A Protecting Group-Free Synthesis Of (?)-Hortonones A-C From The Inhoffen-Lythgoe Diol

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.