Dimethyl 6-[1,2-bis(methoxycarbonyl)-2-(triphenyl-lambda5-phosphanylidene)ethylideneamino]-2-methylsulfanyl-3,4-pyridinedicarboxylate forms a chain of hydrogen-bonded rings.

In the title compound, C(34)H(31)N(2)O(8)PS, the intramolecular distances provide evidence for polarization of the molecular-electronic structure. The molecules are linked into complex chains of rings by three independent C-H...O hydrogen bonds. The significance of this study lies in its finding that two of the four carbonyl O atoms play no role in the hydrogen bonding, despite the large excess of potential hydrogen-bond donors present.