BACKGROUND OF THE INVENTION The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.

Imperanene, a phenolic compound belonging to the rare class C6-C4-C6 of natural products, has been isolated from rhizomes of the plant Imperata cylindrica (1). Like some other compounds of the C6-C4-C6 class (2,3, 4), imperanene has been shown to have biological activity, including antiplatelet aggregation. The search of new platelet aggregation inhibitors for the treatment of diseases such as heart attack and stroke is an active research area, in which imperanene is a potential chemoterapeutic agent.

Recently, the stereoselective synthesis of both enantiomers of imperanene was published (5). The single enantiomer isolated from Iynperata cylindrica was thereby shown to be the (5)-enantiomer by comparison of optical rotation data (5).

Ekman et al. isolated in 1979 the compound (E)-4- (4-hydroxy-3- methoxyphenyl)-2- (4-hydroxy-3-methoxyphenylmethyl) but-3-enoic acid from an acidified alkaline hydrolysate of Norway spruce (Picea abies) root extractives. They proved that this acid was formed by the degradation of hydroxymatairesinol, the most abundant lignan in Norway spruce (6).

Hydroxymatairesinol is found in high concentrations, especially in knots and in the heartwood of branches in Norway spruce (7, 8). Unlike other lignans, hydroxymatairesinol can be isolated in large quantities from wood pulping processes.

It has recently been found that high amounts of hydroxymatairesinol can be produced by extracting finely divided wood material, preferably spruce knotwood, with a polar solvent or solvent mixture and precipitating hydroxymatairesinol from the extract as a complex. Suitable solvents to be used in the extraction step are, for example, pure ethanol or a mixture of ethanol and ethyl acetate. After the extraction step at least part of the solvent is preferably withdrawn before the addition of a complexing agent, which preferable is a carboxylate, such as acetate, of an alkali metal, such as potassium, an earth alkali metal, or ammonium. Such carboxylates form crystallisable adducts with hydroxymatairesinol. An especially preferable complexing agent is potassium acetate, which gives an easily crystallisable potassium acetate adduct of hydroxymatairesinol. This adduct is also rich in the (-) hydroxymatairesinol diastereomer.

SUMMARY OF THE INVENTION An object of this invention is a method for the synthesis of imperanene from a source available in large quantities, namely hydroxymatairesinol, especially hydroxymatairesinol derived from wood.

Thus, this invention concerns a method for the preparation of imperanene (IV) from hydroxymatairesinol (1), wherein hydroxymatairesinol (I)

in a first step is converted to the acid of formula (II)

The method is characterized in that either i) the acid (II) is esterified by use of an alcohol R-OH, wherein R is an alkyl or aryl group, to give an ester of formula (III) wherein R is an alkyl or aryl group, followed by reducing the ester (III) to imperanene or ii) the acid (II) is directly reduced to imperanene.

According to another aspect, the invention concerns the use of an ester of the formula (III) where R is an alkyl or aryl group, as an intermediate in the synthesis of imperanene.

According to a third aspect, the invention concerns a novel ester of the formula (III)

where R is an alkyl or aryl group, provided that R is not methyl.

DETAILED DESCRIPTION OF THE INVENTION Hydroxymatairesinol appears as two diastereomers, namely (-) hydroxymatairesinol and (-) allo-hydroxymatairesinol. The word "hydroxymatairesinol", shall in the definition of this invention be understood to cover any pure geometric isomer or pure stereoisomer or any pure diastereomer or mixture of isomers or diasteromers of the compound. Salts, adducts and complexes of the compound shall also be understood to be covered by the term. Also, wood extracts in which hydroxymatairesinol is the major component are understood to be covered by the term.

Although the acid (II) can be directly reduced to imperanene (IV), for example by use of lithium aluminium hydride, it is preferable to first esterify the acid (II) and then reduce the ester (III) to imperanene (IV).

Although the alcohol used for the esterification of the acid (II) can be any aliphatic or aromatic alcohol, alcohols having R substituents containing up to 20 carbon atoms may be preferred. Particularly preferred are the alcohols R- OH, wherein R is an alkyl or aryl group containing 1 to 12 carbon atoms.

