ENANTIOSELECTIVE TOTAL SYNTHESIS OF (-)-SCABRONINE D

The first enantioselective total synthesis of (-)-scabronine D comprising a unique bridged hemiacetal is described. The total synthesis is successfully accomplished using an enantiopure intermediate prepared in the total synthesis of (-)-scabronines G and A, and (-)-episcabronine A. Because the advanced intermediate was found to be sensitive to basic reaction conditions, the C14 keto and C11 hydroxy groups had to be co-protected as methyl acetal. In addition, both the C15 hydroxy and C17 carboxyl groups were too reactive to be chemically discriminated; hence, the carboxyl group once formed was protected as a tert-butyl ester for ensuring successful transformations.