Begin by defining a five-membered ring (Ring A) composed of two adjacent nitrogens and three carbons, labeled A1-A2-A3-A4-A5.
- A1 (nitrogen) bears a phenyl ring.
- A2 (nitrogen) bears a methyl group.
- A3 (carbon) bears a methyl group and is double bonded to A4.
- A5 (carbon) is double-bonded to an oxygen.
- A4 (carbon) is single-bonded to a NH group, which in turn is single-bonded to a carbon that is double-bonded to Ring B (described next).

Ring B is a five-membered oxygen heterocycle. Label its atoms B1 through B5 so that B1 is the ring oxygen and B2-B5 are the four carbons, closing at B5-B1. The carbon from A4's substituent is double-bonded to B2. B3 is double-bonded to B4. At B5 of this ring, an exocyclic double bond extends into Ring C.

Ring C is a six-membered ring bearing a single nitro substituent (C1-C2-C3-C4-C5-C6). C1 is double-bonded to an oxygen. There are double bonds between C2-C3 and C5-C6. The exocyclic connection from Ring B attaches to C4. A nitro group (-NO2) is bonded to C2; the nitro group consists of a nitrogen atom bonded to two oxygen atoms-one via a double bond and the other via a single bond-resulting in the nitrogen carrying a positive charge and the oxygen attached via a single bond carrying a negative charge.