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1

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Isolation and functional analysis of a set of auxin genes with low root-inducing activity from an Agrobacterium tumefaciens biotype III strain (1989)

Huss, Brigitte ; Bonnard, Géraldine ; Otten, Léon

Springer

Plant molecular biology 12 (1989), S. 271-283

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ISSN: 1573-5028

Keywords: Agrobacterium ; auxins ; roots ; oncogenes ; grapevine ; iaa genes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A new type of root-inducing iaa gene set was cloned from the Ti plasmid of the biotype III Agrobacterium tumefaciens strain Tm-4. These iaa genes are characterized by a very low DNA homology with the well-characterized iaa gene set, iaaM and iaaH, of the “common DNA” region of the biotype I strain Ach5 and by a low root-inducing activity. The biological activities of both iaa gene sets were compared by transferring each into a disarmed Ti vector and by testing the resulting strains on Nicotiana rustica leaf discs, decapitated Datura stramonium stems, tomato plants and Kalanchoë daigremontiana. Tm-4 iaa genes have a reproducibly weaker root-inducing ability on Nicotiana rustica, induce very little tumour growth on decapitated Datura plants or on tomato plants and do not induce roots on Kalanchoë daigremontiana. The Tm-4 iaa region was mapped by λ:: Tn5 transposon mutagenesis and tested on Nicotiana rustica. These tests combined with complementation experiments map the iaa genes to a 4.5-kb region. The Tm-4 iaa genes were able to complement the corresponding Ach5 iaa genes on Nicotiana rustica, indicating that the differences between these genes are quantitative rather than qualitative. Complementation experiments on Kalanchoë showed the iaaM gene of Tm-4 responsible for the overall weak auxin activity of the intact iaa set. In view of the observed structural and functional differences we propose to call the Tm-4 iaa genes TB-iaaM and TB-iaaH and the Ach5 iaa genes A-iaaM and A-iaaH.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00043204

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2

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Specificity of Agrobacterium-mediated delivery of maize streak virus DNA to members of the Gramineae (1989)

Boulton, Margaret I. ; Buchholz, Wallace G. ; Marks, Melanie S. ; [et al.]

Springer

Plant molecular biology 12 (1989), S. 31-40

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ISSN: 1573-5028

Keywords: agroinfection ; Agrobacterium ; strains ; maize streak virus ; Gramineae ; maize

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Parameters affecting the efficiency of agroinfection of maize streak virus (MSV) in maize have been determined. Monomeric units, cloned at a number of sites in the MSV genome were not infectious but multimeric units containing partial duplications were equally as infectious as complete tandem dimeric clones. Inoculation of tandem dimeric units conjugated into different strains of Agrobacterium showed that both A. tumefaciens and A. rhizogenes were able to transfer DNA to maize and this ability was Ti (or Ri) plasmid-specific. Nopaline strains of A. tumefaciens and both agropine and mannopine A. rhizogenes strains efficiently transferred MSV DNA to maize. A number of strains were capable of MSV DNA transfer to other members of the Gramineae, providing information which may be essential for Agrobacterium-mediated transformation of monocotyledonous plants.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00017445

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3

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Transformation of plant cells via Agrobacterium (1989)

Hooykaas, Paul J. J.

Springer

Plant molecular biology 13 (1989), S. 327-336

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ISSN: 1573-5028

Keywords: Agrobacterium ; plant cell transformation ; plant tumor induction ; plant vector systems

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00025321

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4

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Induction and growth properties of carrot roots with different complements of Agrobacterium rhizogenes T-DNA (1989)

Capone, I. ; Spanò, L. ; Cardarelli, M. ; [et al.]

Springer

Plant molecular biology 13 (1989), S. 43-52

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ISSN: 1573-5028

Keywords: Agrobacterium ; hairy roots ; T-DNA ; geotropism

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Single and multiple infections of carrot discs were carried out with Agrobacterium strains harbouring different segments of pRi1855 TL-DNA cloned in the binary vector Bin 19 and with a strain carrying the TR-DNA from the same Ri plasmid. Roots induced by the various co-inoculations were cultured and their growth patterns were followed. Abundant roots could be induced by TL-DNA rol genes A, B and C as a single insert (rolA+B+C) and by rolB alone provided an extended segment beyond its 5′ noncoding region was included in the construction. A depression of rooting capability was caused by the inclusion of rolC together with rolB (rolB+C). In all cases co-inoculation with the Agrobacterium carrying TR-DNA-borne auxin genes was necessary for root induction since none of the rol constructions was in itself capable of eliciting any response; an exceeding majority of these roots were however shown to contain rol genes but no TR-DNA. Rooting was also elicited if rol constructions were co-inoculated with a strain carrying TL-DNA genes 13 and 14 (ORF13+14) instead of the TR-DNA strain. These roots were shown to contain both rol genes and ORF13+14. Striking differences in growth properties were shown by roots containing different complements of TL-DNA genes. Typical hairy root traits, high growth rate, branching and, most noticeably, absence of geotropism, were shown by roots containing rolB alone, while roots with rolA+B+C were geotropic as normal carrot roots. Hairy root traits were conferred to rolA+B+C roots by the concomitant presence of ORF13+14 and by the addition of auxin to the culture medium. A model is presented which attempts to rationalize the growth patterns by assigning interplaying roles to the various TL-DNA genes involved.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00027334

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5

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Phleomycin resistance as a dominant selectable marker for plant cell transformation (1989)

Perez, Pascual ; Tiraby, Gérard ; Kallerhoff, Jean ; [et al.]

Springer

Plant molecular biology 13 (1989), S. 365-373

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ISSN: 1573-5028

Keywords: Agrobacterium ; binary vectors ; bleomycin ; phleomycin ; selective markers ; tobacco

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Tobacco cells are sensitive to bleomycin and phleomycin. The Tn5 and the Streptoalloteichus hindustanus (Sh) bleomycin resistance (‘Ble’) genes conferring resistance to these antibiotics have each been inserted into two plant expression vectors. They are flanked by the nopaline synthase (nos) or the cauliflower mosaic virus (CaMV) 35S promoters on one side, and by the nos polyadenylation signal on the other. These four chimaeric genes were introduced into the binary transformation vector pGA 492, which were thereafter mobilized into Agrobacterium tumefaciens strain LBA 4404. The resulting strains were used to transform Nicotiana tabacum cv. Xanthi nc using the leaf disc transformation procedure. In all cases, phleomycin- and bleomycin-resistant tobacco plants were regenerated from transformed cells under selective conditions; however the highest frequency of rooted plants was obtained when transformation was carried out with the ‘Sh Ble’ gene under the control of the 35S promoter. Phleomycin resistance was stably transmitted to sexual offspring as a dominant nuclear trait as confirmed by Southern blotting.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00015548

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6

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Thiophene accumulation in relation to morphology in roots of Tagetes patula (1989)

Croes, A. F. ; Berg, A. J. R. ; Bosveld, M. ; [et al.]

Springer

Planta 179 (1989), S. 43-50

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ISSN: 1432-2048

Keywords: Agrobacterium ; Auxin and thiophene in roots ; Root culture ; Root morphology ; Tagetes ; Thiophene ; Transformation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Roots of marigold (Tagetes patula L.) accumulate thiophenes, heterocyclic sulfurous compounds with strong biocidal activity. In detached roots cultured in vitro, the thiophene content was 5 μmol·(g fresh weight)-1 which is 25-times higher than in roots attached to the plant. In roots derived from tissues transformed by Agrobacterium tumefaciens and A. rhizogenes, the morphology and thiophene content varied with the bacterial strain used. Transformation stimulated the elongation of the root tips and the formation of lateral roots but lowered the thiophene level to 20–50% relative to the concentration in untransformed detached roots. A negative correlation was found between the number of laterals in a root system and the thiophene content. Extensive branching and a decrease in thiophene accumulation was evoked in untransformed roots by indole-3-acetic acid (1–10 μmol·l-1) added to the medium. Within the roots, the highest thiophene concentrations were found in the tips. The results indicate that auxin directly or indirectly plays a role in the regulation of the thiophene level in root tips.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00395769

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7

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Carrot (Daucus carota) hypocotyl transformation usingAgrobacterium tumefaciens (1989)

Thomas, John C. ; Guiltinan, Mark J. ; Bustos, Silvia ; [et al.]

Springer

Plant cell reports 8 (1989), S. 354-357

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ISSN: 1432-203X

Keywords: Agrobacterium ; Somatic Embryogenesis ; Electroporation ; β-Glucuronidase

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Daucus carota hypocotyl sections were transformed withAgrobacterium tumefaciens LBA4404 containing CaMV 35S promoter, β-glucuronidase coding sequence and the nopaline synthase (Nos) poly adenylation sequences in Bin 19. Sliced sterile seedling hypocotyl segments were preincubated for 2 days, co-cultivated withAgrobacterium for an additional 2 days, and then transferred to medium containing 100ug/ml of kanamycin and 400ug/ml carbenicillin. In 6 weeks kanamycin resistant calli were obtained in 5.8% of the explants from one variety. Calli were subcultured on solid medium, and in 4 weeks introduced into suspension culture. NPTII and Southern blot analysis confirmed that three selected lines were transformed with 1–3 copies of the GUSII construction. GUS activity in transformants was 5 to 250 fold over background.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00716672

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8

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Upstream non-coding region which confers polar expression to Ri plasmid root inducing gene rolB (1989)

Capone, Imerio ; Cardarelli, Maura ; Trovato, Maurizio ; [et al.]

Springer

Molecular genetics and genomics 216 (1989), S. 239-244

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ISSN: 1617-4623

Keywords: Agrobacterium ; Hairy root ; T-DNA ; Glucuronidase gene

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Root differentiation could be elicited on carrot discs by transformation with the agropine Ri plasmid rolB gene cloned in the binary vector Bin19, provided two conditions were met. Firstly, an adequate auxin supply had to be provided. This was achieved by co-inoculation with a strain carrying only the auxin synthetic genes of the TR-DNA. Most of the resulting roots were then shown to harbour only rolB and no aux genes. Secondly, an extended non-coding region (∼1200 bp) at the 5′ end of rolB had to be included in the construction. A shorter (∼300 bp) 5′ region, including TATA and CCAAT boxes, was not sufficient to trigger root differentiation. Both the extended (B1185) and reduced (B310) 5′ regions of rolB were then cloned upstream of the β-glucuronidase (GUS) reporter gene and infections carried out both on the apical and on the basal side of carrot discs. Strong expression of GUS, visualized histochemically as an intense blue colouring of transformed cells was observed with B1185-GUS constructions on the apical side of the discs. Only occasionally could coloured cells be observed on the basal side of the discs with B1185-GUS and on both apical and basal sides with B310-GUS constructions. Strong GUS expression was, on the contrary, achieved on cells of both auxin-rich (apical) and auxin-depleted (basal) sides of the discs with the strong constitutive viral promoter, CaMV35S. These results indicate the presence of an upstream regulatory region which confers polar expression to the rolB gene and suggest a role for auxin in its activation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00334362

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9

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Transformation of meristematic cells in the shoot apex of cultured pea shoots byAgrobacterium tumefaciens andA. rhizogenes (1989)

Hussey, G. ; Johnson, R. D. ; Warren, S.

Springer

Protoplasma 148 (1989), S. 101-105

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ISSN: 1615-6102

Keywords: In vitro shoots ; Pisum sativum ; Meristematic cells ; Shoot apices ; Transformation ; Agrobacterium

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Different tissues in cultured pea shoots were inoculated withAgrobacterium tumefaciens wild types C 58 and ACH 5 andA. rhizogenes wild type 9402. The C 58 and 9402 bacteria induced the formation of tumours and hairy roots respectively while the ACH 5 was inactive. The younger the tissue the more rapidly it responded to the active bacteria. The shoot apex was the most reactive organ and developed into a tumour, theA. rhizogenes tumours subsequently giving rise to transformed hairy roots. Histological examination showed that transformed cells (including those within the apical dome) initially became highly vacuolate before dividing rapidly to form a tumour. These changes were accompanied by cell division in surrounding tissues.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02079328

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10

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Agrobacterium tumefaciens 6bgenes are strain-specific and affect the activity of auxin as well as cytokinin genes (1989)

Tinland, Bruno ; Huss, Brigitte ; Paulus, François ; [et al.]

