows the modification of the length of the side-chain or the size of the cavity by choosing fitted staring materials. The key intermediate has a tosylated linear side-chain susceptible to be transformed into a large variety of functional groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710313
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  • 45
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    Enantiomerically pure 7-oxabicylo[2.2.1]hept-5-en-zyl derivatives as synthetic intermediates. Part IIIPart I, see [1]; Part II, see [2].. Total synthesis of D- and L-ribose derivativesFor a preliminary communication, see Y. Auberson, R. Bimwala, J. Wagner, P. Vogel, Société Suisse de Chimie, Berne, 16 Oct. 1987, Abstract p. 29. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 624-630 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure methyl 5-bromo-5-deoxy-2,3-O- isopropylidene-β-D- (D-5b) and -β-l-ribofuranoside (l-5b) have been derived from (-)-(1R,2S,4R)-2-exo-cyano-7-oxabicylo[2.2.1]hept-5-en-endo,-yl (1′S)-camphanate (1) and (+)-(1S,2R,4S)-2-exo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl(1′R)-camphanate (2), respectively, in 5 synthetic steps and 28% overall yield. Hydrolysis of D-5b and L-5b afforded methyl 2,3-O isopropylidene-β-D-ribofuranoside (D-5a) and methyl 2,3-O-isopropylidene β-L-ribofuranoside (L-5a), respectively. The intermediate (+)-(1R,4R,5R,6R) 5-exo,6-exo-(isopropylidenedioxy)-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7) and its enantiomer(-)-7 were also obtained enantiomerically pure by resolution of (=)-7 by the Johnson-Zeller method. In bothe approaches, the chiral auxiliaries ((-)- and (+)-camphanic acids, or (+)-(S)-N,S-dimethyl-S-phenylsulfoximide) were recovered at an early stage of the synthesis.
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    URL: http://dx.doi.org/10.1002/hlca.19880710316
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  • 46
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    Mécanisme de solvolyse des cis- et trans-(p-toluènesulfonates) d'aryl-2-cyclopentyle I. Etude de la première étape de la solvolyse: effets isotopiques de l' atone de deutérium en position 2, effets de sel basique et effet spécial de sel (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 648-657 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Solvolysis Mechanism of cis - and trans-2-Arylcylopentyl p-Toluenesulfonates. The Step: 1-Deuterium Isotope Effects, Basic Salt Effects, and Special Salt EffectWe have studied the first step of the solvolysis of cis and trans-2-arylcyclopentyl p-toluenesulfonates in HCOOH, AcOH, and EtOh. All substrates show a high kinetic 1-deuterium isotope effect (kH/kD(1) 〉1.15). This fact indicates that first step leads to classical intimate ion-pair Which dissociates to a solvet-separated ion-pair, without participation either of solvent, the 2-aryl group, or a H-atom at C(2). The slight influence of added basic ions on reaction rate allows us to exclude any direct solvent attack on the covalent substrate even in the most favorable case, i.e. ethanolysis of 2-(p-nitrophenyl)cylopentyl-p-toluenesulfonates. Furthermore, solvent-separated ion pair formation is indicated by the special salt effect induced by LiClO4.
    Notes: No abstract.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710319
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  • 47
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710401
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  • 48
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    Anion-receptor molecules: Synthesis of a chiral and functionalized binding subunit, a bicyclic guanidinium group derived from L- or D- asparaginePresented in part at the 11th International Congress of Heterocyclic Chemistry, Heidelberg, Federal Republic of Germany, August, 1987. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 685-693 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optically active (4S,8S)-4, 8-bis(hydroxymethyl)-1,5,7-triazabicyclo[4.4.0]dec-5-ene ((S,S)-1) has been synthesized in nine steps from L-asparagine with a total yield of 5.1%. Similarly, the enantiomer (R,R)-1 has been prepared from D-asparagine. (S,S)- and (S,S)-1 are representative examples of rigid and functionalized bicyclic guanidine systems and constitute useful intermediates in the construction of chiral selective anion-receptor molecules.
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    URL: http://dx.doi.org/10.1002/hlca.19880710402
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  • 49
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    Studies on Antifungal Agents. Part 22. 3-aryl-5-[(aryloxy)alkyl]-3-[(1H-imidazol-1-yl)methyl]-2-methylisoxazolidines and related derivatives (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 718-732 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and antifungal activity of a novel series of 3-aryl-5-[(aryloxy)alkyl]-3-[(1H-imidazol-1-yl)-methyl]-2-methylisoxazolidines and related compounds, are discussed. The synthesis of the title compounds was accomplished via a 1,3-dipolar cycloaddition of α-substituted ketonitrones with l-alkenyl phenyl ethers (Scheme 2 and 3). The compounds were evaluated for in vitro antifungal activity in solid agar cultures against a broad variety of yeast and systemic mycoses and dermatophytes. While antifungal activity was evident throughout the series, in general, derivatives having halogen atom(s) in either or both aryl rings demonstrated the highest potency, especially against Trichophyton rubrum and Candida albicans. The dichloro analog 20 (PR 967-248) was found to possess the most useful activity. Its minimum inhibitory concentration (MIC) values ranged between 0.2 and 2.0 μg/ml, as compared to 0.2-20.0 μg/ml for the standard drug ketoconazole (4).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710406
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  • 50
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    Captodative olefins in normal and inverse Diels-Alder ReactionsPart 3 of Thermal Reactions of Donor-Acceptor Systems. Part 2: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 742-748 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Olefins with captodative substitution are reactive dienophiles in Diels-Alder reactions with normal and inverse electron demand. This is shown for reactions of 2-(tert-butylthio)acrylonitrile (1) with various dienes and heterodienes, e.g. 1,3-cyclohexadiene, hexachloro-1, 3-cyclopentadiene, acrolein, methacrolein, and methyl vinyl ketone (Schemes 2 and 3). In case of the hetrodienes, 3,4-dihydro-2H-pyrans are formed beside small amounts of tetrahydrothiophenes; however, with methyl vinyl ketone, both reaction pathways are equally followed. The high reactivity of captodative olefins in Diels-Alder reactions are rationalized on the basis of Sustmann's FMO model under consideration of Viehe's concept of captodative substitution of alkenes.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710408
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    A novel rearrangement of 2(5H)-furanones (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 783-787 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel rearrangement of 2(5H)-furanones is described. When refluxed in aq. Ethanolic solution in the presence of excess KOH, the 2,5-dihydro-2-oxofuran-3-carboxamides 6 underwent a novel rearrangement to the corresponding 4,5-dihydro-4-oxo-2-(phenylamino)-3-furancarboxylic acids 1 in moderate-to-excellent yields.
