Heterocyclic antisecretory derivatives of the formula:
where D is O, S or NH; E is CH or when D is O or S, E is N; Y is S, O, CH 2 , SO or a direct bond; m is O to 4 and n is 1 to 4, provided that when Y is S, O or SO m is 1 to 4, and when Y is O or SO, n is 2 to 4; A is a chain of 3 or 4 atoms comprising at least one C and also optionally S, N, 2N, or N and S, and also comprising C=O or C=S or where possible S0 2 and chain optionally substituted by 1 or 2 C (1-6) alkyl, benzyl, naphthylmethyl, 2-phenethyl, 4-phenylbutyl, pyridylmethyl, thiazolylmethyl, thienylmethyl, benzyloxy, pyridylmethoxy or phenoxymethyl radicals each optionally substituted on the aromatic ring system by 1 to 3 halogen atoms or methyl, methoxy, trifluoromethyl, dimethylamino, phenyl or phenoxy radicals; and the salts thereof. A process for the manufacture of said compounds is described; e.g. 2-guanidino-4[(2-aminomethyl)-thiomethyl]-thiazole gives by reaction with 5-(4-chlorobenzyl)-2-methyl- thiopyrimid-4-one 5-(4-chlorobenzyl)-2-[2-(2-guanidinothia- zol-4-ylmethylthio)ethylamino]pyrimid-4-one.