title: 4-Oxo-1,4-dihydro-benzo[h][1,3]thia-zeto[3,2-a]quinoline-1,3-dicarb-oxy-lic acid.
abstract: In the title mol-ecule, C(16)H(9)NO(5)S, there is an intra-molecular O-H⋯O hydrogen bond involving the quinolone carbonyl O atom and a carboxyl OH group. In the crystal, inter-molecular O-H⋯O hydrogen bonds between the carbonyl group of the quinolone carboxyl group, and a second carboxyl group on the thia-zeto moiety lead to the formation of chains propagating along [201] and perpendicular to the π-stacks of mol-ecules.
authors.forename: Louise N
authors.initials: LN
authors.lastname: Dawe
authors.forename: Abeer
authors.initials: A
authors.lastname: Ahmed
authors.forename: Mohsen
authors.initials: M
authors.lastname: Daneshtalab