ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The molecular structure of three protected AzaPro-containing peptides have been determined by x-ray diffraction: Z-AzaPro-NHiPr (1; Z: benzyloxycarbonyl), Z-AzaPro-L-Ala-NHiPr (2), and Boc-L-Ala-AzaPro-NHiPr (3; Boc: tert-butyloxycarbonyl). Starting from the key synthon benzyl-azaprolinate, compounds 1, 2, and 3 have been prepared by combined use of liquid phase peptide synthesis method and adequate isocyanates. In all peptides, the following geometric characteristics are retained: (a) pyramidal character of the two nitrogen atoms of the pyrazolidine ring; (b) pseudo cis conformation of the urethane (1, 2) or tertiary amide (3) function preceding the AzaPro residue; (c) identical absolute values of the Azaproline residue torsion angles “φ, ψ” respectively 111° and 23°. In compound 2, the two nitrogen atoms of the pyrazolidine ring are R, R but the opposite S, S absolute configurations are observed in compound 3. In the crystal, compound 3 adopts a folded structure similar to a type VI β-turn with a weak intramolecular i + 3 → i hydrogen bond, while an extended structure is observed in compound 2. In the light of our findings, in a peptide chain and contrary to the Pro residue, an AzaPro residue should prevent the formation of any type of any type of β-turn with the residue following it but could accommodate a folded structure with a pseudo type VI βturn with the preceding residue. If confirmed, this would be of tremendous importance in the design of biologically active peptides and drugs. © 1993 John Wiley & Sons, Inc.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360330707
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