A protecting group-free synthesis of (−)-hortonones A–C from the Inhoffen–Lythgoe diol

Abstract

A synthesis of hortonones A–C has been accomplished from vitamin D₂via the Inhoffen–Lythgoe diol without the use of protective groups. Key steps in the syntheses include a TMS-diazomethane mediated regioselective homologation of the cyclohexanone ring to a cycloheptanone moiety and a sodium naphthalenide-mediated allylic alcohol transposition. It has been found that the absolute configuration of the natural hortonones is opposite that of the synthetic material prepared from vitamin D₂.