Diastereoselective Synthesis of D-erythro-sphingosine

A twelve-step, diastereoselective synthesis of D-erythro-C~s-sphingosine [(2S,3R,4E)-2-amino-l,3-dihydroxy-4-octadecene, 1] is described (12 steps, 10% overall yield), starting from 2,3-O-isopropylidene-D-glyceraldehyde 3. The first step was the crossed addition of N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyloxy)pyrrole (TB- SOP, 2) to 2,3-O-isopropylidene-D-glyceraldehyde 3 (a vinylogous variant of the Mukaiyama-aldol reaction) producing a seven-carbon lactam intermediate 4, which was then shortened by three carbon atoms to furnish the aldehydo-erythrose derivative 10. Wittig elongation of 10 with the appropriate C14 ylide, followed by photoinduced Z to E double bond isomerization and removal of the protecting groups, completed the synthesis.