FORMAL SYNTHESIS OF 3-DEOXY-D-MANNO-2-OCTULOSONIC ACID (KDO) VIA A HIGHLY DOUBLE-STEREOSELECTIVE HETERO-DIELS-ALDER REACTION DIRECTED BY A (SALEN)CO-II CATALYST AND CHIRAL DIENE

This paper presents a formal total synthesis of 3-deoxy-D-manno-2-octu losonic acid (KDO) based on a highly double-stereoselective hetero Die ls-Alder reaction between an electron-rich diene and ethyl glyoxylate catalyzed by (Salen)Co-II complex, a new catalyst for Diels-Alder reac tions. A facial specific hydroboration followed by oxidative workup le ads to a diol system with the trans-diequatorial arrangement of hydrox yl groups at the C-4 and C-5. Inversion of the configuration of the C- 5 hydroxyl group in 12 and then ketal formation afford the desired tar get diisopropylidene-2-deoxy-KDO methyl ester (18), which can be conve rted to KDO according to the literature procedure.