Hydrogenation of cinchona alkaloids over supported Pt catalyst.

The heterogeneous catalytic hydrogenation of two isomeric cinchona alkaloids, cinchonidine and cinchonine, was studied over Pt/Al2O3 in 1N H2SO4 solution under 100 bar H2 at 25°C. Cinchonidine was transformed into two diastereomeric hexahydroderivatives by hydrogenation of ring A (with N) of the quinoline moiety (yield over 95%, diastereomeric ratio 2/3), whereas hydrogenation of cinchonine resulted in the formation of three products, the major one being formed by the hydrogenation of ring B (without N) (yield 60%). The isolated hexahydroderivatives were investigated by 1H-, 13C-NMR, 1H-1H COSY, 1H-13C HetCOSY, and NOESY spectroscopy and were used as modifiers in the heterogeneous enantioselective hydrogenation of ethyl pyruvate and as catalysts in the Michael addition of ethyl 2-oxocyclopentanecarboxylate to methyl vinyl ketone. Chirality 15:S82–S89, 2003. © 2003 Wiley-Liss, Inc.