POLYMERIC SURFACTANT SYSTEMS IN THE ASYMMETRIC HYDROGENATION OF AMINO-ACID PRECURSORS WITH A RHODIUM COMPLEX

The synthesis of new types of soluble and insoluble amphiphilic system s is described, being polysoaps, crosslinked polysoaps, an amphiphilis ed ion exchanger, and ion exchangers loaded with ionic surfactants. It was possible to synthesise insoluble polymeric systems which neverthe less showed micellar properties. The polymers were tested as aids in t he stereospecific hydrogenation of (Z)-methyl alpha-acetamidocinnamate to the methyl ester of N-acetylphenylalanine (R) by means of an optic ally active rhodium complex in water. With linear polysoaps the effect on the reaction was dependent on the structure of the soap molecules. The enantioselectivity of the reaction with monomeric surfactants in water was almost attained. Crosslinked polysoaps showed the same effec ts on the hydrogenation as linear polysoaps with an analogous structur e. Macromolecular ion exchangers loaded with amphiphilic counterions g ave in hydrogenation almost the same effect as these counterions give when they are not bound to an insoluble carrier. Enantioselectivities and reaction rates were usually slightly lower than with monomeric sur factants. However, there is an advantage in the separation of catalyst and product after reaction. It was shown that the rhodium-containing amphiphilic ion exchangers could be reused for up to 9 times.