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    URL: http://dx.doi.org/10.1002/hlca.19880710413
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    Kurze Totalsynthesen von (±)-Sativen und (±)-cis-Sativendiol (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 788-807 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short Total Syntheses of (±)-Sativene and (±)-cis-SativenediolOur approach to (±)-sativene (7) and (±)-cis-sdtivenediol (9) involves: (a) reaction of 3-methylbutanoyl chloride with Et3N/cyclopentadiene to give the endo-isopropyl-ketone 1 (here improved to 71%), (b) NBS bromination of 1 to a 5:1 mixture (87%) of the bromo-ketones 2 and 3, (c) NFD-reaction sequence initiated by the attack of 1,2-butadienyl titanate (complex of 15, obtained from 2-butine) on 2/3 to afford 52% of the brexenone derivative 4 (along with 8% of its epimer 16), (d) addition of dibromomethane to 4 forming 63% of the diene-alcohol 5 (along with 13% of the diene-carbaldehyde 38), and (e) carbenoid ring-expansion with MeLi applied to 5 resulting in 41% the diene-ketone 6 (along with 15% of a 1:3 mixture of the diene-ketones 32 and 33). Wolff-Kishner reduction of 6 led to 81% of (±)-sativene (7), when enough O2 was present, but to 97% of the diene 8 in the strict absence of O2. (±)-cis-Sativenediol (9) was obrained (86%) by OsO4 hydroxylation of 8. The brexenone derivatives 4 and 16 (6:1, 50%) were also produced when the NFD-reaction sequence was applied to the isomeric bromo-ketone mixture 13/13 (1:3). The latter was obtained by NBS bromination of 10, which in turn was available by base epimerization of 1, followed by destructive removal of unreacted 1 by repeated gas-flow thermolysis. An analogous (less convenient) route to (±)-sativene (7) passed through a series of dihydro compounds (the ene series) it started with the methylidene-ketone 36, which was the product (97%) of a partial hydrogenation of 4. Addition of dibromomethane to 36 led t 62% of the methylidene-alcohol 39 (along with a little tetracyclic ether 40). Carbenoid ring expansion of 39 with MeLi afforded ca. 42% of the methylidene-ketone 41 (along with 7% of the methylidene-ketone 43 or, under slightly different condition, along with 9% of the methylidene-ketone 42 and 10% of the methylidene-carabaldehyde 44). The methylidene-alcohol 39 and the methylidene-ketone 43 were also obtained by partial hydrogenation of 5 and 33, respectively. Wolff-Kisher reduction converted 41 into (±)-sativene (7 99%); the same conditons applied to 42 afforded only ca. 8% 7 (along with three other hydrocarbons, one of them (ca. 21%) probably being (±)-copacamphene (45)). In the diene series, the two succeeding reactions (4→5 and 5→6) competed with the same side reaction, a rearrangement leading to the brendene-aldehyde 38. In the ene series, the corresponding dihydro-by-product 44 was found in the reacton 39→41, but not during 36→39. These side reactons could largely be suppressed by keeping the reaction temperature low. An explanation is proposed.
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    Reactions of Haloarenes with Thiolate Anions in Tetraglyme: Competition between electron transfer and SNAr mechanisms (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 859-866 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the bromo-substituted naphthalene 1 with the alkanethiolate anions 2a-b and arenethiolate 2c in tetraglyme gave the corresponding 1-naphythyl thio-ethers 3a-c. Thio-ethers 3a-c were oxidized to the corresponding sulfones 4a-c with m- chloroperoxybenzoic acid. The reaction of the dichloro-substituted anthracene 5a with 2b gave the disubstutution product 6a. The reaction of 9-bromoanthracene 5c with the alkanethiolate 2b gave 6b, whereas the reaction of 5c with the arenethiolate 2c gave a mixture of substitution product 6c and anthracene 7. The observation of the formation of both 6c and 7 is explained by the competition between substitution (SnAr) and electron-transfer (ET) mechanisms. Consistent with this interpretation, the reaction of the monochloro-substituted 5b, which has a higher-energy σ* orbital, with 2c gave 6c without the formation of 7. Zn/KOH in tetraglyme was shown to reduce the aryl halides 5b-c and thio-ether 6c to 7.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710421
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    Synthèse de l'acide décarboxythamnolique (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 876-880 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Decarboxythamnolic AcidThe total synthesis of the meta-depside decarboxythamnolic ( = 3-[(3-formyl-2-4-dihydroxy-6-methyl-phenyl)oxy]-2-hydroxy-6-methoxy-4-methylbenzoic acid; 25) by the biomimetic condensation of the substituted β-orcinol units 9 and 22 is described.
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    URL: http://dx.doi.org/10.1002/hlca.19880710424
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    Metabolism of Carotenoids in Salmonids. Part 3Part 1: [4]; Part 2:[1].. Metabolites of astaxanthin and canthaxanthin in the skin of atlantic salmon (salmo salar, L.) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 887-896 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diets supplemented with astaxanthin and canthaxanthin, respectively, and a control diet without carotenoid additions, were fed to 1½-year-old Atlantic salmon (Salmo salar, L.) for one year. The integuments were investigated as to their quantitative and qualitative carotenoid composition. Astaxanthin and canthaxanthin deposited in the skin amounted to 20 and 14% of the total carotenoids only. Seventy % must be considered as metabolites of astaxanthin and canthaxanthin and 10% as basic xanthophylls also present in the control groups. Astaxanthin apparently underwent the following metabolic pathway: astaxanthin→idoxanthin→adonixanthin→zeaxanthin→zeaxanthin 5,6-epoxides. Reduction of the 4′-carbonyl group was stereospecific leading to the (4′R)-idoxanthin. Canthaxanthin was obviously converted to β,β-carotene via 4′-hydroxyechinenone, echinenone, and 4-hydroxy-β,β-carotene.
