Abstract:
The invention relates to a carbohydrate derivative having formula I                            
     wherein R 1  is (1-4C)alkoxy; R 2 , R 3  and R 4  are independently (1-4C)alkoxy or OSO 3   − , the total number of sulfate groups is 4, 5, or 6; and the twisted lines represent bonds either above or below the plane of the six-membered ring to which they are attached; or a pharmaceutically acceptable salt thereof. 
     The compounds of the invention have antithrombotic activity and may be used for treating or preventing thrombosis and for inhibiting smooth muscle cell proliferation.

Description:
FIELD OF THE INVENTION 
     The invention relates to a carbohydrate derivative, a pharmaceutical composition containing the same, as well as the use of said carbohydrate derivative for the manufacture of a medicament. 
     BACKGROUND OF THE INVENTION 
     Heparin is a commonly used anticoagulant from biological sources such as intestinal mucosa. In the presence of heparin, the inactivation of thrombin by anti-thrombin III (AT-III) is greatly accelerated, involving changes in both the conformation of heparin and AT-III on complexation. Thrombin regulates the last step in the blood coagulation cascade. The prime function of thrombin is the cleavage of fibrinogen to generate fibrin monomers, which form an insoluble gel, a fibrin clot, by cross-linking. 
     The structural features of heparin that are required for interacting AT-III have been subject to various investigations. There are parts in the heparin polymer which show only low affinity for AT-III, whereas other parts were found to be more important for binding to AT-III. Studies of fragmented heparin have finally resulted in the identification of a pentasaccharide fragment accounting for the minimal high-affinity structure that binds to AT-III (see e.g. Physiological Reviews, 71 (2), 488/9, 1991). In this high-affinity fragment eight sulfate groups are present. Four of the sulfate groups were found to be essential for binding to AT-III (Advances in Carbohydrate Chemistry and Biochemistry; Vol. 43; Eds. R. S. Tipson, D. Horton; Publ. Harcourt Brace Jovanovich; B. Casu (pages 51-127), paragraph 6), whereas the other further attribute to higher affinity. This finding was confirmed in synthetic analogues of the pentasaccharide fragment (see e.g. Agnew. Chem. 32 (12), 1671-1818, 1993). 
     The identification of the high-affinity pentasaccharide fragment inspired the preparation of synthetic analogues thereof. Small synthetic carbohydrate molecules of the glycosaminoglycan type were found to be potent and selective anti-Xa inhibitors. See for instance European patent 84,999. Later filed patents/patent applications showed that many variants of these molecules have similar and even higher activities and further improved pharmacological properties, such as the glycosaminoglycan-related carbohydrate derivatives disclosed in EP 529,715 and EP 454,220. These carbohydrate derivatives are devoid of the characteristic functional groups of glycosaminoglycans: free hydroxyl groups, N-sulfate and N-acetyl groups. Further, all of the pentasaccharides disclosed in these latter patent applications carry at least seven sulfate groups. In the field of antithrombotic oligosaccharide derivatives it was thus generally assumed that at least seven sulfate groups are required in pentasaccharide compounds in order to obtain clinically acceptable levels of antithrombotic activity. 
     Unexpectedly, however, a class of glycosaminoglycan-related carbohydrate derivatives has now been found having only four to six sulfate groups and which still display significant clinically effective antithrombotic activity. In addition, the compounds of this invention show fewer side effects. For example, bleeding risks are reduced and the low sulfate content of the compounds does not give rise to heparin-induced thrombocytopenia (HIT) [HIT is a severe side effect, which may be the cause of the death of a patient]. Further, compounds of this invention have a biological half-life which allows once-a-day-treatment. Once-a-day-treatment may be considered to be more favourable than, for example, once-a-week-treatment, allowing quick adaptation of the medical treatment is the condition of a patient requires so. Also hospital logistics are easier with one-a-day-treatment, as no complex dosing schemes are required for the treatment of the patients. 
