Chiral chemoenzymatic routes

Fryszkowska, A., Fisher, K, Gardiner, J. M., and Stephens, G.M. (2010) A short, chemoenzymatic route to chiral P-aryl-y-amino acids using reductases from anaerobic bacteria. Org. Biomol. Chem., 8, 533-535. 

Following route A (Fig. 1), Yan Xiao et al. reported the chemoenzymatic synthesis of poly(8-caprolactone) (PCL) and chiral poly(4-methyl-8-caprolactone) (PMCL) microparticles [5]. The telechelic polymer diol precursors were obtained by enzymatic polymerization of the corresponding monomers in the presence of hexanediol. Enzymatic kinetic resolution polymerization directly yielded the (R)-and (S )-enriched chiral polymers. After acrylation using acryloylchloride, the chiral and nonchiral particles were obtained by crosslinking in an oil-in-water emulsion photopolymerization. Preliminary degradation experiments showed that the stereoselectivity of CALB is retained in the degradation of the chiral microparticles (Fig. 2). 

Extension of DKR to polymer chemistry would readily result in chiral polyesters, polycarbonates, or polyamides from an optically inactive monomer mixture. Scheme 10 describes three variants of chemoenzymatic catalysis applied in polymer chemistry that recently appeared in the literature. Route A uses AA and BB monomers to prepare chiral polymers from racemic/diasteromeric diols. Route B converts an enantiomer mixture of AB monomers to homochiral polymers. Route C is the enzymatic ring-opening polymerization of co-methylated lactones to homochiral polyesters. Details will be given in Sect. 3.4.2. 

Fig. 8. Chemoenzymatic synthesis of chiral epoxides via the a-haloketone reduction route...

Pamies, O. and BackvaU, J.-E. (2002). Enzymatic kinetic resolution and chemoenzymatic dynamic kinetic resolution of delta-hydroxy esters. An efficient route to chiral delta-lac-tones. /. Org. Chem., 67,1261-1265. 

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