SYNTHESIS AND NMR-STUDIES OF N-SUBSTITUTED DERIVATIVES OF KAINIC ACIDDIMETHYL ESTERS

Dimethyl kainate derivatives incorporating the amino protecting groups , 9-fluorenylmethoxycarbonyl (Fmoc), tert-butoxycarbonyl (Boc) and tri phenylmethyl (trityl, Trt), have been synthesized from (-)-alpha-kaini c acid 2-carboxy-4-(1-methylethenyl)-3-pyrrolidinylacetic acid] by mea ns of N-protection followed by esterification with methanol in the pre sence of triphenylphosphine and diethyl azodicarboxylate. Coupling of N-Fmoc protected 4-methylaminobenzoyl chloride with dimethyl kainate f ollowed by N-deprotection with piperidine provided dimethyl 1-(4-methy laminobenzoyl)kainate. The H-1 and C-13 NMR spectra of two of the comp ounds reveal the presence of two conformers due to restricted rotation around the amide bond. The H-1 and C-13 assignments of the four compo unds were carried out by one- and two-dimensional NMR techniques.