Synthesis of 3β, 6α-Dihydroxycholesta-9(11), 17(20), 24-trien-23-one, the Aglycone of Acrosome Reaction-Inducing Steroidal Saponin Co-ARIS II

Abstract

3β, 6α-Dihydroxycholesta-9(11), 17(20), 24-trien-23-one (2), the aglycone of acrosome reaction-inducing steroidal saponin Co-ARIS II (1), was synthesized from asterone diacetate (3) in 8 steps. The side chain was constructed by the coupling reaction of the allyl chloride (8) with the dithiane anion (9). Evidence for 17(20)-E stereochemistry of 2 was obtained by nuclear Overhauser effect (NOE) experiments in the proton nuclear magnetic resonance (¹H-NMR) spectrum. Comparison of the ¹H- and ¹³C-NMR data of 2 with those of 1 confirmed the structure assignment of the latter compound.