Diastereoselective Approach to <i>cis</i>-4-Methyl/thiol-Pipecolic Esters Based on RCM Reaction and Conjugate Michael Addition

<div><p></p><p>A synthetic route for the access to enantiopure <i>cis</i>-4-methyl/thiol-pipecolic esters is presented. It is based on the ring-closing metathesis reaction to build the α,β-unsaturated piperidin-2-one derived from (<i>S</i>)-(–)-phenylethylamine, followed by either diastereoselective conjugate addition of methylorganocuprate allowing access to <i>cis</i>-4-methyl pipecolic ester or by tandem diastereoselective hydrosulforization–thionization reaction providing access to <i>cis</i>-4-thiol pipecolic ethyl esters.</p>