Methyl 7,8-diacetoxy-11-oxo-5-(2-oxopyrrolidin-1-yl)-7,9-epoxycyclopenta[4,5]pyrido[1,2-a]quinoline-10-carboxylate sesquihydrate

Abstract

The title compound, C26H28N2O9·1.5H2O, the product of an acid-catalysed Wagner–Meerwein skeletal rearrangement, crystallizes as a sesquihydrate with the O atom of one of the two independent water molecules occupying a special position on a twofold axis. The organic molecule comprises a fused pentacyclic system containing two five-membered rings (cyclopentane and tetrahydrofuran) and three six-membered rings (piperidinone, tetrahydropyridine and benzene). The five-membered rings have the usual envelope conformations, and the central six-membered piperidinone and tetrahydropyridine rings adopt boat and sofa conformations, respectively. In the crystal, there are three independent O—H...O hydrogen bonds, which link the organic molecules and water molecules into complex two-tier layers parallel to (001). The layers are further linked into a three-dimensional framework by attractive intermolecular carbonyl–carbonyl interactions.