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Crystal structure and molecular conformation of the peptide N-Boc-L-gly-dehydro-Phe-NHCH3

✍ Scribed by T. P. Singh; Punit Narula; V. S. Chauhan; Paramjeet Kaur

Publisher
Wiley (John Wiley & Sons)
Year
1989
Tongue
English
Weight
451 KB
Volume
28
Category
Article
ISSN
0006-3525

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✦ Synopsis

The peptide N-Boc-L-Gly-dehydro-Phe-NHCH, was synthesized by the combination of N-Boc-L-Gly-dehydro-Phe azlactone and pethylamine. Th? peptide crystalliqes in orthorhoybic space group P2,2121 with a = 5.679( 2) A, b = 16.423(9) A, c = 19.198(10) A, V = 1791(2) A3, 2 = 4, d m = 1.212(5) Mg m-,, dc = 1.237(1) Mg m-,. The structure was determined by direct methods using SHELXS 86. The structure was refined by full-matrix least squares procedure to an R value of 0.049 for 1509 observed reflections. The molecular dimensions are, in general, in good agreement with the standard values. The bond angle C"-CB-CY in the dehydro-Phe residue is 133.6(5)'. The peptide backbone torsion angles are 8' = -171.4(4)', a , , = 178.2(4)', = These values show that the backbone adopts the /%bend type I1 conformation. The Boc group has a trans-~ans conformation. The side-chain torsion angles in dehydro-Phe are xz = 1.6(9)',

~2 '

= 0.5(9)', and x$' = 179.8(6)'. The plane of q -C f -C : is rotated with respect to the plane of the phenyl ring at 0.5(6)', which indicates that the atoms of the side chain of the dehydro-Phe residue are essentially coplanar. As a result of the 8-bend in the structure, an intramolecular hydrogen bond is formed b e t w y n the oxygen of the ith residue and the NH of the (i + 3)th residue at a distance of 2.940(5) A. The crystal structure is stabilized by a network of hydrogen bonds and van der Waals interactions. -57.2(6)", = 141.2(4)', w1 = -174.4(4)', I & = 71.5(6)', $2 = 7.2(6)', and WZ = -179.8(5)'. *Supplementary material: hthg of observed and calculated structure factors for the N-Boc-L-Gly-dehydro-Phe-NHCH, peptide and other tables are available on microfiche. Please contact Journal Production Manager, John Wiley & Sons, Inc.

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