Enzymatic synthesis of Thia-L-tryptophans

Thia analogs of L-tryptophan (β-3-thieno[2,3-b]pyrrolyl-L-alanine and β-3-thieno[3,2-b]pyrrolyl-L-alanine) have been prepared by the reaction of L-serine and thienopyrroles catalysed by Salmonella typhimurium tryptophan synthase.