Springer

Molecular genetics and genomics 219 (1989), S. 217-224

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ISSN: 1617-4623

Keywords: Agrobacterium ; 6b gene ; Agrobacterium host range ; Oncogenes ; Plant growth regulation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The T-region located 6b gene of Agrobacterium tumefaciens has been found to interfere with cytokinin effects produced by the cotransferred ipt gene. We have compared the biological activity of three different 6b genes: A-6b from Ach5 (octopine, biotype 1), C-6b from C58 (nopaline, biotype 1) and T-6b from Tm4 (octopine, biotype III) by using different biological assays. Each 6b gene was inserted into a disarmed vector and tested on tobacco stems in coinfection experiments with the Ach5 cytokinin (ipt) gene (A-ipt). A-ipt/C-6b coinfections produced tumours with shoots, A-ipt/A-6b coinfections green tumours and A-ipt/T-6b coinfections tumours with a necrotic surface. The tumour phenotypes obtained were independent of the 6b/A-ipt coinfection ratios, indicating that the strain-specific 6b effects result from the activity of a non-diffusible 6b encoded product. Studies with ipt-less Tm4 mutants showed that 6b genes affect other tumour genes besides the ipt gene and pointed to an influence of T-6b on auxin effects resulting from the Tm4 iaa system. T-iaa/T-6b coinfection experiments showed that T-6b did indeed strongly increase tumour formation by the Tm4 iaa genes. The three 6b genes also have effects which do not require other T-region genes. The complex role of the 6b gene in crown gall induction and Agrobacterium host range will be discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00261180

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11

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Single-stranded DNA transforms plant protoplasts (1989)

Furner, I. J. ; Higgins, E. S. ; Berrington, A. W.

Springer

Molecular genetics and genomics 220 (1989), S. 65-68

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ISSN: 1617-4623

Keywords: Transformation ; Single-stranded DNA ; Agrobacterium ; Transient expression ; Extrachromosomal

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The transfer of the Agrobacterium T-DNA to plant cells involves the induction of the Ti plasmid virulence genes. This induction results in the generation of linear single-stranded (ss) copies of the T-DNA inside Agrobacterium and such molecules might be directly transferred to the plant cell. A central requirement of this ss transfer model is that the plant cell must generate a second strand and integrate the resulting double-stranded (ds) molecule into its genome. Here we report that incubating plant protoplasts with ss or ds DNA under conditions favouring DNA uptake results in transformation. The frequencies of transformation are similar and analysis of ss transformants suggests that the introduced DNA becomes double stranded and integrated. Analysis of transient expression from introduced ss DNA suggests that generation of the second strand is rapid and extrachromosomal.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00260857

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Distribution of two Agrobacterium tumefaciens insertion elements in natural isolates: Evidence for stable association between Ti plasmids and their bacterial hosts (1989)

Paulus, François ; Ride, Michel ; Otten, Léon

Springer

Molecular genetics and genomics 219 (1989), S. 145-152

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ISSN: 1617-4623

Keywords: Agrobacterium ; IS elements ; Ti plasmid ; T-region ; Bacterial evolution

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary A large number of Agrobacterium tumefaciens strains of the biotype III group carry two to ten copies of two related IS elements, IS866 and IS867. A study of the distribution and localization of these elements in 54 strains showed that one IS866 and two IS867 copies are always found at characteristic sites on the octopine/cucumopine and vitopine Ti plasmids, whereas varying amounts of IS866 and IS867 copies occur at different positions on the chromosome. By comparison of the IS patterns, an evolutionary tree could be deduced which shows the phylogenetic relationships between 23 different types of Agrobacterium strains. The structures of the T-regions of the different strains were also compared. Within the octopine/cucumopine group, eight T-region patterns could be defined. These patterns were found to be correlated with the chromosomal IS patterns. This strongly suggests that the IS866 and IS867 containing Ti plasmids are stably associated with their bacterial hosts. The possible role of the IS866 and IS867 elements in Ti plasmid evolution is discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00261170

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13

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Agrobacterium-mediated transformation of somatic embryos as a method for the production of transgenic plants (1989)

Dandekar, Abhaya M. ; McGranahan, Gale H. ; Leslie, Charles A. ; [et al.]

Springer

Methods in cell science 12 (1989), S. 145-150

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ISSN: 1573-0603

Keywords: Agrobacterium ; gene transfer ; somatic embryos ; walnut ; β-glucuronidase

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Somatic embryos have been successfully used as a target tissue for transformation and regeneration of transgenic walnut plants. Walnut somatic embryos, initiated originally from developing zygotic embryos, proliferate numerous secondary embryos from single cells in the epidermal layer. These single cells in intact somatic embryos are susceptible to transformation by genetically engineeredAgrobacterium tumefaciens and provide a means to regenerate nonchimeric transgenic plants. This gene transfer system has been made more efficient using, a) vector plasmids containing two marker genes encoding β-glucuronidase (GUS) and aminoglycoside phosphotransferase (APH(3′)II) and B) a more virulent strain ofAgrobacterium. This system should be applicable to any crop that undergoes repetitive embryogenesis from singleAgrobacterium-susceptible cells.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01404441

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14

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Masthead (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989)

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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.19890720101

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15

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The Conformation of Cycloartenol Investigated by NMR and Molecular Mechanics (1989)

Milon, Alain ; Nakatani, Yoichi ; Kintzinger, Jean-Pierre ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1-13

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Cycloartenol (4), a natural plant sterol, was shown to be an effective membrane reinforcer; this was attributed to its conformation. We now present a conformational analysis of 4 by molecular modeling and NMR. Molecular modeling suggests that two conformations I and II coexist, differing mainly at the level of ring C, and of nearly equal energy, I and II each having ring A and B in a chair and half-chair conformation, respectively, with ring C 1,3-diplanar in I (solid-state structure as determined by X-ray crystallography) and in chair conformation in II. A complete assignment of the 1H- and 13C-NMR spectra of 4 and the entire coupling network in rings A and B is determined by various modern NMR techniques. The conformation of rings A and B thus determined is in agreement with conformations I and II. Low-temperature NMR experiments show a fast equilibrium between two conformations, presumably I and II. It is concluded, therefore, that the cyclopropane ring of 4 produces a flexibility at the level of ring C which may be important for the membrane properties.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720102

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Palladium(0)-Catalyzed Cyclizations of Simple 1-Aryl-1,7-octadien-3-yl Acetates. Preliminary communicationPresented (W.O.) at the ‘3e Congrès national de la Société Française de Chimie’, Nice, September 5, 1988. (1989)

Oppolzer, Wolfgang ; Swenson, Rolf E. ; Pachinger, Werner

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 14-16

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Dienyl acetates 2 lacking a geminal disulfone or a malonate group cyclize selectively to (E)-l-methylidene-2-styrylcyclopentanes 4 in the presence of 7 mol-% of [Pd(PPh3)4].

Additional Material: 1 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720103

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17

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Über den Einfluss des Akzeptor-Teilchromophors bei Dimethin-merocyanin-Farbstoffen auf das Aggregationsverhalten in wässriger Lösung (1989)

Kussler, Manfred ; Balli, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 17-28

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: On the Influence of the Acceptor Part of the Chromophor of Dimethinemerocyanine Dyes upon the Aggregation Tendency in Aqueous SolutionA series of novel long-chain alkyl-dimethinemerocyanine dyes containing sulfonate groups is synthesized in good yield and their aggregation tendency in H2O and in organic solvent/H2O mixtures investigated. The merocyanine dyes 11 and 15 only exhibit an intense, red-shifted absorption band due to J-aggregation in H2O without addition of salt. The influence of cationic and anionic tensides and other compounds as urea, glucose, and polysaccharides upon the J-aggregation tendency is investigated.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720104

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Generation and Trapping of TriafulveneFulvene, Fulvalenes, Part 55; Part 54: [1].Short communication: [2]. (1989)

Weber, Andreas ; Stämpfli, Urs ; Neuenschwander, Markus

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 29-40

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Substituted methylidenecyclopropanes 12a-d, being easily available from 1,1-dibromo-2-(phenylthio)-cyclopropane (9a), are attractive precursors of triafulvene (2-methylidene-1-cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t-BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t-BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D-labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that H—C(2) of 12a-c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]-cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.

Additional Material: 1 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720105

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19

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A Nonconcerted Intramolecular Diels-Alder Reaction of Chiral Allenic-Acid Derivatives (1989)

Trifonov, Latchezar S. ; Orahovats, Alexander S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 59-64

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The reaction between the chiral allenic acid (+)-(S)-1 and the carbodiimides 2a-d and the keten-imine 6 gives, under mild conditions, the tricyclic compounds 3-5, 7, and 8. Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720108

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20

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Konkurrenz von Endoperoxid- und Hydroperoxid-Bildung bei der Umsetzung von Singulett-Sauerstoff mit cyclischen, konjugierten Dienen. Teil I (1989)

Matusch, Rudolf ; Schmidt, Gerhard

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 51-58

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Competition of Endoperoxide and Hydroperoxide Formation in the Reaction of Singlet Oxygen with Cyclic, Conjugated DienesRose-bengal-sensitized photooxygenation of (-)-(R)-α-phellandrene (1) in MeOH at room temperature yielded a complex mixture of products, contrary to previous reports describing cis-(3S, 6R)-epidioxy-p-menthene (2) and trans-(3R, 6S)-epidioxy-p-menthene (3) as the only products. The mixture was separated by prep. HPLC (silica gel, pentane/Et2O 9:1). Besides the known endoperoxides 2 (yield 39%) and 3 (26%), all those hydroper-oxides, which can be deduced from an ene reaction of 1O2 with 1, were isolated, i.e. 4β-p-mentha-2,5-dien-1β-yl hydroperoxide (4) (14%), 4β-p-mentha-2,5-dien-1α-yl hydroperoxide (5) (9%), (2R, 4R)-p-mentha-1(7), 5-dien-2-yl hydroperoxide (6) (2,1%), (2S, 4R)-p-mentha-1(7),5-dien-2-yl hydroperoxide (7) (1,5%) and (1R)-p-mentha-3,6-dien-yl hydroperoxide (8; 1,5%; Scheme 1). Furthermore, the constant cis/trans ratio for all diastereoisomeric pairs (2/2, 4/2, 6/2) was striking. With the help of the two possible conformers 1a and 1b of the starting material a model of a common first step for endoperoxide as well as for hydroperoxide formation is developed. A photooxygenation at -50° supports this model. The absolute value of the cis/trans ratio changes in the same way for the endoperoxides and the hydroperoxides.

Additional Material: 2 Ill.

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Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)

Weber, Andreas ; Galli, Roberto ; Sabbioni, Gabriele ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 41-50

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).

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Locoselective [4 + 2] Cycloadditions of Vinylindoles with Inverse Electron Demand: A new access of indolyl-substituted and annellated pyridazinesDedicated to Prof. Dr. C. H. Brieskorn (Würzburg, FRG) on the occasion of his 75th birthday (1989)

Pindur, Ulf ; Pfeuffer, Ludwig ; Kim, Myung-Hwa

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 65-72

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: 2-Vinylindole (1a) and its donor- and acceptor-substituted (E)-derivatives 1b-e react highly locoselectively with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (3) to form the novel (indol-2-yl)-1,4-dihydropyridazines 4a and 7 as well as the heterocyclic annellated pyridazines 4b, 5, and 6. The reactions of the structurally related 3-vinylindoles 2a-e with 3 also gave rise to new indol-3-ylpyridazines 8, 9, and 10. The locoselectivities of these Diels-Alder reactions were controlled mainly by steric effects.

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Photochemistry of Thiophen-2(5H)-onesDedicated to Prof. Dr. O. E. Polansky on the occasion of his 70th birthday (1989)

Kiesewetter, René ; Margaretha, Paul

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 83-92

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Mechanistic evidence for the light-induced ring opening of thiophen-2(5H)-ones 1 in alcohols affording α, β-unsaturated mercapto esters 2 is presented. Regio-and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S-heterocycles 16 and 18, of 3-thiahex-5-enyl radicals 4 to (tetrahydrothien-3-yl)methyl radicals 6 and of (2,3-dihydrothien-3-yl)methyl radicals 30 (type 7, but-3-enyl radicals) to cyclopropane-methyl radicals 29 are discussed. Irradiation (λ 350 nm) of 1 in cyclohexane in the presence of 2,3-dimethylbut-2-ene affords [2 + 2] cycloadducts 14 albeit in very low yields.

