摘要:

AbstractChemical synthesis and biological activities of a new α‐melanotropin derivative are described.Nα‐(5‐Bromovaleryl)‐Nα‐deacetyl‐α‐melanotropin contains the 5‐bromopentanoyl group as a chemical ‘handle’ in place of the acetyl group of the natural hormone. The synthesis involved a new protected intermediate which allowed the selective deprotection of either the Nαor Nαamino group. The title compound reacted with sodium thiosulfate to giveNα‐deacetyl‐Nα‐(5‐(sulfothio)valeryl)‐α‐melanotropin, a key intermediate for the preparation of tobaccomosaic virus/α‐melanotropin disulfide conjugates. As a basis for the study of the conjugates, biological activities of the title compound onCloudman S‐91 mouse melanoma cell cultures (tyrosinase stimulation, binding, andcyclicAMP accumulation) were determined. They proved to be quite similar to the corresponding α‐melanotropin activities. Differences in bindings may be explained by stronger hydrophobic interaction of the new derivative w

ISSN:0018-019X    

DOI:10.1002/hlca.19850680102

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractAsymmetric disulfide conjugates of mercaptosuccinyl tobacco mosaic virus (TMV ∼ SH) withNα‐desacetyl‐Nα‐5‐(mercaptovaleryl)‐α‐melanotropin were preparedviatheS‐sulfoderivative of the peptide. The conjugates, TMV ∼ SS ∼ α‐MSH(n), contained up ton= 330 disulfide‐linked peptide molecules/virion. Similarly, fluorescent conjugates, Rh(m) ∼ TMV ∼ SS ∼ α‐MSH(n) were prepared, containingm≈︁ 200 rhodamine molecules linked to the virions by thiourea bridges. Such conjugates were designed to study α‐MSH receptor localization and dynamics (mainly internalization), because the carrier virions which served to enhance specific receptor binding and as fluorescent or radioactive markers may be detached from the neuropeptides at will by reduction. Reduction occurred in solution and on the cell surface, but not in the cytoplasm, thus allowing detection of internalized agonist‐receptor complexes. The conjugates were superpotent agonists for tyrosinase stimulation inCloudman S‐91melanoma cell cultures, but were inactive forcyclicAMP accumulation. Their rather rapid internalization and the influence of reducing agents and other agonists on their biologic activity suggest a close connection between receptor location and biologic response as w

ISSN:0018-019X    

DOI:10.1002/hlca.19850680103

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe σ‐orbital manifold of cubane1, as suggested by its PE spectrum, is divided into two sets separated by a 3 eV gap extending from ∼ ‐10.5 eV to ∼ ‐13.5 eV. Halogen substituents with np AO basis energies falling into this gap (e.g.Cl or Br) will, therefore, hyperconjugate appreciably with both sets. Interaction with the lower‐lying set will lead to the usual destabilization (‘normal’ hyperconjugation), whereas interaction with the set above will necessarily lead to a ‘stabilization’ (‘inverted’ hyperconjugation). As a result the lone‐pair ionization energies of Cl or Br substituted cubanes (derived from PE spectra) are much larger than naively expected for an alkyl halide containing as much as 8 C‐atoms. In particular no significant shift of the e g−1lone‐pair bands in the PE spectra of 1,4‐dichloro‐ and 1,4‐dibromocubane can be detected with respect to the first ionization energies of the

ISSN:0018-019X    

DOI:10.1002/hlca.19850680104

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe title sponge is shown to contain eight new sesquiterpenoids for which a common, unusual biogenetic origin is postulated. The compounds are shown to be: (–)‐(1R*,4R*)‐3‐(3′‐furyl)methyl‐2‐p‐menthen‐7‐yl acetate ((–)‐8b); two diols separated as the monoacetates (–)‐(1S*,4R*)‐3‐(3′‐furyl)methyl‐l‐hydroxy‐2‐p‐menthen‐7‐yl acetate ((–)‐13a) and the (–)‐(1R*,4R*)‐epimer (–)‐13b, the two C(4)‐epimeric 4‐ethoxy‐3‐(1′(7′),2′‐p‐menthadien‐3′‐yl)methyl‐2‐buten‐4‐olides ((+)‐14aand (–)‐14b), (–)‐3‐(3′‐furyl)methyl‐7‐nor‐2‐p‐menthen‐l‐one ((–)‐11), (

