Stereoselective divergent synthesis of four diastereomers of pachastrissamine (jaspine B).

A divergent short synthesis of four diastereomers of pachastrissamine was achieved. Natural pachastrissamine was synthesized through bis-tosylation of the common intermediate and cyclization. 2-epi-Pachastrissamine was obtained by monotosylation and spontaneous cyclization of D-ribo-phytosphingosine derivative. By use of regio- and stereospecific ring-opening reaction of the orthoester assisted by a Boc group as a key step, 3-epi- and 2,3-epi-pachastrissamines were synthesized. The three stereogenic centers of all the diastereomers were constructed by using Garner's aldehyde as the sole chiral source.