     Thus, the compounds of the invention display an unexpected and delicately balanced pharmacological profiles. 
     SUMMARY OF THE INVENTION 
     The invention therefore relates to a carbohydrate derivative having formula I                           
     wherein R 1  is (1-4C)alkoxy; R 2 , R 3  and R 4  are independently (1-4C)alkoxy or OSO 3   − ; the total number of sulfate groups is 4, 5 or 6; and the twisted lines represent bonds either above or below the plane of the six-membered ring to which they are attached; or a pharmaceutically acceptable salt thereof. 
     The compounds of the present invention are useful for treating and preventing thrombin-mediated and thrombin-associated diseases. This includes a number of thrombotic and prothrombotic states in which the coagulation cascade is activated which include, but are not limited to, deep vein thrombosis, pulmonary embolism, thrombophlebitis, arterial occlusion from thrombosis or embolism, arterial reocclusion during or after angioplasty or thrombolysis, restenosis following arterial injury or invasive cardiological procedures, postoperative venous thrombosis or embolism, acute or chronic atherosclerosis, stroke, myocardial infarction, cancer and metastasis, and neurodegenerative diseases. The carbohydrate derivatives of the invention may also be used as inhibitors of smooth muscle cell proliferation and for the treatment of angiogenesis, cancer and retrovirus infections, like HIV. 
     Further, the compounds of the invention may be used as anticoagulants and anticoagulant coatings in extracorporeal blood circuits, as necessary in dialysis and surgery. 
     The compounds of the invention may also be used as in vitro or ex vivo anticoagulants. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred carbohydrate derivatives according to the invention have the D-unit has the structure                           
     R 1  is methoxy; and R 2 , R 3  and R 4  are independently methoxy or OSO 3   − . 
     More preferred carbohydrate derivatives are those wherein R 2  is methoxy. In particularly preferred carbohydrate derivatives R 3  is methoxy. The most preferred carbohydrate derivative is the one wherein R 4  is methoxy. 
     In the term (1-4C)alkoxy the (1-4C)alkyl group is a branched or unbranched alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, isopropyl, t-butyl, and the like. The most preferred alkyl group is methyl. 
     The counter-ions which compensate the charged moieties are pharmaceutically acceptable counter-ions, like hydrogen, or more preferably alkali or earth-alkali metal ions, like sodium, calcium, or magnesium. 
     The carbohydrate derivatives according to this invention may be prepared according to well known methods described and used for the synthesis of oligosaccharides. In this respect, in particular reference is made to the previously mentioned European patent EP 529,715. A suitable process for the preparation of the carbohydrate derivatives of formula I is characterized by a process wherein protected monosaccharides having different structures are coupled to give protected disaccharides, after which: 
     (a) protected disaccharides of one type are coupled to protected disaccharides of another type to give protected tetrasaccharides, which tetrasaccharides are coupled to a protected monosaccharide to give protected pentasaccharides; or 
     (b) protected monosaccharides are coupled to protected disaccharides to give protected trisaccharides, which are further coupled to protected disaccharides to give protected pentasaccharides; 
     after which the protective groups are cleaved and free hydroxy groups are sulfated, after which the compound obtained is optionally converted into a pharmaceutically acceptable salt. 
     The monosaccharides are D-glucose, D-mannose, L-idose, D-glucuronic acid or L-iduronic acid, suitably functionalized with the required alkyl groups or by temporarily protective groups. Suitable protective groups are well known in the art. Preferred protective groups include benzyl and acetyl for hydroxy groups, and benzyl for the carboxylate groups of uronic acids. Other protective groups, such as benzoyl, levulinyl, alkoxyphenyl, chloroacetyl, trityl, and the like may be used with equal success. Coupling of the saccharide is performed in a manner known in the art, e.g. deprotection of the 1-position of the glycosyl-donor, and/or activation of this position (e.g. by making a bromide, pentenyl, fluoride, thioglycoside, or trichloroacetimide derivative) and coupling the activated glycosyl-donor with an optionally protected glycosyl-acceptor. 
