Candida Caprolactones

Various cyclic esters have been subjected to hpase-catalyzed ring-opening polymerization. Lipase catalyzed the ring-opening polymerization of 4- to 17-membered non-substituted lactones.In 1993, it was first demonstrated that medium-size lactones, 8-valerolactone (8-VL, six-membered) and e-caprolactone (e-CL, seven-membered), were polymerized by lipases derived from Candida cylindracea, Burkholderia cepacia (lipase BC), Pseudomonas fluorescens (lipase PF), and porcine pancreas (PPL). °... 

Other authors have described the lipase-catalyzed chemoselective acylation of alcohols in the presence of phenolic moities [14], the protease-catalyzed acylation of the 17-amino moiety of an estradiol derivative [15], the chemoselectivity in the aminolysis reaction of methyl acrylate (amide formation vs the favored Michael addition) catalyzed by Candida antarctica lipase (Novozym 435) [16], and the lipase preference for the O-esterification in the presence of thiol moieties, as, for instance, in 2-mercaptoethanol and dithiotreitol [17]. This last finding was recently exploited for the synthesis of thiol end-functionalized polyesters by enzymatic polymerization of e-caprolactone initiated by 2-mercaptoethanol (Figure 6.2)... 

Mei, Y., Kumar, A., and Gross, R. (2003) Kinetics and mechanism of Candida antarctica Lipase B catalyzed solution polymerization of epsilon-caprolactone. Macromolecules, 36.15, 5530-5536. 

The modification of polysaccharides using enzymes has been studied to attain more uniformly substituted products under mild reaction conditions. Hydroxyethylcellulose (HEC) particles were suspended in dimethylacetamide and acylated with vinyl stearate using Candida antartica Lipase B (CAL-B) as the catalyst. After 48 hrs, a product with degree of substitution (D.S.) of 0.1 was formed(8). HEC in film or powder form was modified using lipase-catalysis and e-caprolactone (CL) to form low D.S. HEC-g-PCL copolymers(9). Problems that limit the utility of these reactions include the use of polar aprotic solvents that strip the critical water from enzymes lowering their activities(lO) and the use of heterogeneous reaction conditions that restrict the modification of large particles and films to a small fraction of the substrate that resides at die surface. 

The substrates, ( )-E-caprolactones 1, 2 and 3 (Figure 1) were synthesized by Baeyer-Villiger oxidation of the corresponding cyclohexanones and kinetic resolutions were examined using Novozym-43S (immobilized lipase-B from Candida antarctica catalyzed ring-opening of the lactones 1, 2, and 3 with 1.5 molar equivalents of n-butanol (Scheme-1). Authentic samples of the racemic... 

Soiventless Enantioelective Ring-Opening Polymerization of Substituted e-Caprolactones by Novozym-435 (from Candida antartica) Catalysis... 

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