ZIB

101

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Chiral discrimination in the energetics of formation of diastereomeric adducts involving polypeptides (1986)

Paradossi, G. ; Pispisa, B. ; Rizzo, R. ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1249-1258

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Chiral discrimination in the energetics of formation of diastereomeric pairs between iron (III)-complex ions bound to poly(L-glutamate) or poly (D-glutamate) and L-catecholamines was measured by differential microcalorimetry at 25°C. When the association of substrates by Fe-polypeptide systems was virtually complete, diastereomeric discrimination energies of a few hundred calories per mol were observed, while diastereomeric discrimination entropies were found to be negligibly small. These results are consistent with the finding that the overall stereoselectivity in the electron transfer reaction between the optically active catecholamines and enantiomeric iron(III) materials - corresponding to Δ(ΔG≠) values around 900 cal/mol - is largely controlled by transition state effects in the kinetics.

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URL: http://dx.doi.org/10.1002/bip.360250706

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102

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Gel formation by fibrin oligomers without addition of monomers (1986)

Janmey, Paul A. ; Ferry, John D.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1337-1344

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Soluble fibrin oligomers were formed by reacting fibrinogen with thrombin under fine clotting conditions where the action of thrombin is the rate-determining step for polymerization, and by inhibiting the reaction shortly before gelation. Oligomeric fibrin was separated from unreacted fibrinogen and small oligomers by gel permeation chromatography. Electron microscopy revealed that the largest soluble fibrin oligomers resemble the protofibrils present in fine clots, but are somewhat shorter and entirely lack the twisted, trifunctional junctions that contribute to the elastic properties of fine clots. When thrombin was added to the soluble fibrin oligomers, polymerization resumed and clots were formed at a more rapid rate than from fibrinogen at the same concentration and resulted in a less-opaque clot under coarse clotting conditions. The results confirm a prediction of a theory for the polymerization of fibrin and provide additional evidence that the final state of a coarse fibrin clot depends on the mobility of protofibrils during its formation.

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URL: http://dx.doi.org/10.1002/bip.360250712

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103

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Sequence-dependence of the CD of synthetic double-stranded RNAs containing inosinate instead of guanylate subunits (1986)

Ratliff, Robert L. ; Liu, Jung-Jen ; Vaughan, Marilyn R. ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1735-1750

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The CD spectra and melting profiles have been measured for nine synthetic double-stranded RNAs containing I · C instead of G · C base pairs: poly[r(I) · r(C)], poly[r(I-C) · r(I-C)], poly[r(A-I-C) · r(I-C-U)], poly[r(A-C) · r(I-U)], poly[r(A-I) · r(C-U)], poly[r(A-C-C) · r(I-I-U)], poly[r(A-A-C) · r(I-U-U)], poly[r(A-C-U) · r(A-I-U)], and poly[r(A-U-C) · r(I-A-U)]. CD spectra have not previously been reported for the latter six of these polymers. The substitution of inosinate for guanylate led to recognizable CD differences, with all but two of the polymers having two resolved positive bands above 230 nm. Also, the I-containing RNAs differed from their G-containing counterparts in the almost complete absence of negative CD bands at long wavelengths and in the reduction of negative CD bands near 210 nm. First-neighbor comparisons showed that the CD spectra of the I-containing RNAs were consistent with the nearest-neighbor sequences of the polymers, as previously shown for G-containing RNAs (D. M. Gray, J.-J. Liu, R. L. Ratliff, and F. S. Allen, Biopolymers (1981) 20, 1337-1382). Moreover, two of the first-neighbor comparisons involved spectra of poly[r(A) · r(U)] and poly[r(I) · r(C)], polymers known to be in the A family of conformations in fibers (S. Arnott, D. W. L. Hukins, S. D. Dover, W. Fuller, and A. Hodgson, (1973) J. Mol. Biol. 81, 107-122). Thus, differences in the CD spectra of I- and G-containing RNAs could be simply explained as resulting from differences in the hypoxanthine and guanine chromophores, without invoking differences in conformation. Finally, melting temperatures of the I-containing RNAs were found to vary much less with base composition than do the melting temperatures of G-containing RNAs, since A · U base pairs are closer to I · C than to G · C base pairs in stability.

Additional Material: 5 Ill.

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URL: http://dx.doi.org/10.1002/bip.360250914

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104

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A positron annihilation study of hydrated DNA (1986)

Warman, John M. ; Eldrup, M.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1865-1874

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Positron annihilation measurements are reported for hydrated DNA as a function of water content and as a function of temperature (20 to -180°C) for samples containing 10 and 50% wt of water. The ortho-positronium mean lifetime and its intensity show distinct variations with the degree of hydration and with temperature for the 50% sample. The 10% water sample was relatively insensitive to temperature variation. The results indicate that hydrated DNA containing up to 10% water behaves as a rigid crystalline solid but that the rigidity markedly decreases with a further increase in water content until, for approximately 50% water, its properties resemble more those of a highly viscous fluid.

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105

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Comparison of the effects of cationic porphyrins on DNA properties: Influence of GC content of native and synthetic polymers (1986)

Banville, Debra L. ; Marzilli, Luigi G. ; Strickland, James A. ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1837-1858

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Interactions of meso-tetra(4-N-methylpyridyl)porphyrin [TMpyP(4)], meso-tetra(2-N-methylpyridyl)porphyrin [TMpyP(2)], and meso-tetra(para-N-trimethylanilinium)porphyrin (TMAP) with several native and synthetic DNAs were studied by a variety of physical techniques: nmr (31P and 1H), absorption spectroscopy, viscosity, and flow dichroism (FD). Of the three porphyrins studied, only the interaction of TMpyP(4) with poly [d(G-C)2] was fully consistent with intercalation. In particular, a large increase in viscosity, a downfield 31P-nmr signal (ca. -1 ppm), and upfield imino proton signals (11 to 12 ppm range) were observed. Comparison of the effects of TMpyP(4) on DNAs of different GC contents revealed larger changes in solution viscosity with increased GC content. However, the characteristic changes in 31P- and 1H-nmr spectra were not observed. The viscosity increases observed in studies with poly[d(A-C)(G-T)] and C. Perf. DNA were much lower than with poly[d(G-C)2], M. Lys. DNA, and calf thymus DNA. Thus, GC sequence and content are clearly important. The principal change in the 31P-nmr signal of native DNA is the appearance of a very broad shoulder centered at ca. -2.0 ppm, which is larger in M. Lys. DNA than in C. Perf. DNA. FD studies indicate highly ordered TMpyP(4) cations arranged perpendicular to the DNA axis of calf thymus DNA. Together, these results suggest the major effects of TMpyP(4) on DNA properties are due to strong GC-binding interactions that influence DNA structure. The data are consistent with combined intercalative and outside binding interactions of TMpyP(4) with GC regions of DNA. In contrast, similar studies with TMAP suggest that it influences AT regions of DNA by an outside binding mode. On the other hand, TMpyP(2) effects on DNA properties are consistent with nonselective outside binding.

Additional Material: 11 Ill.

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URL: http://dx.doi.org/10.1002/bip.360251003

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106

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Conformational properties of somatostatin. VI. In a methanol solution (1986)

van den Berg, E. M. M. ; Jans, A. W. H. ; van Binst, G.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1895-1908

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The peptide hormone, somatostatin, has been studied by nmr at 500 MHz in a methanol solution and at low temperature (263 K) in order to investigate a possible similarity with conformationally restricted biologically active analogs. The more pronounced predominancy of one conformer already present in a water solution is demonstrated. No evidence has been shown for interactions between Phe11 and other Phes in the molecule.

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URL: http://dx.doi.org/10.1002/bip.360251007

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107

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Thermodynamics of water-biopolymer interactions: Irreversible sorption by a single, uniform sorbent phase (1986)

Bryan, William P.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1967-1979

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Sorption isotherms of water vapor by solid biopolymers are necessary for the determination of thermodynamic quantities for water-biopolymer interactions. Such isotherms are generally irreversible, so equilibrium thermodynamics may not be applicable. General relationships are derived for thermodynamic quantities of sorption when the sorbent is a single uniform phase. In general, use of the Clausius-Clapeyron equation allows correct determination of differential entropies of sorption. However, calorimetric data are also necessary for the correct determination of other thermodynamic quantities. The single uniform phase model appears more useful than a domain model in explaining the hysteresis seen in water-biopolymer sorption isotherms.

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108

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Specificity in DNA interactions: An nmr investigation of the interaction of propidium with oligodeoxyribonucleotides containing normal and G · T base pairs (1986)

Wilson, W. David ; Jones, Robert L. ; Zon, Gerald ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1997-2015

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The interaction of propidium with three self-complementary oligodeoxyribonucleotides has been investigated by 1H- (base-pair imino proton assigned by 1D NOE and saturation transfer methods) and 31P-nmr as a function of ratio of propidium to oligomer (from zero to saturation) and temperature. The three oligomers are dTATATGCGCATATA (1), dTATATGTGCATATA (2), which has the same sequence as 1 except for the mismatched base pair at position 7, and dTATGTGCATA (3), which is a shortened version of 2. The imino proton chemical-shift changes of 1 on titration with propidium can be explained by the effects of the ring-current anisotropy of propidium at intercalation (3.4 Å) and next-neighbor sites (6.8 Å). The results indicate that propidium binds with neighbor exclusion but with no significant specificity for any intercalation site in the sequence of 1. The addition of propidium to 1 results in general downfield shifts of all 31P signals, as expected for a nonspecific intercalator. Imino and 31P-nmr spectra for 2 indicate that this oligomer forms a hydrogen-bonded G · T base pair at position 7 with little change in base pairing and stacking of base pairs 1-6 compared to 1. The results for addition of propidium to 2 and 3 are quite different than with 1. At low ratio only secondary shifts (6.8 Å) are seen for the G and T imino protons of base-pair 7 on addition of propidium. At higher ratios of propidium, the signals for these G and T protons are lost in 2 and severely broadened in 3, even at low temperature. The other potential intercalation sites in 2 and 3 appear to bind propidium strongly and without significant specificity as with 1. 31P spectra of 2 in the presence of propidium show the expected downfield shifts and broadening. Thus, the minor differences in local helix geometry in 1, and in 2 and 3, away from the G · T base pair do not significantly affect propidium intercalation specificity. Having one or two G · T base pairs at a site, however, makes intercalation in the standard manner significantly less favorable.

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URL: http://dx.doi.org/10.1002/bip.360251013

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109

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An analysis of circular intensity differential scattering measurements: Studies on the sperm cell of eledone cirrhosa (1986)

Wells, K. Sam ; Beach, David A. ; Keller, David ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2043-2064

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: This study represents the first systematic attempt to characterize the possible sources of artifacts that can interfere with the measurement of circular intensity differential scattering (CIDS) as a function of the scattering angle. A theoretical analysis of the effect of imperfect incident circular polarizations in the measurement of baselines from nonchiral scatterers and in the signals from chiral samples is derived. From this analysis the requirements of the tolerance on the quality of the incident circular polarizations to unequivocally measure the CIDS effect are established. The protocol for alignment of the CIDS instrument and the characterization of the incident polarizations utilized in these studies are described in detail. CIDS measurements on suspensions of helical sperm cells are presented. The experimental results are modeled computationally with the use of the current CIDS theory. Good agreement between the data and the computations is obtained. The results clearly indicate the ability of CIDS to provide information on the long-range chiral organization of samples in solution.

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URL: http://dx.doi.org/10.1002/bip.360251103

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110

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The dielectric constant of a folded protein (1986)

Gilson, Michael K. ; Honig, Barry H.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2097-2119

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The goal of this paper is to obtain a theoretical estimate of the dielectric constant of a folded protein. To this end, we develop a form of the Kirkwood-Fröhlich dielectric theory that applies to polar solids and folded proteins. The resulting theory incorporates a factor expressing the degree to which dipolar groups are constrained within the material's structure, as well as a generalized form of Kirkwood's correlation factor. The theory is applied to a hypothetical isotropic protein composed of randomly oriented α-helices and having a number density of dipolar groups equal to that found in actual proteins. The factor of constraint and the generalized dipole correlation factor are calculated using normal mode analysis. Temperature factors are also computed by normal mode analysis and are in reasonable agreement with those found experimentally. The computed dielectric constant is low; the best estimate is that it falls between 2.5 and 4.

