New analogues of the potent cytotoxic saponin OSW-1.

Saponin OSW-1 (5e-G2; 3 beta,16 beta,17 alpha-trihydroxycholest-5-en-22-one 16-O-{O-[2-O-(4-methoxybenzoyl)-beta-D-xylopyranosyl]-(1-->3)-2-O-acetyl-alpha-arabinopyranoside}) analogues: with modified side chain (5a/d-G2), 22-deoxo-23,24,25,26,27-pentanor- (14), 22-deoxo-23-oxa- (17), glycosylated with various monosaccharides (5e-G4/G6/G8), and OSW-1 structural isomer (10) were obtained. The analogues were synthesized using a previously published method for the synthesis of OSW-1. The structures of analogues were fully confirmed by spectroscopic methods, and the S-chirality at C-22 of the structural isomer was established by conformational analysis combined with the NMR spectrometry.