2-[(2-Ethoxy-3,4-dioxocyclobut-1-en-yl)amino]propanamide (N-alaninamidoamide of squaric acid ethyl ester) has been characterized structurally and spectroscopically by ab initio calculations and IR-LD spectroscopy of oriented crystals suspended in a nematic liquid crystal. The results are compared with single crystal X-ray structures illustrating the possibilities of this experimental approach to obtaining structural information as well as assigning IR bands.
A series of seven substituted tert-butyl esters of 2,3-diaryl-3-arylaminopropanoic acids has been synthesized, isolated, spectroscopically and structurally elucidated. An influence of the substituents on the spectroscopic characteristics and conformations is discussed using the data of the linear-polarized IR- (IR-LD), UV-spectroscopy and 1H-NMR. Theoretical quantum chemical calculations are carried out, with a view to explaining and supporting the experimental optical properties and the electronic structure. The stereoselective synthesis of the corresponding diastereoisomers is optimized, thus giving good yields (62-72%) and purity of the compounds
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