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URL: http://dx.doi.org/10.1002/bip.360251106

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111

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Molecular orbital calculations on the oligopeptides netropsin, distamycin and related compounds (1986)

Manning, Mark C. ; Woody, Robert W.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2065-2082

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The electronic structure of the antibiotics netropsin, distamycin A, and related compounds has been examined by various theoretical models. Calculations of both the Pariser-Parr-Pople (PPP) and the semiempirical CNDO/S types can account for the absorption spectrum of netropsin and distamycin A. The CD spectrum has been calculated for the conformation of netropsin found in the crystal structure of a netropsin/DNA dodecamer. Not all the CD spectral features can be attributed entirely to the chiral conformation of netropsin, indicating that there are significant interactions between netropsin and DNA. A CD calculation was also performed for distamycin A in a similar conformation. An examination of the charge-density maps of the excited states suggests that there is substantial charge transfer from the pyrrole ring to either of the adjacent peptide linkages in these systems. At higher energies, even longer distance charge transfer can be observed. Similar behavior was seen in the monomers pyrrole-2-carboxamide and 3-(formylamino)pyrrole.

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URL: http://dx.doi.org/10.1002/bip.360251104

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112

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Masthead (1986)

New York : Wiley-Blackwell

Biopolymers 25 (1986)

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bip.360251201

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113

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A novel peptide conformation: First unequivocal observation of the oxy-analog of a β-bendThis paper is part 157 of the Linear Oligopeptides series; for part 156 see Ref. 1. (1986)

Toniolo, Claudio ; Valle, Giovanni ; Bonora, Gian Maria ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2237-2253

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The x-ray diffraction analysis of the N-benzyloxycarbonyl homo-tripeptide from α-amino-isobutyric acid has shown the occurrence of an incipient 310-helix characterized by one type-III (or type-III′) β-bend followed by one oxy-analog of the same type of β-bend. This represents the first unequivocal observation of the latter conformation, where the O - H group of the COOH moiety present at the C-terminus of the peptide main chain plays the role of the hydrogen-bonding donor. These results have been compared with those of the same peptide in its monohydrate form and of its methyl ester derivative, the x-ray diffraction structures of which are also described here.

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URL: http://dx.doi.org/10.1002/bip.360251203

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Synthesis of fragments by classical solution methods for use in cytochrome c semisynthesisThe amino acid residues, except glycine, are of the L-configuration. For a simpler description, the customary L-designation for individual amino acid residues is omitted. Standard abbreviations for amino acid derivatives and peptides are used according to the suggestion of the IUPAC-IUB Commission on Biochemical Nonemclature (1972) Biochemistry 11, 1726-1732. (1986)

Borin, Gianfranco ; Marchiori, Fernando ; Calderan, Andrea ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2271-2279

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: We report details of the chemical synthesis of two fragments reproducing the C-terminal sequences 71-108 and 70-108 of Saccharomices cerevisiae cytochrome c. Preparation of the fragments employed classical solution methods and a fragment-condensation strategy; they have been used, together with a third fragment (sequence 67-108) [L. Moroder, B. Filippi, G. Borin & F. Marchiori (1975) Biopolymers 14, 2061-2074], in the semisynthesis of chimeric cytochromes [C. J. A. Wallace, G. Corradin, F. Marchiori & G. Borin (1986) Biopolymers 25, 2121-2132].

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URL: http://dx.doi.org/10.1002/bip.360251205

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115

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Evidence for a folded structure of met-enkephalin in membrane mimetic systems: 1H-nmr studies in sodiumdodecylsulfate, lyso-phosphatidylcholine, and mixed lyso-phosphatidylcholine/sulfatide micelles (1986)

Zetta, Lucia ; De Marco, Antonio ; Zannoni, Giulio ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2315-2323

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: 1H-nmr spectra of Met-enkephalin dissolved in aqueous solution of sodiumdodecylsulfate (SDS) micelles are reported as a function of pH and temperature. The temperature behavior of the amide protons is compared with that observed for the same peptide dissolved in aqueous solution of lyso-phosphatidylcholine (LPC) and lyso-phosphatidylcholine-sulfatide (LPC-SH) micelles. The temperature coefficients are affected by the micelle polarity, which suggests that the peptide backbone is not remote from the micelle surface. pH titration performed in the presence of SDS micelles gives a number of intrinsic and extrinsic pKa values, indicative of a folded structure of the opioid molecule. This conformation is characterized by the existence of an intramolecular hydrogen bond involving the Met-5 amide proton and an interaction of the N-terminal residue with the aliphatic side chains of both Phe-4 and Met-5.

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URL: http://dx.doi.org/10.1002/bip.360251209

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116

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Helix → β conformational transition of poly(L-lysine) on dye binding (1986)

Scaria, P. V. ; Atreyi, M. ; Rao, M. V. R.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2349-2358

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Binding of an azo dye, 4′-dimethyl amino azo benzene-4-carboxylic acid (DAAC) to poly(L-lysine) (PLL) in basic aqueous solutions at 20°C has been studied. The azo dye was found to bind to PLL when its side-chain amino groups are in the uncharged state. This was found to be a cooperative phenomenon, and the binding constant and cooperativity factor have been evaluated. The binding of the dye was found to result in a conformational transition of PLL from the α-helix to the β-sheet, which in turn helps in increased dye binding.

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URL: http://dx.doi.org/10.1002/bip.360251212

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Concentration of protein in fibrin fibers and fibrinogen polymers determined by refractive index matching (1986)

Voter, William A. ; Lucaveche, Carmen ; Erickson, Harold P.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2375-2384

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: We have used refractive index matching to determine the concentration of protein in the fibers in fibrin clots and of needlelike crystals of native fibrinogen. Our results are in agreement with those of Carr and Hermans [(1978) Macromolecules 11, 46-50], as determined by light scattering - namely, that protein makes up about 20% of the volume of the fiber. However, we have found that the protein concentration is strongly dependent on ionic strength. An increase in ionic strength caused a substantial drop in the protein concentration. In a buffer containing 100 mM NaCl, the protein concentration was 26.6-29.8 g of protein per 100 cm3 of polymer, and at 200 mM NaCl it was reduced to 22.1-23.1 g/100 cm3.

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Chemical synthesis of polysaccharides. 7. Enzymatic hydrolysis of (1 → 6)-α-DL-glucopyranan (DL-dextran) (1986)

Okada, Masahiko ; Sumitomo, Hiroshi ; Hirasawa, Takahito

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 1955-1965

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Hydrolysis of (1 → 6)-α-DL-glucopyranan (synthetic DL-dextran) by an endo-dextranase from a Penicillium species was examined in an acetate buffer solution (pH 5.3) at 37°C. Three samples of different tacticities (isotactic dyad content, 55, 63, and 72%) were employed with a clinical dextran for comparison. Colorimetric determination of the reducing end units of the saccharides produced during hydrolysis showed that the maximum degrees of hydrolysis based on the D-glucose units, (D.H.)D, for the DL-dextrans were 21.4, 27.8, and 33.0% in the order of increasing isotacitic dyad content, whereas the (D.H.)D value for the clinical dextran was 51.9%. A statistical treatment of the enzymatic hydrolysis is proposed to interpret the experimental results.

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D-Isomeric replacements within the 6-9 core sequence of ac-[Nle4]-α-MSH4-11-NH2: A topological model for the solution conformation of α-melanotropin (1986)

Sugg, Elizabeth E. ; Cody, Wayne L. ; Abdel-Malek, Zalfa ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2029-2042

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Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Analogs of Ac-[Nle4]-α-MSH4-11-NH2 and Ac-[Nle4, D-Phe7]-α-MSH4-11-NH2 were prepared with D-isomeric replacements at the His6, Arg8, and Trp9 residues. The requirement for an indole moiety at position 9 also was evaluated by replacement with L-leucine in both parent fragment analogs. D-isomeric replacements at positions 6 and 8 in either series were detrimental to biological potency in frog (Rana pipiens) and lizard skin (Anolis carolinensis) in vitro melanotropic assays. However, Ac-[Nle4, D-Trp9]-α-MSH4-11-NH2 and Ac-[Nle4, D-Phe7, D-Trp9]-α-MSH4-11-NH2 were equipotent and 10 × more potent than Ac-[Nle4]-α-MSH4-11-NH2, respectively, in the lizard skin bioassay, and 30 and 1900 times more potent in the frog skin bioassay. Ac-[Nle4, D-Phe7, D-Trp9]-α-MSH4-11-NH2 was 3 × more potent than α-MSH in the frog skin bioassay. Proton nmr studies in aqueous solution revealed a marked preservation of the backbone conformation of these linear analogs. Chemical-shift variations due to the through-space anisotropic influence of the core aromatic amino acid residues permitted evaluation of side-chain topology. The observed topology was consistent with nonhydrogen-bonded β-like structure (φ = -139°, ψ = +135° for L-amino acids; φ = +139°, ψ = -135° for D-amino acids) as the predominant solution conformation. The biological and conformational data suggest that high melanotropic potency requires a close spatial arrangement of the His6, Phe7, and Arg8 side chains.

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Cytochrome c chimerae from natural and synthetic fragments: Significance of the biological properties (1986)

Wallace, Carmichael J. A. ; Corradin, Giampietro ; Marchiori, Fernando ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2121-2132

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Analogs of natural proteins have application in basic research, in medicine, and increasingly, in industry. Of the many methods developed for the fabrication of modified proteins, semisynthesis has so far been the most productive [R. E. Offord (1983) Proc. Eur. Peptide Symp., 17 31-42]. The technique of fragment-condensation semisynthesis takes as its basic raw material the native protein; fragments derived from it are manipulated by sequential degradation and resynthesis before recombination. While gene manipulation may overtake protein manipulation in general usefulness, certain types of analogs will remain accessible only by semisynthesis. Fragment condensation semisynthesis, as described above, has been used in preparing cytochrome c analogs [C. J. A. Wallace (1979) Proc. Am. Peptide Symp. 6, 609-612]. To overcome the difficulty of replacing amino acids far from convenient cleavage sites, a number of variants of the method have also been used. These include fragment-specific chemical modification [C. J. A. Wallace & K. Rose (1983) Biochem. J. 215, 651-658] and solid-phase synthesis of small [P. J. Boon, G. I. Tesser, H. H. K. Brinkhof & R. J. F. Nivard (1981) Proc. Eur. Peptide Symp. 16, 127-130] or large fragments [L. E. Barstow, R. S. Young, E. Yakali, J. J. Sharp, J. C. O'Brien, P. W. Berman & H. A. Harbury (1977) Proc. Natl. Acad. Sci. USA 74, 4148-4250]. The latter study gave low final recoveries, so we have prepared large peptides (38-42 residues) by classical solution methods. We have examined both their use in the reformation of the complete protein, and the physical and biochemical properties of the product analogs compared with those of the native proteins.

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The effect of monovalent cations on the association behavior of guanosine 5′-monophosphate, cytidine 5′-monophosphate, and their equimolar mixture in aqueous solution (1986)

Walmsley, Judith A. ; Sagan, Barbara L.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2149-2172

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: 1H- and 31P-nmr spectroscopy have been used to investigate the self-association of M2(5′-CMP) [M = Li+, Na+, K+, Rb+, or (CH3)4 N+; 5′-CMP = cytidine 5′-monophosphate], the self-association of Li2(5′-GMP) (5′-GMP = guanosine 5′-monophosphate), and the heteroassociation of 5′-GMP and 5′-CMP (1 : 1 mole ratio) in aqueous solution as a function of the nature of the monovalent cation. Proton spectral differences for the different 5′-CMP salts exhibit a cation-size dependence and have been ascribed to a change in the stacking geometry. An average stacking association constant of 0.63 ± 0.24M-1 at 1°C, consistent with the weak stacking interactions of the cytosine bases, was determined for the 5′-CMP salts. Heteroassociation of 5′-GMP and 5′-CMP follows the reverse of the cation order for the formation of ordered aggregates of 5′-GMP. Heteroassociation occurs in the presence of Li+, Na+, and Rb+ ions, but only self-association occurs for the K+ nucleotides. Li2(5′-GMP), which does not form ordered species, self-associates to form disordered base stacks with a stacking constant of 1.63 ± 0.11M-1 at 1°C.

