Crystal and molecular structure of N‐acetyl N‐hydroxy α‐amino acids

Abstract

The crystal and molecular structures of racemic (DL) N‐acetyl‐N‐hydroxyvaline and 2‐(N‐acetyl‐N‐hydroxyamino)butyric acid have been determined from three‐dimensional X‐ray data. The crystals of both compounds are monoclinic, space group P21/a. The molecular conformation of these amino acid derivatives is similar, as far as the Φ torsion angle is concerned, but the ψ values are significantly different. In the crystal structures of both compounds, two series of intermolecular hydrogen bonds (HB's) are present: NOH…O  COH HB's link the N‐hydroxy and carboxylic groups, while OCOH…OCN HB's link the carboxylic and N‐hydroxyamidic groups.

Structure–Property Relationship Study of N-(Hydroxy)Peptides for the Design of Self-Assembled Parallel β-Sheets

“…Therefore, we hypothesized that by intercalating α-amino acids in such peptoids, sturdy N -(hydroxy)­peptoid–peptide β-sheet hybrids (e.g., 2 , Figure ) could potentially be generated. Given the important acidity of N -(hydroxyl)­amides in comparison to typical amide groups, we became interested in evaluating their hydrogen-bond donor/acceptor abilities to form β-sheets. N -(hydroxy) and N -(alkoxy)­peptoids are known to preferentially adopt a trans-conformation, which is also appropriate to the design of novel β-sheet tertiary structures.…”

tBuCO-ψ[CO-N(OH)]-Gly-NHiPr

“…There are only a small number of crystal structures of Nhydroxy peptides reported in the literature (Buseti, Ottenheijm, Zeegers, Ajo & Casarin, 1987;Dupont, Lecoq, Mangeot, Aubry, Boussard & Marraud, 1993) and the possible intra-or intermolecular interaction modes of the N-hydroxyl group need to be specified. By slow evaporation of a methanol solution, we have obtained single crystals of the title compound, (I), deriving from N-hydroxyglycine.…”