Additional Material: 1 Tab.

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Electronic and Molecular Structure of the C8H10+· Valence Isomers 1,3,5-Cyclooctatriene+· and Bicyclo[4.2.0]octa-2,4-diene+· from their Electronic absorption Spectra in Freon (1989)

Bally, Thomas ; Roth, Kuno ; Straub, Rolf

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 73-82

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The molecular cations of 1,3,5-cyclooctatriene (COT+·) and bicyclo[4.2.0]octa-2,4-diene (BCO+·) can be observed intact in γ-irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements. This proves the superiority of the Freon-glass method for the generation of metastable primary cations. The electronic absorption (EA) spectra reveal a) that a previous analysis of the BCO+· electronic structure on the basis of the ultraviolet photoelectron (UP( spectrum of BCO was incomplete, and b) that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations. A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+·.

Additional Material: 2 Ill.

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Cyclization Studies with N-Mannich bases of 2-substituted indoles (1989)

Burger, Ulrich ; Bringhen, Alain O.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 93-100

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The synthesis of the indoles 7, 15, 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22, 23, and 24, respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26. In the presence of SnCl4, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27, 28) and eight-membered rings (→ 29) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series.

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Template-Dependent Incorporation of Spin-Labeled Thymidine Analogs into Viral DNA (1989)

Pauly, Gary T. ; Bobst, Elisabeth V. ; Bruckman, David ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 110-116

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The synthesis of novel pppUd analogs substituted at position C(5) with tethered nitroxide radicals is reported. It is shown that these analogs can serve as good substrates for E. coli DNA polymerase (Pol I) and T-4 DNA polymerase using lambda-phage DNA as template. The template-dependent incorporation of the substrates was established by radio-labeling and ESR experiments.

Additional Material: 3 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720114

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Stereoselektive Synthesen von Taxan-Derivaten (1989)

Neh, Harribert ; Kühling, Andrea ; Blechert, Siegfried

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 101-109

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Stereoselective Synthesis of Taxane DerivativesSubstituted racemic 4,8,12-trinortaxanes were prepared stereoselectively in several steps from the dienone 10. A variant of the de Mayo reaction with bicyclononenones 4 and cyclohexen produced the desired configuration at C(8) of the taxane framework. Retro-aldol cleavage of the tetracycle 5 led to the taxane skeleton 6. Stereoselective reduction followed by treatment with base afforded 7b. Hydrolysis of the acetal group and further reduction yielded 9 in which the relative configuration corresponds to the one of the natural products.

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URL: http://dx.doi.org/10.1002/hlca.19890720113

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Asymmetric Diels-Alder reactions: X-Ray crystal-structure analysis of [N-((E)-But-2-enoyl)bornane-10,2-sultam]tetrachlorotitaniumPresented (WO) at the Annual Congress of the Royal Society of Chemistry, Canterbury, April, 1988. (1989)

Oppolzer, Wolfgang ; Rodriguez, Inès ; Blagg, Julian ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 123-130

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: An X-ray diffraction analysis of the crystalline complex 2b (MLn — TiCl4) shows a chelation of the carbonyl O-atom and the upper SO2 O-atom by TiCl4, a slightly pyramidal N-atom, and a π -face-stereoselective shielding of the C(α)-Si face by the CH2(3) group. The Ti-atom is in a pseudo-octahedral environment.

Additional Material: 2 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720116

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Metal Complexes with Macrocyclic Ligands. Part XXVIIPart XXVI. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles (1989)

Tschudin, Daniel ; Riesen, Andreas ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 131-138

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The X-ray structures of the Cu2+ complexes of 1,4,8,11-tetraazacyclotetradecane derivatives with an ethylpro-pionate and diethylphosphonate group, 5 and 6, respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one O-atom. In the case of 5, it is the carbonyl O-atom of the carboxylate group, whereas for 6 it is the phosphonyl O-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu2+ complexes with the 1,4,8,11-tetraazacyclotetradecanes 3-6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3-5 is proportional to the complex concentration and to [OH-] up to pH 13, whereas that of the phosphonate 6 is proportional to [OH-] up to pH 11.5, becoming independent of [OH-] at pH 〉 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra- or an intermolecular OH- attack and the results of the X-ray structure analyses.

Additional Material: 5 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720117

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A New Method for the Preparation of (E)-3-Acylprop-2-enoic AcidsPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988.Dedicated to Prof. R. E. Ireland on the occasion of his 60th birthday (1989)

Obrecht, Daniel ; Weiss, Bettina

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 117-122

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: A new method for the preparation of (E)-3-acylprop-2-enoic acids ( = (E)-3-acylacrylic acids) of type II via acid-catalyzed isomerization of the corresponding 3-acylprop-2-ynal acetals of type I (Scheme 1) has been found. The described reaction gives a rapid and quite general access to these compounds known to exhibit a number of interesting biological activities. Some studies toward the elucidation of the reaction mechanism have been made, and a hypothetical mechanism is proposed.

Additional Material: 2 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19890720115

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6-Thia-1-aza-5λ5-phosphabicyclo[3.2.0]hept-3-ene und Isothiocyanatophosphin-sulfide aus (Methylidenamino)phosphinen, Schwefelkohlenstoff und Acetylen- oder Ethylen-Derivaten (1989)

Fulde, Maria ; Ried, Walter ; Bats, Jan W.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 139-146

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: 6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives(Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2. Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a, b, and acrylates yield isothio-cyanatophosphin-sulfides 5a-c. The structures of 4a and 5a are proven by an X-ray diffraction analysis.

Additional Material: 2 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720118

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C45 und C50-Carotinoide. 6. Mitteilung5. Mitteilung, s. [1]. Synthese eines optisch aktiven cyclischen C20-Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotin) (1989)

Gerspacher, Marc ; Pfander, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 151-157

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: C45- and C50-Carotenoids: Synthesis of an Optically Active Cyclic C20-Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotene)The synthesis of the optically active cyclic C20-building block (R, R)-15 and of the optically active C50-carotenoid (2R, 6R, 2′R, 6′R)-decaprenoxanthin (1) starting from (-)-β-pinene ((S)-2) is reported.

Additional Material: 2 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720120

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Formation of the First Trimeric Monoterpenoid Indole Alkaloids (1989)

Schübel, Helmut ; Fahn, Walter ; Stöckigt, Joachim

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 147-150

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3-hydroxy-14′-(3α″-tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′-(3α″-tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids.

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Polynuclear Iron and Rhodium Complexes of 7-Oxa[2.2.1]hericene (2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one) (1989)

Rubello, Albino ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 158-164

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: μ-Carbonyl(Rh—Rh)di(η5-indenyl)[(2R,3S)-C,2,3,C-η-(2,3,4,5-tetramethylidenebicyclo[2.2.1]heptan-7-one)]]-dirhodium(I)(Rh—Rh) (7) and cis-μ-[(2R,3S,5R,6S))-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis[μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)] (8) have been prepared. Complex 7 reacts with Fe2(CO)9 in hexane/MeOH and gives cis-μ-[(2R,3S,5R,6S] (9), trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η: C,5,6, C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)-μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)-(tricarbonyliron) (10), and, μ-carbonyl(Rh—Rh)[(2R,3S)-C,2,3,C-η-(2,3-dimethyl-5,6-dimethylidenebicyclo-[2.2.1]hept-2-en-7-one)]di(η5-indenyl)dirhodium(I)(Rh—Rh) (11). Treatment of 7-oxa[2.2.1]hericene (4) with Fe2(CO)9 or (cyclooctene)2Fe(CO)3 gave a 1:2 mixture of cis-μ-[(2R,3S,5R,6S)-] (12) and trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis(tricarbonyliron)(13).

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Eine neue Aminoazirin-Reaktion. Bildung von 3,6-Dihydropyrazin-2(1H)-onen (1989)

Hugener, Martin ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 172-179

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-onesThe reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50-80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded.

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Synthesis of the Oviposition-Deterring Pheromone (ODP) in Rhagoletis cerasi L. Preliminary communication (1989)

Ernst, Beat ; Wagner, Beatrice

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 165-171

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: For the assignment of the configuration at C(8) and C(15) of the natural oviposition-deterring pheromone 1 in Rhagoletis cerasi L., the four possible stereoisomers of 1 are synthesized. By condensing the C6 building blocks (5R)-4 and (5S)-4 with the boron enolates of the C10 building blocks (4S)-13 and (4R)-13, followed by decarboxylative dehydration, all stereoisomers of 16 are available (Scheme 5). Glucosylation of 16 followed by formation of the taurin amide gives, after deprotection, the four stereoisomers (8R,15S)-1, (8R,15R)-1, (8R,15S)-1, and (8S,15S)-1 (Scheme 6).

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Mitteilungen (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 185-192

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

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URL: http://dx.doi.org/10.1002/hlca.19890720125

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New Spermine Alkaloids from Aphelandra tetragona (VAHL) NEESDedicated to Prof. Dr. D. Gröger on the occasion of his 60th birthday (1989)

Tawil, Bassem F. ; Zhu, Ji-Ping ; Piantini, Umberto ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 180-184

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: 18-O-Methylchaenorpine (1a) and iso-18-O-methylchaenorpine (1b) two novel stereoisomeric spermine alkaloids were isolated from the roots of Aphelandra tetragona (VAHL) NEES. Their structures were established by chemical and spectroscopic studies.

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URL: http://dx.doi.org/10.1002/hlca.19890720124

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Masthead (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989)

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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.19890720201

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1,5,7-Triazabicyclo[4.4.0]dec-5-en als Reaktionsmedium: Präparativ ergiebige einstufige Herstellung von Etioporphyrin aus Protoporphyrin (1989)

Kämpfen, Ulrich ; Eschenmoser, Albert

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 185-195

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: 1,5,7-Triazabicyclo[4.4.0]dec-5-ene as Reaction Medium: An Efficient One-Step Formation of Etioporphyrine from ProtoporphyrineHeating the commercially available protoporphyrine (4) in molten 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 200° for 4 h under exclusion of O2 produces etioporphyrine (6) in 60-70% yield by bisdecarboxylation and concomitant reduction of the two vinyl groups. Mesoporphyrine (5) is bisdecarboxylated to 6 in over 80% yield under these conditions in TBD as well as in DBU as the reaction medium.

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The Chemistry of Thujone. Part XIV.Part XIII [1]. Synthesis of biologically active aryl terpenoid analogues (1989)

Carvalho, Chris ; Cullen, William R. ; Fryzuk, Michael D. ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 205-212

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Employing thujone-derived intermediates, a series of achiral (9a-d; Scheme 1) and chiral (11b and 11d; Scheme 2) terpene analogues related to the biologically active ‘terpenoid’ hybrids have been prepared. The stereochemistry of the key epoxidation reaction was established by correlation of the product 11b with the previously reported alcohol (R)-20 of known absolute configuration (Scheme 3).

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Vinyl Carbanions. Part 36.Part 35: [9]. Synthesis of 3-deoxy-D-manno-2-octulosonic acid (KDO) and derivatives (1989)

Esswein, Angelika ; Betz, Rainer ; Schmidt, Richard R.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 213-223

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The β-C-lithiated acrylamide 3A has been proven to be an ideal pyruvate β-carbanion equivalent useful in a highly diastereoselective KDO synthesis. The starting material 3 was prepared from pyruvate diethyl acetal in four convenient steps. Direct lithiation with 2 equiv. of LDA generated the dilithiated species 3A quantitatively. Reaction with 2,3:4,5-di-O-isopropylidene-D-arabinose (11) was highly D-manno-selective. The product 12 was obtained readily from the reaction mixture via crystallization. Ring closure to the butenolide 13, subsequent PhS-group removal with Bu3SnH and pyridinium bromide, and hydrogenolytic debenzylation afforded the known butenolide 19; this KDO precursor gives KDO in two convenient steps. Butenolide 19 was also transformed via two high-yielding steps into the 4,5:7,8-di-O-cyclohexylidene-KDO derivative 22, a valuable starting material for KDO α-glycoside syntheses.