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    URL: http://dx.doi.org/10.1002/hlca.19880710426
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    Antifungal Polyphenols from Cordia goetzeiGürke (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1210-1219 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four highly oxygenated polyphenols 1-4, have been isolated from the stem bark of Cordia goetzei Gürke (Boraginaceae) and their structures elucidated by a combination of one- and two-dimensional (including COLOC) NMR spectroscopic techniques, mass spectroscopy, and chemical methods. The first new compound, cordigone (1), is a tetrahydrofuran derivative and the second one, cordigol (2), a furobenzopyran derivative. The benzofurans 3 and 4 are orange pigments, responsible for the coloration of the stem bark of the tree. All four polyphenols are fungicidal against cladosporium cucumerinum.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710532
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    8-Aza-7-deaza-2′-deoxyguanosine: Phosphoramidite synthesis and properties of octanucleotides (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1191-1198 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Base-modified octanucleotides derived from d(G1-G2-A-A-T-T-C-C-) (11) but containing 8-aza-7-deaza-2′-deoxyguanosine (2) instead of 2′-deoxyguanosine (1) have been prepared by solid-phase synthesis employing P(III) chemistry. Isobutyrylation of 2, followed by 4, 4′-dimethoxytritylation and subsequent phosphitylation yielded the methyl or the cyanoethyl phosphoramidites 6a or 6b, respectively. They were used as building blocks in automated DNA synthesis. The resulting octanucleotides 12-14 containing 2 showed increased Tm values compared to the parent oligomer 11. The oligomers 11-14 were employed as sequence-specific probes in endo-deoxyribonuclease Eco RI oligonucleotide recognition. Whereas displacement of dG-2 (enzymic cleavage site of 11) abolished phosphodiester hydrolysis, replacement of dG-1 enhanced the cleavage rate compared to 11.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19880710530
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    Synthesis of Optically Pure Tricarbonyliron Complexes of 5,6-Dimethylidenebicyclo[2.2.2.]oct-2-yl derivatives. Crystal structure and absolute configuration of (+)-tricarbonyl(1S,2S,4R,5R,6S)-C,5,6,C,-η-(5,6-dimethylidenebicyclo[2.2.2]oct-2-yl p-bromobenzoate)iron (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1349-1353 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title complexes have been derived from tricarbonyl [(1R,4S,5S,6R,)-C,5,6,C-η-(5,6-dimethylidenebicyclo[2.2.2]oct-2-ene)]iron (1.). The crystal structure and absoulte configuration of (+)-tricarbonyl (1S,2S,4R,5R,6S)-C,5,6,C,-η-(5,6-dimethylidenebicyclo[2.2.2]oct-2-yl p,-bromobenzoate)]iron ((+)-6) determined by X-ray diffrac-tion studies proved earlier attribution of the relative configuration (endo us. exo,) of the tricarbonyliron moieties in complexes 1 and 2 of 5,6-dimethylidenebicyclo[oct-2-ene. The structure of (+)-6 confirms the absolute configuration derived earlier from circular-dichroism spectra of 5,6-dimethylidenebicyclo[2.2.2]oct-2-yl esters and 5,6-dimethylidenebicyclo[2.2.2]octan-2-one.
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    URL: http://dx.doi.org/10.1002/hlca.19880710546
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    Photocycloadditions of 2-(trimethylsilyloxy)-1,3-butadiene to 2-cycloalkenones. Access to the basic pentalenolactone skeletonPreliminary communication: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1392-1398 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2] Photocycloaddition of 2-(trimethylsilyloxy)-1,3-butadiene to a number of 2-cycloalkenones proved to be quite a general reaction leading to good yields of the cycloadducts (Table). This finding is surprising since dienes, in general, are better known as quenchers of enone triplets rather than as photochemical reactants. Both the high substrate concentrations, which can be employed in these cycloadditions, and the remarkable regio and stereoselectivity of the processes qualify them as valuable for syntheses. In a first application, the photoproducts 1a, b were transformed in three steps into a viable precursor 4 of the pentalenolactone-G and -H antibiotics.
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    Transition-Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part XVIIPart XVI: see [1].. Some platinum(II) complexes with anionic ligands such as methoxide, formate, carboxylate, hydride, and borohydride, and the X-ray crystal structure of [PtHCl()] (PP = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1442-1457 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexes trans-[PtXY(2] (X = H or Me; Y = OMe, OCHO, CO2H, and BH4; 2 = 2,11-bis{bis[3-(trifluoromethyl)phenyl]phosphinomethyl}benzo[c]phenanthrene) were prepared, and their decompositions to trans[PtHX(2)] were studied. Some binuclear hydrido-bridged complexes, e.g.[(2)HPt(μ-H)PtH(2)]+, were also obtained. The preparation of complexes trans-[PtHX(28)2] (X = H or Me, 28 = bis[3-(trifluoromethyl)phenyl]benzylphosphine) is also reported. The X-ray crystal structure of trans-[PtHCl1)] (1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene) was carried out.
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  • 61
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    Singlet-Oxygen Quenching by Carotenoids: Steady-state luminescence experiments (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1005-1010 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The near-infrared luminescence of singlet oxygen (1O2) has been measured in order to determine the efficiency of 1O2 quenching by two carotenoid compounds, β-carotene and canthaxanthin. 1H-Phenalen-1-one and rose bengal have been used as photosensitizers in those steady-state luminescence experiments. Stern-Volmer analysis of the 1O2 luminescence in solutions of CCl4 and CD3OD, containing different concentrations of the carotenoids, has shown a very efficient quenching by canthaxanthin. The rate constants are about a factor of 2 below the diffusion limited values for the given solvents, confirming earlier results in benzene. In comparison, the efficiency of 1O2 quenching by β-carotene is slightly lower than that by canthaxanthin in non-polar solvents and is reduced by an order of magnitude in CD3OD, due to the aggregation of this quencher.
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  • 62
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    Preparation of 3-Oxo- and 3-Ethylideneazetidine DerivativesThis work is part of the Ph. D. thesis of H. B. [1] (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1035-1041 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of 3-azetidinones with different N-substituents and their transformation to 3-ethylideneazetidines has been studied in relation with a projected synthesis of 3-ethylideneazetidine-2-carboxylic acid (= polyoximic acid; 1). The stable crystalline 3-azetidinone hydrochloride (18), obtained by hydrogenolysis of the known 1-(diphenylmethyl)-3-azetidenone (4), is described for the first time, From this key intermediate, 3-oxoazetidine-derived amides, exemplified by benzamide 12,urethanes (e.g. 17), and ureas (e.g. 20) can be prepared in good yield (Scheme 3). The olefination of 3-azetidinones with alkylidene(triphenyl)phosphoranes is a perparatively useful process only for derivatives with a pyramidal N-atom, e.g. the diphenylmethyl derivative 4, and not for the amide 12 or the urethane 17 (Scheme 4). 3-Alkylidene-azetidines with an amide N-atom should, therefore, be prepared by exchange of the N-substituent after the introduction of the double bond.
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  • 63
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    Absorption Spectra and Luminescence Properties of Isomeric Platinum (II) and Palladium (II) Complexes containing 1,1′-biphenyldiyl, 2-phenylpyridine, and 2,2′-bijpyridine as ligands (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1053-1059 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absorption spectra, luminescence spectra, and luminescence lifetimes of the isomeric [M(bph)(bpy)] and [M(phpy)2] complexes M = Pt(II) or Pd(II), bph2- = 1,1′-biphenyl-2,2′-diyl dianion, phpy- = 2-phenylpyridine-2′-yl anion, and bpy = 2,2′-bipyridine have been investigated and compared with those of [M(bpy)2]2+ complexes and of the free protonated ligands H2bph, Hbpy+, and Hphpy. In the absorption spectra, the region below 320 mm is dominated by ligand-centered (LC) transitions, whereas metal-to-ligand charge transfer (MLCT) transitions are responsible for the bands present in the near UV/VIS region. The MLCT bands move to higher energies on replacing Pt with Pd and in going from [M(bph)(bpy)] to the [M(phpy)2] isomer. For the mixed-ligand complexes, evidence for both M → bph2- (at higher energies) and M → bpy bands is found. The structured luminescence observed at 77 K shows lifetimes of 4.0 and 1.1 μs for [Pt(phpy)2] and [Pt(bph)(bpy)], respectively, and 480 and 250 μs for the analogous Pd complexes. On the basis of the energy and lifetime data, the luminescence of the Pt(II) complexes is assigned to the lowest triplet MLCT excited state, whereas for the Pd complexes the luminescent state is thought to result from a mixture of MLCT and LC triplet levels.
