Enantioselective Synthesis of (+)-Ricciocarpin A Using an Auxiliary Hydroxyl Group and a Diastereofacial Selectivity Based Methodology

An enantioselective synthesis of (+)-ricciocarpin A is described starting from (+)-karahana lactone as an enantiopure building block. This synthesis involves a stereofacially directed diastereoselective hydroboration for the installation of the required stereogenic center, and the efficient conversion of an intermediate hydroxyaldehyde to the one-carbon homologated cyanide, using the mild formation of a cyanohydrin followed by an one-pot two-step Barton-McCombie double deoxygenation sequence of the hydroxyl moieties.