sibopirdine sibopirdine sibopirdine, also known as exp921, is a nootropic drug. sibopirdineclinical dataatc codenonelegal statuslegal status in general: unscheduled pharmacokinetic databioavailabilitysusmetabolismsusexcretionsusidentifiers iupac name 5,5-bis(4-pyridylmethyl)-5h-cyclopentadipyridine cas number139781-09-2 yanhydrous: 122955-18-4 ypubchem cid9929210chemspider169416 nuniirag2185dr1anhydrous: 7ikm67cseq ykeggd05833 ycomptox dashboard (epa)dtxsid60930596 chemical and physical dataformulac23h18n4molar mass350.425 g·mol−13d model (jsmol)interactive image smiles c5cnccc5cc1(cc3ccncc3)c2cccnc2-c4c1cccn4 inchi inchi=1s/c23h18n4/c1-3-19-21(26-9-1)22-20(4-2-10-27-22)23(19,15-17-5-11-24-12-6-17)16-18-7-13-25-14-8-18/h1-14h,15-16h2 nkey:fjyrsjdizktxkb-uhfffaoysa-n n ny (what is this?) (verify) synthesis sibopirdine synthesis: dupont merck pharmaceutical company; u.s. patent 5,272,269 (1993). 4,5-diazafluoren-9-one was the starting material.