Synthesis of ?-Hydroxy-?-amino Acid Derivatives by Enzymatic Tandem Aldol Addition–Transamination Reactions

Three enzymatic routes toward ?-hydroxy-?-amino acids by tandem aldol addition–transamination one-pot two-step reactions are reported. The approaches feature an enantioselective addition of pyruvate to various nonaromatic aldehydes catalyzed trans-o-hydroxybenzylidene hydratase-aldolase (HBPA) from Pseudomonas putida. This affords chiral 4-hydroxy-2-oxo acids, which were subsequently enantioselectively aminated using S-selective transaminases. transamination processes investigated involving different amine donors and transaminases: (i) l-Ala as donor with recycling, (ii) a benzylamine benzaldehyde lyase fluorescens Biovar I (BAL) transform the formed into benzoin, minimizing equilibrium limitations, (iii) l-Glu double cascade comprising branched-chain ?-amino acid aminotransferase (BCAT) aspartate amino transferase (AspAT), both E. coli, l-Asp substrate regenerate l-Glu. thus obtained transformed ?-amino-?-butyrolactones, structural motifs found in many biologically active compounds valuable intermediates for synthesis pharmaceutical agents.