Isotopically labeled alpha-keto acids and esters

An isotopically labeled compound of Formula (IIa),

• wherein:
• X is F, Cl, Br, I, MgF, MgCl, MgBr and MgI;
• each R and each R1 may be the same or different and independently may represent hydrogen, deuterium, tritium or a C1-C36 substituted or unsubstituted, saturated, or unsaturated, linear, branched, cyclic, aromatic, or substituted aromatic group, wherein R or R1 may include a heteroatom including O, N, S, Si, and P wherein any of the carbon atoms or heteroatoms may be isotopically labeled;
• and
• y is independently 12, 13, or 14.