Most preferred are alcohols where R is an alkyl group containing 1-3 carbon atoms.

The esterification is preferably performed as an acid catalysed esterification using the alcohol as solvent or by heating a mixture of (II) and the alcohol under removal of the released water.

The ester (III) or alternatively, the acid (II), is preferably reduced to imperanene either by catalytic hydrogenation or by a chemical reduction.

The catalytic hydrogenation is preferably carried out at high pressures and elevated temperatures. A suitable catalyst is a metal or metal oxide or a mixture of metals and/or metal oxides. As example of a suitable catalyst can be mentioned copper/chromium oxide catalyst.

The chemical reduction is carried out, for example, by use of sodium metal and alcohol. More preferably, the reduction is carried out by use of a metal hydride such as lithium aluminium hydride, or lithium or sodium borhydride.

The final product, imperanene (IV), can be obtained as a mixture of the two enantiomers.

The esters of formula (III) are new except for the methyl ester, which has been prepared in order to establish the structure of the acid (II) (reference 6).

However, the esters (III) have not earlier been suggested for use as intermediates in the synthesis of imperanene.

Although both of the hydroxymatairesinol diasteromers can be used for the synthesis according to this invention, it may be desirable to use the

(-) hydroxymatairesinol diastereomer, which is available in large quantities after the extraction process. According to one preferable embodiment, the hydroxymatairesinol is in the form of a complex or adduct, precipitated from an extract obtained by extracting wood material with a polar solvent, such as a potassium carboxylate adduct of hydroxymatairesinol.

The hydroxymatairesinol or its adduct in the starting material to be used in the synthesis does not necessarily need to be purified from other components.

The invention will be illuminated by the following non-restrictive Experimental Section.

EXPERIMENTAL SECTION All commercially available chemicals were used as supplied by the manufactures. Hydroxymatairesinol was isolated from Norway spruce as described in the International patent Publication WO 00/59946. GC analyses were performed on a HP-5890 standard gas chromatograph equipped with a HP-5 column and a FID detector. The samples were silylated using hexamethyldisilazane-chlorotrimethylsilane in pyridine, prior to analyses.

HRMS were recorded on a ZabSpecETOF system.

1H and 13C spectra were recorded on a JEOL JNM-A500 spectrometer at 500 and 125 MHz, respectively. 2D experiments were recorded using JEOL standard pulse sequences and chemical shifts are reported downfield from tetramethylsilane, numbering according to imperanene. The assignments of the 1H and 13C signals were based on homonuclear and heteronuclear direct and long-range correlation spectroscopy (COSY, HMQC, HMBC, COLOC).

Preparative chromatography was performed on a BUCHI B-688 MPLC apparatus, using normal phase silica (Silica gel 40, : 400 mesh, 600 m2/g, Fluka). Analytical TLC was carried out on pre-coated aluminium based sheets (Merk 60 F2s4). Chiral LC-MS was performed on a PE-Sciex API 3000 instrument equipped with a CHIRALCEL OD-R analytical column (0.46 x 25 cm) using multiple reaction monitoring techniques (MRM).

Example 1 (E)-4- (4-hydroxy-3-methoxyphenyl)-2- (4-hydroxy-3- methoxyphenylmethyl) but-3-enoic acid (Compound II in Scheme 1) Aqueous NaOH (0.6 M, 200 ml) was heated to 50 °C and hydroxymatairesinol (1.530 g, 4.1 mmol) was added. The temperature was adjusted 80 °C and the solution was stirred for 2.5 h, cooled to room temp and acidified with HCl-solution (6M) to pH-1. The mixture was then extracted with dichloromethane (4 x 50 ml) and the organic phase was dried over Na2S04. Evaporation of the solvent, using a rotary evaporator, left a light yellow solid (1. 386g, 98 %) of Compound II in a purity of 94 %.

Crystallisation from dichloromethane: diethylether (3: 1) gave Compound II as white needles (1. 068 g, 80 %) in a purity of 98 %. Mp. 126-128 °C.

