摘要:

AbstractOn ultraviolet irradiation O‐acetyljervine (1) is subjected to several parallel fragmentations. From the complex reaction mixtures obtained in a variety of solvents (dioxan, tetrahydrofuran, acetonitrile, iso‐octane, benzene) the major alicyclic products6–8and the heterocyclic compounds12–16have been isolated. Products6–8undergo further photochemical changes,e.g., decarbonylation of7to9and hydrolytic cleavage of8to10.These photofragmentations are initiated almost specifically upon selective π → π* excitation at 2537 Å with a quantum yield of Φ2537= 0.145 for conversion of starting material. Reaction upon irradiation in the long‐wavelengthn→ π* absorption band is very much less efficient (Φ3660= 0.611 · 10−3, both determinations for O‐trimethylsilyl‐jervine (2) in tetrahydrofuran). A high degree of photostability is observed also at 2537 Å on N‐protonation of O‐acetyljervine (1) in acetic acid. Furthermore, reactivity is greatly reduced for the N‐methyl (3) and N‐acetyl (4) derivatives in neutral solvents at 2537 Å. N‐Chloro‐O‐acetyljervine (5) in dioxan at 2537 Å gave

ISSN:0018-019X    

DOI:10.1002/hlca.19710540202

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractDie Synthese von (±)‐Dehydroheliotridin, dem enzymatisch produzierten Hauptabbauprodukt der Alkaloide Lasiocarpin und Heliotrin, wird beschrieben. Als Edukt dient 1,6‐Dihydroxy‐2, 5‐dicyan‐hexatrien‐(1,3,5)‐dicarbonsäure‐(1,6)‐diäthylester, der mit β‐Alaninäthylester versetzt wird. Das erhaltene 1‐(2‐Äthoxycarbonyl‐äthyl)‐2‐äthoxycarbonyl‐3‐cyanpyrrol wird zu einer Tricarbonsäure hydrolysiert, dann verestert und schliesslich zu (±)‐1,6‐Diäthoxycarbonyl‐7‐oxo‐6, 7‐dihydro‐5H‐pyrrolizidin cyclisiert. Letzteres ergibt Dehydroheliotridin durch Verseifung, Decarboxylierung, Veresterung zu 1‐Methoxycarbonyl‐7‐o

ISSN:0018-019X    

DOI:10.1002/hlca.19710540203

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe ionic reaction of linalool and N‐bromosuccinimide in CCl4at room temperature afforded 2‐methyl‐2‐vinyl‐5‐(1‐bromo‐1‐methyl‐ethyl)‐tetrahydrofuran (I). On treatment with refluxing collidine this compound yielded the intermediate allyl vinyl ether III, which immediatealy rearranged to 2,2, 5‐trimethylcyclohept‐4‐en‐one (V) or «karahanaenone» through a [3,3]‐sigmatropic process. Karahanaenone, a constituent of hop oil, was thus synthesized for the first time (overall yield 62% from linalool). The mechanisms

ISSN:0018-019X    

DOI:10.1002/hlca.19710540204

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe cycloaddition reactions of cycloheptatriene with acrylonitrile and methyl acrylate have been investigated in some detail. Theexo(1) andendo(2) adducts resulting from the [2+2+2]‐cycloaddition of acrylic components to the 2,5‐positions of cycloheptatriene have been separated and the structures have been elucidated by NMR. The by‐products are 7‐endo‐substitued derivatives of bicyclo[4,2,1]nona‐2,4‐diene (3), resulting from the formal [6+2]‐cycloaddition to the 1,6‐positions of cycloheptatriene. The mechanism of their formation is discussed.Irradiation (λ = 253,7 nm) of3in various solvents gave an almost quantitativ yield of [2+2]‐cyclodimers of the14type. No intramolecular photocyclization of3to cyclobutenes13aa

