Chemical modification and structure-activity relationships of pyripyropenes. 1. Modification at the four hydroxyl groups.

Four hydroxyl groups of pyripyropenes have been modified and evaluated for their ability to inhibit microsomal acyl-CoA:cholesterol acyltransferase (ACAT) activity in vitro and to lower cholesterol absorption in vivo in a cholesterol-fed hamster. 7-O-n-Valeryl derivative (8c) improved the in vitro ACAT inhibitory activity (IC50 = 13 nM) about 7 times better than pyripyropene A. Introduction of methanesulfonyl group at 11-hydroxyl group (17a) increased both in vitro activity (IC50 = 19 nM) and in vivo efficacy (ED50 = 10 mg/kg).