alpha,beta-Dehydro-amino acid residues in the design of peptide structures: synthesis, crystal structure, and molecular conformation of two homologous peptides-N-Ac-dehydro-Phe-L-Leu-OCH3 and N-Ac-dehydro-Phe-NorVal-OCH3

Sharma, P.; Narula, P.; Singh, T.P.

Biopolymers 34(9): 1243-1249

1994


ISSN/ISBN: 0006-3525
PMID: 7948736
DOI: 10.1002/bip.360340912
Accession: 047993850

Download citation:  
Text
  |  
BibTeX
  |  
RIS

Article/Abstract emailed within 0-6 h
Payments are secure & encrypted
Powered by Stripe
Powered by PayPal

Abstract
The dehydro-residue containing peptides N-Ac-dehydro-Phe-L-Leu-OCH-3 (I) and N-Ac-dehydro-Phe-NorVal-OCH-3 (II) were synthesized by the usual workup procedures. The peptides crystallize from their solutions in methanol in space group P6-5: (I) a = b = 12.528(2) ANG , c = 21.653(5) ANG ; (II) a = b = 12.532(2) ANG , c = 21.695 (4) ANG . The structures were determined by direct methods. Both peptides adopt similar conformations with vphi, psi of dehydro-Phe as follows: (I) -57.0(5) degree and -37.0(5) degree ; (II) -56.0(5), degree and -37.5(5) degree . The observed data on dehydro-Phe when placed at the (it1) position show that the vphi,psi values of dehydro-Phe are either -60 degree , 140 degree or -60 degree , -30 degree . The conformation of -60 degree , 140 degree can be accommodated only with a flexible residue at the (i + 2) position while the vphi,psi values of -60 degree , -30 degree are obtained with a bulky residue at the (i+2) position as in the present structures. The molecules are packed in a helical way along the c axis. These are held by two strong intermolecular hydrogen bonds involving both NH as donors and acetyl group and dehydro-Phe oxygen atoms as acceptors.

alpha,beta-Dehydro-amino acid residues in the design of peptide structures: synthesis, crystal structure, and molecular conformation of two homologous peptides-N-Ac-dehydro-Phe-L-Leu-OCH3 and N-Ac-dehydro-Phe-NorVal-OCH3