Biosynthesis of leucine involves conversion of alpha-ketoisovalerate to 1-isopropylmalate (see above). This proceeds in multiple steps (1) deprotonation, (2) C-C bond formation followed by protonation and thioester hydrolysis. Write a detailed mechanism for this conversion. Then, draw the intermediate (or compound) produced in step 1. You do not have to consider stereochemistry. Draw uninvolved carboxyl groups in the anionic state, and enolates as carbanions. When needed, abbreviate CoenzymeA-S- as CH3S- in your drawing.