The effect of N-substituent on the relative thermodynamic stability of unionized and zwitterionic forms of α-diphenylphosphino-α-amino acids

Abstract

© 2020 The relative thermodynamic stability of unionized and zwitterionic forms of α-phosphino-α-amino acids is governed by the substituent R at the nitrogen atom, namely, (het)aryl substituents favour the formation of the unionized form RHNCH(PPh2)COOH, while in the case of alkyl analogues the zwitterions RH2N+CH(PPh2)COO− predominate. The experimentally observed trends have been supported by quantum-chemical calculations. The synthesis and X-ray crystal structure analysis of a new unionized α-phosphino-α-amino acid [α-diphenylphosphino-N-(2-methoxycarbonylphenyl) glycine] are reported.