Stereoretentive C-H bond activation in the aqueous phase catalytic hydrogenation of amino acids to amino alcohols.

[reaction: see text] At 100 degrees C and 1000 psi of hydrogen, aqueous l-alanine undergoes facile hydrogenation to l-alaninol over a 5% Ru/C catalyst. In the presence of added acid to protonate the carboxylate moiety, the reaction is faster and more selective than analogous reductions of simple alkanoic acids. Stereochemistry at the alpha-carbon is retained despite complete exchange of hydrogen at this site, as shown by deuterium incorporation. Similar stereoretentive C-H bond activation at C2 is seen in l-alaninol itself, and when acid is omitted, in l-alanine. These processes reveal a class of mild, highly stereoretentive C-H bond activations occurring in water over a heterogeneous catalyst.