0000000000380553
AUTHOR
Agnieszka Macedowska-capiga
Thecis-transisomerization ofN-methyl-α,β-dehydroamino acids
Dehydroamino acids with the methylated N-terminal peptide group occur in natural small cyclic peptides. The structural analysis was used to investigate the cis-trans isomerization of the N-terminal tertiary amide group of diamides: Ac-(Z)-Δ(Me)Abu-NHMe (1), Ac-(Z)-Δ(Me)Phe-NHMe (2), Ac-(E)-Δ(Me)Phe-NHMe (3), Ac-Δ(Me)Ala-NHMe (4), and Ac-(Me)Ala-NHMe (5). The compounds were analyzed in the solid state by an X-ray crystallography (1-3), and in the solution by FTIR (MeCN and CHCl(3) ) and NMR (DMSO-d6 and CDCl(3) ) methods (1-5). In the solid state, the studied compounds adopt the cis configuration of N-terminal amide. In solution, this configuration also prevails for the dehydroamino acids 1-…
The conformation cis of N-acetyl-N-methyl-α,β-dehydroalanine N′-methylamide and saturated analogues
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…
N-Methyldehydroamino acids promote a configuration cis of N-methylamide bond
Abstract Dehydroamino acids with a methylated N-terminal tertiary amide bond occur in natural small cyclic peptide toxins. To investigate their conformational preferences a systematic theoretical analysis was performed on N ′-methylamides of N -acetyl- N -methyldehydroamino acids (Ac-Δ(Me)Xaa-NHMe, where Xaa = ( Z )-Abu, ( E )-Abu, Val, ( Z )-Phe, and ( E )-Phe) considering the configuration trans and cis of the tertiary amide bond. The ϕ , ψ potential energy surfaces were calculated at the B3LYP/6-31+G ∗∗ //HF/3-21G level with inclusion of the solvent (water) effect (SCRF method). The conformers localised were fully optimised at the B3LYP/6-31+G ∗∗ in vacuo. The accessible areas of the pot…
CCDC 862034: Experimental Crystal Structure Determination
Related Article: Dawid Siodłak, Agnieszka Macedowska-Capiga, Małgorzata A. Broda, Anna E. Kozioł, Tadeusz Lis|2012|Biopolymers|98|466|doi:10.1002/bip.22082
CCDC 862033: Experimental Crystal Structure Determination
Related Article: Dawid Siodłak, Agnieszka Macedowska-Capiga, Małgorzata A. Broda, Anna E. Kozioł, Tadeusz Lis|2012|Biopolymers|98|466|doi:10.1002/bip.22082
CCDC 862035: Experimental Crystal Structure Determination
Related Article: Dawid Siodłak, Agnieszka Macedowska-Capiga, Małgorzata A. Broda, Anna E. Kozioł, Tadeusz Lis|2012|Biopolymers|98|466|doi:10.1002/bip.22082