ISSN:0018-019X    

DOI:10.1002/hlca.19850680105

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractReaction of glutarimide with pent‐4‐enylmagnesium bromide, followed by cyclization of intermediate ketoamide, and hydrolysis of the formates10and13led to the mixture of the hydroxylactams11(cis)and14(trans)which could be separatedviatheir benzenecarbamates. Reduction ofcis‐hydroxylactam11with LiAlH4yielded 2‐depentyl‐7‐debutylperhydrohistrionicotoxin (6), whereas reduction oftrans‐isomer14gave the epimeric alcohol9.cis‐Hydroxylactam11was convertedviathiolactam17and the methylthio derivative18to ketimine19which was reduced with NaBH4yielding a mixture of natural4and unnatural7, analogues of perhydrohistrionicotoxin (2). Reduction of4with H2in the presence of Pd/C yielded (±)‐7‐debutylperhydro

ISSN:0018-019X    

DOI:10.1002/hlca.19850680106

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

Halochromic Molecules. Synthesis of Substituted 6H‐Chromeno[4,3‐b]indolizines and their Aza‐analoguesWe have synthesized a series of substituted chromeno[4,3‐b]indolizines and their respective aza‐analogues. Dyes generated from them contain the electrondonating 2‐(2‐hydroxy‐5‐methylphenyl)indolizin‐3‐yl moiety. The 90 MHz FT1H‐NMR spectra of starting and final products supported the postulated structures. Fragmentations in the mass spectra also were consistent with

ISSN:0018-019X    

DOI:10.1002/hlca.19850680107

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

Halochromic Molecules. Spectrophotometric Investigation of the Acidobasic Behaviour of Substituted 6,6‐Diphenyl‐6H‐chromeno[4, 3‐b]indolizines and their Aza‐analoguesSubstituted 6,6‐diphenyl‐6H‐chromeno[4,3‐b]indolizines form ring‐opened, intensely coloured (diphenyl)‐indolizinylcarbenium salts with acid. UV/VIS spectra of the coloured salts are discussed on the basis of VEPPPCI calculations. The ϵpH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex

ISSN:0018-019X    

DOI:10.1002/hlca.19850680108

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractDisplacements of1H‐NMR chemical shifs for caffeine in D2O solution as a function of concentration conform to the behaviour expected for pure dimer formation according to the equilibrium 2(caffeine)⇄(caffeine)2with a statistical probability of at least 95%. Confidence limits reported earlier for the dimerisation constant of caffeine represent the real statistical dispersion in the experimental data and do not reflect a systematic error such as tetramer format

ISSN:0018-019X    

DOI:10.1002/hlca.19850680109

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe carbonyl group in lactones and, to a lesser extent, in lactams tends to show a CCO angle that is larger than the OCO or NCO angle, the difference increasing in magnitude as the ring size decreases. The observed trend provides information on ratios of force constants characterising the flexibility of the s‐cis‐ester group and may be interpreted in terms of incipient chemical reaction to−O(CH2)nCO+. Molecular orbital calculations (MINDO/3, MNDO, EH) for model compounds provide an electronic interpretation of this angle difference in terms of an anomeric interaction between the p‐type lone pair on the carbonyl O‐atom and the ant

ISSN:0018-019X    

DOI:10.1002/hlca.19850680110

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

Isolation of Bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranoside). Structural Determination by Chemical Correlation with Bafilomycin A1and LeucanicidinFrom cultures of an actinomycete strain, the known antifungal and insecticidal antibiotic leucanicidin (1) and a hitherto unknown antifungal antibiotic, bafilomycin‐A1‐21‐O‐(α‐L‐rhamnopyranoside) (2), were isolated. The latter is spectroscopically closely related to1and bafilomycin A1(3) and gave degradation products identical with compounds obtained by anal

ISSN:0018-019X    

DOI:10.1002/hlca.19850680111

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY