An Efficient Stereoselective Synthesis of Δ4,5-Pipecolic Esters

Article abstract of DOI:10.1021/jo00048a030

The synthesis of racemic and enantiomerically homogeneous pipecolic esters from 1-amino-3-buten-2-ols is reported.The synthesis of enantiomerically homogeneous N-methylpipecolic esters requires four chemical steps from N-t-BOC-protected amino esters.The key step of the sequence is a conformationally restricted Claisen rearrangement.The method affords complete control of the absolute and relative stereochemistry of all three stereogenic centers in pipecolic ester 22 which is obtained in 33percent overall yield from N-t-BOC-L-alanine ethyl ester 16a.