PENTAPEPTIDES, PROCESSES FOR THEIR PREPARATION, INTERMEDIATES USED IN SUCH PROCESSES, USE IN PHARMACEUTICAL COMPOSITIONS AND COMPOSITIONS CONTAINING THEM

摘要

Pentapeptides of the formula: wherein R1 is hydrogen, methyl, ethyl, propyl, 2-methyl-2-pentenyl, 2-methyl-1-pentenyl, cyclopropylmethyl, or cyclobutylmethyl; R2, R3, and R4 are, independently, hydrogen or methyl; and X is -OH, -NH2, -NHCnH2n+1 where n is 1, 2, 3, or 4, -OR3, or CH2OR3, where R3 is hydrogen or lower alkyl of from 1 to 4 carbon atoms; or a pharmaceutically acceptable salt thereof; have analgesic activity upon administration to warm-blooded animals.