摘要:

The Absolute Configuration of Macroline, a Degradation Product of the Alkaloid VillalstonineThe absolute configuration of macroline(1), a degradration product of villalstonine(2), was determined. The chemical degradation of1gave a mixture of (–)‐(20S)‐20,21‐dihydro‐19‐desoxo‐macroline(9)and (–)‐(20R)‐20,21‐dihydro‐19‐desoxo‐macroline(10), which was related to the degradation products9of (+)‐ajmaline(3)and10of (+)‐isoajmaline(4)of known absolute configuration. Together with the complete relative stereochemistry of2the absolute configuration of2and of the second moiety of2, (+)‐pleiocarpamine(20), could be derived. Since the absolute configuration of the (–)‐6, 7‐dihydroaspidospermidine moiety of (+)‐pycnanthinine has been known already [15], the structure byGorman et al.[17] represents the ab

ISSN:0018-019X    

DOI:10.1002/hlca.19810640112

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

Abstract13C‐NMR. and He (Iα) photoelectron spectra of alkyl phenyl sulfides, sulfoxides and sulfones have been used to probe how their conformations depend on the size of the alkyl groups R. The results are interpreted to indicate that in the sulfides the S, R‐bond is twisted out of the planar conformation with increasing size of the alkyl group, whereas in the sulfoxides and sulfones the preferred conformation with the S, R‐bond perpendicular to the phenyl group plane seems to be independent of the size of R. These conclusions are in agreement with previous work on the alkyl phenyl sulfides and provide strong support for previous conjectures concerning the preferred conformations of alkyl phenyl sulfoxides and su

ISSN:0018-019X    

DOI:10.1002/hlca.19810640113

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

Preparation of Styryl and Stilbenyl Derivatives of Pyrimidines2‐ and 4‐(p‐Tolyl)‐substituted pyrimidines react with anils of hetero‐aromatic aldehydes in the presence of dimethylformamide and potassium hydroxide or potassiumt‐butoxide to yield the corresponding 2‐ and 4‐[4″‐(heteroaryl)stilben‐4′‐yl]pyrimidines or the 2‐ and 4‐[a‐(heteroaryl)‐4′‐styryl]pyrimidines respectively (‘Anil synthesis’). Furthermore, theSchiff′s bases derived fromp‐chloroaniline and 4‐(pyrimidine‐2‐yl and 4‐yl)benzaldehydes give, with methyl‐ and withp‐tolyl‐substituted heterocycles, the corresponding heterocyclic substituted styryl and stilbenyl derivatives. Alkyl‐, alkoxy‐ or p

ISSN:0018-019X    

DOI:10.1002/hlca.19810640114

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe reactions of 2exo‐ and 2endo‐norbornyl bromide (1eand2e, respectively) in 90% ethanol with a large excess of potassium hydroxide, and of 2exo‐norbornylp‐toluenesulfonate(1g)with excess sodium thiophenolate in methyl cellosolve, have been studied. They obey the first order rate law and are zero order with respect to the base‐nucleophile. However, the ratio of 1,2‐ and 1,3‐elimination toexo‐substitution products depends strongly on the base‐nucleophile concentration. Ion pair intermediates are indicated. The extreme inertness of 2‐norbornyl derivatives in displacement reactions is due to severe steric hindrance of rearside nucleophilic attack, a feature they have in common with other bi‐ and tricyclic molecules bearing nucleofugal groups adjacent to one or

ISSN:0018-019X    

DOI:10.1002/hlca.19810640115

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractA full discussion of the configuration of tricyclo [7.1.1.02,7]undecanes related tocis‐10, 10‐dimethyltricyclo [7.1.1.02,7]undec‐2‐en‐4‐one(2), theRobinsonannelation product from norpinone1and 3‐buten‐2‐one is given, based on 360‐MHz‐NMR. spectra. NuclearOverhausereffects confirm thecisconfiguration of2, and show that the saturated ketone10, obtained by catalytic hydrogenation, is also all‐ciswith the cyclohexanone ring in the boat conformation. The parent hydrocarbon,cis‐10, 10‐dimethyltricyclo[7.1.1.02,7]undecane is compared with one of the correspondingtransisomers prepared from pinocarvone(14). The stereochemistry of metal hydride reduction andGrig

ISSN:0018-019X    

DOI:10.1002/hlca.19810640116

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThePariser‐Parr‐Pople(PPP) type LCI‐SCF‐MO calculations were used to study the models of 1, 3‐diphenyltriazene(1), 1, 3‐bis(3‐pyridyl)triazene(2), 1, 3‐bis (2, 4‐dichlorophenyl)triazene(3), and 1, 3‐bis (4‐ethoxycarbonyl)triazene(4). The results of the calculations were compared with the experimental electronic absorption and emission (fluorescence, phosphorescence) spect

ISSN:0018-019X    

DOI:10.1002/hlca.19810640117

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe isotope partition coefficient α between cyclohexane, cycloheptane and hydrogen has been determined between 80 and 180° and pressures around 1 atm. The values decrease with increasing deuterium content y of the hydrogen and can be expressed by the simple equation Ina= Δ S/R + (ΔH+ δ · y)/RT with an error of ±1%. However it was not possible to achieve good agreement with theoretical calculations using a unique average value for the partition function of the hydro

ISSN:0018-019X    

DOI:10.1002/hlca.19810640118

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe parameters which influence the inverted wave appearing in the reverse (oxidation) sweep in the cyclic voltammogramme of the title compound1are discussed in detail. The inverted wave is due to the interaction of the reduction products of1with the electrode and the electrolyte (TBAFB). The key condition for the presence of the inverted peak is a slow scan rate on the reverse sweep, at least for the last 50 mV before the inversion of the current‐potential curv

ISSN:0018-019X    

DOI:10.1002/hlca.19810640119

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe photoaddition6→7, followed by a reductive cleavage of the →‐chlorocyclobutylketone7, gave the stereochemically pure spiro [4,5]de

ISSN:0018-019X    

DOI:10.1002/hlca.19810640120

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY

摘要:

AbstractThe preparations of 1‐acetylvinyl arenecarboxylates H2C=C(COCH3)OCOR with R = phenyl,p‐nitrophenyl, 2,4‐dinitrophenyl, α‐ and β‐naphthyl are described(3). TheDiels‐Alderreactivity of these dienophiles toward cyclopentadiene is evaluated and compared with that of methyl vinylketone, 3‐trimethylsilyloxy‐, 3‐ethoxy‐ and 3‐acetoxy‐3‐buten‐2‐ones. The stereoselectivity of the cycloadditions of these dienophiles with 2,3,5,6‐tetramethylidene‐7‐oxanorbornane(1)and 5,8‐dimethoxy‐1,4‐epoxy‐2,3‐dimethylidene‐1,2,3,4‐tetrahydroanthracene(2)is studied. In principle, the dienophiles3allow direct functionalization of the position C(9) of the A‐ring of daunomycinone analogs by

ISSN:0018-019X    

DOI:10.1002/hlca.19810640121

出版商:WILEY‐VCH Verlag GmbH    

年代:1981

数据来源: WILEY