HRMS m/z calculated for Cl9H2006 (M+) 344.1260 found 344. 1264. in NMR (500 MHz, CDC13) 8 2.86 (1H, dd, J= 13. 8,6. 9 Hz, H-7'b), 3.11 (1H, dd J= 13. 7, 7.8 Hz, H-7'a), 3.41 (1H, dddd, J= 8. 7,7. 9,7. 0,0. 9, H-8'), 3. 78 (3H, s, H-OMe'), 3.88 (3H, s, H-OMe), 6.08 (1H, dd, J= 15. 8, 8. 8 Hz, H-8), 6.36 (1H, d, J= 15.4 Hz, H-7), 6.69 (1H, dd, J= 7. 9,2. 0 Hz, H-6'), 6.72 (1H, d, J= 1. 9 Hz, H-2'), 6.79 (1H, d, J= 7. 9 Hz, H-5'), 6. 81- 6. 88 (3 H, complex, H-2, H-5, H-6). 13C NMR (500 MHz, CDC13) S 38.74 (C-7'), 51.59 (C-8'), 55. 87 (OMe'), 55.97 (OMe), 108. 58 (C-2), 112.12 (C-2'), 114.50 (C-5'), 114.67 (C-5), 120.16 (C-6), 121.87 (C-6'), 124.45 (C-8), 129.36 (C-1), 130.52 (C-1'), 132.71 (C-7), 144.44 (C-4'), 145. 84 (C-4), 146.61 (C-3'),

146.96 (C-3), 176.92 (C-9'). EI m/z (relative intensity) 344 (13), 298 (5), 207 (5), 161 (7), 150 (12), 137 (100), 122 (2), 71 (6).

Example 2 (E)-4- (4-hydroxy-3-methoxyphenyl)-2- (4-hydroxy-3- methoxyphenylmethyl) but-3-enoic acid methylester (a compound of formula III in Scheme 1).

0. 554 g of the acid II prepared in Example 1 (purity 98 %, 1.6 mmol) was dissolved in 55 ml methanol and 0.1 ml of 4: 1 methanol-concentrated H2SO4 (0.36 mmol) was added. The solution was stirred for 17 h at 50 °C and then poured into 70 ml saturated NaCl solution. The mixture was extracted with dichloromethane and the organic phase dried over Na2S04. Evaporation of the solvent gave 0.569 g (99 %) of the methyl ester in a purity of 92 %.

Crystallisation from dichloromethane-ether (1: 1) gave 0.40 g (70 %) of the methyl ester as a yellow solid. Mp. 143-144 °C.

HRMS m/z calculated for C2oH2206 (M+) 358. 1416 found 358. 1422. in NMR (500 MHz, CDC13) 5 2. 85 (1H, dd, J= 13. 7,6. 9 Hz, H-7'b), 3.08 (1H, dd J= 13. 7, 8. 1 Hz, H-7'a), 3.40 (1H, m, H-8'), 3.65 (3 H, s, 9'- OMe), 3. 81 (3H, s, H-OMe'), 3. 88 (3H, s, H-OMe), 6.06 (1H, dd, J= 15.8, 8. 8 Hz, H-8), 6.32 (1H, d, J= 15. 9 Hz, H-7), 6.66-6. 69 (2 H, complex, H-6', H- 2') 6.81 (1H, d, J= 8. 5 Hz, H-5'), 6. 80-6. 86 (3H, m, H-2, H-5, H-6). 13C NMR (500 MHz, CDC13) 8 38.92 (C-7'), 51.74 (C-8'), 51. 88 (9'-OMe), 55.88 (OMe), 55.93 (OMe'), 108.22 (C-2), 111.75 (C-2'), 114.29 (C-5'), 114.44 (C-5), 120.18 (C-6), 121. 80 (C-6'), 124.59 (C-8), 129.34 (C-1), 130.56 (C-1'), 132.47 (C-7), 144.23 (C-4'), 145.59 (C-4), 146.32 (C-3'), 146.65 (C-3), 174.19 (C-9'). EI m/z (relative intensity) 358 (17), 299 (3), 222 (16), 190 (7), 175 (2), 161 (25), 137 (100), 122 (6).