     For the treatment of venous thrombosis or for the inhibition of smooth muscle cell proliferation the compounds of the invention may be administered enterally or parenterally, and for humans preferably in a daily dosage of 0.001-10 mg per kg body weight. Mixed with pharmaceutically suitable auxiliaries, e.g. as described in the standard reference, Gennaro et al., Remington&#39;s Pharmaceutical Sciences (18th ed., Mack Publishing Company, 1990, see especially Part 8: Pharmaceutical Preparations and Their Manufacture), the compounds may be compressed into solid dosage units, such as pills, tablets, or be processed into capsules or suppositories. By means of pharmaceutically suitable liquids the compounds can also be applied as an injection preparation in the form of a solution, suspension, emulsion, or as a spray, e.g. a nasal spray. 
     For making dosage units, e.g. tablets, the use of conventional additives such as fillers, colorants, polymeric binders and the like is contemplated. In general any pharmaceutically acceptable additive which does not interfere with the function of the active compounds can be used. Suitable carriers with which the compositions can be administered include lactose, starch, cellulose derivatives and the like, or mixtures thereof, used in suitable amounts. 
    
    
     The invention is further illustrated by the following examples. 
     EXAMPLES 
     Preparation of Example I (Compound  32 ) 
     Synthesis of GH Disachharide  16  (Scheme 1+2) 
     Compound  2   
     Compound  1  (60 g; commercially available) was dissolved in N,N-dimethylformamide (858 ml) together with benzyl bromide (50.5 ml). After cooling to +10° C. a 20% aqueous solution of sodium hydroxide was added dropwise. After stirring for 1 hour the temperature was raised to 20° C. and the mixture was stirred another 20 hours. The solution was then poured into a mixture of icewater and toluene and extracted. The organic layer was concentrated and the crude product purified by cristallysation to give 30.0 g of compound  2 . 
     TLC: Rf=0.60, toluene/ethyl acetate: 7/3, v/v 
     Compound  3   
     Compound  2  (26.4 g) was dissolved in N,N-dimethylformamide (211 ml) and cooled in ice. Sodium hydride (2.5 g) was added under nitrogen atmosphere. Then 4-methoxy benzyl chloride (13.3 g) was added dropwise and the mixture was stirred for 1 hour at room temperature. The mixture was then diluted with ethyl acetate, washed with water (2×) and concentrated to give 40.7 g of crude compound  3 . 
     TLC: Rf=0.80, toluene/ethyl acetate: 7/3, v/v 
     Compound  4   
     Compound  3  (34.9 g) was dissolved in 60% aq. acetic acid and stirred for 4 hours at 60° C. The mixture was diluted with toluene and concentrated. Purification by silicagel chromatography gave 26.4 g of compound  4 . 
     TLC: Rf=0.07, toluene/ethyl acetate: 7/3, v/v 
     Compound 5 
     Compound  4  (26.4 g) was dissolved in dichloromethane (263 ml) under nitrogen atmosphere. Trimethyloxonium tetrafluoroborate (11.6 g) and 2,6-di-t-butyl-4-methylpyridine (17.4 g) were added at room temperature. After 4 hours the mixture was poured into ice-water and extracted with dichloromethane. The organic layer was washed with sodium hydrogencarbonate and evaporated. Purification of the crude product by silicagel chromatography gave 18.5 g of compound  5 . 
     TLC: Rf=0.25, toluene/ethyl acetate: 7/3, v/v 
     Compound  7   
     Compound  6  (3-methyl-1,2,4,6-tetraacetyl-idose) (48.4 g) was dissolved in toluene (175 ml). Under nitrogen atmosphere ethanethiol (20 ml) and boron trifluoride diethyl etherate (1M in toluene; 134 ml) were added. After stirring for 1 hour aqueous sodium hydrogencarbonate (400 ml) was added and the mixture was stirred for another hour. The mixture was then poured into ethyl acetate. The organic layer was washed twice with water and concentrated. Purification by silicagel chromatography gave 29.6 g of compound  7 . 