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Structural investigation of poly-L,D-proline, a synthetic ion channel across bilayer membranes: Crystal structure and molecular conformation of two tetra-D,L-proline derivatives (1986)

Colapietro, M. ; De Santis, P. ; Palleschi, A. ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2227-2236

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The crystal structures and molecular conformations of two tetraproline derivatives with alternating configurations Boc(D-Pro,L-Pro)2OH and Boc(D-Pro,L-Pro)2OCH3 are investigated in connection with the ability of the homologous polymer to selectively increase (as an ion channel) the ion permeability across bilayer membranes. Both tetramers are characterized by the cis-trans alternating conformation of the peptide bonds, which formally transforms in a turn of the poly-D,L-proline channel after a cis-trans change of the central peptide residue.

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Sol-sol structural transition of aqueous agarose systems (1986)

Biagio, P. L. San ; Madonia, F. ; Newman, J. ; [et al.]

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2255-2269

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A structural transition is reported to occur in aqueous sols of agarose, an electrically uncharged biostructural polysaccharide. The transition has no measurable effect on size dispersity on the shape of the solute polysaccharide as observed by precision photon correlation spectroscopy. It originates a low-angle pattern of scattered light similar to that which monitors phase separations in polymer blends. Thus, it must be due to some extent to spatially modulated polymer clustering, typical of spinodal decomposition. In the interval of temperatures studied, it precedes very distinctly in time the thermoreversible sol-gel transition, which is known to be promoted at higher concentrations. It also anticipates to an appreciable extent the spatial density modulation observed in the gel. Although reported here for the first time, a spinodal decomposition of the sol that precedes and possibly triggers the processes leading to gelation does not come unexpectedly in terms of site-bond correlated-percolation theory. In general, this occurrence raises the question as to whether the spontaneous onset of regions of higher and lower polymer concentration (spinodal separation) may be regarded as a novel path for biomolecular interactions and the self-assembly of order in biomolecular systems.

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Energy transfer in polynucleotide homopolymers and copolymers (1986)

Burns, Victor W.

New York : Wiley-Blackwell

Biopolymers 25 (1986), S. 2309-2313

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ISSN: 0006-3525

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Using the fluorophore Tb3+ as a reporter, the effect of thallium (Tl+1) on the transfer of energy in polyribonucleotides and polydeoxynucleotides at room temperature has been studied. In p(G), p(G, I), and pd(G)6 thallium greatly increases the transfer of uv energy absorbed by the bases to Tb3+. In DNA, p(G, U), p(G, A), p(A, U), p(X), p(A), p(U), p(I), pd(G, A)6, and pd(G, T)5 thallium has little or no effect. Thallium increases intersystem crossing to the triplet states only in p(G), p(G, I), and pd(G)6, and the triplets overlap the excited singlet state in Tb3+. In those G- and X-containing polymers showing little thallium effect, the evidence suggests that intersystem crossing is comparatively high to begin with. These polymers, including DNA, appear to transfer absorbed energy to triplet states efficiently at room temperature.

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Chemistry-Experiment and Theory. Von B. G. Segal. John Wiley & Sons, New York - Chichester - Brisbane - Toronto - Singapore 1985. 1000 S., ca. 42.50 $. ISBN 0-471-80811-3 (1986)

Müller, Horst

Weinheim : Wiley-Blackwell

Chemie in unserer Zeit 20 (1986), S. 67-67

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ISSN: 0009-2851

Keywords: Chemistry ; Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/ciuz.19860200207

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Preparation of Optically Active Secondary Amines by Thermal Decomposition of (Methylbenzyl)urea Analogs: Absolute Configuration of (+)- and (-)-Mecamylamine. Preliminary CommunicationThe full paper will be published elsewhere.Patent application has been filed. (1986)

Schönenberger, Bernhard ; Brossi, Arnold ; George, Clifford ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 283-287

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Thermolysis of the (α-methylbenzyl)urea diastereoisomers 4 and 5 of (±)-mecamylamine ((±)-1) and 6 and 7 of (±)-1-noreseroline O-methyl ether ((±)-3) in refluxing alcohol afforded optically pure amines in high yield, besides optically pure carbamates of (α-methylbenzyl)amine which can be recycled. The absolute configuration of (-)-mecamylamine hydrochloride ((-)-1 · HCl) was determined by X-ray diffraction analysis.

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2,5-Chinonmethide des 1,6-Methano[10]annulens mit S,N- und N,N-Acylketenacetal StrukturMeinem hochverehrten Lehrer, Prof. Dr. Siegfried Hünig, Würzburg, zum 65. Geburtstag gewidmet (1986)

Neidlein, Richard ; Hartz, Georg

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 315-328

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: 2,5-Quinonemethides of 1,6-Methano[10]annulene with the Structures of S,N- and N,N-Acylketene AcetalsInvestigation on the chemical reactivities of 2-(tert -butoxy)-1,6-methano[10]annulene and the syntheses of the compounds 2, 4, 6-8, 11, 13-22 are described; the results of 1H- and 13C-NMR-spectroscopic measurements are reported.

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1,2-Epoxycarotinoide. 6. Mitteilung. Isolierung von 1′,2′-Epoxy-1′,2′-dihydro-ε,ψ-carotin aus der ‘Delta-Mutanten’-Tomate (1986)

Berset, Daniel ; Pfander, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 340-344

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: 1,2-Epoxycarotenoids Isolation of 1′,2′-Epoxy-1′,2′-dihydro-ε,ψ-carotene from a ‘Delta Mutant’ TomatoFrom ‘Delta Mutant’ tomatoes, optically active 1′,2′-epoxy-1′,2′-dihydro-ε,ψ-carotene (7) was isolated. According to the CD data, the configuration is 6R and presumably 2′S.

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(Cholestanyloxycarbonyl)benzyl esters as peptide substituents: Conformational properties of fully protected oligo-L-lysines with C-terminal (cholestanyloxycarbonyl)benzyl and benzyl ester moieties (1986)

Toniolo, Claudio ; Bonora, Gian Maria ; Moretto, Vittorio ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 350-358

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: This study involves L-lysine oligo peptides, protected at the N-terminus by the Nps and at the ε-amino functions by Boc groups. Two series were prepared from dimer to octamer, one containing the p-[(cholestan-3β-yloxy)carbonyl]benzyl, the other one the benzyl ester group at the C-terminus. Conformational analyses were performed by IR absorption. The occurrence of the intermolecular β-structure in the solid state and in CH2Cl2 solution was demonstrated for the highest oligomers. The relative stabilities of the self-associated species were determined by adding a variety of polar solvents to the CH2Cl2 solutions. The cholestanyl-containing peptides have a lower propensity to self-aggregate than the benzyl-ester analogues. Self-aggregation and decreasing solubility run in parallel. It was also directly shown that soluble urea derivatives may disrupt intermolecular H-bonds in CH2Cl2, a point of practical interest, particularly in solid-phase peptide synthesis.

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Die toxischen und sedierend wirkenden Bufadienolide von Kalanchoedaigremontiana HAMETet PERR (1986)

Wagner, Hildebert ; Lotter, Hermann ; Fischer, Manfred

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 359-367

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The Toxic and Sedative Bufadienolides of Kalanchoe daigremontiana HAMET et PERR.From the toxic Crassulacee Kalanchoe daigremontiana five biosynthetically related bufadienolides have been isolated and structurally elucidated by X-ray and 1H- and 13C-NMR spectroscopy. The compounds were identified as bersaldegenin 1,3,5-orthoacetate (2), bersaldegenin 1-acetate (4), bersaldegenin 3-acetate (3), 1β,3β,5,11α,14-pentahydroxy-12,19-dioxo-5β,14β-bufa-20,22-dienolide 1,3,5-orthoacetate ( = daigremontianin; 1), and 3β-acetoxy-1β,5,14-trihydroxy-5β,14β-bufa-20,22-dienolide ( = daigredorigenin-3-acetate, 5). According to the pharmacological investigations, the two orthoacetates 1 and 2 comprise the positive inotropic, sedative, and toxic activity of the plant.

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Enantioselective Synthesis of D-erythro-Sphingosine and of Ceramide (1986)

Julina, Radomir ; Herzig, Thomas ; Bernet, Bruno ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 368-373

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The enynol 2 was transformed into D-erythro-sphingosine 11 (7 steps, 46%) and into ceramide 1 (8 steps, 41% overall yield). The key steps were the mono-epoxidation of the enynol 5 (Ti(t-BuO)4, (-)-D-diethyl tartrate, t-BuOOH) to 6 (86%, ≥ 98% ee), the regioselective intramolecular opening of the oxirane 6 via the benzylurethane 7, and the reductive tranformation of the acetylene 9 into the oxazolidinone 10 (Li, EtNH2, 88%).

Additional Material: 1 Ill.

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An ESR Study of the Radical Cations of Tetrathiafulvalene (TTF) and Electron Donors Containing the TTF Moiety (1986)

Ćavara, Luka ; Gerson, Fabian ; Cowan, Dwaine O. ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 141-151

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Hyperfine data and g factors are reported for the radical cations of tetrathiafulvalene (TTF; 1) and of its derivatives 2-13. From the intense satellite spectra of 1+-13+ not only the coupling constants of the 33S isotopes in the TTF moiety could be determined, but also, in favourable cases, those of the 13C isotopes in the central double bond. The former values range from 0.370 (8+) to 0.470 mT (4+) and the latter from 0.255 (8+) to 0.360 mT (4+) in the radical cations of bis(ethylenedithio)-TTF (8+) and tetracyano-TTF (4+). The radical cation of TTF (1+) exhibits intermediate values, 0.425 for the 33S and 0.285 mT for the 13C isotopes. The spin population in 1+-13+ resides, to a large extent, in the central S2C = CS2 part of the π-system. It tends to increase (decrease) by substitution with electron-accepting (donating) groups in the 2,3,6,7-positions of TTF.

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URL: http://dx.doi.org/10.1002/hlca.19860690117

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Conformation-Odor Relationships in Norlabdane Oxides (1986)

Ohloff, Günther ; Vial, Christian ; Demole, Edouard ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 163-173

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Conformational factors have been found responsible for the dramatic change in odor between (-)-deoxyambreinolide (12) and its (+)-epi derivative 13. The presumably molecular event during the receptor interaction has been simulated by the diastereoisomeric 11-methyl-ambrox derivatives 3 and 5 as model compounds.

Additional Material: 1 Tab.

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Crystal Structures of Chiral Ionophores: Bis(9,9′-spirobifluorene)-26-crown-4 and -32-crown-6 (1986)

Egli, Martin ; Dobler, Max

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 626-631

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The X-ray crystal structures of bis(9,9′-spirobifluorene)-26-crown-4βbenzene solvate (monoclinic, a = 15.47 Å, b 11.265 Å, c = 15.220 Å, β = 91.54°, space group C2) and bis(9,9′-spirobifluorene)-32-crown-6·dichloromethane solvate (tetragonal, a = 20.958 Å, c = 11.779 Å, space group P41212) are described. Both compounds act as enantioselective ionophores for α-aminoalcohols.

