ASYMMETRIC-SYNTHESIS BY REDUCTION OR BY OXIDATION OF PROCHIRAL SUBSTRATES ABSORBED INTO CHIRAL POLYMER SUPPORTS

Prochiral ketones absorbed into chiral polymer supports were reduced w ith aqueous potassium borohydride. 2-Substituted naphthoquinones absor bed into chiral polymer supports were epoxidized using aqueous alkalin e hydrogen peroxide. In both systems asymmetric synthesis was achieved . Best results were obtained with microcrystalline cellulose triacetat e as the polymer support: 8.6% ee in a reduction, 4.5% ee in an epoxid ation. Use of tetra-n-butylammonium bromide as a phase transfer cataly st tended to improve chemical yields and ees. The potential of this ty pe of approach in asymmetric synthesis is discussed.