     TLC: Rf=0.45, toluene/ethyl acetate: 6/4, v/v 
     Compound  8   
     Compound  5  (17.5 g) and compound  7  (28.2 g) were dissolved in toluene (525 ml) under nitrogen atmosphere. After addition of powdered molsieves (4 Å) the reaction was cooled to −20° C. A freshly prepared 0.1 M solution of N-iodosuccinimide (17.4 g) and trifluoromethanesulphonic acid (1.38 ml) in dioxane/dichloromethane (1/1 v/v) were added dropwise under continuous nitrogen flux. After 10 minutes the red reaction mixture was filtered and washed successively with aqueous sodium thiosulphate and aqueous sodium hydrogencarbonate. The organic layer was concentrated in vacuo and 30.0 g of compound  8  isolated. 
     TLC: Rf=0.45, dichloromethane/ethyl acetate: 8/3, v/v 
     Compound  9   
     Compound  8  (30.0 g) was dissolved in 460 ml methanol/dioxane (1/1, v/v) and potassium butanolate was added for saponification. After 15 minutes the mixture was neutralised with Dowex 50WX8H + -form and concentrated in vacuo. Purification was established by silicagel chromatography to give 17.4 g of compound  9 . 
     TLC: Rf=0.25, dichloromethane/methanol: 95/5, v/v 
     Compound  10   
     Under nitrogen atmosphere compound  9  (17.4 g) was dissolved in N,N-dimethyl-formamide (77 ml). 1,2-dimethoxypropane (26 ml) and p-toluenesulfphonic acid where added and the mixture was stirred for 30 minutes. Diluting the mixture with aqueous sodium hydrogencarbonate and extracting it with ethyl acetate gave 19.7 of compound  10  after evaporation of the solvent. 
     TLC: Rf=0.45, dichloromethane/methanol: 95/5, v/v 
     Compound  11   
     Compound  10  (18.5 g) was dissolved in N,N,-dimethylformamide (24.4 ml) and cooled to 0° C. Under nitrogen atmosphere sodium hydride (1.47 g; 60% dispersion in oil) and iodomethane (2.36 ml) where added. After 1 hour excess of sodium hydride was neutralised, the mixture extracted with dichloromethane and concentrated to give 20.0 g of compound  11 . 
     TLC: Rf=0.85, dichloromethane/methanol: 95/5, v/v 
     Compound  12   
     Compound  11  (18.4 g) was dissolved in dichloromethane (838 ml) and water (168 ml). 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (7.1 g) was added and the mixture was stirred for 18 hours at 4° C. The mixture was poured into aqueous sodium hydrogencarbonate and extracted with dichloromethane. Concentration of the organic layer gave 12.7 g of compound  12 . 
     TLC: Rf=0.40, dichloromethane/methanol: 95/5, v/v 
     Compound  13   
     Compound  12  was converted to the title compound according to the same procedures described for the preparation of compound  11 . 
     TLC: Rf=0.48, toluene/ethyl acetate: 1/1, v/v 
     Compound  14   
     After dissolving compound  13  (2.5 g) in acetic acid (14.6 ml) and water (6.1 ml) the mixture was stirred overnight at roomtemperature. Coevaporation with toluene and purification by silicagel chromatography gave 1.9 g of compound  14 . 
     TLC: Rf=0.31, ethyl acetate, v/v 
     Compound  15   
     To a solution of compound  14  (1.7 g) in dichloromethane (9 ml) were added 2,2,6,6-tetramethyl-1-piperidinyloxy (5 mg), saturated sodium hydrogen carbonate solution (5.8 ml), potassium bromide (32 mg) and tetrabutylammonium chloride (42 mg). The mixture was cooled to 0° C. and a mixture of saturated sodium chloride solution (6.5 ml) saturated sodium hydrogen carbonate solution (3.2 ml) and sodium hypochlorite (1.3 M; 7.3 ml) was added during 15 minutes. After 1 hour stirring the mixture was diluted with water and extracted (3 times) with dichloromethane. The organic layer was washed with brine, dried on magnesium sulfate, filtered and evaporated to dryness to give 1.74 g of crude compound  15 . 