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URL: http://dx.doi.org/10.1002/hlca.19860690312

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Steric Effects on Reaction Rates. Part VIII. The Significance of Front Strain Release in Solvolysis of Bridgehead Derivatives (1986)

Müller, Paul ; Blanc, Jacky ; Mareda, Jiri

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 635-645

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The steric requirements of leaving groups for 14 bridgehead derivatives have been examined using MM2 calculations. The strain varies almost monotonously throughout the series upon variation of the leaving group from H to C1, OH, CH3, CH3CH2O, (CH3)3CO, (CH3)3C and no significant trends for differential F-strain effects are detected expect for the perhydrophenalene derivative 13. The experimental rates of solvolysis of bridgehead derivatives correlate well with the calculated steric energy differences between substrate R-X and the corresponding carbenium ion R⊕. However, the strain calculations using the more recent force-fields (MM2) disagree, in part, with those reported in the literature: chloride and p-toluenesulfonate leaving groups correlate with identical slopes, and the perhydrotriquinacene derivative 10 shows no anomalous behavior. The calculations suggest that F-strain and C,C-hyperconjugation should not play any dominant role in bridgehead solvolysis.

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Die Synthese und der thermische Zerfall des 1,2-Diazabenzo[e]-semibullvalens und dessen Beziehung zur Thermolyse des Benzobenzvalens (1986)

Burger, Ulrich ; Mentha, Yves ; Jean Thorel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 670-675

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The Synthesis and the Thermal Decay of 1,2-Diazabenzo[e]semibullvalene and its Relation to the Thermolysis of BenzobenzvaleneThe [4 + 2]-photoadduct of naphthalene and 4-phenyl-4H-1,2,4-triazol-3,5-dione (PTAD) was subjected to a triplet-sensitized di-π-methane rearrangement. Hydrolysis of the resulting urazol 15 gave a stable semicarbazide 16 which by nickel-peroxide oxidation gave 1,2-diazabenzo[e]semibullvalene (10). At 40 °C, the latter decays in CHCl3 solution to produce benzofulvene (2) as the principal product, accompanied by benzobenzvalene (1) and small amounts of naphthalene. This decay reaction is rationalized in terms of a 1,3-dipolar cycloreversion which is followed by denitrogenation to give indenyl carbene (19). The thermolysis of 1 in solution is believed to proceed via the same carbene. At present, these findings provide only a partial answer to the benzobenzvalene enigma (i.e., in solution at 150°, 1 gives 2, but in the gas-phase at 300°, 1 yields naphthalene). MeOH is shown to add readily to 10 in a homologous Michael addition.

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URL: http://dx.doi.org/10.1002/hlca.19860690317

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Formale Totalsynthese von (±)-Isocomen durch Anwendung der α-Alkinon-Cyclisierung (1986)

Manzardo, Giuseppe G. G. ; Karpf, Martin ; Dreiding, André S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 659-669

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Formal Total Synthesis of (±)-Isocomen by Application of the α-Alkinon CyclizationA total synthesis of the racemic form of the sesquiterpene isocomene (A) was accomplished by application of the cyclopentenone anellation B→D (Scheme 1) which includes the α-alkynone cyclization C→D, a gas-phase flow thermolytic process. Starting with the known product 2 (Scheme 3) of the anellation B→D, the elaboration of ring C of A proceeded in 9 steps to the α-alkynone 16 (Scheme 5) which was cyclized at 540° selectively to give the angularly fused triquinane 4 (77%). A two-step procedure then led to 5 (Scheme 6), a last but one intermediate in a known total synthesis of (±)-A. The conversion of 16 to 4 also demonstrated the compatibility of an acetoxy function with the anellation sequence B→D.

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URL: http://dx.doi.org/10.1002/hlca.19860690316

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Photochemical Rearrangements of 5,6-Epimino-5,6-dihydro-β-ionone and Derivatives (1986)

Müller, Ernst Peter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 692-697

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: On irradiation at -20°, 5,6-epimino-5,6-dihydro-β-ionone (E)-3 rearranges to the products 6 and 7. The N-methyl derivative (E)-4 does not lead to any photoproduct upon brief irradiation; on prolonged irradiation, only unspecific photodecomposition is observed. The N-acylated derivative (E)-5 undergoes rapid (E)/(Z)-isomerization and slow rearrangement to 12 and 13.

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Pteridine. Teil LXXX.Teil LXXIX: [1]. Synthese, Reaktionen und Photochemie von Pteridinthionen (1986)

Heekel, Armin ; Pfleiderer, Wolfgang

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 708-717

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Synthesis, Reactions, and Photochemistry of PteridinethionesThe pteridine-6(5H)-thione 1 and various pteridine-7(8H)-thiones (13, 22, 26) have been synthesized, and their photochemical reactivity has been investigated under aerobic conditions. The formation of different photooxidation products is pH-dependent. In acidic to neutral media, disulfides (2, 15, 23, 29) are formed, whereas neutral to alkaline solutions favour the formation of pteridinesulfinic (3, 17) and -sulfonic acids (6, 16, 24, 30). Prolonged irradiation of the disulfides 2 and 15 led to the intensively yellow fluorescing bis(thio)dilumazines 19 and 20, respectively.

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URL: http://dx.doi.org/10.1002/hlca.19860690323

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Cacospongione A, cacospongienone A, and cacospongienone B, new C21 difuran terpenoids from the marine sponge Cacospongiascalaris SCHMIDT of the Côte d' Azur (1986)

Guella, Graziano ; Amade, Philippe ; Pietra, Francesco

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 726-733

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The sponge Cacospongia scalaris (family Thorectidae), collected at the Cap de Nice (Cǒte d'Azur), is shown to contain a series of truncated, linear C21 difuran terpenoids comprising the known sponge products furospongin-1 ((+)-1), furospongin-2 (2), and dihydrofurospongin-2 ((-)-(E)-3), besides the new products cacospongione A ((-)-4), cacospongienone A ((-)-(Z)-6), and cacospongienone B ((-)-(E)-6), whose absolute configurations have been assigned by chemical correlations with (+)-1. Possibly, one of the two cacospongienones is an artifact, as these two terpenoids interconvert on standing. This is the first finding of linear C21 difuran terpenoids, which are typical of the Spongiidae, in a member of the family Thorectidae.

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URL: http://dx.doi.org/10.1002/hlca.19860690325

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Mitteilungen (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 749-750

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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.19860690327

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Deoxy-nitrosugars 12th communication11th Communication: [1]. Synthesis of isosteric mono-phosphonate analogues of β-and α-D-fructose 2,6-bisphosphate (1986)

Meuwly, Roger ; Vasella, Andrea

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 751-760

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: A synthesis of the isosteric mono-phosphonate analogues 2a and 19 of the β-and α-D-fructose 2,6-bisphosphate, respectively, is described. Chain elongation of the 1-deoxy-1-nitro-D-arabinose 3 (Scheme 1) by a Henry reaction with paraformaldehyde followed by protection of the resulting alcohol (methoxymethyl ether) and a radical-chain substitution by nitromethane anion gave the key intermediates, the gluco-anhydroalditol 6 and the manno-anhydroalditol 7. These products equilibrated under basic conditions. Conversion of 7 to the aldehyde 9, Abramov reaction of 9 with diphenyl phosphite followed by deoxygenation according to Barton gave the phosphonate 11 (Scheme 2). Selective hydrogenolysis of 11, phosphorylation and deprotection gave 2 which was converted to the tetrasodium salt 2a. Similarly, 6 was transformed into the isosteric phosphonate analogue 19 of the α-D-fructose 2,6-bisphosphate (Scheme 3).

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Sequence dependence of secondary-structure formation part IVPart III: [1]. Helix-forming potential of amphiphilic oligopeptides containing aib residues (1986)

Mutter, Manfred ; Altmann, Karl-Heinz ; Flörsheimer, Andreas ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 786-792

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The conformational properties of Aib-containing oligopeptides having the propensity to adopt amphiphilic helical conformations were investigated by CD spectroscopy in solution. The peptides CF3COOH.H-Pro-Glu-[Ala-Aib-Glu-Aib-]4Gly-OH (I), HCl.H-Pro-Ala-Aib-[Gul-Ala-Ala-Aib-]2Glu-Ala-Aib-Gly-PEGM (II), and CF3COOH.H-Ala-Aib-[Glu-Glu-Ala-Aib-]3PEGM (III) were synthesized according to the general principles of the liquid-phase method for peptide synthesis. Peptides I-III exhibit helical conformations in CF3CH2OH, MeOH, and in H2O at acidic pH; however, at pH 7, only II forms a stable helix, whereas I and III are predominantly in an unordered conformation. Some general features for the construction of amphiphilic helices are discussed in the light of the experimental data.

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Conformational Analysis of Endoperoxides Grafted onto Bicyclo[2.2.n]alkanes as a Test of the Rigidity of the Bicyclic Skeleton. Photo-oxidation of [2.2.2] Hericene and 2,3,5,6-Tetramethylidenebicyclo[2.2.n]alkanesInteraction between non-conjugated chromophores, Part 24. Part 23, see [1a]. For a preliminary report, see communication No. ONII-10, Autumn Meeting of the Swiss Chemical Society, Bern, Oct. 18, 1985. (1986)

Birbaum, Jean-Luc ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 761-772

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Keywords: Chemistry ; Organic Chemistry

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Notes: The photo-oxidation of [2.2.2]hericene (6) gave successively the endoperoxides 11 (9,10,11,12-tetramethylidene-4,5-dioxatricyclo[6.2.2.02,7]dodec-2(7)-ene), the bis-endoperoxide 16 (15,16-dimethylidene-4,5,11,12-tetraoxatetracyclo[6.6.2.02,7.o9,14]hexadeca-2(7),9(14)-diene), and the tris-endoperoxide 19 (4,5,11,12,17,18-hexaoxapentacyclo[6.6.6.02,7.09,14.015,20]icosa-2(7),9(14),15(20)-triene). The endoperoxides 11, 16, and 19 were formed in the presence or in the absence of a dye sensitizer. The sensitized photo-oxidations of 2,3,5,6-tetramethylidenebicyclo[2.2.2]octane (4), 5,6,7,8-tetramethylidenebicyclo[2.2.2]oct-2-ene (5), 2,3,5,6-tetramethylidenebicyclo[2.2.1]-heptane (7), and 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptane (8) gave successively the corresponding mono-endoperoxides 9, 10, 12, and 13 and the bis-endoperoxides 14, 15, 17, and 18, respectively. Low-temperature NMR spectra of the bis-endoperoxides 14 and 16 indicated that their C2 and Cs conformers have the same stability. Similarly, there was no difference in the enthalpy of the D3 and C2 conformers of the tris-endoperoxide 19. The following reactivity sequence was observed for the sensitized photo-oxidations of 6-8 and 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene (23): 6 + 1O2→11 〉 7 + 1O2→12〉8 + 1O2→13〉23 + 1O2→24, a trend parallel with that reported for the ethylenetetracarbonitrile (TCNE) cycloadditions to the same polyenes. The rate-constant ratios k1/k2 and k2/k3 for the three successive photo-oxidations of [2.2.2]hericene (6) did not differ significantly from unity, in contrast with the Diels-Alder additions of 6. Similarly, the rate-constant ratios k1/k2 for the two successive photo-oxidations of tetraenes 7 and 8 were significantly smaller than those reported for the successive TCNE cycloadditions to 7 to 8. The endoperoxide formations are not sensitive to the change in the exothermicity of the reactions but they are sensitive to the electronic properties (IP's) of the polyenes.

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Ion-Molecule reaction in the gas phase part VIFor Part V, see [1]. Regioselective SN2 reaction from terpenoid diastereoisomeric diols using CI/NH4+Dedicated to Prof. Tino Gäumann on the occasion of his 60th birthday (1986)

Tabet, Jean-Claude ; Prevost, Chantal ; Bouillot, Anne ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 806-815

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Keywords: Chemistry ; Organic Chemistry

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Topics: Chemistry and Pharmacology

Notes: A stereospecific and regioselective SN2 mechanism (Walden inversion) is observed during studies involving modified terpenoid epimeric diols in a high-pressure ion source using ammonia as a reagent gas.

