ZnCl2-triggered lactonization reactions of γ,δ-epoxy-β-silyloxy esters with remote alkoxy groups (CH2)nOR (n = 2, 3), producing five- and/or six-membered ring lactones, have been investigated. Under such conditions, the regiochemistry of the reaction is governed by the cis or trans nature of the starting epoxy ester and also by its C(3) stereochemistry. An X-ray crystallographic structure of a γ-lactone