Axially chiral amino acid derivatives were synthesized via a selective single-step monoesterification of 1,1′-binaphthyl-2,2′-dicarboxylic acids. In the presence of Ag2CO3, the alkylative monoesterification of a 1,1′-binaphthyl-2,2′-dicarboxylic acid with an alkyl halide proceeded selectively in a single operation. Curtius rearrangement of the monomethyl ester and successive alcoholysis of the corresponding isocyanate afforded the N-protected binaphthyl amino acids.
Key words
unnatural amino acid - monoesterification - half-ester - biaryl - axial chirality