ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The molecular and crystal structures of one derivative and three homopeptides (from the di-to the tetrapeptide level) of the chiral, Cα, α-disubstituted glycine Cα-methyl, Cα-benzylglycine [(αMe)Phe], have been determined by x-ray diffraction. The derivative is mClAc-D-(αMe)Phe-OH, and the peptides are pBrBz-[D-(αMe)Phe]2-NHMe, pBrBz-[D-(αMe)Phe]3-OH hemihydrate, and pBrBz-[D-(αMe)Phe]4-OtBu sesquihydrate. All (αMe)Phe residues prefer φ,ψ torsion angles in the helical region of the conformational map. The dipeptide methylamide and the tripeptide carboxylic acid adopt a β-turn conformation with a 1 ← 4 C=O…H—N intramolecular H bond. The structure of the tripeptide carboxylic acid is further stabilized by a 1 ← 4 C=O…H—O intramolecular H bond, forming an “oxy-analogue” of a β-turn. The tetrapeptide ester is folded in a regular (incipient) 310-helix. In general, the relationship between (αMe)Phe chirality and helix screw sense is opposite to that exhibited by protein amino acids. A comparison is made with the conclusions extracted from published work on homopeptides from other Cα-methylated α-amino acids. © 1993 John Wiley & Sons, Inc.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360331011
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