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Colchicine models: Synthesis and Antitubulin Activity of 2′-Monosubstituted and 2′, 5-Disubstituted 2,3,4,4′-Tetramethoxy-1,1′-biphenyls. Synthesis of 4,4′, 5′, 6′-tetramethoxy-1,1′-biphenyl-2,3′-dicarboxylic acidThis paper is dedicated to our friend and colleague Dr. Tetsuji Kametani, Hoshi College of Pharmacy, Tokyo, Japan, who died on October 11, 1988 (1989)

Itoh, Yoshikuni ; Brossi, Arnold ; Hamel, Ernest ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 196-204

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Notes: Reductive amination of 2,3,4,4′-tetramethoxtybiphenyl-2-carbaldehyde (4) with MeNH2 afforded methylamine 5 (Scheme 1), Hydroxymethylation of amine 8, prepared similarly from 4 by reductive amination with benzylamine followed by N-methylation, afforded alcohol 12 which was converted the 5-methyl-substituted methylamine 14 by conventional chemical reactions (Scheme 2), Methylamine 14 was also obtained from ester 16 after hydroxymethylation to alcohol 17 and conventional manipulation of alcohol and ester functions (Scheme 2). Both amines 5 and 14 as well as the 2′, 5-dimethyl-substituted biphenyl 26 prepared from the dialdehyde 25 by a Wolff-Kishner reduction, did not show noteworthy activity in the tubulin binding assay or as inhibitors of tubulin polymerization (Table). However, the 2′ethyl-substituted biphebyl 11 prepared from 4 by reaction with MeLi followed by dehyderation and catalytic reduction of styrene 10 (Scheme 1) showed appreciable activity in both assays, coming close to that of known phenyltropolone models. The X-ray analysis of 14·HCl and 11 showed significant difference in the orientation of the rings with respect to one another (Fig.).

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Biosynthesis of Homoterpenes in Higher Plants (1989)

Boland, Wilheim ; Gäbler, Andreas

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 247-253

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Notes: In higher plants, the two homoterpenes 4,8-dimethyinona-1,3,7-triene (1) and 4,8,12-trimethyltrideca-1,3,7,11-tetraene (2) are synthesized from the regular terpene alcohols nerolidol and geranyllinalool by fragmentation into the homoterpene and butenone. The biosynthetic pathway is evidenced by conversion of (2H)nerolidol in Hoya purpureo-fusca, Magnolia liliiflora nigra, Robinia pseudoacacia, and Philadelphus coronarius.

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Sphinxolide, a 26-Membered Antitumoral Macrolide Isolated from an Unidentified Pacific Nudibranch (1989)

Guella, Graziano ; Mancini, Ines ; Chiasera, Giuseppe ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 237-246

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: It is shown that an unidentified nudibranch of Hawaiian waters contains a 26-membered macrolide, sphinxolide ((-)-1) with potent activity against the KB cell line. The structure of sphinxolide, a 2:1 mixture of (E/Z)-isomers at the formamide moiety, is established to be (-)-1 on the basis of extensive NMR and FAB-MS analysis, in combination with data for the products of mono- (→(-)-2) and diacetylation (→(+)-3).

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Synthesis of Aristotelia-Type Alkaloids.Part III: [1]. Part IV. Synthesis of (±)-aristoserratineDedicated to Prof. D. Arigoni on the occasion of his 60th birthday (1989)

Burkard, Stefan ; Borschberg, Hans-Jürg

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 254-263

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Notes: A convergent diastereoselective synthesis of racemic aristoserratine ((±)-24) via an intramolecular iminium-ion cyclization is described. The pivotal imine (±)-19 was prepared by condensation of the two building blocks (± )-trans-8-amino-3-(2,6-difluorobenzyloxy)-1-p-menthene ((±)-11) and N-(p-methoxybenzenesulfonyl)-3-indo-leacetaldehyde (18) which were synthesized from (±)-trans-1-p-menthene-3,8-diol ((±)-7) and 3-indoleacetic acid, respectively. On the route to the target (±)-24, two previously unknown indole alkaloids have been characterized, namely (±)-‘anti’-hobartin-15-ol ((±)-22) and (±)-‘anti’-aristotelin-15-ol ((±)-23).

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Syntheses of α, β-Epoxy Silyl Ketones (1989)

Scheller, Markus E. ; Bernd Schweizer, W. ; Frei, Bruno

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 264-270

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Keywords: Chemistry ; Organic Chemistry

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Notes: The synthesis of the α, β-epoxy-acylsilanes 1 and 2 starting from the allylic silyl alcohols (E)- and (Z)-3, respectively, by epoxidation with t-BuOOH/VO(acac)2 followed by oxidation with Collins reagent (CrO3/pyridine) in up to 70% overall yields, is described. The acid-catalyzed rearrangement of the epoxy-silyl alcohols 4A + B und 5A + B led to the novel unstable diastereoisomeric α-silyl-β-hydroxy-aldehydes 9 and 10, respectively. The structure of 10 was established by X-ray crystal-structure analysis of the corresponding alcohol 11.

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Spectroscopic Studies of Cyclometallated Pd(II) and Pt(II) Complexes: Optical absorption and emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (1989)

Schwarz, Raimund ; Gliemann, Günter ; Chassot, Laurent ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 224-236

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The polarized optical absorption and emission (spectra, decay times) of single crystals of [Pd(thpy)2] and [Pt(thpy)2] (thpy ≡ C(3′)-deprotonated form of 2-(2-thienyl)pyridine) at temperatures 1.9 K ≤ T ≤ 80 K are reported. The emission of [Pt(thpy)2] can be influenced strongly by applied magnetic fields (0 ≤ H ≤ 6 T). Depending on the central ions Pd and Pt, the lowest excited electronic states of the single complexes are ligand-centered (LC) states and metal-to-ligand charge transfer (MLCT) states, respectively. This difference leads to distinctly dissimilar properties of the emission of both compounds. The experimental data show that the emission of single crystals of [Pd(thpy)2] and [Pt(thpy)2] at T ≤ 30 K originates from several types of traps (defect states of symmetry 3B2-stabilized below the exciton band) with LC and MLCT character, respectively. In the Pt compound, the 3B2 is split by spin-orbit coupling into three states. The states B1′ and A2′, which determine the emission properties, are separated by Δv ∼ 13 cm-1. Both states can mix under the influence of an applied magnetic field yielding an increase of the emission intensity by a factor of ∼ 1.5 at H = 6 T.

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Total Synthesis of L-Allose, L-Talose, and derivatives.Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives (‘naked sugars’ [2]) as synthetic intermediates, Part IV. Part III, see [1]. (1989)

Auberson, Yves ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 278-286

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Keywords: Chemistry ; Organic Chemistry

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Notes: (1S, 4R, 5S, 6S)-5-exo, 6-exo-(Isopropylidenedioxy)-7-oxabicyclo[2.2.1]heptan-2-one ((-)-1) was transformed with high stereoselectivity to L-allose. Similarly, enantiomer (+)-1 was transformed into L-talose. The ketones (+)-1 and (-)-1 were derived from furan and 1-cyanovinyl (1S)-camphanate and 1-cyanovinyl (1R)-camphanate, respectively.

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Highly Stereoselective Total Syntheses of 2,5-Anhydro-4-deoxy-D-ribo-hexonic Acid and of (1S)-1-C-(6-amino-7H-purin-8-yl)-1,4-anhydro-3-deoxy-D-erythro-pentitol (= cordycepin C)Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives (‘naked sugars’) as synthetic intermediates, Part V. Part III: [1]. Part IV: [2].Part of the planned Ph. D. thesis of F. G., University of Lausanne.Dedicated to Prof. Hans Dahn on the occasion of his 70th birthday (1989)

Gasparini, Fabrizio ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 271-277

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Notes: Highly regio- and stereoselective monohydroxylation of the C=C bond of (+)-7-oxabicyclo[2.2.1]hept-5-en-2-one (8) was achieved via LiAlH4 reduction of the corresponding 5,6-exo-epoxy dimethyl acetal 9. The reaction gave exclusively (-)-(1R, 2R, 4S)-6,6-dimethoxy-7-oxabicyclo[2.2.1]heptan-2-exo-ol (10) which was transformed into 2,5-anhydro-3-O-benzyl-4-deoxy-D-ribo-hexonic acid (15) and 2,5-anhydro-4-deoxy-D-ribo-hexonic acid (6) via ozonolysis of (-)-(1R, 4S, 6R)-6-exo-benzyloxy-2-{[(tert-butyl)dimethylsilyl]oxy}-7-oxabicyclo[2.2.1]hept-2-ene (14). Cordycepin C (5) was derived from 6 and 4,5,6-triaminopyrimidine using CsF/DMF to generate the adenine heterocycle.

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Die absolute Konfiguration der Iridale und Cycloiridale unterschiedlicher HerkunftDr. G. Ohloff zum 65. Geburtstag mit den besten Wünschen gewidmet (1989)

Marner, Franz-Josef ; Jaenicke, Lothar

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 287-294

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The Absolute Configuration of Iridals and Cycloiridals of Different OriginNatural irones are known to occur in enantiomeric forms within Iris oils of different origin. They are formed by oxidative degradation of the cycloiridals (C31-triterpenoids) found in rhizomes of various Iris species. The absolute configuration of iridals from different varieties is determined by ozonolysis of the triterpenoids and comparison of their degradation products with authentic samples of known configuration. It is shown that the initial cyclization of squalene resulting in the formation of a monocyclic seco-ring-A iridal has the same stereo-chemical course throughout all Iris species studied. The subsequent cyclization of the homofarnesyl side chain of the iridals, however, produces cycloiridals with enantiomeric irone moieties within different subspecies of the sword lilies.

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Metal Complexes with Macrocyclic Ligands. Part XXVIII.Part XXVII: [1]. Structures and stabilities of the Cu2+ complexes with 1,4,7-triazacyclononane-1-acetic acid (1989)

Studer, Martin ; Riesen, Andreas ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 307-312

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Notes: The potentiometric study of the complexation of 1,4,7-triazacyclononane-l-acetic acid (1) with Cu2+ (I = 0.5 (KNO3), T = 25°) indicates the presence of the species [Cu(1)], [Cu(1)OH], [Cu(1)2], and [(Cu(1))2OH], the stability constants of which are determined. The two complexes [Cu(1)]ClO4 and [(Cu(1)2)OH]ClO4 were also characterized by X-ray structure analysis. In both cases, the Cu2+ ion is in a distorted square-pyramidal arrangement, penta-coordinated by the three N-atoms of the macrocycle, an O-atom of the carboxylate, and an additional O-atom either from a second carboxylate or from an OH-, acting as a bridge between two metal centres.

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URL: http://dx.doi.org/10.1002/hlca.19890720215

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Metal Complexes with Macrocyclic Ligands. Part XXIX.Part XXVIII: [1]. Structural and kinetic studies of two isomeric Cu2+ complexes with 1,4-dimethyl-8-[2-(2-pyridyl)ethyl]-1,4,8,11-tetraazacyclotetradecane (1989)

Tschudin, Daniel ; Riesen, Andreas ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 313-319

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The synthesis and complexation properties of 1,4-dimethyl-8-[2-(2-pyridyl)ethyl]-1,4,8,11-tetraazacyclotetra-decane (2) are described. This ligand forms with Cu2+ two complexes, one of which has been characterized by X-ray structure analysis. The structural, spectral, and kinetic studies indicate that the two Cu2+ complexes are isomers with the macrocycle in the trans-III and trans-I configuration. The rate of the interconversion of the trans-I isomer to the thermodynamically more stable trans-III species is proportional to [OH-]. A mechanism for this reaction is proposed.

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URL: http://dx.doi.org/10.1002/hlca.19890720216

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Stereochemical Criteria Providing Unambiguous Experimental Evidence for the intermediacy of ion/molecule complexes in the generation of enolates from gaseous alkoxides. Short communicationDedicated to Prof. Josef Seibl on the occasion of his 65th birthday (1989)

Sülzle, Detlev ; Schwarz, Helmut

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 320-322

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Notes: The epimeric alkoxides 6a and 6b, generated in the gas phase by deprotonation of the stereospecifically deuterated isoborneols 5a and 5b, undergo loss of H2 and HD in a 1:1 ratio. This result, ruling out a concerted one-step process, establishes the intermediacy of an ion/molecular complex (‘solvated’ hydride ion) in the course of formation of enolates from the alkoxide anions in the gas phase.

