An expeditious route to the synthesis of kelampayosides A and B

Chemoselective NIS/cat. TfOH-mediated glycosylation of ethyl 2,3,4-tri-O-be nzoyl-1-thio-beta-D-glucopyranoside (13) with ethyl 2,3-di-O-acetyl-5-O-ben zyl-1-thio-alpha/beta-D-erythro-apiofuranoside (4a) gave dimer 14 in an exc ellent yield. BF . Et2O-catalysed condensation of the alpha-trichloroacetim idate 31, accessible in two steps from 14, with 3,4,5-trimethoxyphenol gave beta-linked derivative 32 followed by deprotection gave Kelampayoside A. P rotecting group manipulations of 32 and subsequent caffeoylation of resulti ng 36 followed by deprotection gave Kelampayoside B. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.