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  • 64
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    Ruthenium(II) Complexes with Three Different Diimine Ligands (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1108-1115 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of tri-heteroleptic complex of Ru(II) with diimine ligands is describe. Ten compounds [Ru(R2bpy) (biq) (L)][PF6]2 (R = H, CH3); L = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (Me2bpy), 2,2′-bipyrimidine (bpm), 2,2′-biisoquinoline (biiq), 1,10-phenanthroline (phen), dipyrido[3,2-c:2′,3′-e]pyridazine (taphen), 2,2′-biquinoline (biq), 6,7-dihydrodipyrido[2,3-b:3,2-j][1,10]-phenanthroline (dinapy), 2-(2[pyridyl)quinoline (pq), 1-(2-pyrimidyl)pyrazole] (pzpm), 2,2′-biimidazole (H2biim) are characterized by elemental analysis, electronic and 1H-NMR spectroscopy. The relative photosustitution rates of biq in MeCN are given at three temperatures.
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    URL: http://dx.doi.org/10.1002/hlca.19880710525
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  • 65
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    (Benzylthio)- und (Arylthio)-substituierte Nitril-ylide: Thermische Erzeugung und Reaktionen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1177-1190 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal Generation and Reactions of (Benzylthio)-and (Arylthio)-Substituted Nitrile YlidesThermolysis of 4-(benzylthio)- and 4-(arylthio)-1,3-oxazol-5(2H)-ones 6, at 110-155° in the presence of dipolarophiles with activated C≡C, C=C, C=O, C=S, and N=N bonds, led to 5-membered cyclo-adducts and CO2 (cf. Schemes 3, 5-7). Heating 6a and 6c in the presence of ethyl propiolate yielded ethyl quinoline-3-carboxylate (19) and ethyl pyridine-3-carboxylate(22), respectively (cf. Scheme 8). These results are rationalized on the basis of the intermediate formation of thio-substituted nitrile ylides of type 7 (cf. Scheme 2), which undergo regioselective 1,3-dipolar cycloadditions with reactive dipolarophiles. In the absence of such a dipolarophile, the nitrile ylides isomerize via a [1,4]-H shift to give 2-aza-1,3-butadienes of type 20. The latter are trapped in a Diels-Alder reaction with ethyl propiolate (cf. Scheme 8).
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    The Reversible Proxibarbal-Valofan Isomerisation. Part I. Kinetic and thermodynamic studies in aqueous solutions (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1220-1227 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tautomerisation between proxibarbal (I) and the two diastereoisomers of valofan, IIX and IIY, was investigated in aqueous solutions, and various rate and equilibrium caonstants were calculated by compartmental analysis. The proportion of I at equilibrium was found to increase with pH, and indeed, the two equilibrium constants are linear functions of pH. In contrast, the equilibrium-concentratio ratio of IIY/IIX was close to 63:37 and remained constant in the pH range investigated. The rate constants were also determined as a function of temperature, allowing calculation of the tehrmolynamic parameters. Under physiological conditions, the difference in free energy favouring I vs. IIX and IIY is 6.7 and 5.4KJ · mol-1, respectively.
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    URL: http://dx.doi.org/10.1002/hlca.19880710533
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    Tandem Diels-Alder Reactivity Controlled by Remote Substituents. Regioselective synthesis of linearly annellated six-membered ring systems from (1RS,5SR,6RS,7SR)-6,7-bis(chloromethyl)-8,9-dimethylidene-2-oxabicyclo[3.2.2]nonan-3-one. Crystal structure of (1RS,5RS,6SR,11RS)-6,7-bis(chloromethyl)-3-oxo-2-oxatricyclo[7.4.0.1,5]tridec-8-en-11-yl methyl ketoneFor a preliminary communication, see [1].Part of the planned Ph. D. thesis of Bernard Demarchi, University of Lausanne. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1249-1267 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthess of 6,7,8,9-tetramethylidene-2-oxabicyclo[3.2.2]nonan-3-one (12), 6,7,8,9-tetramethylidene-2-azatricyclo[3.2.2]nonan-3-one (13), and (1RS,5SR,6RS,7SR)-6,7-bis(chloromethyl)-8,9-dimethylidene-2-oxabicyclo-[3.2.2]nonan-3-one (14) are presented. The rate constants of the two successive Diels-Alder additions of a given dienophile to 12 and 13 were nearly the same. Lewis-acid-catalyzed Diels-Alder addition of methyl vinyl ketone to 14 gave adduct 39 with high regio- and stereoselectivity. Lewis acids isomerized 39 into(1RS,5RS,6SR,7SR,11RS)-6,7-bis(chloromethyl)-3-oxo-2-oxatricyclo[7.4.0.01,5]tridec-8-en-11-yl methyl ketone (40) whose structure was determined by single-crystal X-ray crystallography. Heating 39 with CsF/Cs2CO3 in DMF/HMPT gave (1RS,5RS,11RS)-6,7-dimethylidene-3-oxo-2-oxatricycl. [7.4.0.01,5]tridec-8-en-11-yl methyl ketone (42). The exocyclic butadiene moiety of triene 42 added to methyl propynoate and 2,3-didehydroanisole with good regioselectivity giving polysubstituted anthracenyl and naphthacenyl derivatives, respectively.
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    Präparative chromatographische Enantiomerentrennung von synthetisch nützlichen cyclischen AcetalenTeil der Doktorarbeiten von St. M. (Dissertation Nr. 8616, ETH Zürich, 1988), J. Z. (Dissertation Nr. 8518, ETH Zürich, 1988) und der geplanten Dissertation von U. G. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1303-1318 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparative Chromatographic Resolution of Synthetically Useful Cyclic AcetalsRacemic cyclic acetals derived from aldehydes and glycine, glycolic acid, thioglycolic acid, formylacetic acid, and acetoacetic acid (oxazolidinones 4-13, dioxolanones 14, 15, oxathiolanone 16, dioxinones 17-23) are resolved by preparative high-pressure liquid chromatography on silica gel coated with the polymer from N-acryloylphenylalanine ethyl ester (Chiraspher®). The separation factors α range from1,1 to 2,4. Use of a Prepbar®-chromatography system allows injection of several grams at a time. The enantiomeric acetals thus obtained are fully characterized. First application to amino-acid synthesis are mentioned.
