Journal of Molecular Catalysis B: Enzymatic 92 (2013) 51–56 Contents lists available at SciVerse ScienceDirect Journal of Molecular Catalysis B: Enzymatic jo ur nal home p age: www.elsevier.com/locate/molcatb Polymer-immobilized fluorinase: Recyclable catalyst for fluorination reactions Maxim E. Sergeev a,∗ , Federica Morgia a , Muhammad R. Javed a , Mami Doi b , Pei Y. Keng a,∗ a Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, University of California Los Angeles, 570 Westwood Plaza, Los Angeles, CA 90095, USA b Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan a r t i c l e i n f o Article history: Received 14 January 2013 Received in revised form 11 March 2013 Accepted 11 March 2013 Available online 21 March 2013 Keywords: Nucleophilic fluorination Enzymatic catalysis Polymer support Immobilized fluorinase a b s t r a c t Polymer-immobilized fluorinase for the synthesis of 5 ′ -fluoro-5 ′ -deoxyadenosine (FDA) from S-adenosyl- l-methionine (SAM) and fluoride ion in aqueous media is described. The optimal composition of the poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) and the heterogeneous catalytic reaction conditions were developed to yield FDA in 49% within 150 min. In PET radiochemistry, using [ 18 F]fluoride ion in [ 18 O]H 2 O obtained from the cyclotron, [ 18 F]FDA was synthesized with 68% fluorination efficiency. The immobilized fluorinase was recycled for up to four runs with 80% of catalytic activity in the final cycle. © 2013 Elsevier B.V. All rights reserved. 1. Introduction 1.1. Statement of significance Research on a simple, mild and selective fluorination methodol- ogy of complex molecules is critical in facilitating the development of pharmaceuticals and in accelerating the field of molecular diagnostics. Fluorinated organic molecules are known to enhance lipophilicity, metabolic stability, bioavailability and selectivity through their inductive effects [1 a–c ]. Additionally, the less stable fluorine-18 isotope counterpart is an ideal nuclide for molecular diagnostic using positron emission tomography (PET) due to the moderate half-life and the high image resolution in PET imaging in comparison to other radioisotopes [2]. To date, fluorine-18 labeling reactions require time consuming multistep synthesis in organic solvents due to the incompatibility of fluoride ions with other functional groups, the use of harsh reagents and the need of high reaction temperatures to produce injectable doses of PET probes in less than 6 h [3,4]. More recently various fluorination methodolo- gies utilizing transition-metal catalysts and bulky protic solvents are emerging to simplify fluorination reactions [5]. Notably, the enzyme catalyzed fluorination reaction using fluoride ion in aque- ous media is particularly attractive due to its high chemoselectivity and high reaction yield under extremely mild conditions [6–8]. In the field of enzyme catalysis for organic syntheses, solid ∗ Corresponding authors. Tel.: +1 310 983 3194; fax: +1 310 206 8975. E-mail addresses: msergeev@mednet.ucla.edu, m.e.sergeev@gmail.com (M.E. Sergeev), pkeng@mednet.ucla.edu (P.Y. Keng). supported enzymes enable simpler separation of the enzymes from the product, and the immobilized enzymes could be recycled over a finite number of cycles. These features of immobilized enzymes have the potential to reduce the overall cost and synthesis time [9,10]. However, there is no evidence of successful applications of recyclable biocatalysts for fluorination of organic molecules. Specif- ically in PET radiochemistry, the short-lived [ 18 F]fluorine isotope (t 1/2 = 109 min) necessitates the development of a rapid, simple and efficient methodology for the preparation of [ 18 F]-labeled com- pounds to obtain optimal PET images. Therefore, it is critical to streamline the radiolabeling process with the shortest time for reaction, purification and reformulation. Specifically for homoge- neous enzymatic reactions, the enzymes need to be first separated from the reaction product prior to subjecting the crude mixture through a standard purification process. Thus, the combined fea- tures of solid phase enzymatic fluorination catalysis and the mild and selective enzymatic reactions have significant potential toward the development of a more efficient, simplified and rapid prepara- tion of fluorine containing molecules. 1.2. Known procedures O’Hagan and co-workers discovered and isolated a spe- cific halogenase, called fluorinase (also known as 5 ′ -deoxy-5 ′ - fluoroadenosine synthase, EC 2.5.1.63) to catalyze the reaction of S-adenosyl-l-methionine (SAM) with fluoride ion [11,12]. In comparison to conventional synthetic methodologies, which require multistep reactions, high temperature, long synthesis time and necessitate complicated purification processes, enzy- matic reactions are performed in a single step under mild reaction 1381-1177/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molcatb.2013.03.009