Abstract: The present invention relates to compounds of the formula ##STR1## wherein R' is hydrogen, straight or branched chain lower alkyl having from 1 to 4 carbon atoms or benzyl, Z is hydrogen or straight chain lower alkyl having from 1 to 4 carbon atoms, Y is hydrogen or a nitrogen blocking group selected from the group consisting of tertiary alkoxycarbonyl, benzyloxycarbonyl, cycloalkoxycarbonyl and vinyloxycarbonyl, R.sub.c is hydrogen, halogen or benzyloxy and R.sub.d is hydrogen, or R.sub.c and R.sub.d are benzyloxy; or an individual diastereomer thereof. Said compounds having use as intermediates in the production of enkephalin derivatives which in turn are used as analgesic and antipsychotic agents.