Hydrogenolysis of hydroxymatairesinol over carbon-supported palladium catalysts Heidi Markus a , Pa¨ivi Ma¨ki-Arvela a , Narendra Kumar a , Natalya V. Kul’kova b , Patrik Eklund c , Rainer Sjo ¨holm c , Bjarne Holmbom d , Tapio Salmi a , and Dmitry Yu. Murzin a, * a Laboratory of Industrial Chemistry, Process Chemistry Centre, A ˚ bo Akademi University, Biskopsgatan 8, FIN-20500, A ˚ bo/Turku, Finland b Karpov Institute of Physical Chemistry, Moscow, Russia c Department of Organic Chemistry, Process Chemistry Centre, A ˚ bo Akademi University, Biskopsgatan 8, FIN-20500, A ˚ bo/Turku, Finland d Laboratory of Wood and Paper Chemistry, Process Chemistry Centre, A ˚ bo Akademi University, Porthansgatan 3, FIN-20500, A ˚ bo/Turku, Finland Received 11 March 2005; accepted 29 May 2005 The naturallignan hydroxymatairesinol was hydrogenolysed to a potential anticarcinogenic substance matairesinol over different carbon-supported palladium catalysts. The reaction was conducted in 2-propanol at 70 C under hydrogen flow in a stirred glass reactor. The catalysts were characterised by N 2 -physisorption, CO pulse chemisorption and pH measurement of aqueous catalyst slurries. The most active catalyst (Degussa-Hu ¨ls) gave yields of matairesinol over 90% in 4 h. It was concluded that the acidity of the catalyst had a profound influence on the reaction rate. KEY WORDS: lignans; hydroxymatairesinol; matairesinol; hydrogenolysis; carbon-supported palladium catalyst. 1. Introduction Lignans,a group of plant phenols consisting of two b-b-linked cinnamic acid residues [1], can be found in many different plantparts,such as the wooden parts, roots, leaves,flowers,fruits, and seeds.Most plants contain only smallamountsof lignansas glycosidic conjugatesassociated with fibrecomponents, which makesthe isolation processdifficult [2]. Coniferous trees,on the otherhand, contain exceptionally large amounts of lignans in unconjugated forms, which makes it easier to isolate them. Norway spruce (Picea abies) knots, i.e., the part of a branch that is embedded in the stem, contain large quantities of lignans, 6–24 wt.%, out of which hydroxymatairesinol is the mostabundant, constituting 65–85 wt.% of the lignans [3]. There are two diastereomers of hydroxymatairesinol, (7R,8R,8¢R)- (–)-7-allo-hydroxymatairesinol(HMR 1) and (7S,8R,8¢R)-(–)-7-hydroxymatairesinol (HMR 2), of which the latter is the major isomer [4]. Many differentplant lignansare converted by the mammalian gut microflora to the mammalian lignans enterolactone and enterodiol [5]. In the beginning of the 1980s it was suggested that lignans may prevent breast cancer[6].Severalstudies were made and the results showed thatwomen who have breast cancerexcrete smaller amounts of enterolactone than healthy women do, and that the urinary enterolactone excretion can be associated with the grain-fibre intake. It has also been proposed that besides breast cancer,lignans may pre- vent prostate and colon cancer. In addition to the an- ticarcinogenic effects, lignansalso have antioxidative effects [7]. Matairesinol (MAT) can be found in small amounts in different plants, for example in flaxseed and rye [5]. MAT can be producedthroughhydrogenolysisof HMR, which as indicated above could be extracted in largerquantitiesfrom Norway spruce knots. Hydro- genolyses of benzyl alcohol derivatives have earlier been performed over carbon-supported palladium catalysts in ethanol[8].The hydroxylis a poor leaving group, but the reaction rate can be clearly enhanced by addition of an acid,which produces a protonated alcohol making water the leaving group [8,9]. There are several benefits with activated carbons as support materials: they have high surface area, are inexpensive and inert in corrosive environments, and the preciousmetalssupported on them can easily be recovered [10]. Moreover, their pore structure and surface area can be varied relatively easily. However, commercial carbon-supported metal catalysts sometimesexhibitlarge batch-to-batch variations in performance which is, at least partially, due to natural variations in the starting materials [10]. Eklund et al. [11] demonstrated the possibilityto hydrogenolyse HMR under hydrogen pressure over Pd/C in dichloro- ethane and the K-acetate adduct of HMR was hydrog- enolysed with Raney-Nickeland Pd/C catalysts in ethanol (hydrogen pressure). In this work, a mixture of hydroxymatairesinol isomers(HMR 1 and HMR 2) extracted from Norway spruce was hydrogenolysed to * To whom correspondence should be addressed. E-mail: dmurzin@abo.fi Catalysis Letters Vol. 103, Nos. 1–2, September 2005 ( 2005) 125 DOI: 10.1007/s10562-005-6514-6 1011-372X/05/0900–0125/0 2005 Springer Science+Business Media, Inc.