What is "phenylglyoxylic acid"

Phenylglyoxylic acid is the organic compound with the formula CHC(O)COH. The conjugate base, known as benzoylformate is the substrate of benzoylformate decarboxylase, a thiamine diphosphate-dependent enzyme:

It is a colourless solid, m.p. 64–66 °C.

Phenylglyoxylic acid can be synthesized by oxidation of mandelic acid with potassium permanganate. An alternative synthesis involves hydrolysis of benzoyl cyanide.