Synthesis of optically active alpha-methyl beta-hydroperoxy esters by diastereoselective singlet oxygen ene reaction and horseradish peroxidase catalyzed kinetic resolution

Optically active diastereomeric beta-hydroperoxy eaters 4 have been prepare d by singlet oxygen ene reaction of beta,gamma-unsaturated esters 3 and sub sequent horseradish peroxidase (HRP) catalyzed kinetic resolution of the en e product. The highest enantiomeric excess (up to 95%) has been obtained fo r the isopropyl ester threo-4c, which establishes that the size of the remo te ester functionality exercises appreciable control in the enantioselectiv ity of the enzymatic kinetic resolution.