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    Stereoselectivity in Reactions of Metal Complexes. Part XPart IX: [1]. Kinetics and stereoselectivity of the inner-sphere electron-transfer reaction between [Co(bamap)H2O]+ (bamap = 2,6-bis(3-carboxy-1,2-dimethyl-2-azapropyl)pyridine) and optically active iron(II) complexes (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1339-1348 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the electron-transfer reaction between racemic or optically active [Co(bamap)H2O]+ and optically active Fe2+ complexes of the three new pentadentate ligands bamap, alamp, and valmp has been investigated. All the reacting species show C2 symmetry. With respect to aquo-Fe2+, the reaction rate for the Fe2+ complexes is enhanced by a factor of 104 to 105, and the observed kΔΛ/kΛΛ ratio is 1.0, 1,9, and 1.2, respectively. In all cases where stereoselectivity is observed, the reaction is faster between the complexes of opposite absolute configuration (ΔΛ or ΛΔ) than between species with the same configuration (ΛΛ or ΔΔ). The stereoselectivity effects are discussed of the basis of the structure of the transition state and the interatomic distances between the two metal centers at the moment of electron transfer.
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710601
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    Synthesis of (+)-1,3:2,5-dianhydroviburnitol ((+)-(1R,2R,3S,5R,6S)-4,7-dioxatricyclo[3.2.1.03,6]octan-2-ol) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1399-1405 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epoxidation of (-)-(1R,2R,4R)-2-endo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl acetate ((-)-5) followed by saponification afforded (+)-(1R,4R,5R,6R)-5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7). Reduction of (+)-7 with diisobutylaluminium hydride (DIBAH) gave (+)-1,3:2,5-dianhydroviburnitol ( = (+)-(1R,2R,3S,4R,6S)-4,7-dioxatricyclo[3.2.1.03,6]octan-2-ol; (+)-3). Hydride reductions of (±)-7 were less exo-face selective than reductions of bicyclo[2.2.1]heptan-2-one and its derivatives with NaBH4, AlH3, and LiAlH4 probably because of smaller steric hindrance to endo-face hydride attack when C(5) and C(6) of the bicyclo-[2.2.1]heptan-2-one are part of an exo oxirane ring.
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    Lavandulifolioside: A New Phenylpropanoid Glycoside from Stachys lavandulifolia (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1483-1490 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new phenlypropanoid glycoside has been isolated from the methanolic extract of the aerial parts of Stachys lavandulifolia (Lamiaceae), lavandulifolioside (1). On the basis of chemical and spectral data the structure of the new compound 1 has been elucidated as β-(3,4-dihydroxyphenyl)ethyl O-α-L-arabinopyranosyl-(1→2)-α-L-rhamnopyranosyl-(1→3)-4-O-caffeoyl-β-D-glucopyranoside.
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    Applications of ENDOR spectroscopy to radical cations in freon matrices. Part 2Part 1, see [1].. The radical cation of 2,3-diazabicyclo[2.2.2]oct-2-ene (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1498-1501 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical cation of 2,3-diazabicyclo[2.2.2]oct-2-ene (1), generated by γ-rays in a CF2ClCFCl2 matrix, has been fully characterized by its hyperfine data with the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The isotropic coupling constants for \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} are +3.14 mT for the two 14N Nuclei in the azo group, -0.336 mT for the two protons at the bridgehead C atoms, and +151 and +0.135 mT for the sets of four exo- and four endo-protons, respectively. MO calculations indicate that these values are consistent with an electron removal from an orbital represented by the antibonding combination (n_) of the lone-pair atomic orbitals at the two N atoms. The corresponding radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} is persistent in fluid solution and its hyperfine data, combined with MO calculations, point to an electron uptake into the antibonding π orbital (π*) of the azo group. It is, thus, reasonable to classify \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{+}\kern-4pt {.} }}$\end{document} as a σ and \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }}$\end{document} as a π radical.
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    Semicorrin Metal Complexes as Enantioselective Catalysts. Part 1. Synthesis of chiral semicorrin ligands and general conceptsTaken in part from the Ph.d. thesis of H. F., ETH-Zürich (in preparation); for a preliminary communication, see [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1541-1552 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient synthesis of chiral semicorrin ligands is described (see 6-9, Schemes 2 and 3). Both enantiomers are readily obtained in enantiomerically pure form starting either from D-or L-pyroglutamic acid (1). Semicorrins of this type possess several features that make them attractive ligands for enantioselective control of metal-catalyzed reactions. Their structure is characterized by C2 symmetry, a conformationally rigid ligand system, and two stereogenic centers adjacent to the coordination sphere. In a metal complex, the two substituents at the stereogenic centers shield the metal atom from two opposite directions and, therefore, are expected to have a pronounced effect on the stereochemical course of a reaction occurring in the coordination sphere. The structure of these two substituents can be easily modified in a variety of ways. A series of (semicorrinato)copper(II) complexes (see 10-14, Scheme 4) has been prepared, and in one case (14), the three-dimensional structure has been determined by X-ray analysis (Fig. 1).
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    Stereoselective synthesis of pyrrolo[2,3-d]pyrimidine α- and β-D-ribonucleosides from anomerically pure D-ribofuranosyl chlorides: Solid-Liquid Phase-Transfer Glycosylation and 15N-NMR Spectra (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1573-1585 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-liquid phase-transfer glycosylation (KOH, tris[2-(2-methoxyethoxy)ethye]amine ( = TDA-1), MeCN) of pyrrolo[2,3-d]pyrimidines such as 3a and 3b with an equimolar amount of 5-O-[(1,1 -dimethylethyl)dimethylsilyl]-2,3-O-(1-methylethylidene)-α-D-ribofuranosyl chloride (1) [6] gave the protected β-D-nucleosides 4a and 4b, respectively, stereoselectively (Scheme). The β-D-anomer 2 [6] yielded the corresponding α-D-nucleosides 5a and 5b with traces of the β-D-compounds. The 6-substituted 7-deazapurine nucleosides 6a, 7a, and 8 were converted into tubercidin (10) or its α-D-anomer (11). Spin-lattice relaxation measurements of anomeric ribonucleosides revealed that T1 values of H—C(8) in the α-D-series are significantly increased compared to H—C(8) in the β-D-series while the opposite is true for T1 of H—C(1′). 15N-NMR data of 6-substituted 7-deazapurine D-ribofuranosides were assigned and compared with those of 2′-deoxy compounds. Furthermore, it was shown that 7-deaza-2′deoxyadenosine ( = 2′-deoxytubercidin; 12) is protonated at N(1), whereas the protonation site of 7-deaza-2′-deoxyguanosine (20) is N(3).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710623
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710701
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  • 77
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    Synthesis and Characterization of Crown-Ether-Containing Phthalocyanines with Group-IV-A Elements (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1616-1621 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Group-IV-A phthalocyanines with four crown ether substituents have been prepared from 4′,5′-dicyanobenzo(15-crown-5), 4′,5′-diiminoisoindolino(15-crown-5), or metal-free phthalocyanine and the corresponding metal salts. The axial ligands of dichloro[tetra(15-crown-5)phthalocyaninato]silicon or -tin have been converted into dihydroxy derivatives by hydrolysis in aqueous Et3N. The catalytic effect of H2O-free CaC12 in quinoline is used for the polycondensation of dihydroxysilicon-phthalocyanine to cofacially arrayed polymers. The thermal stability of group-IV-A-metal phthalocyanines is confirmed by the higher initial decomposition points (290-440°) compared to those of the corresponding transition-metal phthalocyanines.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710705
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  • 78
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    Facile Synthesis of Carbon Monoxide Isotopically Labelled at Oxygen from Enriched Water without Isotopic Dilution (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1659-1660 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: O-Labelled carbon monoxide was prepared on the gram scale from enriched water and acetals of norborn-2-en-7-one(= bicyclo[2.2.1]hept-2-en-7-one) in almost quantitative yields and without isotopic dilution.
