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-octulosonic acid (KDO) based on a highly double-stereoselective hetero Diels-Alder reaction between an electron-rich diene and ethyl glyoxylate catalyzed by (Salen)Co(II) complex, a new catalyst for Diels-Alder reactions. A facial specific hydroboration followed by oxidative workup leads to a diol system with the trans-diequatorial arrangement of hydroxyl 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 target diisopropylidene-2-deoxy-KDO methyl ester (18), which can be converted to KDO according to the literature procedure.
Hu
Yun-Jin
YJ
State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai, 200032, China.
Huang
Xiao-Dong
XD
Yao
Zhu-Jun
ZJ
Wu
Yu-Lin
YL