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Crystal structure of dehydromonopetide, (Z)‐ N ‐acetyl‐α,β‐dehydrophenylalanine methylamide
Author(s) -
Aubry A.,
Allier F.,
Boussard G.,
Marraud M.
Publication year - 1985
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360240405
Subject(s) - chemistry , monoclinic crystal system , vicinal , crystallography , stereochemistry , hydrogen bond , molecule , amide , double bond , crystal structure , degree of unsaturation , crystal (programming language) , peptide bond , peptide , biochemistry , organic chemistry , computer science , polymer chemistry , programming language
The crystal structure of (Z)‐acetyl‐α,β‐dehydrophenylalanine methylamide (monoclinic Cc, a = 10.241(1), b = 15.252(1), c = 8.643(1) Å, β = 120.98(1)°, Z = 4) has been solved by x‐ray diffraction to an R ‐factor = 0.148, and compared to that of the homologous L ‐phenylalanine dervative. Molecules are intermolecularly hydrogen‐bonded to four neighboring molecules in a three‐dimensional network with alternating layers of interacting amide bonds and orthogonally arranged phenyl rings. The existence of the C α = C β double bond results in a phenyl orientation that is forbidden for phenylananine (χ 1 = −7,8°), and in shorter C α − C β and C β − C γ distances. The geometrical paramenters of the peptide backbone are not drastically modified by α,β‐unsaturation. However, the N‐C α ‐C′ angle is increased by nearly 5°, and the dimensions, and therefore probably the electronic conjugation, of the N‐terminal amide group to be affected by the occurrence of the vicinal C α = C β double bond.