4 325 961 the compound of formula i or salt thereof may also be advantageously combined with an h 1 or h 2 receptor antagonist such as for instance cimetidine ranitidine terfenadine famotidine temelastine acrivastine loratidine utrizine tazifylline azelastine aminothiadiazoles disclosed in european patent 81102976 8 and like compounds such as those disclosed in u s pat no 4 283 408 4 362 736 4 394 508 and european patent application 40 696 the pharmaceutical compositions may also contain a k h atpase inhibitor such as omeprazole disclosed in u s pat no 4 255 431 and the like each of the references referred to in this paragraph is hereby incorporated by reference generally the scheme for the preparation of the compounds of formula i above is shown in scheme i and scheme ii as follows str7 the starting esters 1 are prepared as described in u s pat no 5 017 604 intermediate hydrazides may be prepared from the corresponding esters 1 by treatment with hydrazine at 0 u00b0 c to room temperature preferably anhydrous hydrazine in the absence of another solvent at room temperature for 5 to 30 minutes thiones 2 may be prepared from the hydrazides by treatment with a reagent such as carbon disulfide or thiophosgene or thiocarbonyldiimidazole in an alcohol solvent such as methanol or an ether solvent such as thf in the presence of an appropriate base such as naoh koh triethylamine imidazole and the like the reactions may be conducted at temperatures of 0 u00b0 c to the reflux temperature of the solvent for 30 minutes to overnight oxo derivatives 3 may be prepared from the hydrazides by treatment with a reagent such.