作者:Matthias Müller、Ursula Huchel、Armin Geyer、Richard R. Schmidt
DOI:10.1021/jo990132e
日期:1999.8.1
The m-xylylene moiety was employed as rigid spacer in intramolecular glycoside bond formation. Fifteen-membered macrocycle formation starting from 6-O-linked donor and 6- and 4-O-linked acceptor (5a,b, 6b) led exclusively to beta(1-4)- and beta(1-6)-linked compounds 7 beta and 8 beta, respectively, which gave cellobioside and gentiobioside derivatives. The glycosylation yields could be improved by 14-membered macrocycle formation. In the four cases studied, the donor was 6-O-linked to the spacer. For the acceptor linkage to the spacer and the accepting hydroxy group, relative D-/L-threo- and D-/L-erythro-arrangements were chosen. Standard glycosylation conditions led in three cases (13, 14, 23) only to beta-linkage in high yield (16 beta, 17 beta, 25 beta). For the transformation of 24, having a D-erythro-arrangement in the acceptor moiety, the alpha-anomer 26 alpha was preferentially obtained. Limitation of the conformational space of the donor and the acceptor as in 31, which is stereochemically identical with 24, led to the corresponding alpha-glycoside 32 alpha in 87% yield. Synthesis of a pseudo mirror image of 23 [having 6-(D)/3-(D-threo)-arrangement], namely 35, having 3(L)/6-(L-threo)-arrangement of the donor and acceptor moieties, expectedly gave only alpha-glycoside 36 alpha in very high yield. Thus, the efficiency and versatility of this conceptual approach to intramolecular glycoside bond formation is exhibited.