An expeditious route to the synthesis of kelampayosides A and B

Abstract

Chemoselective NIS/cat. TfOH-mediated glycosylation of ethyl 2,3,4-tri- O-benzoyl-1-thio-β-D-glucopyranoside (13) with ethyl 2,3-di-O-acetyl-5-O- benzyl-1-thio-α/β-erythro-apiofuranoside (4a) gave direct 14 in an excellent yield. BF3·Et2O-catalysed condensation of the α- trichloroacetimidate 31, accessible in two steps from 14, with 3,4,5- trimethoxyphenol gave β-linked derivative 32 followed by deprotection gave Kelampayoside A. Protecting group manipulations of 32 and subsequent caffeoylation of resulting 36 followed by deprotection gave Kelampayoside B.