a-oxoisocaproate
4-methyl-2-oxopentanoate
2-oxoisocaproate

C6H10O3

It's an a-keto acid (molecule formed after the deamination of an amino acid - in this case leucine)

Catabolism of isoleucine, leucine and tryptophan (3D)
Catabolism of phenylalanine, tyrosine and leucine (3D)
Synthesis of alanine, isoleucine, valine, and leucine (3D)