Conformational preference for the (oxiran-2-ylmethyl 3-oxobutanoate)(11)(β-ketoester) was studied using theoretical calculation and experimental data to demonstrate the influence of the conformation on the absence of intramolecular cyclization reaction to produce butyrolactones. Transition state structure was obtained from theoretical calculation, it can be observed that the β-ketoester (CH3COCH2COO-R) moiety changes its conformation from ...