‘Chiron’ approach to the total synthesis of macrolide (+)-Aspicilin

Abstract

An efficient total synthesis of 18 membered macrolactone, (+)-Aspicilin (lichen macrolide) has been achieved in 12 linear steps with 10.2% overall yield from carbohydrate based building block D-glucal. Highlights of the strategy include preparation of 2-deoxysugar from protected glycal 14, two-carbon Wittig olefination of the Swern oxidised intermediate 7, union of ‘carbohydrate based’ fragment 5 and a long chain (C-11) chiral alcohol 6 by Yamaguchi esterification and finally ring closing metathesis of the resulting compound 4.