NMR-STUDIES OF BUSPIRONE (AN ANXIOLYTIC DRUG) ANALOGS

Conformations of piperazine rings in iperazinyl]butyl}-8-azaspiro[4.5] -decane-7,9-dione (buspirone - 1) and its two analogues iperazinyl]but yl}-8-azaspiro[4.5]-decane-7,9-dione (kaspar - 2) and inolinyl)-1-pipe razinyl]butyl}-2,6-piperidinedione (mesmar - 3) (Fig. 1) have been stu died with the aid of H-1 NMR and C-13 NMR spectra. For free bases the two bands corresponding to piperazine hydrogen atoms in the spectra br oaden considerably with a decrease in temperature to divide into four separate bands, indicating the presence of a dynamic exchange process. A similar dynamic process, but for higher temperatures, was observed for buspirone (1), kaspar (2) and mesmar (3) hydrochlorides. Proton an d carbon atom resonance lines have been assigned with the aid of 2D CO SY and 2D HETCOR two-dimensional spectra.