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Three Novel Spin-Labeled Substrates for Enzymatic Incorporation into Nucleic Acid Lattices (1986)

Toppin, Charles R. ; Pauly, Gary T. ; Devanesan, Prabu ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 345-349

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: The synthesis of one C(4)-spin-labeled uridine-5′-diphosphate (C(4)-UDP) and two nitroxide-containing 2′-deoxyuridine-5′-triphosphate (dUTP) analogs are reported. The C(4)-UDP derivative was incorporated into copolymers by polynucleotide phosphoxylase (PNPase); one of the two dUTP analogs, substituted at position C(4), was a good substrate for TdT, whereas the other one, substituted at position C(5), served as substrate for E. coli DNA polymerase (Pol I).

Additional Material: 1 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19860690213

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Reaktionen von 3-substituiertem 5-Trifluormethyl-1,3,4-oxadiazol-2(3H)-on mit NucleophilenIX. Mitt. über Synthese von Heterocyclen. VIII. Mitt. s. [1].Vorgetragen an der Herbstversammlung der Schweizerischen Chemischen Gesellschaft am 18. Oktober 1985 in Bern. (1986)

Kristinsson, Haukur ; Winkler, Tammo ; Mollenkopf, Max

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 333-339

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Notes: Reactions of 3-Substituted 5-Trifluoromethyl-1,3,4-oxadiazol-2(3H)-one with NucleophilesThe 3-substituted 5-trifluoromethyl-1,3,4-oxadiazolones 3, 4, 13, and 15 are attacked by N- and S-nucleophiles either at the ring C-atom C(2) or C(5). Depending on the nature of the substituent and the nucleophile, the ring-opening products 7, 10, 12, and 14 or the ring-enlargement products 16 are formed. The reaction of 4 with thiols is a novel variant of the Grob-type fragmentation. The reactivity of the 1,3,4-oxadiazolones is compared with that of the analogous 1,3,4-thiadiazolones. The structures of the new compounds were elucidated by 1H- and 13C-NMR spectroscopy.

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URL: http://dx.doi.org/10.1002/hlca.19860690211

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Synthese von 4,4-disubstituierten 1,3-Thiazol-5(4H)-thionen (1986)

Jenny, Christjohanes ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 374-388

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Synthesis of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thionesAn easy synthesis for the 1,3-thiazol-5(4H)-thiones 5, a class of heterocycles which have hitherto only been available with difficulty, is described. Reaction of 3-amino-2H-azirines 25 with thiocarboxylic acids at 0° yields monothiodiamides of type 20 (Scheme 6) which, on treatment with Lawesson reagent at 100°, undergo thiation and cyclization to give 5 in good yield.

Additional Material: 3 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19860690217

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Herstellung von disubstituierten Maleinsäure-anhydriden mit Hilfe von reaktiven 2-Oxo-3H-imidazo[1,2-a]pyridinium-Verbindungen (1986)

Baumann, Marcus E. ; Bosshard, Hans ; Breitenstein, Werner ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 396-403

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Notes: Preparation of Disubstituted Maleic Anhydrides from Reactive 2-Oxo-3H-imidazo[1,2-a]pyridinium CompoundsA new useful method for the preparation of disubstituted maleic anhydrides, most of them bearing additional functional groups in the side chain, is described. The key step of the synthesis consists of the addition of 2-oxo-3H-imidazo[1,2-a]pyridinium compounds to a variety of different Michael acceptors.

Additional Material: 1 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19860690219

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Konfigurationsbestimmung von geometrischen Isomeren mittels selektiver 13C{1H}-NOE-Differenzspektroskopie (1986)

Neidlein, Richard ; Kramer, Walter ; Ullrich, Volker

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 898-904

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Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Application of Selective 13C{1H}-NOE Difference Spectroscopy in Determination of the Configuration of (Z)/(E)-IsomersHeteronuclear 13C{1H}-NOE studies have been performed to elucidate the configuration at the imino double bond in N,N′-Dicyanoquinonediimines. Selective low-power irradiation of the neighbouring ring protons in compounds 1-5 increases the signal intensities of CN as well as of the imino-C-atoms in the 13C-NMR spectra. The increase of signal intensity can easily be detected by the difference spectroscopy. The results of this investigation are in good agreement with a recently published study on the stereochemistry of N,N′-Dicyanoquinonediimines, based on the interpretation of 13C-chemical shifts.

Additional Material: 4 Ill.

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Synthese und Strukturaufklärung von Merucathin und Pseudomerucathin. Zwei Inhaltstoffe von Catha edulis FORSK (1986)

Wolf, Jean-Pierre ; Pfander, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 918-926

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Synthesis and Structure Elucidation of Merucathine and Pseudomerucathine. Two Constituents of Catha edulis FORSK.Starting from L-alanine, two constituents of Catha edulis FORSK. (3R,4S)-4-amino-1-phenyl-1-penten-3-ol ((3R,4S)-4, merucathine) and (3S,4S)-4-amino-1-phenyl-1-penten-3-ol ((3S,4S)-4, pseudomerucathine) were synthesized.

Additional Material: 4 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19860690420

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Mitteilungen (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 955-956

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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.19860690424

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1,4-Dithiafulvene aus der Umsetzung von 4,4-disubstituierten 1,3-Thiazol-5(4H)-thionen mit AcetylenderivatenVorläufige Mitteilung s. [1]. (1986)

Jenny, Christjohannes ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 419-429

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Notes: 1,4-Dithiafulvenes, Products of the Reaction of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thiones and Acetylenic CompoundsOn heating in toluene, 4,4-disubstituted 1,3-thiazol-5(4H)-thiones 1 and acetylenecarboxylates or acetylenecarbonitriles 2 undergo a cyclosubstitution reaction to yield 2-methylidene-1,3-dithiol derivatives 3 (1,4-dithiafulvenes) and a nitrile. Further heating of 3a and 3b in the presence of excess 2a leads to the isomeric 2,3-dihydrothiophene-2-thiones 4a and 4b, respectively. The benzodithiafulvene 14 has been formed in a similar reaction from 1a and in situ generate benzyne.

Additional Material: 2 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19860690223

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Perimeter-Type Structures in Charged [4n + 2] Annuleno [4n + 2] annulenes. The Importance of the Frontier-Orbitals (1986)

Huber, Walter ; Müllen, Klaus ; Schnieders, Christoph ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 949-954

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Notes: The tetra(tert-butyl)[14]annuleno[14]annulene 1 is transformed, via alkali metal reduction, into its radical monoanion, dianion, radical trianion, and tetraanion. The paramagnetic species are characterized by ESR and ENDOR spectroscopy and the diamagnetic species by 1H- and 13C-NMR spectroscopy. Well-resolved ESR and NMR spectra can only be obtained, if the reduction is carefully monitored. For the interpretation of the data, the ions derived from the structurally related [14]- and [22]annulenes 3 and 5 as well from the tetra(tert-butyl)[14]annuleno[18]annulene 2 serve as suitable model compounds. While the behavior of the neutral annulenoannulene 1 is governed by that of the [14]annulene-subunit, the corresponding ionic systems can best be described as macrocyclic perimeters. This outcome can be rationalized by the nodal properties of the frontier MO's.

Additional Material: 2 Ill.

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URL: http://dx.doi.org/10.1002/hlca.19860690423

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Stereoselective Reduction of δ-Hydroxy-β-ketoesters (1986)

Kathawala, Faizulla G. ; Prager, Bernhard ; Prasad, Kapa ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 803-805

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Keywords: Chemistry ; Organic Chemistry

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Notes: The reduction of δ-hydroxy-β-ketoesters 1 was investigated with three different reducing agents. In several instances, high selectivity in favor of syn-1,3-diols was observed.

Additional Material: 2 Tab.

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URL: http://dx.doi.org/10.1002/hlca.19860690407

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Anion Selectivity of Metalloporphyrins in Membranes (1986)

Ammann, Daniel ; Huser, Marin ; Kräutler, Bernhard ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 849-854

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Notes: Lipophilic Co(III) and Mn(III) complexes of 5,10,15,20-tetrakis[4-(hexyloxycarbonyl)phenyl]porphyrin act as positively charged carriers for anions and induce anion selectivities in membranes clearly deviating from the sequence of classical anion exchangers. Different anion selectivities are observed for the Co(III) and Mn(III) porphyrins.

Additional Material: 1 Ill.

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Approaches to 1H-Cyclopropa[l]phenanthrenes. Eliminations with 1a,9b-Dihydro-1H-cyclopropa[l]phenanthrene Derivatives (1986)

Müller, Paul ; Thi, Huong Can Nguyen ; Pfyffer, Jean

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 855-864

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Keywords: Chemistry ; Organic Chemistry

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Notes: Base-induced elimination of the sulfonium salt 2i in the presence of furan affords the addition products 7 and 8, derived from 1H-cyclopropa[l]phenanthrene (1) and the isomeric cyclopropene 5a (Scheme 3). Upon oxidation, the selenide 2c yields phenanthrene-9-methanol (9), presumably via 1. No evidence for the intermediate 1 is obtained from sulfoxide pyrolysis with 2e, which leads to products formed by radical pathways (Scheme 5). Reductive elimination of the disulfone 3b gives half-reduction to monosulfone 2g and complete reduction to cyclopropane 2 as well as 9-methylphenanthrene (15), but no evidence for the intermediate 1.

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URL: http://dx.doi.org/10.1002/hlca.19860690412

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Fluorine-Containing Organozinc Reagents Part 1 A Simple Synthesis of 2,2-Dichloro-3,3,3-trifluoropropanol (1986)

Lang, Robert Werner

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 881-886

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Notes: The title compound 1, which can be regarded as a synthetic equivalent of substituted 1,1,1-trifluoroacetone 2, is prepared by Zn-induced reductive addition of 1,1,1-trichloro-2,2,2-trifluoroethane (3) to formaldehyde (4). A brief survey of the scope of this C—C-bond formation leading to a variety of new CF3-containing synthetic building blocks is also given.

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Intramolekulare 1,3-dipolare Cycloadditionen mit alkenyl-substituierten 3,4-DiarylsydnonenTeilweise in vorläufigen Mitteilungen veröffentlicht [1] [2].Als Sydnone werden mesoionische 1,2,3-Oxadiazol-5-one (1,2,3-Oxadiazolium-5-olate, Anhydro-5-hydroxy-1,2,3-oxadiazolium-hydroxide) bezeichnet [3]. (1986)

Meier, Hansruedi ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 927-940

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Notes: Intramolecular 1,3-Dipolar Cycloaddition Reactions of Alkenyl-substituted 3,4-DiarylsydnonesThe 3,4-diarylsydnones 1 and 12a-e with an allyl or alkenyloxy substituent on the N(3)-phenyl group have been synthesized by classical methods starting from 2-allylaniline and the corresponding alkenyloxyanilines, respectively (Schemes 2 and 3). Whereas the allyl-substituted sydnone 1 undergoes an intramolecular 1,3-dipolar cycloaddition at room temperature in solution to yield 13 (Scheme 4), the alkenyloxy-substituted sydnones 12a-e are thermally stable. On irradiation of 1 and 12a-d, formation of the fused dihydropyrazoles 2 and 14a-d (Schemes 1 and 5) is observed. In the case of 12d, the yield of 14d is very low, and the symmetric 1,2,3-triazole 15a has been isolated as the main product. A very likely reaction mechanism for the formation of the photoproducts involves decarboxylation of the sydnones to give a nitrile-imine which undergoes an intramolecular 1,3-dipolar cycloaddition onto the C=C bond.

