Zusammenfassung
In the hydrogenation of the C=N double bonds of the pyrazine ring of folic acid to 5,6,7,8-tetrahydrofolic acid a new asymmetric center is formed at C6 of the pteridine system. With rhodium(r) catalysts made from optically active phosphanes, which are immobilized on silical gel, the hydrogenation in aqueous solution can be controlled stereoselectively. The highest diastereomeric excess of ca. 40% ...
Zusammenfassung
In the hydrogenation of the C=N double bonds of the pyrazine ring of folic acid to 5,6,7,8-tetrahydrofolic acid a new asymmetric center is formed at C6 of the pteridine system. With rhodium(r) catalysts made from optically active phosphanes, which are immobilized on silical gel, the hydrogenation in aqueous solution can be controlled stereoselectively. The highest diastereomeric excess of ca. 40% is obtained with (-)-BPPM containing catalysts. The hydrogenation of the biomolecule folic acid in aqueous solution is also possible homogeneously with rhodium(I)phosphane catalysts, the ligands of which contain sulfonic acid groups and polyether fragments. The homogeneous hydrogenations proceed slower and with somewhat reduced diastereoselectivities compared to the heterogeneous catalyses. The hydrogenation of 2-methylquinoxaline is a model system for the reduction of folic acid. The usual rhodium(I)-phosphane catalysts afford only small enantioselectivities.
Altmetric