Structural versatility of peptides containing C alpha, alpha-dialkylated glycines: conformational energy computations, i.r. absorption and 1H n.m.r. analysis of 1-aminocyclopropane-1-carboxylic acid homopeptides.
Conformational energy computations on the 1-aminocyclopropane-1-carboxylic acid mono-, di-, and tripeptide amides, Ac-(Ac3c)n-NHMe (n = 1-3), indicate that this C alpha, alpha-dialkylated, cyclic alpha-amino acid residue is conformally restricted and that type-I(I') beta-bends and distorted 3(10)-helices are particularly stable conformations for the di- and tripeptide amides, respectively. The results of the theoretical analysis are in agreement with those obtained in an i.r. absorption and 1H n.m.r. investigation in chloroform solution of Ac3c-rich tri- and tetrapeptide esters. A comparison is also made with the conclusions extracted from our previous work on peptides rich in Aib (alpha-aminoisobutyric acid), Ac5c (1-aminocyclopentane-1-carboxylic acid), and Ac6c (1-aminocyclohexane-1-carboxylic acid).
Crisma
M
M
Department of Organic Chemistry, University of Padua, Italy.
Bonora
G M
GM
Toniolo
C
C
Barone
V
V
Benedetti
E
E
Di Blasio
B
B
Pavone
V
V
Pedone
C
C
Santini
A
A
Fraternali
F
F
D000478:Alkylation; D000596:Amino Acids / Q000737:chemistry*; D000598:Amino Acids, Cyclic; D005998:Glycine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D009842:Oligopeptides; C023863:1-aminocyclopropane-1-carboxylic acid; D005998:Glycine