Kamei C, Mio M, Tasaka K
Experientia. 1983 Sep 15;39(9):1025-6. doi: 10.1007/BF01989784.
Studies of the analgesic effect of tripeptide-beta-phenethylamides are described, and their structure-activity relationship is discussed. SD-25, which has a methyl group at R2, and a hydroxymethyl group at R3 of beta-phenethylamide, was the most potent one of the 8 analogs tested.