Studies on the total synthesis of sanglifehrin A: stereoselective synthesis of the C(29)-C(39) fragment

A highly stereoselective synthesis of the C(29)-C(39) fragment of the potent immunosuppressant sanglifehrin A has been accomplished by a sequence involving 16 steps (18% overall yield) from N-propionyloxazolidinone 9. Key steps are a diastereoselective hydroboration, and a diastereoselective epoxidation of an allylic alcohol followed by a 1,5-anti boron-mediated aldol reaction of methyl ketone 4 with chiral aldehyde 5.