ISSN:0018-019X    

DOI:10.1002/hlca.19710540205

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractPig kidney particulate aminopeptidase (EC 3.4.1.2) was purified by a modification of the procedure ofWachsmuth et al.[3] to a state of homogeneity according to criteria of ultracentrifugation and polyacrylamide gel electrophoresis, and some of its physical and chemical properties were determined.The purified enzyme (specific activity 30 ± 3 μmoles leucine‐p‐nitroanilide hydrolyzed/min/mg) has as20,w= 9.82 S at pH 8 and a molecular weight of about 280,000 as determined by high speed sedimentation equilibrium. Divergence between the number‐, weight‐ and z‐ average molecular weights, and a sharp decrease of these values at low protein concentration, suggest that one is dealing with an associating‐dissociating system.Amino acid analysis revealed the presence of considerable quantities of carbohydrates in the enzyme. Colorimetric, gas chromatographic and enzymatic analyses demonstrated the presence of glucosamine, galactose, mannose, fucose and sialic acid residues in the ratio of 1:0.89:0.75: 0.13: 0.13, amounting toca. 400 residues or 20% (56,000 daltons) of the molecular weight. With the exception of sialic acid, the carbohydrate content was remarkably constant from preparation to preparation.Analyses by both atomic absorption spectrometry and the dithizone method showed that zinc–the only metal found in significant amount–was always present in the ratio of 2 atoms per molecule. It is therefore proposed that pig kidney particulate aminopeptidase is a Zn‐cont

ISSN:0018-019X    

DOI:10.1002/hlca.19710540206

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractRadicals H2NĊHCOOH and H2NĊHCOO−which have different ESR. spectra are observed during the reaction of hydroxyl radicals with glycine in aqueous solution. Rapid and reversible exchange between the different dissociated radicals is induced by addition of phosphoric acid. The pH dependence of the ESR. spectra yields the pKvalue and rate constants for proton transfer reactions between the radicals and phos

ISSN:0018-019X    

DOI:10.1002/hlca.19710540207

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe circular dichroism and optical rotatory dispersion of three vespirenes, three vespirones, and of some related 9, 9′‐spirobifluorene derivatives [4] have been measured. The absolute configurations of these compounds have been determined from chiroptical properties (CU., ORD.) in four ways which give mutually consistent results. For the (−)‐vespirenes the (R)‐configuration (Figs. 1 and 2) follows from 1 is

ISSN:0018-019X    

DOI:10.1002/hlca.19710540208

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe complex formation of the ligands given in the title has been investigated using potentiometric measurements at ionic strength 0,1 and 20°C. The results are discussed in comparison with the known values and with those of similar ligands

ISSN:0018-019X    

DOI:10.1002/hlca.19710540209

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractEine Totalsynthese des Hexahydroindolizin‐Alkaloids Ipalbidin (7) und seines β‐D‐Glucosids Ipalbin (1) wird beschrieben. Der zentrale Syntheseschritt besteht aus einer N‐Acylierung des vinylogen Amidsystems3, gefolgt von einer internen Kondensation zum pentasubstituierten Pyridon4. Die spektralen Daten von synthetischem Ipalbidin bzw. Ipalbin sind identisch mit denjenigen der entsprechenden natürlichen Verbindungen. Auf Grund des Vergleichs von optischen Drehugen wird ermittelt, dass Ipalbidin in der Natur in racemischer Form

ISSN:0018-019X    

DOI:10.1002/hlca.19710540210

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractDie Reaktion von Erythronolid B mit Säure lieferte das bisher unbekannte 8, 9‐Anhydroerythronolid‐B‐6, 9‐hemiacetal. Diese Verbindung wurde oxydativ in (8S, 9S)‐8, 9‐Anhydroerythronolid‐B‐6, 9‐hemiacetal 8,9‐epoxid und (8S)‐8‐Hydroxyerythronolid B umgewandelt. Durch Reduktion der Doppelbindung im Enoläther wurde das (9S)‐9‐Dihydro‐6, 9‐

ISSN:0018-019X    

DOI:10.1002/hlca.19710540211

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY