Two new syntheses of protected dipeptide analogues bearing a trans carbon-carbon double bond in place of the amide linkage are reported. One route is a linear synthesis employing the rearrangement of an allylic selenide to a protected allylic amine. The second route is convergent and uses the Julia olefin synthesis in a key step. The latter route is fully stereocontrolled and has been used to prepare protected trans-alkene isosteres of the ...
