Stereoselective synthesis of erythronolide a by extremely efficient lactonization based on conformational adjustment and high activation of seco-acid1

Abstract C1-C5 sulfone (11) and C7-C15 aldehyde (20), synthesized stereoselectively from D- glucose, were coupled, and the C5 and C6 chiral centers were constructed taking advantage of the MPM (4-methoxybenzyl) type protecting group to give the seco-acid (7), which has 9,11-and 3,5- diols protected as the mesityl- and DMP (3,4-dimethoxyphenyl) acetals, respectively. When Yamaguchi's mixed anhydride of 7 was treated with a high concentration of DMAP at room temperature, a very rapid cyclization occurred and the 14-membered lactone (8) was isolated in almost quantitative yield. Deprotection of 8 readily gave 9-dihydroerythronolide A (2), which was converted to the title compound (1).