摘要:

AbstractThe stereoselective synthesis of (±)‐4,4‐dinor‐9βH‐pimara‐7,19‐diene,6, is described. This compound represents the B,C‐ring system of the momilactones, fungitoxic diterpenes having a 9βH‐pimarane skeleton. Thetrans‐syn‐cistricyclic system was formed via aDiels‐Alderreaction of formyl enone9with 2‐(tert‐butyldimethylsilyloxy)‐3‐methyl‐1,3‐butadiene. The resulting regiospecific silyl enol ether was deformylated and stereoselectively reduced to alcohol26. This alcohol was dehydrated to alkene22and acylated to acetate23, respectively. Alkylation of22gave the α‐dithiolanyl compound27. Alkylation of23gave the β‐dithiolanyl compound35. Compound27, containing an α‐oriented dithiolanyl group, could be converted into model compound6, which possesses a β‐oriented vinyl substituent as a result of an equilibrium during theWittigreaction. Compound35was converted into model compoun

ISSN:0165-0513    

DOI:10.1002/recl.19851040702

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19851040703

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractPseudo‐first‐order rate constants have been measured for the acid‐catalyzed hydrolysis of a series ofN,N‐dimethyl‐ andN‐methyl‐N‐phenylbenzenesulfonamides in 70% (v/v) CF3CO2H/H2O at 99°C. Analysis of the effect of alkyl substituents in the benzene ring shows a remarkable rate enhancement byortho‐alkyl groups, in contrast with a rate retardation of similar substituents in the corresponding benzamides. The rate enhancement in the sulfonamides is attributed to relief of initial‐state strain in the transition state for hydrolysis. When the sulfonamide moiety is contained in a five‐membered ring fused to a phenyl ring, the rate of hydrolysis is markedly reduced by anor

ISSN:0165-0513    

DOI:10.1002/recl.19851040704

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThebaine (1) was converted intoN‐formylnorthebaine (4) viaN‐demethylation using diethyl azodicarboxylate followed by treatment with ethyl formate.Diels‐Alderreaction of4with nitroethene yielded5exclusively with the 6α,14α‐etheno bridge and the nitro group in the 7α‐position. Hydrolysis of5and methylation then gave7, the nitroethene addition product of thebaine. Reduction of5and7with aluminium amalgam gave the corresponding 7α‐amines11and8, respectively. Reduction of7with formamidinesulfinic acid or with lithium aluminium hydride gave

ISSN:0165-0513    

DOI:10.1002/recl.19851040705

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractA number of phosphorodichloridites (1) carrying various β‐functionalized ethyl protective groups were converted into their corresponding phosphoromorpholido chloridites (2). These were then reacted with 5′‐O‐(dimethoxytrityl)thymidine to give the pertinent phosphoromorpholidites (3). The applicability of these compounds in the synthesis of oligodeoxynucleotides on a solid support has been evaluated using the synthesis of the thymidine

ISSN:0165-0513    

DOI:10.1002/recl.19851040706

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe behaviour of a polypyrrole‐modified electrode in an aqueous 0.5 M HCl solution at high anodic potentials was studied. Electrochemical experiments and13C‐NMR analysis showed a decrease in conductivity, due to the formation of CCl bonds in the pyrrole ring stru

ISSN:0165-0513    

DOI:10.1002/recl.19851040707

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19851040701

出版商:WILEY‐VCH Verlag    

年代:1985

数据来源: WILEY