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Neue Dimethinmerocyanin-Farbstoffe mit der (Sulfobutyl)benzothiazol-Gruppe als Donor-Teilchromophor und deren Aggregationsverhalten in wässriger Lösung (1989)

Kussler, Manfred ; Balli, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 295-306

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Notes: Novel Dimethinemerocyanine Dyes with the (Sulfobutyl)benzothiazole Group as Donor Part of the Chromophor and their Aggregation Tendency in Aqueous SolutionA series of novel dimethinemerocyanine dyes with the (sulfobutyl)benzothiazole group as the donor part of the chromophor is synthesized in good yield and their aggregation tendency in H2O without addition of salt investigated. The merocyanine dye 2b only gives J-aggregation in H2O. The dyes 1a-f and 2a exhibit an intense, red-shifted absorption band due to J-aggregation in H2O in the presence of Me4NCl. In contrast, the dyes 1g and 2c-f show a slightly red-shifted absorption band. The degree of aggregation in H2O is investigated by ultracentrifugation of the representative 2e. Indeed, the slightly red-shifted absorption band in H2O is due to aggregation of ‘oligomers’ of the dye. Contrary to the aggregation of ‘polymers’ of dyes (J-aggregation), we suggest the term ‘K’ band for the slightly red-shifted absorption band. The hemicyanine dye 5 gives the same absorption band in MeOH and in MeOH/H2O 1:3. The dye 11 shows an absorption band in H2O that is probably blue-shifted because of negative solvatochromism. The merocyanine dye 13 gives H-aggregation in H2O.

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Models for Copper-Dioxygen Complexes: The chemistry of copper(II) with some planar tridentate nitrogen ligands (1989)

Piguet, Claude ; Bocquet, Bernard ; Müller, Edgar ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 323-337

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1), 2,6-bis(l-methylbenzimidazol-2-yl)pyridine (mbzimpy, 2) 2,6-bis(benzothiazol-2-yl) pyridine (bzthpy, 3), 2,6-bis(benzoxazol-2-yl)pyridine (bzoxpy, 4), and 2,2′, 6′, 2″-terpyridyl (terpy, 5) is reported. Electronic and EPR spectra are consistent with the complexes [CuL]2+ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand-field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper. Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl- and OH- (provided that the ligand has no acidic protons) for all ligands except terpy. The reaction between [Cu(mbzimpy)]2+ and imidazole has been studied by potentiometric titration in MeCN/H2O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25°), and also the formation of an imidazolate-bridged dinuclear species.

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URL: http://dx.doi.org/10.1002/hlca.19890720218

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Synthesis of (-)-Conduritol C (1L-Cyclohex-5-ene-1,2,3/4-tetrol)Enantiomerically pure 7-oxabicyclo[2.2.1]hept-5en-2-yl derivatives (‘naked sugars’ [1]) as synthetic intermediates, Part VI; Part V:[2]. (1989)

Le Drian, Claude ; Vieira, Eric ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 338-347

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Keywords: Chemistry ; Organic Chemistry

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Notes: (1R, 2R, 4R)-2-endo-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate ((-)-7) has been transformed into the all-cis-configurated 4L-4,5,6/0-trihydroxycyclohex-2-en-1-one derivatives (-)-12 and (-)-19. (-)-Conduritol C ((-)-3) was derived in a stereospecific manner from (-)-12.

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Diels-Alder-Reaktionen mit 3-Cyclopropylidenprop-1-enyl-ethyl-ether als 1,3-Dien (1989)

Kienzle, Frank ; Stadlwieser, Josef ; Mergelsherg, Ingrid

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 348-352

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Diels-Alder Reactions with 3-Cyclopropylideneprop-1-enyl Ethyl Ether as 1,3-DieneThe title compound undergoes readily Diels-Alder reactions with various dienophiles, especially with quinones. The resulting adducts constitute key intermediates in the synthesis of labdane diterpenoids.

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Synthese von (+)-Abscisinsäure (1989)

Soukup, Milan ; Lukáč, Teodor ; Lohri, Bruno ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 361-364

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Synthesis of (+)-Abscisic Acid.Starting from (4S)-4-hydroxy-2,6,6-trimethylcyclohex-2-enone (2), a short synthesis of the natural (+)-abscisic acid ((+)-1) has been accomplished.

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Ein neuer Zugang zu 2,6,6-Trimethylcyclohexa-2,4-dienon aus 4-Oxoisophoron (1989)

Soukup, Milan ; Lukáč, Teodor ; Zell, Reinhard ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 365-369

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Keywords: Chemistry ; Organic Chemistry

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Notes: A New Access to 2,6,6-Trimethylcyclohexa-2,4-dienone from 4-Oxoisophorone2,6,6-Trimethylcyclohexa-2,4-dienone (1), a versatile starting material for the preparation of some carotenoids and several natural products, was efficiently (73% yield) prepared from oxoisophorone 3. After conversion of 3 to the alcohol 4 or the acetate 5, H2O was eliminated (4→1) under acidic distillative conditions, whereas AcOH could be eliminated (5→l) under Pd(O) catalysis.

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Neue Zugänge zu einigen aromatischen Retinoiden (1989)

Soukup, Milan ; Broger, Emil ; Widmer, Erich

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 370-376

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Notes: New Approaches to Some Aromatic RetinoidsStarting from 2,3,5-trimethylphenol (2), two pathways to ethyl (all-E)-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethylnona-2,4,6,8-tetraenoate (1) and to some of its (Z)-isomers have been developed. The first one is based on a Pd(O)-catalyzed arylation of (Z)-3-methylpent-2-en-4-yn-l-ol (6) with 4-bromo-2,3,5-trimethylanisol (5). The acetylenic C15-alcohol 9 was transformed into the corresponding acetylenic phosphonium salt 10, which was catalytically hydrogenated to the olefinic Wittig salt. Wittig olefination led, then, to the (6Z, 8Z)- and (4Z, 6Z, 8Z)-isomers, 7 and 8, respectively. In a second approach, Friedel-Crafts reaction of 3-methylpent-l-en-4-yn-3-ol with the 2,3,5-trimethylanisol gave a C15-intermediate with a terminal C=C bond in the side chain. After deprotonation and reaction with a C5 aldehyd, the corresponding C20-intermediate could be isolated in high yield. Finally, further conversion led predominantly to the (all-E)-retinoid, accompanied by its (9Z)- and (13Z)-isomers.

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Synthesis of Gossypol AnaloguesDedicated to the memory of Professor Dr. Pierre Crabbé (1989)

Ognyanov, Vassil I. ; Petrov, Orlin S. ; Tiholov, Emil P. ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 353-360

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Two gossypol analogues 2a and 2b were synthesized for biological evaluation as male contraceptive agents. The naphthol 8c was prepared by analogy with a known procedure starling from 3-isopropylcatechol (3). (t-Bu)2O2-Mediated phenolic coupling of 8c furnished the binaphthol 9c which, after pyrane ring closure, deprotection. and selective bisformylation with SnCl4/Cl2CHOCH3, gave the target compound 2a. The corresponding tetrahydroxy analogue 2b was prepared in a similar way.

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Cyclometalated Compounds of Platinum(II) with two different C, N-aromatic ligands (1989)

Deuschel-Cornioley, Christine ; Lüönd, Rainer ; von Zelewsky, Alex

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 377-382

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Notes: A synthetic route leading to bis-heteroleptic cyclometalated complexes is described. The complexes [2-(2′-thienyl)pyridinato-N, C-3′]{2-[3′-(trimethylsilyl)2′-thienyl]pyridinato-N, C3′}platinum(II) ([Pt(thpy) (TMS-thpy)]; I) and (l-phenylpyrazolato-N2, C2′)[2-(2′-thienyl)pyridinato-N, C3′]platinum ([Pt(Phpz)(thpy)]; II) are characterized by UV/VIS, NMR, and mass spectroscopy. Thermal and photochemical oxidative addition reactions yield two out of the 10 possible pairs of enantiomers of octahedral Pt(IV) compounds.

Additional Material: 1 Ill.

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Masthead (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989)

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

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URL: http://dx.doi.org/10.1002/hlca.19890720301

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Mitteilungen (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 401-402

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

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URL: http://dx.doi.org/10.1002/hlca.19890720228

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The Radical Cations of Bicyclo[2.2.1]hepta-2,5-diene (8,9,10-Trinorborna-2,5-diene) and bicyclo[2.2.2]octa-2,5-diene (2,3-Dihydrobarrelene). An ESR and ENDOR studyPart 5 of ‘Applications of ENDOR Spectroscopy to Radical cations in Freon matrices’. Part-4: [1]. (1989)

Gerson, Fabian ; Qin, Xue-Zhi

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 383-390

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The radical cation of bicyclo[2-2.1]hepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1) in CF2ClCFCl2, and CF3CCl3 matrices and that of bicyclo[2.2.2]octa-2,5-diene (2,3-dihydrobarrelene; 2) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy. For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, methano-bridge, and bridgehead protons are -0.780 ±0.005, +0.304±0.002, and -0.049±0.002 mT, respectively. The hyperfine tensor for the methano-bridge protons is axial, Ax = +0.263 ± 0.002 and Ay = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = -0.594 ± 0.005, Ay= -0.913 ± 0.005, and Az = -0.834 ± 0.005 mT (x parallel to C—H- z parallel to 2pπ axis). For \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are -0.68 ± 0.01, +0.162 ± 0.005, and -0.108 ± 0.005 mT, respectively. The hyperfine data for \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document} fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(π), of the two bonding ethene π-MO's.

Additional Material: 5 Ill.

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The Allylic Oxidation of Geraniol Catalyzed by Cytochrome P-450Cath., Proceeding with retention of configurationPresented in part at the ‘22nd Reaction Mechanisms Conference’, Pittsburgh, 12.6-16.6.88, at the ‘6th International Conference on Biochemistry and Biophysics of Cytochrome P-450’, Vienna, 3.7.-8.7.88, and at the meeting on the ‘Biocatalytic synthesis of Organic Compounds’, Saratoga Springs, NY, 8.-12.8.88.Dedicated to Prof. D. Arigoni on the occasion of his 60th birthday (1989)

Fretz, Heinz ; Woggon, Wolf-Dietrich ; Voges, Rolf

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 391-400

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Keywords: Chemistry ; Organic Chemistry

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Notes: Incubation of the geraniols (R)-(8-2H1)[8-3H1]-1 and (S)-(8-2H1)[8-3H1]-1 with microsomal cytochrome P-450Cath. from the subtropical plant Catharanthus roseus (L.)G. DON resulted in the formation of the chiral 8-hydroxygeraniols (S)-(8-2H1)[8-3H1]-2 and (R)-(8-2H1)[8-3H1]-2. Their absolute configuration was assigned on the basis of the 1H-decoupled 3H-NMR Spectra of the corresponding dicamphanates (S)-(8-2H1)[8-3H1]-9 and (R)-(8-2H1)[8-3H1]-9, of which the configurations are established in relation to the synthetic reference samples. The results clearly indicate retention of configuration during the allylic oxidation of 1.

