Tetronic acid is a chemical compound, classified as a γ-lactone, with the molecular formula C4H4O3.

It interconverts between keto and enol tautomers:[2] Many natural products such as ascorbic acid (vitamin C), penicillic acid, pulvinic acids, and abyssomicins possess the β-keto-γ-butyrolactone motif of tetronic acid.

[3] In organic synthesis, it is used as a precursor for other substituted and ring-fused furans and butenolides.

[4][5] It is also forms the structural core of a class of pesticides, known as tetronic acid insecticides, which includes spirodiclofen and spiromesifen.

[6]