Heterocyclic β-hydroxy-α-amino acids as substrates for a novel aldolase from Streptomyces amakusaensis; preparation of (2R,3R)-3-(2-thienyl)serine and (2R,3R)-3-(2-furyl)serine from racemic threo material

Abstract

A novel aldolase from Streptomyces amakusaensis which catalyses a reverse aldol reaction on (2S,3R)-β-hydroxy-α-amino acids is specific for aromatic compounds, but otherwise shows broad substrate tolerance. This is further illustrated by its ability to catalyse the cleavage of two aromatic heterocyclic compounds, namely (2S,3S)-3-(2-thienyl)serine 10 and (2S,3S)-3-(2-furyl)serine 12 at similar (but lower) rates to that of 3-phenylserine 2. This cleavage is stereospecific and leads to the preparation of optically pure (2R,3R)-3-(2-thienyl)serine 14 and (2R,3R)-3-(2-furyl)serine 15 from readily synthesised threo material. Evidence is presented that the aldolase is neither a serine hydroxymethyltransferase nor a threonine aldolase.