摘要:
An efficient synthesis of 4-methoxyphenyl alpha-L-Rhap-(1 -> 3)-alpha-L-Rhap-(1 -> 3)-alpha-L-Rhap-(1 -> 2)-6-deoxy-alpha-L-Talp, the tetrasaccharide related to the GPLs of Mycobacterium intracellare serotype 7, was achieved with 4-methoxyphenyl 3,4-di-O-benzoyl-6-deoxy-alpha-L-talopyranoside (6c) as the key intermediate which was obtained through selective 3-O-benzoylation of 4-O-benzoyl-6-deoxy-alpha-L-taloside. Coupling of 6c with 3-O-allyloxycarbonyl-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate followed by removal of the allyloxycarbonyl protecting group afforded the disaccharide acceptor 11. Condensation of 11 with 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl-(1 -> 3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate and subsequent deprotection gave the target tetrasaccharide. (C) 2008 Elsevier Ltd. All rights reserved.