APPLICATION OF THE TERM RELATIVE ENANTIOSELECTIVITY AS USEFUL MEASURE FOR COMPARISON OF CHIRAL CATALYSTS, DEMONSTRATED ON ASYMMETRIC HYDROGENATION OF AMINO-ACID PRECURSORS

The application of the quotient ''relative enantioselectivity'' Q = q/q' in which q and q' are enantiomenc ratios R/S (or S/R) for two comparable cases of asymmetric synthesis experiments is recommended for comparison of two or more catalysts or other variables like solvents, substrates and cofactors. The importance of this term Q lies in the possibility to form and compare values of enantioselectivity over the whole range from 99,9 % ee (R) to 99,9 % ee (S) in a mathematically correct way and is demonstrated on multiple examples of asymmetric hydrogenation of partly new N-acyl-dehydroamino acid derivatives with a couple of catalysts [Rh(Ph-beta-glup)(COD)]BF4 1 and [Rh(Ph-beta-glup-OH)(COD)]BF4 2. Interesting inversions of Q could be discovered for changes of the type of substrate and in dependence of the polarity of solvents.