Synthesis of 3-C-Branched Kdo Analogues via Sonogashira Coupling of 3-lodo Kdo Glycal with Terminal Alkynes

摘要

A highly efficient approach for the synthesis of 3-C-branched mono- and di-3-deoxy-n-manno-oct-2-ulosonic acid (Kdo) enyne analogues is developed for the first time based on Sonogashira coupling of terminal alkynes with 3-iodo Kdo glycal obtained by the NIS/TMSOTf-promoted one-step reaction from peracetylated Kdo ethyl ester. Further transformation of 3-C-branched mono- and di-Kdo enyne analogues by asymmetric hydrogenation and saponification provided 2-deoxy-beta-carboxyl Kdo analogues in a stereocontrolled mode.