Additional Material: 2 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720227

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Elektrochemische Decarboxylierung von L.-Threonin- und Oligopeptid-Derivaten unter Bildung von N-Acyl-N, O-acetalen: Herstellung von Oligopeptiden mit Carboxamid-oder Phosphonat-C-TerminusTeilweise in einer Kurzmitteilung erwähnt (1989)

Seebach, Dieter ; Charczuk, Roland ; Gerber, Christian ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 401-425

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Description / Table of Contents: Electrochemical Decarboxylation of L-Threonine and Oligopeptide Derivatives with Formation of N-Acyl-N, O-acetals: Preparation of Oligopeptides with Amide or Phophonate C-TerminusDerivatives of α-amino acids with two stereogenic centers (cf. L-threonine) and of di-, tri-, and tetrapeptides are electrolyzed in MeOH or AcOH, with formation of N-acyl-N, O-acetals (1b-15b, 20b), in an anodic oxidative substitution of the COOH by an OR group. The amine ends of the oligopeptides may be benzyloxycarbonyl(Z)- or (tert-butoxy)carbonyl(Boc)-protected. With unprotected dipeptides, an electrolytic decarboxylative cyclization to imidazolidinones (18c, 19c) may also occur (in H2O/NH4OAc). The electrolyses are carried out in simple flasks with cooling jackets (‘undivided cell’), using constant current conditions and anodes of Pt or glassy C. The electrolyte is generated in situ by adding 10-20 mol-% of a tertiary amine. Mild acidic hydrolysis of electrolysis products thus obtained may lead to amino-acid amides or peptide amides (10c, 11c, 12c, 17c) with one amino acid less than the starting material. The N, O-acetals from L-threonine and the oligopeptides also react with organometallic nucleophiles such as Grignard compounds (→21-26, 29), with formation of products in which the original COOH group has been replaced by alkyl or allyl (sometimes even with moderate stereoselectivity). By treatment of the peptide-derived (open-chain) N, O-acetals with trialkyl or triaryl phosphites/TiCl4 the RO group is replaced by a phosphodiester group in a (non-diastereoselective) Michaelis-Arbuzov-type reaction (1d, 1e, 2d-9d, 5e). Thus, the two-step sequence of electrolysis and phosphonation converts an oligopeptide derivative to an analogue with a phosphonic-acid end group. The diastereoisomeric N-protected dimethyl and diethyl dipeptidephosphonates (also prepared from the corresponding diaryl esters by Ti(OR)4-mediated transesterification) could be separated by preparative HPLC (SiO2, Lichrosorb Si 60, 10 μm); the dextrorotatory isomers of 1d-3d were assigned L, D-, the laevoratory ones L, L-configuration by hydrolysis to and identification of the known amino and aminophosphonic acids. The results described demonstrate a new simple route leading, from a given oligopeptide, to pure peptide analogues of known configuration.

Notes: No abstract.

Additional Material: 2 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720302

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Acid-Catalyzed Cyclization Reactions of Substituted Acetylenic Ketones: A new Approach for the Synthesis of 3-Halofurans, Flavones, and StyrylchromonesPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988. (1989)

Obrecht, Daniel

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 447-456

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Notes: Acetylenic acetals of type I (Scheme 1) and acetylenic ketones of type III (Scheme 1), 37 and 38 (Scheme 7) are versatile synthetic precursors for the synthesis of various heterocycles by acid-catalyzed cyclization reactions. By this way, substituted 3-halofurans of type II and IV (Scheme 1) and flavones and styrylchromones (Scheme 7) can be synthesized in good-to-excellent yields. The high degree of regioselectivity in the synthesis of the 3-halofurans (Scheme 4) is the result of the regioselective β-addition of HX (X = Cl, Br, I) to the acetylenic aldehyde and acetylenic ketone moieties. A possible mechanism is depicted in Scheme 5. Since 3-halofurans can easily be metalated and substituted, this approach constitutes a new synthesis of highly substituted furans.

Additional Material: 3 Tab.

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Stoffwechselprodukte von Mikroorganismen. 253. Mitteilung252, Mitteilung. Hormaomycin, ein neues Peptid-lacton mit morphogener Aktivität auf Streptomyceten (1989)

Andres, Nikolaus ; Wolf, Heinz ; Zähner, Hans ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 426-437

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Description / Table of Contents: Hormaomycin, a Novel Peptide Lactone with Morphogenetic Activity on StreptomycesA culture identified as Streptomyces griseoflavus (strain W-384) has been found to produce a novel peptide-lactone antibiotic designated hormaomycin (6). The empirical molecular formula of the compound is established to be C55H69ClN10O14. The constituent amino acids of the antibiotic are suggested to be allothreonine (1; 1), isoleucine (2; 1), 3-methyl-phenylalanine (3; 2), and, for the first time identified from a natural source, 4-[(Z)-prop-1-enyl]-proline (4; 1) and 3-(2-nitrocyclopropyl)-alanine (5; 2). The amino acids were delivered by acidic hydrolysis and assigned by high-resolution- GC/MS analysis (after transformation to derivatives) in combination with extended 2D-NMR experiments of the antibiotic itself. From the latter, it became plausible that the N-terminus of the peptide chain is acylated by a Cl-containing derivative of 1H-pyrrol-2-carboxylic acid. Hormaomycin is active against some Gram-positive bacteria. In addition, the antibiotic exhibits potent aerial mycelium-inducing activity and effects the production of antibiotics.

Notes: No abstract.

Additional Material: 4 Ill.

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Novel Trinor-eremophilanes (Dendryphiellin B, C, and D), Eremophilanes (Dendryphiellin E, F, and G), and Branched C9-Carboxylic Acids (Dendryphiellic Acid A and B) from the Marine Deuteromycete Dendryphiella salina (SUTHERLAND) PUGHet NICOT (1989)

Guerriero, Antonio ; D'Ambrosio, Michele ; Cuomo, Vincenzo ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 438-446

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Notes: Further investigation of global extracts from cultures of the marine deuteromycete Dendryphiella salina leads to the isolation of three novel trinor-eremophilanes esterified by branched C9-carboxylic acids, dendryphiellin B(= (+)-(1R*,2S*,7R*,8aR*)-1,2,6,7,8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*, 2E, 4E)-6-hydroxy-6-methylocta-2,4-dienoate; (+)-2), dendryphiellin C (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7,8,8a-hexa-hydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6S, 2E, 4E)-6-methylocta-2,4-dienoate; (+)-3)), and dendryphiellin D (=(+)-(1R*, 2S*, 7R*, 8aR*)-1,2,6,7(8,8a-hexahydro-7-hydroxy-1,8a-dimethyl-6-oxonaphthalen-2-yl (6R*,2E,4E)-6-(hydroxymethyl)octa-2,4-dienoate; (+)-4). An intact eremophilane, dendryphiellin E (5), and its ethanolysis product dendryphiellin F whose absolute configuration is represented by structural formula (+)-6 are also isolated from the above extracts. Dendryphiellin E exists as an open form 5a in equilibrium with a closed form 5b. A similar equilibrium exists between the open form 8a and the closed form 8b of a non-esterified eremophilane, dendryphiellin G (8), which is isolated too from the above extracts and proves structurally related to the cyclic portion of 5. Finally, the free, branched C9-carboxylic acids dendryphiellic acid A ((+)-9) and B ((+)-10) which correspond to side chains of the above esterified terpenes are also isolated from the above extracts.

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Eine neue Azepinring-Synthese (1989)

Kvita, Vratislav ; Sauter, Hanspeter ; Rihs, Grety

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 457-463

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Description / Table of Contents: A New Azepine-Ring SynthesisA new one-step synthesis of an azepine ring is described. The 2H-pyran-2-one ring of methyl cumalate (8) or cumalaldehyde (2) upon reaction with an 1-aminoacryl derivative, e.g. 1 or 6, is opened with subsequent decarboxylation to give a 1-aminobutadiene derivative that undergoes an electrocyclic ring closure to the azepine ring (Schemes 1 and 2).

Notes: No abstract.

Additional Material: 1 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720306

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New Hyperforin Derivatives from Hypericum revolutum VAHL with Growth-Inhibitory Activity against a Human Colon Carcinoma Cell LinePresented in part at the 36th Annual Congress on Medicinal Plant Research, Freiburg im Breisgau, FRG, 12-16th September, 1988, and at the Meeting of the Swiss Chemical Society, Bern, 21st October, 1988. (1989)

Decosterd, Laurent A. ; Stoeckli-Evans, Helen ; Chapuis, Jean-Charles ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 464-471

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Notes: The crude petroleum-ether extract of the root bark of Hypericum revolutum VAHL (Guttiferae) exhibited in vitro growth-inhibitory activity against the Co-115 human colon carcinoma cell line. Activity-guided fractionation of this extract resulted in the isolation of two new hyperforin derivatives 1 and 2. The structure of 1 (hyperevolutin A) was established by X-ray analysis as the 4-hydroxy-8-exo-methyl-5,7-exo-bis(3-methylbut-2-enyl)-1-(2-methyl-1-oxopropyl)-8-endo-(4-methylpent-3-enyl)bicyclo[3.3.1]non-3-ene-2,9-dione. The structure of the homologue 2 was deduced by comparison of its UV and 1H- and 13C-NMR spectra with those of 1.

Additional Material: 2 Ill.

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Asymmetric Diels-Alder Reaction of 1-Methoxybuta-1,3-diene with (2R)-N-Glyoxyloylbornane-10,2-sultam (1989)

Bauer, Tomasz ; Chapuis, Christian ; Kozak, Janusz ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 482-486

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Notes: Starting from sultam 1, the chiral dienophile (2R)-N-glyoxyloylbornane-10,2-sultam (4) was readily prepared. Non-catalyzed atmospheric- and high-pressure as well as [Eu(fod)3]-promoted [4 + 2] cycloadditions of 1-methoxy-buta-1,3-diene (5) to chiral dienophile 4, leading with high asymmetric induction to 6-methoxy-3,6-dihydro-2H-pyran-2-yl derivatives 6-9, are described. The extent and direction of asymmetric induction in these reactions were established by 1H-NMR analysis and chemical correlation, respectively. Stereochemical models for both non-catalyzed and [Eu(fod)3]-promoted reactions are proposed.

Additional Material: 1 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19890720310

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5,10:8,9-Disecosteroids (= Steroklastanes): A new type of modified steroidsDr. Günther Ohloff on the occasion of his 65th birthday (1989)

Lorenc, Ljubrinka ; Bondarenko, Lidija ; Pavlović, Vlada ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 608-623

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Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Thermolysis of steroidal 5α, 8α- peroxides of type 3a-d generates as major products the corresponding diseco compounds containing a 14-membered ring instead of the standard A-B-C-ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β-unsaturated ketones of type 4, formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer-Villiger oxidation to give, as final products, the 15-membered cyclic epoxyenol lactones of type 20 and 21. The structures of the various products were determined by 1H- and 13C-NMR spectroscopy. The conformations of the 14- and 15-membered rings were established by X-ray structure analyses of 7 and 21a. A reaction mechanism for the above transformations is discussed.

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Thermal and Photochemical Reactions of 1,2-Annelated Barrelenes and Hydrobarrelenes in the presence of transition-metal carbonyls (1989)

Trifonov, Latchezar S. ; Orahovats, Alexander S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 648-652

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The [Co2(CO)8]-mediated retro-Diels-Alder reaction of the annelated barrelenes 1 afforded the 1H-indol-2(3H)-one derivatives 3 (Scheme 1), while the hydrobarrelene 4a, under the same conditions, was converted to the anilide 6 (Scheme 2); 4b remained unaffected. The direct irradiation of 1 led to the annelated cyclooctatetraenes 7 (Scheme 3). On irradiation in the presence of excess of [Fe(CO)5], 1a, 1b, and 4a gave the tricarbonyliron complexes 8, 9, and 11, respectively (Schemes 3 and 4); under these conditions, 4b was inert.

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A Simple and Efficient Method for the Preparation of Binaltrorphimine and Derivatives and determination of their K opioid antagonist selectivity (1989)

Schmidhammer, Helmut ; Smith, Colin F. C.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 675-677

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The bimorphinans 1 (binaltrorphimine), 3, and 7 have been prepared by treatment of the parent morphinan-6-ones naltrexone (5), naloxone (4), and dihydrocodeinone (6), respectively, with N-methylhydrazine sulfate in AcOH at room temperature. Compound 3 showed opioid antagonist potency and selectivity for K receptors which were somewhat lower in comparison to 1.