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    URL: http://dx.doi.org/10.1002/hlca.19880710710
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  • 79
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    Syntheses of Amino-dideoxyallose and Amino-deoxyribose Derivatives Using Acylnitroso DienophilesDedicated to Professor Elias J. Corey on the occasion of his 60th birthday (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1642-1658 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dimethyl acetals 4 of (E)-2,4-pentadienal and of (E,E)- and (E,Z)-2,4-hexadienals undergo regio- and stereospecific cycloaddition reactions with in-situ-generated acylnitroso dienophiles 5a and 5b, leading thereby to the corresponding dihydrooxazines 7a-d and 8c-d. cis-Glycolization of these latter adducts stereospecifically gave the dihydro derivatives 9a-d and 10d which, after sequential hydrogenolysis, deacetalization, and instant cyclization, led to the aminodeoxyribose derivatives 17a, 17f, and 18, and to the amino-dideoxyallose compounds 17c and 17h. These piperidino-deoxysugar derivatives exhibit a strong anomeric effect, i.e. OH—C(1) is always axial, which is explained in terms of a nN(π)-σ*(C—OH) orbital compression, as compared to the less pronounced one in the more classical pyranose series.
    Additional Material: 8 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710709
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  • 80
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    1,3-Dipolare Cycloaddition aromatischer Nitril-ylide und Nitril-oxide an Dicyan und Diazocyanide (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1681-1688 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3 Dipolar Cycloaddition of Aromatic Nitrile Ylides and Nitrile Oxides with Cyanogen and DiazocyanidesNitril ylides 2 generated from the imidoyl chlorides 1 react with cyanogen and aryldiazocyanides to 2,5(4)-dia-ryl-1H-imidazole-4(5)-carbonitriles 3a,b or 5(4)-(arylazo)-2,4(5)-diaryl-1H-imidazoles 4a and 2,3,5-triaryl-2,3-dihydro-1H-1,2,4-triazole-1-carbonitriles 5a-f, respectively (Scheme 1). Reactions of benzonitrile oxides 7 with these dipolarophiles lead to 3,3′-diaryl-5,5′-bi[1,2,4]oxadiazoles 8a-c or 3-aryl-5-(arylazo)-1,2,4-oxadiazoles 9a-j (Scheme 2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710714
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  • 81
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    Synthese der Spermidin-Alkaloide (±)-Inandenin-10-ol, Inandenin-10-on und (±)-OncinotinHerrn Prof. Dr. Duilio Arigoni zum 60. Geburtstag gewidmet. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1708-1718 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of the Spermidine Alkaloids (±)-Inandenin-10-ol, Inandenin-10-one, and (±)-OncinotineNew syntheses of the title compounds using two-ring-enlargement reactions are described. Starting from the aldehyde 1, the corresponding 4′-aza derivative 15 could be obtained by reductive amination with the appropriate and protected spermidine derivative 14 (Scheme 4). Enlargement of the carbocyclic ring in 15 by five members gave, after further transformations, the hydroxylactam 18. Transamidation of 18, the second ring-enlargement step, led to (±)-inandenin-10-ol (7;22.9% overall yield) and, after oxidation, to inandenin-10-one (8; 22.5%, overall yield). (±)-Oncinotine 6 was synthesized by two pathways (Scheme 6): protection of the terminal NH2 group by treatment with the Nefkens reagent and replacement of the OH group by Cl gave 24, which by thermal transamidation followed by direct ring closure led to the oncinotine derivative 26. The same intermediate could be obtained in higher yield via 28 by oxidation and protection of 18 followed by transamidation and reductive ring closure. Treatment of 26 with hydrazine finally gave (±)-oncinotine 6 in 15.9% overall yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710718
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  • 82
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    Diastereoselektive Alkylierung von 3-Aminobutansäure in der 2-StellungSir Derek Barton, zum 70. Geburtstag gewidmet (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1824-1839 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diastereoselective Alkylation 3-Aminobutanoic Acid in the 2-PositionThe enantiomerically pure 3-aminobutanoic acids (R)- and (S)-6 are readily available by preparative HPLC separation of the two diastereoisomers 5 obtained from addition of (S)-phenethylamine to methyl crotonate and subsequent hydrogenolysis (Scheme 2). (S)-Methyl 3-(benzoylamino) butanoate ((S)-3) is also available by enzymatic kinetic resolution with pig-liver esterase. The N-benzyl- and N- benzyloxycarbonyl derivatives rac3,8, and 9 of 3-aminobutanoates are doubly deprotonated with LDA and alkylated or aminated in high selectivity (17 examples, relative topicity like; see Tables 1 and 2). The configuration of three of the products is assigned (Schemes 4-6), and in four cases, the free α-substituted β-amino acid is prepared by acidic hydrolysis (see Table 3). It is shown that the doubly lithiated β-amino-acid derivative is solubilized, and its reactivity may be strongly influenced by the presence of 3 equiv. of LiCl.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19880710724
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  • 83
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    Masthead (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710801
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  • 84
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    Energy-Minimized Structures and Calculated and Experimental Isomer Distributions in the Hexaaminecobalt(III) system [Co(trap)2]3+ (trap = 1,2,3-propanetriamine) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1875-1880 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two isomers of [Co(trap)2]3+ (meso-[Co(trap)2]3+ and rac-[Co(trap)2]3+; trap = 1,2,3-propanetriamine) have been studied by strain-energy minimization. The two isomers have been separated preparatively by fractional crystallization, and fully characterized by 13C-NMR and electronic spectroscopy, and microanalyses. The calculated isomer distribution (rac/meso = 60%: 40%) is in good agreement with HPLC analysis of thermodynamic equilibrium mixtures at 298 K and 353 K (rac/meso = 55% : 45%). These results are discussed in relation to the approach of calculating isomer distributions of hexaaminecobalt(III) systems by strain-energy minimization neglecting the differences in environmental effects.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710805
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  • 85
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    Synthesis of New unnatural Macrocyclic Trichothecenes: 4-epiverrucarin A. 47th Communication on verrucarins and roridins46th Commun.: [1]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1904-1913 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4-epiverrucarin A (24), a new unnatural macrocyclic trichothecene, was synthesized starting from 4-epiverrucarol (20). The latter was obtained by metal-hydride reduction of the 4-oxo derivative 19. Subsequent conversion of 20 into the monoester 30 and then the diester 32 followed by macrolactonization of the latter yielded 4-epiverrucarin A (24). Attempts to invert the configuration of the naturally occuring 3α-OH group of a trichothecene were unsuccessful. The cytostatic (P-815) and immunosuppressive (MLR) activity of several natural and unnatural trichothecenes was determined in vitro.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710809
