title: Highly regioselective enzymatic synthesis of 5'-O-stearate of 1-beta-D-arabinofuranosylcytosine in binary organic solvent mixtures.
abstract: In this paper, highly regioselective enzymatic acylations of 1-beta-D-arabinofuranosylcytosine (ara-C) with vinyl stearate (VS) in binary organic solvents were explored for the preparation of 5'-O-stearate of ara-C with potential antitumor activity. Twelve kinds of hydrolases were tested for the regioselective acylation reaction and the immobilized Candida antarctica lipase B (Novozym 435) showed the highest regioselectivity (>99.9%) towards the 5'-OH of ara-C. A comparative study showed that the lipase had much higher catalytic activity in the binary mixture of hexane and pyridine than in other tested co-solvent systems. To better understand lipase-mediated acylation conducted in the best binary organic solvent system, the effects of hydrophobic solvent content, molar ratio of VS to ara-C, initial water activity, and reaction temperature on the acylation reaction were studied. It was found that the most suitable hexane content, VS-ara-C molar ratio, initial water activity, and reaction temperature were shown to be 25% (v/v), 20:1, 0.07, and 50 degrees C, respectively. Under these reaction conditions, the initial reaction rate, the maximum substrate conversion, and regioselectivity were as high as 86.0 mmol.L(-1)h(-1), 96.6%, and >99.9%, respectively. The product of Novozym 435-catalyzed acylation was characterized by Carbon-13((13)C) NMR and confirmed to be 5'-O-stearate of ara-C.
authors.affiliation: State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Wushan Road 381, Guangzhou, 510641, People's Republic of China.
authors.forename: Xiao-feng
authors.initials: XF
authors.lastname: Li
authors.forename: Min-hua
authors.initials: MH
authors.lastname: Zong
authors.forename: Guang-lei
authors.initials: GL
authors.lastname: Zhao
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism*; D002175:Candida / Q000201:enzymology; D003561:Cytarabine / Q000031:analogs & derivatives* / Q000378:metabolism*; D004800:Enzymes, Immobilized / Q000378:metabolism; D006586:Hexanes / Q000737:chemistry; D006867:Hydrolases / Q000378:metabolism*; D011725:Pyridines / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013228:Stearates / Q000378:metabolism*; D013696:Temperature
chemical_list: D000970:Antineoplastic Agents; D004800:Enzymes, Immobilized; D006586:Hexanes; D011725:Pyridines; D012997:Solvents; D013228:Stearates; D003561:Cytarabine; D006867:Hydrolases; C023666:pyridine