The key step in the preparation of racemic (Z)-14-heptadecen-4-olide (VIa) and (Z)-11-pentadecen-4-olide (VIb), sex pheromone analogues of Ostrinia nubilalis and Cydia molesta, was efficient cross-coupling reaction of 3-methoxycarbonylpropanoyl chloride with corresponding (Z)-alkenylmagnesium bromides. The methyl 4-oxo-(Z)-14-heptadecenoate (Va) and methyl 4-oxo-(Z)-11-pentadecenoate (Vb) prepared in this way were converted by one-pot reaction using sodium borohydride in an ethanolic solution to the required (Z)-alken-4-olides (VIa, VIb).