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Intramolecular Oxygen Transfer on the Ozonolysis of a Diphenylcyclopentene Derivative (1986)

Jefford, Charles W. ; Boukouvalas, John ; Jaggi, Danielle ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 941-948

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Notes: The ozonolysis of cis-3,4a,7,7a-tetrahydro-3,3-dimethyl-6,7a-diphenylcyclopenta[1,2,4]trioxine (1) in CH2Cl2 at -78° gave the secondary endo ozonide 2 (43% yield) and an acetal 3 (27% yield) derived from O-insertion at the ortho position of the C(7a) phenyl substituent. Both structures were elucidated by X-ray. Repetition of the ozonolysis in MeOH/CH2Cl220:3 at -78° also gave the same two products in 12 and 15% yields, repectively, together with the hemiperacetal 4 (54% yield) formally derived from the secondary ozonide by addition of MeOH.

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Masthead (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986)

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Isoswerosid, ein neues Secoiridoidglycosid aus den Wurzeln des Zwergholunders Sambucus ebulus L. (Caprifoliaceae). 2. Mitteilung über die Inhaltsstoffe der Zwergholunderwurzel (1986)

Gross, Gian-Andrea ; Sticher, Otto

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1113-1119

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Notes: Isosweroside, a New Secoiridoid Glycoside from the Roots of Sambucus ebulus L. (Caprifoliaceae)The paper describes the isolation and structure elucidation of isosweroside (6-(β-D- glucopyranosyloxy)-methyl-9-vinyl-2,8-dioxabicyclo[3.3.1]non-6-en-3-one), the first Valeriana-type secoiridoid glycoside from the roots of Sambucus ebulus L. along with the two known glycosides ebuloside and morroniside.

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Synthèse d'acétals de désoxy-3-hydroxyamino-3-furannoses. Note de laboratoire (1986)

Tronchet, Jean M. J. ; Habashi, Ford ; Fasel, Jean-Pierre ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1132-1136

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Notes: Synthesis of 3-Deoxy-3-(hydroxyamino)furanose AcetalsReduction of sugar ketoximes with NaBH3CN under acidic conditions constitutes a good synthetic pathway to deoxy(hydroxyamino)sugar derivatives. These compounds which are useful building blocks for the preparation of analogs of various classes of biologically important carbohydrates are reasonably stable.

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1,3-Dioxanone Derivatives from β-Hydroxy-carboxylic Acids and Pivalaldehyde. Versatile Building Blocks for Syntheses of Enantiomerically Pure Compounds. A Chiral Acetoacetic Acid Derivative Preliminary Communication (1986)

Seebach, Dieter ; Zimmermann, Jürg

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1147-1152

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Notes: (R)-3-Hydroxybutyric acid (from the biopolymer PHB) and pivalaldehyde give the crystalline cis - or (R,R)-2-(tert-butyl)-6-methyl-1,3-dioxan-4-one (1a), the enolate of which is stable at low temperature in THF solution and can be alkylated diastereoselectively (→3, 4, 5, and 7). Phenylselenation and subsequent elimination give an enantiomerically pure enol acetal 10 of aceto-acetic acid. Some reactions of 10 have been carried out, such as Michael addition (→11), alkylation on the CH3 substituent (→13), hydrogenation of the C=C bond (→1a) and photochemical cycloaddition (→16). The overall reactions are substitutions on the one stereogenic center of the starting β-hydroxy acid without racemization and without using a chiral auxiliary.

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Diastereoselectivity and Reactivity in the Diels-Alder Reactions of α-Chloronitroso Ethers (1986)

Felber, Helena ; Kresze, Günther ; Prewo, Roland ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1137-1146

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Notes: The structure of the α-chloronitroso ether 1, obtained from the hydroximolactone 2 and tert-butyl hypochlorite (89%), was established by X-ray crystallographic analysis. The [4 + 2] cycloadditions of 1 with the dienes 3 and 8-11 led to the N-unsubstituted 3,6-dihydro-2H-1,2-oxazines 6 and 12-16 in high enantiomeric excess (Table 1). Due to the additional α-alkoxy group, the reactivity of 2 is much superior to the one of known α-chloronitrosoalkanes. The reactive conformation of 1 was deduced from the X-ray analysis as well as the high diastereoselectivity of the cycloadditions. The importance of the α-alkoxy group was evidenced from the similar reactivity of the racemic α-chloronitroso ethers 25-27 which were prepared from the hydroximo ethers 28-30 and tert-butyl hypochlorite.

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Desoxy-nitrozucker 14. Mitteilung13. Mitteilung: [1]. 1-C-Nitroglycale. Herstellung und Umsetzung mit einigen Stickstoff-Nucleophilen (1986)

Baumberger, Franz ; Beer, Dieter ; Christen, Markus ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1191-1204

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Notes: 1-C-Nitroglycals. Preparation and Reaction with Some Nitrogen NucleophilesAcetylation of the 1-deoxy-1-nitromannopyranoses 2 and 6 was accompagnied by spontanous β-elimination to give the 1-C-nitroglucals 3 and 7, respectively, while acetylation of the gluco- and galacto-configurated 1-deoxy-1-nitropyranoses 8 and 14 gave the acetates 9 and 15, respectively (Scheme 1). The acetylation of the ribo- and arabino-configurated 1-deoxy-1-nitrofuranoses 19 and 21 also occurred without β-elimination to give the acetates 20 and 22, respectively (Scheme 2). Mild base treatment of the previously described O-acetylnitro-β-D-glucose 4, the O-acetylnitro-β-D-pyranoses 9 and 15, and the O-acetylnitro-β-D-furanoses 17, 20, and 22 gave the 1-C-nitroglycals 3, 10, 16, 18 and 23, respectively (Scheme 1 and 2). The previously obtained 1-C-nitroglucal 3 was deacetylated by treatment with MeOH in the presence of KCN or sodium m-nitrophenolate to give the free nitroglucal 5. Deacetylation of the benzylidene protected 1-C-nitroglucal 10 (MeOH, NaOMe) gave the 4,6-O-benzylidene-1-C-nitroglucal 11 and traces of the 2-O-methyl-1-C-nitromannoses 12 and 13. The UV, IR, 1H-NMR and 13C-NMR spectra of the 1-C-nitroglycals are discussed. In solution, the 1-C-nitroglycals 1, 5, 7, 10, 11, and 16 adopt approximately a 4H5- and 3 a flattened 4H5 conformation. The structure of 5 was established by X-ray analysis. In the solid state, 5 adopts a sofa conformation, which is stabilized by an intramolecular H-bond. The β-addition of NH3 to the 1-C-nitroglucals 7 and 10 was followed by an O→ N acetyl migration to give exclusively anomeric pairs of the N-acetyl-1-nitromannosamine derivatives 24/25 and 26/27, respectively (Scheme 3). The β-addition of methylamine, octadecylamine, and tryptamine to the 1-C-nitroglucal 11 also stereoelectronically controlled and gave the crystalline N-alkyl-1-nitromannosamines 28, 29, and 30, respectively. The stereoelectronically controlled β-addition of NH3 to the 1-C-nitrogalactal 16, followed by acetylation, yielded exclusively the talosamine derivative 31, while the reversible β-addition of azide ions to 16 gave the anomeric 2-azido-1-nitrogalactoses 32 and 33. The β-addition of azide ions to the 1-C-nitroglucal 1 led to the 2-azido-1-nitromannose 34. In the presence of excess formaldehyde, this addition was followed by a Henry reaction. Chromatography of the crude product was accompagnied by solvolytic removal of the NO2 group to give the 3-azidomannoheptulose 35 in high yields (Scheme 4).

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Comparison of the Complexation of Open-Chain and Cyclic N2S2 Ligands with Cu+ and Cu2+ (1986)

Kaden, Thomas A. ; Kaderli, Susanne ; Sager, Wiebke ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1216-1223

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Notes: The complexation properties of the open-chain N2S2 ligands 1-4 are described and compared to those of analogous N2S2 macrocycles 5-7. With Cu2+, the open-chain ligands give complexes with the stoichiometry CuL2+ and CuLOH+, the stabilities and absorption spectra of which have been determined. The ligand field exerted by these ligands is relatively constant and independent of the length of the chain. With Cu+, the species CuLH23+, CuLH2+, and CuL+ were identified and their stabilities measured. The redox potentials calculated from the equilibrium constants and measured by cyclic voltammetry agree and lie between 250 and 280 mV against SHE. The comparison between open-chain and cyclic ligands shows that (1) a macrocyclic effect is found for Cu2+ but not for Cu+, (2) the ligand-field strength is very different for the two types of ligands, and (3) the redox potentials span a larger interval for the macrocyclic than for the open-chain complexes.

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Nucleotides. Part XXVPart XXIV: [1].. Chemical synthesis of the hexaribonucleotide C-A-A-C-C-A (1986)

Lchiba, Misuzu ; Charubala, Ramamurthy ; Varma, Rajendra S. ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1768-1777

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Notes: The chemical synthesis of the ribo-hexamer C-A-A-C-C-A has been achieved by two different routes applying the phosphotriester approach and using the (p-nitrophenyl)ethyl group for phosphate protection. The 2′-hydroxy groups as well as the terminal 2′,3′-diol function have been blocked by the (tert-butyl) dimethylsilyl group as permanent protection throughout all the synthetic steps with great success. Final deblocking of all protective groups could be performed with 80% yield to give the hexamer 23. The various protected intermediates have been characterized by elemental analysis and UV spectra.

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Errata (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1787-1787

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URL: http://dx.doi.org/10.1002/hlca.19860690736

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The Formation of Bridged Bicyclic 1,2,4-Trioxanes by Intramolecular Capture of β-Hydroperoxy Cations (1986)

Jefford, Charles W. ; Favarger, France ; Ferro, Serenella ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1778-1786

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Notes: The 1,4-endoperoxide, prepared from 3-(4-methylnaphth-1-yl)propanal by photo-oxygenation in CH2Cl2, gave on treatment with Amberlyst-15®, 3,10b-epidioxy-2,3,4a,10b-tetrahydro-6-methyl-1H-naphtho[2,1-b] pyran in 85% yield. Its structure was determined by X-ray crystal structure analysis. The 1,2,4-trioxane moiety is locked in a twist-boat conformation with trans fusion to the parent six-membered ring. The 1,4-endoperoxides of the methyl, butyl, and phenyl ketone analogues of the aforementioned aldehyde underwent similar acid-catalyzed rearrangement to the corresponding bridged bicyclic trioxanes in 94, 47, and 48% yields, respectively.

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New Synthetic Routes to β-Olefinic Trialkoxyphosphonium Salts and Phosphonates: Organometallic Variants of the Michaelis-Arbuzov ReactionReactions with Metal-Coordinated Olefins, Part V. Part IV: see [1]. Presented in part at the XIIth International Conference on Organometallic Chemistry, Vienna, September 1985. (1986)

Hafner, Andreas ; Von Philipsborn, Wolfgang ; Salzer, Albrecht

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1757-1767

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Notes: The low-temperature addition of tertiary phosphites to [(allyl)Fe (CO)4]+X- complexes proceeds regio- and stereospecifically and produces metal-coordinated β-olefinic trialkoxyphosphonium ions. These can be converted by various routes into the uncomplexed phosphonium salts or phosphonates. Similar reactions of acyclic [(dienyl)Fe(CO)3]+X- compounds give metal-coordinated (2,4-dien-1-yl)trialkoxyphosphonium salts or dialkyl (2,4-dien-1-yl)phosphonates. The mechanisms and their relationship to the classical Michaelis-Arbuzov reaction are discussed. The new compounds are characterized, if possible, by 1H-, 13C-, and 31P-NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig-Horner reactions, are difficult to obtain by conventional routes.

