Synthetic studies towards novel tris-oxazole based macrolides of marine origin. Stereocontrolled synthesis of the C20C35 fragment in ulapualide A

Abstract

The C20C35 subunit 3 in ulapualide A 1 has been synthesised in enantiomerically pure form using a combination of the Evans aldol reaction, controlled ring opening reactions of chiral epoxides, and Brown's asymmetric allylboration reaction, to set up the eight chiral centres in the key intermediates 4 and 5 . An olefination reaction between 4 and 5 , followed by hydrogenation of 23 , and protection of the resulting alcohol 24 then led to 3 . Graphic