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  • 86
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    Steric Crowding in Coordination Compounds: Electron-transfer kinetics of the [Co(tmen)3]3+/2+ couple (tmen = 2,3-dimethylbutane-2,3-diamine) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1966-1970 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [Co(tmen)3]3+ complex ion (tmen = 2,3-dimethylbutane-2,3-diamine) has been synthesized and its redox characteristics compared to those of its parent ion [Co(en)3]3+. The 12 peripheral Me groups significantly affect the properties of the [Co(tmen)3]3+ ion. The ligand-field bands are shifted to lower energies by about 1700 cm-1 compared to [Co(en)3]3+. The reduction potential for [Co(tmen)3]3+ is +0.28 V (vs. NHE) compared to -0.18 V for [Co(en)3]3+. The rate of the self-exchange reaction for the [Co(tmen)3]3+/2+ couple, k = 8.5 × 10-8 M-1·S-1 was determined by applying the Marcus cross-relation with the reductants Cr2+, V2+, Eu2+, Ru2+, and [Co(sepulchrate)]2+.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710814
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  • 87
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    First Total Synthesis of Enantiomerically Pure(-)-Silphiperfol-6-en-5-onFor a Preliminary communication of this work, see [1a,b][2]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 569-576 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The angular triquinane (-)-silphiperfol-6-en-5-on ((-)-14) has been synthesized for the first time time in enantiomerically pure form. A highly efficient triplet-sensitized photoreaction, the oxadi-π-methane rearrangement of the complex β,γ-enone(+)-6 to (-)-7, constitutes the key step. The know staring material, (1R, 7aR)-3,6,7,7a-tetrahydro-1-hydroxy-7a-methyl-1H-inden-5(2H)-one ((-)-2), is readily accessible in 〉 97% enantiomeric purity. This new approach should enable access also to other angularly fused triquinanes of the silphinene type and related structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710309
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  • 88
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    Fredericone, neue hochfunktionalisierte Abietanoide aus Blattdrüsen von Coleus fredericii G. TAYL (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 577-587 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fredericon A, B, C, and D, Novel and Highly Functionalized Abietanoids from Leaf-Glands of Coleus fredericiiFrom the leaf-glands of the title plant (fam. Labiatae) two novel, genuie spirocycloopropyl-coleons have been isolated and structurally characterized. Fredericon A (1) bears the unusal 1,1,2-tricarbonylcyclopropane substructure that renders the molecule very suseptible to nucleophile-promoted rearrangements. Biogenetically intriguing is the presence of a 3-acetoxypropyl side-chain in fredericon B (3). Its formation from the well known isopropyl group is explained by transformation of the latter into a spirocyclopropane, followed by a reductive opening of the cyclopropane and reducation of the aldehyde, MeOH addition to 1, yields fredericon C (5), a derivative of 1H-phenanthro[3,2-b]pyran-7,12(2H,8H)-dione by two consecutive introlecular nucleophilic openings of the cyclopropane ring and the derived methoxy-oxirane. Similar methanolysis of a crude fraction of 1, produced, in addition to 5, the fredericon D, a novel derivative of 3H-phenanthro[3,2-b]pyran-2-(4H)-one(6).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710310
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  • 89
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    A new synthesis of N-acetylneuraminic acid (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 609-618 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthesis of N-acetylneuraminic acid (Neu5Ac; 28) via aldehyde 10 is described. The aldehyde 10 was obtained from N, acetyl-D-glucosamine (11; 5 steps, overall yield ca. 6%) or from D-glucono-1,5-lactone (17; 6 steps, overll yield ca 57%). Thus, on the one hand, N-acetyl-D-mannosamine (12), obtained from 11, was transformed into the known dithioacetal 14 and hence into the (ethylthio)dihydrooxazole 16, which was cleaved under weakly acidic conditions to the aldehyde 10. On the other hand, the known ester 18, obtained from 17, was sulfonylated and further transformed via the azide 20 into the N-acetyl-D-mannonate 22. Reduction of 22 to 23 and oxidation of 23 with ‘periodinane’ again gave 10. The aldehyde 10 was treated with the organozinc reagent 8 obtained from tert-butyl 2-(bromomethyl)acrylate (2) to yield predominantly 24, which was transformed (two steps) into the 2-methylidene-D-glycero-nononic acid 27 and hence into Neu5Ac (28).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710314
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  • 90
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    (-)-N-[(Cyclopropyl) methyl]-3,4-dimethoxy-5-methylmorphinan-6-one, an opioid agonist with preference for kappa opioid receptors (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 642-647 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Allyl- and N-[(Cyclopropyl)methyl]-3,4-dimethoxy-5-methylmorphinan-6-one (9 and 10, resp.) were synthesized from 5-methyldih drothebainone (1). This essential intermediate was prepared from the baine via 5-methylthebaine (5) employing a novel route. The Pharmacological studies showed 9 and 10 to be potent opioid agonists. Compound 10 was found to have preference for kappa rather than mu opioid receptors.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710318
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  • 91
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    Mécanisme de solvolyse des cis - et trans-(p-toluénesulfonates) d'aryl1-2-cyclopentyle II. Etude des étapes ultérieures à l'ionisation lors de la solvolyse des cis-(p-toluénesulfonates) d'aryl-2-cyclopentyle (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 658-673 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Solvolysis Mechanism of cis- and trans-2-Arylylopentylp- Toluenesulfonates, Subsequent Step in cis-2-Arylcyclopentyl p-Toluenesulfonate SolvolysisThe solvolysis of a series of 1-deuteriated, 2-deuteriated, and undeuteriated cis-2-arylcyclopentyl p-toluenesulfonates in HCOOH, AcOH, and EtOH has been studied. We have shown that classical secondary carbocation arising from substrate ionisation undergoes two concurrent processes, namely kc (direct products formation) and kip (hydrogenium bridged ion formation as tertiary carbocation or products precursor). The intrinsic properties of solvent and the aryl substitutant electronic effects the total solvolysis rate and the respective contributions of k c and k ip processes. Comparing the observed and calculated kinetic isotope of D-C(2) allows one to conclude that no step can called ‘rate-determining step’ but that the steps following ionisation have a preponderent effect on the total solovolysis rate.
