a-b-dihydroxyisovalerate
(R)-2,3-dihydroxy-3-methylbutanoate
(R)-2,3-dihydroxy-isovalerate
(R)-2,3-dihydroxy-isovaleric acid

C5H10O4

It's an a-keto acid (molecule formed after the deamination of an amino acid - in this case valine) precursor. In order to form the valine carbon skeleton, it has to be dehydrated twice (to remove the C2 and C3 hydroxyls).

Synthesis of alanine, leucine, valine and isoleucine (3D)