Synthesis of (2R,4R)- and (2S,4S)-4-hydroxypipecolic acid derivatives and (2S,4S)-(−)-SS20846A

Syntheses of protected derivatives of both enantiomers of trans-4-hydroxypipecolic acid (2) and the natural product (−)-SS20846A (3) were accomplished from vinylglycinols. Key transformations involved construction of the piperidine ring via ring-closing metathesis (Grubbs’ catalyst) and installation of the 4-hydroxy substituent by Prevost reaction. X-Ray diffraction analyses conclusively established the regio- and stereochemistry of key intermediates.