b-Fluoro-coniferyl alcohol does not inhibit lignin biosynthesis in suspension cultures of Picea abies (L.) Karst. Mikaela Gustafsson a , Anna Ka¨ rko¨ nen b , Liisa K. Simola b , Teemu H. Teeri c , JussiSipila¨ a , Ilkka Kilpela¨inen c , Go¨sta Brunow a, * a Laboratory of Organic Chemistry, Department of Chemistry, University of Helsinki, PO Box 56, FIN-00014, Helsinki, Finland b Department of Biosciences, Division of Plant Physiology, University of Helsinki, PO Box 56, FIN-00014, Helsinki, Finland c Institute of Biotechnology, University of Helsinki, PO Box 56, FIN-00014, Helsinki, Finland Received 2 October 2000; received in revised form 14 May 2001 Abstract A fluorinated analogue of coniferyl alcohol has been reported to be a specific inhibitor of oxidases involved in the biosynthesis of lignin. The Z isomer of b-fluoro-coniferyl alcohol was synthesized and used for the preparation of dehydrogenation polymers (DHPs) and was also tested on lignin producing suspension cultures of spruce (Picea abies (L.) Karst.). The growth of the cells or the production of lignin by the suspension cultures was not significantly affected by the addition of fluoroconiferyl alcohol. This analogue did not form polymers quite as easily as did coniferyl alcohol in oxidation with hydrogen peroxide and horseradish per- oxidase. In both cases the b-fluoroconiferyl alcohol became incorporated in the polymeric product. We were unable to detect any specific inhibition of peroxidase activity, which is at variance with earlier reports of pronounced inhibition of lignin biosynthesis in poplar plantlets by fluoroconiferin, a potential inhibitor of oxidases involved in lignin biosynthesis. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Picea abies (L.) Karst.; Spruce; Suspension cultures; Lignin synthesis; Inhibition; Fluoroconiferyl alcohol 1. Introduction Fluorinated analogues of lignin precursors, so called monolignols, have been studied as possible inhibitors of peroxidase activity (Goldberg et al., 1988). Fluorine, being similar in size to hydrogen but very different in reactivity can, when substituted in a reactive position, give rise to analogues which may act as antimetabolites towards the fluorine-free parents (Welch, 1987). In monolignols, the b position in the side chain is the most reactive. Such fluoro analogues of cinnamic compounds have been reported to function as hydrogen donors for peroxidase reac- tions, forming ‘‘lignin-like’’ polymers (Goldberg et al., 1988). In a more recent report it was stated that b- fluoroconiferyl alcohol acts as a specific inhibitor of lignin biosynthesis in poplar shoots (Daubresse et al., 1997). In view of the importance for the study of lignin forming enzymes of finding a specific inhibitor of lignin polymerization, we have synthesized b-fluoroconiferyl alcohol and studied its effect on the lignin formation ability of suspension cultures of spruce as well as its reactivity in peroxidatic oxidation experiments. We could not observe any significant effects on lignin pro- duction in the suspension cultures after addition of the fluoro analogue of coniferyl alcohol. 2. Results 2.1. The preparation of -fluoro coniferyl alcohol The synthesis of the Z isomer coniferyl alcohol with a fluorine in the b position, using a Horner–Emmons reaction with phosphonofluoroacetate and vanillin ace- tate, has been mentioned in an article by Goldberg et al. (1988) but no physical or spectroscopic data for the pro- duct have been published. The Horner–Emmons is a generalrouteforobtainingmainlytheEisomer,whichin this case has to be isomerized to the Z isomer by treat- ment with bromine. We have used a more direct stereo- selective route to (Z)-2-fluoroalkenoates (Clemenceau and Cousseau, 1993) to prepare the acetate of (Z)-b- fluoro ethyl ferulate which we then reduced to the cor- 0031-9422/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0031-9422(01)00251-5 Phytochemistry 58 (2001) 243–248 www.elsevier.com/locate/phytochem * Corresponding author. E-mail address: gosta.brunow@helsinki.fi (G. Brunow).