Stereocontrolled synthesis of macrolide and polyether antibiotics is one of the most attractive areas in current synthetic organic chemistry. Recently, we planned to synthesize representative macrolide antibiotics and their aglycones such as methynolide (12-membered), picronolide (14-membered), erythronolide A (14-membered), and tylonolide (16-membered) from D-glucose by a common methodology. In the macrolide synthesis, macro-lactonization of active esters has been used, though often in poor yield. We report here that the Wittig-Horner cyclization was proved to give excellent results in the case of the synthesis of methynolide (30), tylonolide (33), and a model compound (35) of pironolide (14-membered). When esters having both aldehyde and keto-phosphonate groups, 28, 31, 34, were exposed to powdered anhydrous K_2CO_3 (6 eqv.) and 18-crown-6 (12 eqv.) in dilute toluene solution (1 mM) at 80℃ (several hrs.), the expected macro-cyclic enones, 29, 32, 35, were readily obtained in high yields.
