Synthesis and structural studies of 3-alkylamino-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides:: a new class of heterocyclic compounds with therapeutical promises.

3-Alkylamino-pyrido[4,3-e]-1-2,4-thiadiazine 1,1-dioxide represents a new class of heterocyclic compounds expressing important pharmacological properties. According to the position of the C=N double bond in the thiadiazine ring, this heterocyclic ring system may exist under three different tautomeric forms. By means of spectral and X-ray data collected from selected compounds, the most favourable tautomeric form adopted by 3-alkylamino-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides devoid of an alkyl substituent in the 2- or in the 4-position was determined. The present study giving new insights in the geometrical and conformational aspects of pyridothiadiazinedioxides is important considering the pharmacological potentialities of this class of heterocyclic compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.