$\alpha$-Ketoglutarate and Oxaloacetate act as precursors in the synthesis of ______.

$\alpha$-Ketoglutarate is a key intermediate in the Krebs cycle and serves as the precursor for the synthesis of the amino acid glutamic acid (glutamate) through the process of reductive amination or transamination.

Oxaloacetate, another intermediate of the Krebs cycle, acts as the precursor for the synthesis of aspartic acid (aspartate) via transamination.

Thus, $\alpha$-Ketoglutarate and Oxaloacetate act as precursors in the synthesis of Glutamic acid and Aspartic acid, respectively.

Answer: Glutamic acid, Aspartic acid