Syntheses of optically active alpha-amino nitriles by asymmetric transformation of the second kind using a principle of O. Dimroth

A mixture of solids A(s) and B-s in equilibrium with the dissolved compound s A(1) and B-1 is transformed completely into one pure solid, say B-s, if t he dissolved compounds A(1)reversible arrow B-1 are equilibrating in soluti on. This is applied to transform 1 : 1 mixtures of solid diastereomeric amy gdalates (2-hydroxy-2-phenylacetates; mandelates) (R,R)-3 + (S,R)-3 prepare d from racemic alpha-amino nitriles (R,S)-1 with (R)-mandelic acid 2 into s tereochemically pure single diastereomers (R,R)-3, or (S,R)-3 (de > 97%) (' asymmetric transformation of the second kind by application of Dimroth's pr inciple'). Decomposition of the amygdalates (R,R)-3, or (S,R)-3, with aqueo us base affords the enantiomerically pure alpha-amino nitriles (R)-1, or (S )-1 (ten examples). The chiral auxiliary (R)mandelic acid is recovered almo st quantitatively. The optically active alpha-amino nitriles are hydrolyzed to amides 6, and further to alpha-N-alkylamino acids 7. N-Benzylamino acid s 7 are hydrogenated to alpha-amino acids 8. Some of the optically active a lpha-amino nitriles 1 are reduced to optically active 1,2-diamines 9. In mo st cases, absolute configurations could be assigned by comparison of the sp ecific rotations observed with those of authentic compounds.