Healthcare costs are a significant worldwide, with many patients being denied medications because of their high prices. One approach to addressing this problem involves the biosynthesis of chiral drug intermediates, an environmentally friendly solution that can be used to generate pharmaceuticals at much lower costs than conventional techniques. In this context, embodiments of the invention comprise methods and materials designed to allow microorganisms to biosynthesize the nonnatural amino acid L-homoalanine. As is known in the art, L-homoalanine is a chiral precursor of a variety of pharmaceutically valuable compounds including the anticonvulsant medications levetiracetam (sold under the trade name Keppra®) and brivaracetam, as well as ethambutol, a bacteriostatic antimycobacterial drug used to treat tuberculosis. Consequently, embodiments of the invention can be used in low cost, environmentally friendly processes to generate these and other valuable compounds.