ASYMMERTIC SYNTHESIS OF Β-SUBSTITUTED α-AMINO ACIDS VIA A CHIRAL Ni(II) COMPLEX OF DEHYDROALANINE

Article abstract of DOI:10.1016/S0040-4020(01)86056-7

An efficient approach to the asymmetric synthesis of β-substituted (S)-alanines is describen.The chiral Ni(II) complex of a Schiff base derived from (S)-o-N-(N-benzylpropyl)aminobenzophenone (BBP) and glycine was treated with formaldehyde and sodium methoxide to give a corresponding (R)-serine complex which, in turn, was converted to the chiral Ni(II) dehydroalanine complex.Michael type base catalyzed addition of nucleophiles (including MeOH, Me2NH, PhCH2NH2, imidazole, PhSH, PhCH2SH,, malonic ester and benzylmagnesium chloride) produced a mixture of diastereoisomeric complexes with a 70-90percent excess of S,S (or L,L) isomers over the S,R (or L,D) ones.The cleavage of pure diastereoisomers with aqueous HCl gave, in good yields, β-substituted (S) (or L)-alanines and regenerated the chiral auxiliary (BBP).