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URL: http://dx.doi.org/10.1002/hlca.19890720408

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Synthèse d'une sonde biotinylée à bras clivable allongé pour l'isolement des récepteurs de l'angiotensine II (1989)

Seyer, René ; Aumelas, André ; Marie, Jacky ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 678-689

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Synthesis of a Biotinylated Probe with an Extended Cleavable Arm for Angiotensin II Receptors PurificationWe have synthesized a new biotinylated probe for angiotensin II receptors studies: biotinyl-NH(CH2)2—SS—(CH2)2—CO-Gly-∊ Ahx-[Ala1, Phe(4N3)8]angiotensin II (5). This molecule can be photoactivated through an arylazido group. 1H-NMR studies suggest that it adopts an extended conformation which should allow a simultaneous recognition of both streptavidin and hormone receptor. It has a good affinity for receptors (Kd = 1 nM) and hence is a promising tool in their detection (autoradiography, gold-, ferritin-, enzyme-, or fluorescent streptavidin derivatives) and separation (cell sorting, affinity chromatography). It can be monoiodinated (°6) at its tyrosine residue without a significant loss of affinity. Its extended cleavable arm allows an easy recovery of the ‘probe-receptor’ complex from streptavidin. An HPLC monitoring of the synthesis is described, particularly of the segment coupling 1 + 2 in presence of (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP). This method can be used as well for synthesis of the D-Phe8 derivative that has antagonist properties.

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Synthesis of 11-Oxaestrogens via Dye-Sensitized Photo-oxygenation of a 9,11-Didehydroestrone Derivative (1989)

Planas, Antoni ; Sala, Nuria ; Bonet, Juan-Julio

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 725-730

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The 3-methoxy-1 1-oxaestrone (13) has been synthetized from estrone (3) following an approach that involves the ring-C fragmentation of the estrogenic skeleton by dye-sensitized photo-oxygenation of the properly C(17)-protected 9,11-didehydroestrone derivative 6 as the key step. The C(13)-side-chain degradation of the 9-oxo-9,11-seco-aldehyde 7 followed by reduction to the 9β, 12-diol 10 and further cyclization yields the 11-oxaestrogenic skeleton. By this procedure, 13 is obtained in 9 steps from 3 with a non-optimized overall yield of ca. 15%.

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Photo-oxygenation of Styrenic Estrogens: Product characterization and kinetics of the dye-sensitized photo-oxygenation of 9,11-didehydroestrone derivativesPhotochemical Reactions, Part 23. Part 22: [1] (1989)

Planas, Antoni ; Lupon, Pilar ; Cascallo, Montse ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 715-724

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The dye-sensitized photo-oxygenation of 3-hydroxyestra-1,3,5(10), 9(11)-tetraen-17-one (8) gives a complex mixture from which only the 1,4-endo-peroxide 10 can be isolated in low yield. In contrast, the 3-methoxy derivative 9 yields the C-seco-aldehyde 11 as a major product, suggesting that 1,2-dioxetane is a primary photo-oxygenation intermediate. As the electron-donating character of the substituent at C(3) decreases in the sequence 12 (R = PhCO), 13 (R = Ac), and 14 (R = Ts), the rate constant in substrate disappearance becomes drastically smaller as compared with 8 and 9, and no photoproducts are detected. The results are rationalized by means of electronic and conformational factors.

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Synthèse énantiospécifique des acides (+)-(2R)- et (-)-(2S)-éthyl-6-dihydro-3,4-méthyl-2-oxo-4-2H pyranecarboxylique-5 (1989)

Deschenaux, Pierre-François ; Kallimopoulos, Thomas ; Stoeckli-Evans, Helen ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 731-737

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Enantiospecific Synthesis of (+)-(2R)- and (-)-(2S)-6-Ethyl-3,4-dihydro-2-methyl-4-oxo-2H-pyran-5-carboxylic AcidThe two enantiomers (-)-(2S)- and (+)-(2R)-6-ethyl-3,4-dihydro-2-methyl-4-oxo-2H-pyran-5-carboxylic acid ((S)- and (R)-7) have been synthesized from (+)-(3S) and (-)-(3R)-3-hydroxybutanoates, respectively (Scheme 1). By reduction and decarboxylation, the tetrahydro-2H-pyranols (2R, 4R, 6S)- and (2S, 4S, 6R)-13, respectively, were obtained with an enantiomeric excess of ≥ 93%.

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Pteridines. Part XLIPart XL, see[1]. Synthesis and properties of 6,7,8-trimethyl-4-thiolumazine (1989)

Hübsch, Walter ; Pfleiderer, Wolfgang

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 738-743

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The first representative of the 8-substituted 4-thiolumazine series has been synthesized. In a sequence of reactions, 4,6-dichloropyrimidin-2-(1H)-one (1) is first converted into 4-chloro-6-(methylamino)pyrimidin-2(1H)-one (6), then the Cl-atom displaced by the thioxo group (→7) followed by a coupling reaction with 4-chlorophenyldiazonium chloride to introduce the necessary N-function into the 5-position (→ 9; Scheme 1). Reduction of the p-chlorophenylazo group leads to the 6-(methlyamino)-4-thiouracil-5-amine (10) which on condensation with diacetyl gives 6,7,8-trimethyl-4-thiolumazine (8). The physical properties of 8 are compared with the 2-thio analog and 6,7,8-trimethyllumazine indicating that 8 possesses the highest acidity and the longest UV absorption.

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Studies on the Biosynthesis of Spirostaphylotrichin A (1989)

Sandmeier, Peter ; Tamm, Christoph

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 774-783

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Incorporation of 14C-labelled acetate and amino acids as well as of [1-13C]-, [2-13C]-, and [1,2-13C2] acetate, L-[methyl13C] methionine, [2,3-13C2] succinate, and L-[2,3-13C2] aspartate into spirostaphylotrichin A (1) by Staphylotrichum coccosporum demonstrates that the building blocks of 1 are 5 units of acetate/malonate, 1 unit of methionine, and a C4-dicarboxylic acid. The latter is most likely aspartate and derived from the citric-acid cycle. Using [2-13C, 2-2H3] acetate as a precursor, the starter unit of the polyketide chain was identified.

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URL: http://dx.doi.org/10.1002/hlca.19890720418

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New Spirostaphylotrichins from Staphylotrichum coccosporum (1989)

Sandmeier, Peter ; Tamm, Christoph

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 784-792

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The isolation and structure elucidation of the new spirostaphylotrichins B (2), C and D (3/4), F (5), Q (6), and R (7) are described. Compounds 2 and 3 are artefacts formed during the isolation of the metabolites from the cultures. The absolute configuration of spirostaphylotrichin A (1) has been determined by CD spectroscopy.

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URL: http://dx.doi.org/10.1002/hlca.19890720419

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Diazotisation Mechanism of Heteroaromatic Amines. Diazotisation of 2-aminothiazole as an equilibrium (1989)

Diener, Heinz ; Güleç, Bilge ; Skrabal, Peter ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 800-805

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The rate of diazotization of 2-aminothiazole was measured in 65 to 75% (w/w) aqueous H2SO4. The kinetic solvent isotope effect of the diazotization in 72% D2SO4/D2O was determined (kH/kD = 5.8 ± 0.2). These data are consistent with a mechanism in which the 2-aminothiazole, protonated at the ring N-atom, but not at the NH2 group, is attacked by the NO+ ion. The reaction does not go to completion, but to an equilibrium. The equilibrium concentration of the diazonium ion was determined in 30,50,70, and 90% (w/w) H2SO4 at three initial concentration of reagents (0.001,0.01, and 0.1m). The final concentrations of the reagents and the diazonium ion are consistent with a reversible process. This is the first diazotization for which quantitative evidence for equilibration has been found. In the very large range of acidities used (Ho = -1.73 to -9.01), it was not possible to calculate meaningful equilibrium constants that are independent of the acidity.

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URL: http://dx.doi.org/10.1002/hlca.19890720421

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Struktur/wirkung-Beziehungen bei Geruchsstoffen mit dem Bicyclo[2.2.2.]octan-GerüstHerrn Dr. Günther Ohloff mit den besten Wünschen zum 65. Geburtstag gewidmetAuszugsweise vorgetragen an ‘The Conference on Terpene Chemistry’, 25.4.1986, Grasse, und am ‘19th International Symposium on Essential Oils and Other Substrates’, 9.19.1988, Greinfensee/Dübendorf, Schweiz. (1989)

Spreitzer, Helmut ; Buchbauer, Gerhard ; Reisinger, Sigrid

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 806-810

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Structure-Activity Relationships of Odorants with a Bicyclo[2.2.2]octane SystemThe synthesis of the olfactory interesting homonojigikualcohol 2 and of its epimer 10 leads to the keto alcohols 6a, b and 7a, b as intermediates. The latter have OH and C=O groups (an AH/B system) fixed at the rigid bicyclic nucleus at different distances (2.8 and 4.7 Å) and confirm Ohloff's rule for odoriferous properties which is based on this distance.

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Solubilization of Peptides in Non-polar Organic Solvents by the Addition of Inorganic Salts: Facts and ImplicationsDedicated to Prof. Gerhard Schröder on the occasion of his 60th birthday (1989)

Seebach, Dieter ; Thaler, Adrian ; Beck, Albert K.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 857-867

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The solubility of open-chain peptide derivatives (12 examples) in non-polar, ether-type organic solvents may be greatly increased by addition of salts (LiCl, LiBr, LiI, LiBF4, LiClO4, NaI, MgBr2 CaBr2, ZnCl2) or of titanates (Ti(OEt)4, Ti(OCHMe2)4). Examples are reported (Tables 2-6) in which this solubilizing effect leads to peptide concentrations more than one-hundred-fold those in the absence of salt (cf, Boc—Ala—Gly—Gly—Gly—OH in THF from 2g·1-1 to ≥ 300 g·1-1 with 6 equiv. of LiCl), 1H-NMR Spectra of one of these solutions are reported (Fig. 1). There are no indications for epimerizations of stereogenic centres on the peptide backbone. Possible applications of these solutions in peptide chemistry are discussed.

Additional Material: 2 Ill.

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Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]ironPart of the planned Ph. D. thesis of Edia Bonfantini, Ecole Polytechnique Fédérale de Lausanne. (1989)

Bonlantini, Edia ; Vogel, Pierre ; Pinkerton, Alan A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 906-916

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Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene-l-methanol (7) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe2(CO)9] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene (8) led to the formation of a 1.7:1 mixture of ‘trans’ (19, 21, 22) vs. ‘cis’ (20, 23, 24) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron (25) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron (26). The structures of products 19 and of its exo (21) and endo (22) [Fe(CO)3(1,3-diene)]complexes) and 20 (and of its exo (23) and endo (24) (Fe(CO)3(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron (21). In the latter, the Fe(CO)3(1,3-diene) moiety deviates significantly from the usual local Cs symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η3-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).

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Synthesis of Chiral 12-Phenyl(2H)dodecanoic Acids: Useful metabolic probes for the biosynthesis of 1-alkenes from fatty acids (1989)

Görgen, Günther ; Boland, Wilhelm ; Preiss, Ute ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 917-928

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The synthesis of chiral 12-phenyi(2H)dodecanoic acids as metabolic probes for the evaluation of the stereo-chemical course of the biosynthesis of 1-alkerses from fatty acids in plants and insects is described. The diastereoisomeric (2R, 3R)- or (2S, 3S)-12-phenyl(2,3-2H2)dodecanoic acids 11 are obtained in high chemical and optical yield (〉97% e.e.) from the readily available (E)-12-phenyl(2,3-2H2)dodec-2-enoic acid (10) or (E)-12-phenyldodec-2-enoic acid (10a) by microbial reduction with wet packed cells of Clostridium tyrobutyricum in either 2H2O or H2O buffer. (2R)- and (2S)-12-phenyl(2-2H)dodecanoic acids 9 (〉97% e.e.) are accessible from the allylic alcohol 6 via Sharpless epoxidation with (+)-L- or (-)-D-diethyl tartrate, Synthetic routes to the (E)- and (Z)-11-phenyl(1-2H) undec-1-enes 16 and 16a as reference compounds are also included.

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URL: http://dx.doi.org/10.1002/hlca.19890720507

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Photochemical Reactions 150th Communication149th Communication: [1]. Wavelength Dependence of the Photochemistry of 7-Methyl-β-ionone (1989)

Mathies, Peter ; Nishio, Takehiko ; Frei, Bruno ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 933-942

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The wavelength dependence of the photolysis of 7-methyl-β-ionone ((E)-1) was investigated. Irradiation of (E)-1 with light of λ 〉 347 nm leads primarily to (E/Z)-isomerization followed by transformation to the tricyclic enol ether 3 as the only secondary photoproduct. On photolysis of (E)-1 with light of shorter wavelength (λ 〉 280 nm or λ = 254 nm), however, a series of other products was formed (via a) photocyclization of the dienone chromophore (→ 5), (b) photo-enolization (→8), and (c) a 1,5-sigmatropic H-shift (→ (E/Z)-7). For the structure elucidation of the new products, 7-[13C]methyl-β-ionone ((E)-[7-methyl-13C]-1) was prepared and irradiated furnishing the corresponding 13C-labelled photoproducts.

