epicillin epicillin epicillin (inn) is a penicillin antibiotic. it is not approved by the fda for use in the united states. epicillinclinical dataatc codej01ca07 (who) identifiers iupac name (2s,5r,6r)-6-amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicycloheptane-2-carboxylic acid cas number26774-90-3 ypubchem cid71392chemspider64486 nunii3lu1l73c8ycomptox dashboard (epa)dtxsid60181288 echa infocard100.043.623 chemical and physical dataformulac16h21n3o4smolar mass351.42 g·mol−13d model (jsmol)interactive image smiles o=c(o)2n3c(=o)(nc(=o)(c/1=c/c\c=c/c\1)n)3sc2(c)c inchi inchi=1s/c16h21n3o4s/c1-16(2)11(15(22)23)19-13(21)10(14(19)24-16)18-12(20)9(17)8-6-4-3-5-7-8/h3-4,7,9-11,14h,5-6,17h2,1-2h3,(h,18,20)(h,22,23)/t9-,10-,11+,14-/m1/s1 nkey:rpbafsbgydknrg-njbdsqktsa-n n ny (what is this?) (verify) it is an aminopenicillin.