A preparative method for the synthesis of a series of 1-R-4-hydroxy-2,2-dioxo-1H-2λ 6 ,1-benzothiazine- 3-carboxylates has been developed. The special features of the steric structure for compounds of this class have been studied on the example of the 1-N-methyl derivative. Results of studying the analgesic properties of the substances obtained are given. Chemical modification is the simplest and the most widely applied means of improving the pharmacological and pharmaceutical properties of biologically active substances (1, 2). This is generally accepted and became quite common for the medicinal chemistry methodology used by us fairly successfully for the optimization of several lead structures discovered among numerous derivatives of 4-hydroxyquinolin-2-ones (3-7). An interesting extension of the studies in this direction is the replacement of carbonyl in position 2 by a sulfonyl group, i.e., the transition from 4-hydroxyquinolin-2-ones to 4-hydroxy-2,1-benzothiazine 2,2-dioxides. There are numerous examples of similar modifications reported in the literature (8, 9), including that with excellent biological results (10, 11). The variously substituted 2,2-dioxo-2,1-benzothiazines (sulfostyrils) act as test objects in this study. Up until now, only their 4-hydroxy derivatives remain outside the field of vision for investigators. We have attempted to fill the gap by planning to carry out a set of synthetic and biological work according to designated themes. The results of the first of them, devoted to 1-R-4-hydroxy-2,2-dioxo-1H-2λ 6 , 1-benzothiazine-3-carboxylates 1, are given in the present communication. The synthesis of the desired alkyl-2,1-benzothiazine-3-carboxylic acids 1 was achieved by a route analogous to the preparation of the quinoline analogs (12), with only difference that upon acylation of methyl anthranilates 2 we used alkyl chlorosulfonylacetates instead of alkyl malonyl chlorides (13). This initial step was a common synthetic procedure and was not distinguished by any special features. The sulfanilides 3 obtained were subjected directly to heterocyclization step, although if necessary it is possible to isolate them in a pure state and characterize (see Experimental for details).