Total Synthesis of an Immunosuppressive Glycolipid,(2S,3S,4R)-1-O-(alpha-D-Galactosyl)-2-tetracosanoylamino-l,3,4-nonanetriol

摘要

A practical and efficient total synthesis of (2S,3S,4R)-1-O-(alpha-D-galactosyl)-2-tetracosanoylamino-l,3,4-nonanetriol.OCH 1b,a potential therapeutic candidate for Thl-mediated autoimmune diseases,is described.The synthesis incorporates direct alkylation onto epoxide 5 and stereospecific halide ion catalyzed alpha-glycosidation reaction.A key intermediate 10 was obtained in only eight steps and 37% overall yield from commercially available D-arabitol 2,and the total synthesis of 1b was accomplished in 12 steps and 19% overall yield.This method will enable the synthesis of a variety of phytosphingolipids,especially that with the shorter sphingosine side chain than la.in a highly stereo-selective manner.