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URL: http://dx.doi.org/10.1002/hlca.19890720509

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Catechol-O-methyltransferase-Inhibiting Pyrocatechol Derivatives: Synthesis and Structure-Activity Studies (1989)

Borgulya, Janos ; Bruderer, Hans ; Bernauer, Karl ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 952-968

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: 3-Nitro- and 3-cyanopyrocatechols bearing electron-withdrawing substituents at C(5) have been found to inhibit the enzyme catechol-O-methyltransferase. Structure-activity studies are discussed on the basis of the pharmocological data of 50 compounds (cf, Chapt. 4, Tables 1-7). Some 3-nitro-5-aroylpyrocatechols (Type A2, Table 1) fulfil the requirements for a clinical candidate, being orally active, specific, reversible, and relatively short-acting. The chemical work involved is illustrated by describing a choice of exemplary syntheses, dealing with compounds 9, 11, 14, 18, 22, 24, 25, 35, 41, and 42 (Chapt. 5, Schemes 1-10).

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URL: http://dx.doi.org/10.1002/hlca.19890720511

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Glycosylidene Carbenes a new approach to glycoside synthesis. Part 1. Preparation of glycosylidene-derived diaziridines and diazirinesPresented at the ‘197th ACS National Meeting’, Dallas, Texas, 9th-14th April 1989, Abstr. Carb 9. (1989)

Briner, Karin ; Vasella, Andrea

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1371-1382

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A new approach towards the synthesis of glycosides based upon a (formal) insertion of glycosylidene carbenes into O—H bonds is presented. The synthesis and characterization of the glycosylidene-derived diazirines 25-28, precursors of glycosylidene carbenes, are described. The diazirines were prepared by the rapid, high-yielding oxidation of the diaziridines 20 and 22-24 with I2/Et3N. The diaziridines, the first examples of C- alkoxy-diaziridines, were formed in high yields by the reaction of the [(glycosylidene)-amino]methanesulfonates 14 and 17-19 with a saturated solution of NH3 in MeOH. The diazirines are highly reactive compounds, losing N2 at room temperature or below. The reaction of the gluco-configurated diazirine 25 with i-PrOH yielding a mixture of the α- and β-D-glucosides 29 and 30 illustrates the potential of glycosylidene-derived diazirines as a new type of glycosyl donors.

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URL: http://dx.doi.org/10.1002/hlca.19890720626

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An Electrochemical Variant in the Syntheses of Exaltone® and muscone: Anodic fragmentation of α, β-unsaturated tosylhydrazonesDedicated to Dr. Günther Ohloff on the occasion of his 65th birthday (1989)

Limacher, Liviana L. ; D. Delay, François ; Bédert, Nicole ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1383-1389

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Ring enlargement of bicyclo[10.3.0]pentadec-1(12)-en-13-one p-toluenesulfonylhydrazone into cyclopentadec-4-yn-l-one was accomplished under mild and controlled anodic oxidation conditions. The mechanism of this fragmentation is reconsidered.

Additional Material: 2 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720627

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94

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Structure-Activity Relationship in Ambergris-Type Woody Odorants possessing a hydronaphthalene skeletonDedicated to Dr. G. Ohloff on the occasion of his 65th birthday (1989)

Vial, Christian ; Thommen, Walter ; Näf, Ferdinand

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1390-1399

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A series of methyl hydronaphthyl alcohols, formates, acetates, and ketones were prepared and their odour properties evaluated. Minor structural changes, even opposite to the osmophoric group, were found to have major effects on the odour. 13C—NMR shift assignments of the hydronaphthyl derivatives are presented.

Additional Material: 2 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720628

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Maurer, Bruno ; Hauser, Arnold ; Froidevaux, Jean-Claude

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1400-1415

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Twenty irone-related compounds 1-20 containing from 10 to 16 C-atoms have been identified for the first time in commercial Iris oil of Moroccan origin (Iris germanica L.). Most of the structures and the absolute configurations of natural 6, 16, and 17 are corroborated by partial synthesis. The organoleptic properties of some of the new constituents are discussed.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720629

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96

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Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study (1989)

Gerson, Fabian ; Huber, Walter ; Wellauer, Thomas

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1428-1434

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: ESR and ENDOR studies have been carried out on the radical cations obtained consecutively by reaction of trans-10b, 10c-dimethyl-10b, 10c-dihydropyrene (4) with AlCl3 in CH2C12. The primarily formed \documentclass{article}\pagestyle{empty}\begin{document}${\bf 4}^{+ \atop \dot{}}$\end{document} rearranges at 253 K to the radical cation(s) of 1,6- (5a) and/or 1,8-dimethylpyrene (5b). At 323 K, the spectra of \documentclass{article}\pagestyle{empty}\begin{document}${\bf 5a}^{+ \atop \dot{}}$\end{document}/\documentclass{article}\pagestyle{empty}\begin{document}${\bf 5b}^{+ \atop \dot{}}$\end{document} are replaced by that of the highly persistent radical cation of 1,3,6,8-tetramethylpyrene (6). Surprisingly, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 6}^{+ \atop \dot{}}$\end{document} is also the only observable paramagnetic product resulting from a treatment of 4,5,7,8- (1), 4,7,13,16- (2), and 4,5,12,13-tetramethyl[2.2]paracyclophane (3) with AlCl3 in CH2Cl2 at 353 K. The structures of the intermediates in the rearrangement [\documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 3}^{+ \atop \dot{}}$\end{document}] → \documentclass{article}\pagestyle{empty}\begin{document}${\bf 6}^{+ \atop \dot{}}$\end{document} are discussed.

Additional Material: 2 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720631

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[4 + 2]-Cycloadditionen von α, β- ungesättigten hydrazonen. Teil3Teil 2: [1]. Isothiazolo[4,5-b]pyridin-3(2H)-on-1,1-dioxide (= 4-azasaccharine) (1989)

Waldner, Adrian

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1435-1443

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: [4 + 2] Cycloaddition of α, β-Unsaturated Hydrazones: Isothlazolo[4,5-b]pyridin-3(2H)-on 1,1-Dioxides (= 4-Azasaccharine Derivatives)The [4 + 2] cycloaddition of α, β -unsaturated hydrazones of type 1 (1-azabuta-1,3-dienes) with isothiazol-3(2H)-on 1,1-dioxide derivatives 10 affords, depending on the solvent used, picolinamides 15 or 17, 4,7-dihydro-4-azasaccharine 14 or 4-azasaccharine derivatives 16 (Scheme 4). The course of the reaction is mainly influenced by the substituent R of the dienophile 10.

Additional Material: 1 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720702

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Bildung von 5,6-Dihydro-1,3(4H)-thiazin-4-carbonsäure-estern aus 4-Allyl-1,3-thiazol-5(4H)-onen (1989)

Jenny, Christjohannes ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1639-1646

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Formation of Methyl 5,6-Dihydro-l, 3(4H)-thiazine-4-carboxyiates from 4-Allyl-l, 3-thiazol-5(4H)-ones.The reaction of N-[1-(N, N-dimethylthiocarbamoyl)-1-methyl-3-butenyl]benzamid (1) with HCl or TsOH in MeCN or toluene yields a mixture of 4-allyl-4-methyl-2-phenyl-1,3-thiazol-5(4H)-one (5a) and allyl 4-methyl-2-phenyl-1,3-thiazol-2-yl sulfide (11; Scheme 3). Most probably, the corresponding 1,3-oxazol-5(4H)-thiones B are intermediates in this reaction. With HCl in MeOH, 1 is transformed into methyl 5,6-dihydro-4,6-dimethyl-2-phenyl-1,3(4H)-thiazine-4-carboxylate (12a). The same product 12a is formed on treatment of the 1,3-thiazol-5(4H)-one 5a with HCl in MeOH (Scheme 4). It is shown that the latter reaction type is common for 4-allyl-substituted 1,3-thiazol-5(4H)-ones.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720724

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99

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Nucleotides. Part XXXIPart XXX: [1].. Modified Oligomeric 2′-5′ A Analogues: Synthesis of 2′-5′ oligonucleotides with 9-(3′-azido-3′-deoxy-β-D-xylofuranosyl)adenine and 9-(3′-amino-3′-deoxy-β-D-xylofuranosyl)adenine as modified nucleosides (1989)

Herdewijn, Piet ; Charubala, Ramamurthy ; Pfleiderer, Wolfgang

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1729-1738

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A series of new 2′-5′ oligonucleotides carrying the 9-(3′-azido-3′deoxy-β-D-xylofuranosyl)adenine moiety as a building block has been synthesized via the phosphotriester method. The use of the 2-(4-nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) blocking groups for phosphate, amino, and hydroxy protection guaranteed straightforward syntheses in high yields and easy deblocking lo form the 2′-5′ trimers 21, 22, and 25 and the tetramer 23. Catalytic reduction of the azido groups in [9-(3′-azido-3′-deoxy-β-D-xylofuranosyl)adenine]2′-yl-[2′-(Op-ammonio)→ 5′]-[9-(3′-azido-3′-deoxy-β-D-xylofuranosyl)adenin]-2′-yl-[2′-(Op-ammonio)→ 5′]-9-(3′-azido-3′-deoxy-β-D-xylofuranosyl)adenine (21) led to the corresponding 9-(3′-amino-3′-deoxy-β-D-xylofuranosyl)-adenine 2′-5′ trimer 26 in which the two internucleotidic linkages are formally neutralized by intramolecular betaine formation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19890720810

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On the Macrolactonization of β-Hydroxy Acids. Crystal structures of the pentolide and the hexolide from (R)-3-hydroxybutanoic acid. Molecular modeling studies of the tetrolideDedicated to Prof. Dr. Wilhelm Simon on the occasion of his 60th birthday (1989)

Seebach, Dieter ; Brändli, Urs ; Müller, Hans-Martin ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1704-1717

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The temperature and concentration dependence of the previously reported formation of oligolides from (R)- or (S)-3-hydroxybutanoic acid under Yamaguchi's macrolactonization conditions (2,4,6-trichlorobenzoyl chloride/base) was studied. While the content of hexolide 2 in the product mixture is almost invariably ca. 35%, the amounts of pentolide 1 and of the larger rings strongly depend upon the temperature employed (Fig.1). Cyclic oligomers (5,6) are also obtained from 3-hydroxypentanoic acid. Enantiomerically pure β-butyrolactone can be used for the preparation of pento-, hexo-, and heptolide under Shanzer's macrolactonization conditions (tetra-oxadistannacyclodecane ‘template’). The X-ray crystal structures of the pentolide 1 and of two modifications (space groups C 2 and P 21) of the hexolide 2 were determined (Figs. 2-6 and Tables 1 and 5). No close contacts between substituent atoms and atoms in the rings or between ring atoms are observed in these structures. The hexolide C 2 modification is ‘just a large ring’, while the crystals of the P 21 modification contain folded rings the backbones of which resemble the seam of a tennis ball. A comparison of the torsion angles in the folded hexolide ring of the P 21 modification with those in the helical poly-(R)-3-hydroxybutanoate (PHB) suggests (Table 2) that the same interactions might be responsible for folding in the first and helix formation in the second case. Molecular modeling with force-field energy minimization of the tetrolide from four homochiral β-hydroxybutanoic acid units was undertaken, in order to find possible reasons for the fact that we failed to detect the tetrolide in the reaction mixtures. The calculated conformational energies (per monomer) for some of the tetrolide models (Figs. 7-9 and Tables 3 and 4) are not significantly higher than for the pentolide and hexolide crystal structures. We conclude that thermodynamic instability is an unlikely reason for the lack of tetrolide isolation. This result and failure to observe equilibration of pentolide 1 to a mixture of oligomers under the reaction conditions suggest that product distribution is governed by kinetic control.

Additional Material: 9 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19890720807

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