     TLC: Rf=0.14, dichloromethane/methanol: 9/1, v/v 
     Methyl O-(benzyl 2,3-Di-O-methyl-α-L-idopyranosyluronate)-(1→4)-2-O-benzyl-3,6-Di-O-methyl-α-D-glucopyranoside  16   
     To a solution of 1.74 g of compound  15  in N,N-dimethylformamide was added under nitrogen atmosphere 1.68 ml of benzylbromide and 1.1 g of potassium hydrogen carbonate. After stirring the solution for 90 minutes water was added and the mixture extracted with ethyl acetate. After evaporation of the organic layer and purification by silicagel chromatography 1.64 g of compound  16  was isolated. 
     TLC: Rf=0.50, toluene/ethyl acetate: 1/1, v/v 
     Synthesis of EF-disaccharide  25  (Scheme 2+3) 
     Compound  17   
     Compound  12  (10.5 g) was dissolved in dry N,N-dimethylformamide (178 ml), cooled to 0° C. under nitrogen atmosphere. Sodium hydride (1.91 g; 60% dispersion in oil) was added after which benzylbromide (3.3 ml) was added dropwise. After 30 minutes the reaction was complete and the excess sodium hydride was neutralised. Water was added and the mixture extracted twice with ethyl acetate. Evaporation of the solvent gave 13.6 g of compound  17 . 
     TLC: Rf=0.50, toluene/ethyl acetate: 1/1, v/v 
     Compound  18   
     Compound  17  was converted to the title compound according the same procedures described for the preparation of compound  14 . 
     TLC: Rf=0.68, dichloromethane/methanol: 9/1, v/v 
     Compound  19   
     Compound  18  was converted to the title compound according the same procedures described for the preparation of compound  15 . 
     TLC: Rf=0.14, dichloromethane/methanol: 9/1, v/v 
     Compound  20   
     Compound  19  was converted to the title compound according the same procedures described for the preparation of compound  16 . 
     TLC: Rf=0.38, dichloromethane/methanol: 85/15, v/v 
     Compound  21   
     Compound  20  (9.9 g) was dissolved in 300 ml methanol (dry) and refluxed under nitrogen atmosphere. A 1 M solution of sodium methoxide (65.2 ml) was added dropwise and stirred for 3 hours. The temperature was then cooled to room temperature and 1N sodium hydroxide (22.2 ml) was added and stirred for 90 minutes. Neutralisation with Dowex 50WX8H +  form and evaporation of the solvents gave the crude residue. 
     N,N-dimethylformamide (192 ml) and powdered molsieves (4 Å) were added under nitrogen atmosphere. Potassium hydrogencarbonate (3.2 g) and benzylbromide (4.8 ml) were added and the mixture stirred for 5 hours after which ethyl acetate was added and the mixture washed with water. Evaporation of the solvent and purification of the rude product by silicagel chromatography gave 6.19 g of compound  21  and 1.88 g of recovered compound  20 . 
     TLC: Rf=0.74, dichloromethane/methanol: 9/1, v/v 
     Compound  22   
     Compound  21  (6.2 g) was dissolved in 40 ml of dioxane. Levulinic acid (2.1 g), dicyclohexyl carbodiimide (3.75 g) and 4-dimethylaminopyridine (0.2 g) where added and the mixture stirred for 2 hours under nitrogen atmosphere. Ether (95 ml) was added and the precipitate filtered off. The organic layer was washed with aqueous potassium hydrogensulphate and concentrated. Cristallisation from diethyl ether/heptane gave 6.2 g of compound  22 . 
