Epoxide derivatives of pipecolic acid and proline are inhibitors of pipecolate oxidase.

The cis-4,5-epoxide derivative of L-pipecolic acid (2S,4S,5R-epoxypipecolic acid, cis-3) was synthesized and found to serve as an excellent substrate for L-pipecolate oxidase (L-PO) and also to cause time-dependent, irreversible inactivation of the enzyme. Data are presented showing this compound is a mechanism-based inhibitor of L-PO, whereas 2S,3R,4S-epoxyproline acts as a reversible inhibitor.