An efficient and scalable synthesis of enantiomerically pure N-Boc-protected 4-(Z)-propenylproline (15) using the conventional Wittig reaction to construct the double bond has been developed [11% yield over 8 steps from N-Boc-pro- (29)] was prepared along a reasonably efficient synthetic route applying the thermal rearrangement of 2-azido-6-chloropyridine N-oxide (22) as a key step in fairly good overall yield [9% over 7 steps from easily accessible 2,6-dichloro-