Search results for "Single crystal structure analysis"
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Molecular and crystal structure of Ac-(Z)-ΔAbu-NMe2 and Ac-DL-Abu-NMe2 as compared to those of related molecules
2004
Abstract The molecular and crystal structures of two homologous amino acid derivatives: N-acetyl-α,β-dehydro-butyrine N´,N´-dimethylamide (1) and N-acetyl-DL-butyrine N´,N´-dimethylamide (2), have been determined by X-ray crystallography. Similar solid-state association of both compounds is observed; despite different molecular conformation, they form centrosymmetric dimers linked by the intermolecular N–H…O hydrogen bonds. The conformation of two crystallographically independent molecules of 1 [with torsion angles ϕ, ψ, χ 1 ≈ (–47°, 130°, 3°), respectively] is also characteristic of other related diamides – ΔAla, ΔPhe and ΔLeu – previously studied in the solid state. To analyse whether thi…
The conformation cis of N-acetyl-N-methyl-α,β-dehydroalanine N′-methylamide and saturated analogues
2007
A series of three homologous amino acids derivatives: N-acetyl-N-methyl-α,β–dehydroalanine N′-methylamide (1), N-acetyl-N-methyl-L-alanine N′-methylamide (2), and N-acetyl-N-methyl-DL-alanine N′-methylamide have been synthesised. The racemic species undergoes spontaneous separation into L and D-enantiomers. From these two chiral forms, the structure of L-enantiomer (3) was analysed. The molecules of 1 – 3 adopt the cis arrangement of the N-terminal amide bond. The molecular conformations are similar for 1 (φ, ψ = 94.6(1)°, −1.7(1)°) and 3 (φ, ψ = 111.5(1)°, −23.8(1)°), and also 2 (φ, ψ = −114.8(2)°, 29.5(2)°), if inversion through the chiral C2 carbon is considered. They are stabilised by i…