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Abstract
The purpose of this investigation was the synthesis and study of the configuration of various 4-methyl-2-pyrrolidones and 3-methyl pyrrolidines. Then, by using the steric energies and coupling constants to figure out the Karplus-equation constant of 5-member ring heterocyclic compounds.
Initially, attempts were made to prepare a number of methyl-4-alkylamino-3-methyl-2-butenoates, stable as the hydrochloride, by the reaction of methyl-4-bromo-3-methyl-2-butenoate with a series of amines. The unsaturated amino ester was readily reduced to the corresponding methyl-4-alkylamino-3-methyl-butyrate hydrochloride. Methyl-4-t-butylamino-3-methyl-butyrate was hydrolyzed to 4-t-butylamino-3-methyl-butyric acid. When the hydrolyzation procedure was applied to methyl-4-cyclohexyl-3-methyl-butyrate, the desirable amino-acid, along with 2-pyrrolidone, was collected in a 1:2 ratio. When methyl-4-benzylamino-3-methylbutyrate was hydrolyzed, the only product was 1-benzyl-4-methyl-pyrrolidone.
1-Alkyl-4-methyl-2-pyrrolidones were obtained by vacuum distillation of the corresponding methyl-4-alkylamino-3-methylbutyrates which were initially refluxed under different conditions. The 3-methyl pyrrolidines were obtained by reducing the corresponding pyrrolidones in the presence of lithium aluminium hydride.
The coupling constants were checked by a computer simulation program named "NMR-SIM2". The steric energies were done by a computer program-QCPE No 395. An equation dealing with the relationship among the dihedral angle, coupling constant, steric energy and Karplus constant was derived. By setting "B" = 0 and "C" = 1.4, the Karplus constant parameter "A" was figured out by putting each data set into that equation. "A" is equal 8.9 in this study.
The ('13)C and ('15)N chemical shifts of pyrrolidones and pyrrolidines were determined. The coupling constants were calculated by using the available data and equations.
