ChemInform Abstract: Practical Resolution of an Atropoisomeric α,α-Disubstituted Glycine with L-Phenylalanine Cyclohexylamide as Chiral Auxiliary.

l-Phenylalanine cyclohexylamide has been used as a chiral auxiliary for the medium-scale resolution of 2′,1′:1,2;1″,2″:3,4-dinaphthcyclohepta-1,3-diene-6-amino-6-carboxylic acid (Bin), an α,α-disubstituted glycine with only axial dissymmetry. Coupling of X–Bin–OH (X=Ac; Bz) with H–(l)-Phe–NH–C6H11 by the EDC/HOBt method gave the dipeptide diastereoisomers X–(R)-Bin–(l)-Phe–NH–C6H11 and X–(S)-Bin–(l)-Phe–NH–C6H11, which were separated by crystallization (X=Bz) and/or chromatography. Extensive acidic hydrolysis, followed by esterification of the resulting free amino acid enantiomers, led to enantiomerically pure (−)-(R)-H–Bin–OMe and (+)-(S)-H–Bin–OMe with high yields.