pf-514273 pf-514273 pf-514273 is a drug developed by pfizer, which acts as an extremely selective antagonist for the cb1 receptor, with approximately 10,000x selectivity over the closely related cb2 receptor. this very high selectivity makes it useful for scientific research into these receptors, as many commonly used cannabinoid receptor antagonists also block the cb2 receptor to some extent. pf-514273identifiers iupac name 2-(2-chlorophenyl)-3-(4-chlorophenyl)-7-(2,2-difluoropropyl)-6,7-dihydro-2h-pyrazolooxazepin-8(5h)-one cas number851728-60-4 ypubchem cid11316919chemspider9491886 nunii45frj4ygm2comptox dashboard (epa)dtxsid80462142 chemical and physical dataformulac21h17cl2f2n3o2molar mass452.28 g·mol−13d model (jsmol)interactive image smiles o=c1n(cc(f)(c)f)ccoc2c1nn(c2-c(cc4)ccc4cl)-c3ccccc3cl inchi inchi=1s/c21h17cl2f2n3o2/c1-21(24,25)12-27-10-11-30-19-17(20(27)29)26-28(16-5-3-2-4-15(16)23)18(19)13-6-8-14(22)9-7-13/h2-9h,10-12h2,1h3key:fjmqjsuoogowbd-uhfffaoysa-n ny (what is this?)