# Structures of Pivaloyl-L-prolyl-N-methyl-D- phenylalaninamide and Pivaloyl-L-prolyl-N-methyl-D-valinamide

Bardi, R and Piazzesi, AM and Toniolo, C and Sen, N and Balaram, H and Balaram, P (1988) Structures of Pivaloyl-L-prolyl-N-methyl-D- phenylalaninamide and Pivaloyl-L-prolyl-N-methyl-D-valinamide. In: Acta Crystallographica Section C: Crystal Structure Communications, 44 (11). pp. 1972-1976.

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## Abstract

$C_{20}H_{29}N_3O_3$ (Piv-L-Pro-D-Phe-NHMe, 1; Piv, pivaloyl and NHMe, methylamino): $M_r$ = 359.4, monoclinic, $P2_1$, a = 11.615 (3), b = 14.701(3), c = 5.912 (3) A, \beta = 98.04(10) deg, V = 999.6 (6) $A^3$, Z = 2 , $D_x$ = 1.194, $D_m$ = l.19g ${cm}^-3$, \lambda(Mo K\alpha) = 0.71069 A, \mu = 0.756${cm}^-1$, F(000) = 388, T = 297 K. $C_{16}H_{29}N_3O_3$ (Piv-L-Pro-D-Val-NHMe, 2): $M_r$ = 311.4, orthorhombic, ${P2}_12_12_1$, a = 17.868 (3), b = 16.062 (3), c = 6.183(3) A, V = 1774.5 (9) $A^3$, Z = 4, $D_x$ = 1.166, $D_m$ = 1.16 g ${cm}^-3$, \lambda = 0.71069 A, \mu = 0.756 ${cm}^-1$, F(000) = 680, T = 297 K. Final R values: 0.047 for 1613 observed [I \geq 3\sigma(I)] reflections of (1) and 0.079 for 1102 observed [I \geq 3\sigma(I)] reflections of (2). The backbone conformation and crystal packing motif of the two compounds are similar and typical of Piv-L-Pro-D-Xxx-NHR terminally-blocked heterochiral dipeptides. In particular, the structure is folded at the L-Pro-D-Xxx sequence to form a type-II \beta-bend stabilized by a 4 \rightarrow 1 intramolecular N-H...O=C H-bond between the methylamide N-H and pivaloyl C=O groups.

Item Type: Journal Article http://dx.doi.org/10.1107/S0108270188007... Copyright for this article belongs to International Union of Crystallography. Division of Biological Sciences > Molecular Biophysics Unit 16 Feb 2005 19 Sep 2010 04:18 http://eprints.iisc.ernet.in/id/eprint/2813