(ALKOXYALKYL)BORONIC ESTER INTERMEDIATES FOR ASYMMETRIC-SYNTHESIS

The use of boronic ester chemistry in the construction of synthetic in termediates containing two or three chiral centers corresponding to st eric relationships in the macrolide leuconolide has been explored. A f our-carbon chain with a substituent at each carbon has been built from each end, and the effects of different chiral directors and masking g roups have been compared. Exceptionally facile debenzylation of a benz yloxy group separated by four carbon atoms from a boronic ester functi on has been observed and may account for the failure of earlier attemp ts to synthesize sugars via analogous chemistry. A novel method of red ucing alpha-chloro boronic esters to alkylboronic esters with sodium h ydride in DMSO has been found.