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Mitteilungen (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1788-1789

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URL: http://dx.doi.org/10.1002/hlca.19860690737

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Masthead (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986)

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URL: http://dx.doi.org/10.1002/hlca.19860690801

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Membrane Structure of Substance P. I. Prediction of Preferred Conformation, Orientation, and Accumulation of Substance P on Lipid MembranesPeptide nomenclature and abbreviations, see IUPAC-IUB JBCN Recommendations 1983 on ‘Nomenclature and Symbolism for Amino Acids and Peptides’ [1a]. (1986)

Schwyzer, Robert ; Erne, Daniel ; Rolka, Krzysztof

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1789-1797

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Notes: Preferred conformation, orientation, and accumulation of substance P on a neutral hydrophilic-hydrophobic interface was estimated and extrapolated to interactions with neutral and anionic lipid bilayer membranes according to our general procedure. Nine residues at the C-terminus were predicted to be transferred to the hydrophobic phase as an α-helical domain, oriented quite perpendicularly on the membrane surface. The N-terminal residues remained in the aqueous phase with their charges exposed to H2O. The molecular amphiphilic moment vector was strong (338 arbitrary units) and pointed its hydrophilic end towards the N-terminus, only 15° away from the helix axis. The molecular electric dipole moment vector was also strong (124 debye) and pointed its positive end towards the N-terminus, only 9° away from the helix axis. Thus, it reinforced the effect of the amphiphilic moment of a peptide intruding into the membrane dipole layer. The estimated dissociation constant for the equilibrium between membrane-bound and free substance P was Kd ≍ 46 mM for neutral membranes, and Kd ≍0.43 mM for anionic membranes with a Gouy-Chapman surface potential of -40 mV. Thus, substance P behaved similarly to dynorphin A and adrenocorticotropin peptides which insert their N-terminal message segments as perpendicularly oriented helical domains into membranes, whereas their C-terminal address segments remain in the aqueous phase as random coils. Substance P is the first instance of a neuropeptide which is expected to insert a C-terminal message into lipid membranes.

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Membrane Structure of Substance P. II. Secondary Structure of Substance P, [9-Leucine]substance P, and Shorter Segments in 2,2,2-Trifluoroethanol, Methanol, and on Liposomes Studied by Circular DichroismPeptide nomenclature and abbreviations, see IUPAC-IUB JBCN Recommendations 1983 on ‘Nomenclature and Symbolism for Amino Acids and Peptides’ [1a] and Table 1. Amino-acid residues are in their L-configuration unless explicitly stated otherwise. Random coil means nonregular, nonrepeating sequences of backbone dihedral angles with or without equilibria between various random coil conformers. PC = phosphatidyl-choline; DOPC = dioleoyl-sn-glycero-3-phosphocholine; PS = phosphatidylserine (brain). (1986)

Rolka, Krzysztof ; Erne, Daniel ; Schwyzer, Robert

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1798-1806

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Notes: Comparative CD studies with substance P (1), [Leu9]substance P ([Leu9]-1), and their shorter peptide segments supported the membrane structures predicted for substance P and [Leu9]substance P. They indicated that the C-terminal segments (from residue 3 or 4 onward) can adopt α-helical conformations in hydrophobic environments and on lipid membranes. The N-terminal segment, (residues 1-4) had a poly(proline)-like conformation in aqueous and hydrophobic surroundings. Residues 3 and 4 (Lys-Pro) appeared to belong to both domains and bring about the transition between the two. The estimated free energies of transfer for 1 and [Leu9]-1 from their random conformations in H2O to their partially helical conformations on an aqueous-hydrophobic interface are too small to allow detectable interaction with neutral lipid membranes at low concentrations. The two peptides should, however, interact detectably with anionic membranes because of favourable Boltzmann distribution factors. This prediction was shown to be correct for liposomes prepared from 1,2-dioleoyl-sn-glycero-3-phosphocholine (neutral) and phosphatidylserine (anionic).

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Membrane Structure of Substance P. III. Secondary Structure of Substance P in 2,2,2-Trifluoroethanol, Methanol, and on Flat Lipid Membranes Studied by Infrared SpectroscopyPeptide nomenclature and abbreviations, see IUPAC-IUB JBCN Recommendations 1983 on ‘Nomenclature and Symbolism for Amino Acids and Peptides’ [la] and Table 1. Amino-acid residues are in their L-configuration unless explicitly stated otherwise. Random coil means nonregular, nonrepeating sequences of backbone dihedral angles with or without equilibria between various random-coil conformers. IR-ATR = infrared attenuated total reflection spectroscopy. POPC = 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. (1986)

Erne, Daniel ; Rolka, Krzysztof ; Schwyzer, Robert

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1807-1816

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Notes: IR data of the neuropeptide substance P (1) and its synthetic segments des-(Arg1-Gln6)-substance P (6), des-(Arg1-Pro4)-substance P (4), des-(Arg1-Lys3)-substance P (3), and des-Arg1-substance P (2) indicate predominant β-structures in the solid state and α-helical structures in CF3CH2OH (amide I band shape analysis). In MeOH, the spectra of 1 suggest a partly helical structure. On membranes prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, a C-terminal α-helix consisting of 8 or 9 peptide bonds appears to be induced (IR attenuated total reflection studies). Its perpendicular orientation on the membrane is suggested by the dichroic ratios of the amide-I and -II bands. This study is consistent with our CD experiments and lends support to the membrane structure of 1 predicted from the estimated amphiphilic moment, hydrophobic-association constant, and helix length.

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Enantioselective Synthesis of β-Necrodol and of 1-Epi-β-necrodol via Asymmetric 1,4-Addition and Magnesium-Ene Cyclization. Preliminary Communication (1986)

Oppolzer, Wolfgang ; Schneider, Philippe

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1817-1820

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Enantiomerically pure β-necrodol (1) and its 1-epimer 16 have been synthesized starting from aldehyde 5. The two key steps are an asymmetric conjugate addtion/Mannich reaction tandem (10→12) and a type-II-magnesiumene cyclization/oxidation sequence (14→1 + 16).

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3,7-Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes (1986)

Metzger, Erich ; Aeschimann, Roland ; Egli, Martin ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1821-1828

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Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

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Notes: Lipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′-tetracyclohexyl-5,5-dimethyl-3,7-dioxaazelaamide) has been prepared, and its structure was elucidated by X-ray analysis.

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Stoffwechselprodukte von Mikroorganismen. 237. Mitteilung236. Mitt.: [1]. (2S, 3R, 4R, 6R)-2,3,4-Trihydroxy-6-methylcyclohexanon aus zwei Actinomyceten-Stämmen (1986)

Müller, André ; Keller-Schierlein, Walter ; Bielecki, Jacek ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1829-1832

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Notes: (2S, 3R, 4R, 6R)-2,3,4-Trihydroxy-6-methylcyclohexanone from Two Strains of ActinomycetesA tetrazolium-blue positive compound was isolated from two strains of acinomycetes. Its constitution and relative configuration 1 were determined by spectroscopic methods, and the absolute configuration by degradation to (+)-(R)-methylsuccinic acid.

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Stoffwechselprodukte von mikroorganismen. 238. Mitteilung237. Mitt.: [1].. Isolierung und Strukturaufklärung von Differolid (1986)

Keller-Schierlein, Walter ; Bahnmüller, Urs ; Dobler, Max ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1833-1836

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Notes: Isolation and Structure Elucidation of DifferolideFrom cultures of a new actinomycete, Streptomyces aurantiogriseus (PREOBRAZHENSKAYA 1975), strain Tü 3149, a compound C12H12O4 was isolated, which enhances the formation of aerial mycelium and spores of Streptomyces glaucescens. The structure determined by X-ray diffraction studies was that of racemic dilactone 1 ((±)-differolide).

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Carbophile Additionen von Organocupraten mit 1,3-Thiazol-5(4H)-thionen (1986)

Jenny, Christjohannes ; Wipf, Peter ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1837-1843

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Notes: Carbophilic Additions of Organocuprates and 1,3-Thiazole-5(4H)-thionesOrganocuprates and 1,3-thiazole-5(4H)-thiones 1 react in THF at 0° via carbophilic addition onto the C—S bond to give 4,5-dihydro-1,3-thiazole-5-thiols 3 (Scheme 3). This observation is in marked contrast to the previously described reaction of organolithium compounds and 1, which undergo a thiophilic addition onto the exocyclic S-atom. As an exception, treatment of the 1,3-thiazole-5(4H)-thione 1a with tert-butyl cuprate leads to 7a (Scheme 3).

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Synthesis of 3β-Hydroxy[21-14C]-5β-pregn-8(14)-en-20-one from Chenodeoxycholic Acid (1986)

Deluca, MóNica E. ; Seldes, Alicia M. ; Gros, Eduardo G.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1844-1850

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Notes: 3β-Hydroxy[21-14C]5β-pregn-8(14)-en-20-one (17) was prepared from chenodeoxycholic acid (1a). The synthetic sequence involved: (i) degradation of the bile-acid side chain to an etianic acid; (ii) formation of the 8(14)-double bond; (iii) inversion of the configuration at C(3); (iv) construction of the acetyl side chain at C(17) with the required isotopic label at C(21). Structures of all described products were confirmed by chemical and spectroscopic (IR, 1H-NMR, 13C-NMR, MS) methods.

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Neue 1,6-Methano[10]annulen-Derivate durch Umlagerungsreaktionen der Trimethylsilyl-Gruppe (1986)

Neidlein, Richard ; Wirth, Wolfgang

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1851-1854

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Notes: New Derivatives of 1,6-Methano[10]annulene by Rearrangement of Trimethylsilyl GroupsOxidation of derivatives of trimethylsilyl-substituted bicyclo[4.4.1]undeca-1,3,5,7-tetraenes 1-3 leads to 1,6-methano[10]annulenes. In the case of 2 and 3a, rearrangement of the trimethylsilyl group takes place. This rearrangement can be used to prepare 2,9-disubstituted 1,6-methano[10]annulenes.

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Highly Stereoselective Photochemical Oxidative Addition Reactions. Preliminary Communication (1986)

Chassot, Laurent ; von Zelewsky, Alex

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1855-1857

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Notes: Cyclometallated complexes of the type cis-bis(2-phenylpyridine)platinum(II) (C22H16N2Pt) and cis-bis(2-(2′-thienyl)pyridine)platinum(II) (C18H12N2S2Pt) undergo thermal or photochemical oxidative addition (TOA or POA) reactions with a number of substrates. TOA (with CH3I, CH3CH2I etc.) yield mixtures of several isomers which rearrange slowly (within ca. one week at room temperature) to one of the possible cis-isomers. CH2Cl2, CHCl3, or (E)—ClCH=CHCl, e.g., do not react thermally. POA yield directly complexes of Pt(IV) with the halide and a σ-bonded C-atom in cis-position. The configuration, as assigned by extensive use of 1H-NMR data, can be characterized for the two chelating ligands C … N and C′ … N′ by C,C′-cis; N,N′-cis and C(chelate), Cl-trans.

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Conformationally Restricted Analogs of Platelet-Activating Factor (PAF) (1986)

Hadváry, Paul ; Weller, Thomas

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1862-1871

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Notes: The synthesis of the five-membered cyclic phosphorodiamidic-acid derivatives 10 and 11 as well as the preparation of the six-membered cyclic phosphates 18, 19, 22-25, and phosphoramidates 27-32 is described. The effects of these conformationally restricted platelet-activating factor analogs on rabbit platelet aggregation are briefly discussed. The 2-oxo-1,3,2-dioxaphosphorinanes 19, 25, and 30 were found to be equally potent platelet-activating factor antagonists as the known thiazolium salt 33.

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Metaboliten der 1,5-Dihydroimidazo[2,1-b]chinazolin-2(3H)-one. Synthese und Reaktionen einiger 1,5-Dihydro-3-hydroxyimidazo[2,1-b]chinazolin-2(3H)-one (1986)

Stalder, Henri

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1887-1897

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Notes: Metabolites of 1,5-Dihydroimidazo[2,1-b ]quinazolin-2(3H)-ones. Preparation and Reactions of Some 1,5-Dihydro-3-hydroxyimidazo[2,1-b]quinazolin-2(3H)-onesHydroxylated 1,5-dihydroimidazo[2,1-b]quinazolin-2(3H)-ones 2-4 and 6 were isolated as metabolites of imidazoquinazolinones 1a and 1b, respectively. The synthesis of 1,5-dihydro-3-hydroxy-3-methylimidazo[2,1-b]quinazolin-2(3H)-ones 3, 4, and 6, and the preparation of some derivatives thereof is described.

