The preparation of unsymmetrical diglycerides

Abstract

Racemic 1,2-di-O-acylglycerols containing stearic and palmitic acids were prepared from 1,2-di-O-acyl-3-O-2′-tetrahydropyranylglycerols by hydrolysis of the tetrahydropyranyl group with boric acid. The 1,2-di-O-acyl-3-O-2′-tetrahydropyranylglycerols were obtained by acylation of 3-O-2′-tetrahydropyranylglycerol which was prepared from glycerol 1,2-carbonate. Enzymic hydrolysis of the 1,2-di-O-acyl-3-O-2′-tetrahydropyranyl-glycerols with pancreatic lipase gave 2-O-acyl-3-O-2′-tetrahydropyranylglycerols which were reacylated with a different fatty acid and hydrolysed to give “mixed acid” diglycerides. The method should be general for the preparation of 1,2-di-O-acyl-L-glycerols containing any mixture of long-chain acyl groups (saturated or unsaturated) using L-glycerol 1,2-carbonate as a starting material. The latter compound was synthesised from 3-O-benzyl-L-glycerol. The hydrolysis of racemic 1-O-hept-1′-enyl-2,3-di-O-palmitoylglycerol with pancreatic lipase gave 1-O-hept-1′-enyl-2-O-palmitoylglycerol, a “plasmaloge nicdiglyceride” suitable as an intermediate for the synthesis of plasmalogens.