isovaleric acid

noun

iso·​va·​ler·​ic acid ˌī-sō-və-ˌlir-ik-  -ˌler- 

: a liquid acid C₅H₁₀O₂ that has a disagreeable odor, that occurs especially in valerian root in the free state and in some essential oils and marine-animal oils in the form of esters, and that is used chiefly in making esters for use in flavoring materials