The 3-Me analog of fentanyl (3-MeF) was first introduced by Paul Janssen, J. Med. Chem.; 1974; 17(10); 1047-1051 which has been recently revisited by Slavic researchers. J. Serb. Chem.; 2004; 69(7) 511-526 QSAR reveals that the β-OH was first incorporated into 3-MeF because this pharmacophore had previously been shown to raise the potency of closely-related piperidine based narcotics J. Med. Chem.; 1962; 5(5); 913-919 such as phenoperidine, for example. AFAIK, ohmefentanyl was first reported by Chinese chemists in 1979. Scienta Sinica Vol. XXIV No. 5 pp 710-721 (May 1981) Since that time, both Chinese, and also American scientists, submitted the first elaborate evaluations on OMF isomer variations in 1995, in the JMC.J. Med. Chem.; 1995; 38(18); 3652-3659. J. Med. Chem.; 1995; 38(9); 1547-1557