Compounds of formula (I) ##STR00001## wherein R.sub.1 is 2-indanyl, R.sub.2 is 1-methylpropyl, R.sub.3 is a group selected from 2,6-dimethyl-3-pyridyl or 4,6-dimethyl-3-pyridyl, R.sub.4 represents methyl and R.sub.5 represents hydrogen or methyl or, R.sub.4 and R.sub.5 together with the nitrogen atom to which they are attached represent morpholino and pharmaceutically acceptable derivatives thereof are described, as are processes for their preparation, pharmaceutical compositions containing them and their use in medicine, particularly their use as oxytocin antagonists.