Abstract: Peptides and pharmaceutically acceptable salts thereof of the following formula are provided ##STR1## wherein R is selected from the group consisting of Leu, Ile and Val,X is from zero to four amino acids,Y is from zero to four amino acids, andZ is OH or NH.sub.2.The compounds are useful in inhibiting thrombin- and plasmin-induced aggregation of human platelets.

Abstract: Compounds of formulaR.sup.1 CO--NH--CH(R.sup.2)--CONH--CH(R.sup.3)--X[wherein:R.sup.1 represents alkyl having an .alpha.-amino or protected .alpha.-amino substituent and an aryl, heterocyclic or heterocyclic-dithio substituent;R.sup.2 represents a variety of aliphatic and cycloaliphatic hydrocarbon groups, which may be substituted;R.sup.3 represents isobutyl, sec-butyl, benzyl or (C.sub.3 -C.sub.8 cycloalkyl)methyl; andX represents a group of formula --CH(--A--R.sup.4)--Y (in which: A represents a single bond or an alkylene group; R.sup.4 represents a carboxy group; a protected carboxy group, a carbamoyl group, an N-substituted carbamoyl group, a carbazoyl group, an N-substituted carbazoyl group or an acyl group; and Y represents a hydroxy group, a mercapto group or a formyl group), ora group of formula --P(O) (R.sup.5)--OH (in which R.sup.

Abstract: Oligopeptides of formula (I) ##STR1## (wherein R.sup.1 CO-- is an acyl group. But is an isobutyl or sec-butyl group and X is a variety of organic groups) and salts and esters thereof have valuable renin inhibitory activity.

Abstract: An improved and novel process for the preparation of a carboxylic acid ester which comprises reacting a carboxylic acid with an alcohol or a sulfenic acid ester thereof in the presence of a tertiary phosphine and a disulfide of a mercaptoheterocyclic compound containing a nitrogen-carbon double bond with which the disulfide linkage is conjugated.