Steroids 2009-08-01

On reactions of steroidal 23-oxo and 23,24-epoxysapogenins with Lewis acids.

Izabella Jastrzebska, Leszek Siergiejczyk, Aneta M Tomkiel, Zofia Urbańczyk-Lipkowska, Dominik Wójcik, Jacek W Morzycki

Index: Steroids 74(8) , 675-83, (2009)

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Abstract

The reaction of 23-oxotigogenin acetate with TMSOTf in THF afforded the corresponding bisnorcholanic lactone in 60% yield. The analogous reactions carried out in dichloromethane or benzene gave the rearranged products--the isomeric spirostanic ketone (10-15%) and bisfuran (40-42%). Similar products were also obtained upon treatment of 23,24-epoxysapogenins with BF(3). The epoxides treated with TiCl(4) afforded mostly chlorohydrins and no rearranged products were detected.