Example 3 Imperanene (Compound IV in Scheme 1) 0.554 g of the methyl ester prepared in Example 2 (1.5 mmol, purity 96 %) was dissolved in 40 ml dry THF and LAH (0.367 g, 9.7 mmol) was portionwise added. The mixture was stirred at room temperature under an atmosphere of argon (flame-dried glassware) for 3.5 h. The reaction was then quenched by adding the reaction mixture to 100 ml distilled water. The pH value was adjusted to 6 with 10 % HC1 and the mixture was extracted with dichloromethane (3 x 50 ml). The organic phase was washed with 50 ml saturated NaCl solution, dried over Na2S04, and the solvent was removed under reduced pressure. The residue was dried under vacuum, yielding 0.424 g (83 %) of imperanene as a white powder. Purity 94 %. The product was further purified by MPLC (ethylacetate : petroleum ether, 1: 1) to yield 0.266 g (54 %) of imperanene in a purity > 98 %.

HRMS m/z calculated for ClgH2205 (M+) 330. 1467 found 3 3 0. 1470.'H NMR (500 MHz, CDC13) 8 2. 62 (1H, m, H-8'), 2.68 (1H, dd, J= 13. 4,7. 0 Hz, H-7'a) 2.74 (1 H, dd, J= 13.4, 7.2 Hz, H-7'b), 3. 56 (1H, dd, J= 10.7, 7.2 Hz, H-9'a), 3.66 (1H, dd, J= 10.6, 4.7 Hz, H-9'b), 3.81 (3H, s, OMe'), 3. 88 (3H, s, OMe), 5.54 (1H, s, OH'), 5. 68 (1H, s, OH), 5.92 (1H, dd, J= 16. 0,8. 3 Hz, H-8), 6.34 (1H, dd, J= 15. 9, 0. 8 Hz, H-7), 6.66 (1H, dd, J= 8. 2,2. 0 Hz, H-6'), 6.68 (1H, complex, H-2'), 6. 81 (1H, d, J= 8. 2 Hz, H-5'), 6.80-6. 85 (3H, complex, H-6, H-5, H-2). 13C NMR (500 MHz, CDC13) 5 37.67 (C-7'), 47.60 (C-8'), 55. 88 (C-OMe'), 55.91 (C-OMe), 65.25 (C-9'), 108. 26 (C-2), 111. 81 (C-2'), 114.21 (C-5'), 114.47 (C-5), 119.74 (C-6), 121. 87 (C-6'), 128.42 (C-8), 129.75 (C-1), 131.54 (C-1'), 132.14 (C-7), 143.93 (C-4'),

145.33 (C-4), 146.34 (C-3'), 146.63 (C-3). EI m/z (relative intensity) 330 (41), 312 (14), 219 (21), 193 (49), 175 (58), 151 (54), 143 (17), 137 (100).

It will be appreciated that the methods of the present invention can be incorporated in the form of a variety of embodiments, only a few of which are disclosed herein. It will be apparent for the expert skilled in the field that other embodiments exist and do not depart from the spirit of the invention.

Thus, the described embodiments are illustrative and should not be construed as restrictive.

References 1. Kimihiro Matsunaga; Masaoki Shibuya; Yasushi Ohizumi. J. Nat. Prod.

1995, 58, 138.

2. Dalia Green; Yoel Kashman; Ahron Miroz. J. Nat. Prod. 1993, 56, 1201.

3. Masayoshi Ishida; Takashi Hamasaki ; Yuichi Hatsuda. Agr. Biol. Chem.

1979, 39, 2181.

4. Nada K. Gulavita; Shirley A. Pomponi; Amy E. Wright; Michelle Garay; Matthew A. Sills. J. Nat. Prod. 1995, 58, 954.

5. James C. Shattuck; Cheney M. Shreve; Organic Letters. 2001, 3, 3021.

6. Rainer Ekman ; Risto T. Sjoholm ; Rainer Sjoholm, Finn. Chem. Lett., 1979, 126.

7. Stefan Willför ; Jarl Hemming; Markku Reunanen; Christer Eckerman ; Bjarne Holmbom. Hydrophilic and lipophilic extractives in Norway spruce knots. Proc. 11 tu Inter. Symp. Wood Pulping Chem. , ATIP, Nice, 2001.

8. Rainer Ekman. Acta Acad. Abo. Ser. B. 1979, 39 : 3, 1.

Scheme 1