Synthetic studies on aculeximycin: Synthesis of C24-C40 segment by kobayashi aldolization and epoxide rearrangements

Stereoselective synthesis of the C24-C40 segment of aculeximycin has been achieved by using the Kobayashi aldol reactions and epoxy-opening rearrangement reactions. The C33-C40 segment was synthesized by the Kobayashi aldol reaction followed by epoxidation and Jung rearrangement of epoxide 9, while the C25-C32 segment was constructed by the Kobayashi aldol reaction followed by epoxidation and the epoxy-opening rearrangement reaction of epoxide 13. These segments were connected by the aldol reaction and the sequential dehydration, reduction, and conversion of ethyl ester to ethyl ketone to give the C24-C40 segment 1. All stereogenic centers were constructed by substrate-controlled stereoselective reactions.