2-Ethyl-5-hydroxy-hexanoic Acid 1-Methylethyl Ester is an intermediate used in the synthesis of Mono(2-ethyl-5-hydroxyhexyl) Phthalate-d4 (Mixture of Diastereomers) (M542512), which is an isotope labeled derivative of Mono(2-ethyl-5-hydroxyhexyl) Phthalate (M542510), a phthalate metabolite.