AbstractThis paper describes a stereospecific synthesis of nine 2E,6E, 10(Z)‐trienyl esters R1R2CCH(CH2)2CR3CH(CH2)2CR4CHCO2Me (1a‐i) and their selective conversion into the corresponding epoxides(7a‐i), including the natural occurring hormones JHI‐III. The trienyl system of1has been reached stereospecifically by allowing specifically substituted vinylcuprates, [R1R2CCHCuY]⊖, to react with 4‐iodo‐1‐butyne, followed by conversion of the formed enynes R1R2CCH(CH2)2CCH (3) into new cuprates of the type thus [R1R2CCH(CH2)2CR3CHCuY]⊖. These cuprates furnish, upon reaction with 4‐iodo‐l‐butyne, the dienynes R1R2CCH(CH2)2CR3CH(CH2)2CCH (5). From5, vinylcuprates [R1R2CCH(CH2)2CR3CH(CH2)2CR4CHCuY]⊖have been obtained which, upon reaction with carbon dioxide followed by methylation, gave compounds1. For the preparation of the vinylcuprates from the 1‐alkynes we generally used a new alkylcopper(I) s