1. The molecule has a bicyclic core ring. Ring A (N1-C2-N3-C4-C5-C6) is fused with Ring B (C5-C6-N7-C8-N9), sharing two carbons.
2. N1 carries a straight-chain butyl substituent (-CH2-CH2-CH2-CH3).
3. C2 is double-bonded to an oxygen, forming a lactam carbonyl.
4. N3 is double-bonded to C4, and C4 bears a hydroxyl group (-OH).
5. In Ring B, N7 is double-bonded to C8, and N9 is substituted with a methyl group (-CH3).
6. C8 is bonded to a methylene group, which is linked to the oxygen of an ester group. The ester carbon is bonded to a three-carbon chain; the terminal carbon of this chain is a carbonyl (-C(=O)-) attached to a five-membered thiophene ring.
7. The thiophene ring (comprising four carbons and one sulfur) is numbered with the sulfur at position 1 and is attached the previous described carbonyl at position 2, and it bears a chlorine substituent at position 5.