    Notes: No abstract.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710320
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  • 92
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    1H-and 13C-NMR study of the dilithium naphthalene and its TMEDA complex (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 694-702 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dilithium naphthalene (2) and its TMEDA complex 3 have been prepared, and their 1H-and 13C-NMR spectra were analyzed in terms of chemical shifts and coupling constants. From its Q value, 2 is characterized as delcoalized [4n] π system and the 1H - as well as the 6Li-NMR shifts classify the ion as strongly paratropic. For the quarternary C-atoms, a down-field shift of 30.4 ppm is observed. The conclusions drawn from the NMR parameters are compared with the results of MNDO calculations for naphthalene and biphenylene and their ions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710403
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  • 93
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    Transition-metal complexes with bidentate ligands spanning trans-position. Part XVIPart XV:[1]. X-ray structural and 31P-NMR solution studies of 2,11-Bis(diethylphosphinomethyl)benzo[c]phenanthrenesilver(I) perchlorate (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 703-711 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of complexes {AgX(1c)} (X = Cl, Br, I, NO3 and ClO4; 1c = 2,11-bis(diethylphosphinomethyl)benzo[c]phenanthrene) is reported. The 31P-NMR spectra of the above complexes were recorded and the 1J(107Ag, 31P) values are compared with the corresponding data for related complexes. The X-ray crystal structure of [Ag(1c)](ClO4) was determined. There are two crystallographically independent molecules in the unit cell each containing two-coordinate silver, the O-atoms of the perchlorate anions being outside bonding range from the central atom. The two molecules, however, show different bonding parameters: Thus for ‘molecule 1’ P(1)—Ag(1)—P(2) = 167.6(1)°, Ag(1)—P(1) = 2.389(3) and Ag(1)—P(2) = 2.393(3) Å, while for ‘molecule 2’ P(3)—Ag(2)—P(4) = 164.8(1)°, Ag(2)—P(3) = 2.377(3), and Ag(2)—P(4) = 2.378(3) Å. These differences are probably due to packing forces in the crystal lattice.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710404
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    Anion-receptor molecules: Macrocyclic and macrobicyclic effects on anion binding by polyammonium receptor molecules (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 749-756 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability constants for anion binding by the acyclic hexaamine 1, its macrocyclic analogue 2, and the bicyclic compound 3 in their protonated forms are reported. Compound 3 forms stable and selective complexes with halide ions, the stability sequence being I- 〉 Br- 〉 Cl-. Compound 2 forms more stable complexes with sulfate, oxalate, and malonate dianions than its acyclic analogue 1 and shows a better selectivity pattern. Compound 3 forms stronger complexes with oxalate2- than 2 and shows a remarkably high binding selectivity between oxalate2- and malonate2-. The comparison of the ability of 1-3 to complex anions demonstrates the macrocyclic and macrobicyclic effects on anion binding stability and selectivity.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710409
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    Alkylation of Adenine, Adenosine, and NAD+ with 1,3-Propanesultone. Synthesis of N6-(3-sulfonatopropyl)-NAD+, a new NAD+ derivative with substantial coenzyme activity (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 762-772 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactivity of 1,3-propanesultone with adenine, adenosine, and NAD+ was studied in order to prepare N6-(3-sulfonatopropyl)-NAD+ (3b), a new NAD+ derivative substituted at the purine moiety with sunstantial coanzyme activity for several dehydrogenases. The regiochemistry of the alkylation at the purione nucleus was investigated by UV, 1H-NMR, and FAB-MS proved to be a powerful tool for determining the molecular weight of these polar and poorly volatile compounds. In addition, regular framgmentation of 3b and other NAD+ derivatives was observed.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710411
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  • 96
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    Electronic Resource
    A (1,5)-Vinyl Shift (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 808-811 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of the by-product of the pyrolysis of 1 has been proved to be 3. It is proposed that a (1, 5) Shift of an (alkoxycarbonyl)vinyl group (8⇄10) is the step in formation of 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710415
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  • 97
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    Electronic Resource
    Identifizierung von 2-Acetamido-2-desoxy-α-D-glucopyranosyl-1-phosphat in Kuhmilch als Wachstumsfaktor für Treponema vincentii (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 818-821 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Identification of 2-Acetamido-2-deoxy-α-D-glucopyranosyl 1-Phosphate in Cow-Milk as Growth Factor for Treponema vincentiiA 7:3 mixture of 2-acetamido-2-deoxy-α-D-glucopyranosyl and -α-D-galactopyranosyl 1-phosphate (1 and 2, resp.) was isolated from cow-milk and identified by 1H- and 13C-NMR spectroscopy. The 2-acetamido-2-deoxy-α-D-glucopyranosyl 1-phosphate is a growth factor for Treponema vincentii.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710417
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  • 98
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    The adamantane rearrangement of syn- and anti-Tricyclo[4.2.1.1.12,5] decane. Part IIFor Part I, see [1].. Rearrangements initiated by regioselective formation of carbocations at C(3) and C(9) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 848-858 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The endo- and exo-alcohols 5-12 of syn-(1) and anti-tricyclo[4.2.1. 12.5]decane (2) were treated with BF3/Et3SiH (ionic hydrogenation) in order to study the behaviour of the corresponding regioselectively generated carbocations at C(3) (a (syn), b (anti)) and C(9) (c (syn), d (anti)). The anti-hydrocarbon 2 is practically the sole product obtained starting with the four 3-alcohols (via a→b from 5 and 6 (syn) and via b from 9 and 10 (anti)). The four 9-alcohols in each case yield a mixture of 2-endo, 3-endo- (3) and 2-exo,3-exo-trimethylene-8,9,10-trinorbornane (4) (via c → e from 7 and 8 (syn) and via d → f from 11 and 12 (anti)), but no hydrocarbon 2, i.e. none of the 1,3-H shifts c → a and d → b is involved.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710420
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  • 99
    Electronic Resource
    Electronic Resource
    Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part 1. Bromotri-μ-carbonyloctacarbonyltetrairidate(1-) (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 867-871 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 2D and variable-temperature 13C-NMR study indicates that a CO-site exchange occurs in the title complex via several consecutive processes, the first being a ‘merry-go-round’ of the basal CO's, the second a switch of basal face not involving unbridged intermediates.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710422
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  • 100
    Electronic Resource
    Electronic Resource
    Mitteilungen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 930-930 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710428
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