Synthesis of optically active α-monobenzoyl glycerol by asymmetric transesterification of glycerol

Efficient asymmetric synthesis of optically active α-monobenzoyl glycerol (α-MBG) was examined by enzymatic transesterification of vinylbenzoate with glycerol in organic solvents. Optical purity and absolute configuration of the synthesized α-MBG could be easily determined with HPLC after derivatization to solketal benzoate by reacting with camphorsulfonic acid and acetone dimethylacetal. 1,4-Dioxane was selected to be the most suitable solvent in which glycerol is soluble. Although almost enzymes lost their activity in 1,4-dioxane, lipases immobilized on macroporous resin catalyzed the synthesis of optically active α-MBG. By using the carrier-fixed CHIRAZYME L-2, the reaction conditions, such as substrate concentrations, reaction temperature, and acyl donor, were optimized. Under the optimized condition, (R)-α-MBG having 54% e.e. was synthesized with 94% yield on a multigram-scale, and its optical purity was brought up to over 95% by one recrystallization.