Total Synthesis and Biological Evaluation of Prealnumycin B

Prealnumycin B is an aromatic polyketide characterized as a reduced form of prealnumycin with a 6S-alcohol. As an extension of our earlier work on the synthesis of prealnumycin, the C7-C8 double bond was hydrogenated using Wilkinson's catalyst, and the C6 carbonyl group was stereoselectively reduced via asymmetric transfer hydrogenation with the (S,S)-Ts-DENEB catalyst, where the use of methanol as a solvent was crucial for achieving high regioselectivity. By comparing its spectroscopic data with those of the natural isolate, the absolute configuration of prealnumycin B was determined to be 1R,6S. In addition, the antibacterial activities of prealnumycin B and related compounds were evaluated.