4-methyl-2-oxopentanoic acid is a 2-oxo monocarboxylic acid that is pentanoic acid (valeric acid) substituted with a keto group at C-2 and a methyl group at C-4. A metabolite that has been found to accumulate in maple syrup urine disease. It has a role as a human metabolite and an algal metabolite. It derives from a valeric acid. It is a conjugate acid of a 4-methyl-2-oxopentanoate. Experimental spectrum in Natural Products Magnetic Resonance Database: [NP0001215](https://np-mrd.org/natural_products/583/submission_spectrum_view?spectrum_id=366&spectrum_type=real)