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 c lass of heterocyclic compounds expressing important pharmacological propert ies. According to the position of the C=N double bond in the thiadiazine ri ng, this heterocyclic ring system may exist under three different tautomeri c forms. By means of spectral and X-ray data collected from selected compou nds, 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 reserv ed.