studies on the conformation of amino acids. V. Conformation of amino acids with δ-atoms

Abstract

Preferred conformations of the backbone and side-chain of the amino acids, norvaline, leucine, phenylalanine, tyrosine, tryptophan, and histidine obtained by calculating the energies of conformations are reported. The conformations of non-aromatic side groups are restricted to only certain values of χ¹ and χ², and the backbone conformation is the same as shown for aminobutyric acid having a single γ-methyl group. The aromatic side groups prefer a perpendicular orientation about the bond Cβ-Cγ and deviations from this orientation are characteristic of the position of the γ-atom. The experimentally observed conformations of amino acids with S-atoms and aromatic groups in the side-chain are compared with the theoretical predictions and the agreement is found to be excellent.