NEW MATERIAL:2-( 10,11-Dihydro-8-hydroxy-11-oxodibenzo[b,f]thiepin-2-yl )- propionic acid of formula I and its non-toxic salt.

USE: Antiphlogistic agent.

PROCESS: The compound I is prepared by heating and refluxing a compound II (R1 is lower alkyl; R2 is NH2 or OH) in water or other solvent, in the presence of an acid which is sufficiently strong to hydrolyze the alkoxy group, e.g. hydrobromic acid, tribromo- boric acid, etc., for several hours. The compound II can be prepared, e.g. by (1) reacting a compound III with a compound IV (one of A and B is halogen and the other is SH), (2) reducing the acetyl group of the resulting compound to hydroxyethyl group, and (3) subjecting the product to halogenation, cyanation, esterification, cyclization, and if necessary, hydrolysis.