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[2 + 2] cycloaddition of optically active ketenes. Synthesis of (-)-blastmycinonePresented at the ‘Swiss Chemical Society Meeting’ in Bern, October 1982, at the University of Basel. February 1983 and at the ‘XIth Conference on Isoprenoids’ in Poland, 1985.. Preliminary Communication (1986)

Fráter, Georg ; Müller, Urs ; Günther, Wulf

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 1858-1861

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Notes: [2 + 2] Cycloaddition of (menthyloxy)methylketene (2) to cis-ethyl propenyl ether showed a ca. 3:1 diastereo-selectivity. A two-step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)-compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis- benzyl 1-hexenyl ether (9) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (-)-blastmycinone. Accordingly, the preferred transition state has been deduced as 15.

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Kombinierte NOE- und Entkopplungsexperimente zur selektiven H-NMR-Detektion: Anwendung auf ein stereochemisches Problem (1986)

Bigler, Peter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2062-2066

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Keywords: Chemistry ; Organic Chemistry

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Notes: Combined NOE and Decoupling Experiments for the Selective H-NMR Detection: Application to a Stereochemical ProblemThe successful solution of complex stereochemical problems by NMR methods often requires scalar (J) and dipolar (NOE) data. A modern method, improved with respect to sensitivity and selectivity, which yields both scalar and dipolar informations is proposed, and an application to configurational analysis is demonstrated. The method is based on NOE effects for the detection of selected protons and homonuclear decoupling for improved resolution.

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Metal complexes of macrocyclic ligands. Part XXIIIPart XXII: [1].. Synthesis, properties, and structures of mononuclear complexes with 12- and 14-membered tetraazamacrocycle-N,N′,N″,N‴-tetraacetic Acids (1986)

Riesen, Andreas ; Zehnder, Margareta ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2067-2073

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Notes: The two tetraazamacrocycle-N,N′,N″,N‴-tetraacetic acids H4dota and H4teta form with Ni2+, Cu2+, and Zn2+ (M2+) mononuclear complexes MLH2 and M′[ML], M′ being an alkaline earth ion. The structures of Ni(H2dota) and Cu(H2dota) have been solved by X-ray structure analysis. The metal ions are in a distorted octahedral geometry coordinated by four amino N-atoms and two carboxylates. In the case of Cu2+, the distortions are more pronounced than for Ni2+ indicating that the Jahn-Teller effect is operating. Starting from these two structures, the coordination geometry of the other complexes is discussed using VIS and IR spectra.

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Metal complexes of macrocyclic ligands. Part XXIVPart XXIII: [1].. Binuclear complexes with tetraazamacrocycle-N,N′,N″,N‴-tetraacetic acids (1986)

Riesen, Andreas ; Zehnder, Margareta ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2074-2080

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Notes: The three ligands H4dota, H4teta, and H4heta give binuclear complexes with Cu2+ and Ni2+, the spectral properties of which have been studied. The structures of Cu2(dota)·5H2O and Cu2(teta)·6H2O have been established by X-ray diffraction analysis.

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Metal complexes with macrocyclic ligands. Part XXVPart XXIV: [1].. One-step synthesis of mono-N-substituted azamacrocycles with a carboxylic group in the side-chain and their complexes with Cu2+ and Ni2+ (1986)

Studer, Martin ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2081-2086

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Notes: Mono-N-substituted azamacrocycles 2-7, containing a carboxyalkyl or carboxyaryl side-chain, are obtained by reacting a five-fold excess of the macrocycle with 1 equiv. of a suitable halogenocarboxylic acid in alkaline aqueous EtOH. For halogenocarboxylic acids, which easily lactonize under alkaline conditions, a variant with the corresponding ester or nitrile as alkylating agent is also described. The salient point of this synthesis lies in the use of an excess of the macrocycle over the alkylating agent, thus reducing the amount of polyalkylation to a minimum, and in the easy separation of the excess of unreacted educt from the aminocarboxylic acid. These new ligands form Ni2+ and Cu2+ complexes, the spectral properties of which have been studied. In the case of the Cu2+ complexes with ligand 2, 3, and 6, a pH-dependent color change is observed. This is explained with an equilibrium between a species, in which the carboxylate group is bound to the metal, and one, in which it is protonated and non-coordinated. In the case of the Ni2+ complexes with the same ligands, only the species with a coordinated carboxylate was observed. In the Cu2+ and Ni2+ complexes with ligands 4 and 5, however, the carboxylate group does not coordinate at all, because of the length or the special structure of the chain.

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Triaziridine. 6. Mitteilung5. Mitteilung: [1].. Substituententransformationen an TriaziridinenVorgetragen von H.H. an der Versammlung der Schweizerischen Chemischen Gesellschaft vom 10. Oktober 1986 in Bern. (1986)

Hilpert, Hans ; Hoesch, Lienhard ; Dreiding, André S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2087-2097

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Notes: Substituent Transformations on TriaziridinesSeveral novel triaziridines were prepared by substituent transformations starting from the known dialkyl-triaziridine-carboxylates 1a-c, with the aim to study the influence of the substitution pattern on the properties of the triaziridine ring. The dialkyl-triaziridines 2a-c were obtained by (t-BuO-)-mediated demethylation and decarboxylation and the dialkyl-triaziridine-methanols 4a-c by LiAlH4 reduction. Further reduction of the tosylates of 4a, b with LiAlH4 gave the methyl-dialkyl-triaziridines 3a, b. The dialkyl-triaziridines 2a, c could not be N-methylated directly with CH3I, but the anions 10a, c, obtained from 2a, c with CH3Li, yielded 3a, c. N-Methylation of 2a with (CH3)3OBF4 did not afford 3a but rather the methyl-triaziridinium salt 11. The dialkyl-triaziridine 2c has pKa 〉 14, its protonated species 〈 2. A concept that the electron pairs on the triaziridine N-atoms are more strongly localized than on amine N-atoms explains (a) that the dialkyl-triaziridine 2c is hardly basic, (b) that the LiAlH4 reductions of the esters 1 stop at the stage of the methanols 4, and (c) that the methanols 4a, b do not cleave like aminomethanols.

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Norbornanes. Part 18. Inductive Charge Dispersal in the Solvolyses of 4- and 5-Substituted 2-Norbornyl p-Toluenesulfonates (1986)

Fuso, Francesco ; Grob, Cyril A. ; Sawlewicz, Pawel ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2098-2107

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Notes: The solvolysis rates and products of 4- and 5-exo-substituted 2-exo- and 2-endo-norbornyl tosylates 9 and 10, respectively, are reported. The logarithms of the rate constants (log k) correlate linearly with the inductive constants σIq for the substituents. A comparison of the reaction constants p1 for the 4-, 5-, 6-, and 7-substituted 2-exo- and 2-endo-tosylates 9, 10, 1, and 2 respectively, indicates that inductivity is higher for 2-exo-ionization than for 2-endo-ionization in all series. This observation is attributed to the more favorable alignment of neighbouring C-atoms for dorsal participation in exo-ionization, especially, in the case of C(6).

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Ionization Energies of 1-R-2,2-dimesitylethenols, 1,2-Dimesityl-2-phenylethenol, and Some of their Keto Tautomers (1986)

Lecoultre, Jacques ; Heilbronner, Edgar ; Biali, Silvio E. ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2108-2113

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Notes: The He(Iα) PE spectra of the two pairs of 1(Ph)-3 and 2-4 have been recorded and assigned by comparison with spectra of related molecules, or by using simple MO arguments. This analysis shows that the PE spectra are in agreement with the assumption that the twist angles observed in the crystalline state are more or less conserved in the gas phase. The observed first adiabatic ionization energies IIa allow the calculation of the molar reaction enthalpy ΔrHmθ which accompanies the enolization of the radical cations of the title compounds. It is found that ΔrHmθ ≍ --70 kJ mol-1 is roughly the same for both keto/enol pairs, in qualitative and quantitative agreement with expectation. These results complement and correct ionization energies determined previously by mass spectrometric methods and conclusions based on them.

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Erratum (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2133-2133

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Keywords: Chemistry ; Organic Chemistry

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URL: http://dx.doi.org/10.1002/hlca.19860690838

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Mitteilungen (1986)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2197-2200

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Synthesis and Biological Properties of N-Acetyl-4-deoxy-D-neuraminic Acid (1986)

Hagedorn, Heinz-Werner ; Brossmer, Reinhard

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2127-2132

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Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: N-Acetylneuraminic acid (1) can be transformed into the methyl α-D-ketoside 2 which, by reaction with methanesulfonyl chloride, yields the corresponding 4-O-mesylate 3 and the 4,7-di-O-mesylate 4 as a by-product. Compound 3 reacts with Nal giving the 4-deoxy-4-iodo compound 5 with equatorial orientation of the I-atom. As second product, the dihydrooxazole 6 is produced. Catalytic hydrogenation of 5 is followed by ester cleavage and removal of the isopropylidene group yielding the methyl α-D-ketoside 8 which affords the title compound, N-acetyl-4-deoxyneuraminic acid (9), by reaction with fowl plague virus sialidase. Further biochemical activities of 8 and 9 are reported.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19860690837

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Charge Dispersal in the Quinuclidine Radical Cation and in the Quinuclidinium Ion, as Revealed by PE and ICR Spectroscopy (1986)

Heilbronner, Edgar ; Honegger, Evi ; Lecoultre, Jacques ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 2114-2126

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The nN-1 ionization energies I1c and the gas-phase basicities GB of CH3-, Cl-, or CN-substituted quinuclidines have been measured by PE and ICR spectroscopy. The dependence of the shifts ΔI1c and ΔGB (relative to the values of the parent molecule) allow conclusions about the charge dispersal accompanying the nN-1 ionization or the protonation of quinuclidine in the gas phase. The agreement with the results of a minimal basis set ab initio calculation is excellent. Comparison of the solution pKa values with either I1c or GB reveals that 2-substituted quinuclidines exhibit sizeable solvent-induced proximity effects, i.e. that the corresponding quinuclidinium ions are more acidic in solution than expected on the basis of the gas-phase basicities. This agrees with earlier results concerning 2-substituted pyridines.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19860690836

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Makrocyclische Benzolactone durch Ringerweiterung von 2-Nitrocycloalkanonen (1986)

Stach, Hans ; Hesse, Manfred

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 85-90

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Macrocyclic Benzolactones by Ring Enlargement of 2-NitrocycloalkanonesReaction of 2-nitroalkanones with 1,4-benzoquinone in the presence of 1,8-diazabicyclo[5.4.0]undec-7-en gave (hydroxybenzo)nitrolactones of general formula 6 (Scheme 1). The transformation involves a Michael reaction, aromatization, and ring enlargement via a five-membered intermediate. The (hydroxybenzo)nitrolactones were converted to the already known (acetoxybenzo)oxolactones 15-17. The characteristic mass spectral behavior of the ring-enlarged products is discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19860690112

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15N-NMR Spectroscopic Characterization of Triaziridines (1986)

Hilpert, Hans ; Hollenstein, Roger

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 69 (1986), S. 136-140

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The 15N-NMR spectra of cis- and trans-2,3-dialkyl-substituted triaziridines are reported. The assignment of the 15N-NMR resonances is described, and the chemical-shift and coupling data are compared with those of aziridines and diaziridines. The 1J(N,H) coupling constants allow one to deduce the relative configuration of the involved N-atom. In CDCl3, a 1J(N,H) value of 58.1 ± 0.5 Hz is assigned to an N—H bond cis to two lone-pairs of electrons at neighboring N-atoms, i.e. to the cis,trans-triaziridinesThe first stereodescriptor denotes the relative configuration of the two equal alkyl substituents, the second the relative configuration of one alkyl substituent and the H-atom., and a value of 51.7 ± 0.5 Hz is assigned to a N—H bond cis to only one lone-pair of electrons, i.e. to trans, cis-triaziridines.

Additional Material: 2 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/hlca.19860690116

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