The synthesis of the small pseudopeptide Boc-L-Phe-D-Imz-OBn (Imz = imidazolidin-2-one-4-carboxylate) is reported. Crystallization of this peptide from methanol, ethanol, and isopropanol leads to isostructural solvates when the solvent is methanol or ethanol with a peptide/solvent ratio of 2:1 and to an unsolvated polymorph in the case of isopropanol. The solvate peptide crystallizes forming infinite chains with the monomers in parallel orientation connected by a single hydrogen bond. The chains are arranged in antiparallel direction and cross-linked through the NH group of the imidazolidin heterocycle with formation of a stable 2D network. Crystals from isopropanol form a different 2D network. The degree of order in the crystal assembly decreases from methanol and ethanol solvates to the unsolvated pseudopeptide grown from isopropanol. Quantum chemical calculations at the HF/6-31G* level of ab initio MO theory, carried out on the two different packings, show a slight preference for the unsolvated packing.

A network of small molecules connected by cross-linked NH bonds

ANGELICI, GAETANO;CONTALDI, SIMONE;FALINI, GIUSEPPE;MONARI, MAGDA;TOMASINI, CLAUDIA
2010

Abstract

The synthesis of the small pseudopeptide Boc-L-Phe-D-Imz-OBn (Imz = imidazolidin-2-one-4-carboxylate) is reported. Crystallization of this peptide from methanol, ethanol, and isopropanol leads to isostructural solvates when the solvent is methanol or ethanol with a peptide/solvent ratio of 2:1 and to an unsolvated polymorph in the case of isopropanol. The solvate peptide crystallizes forming infinite chains with the monomers in parallel orientation connected by a single hydrogen bond. The chains are arranged in antiparallel direction and cross-linked through the NH group of the imidazolidin heterocycle with formation of a stable 2D network. Crystals from isopropanol form a different 2D network. The degree of order in the crystal assembly decreases from methanol and ethanol solvates to the unsolvated pseudopeptide grown from isopropanol. Quantum chemical calculations at the HF/6-31G* level of ab initio MO theory, carried out on the two different packings, show a slight preference for the unsolvated packing.
G. Angelici; N. Castellucci; S. Contaldi; G. Falini; H.-J. Hofmann; M. Monari; C. Tomasini
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/83137
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