Mercaptolysis of the E/F Rings of Steroidal Sapogenins: A Concise Synthesis of Δ²⁰⁽²²⁾‐Furostene‐26‐thioethers

Abstract

Lewis acid catalyzed mercaptolysis of steroidal SapogeninS was reinvestigated. Besides obtaining the reported 26-thioacetals 5 under milder conditions, a new type of compounds Am(a)-furostena26-thioethers 6 were also synthesized through the mercaptolysis of steroidal sapogenins, which can be used to the synthesis of the steroidal molecule with side chains.

Structure, Bioactivity, and Chemical Synthesis of OSW-1 and Other Steroidal Glycosides in the Genus Ornithogalum

“…The opening of the E/F ring was the first key step for utilizing the intact skeleton of sapogenins to synthesize the aglycon of OSW-1. 145 , an abundant and cheap plant-derived steroidal sapogenin, readily reacted with thiols or dithiols in the presence of a Lewis acid such as BF 3 ·Et 2 O to afford directly the 26-thioacetal 146 . , The 26-thioacetal 146 underwent reductive desulfurization catalyzed by W-2 Raney nickel to realize the needed conversion at C-26. For further modification of the E ring, the Δ 5(6) -double bond and C-3 hydroxyl group in the A/B ring of 147 were protected via a classical carbonation rearrangement .…”