Abstract: The invention relates to a novel process for preparing 1-[/2S/-methyl-3-mercaptopropionyl]-pyrrolidine-/2S/-carboxylic acid of the formula I ##STR1## in which 1-[/2S/-methyl-3-thiocyanatopropionyl]-pyrrolidine-/2S/-carboxylic acid of the formula II ##STR2## is dissolved in an aqueous mineral acid, the solution obtained is diluted with water and the 1-[/2S/-methyl-3-carbamoylthiopropionyl]-pyrrolidine-/2S/-carboxylic acid of the formula III ##STR3## that forms is hydrolized with an aqueous solution of a base.

Abstract: The invention relates to a novel process for preparing 1-[(2S)-3-mercapto-2-methyl-1-oxopropyl]-L-proline (captopril) of formula (I). ##STR1## which comprises hydrogenolysing 1-[(2S)-2-methyl-1-oxo-3-rhodanidopropyl]-L-proline of formula (II) ##STR2## in an inert solvent, in the presence of a catalyst, at a temperature of 50.degree. to 120.degree. C. under a pressure of 10.sup.5 to 10.sup.7 Pa.The above compound of formula (II) is new and can be prepared by acylating L-proline with a reactive acylating derivative of (2S)-2-methyl-3-rhodanido-propionic acid of formula (III).

Abstract: The invention relates to novel pyrazolo[1,5-c]quinazoline derivatives of the general formula I ##STR1## wherein R represents a hydrogen atom, a C.sub.1-4 alkyl group or an acyl group,R.sub.1 represents a hydrogen atom, a C.sub.1-12 alkyl group, a C.sub.3-8 cycloalkyl group, a C.sub.2-4 alkenyl group, an aralkyl group, wherein the alkyl group has 1 to 4 carbon atoms, a phenylalkenyl group, wherein the alkenyl group has 2 to 4 carbon atoms, furthermore a carboxy group or a phenyl group optionally substituted by one or more substituents selected from the group consisting of halogen, hydroxy, C.sub.1-4 alkoxy, nitro or di(C.sub.1-4 alkyl)amino groups, orR and R.sub.1 may form together a valence bond,R.sub.2 represents a hydrogen atom, a C.sub.1-4 alkyl or a phenyl group, orR.sub.1 and R.sub.2 may form together a C.sub.2-7 alkylene group,R.sub.