     TLC: Rf=0.26, dichloromethane/acetone: 95/5, v/v 
     Compound  23   
     Compound  22  (6.1 g) was dissolved in acetic anhydride (256 ml) under nitrogen atmosphere and cooled to −20° C. A mixture of sulphuric acid (4.9 ml) in acetic anhydride (49 ml) was added dropwise during 30 minutes. After 60 minutes sodium acetate was added until the pH of the mixture was neutral. Ethyl acetate and water where added and the organic layer concentrated. Purification by silicagel chromatography gave 4.2 g of compound  23 . 
     TLC: Rf=0.63, dichloromethane/acetone: 9/1, v/v 
     Compound  24   
     Compound  23  (4.2 g) was dissolved in tetrahydrofuran (42 ml) and piperidine (4.1 ml) was added. The mixture was stirred overnight at room temperature. Ethyl acetate was added and the mixture washed with 0.5 N hydrochloric acid. The organic layer was concentrated and the residue purified by silicagel chromatography to give 3.2 g of compound  24 . 
     TLC: Rf=0.33, dichloromethane/ethyl acetate: 1/1, v/v 
     O-(benzyl 2,3-di-O-methyl-4-O-levulinoyl-β-D-glucopyranosyluronate)-(1→4)-3-O-acetyl-2-O-benzyl-6-O-methyl-D-glucopyranosyl Trichloroacetimidate  25   
     Compound  24  (1.59 g) was dissolved in dichloromethane under nitrogen atmosphere. Trichloroacetonitril (1.1 ml) and cesium carbonate (72 mg) were added and the mixture stirred for 1 hour. The cesium carbonate was filtered off and the filtrate concentrated. Purification by silicagel chromatography gave 1.57 of compound  25 . 
     TLC: Rf=0.60, toluene/ethyl acetate: 3/7, v/v 
     Synthesis of EFGH-tetrasaccharide  27  (Scheme 4) 
     Compound  26   
     A mixture of compound  16  (0.530 mg) and compound  25  (0.598 mg) was dried by coevaporation with dry toluene and dissolved in 8.2 ml of dry dichloromethane. Powdered molsieves (4 Å) was added and the mixture was cooled to −20° C. under nitrogen atmosphere and stirred for 30 minutes. To the resulting suspension was added trimethylsilyl trifluoromethanesulphonate (15 mol % in relation to compound  25 ). After stirring for 10 minutes sodium hydrogencarbonate was added, the mixture was filtered and water and dichloromethane were added. The organic layer was then extracted, concentrated and the crude product purified by silicagel chromatography to give 0.62 g of compound  26 . 
     TLC: Rf=0.47, toluene/ethyl acetate: 3/7, v/v 
     Methyl-O-(Benzyl 2,4-di-O-dimethyl-β-D-glucopyranosyluronate)-(1-4)-O-(3-O-acetyl-2-O-benzyl-6-O-methyl-α-D-glucopyranosyl)-(1→4)-O-(benzyl 2,3-di-O-methyl-α-L-idopyranosyluronate)-(1→4)-2-O-benzyl-3,6-di-O-methyl-α-D-glucopyranoside  27   
     To a solution of compound  26  (0.58 g) in pyridine was added a mixture of 2.76 ml acetic acid, 0.32 ml hydrazine hydrate in 2.1 ml pyridine. After 9 minutes, water and dichloromethane where added and the organic layer washed with 1 N hydrochloric acid and aqueous sodium hydrogencarbonate. Purification by silicagel chromatography gave 0.27 g of compound  27 . 
     TLC: Rf=0.45, toluene/ethyl acetate: 3/7, v/v 
     Synthesis of DEFGH-pentasaccharide  32  (Scheme 4+5) Example I 
     Compound  29   
     A mixture of compound  27  (150 mg) and 76 mg of compound  28  (Ref: Bioorganic &amp; Medicinal Chemistry, vol 2, no 11, 1267-1280, 1994) was dried by coevaporation with dry toluene and dissolved in 7.5 ml of dry dichloromethane. Under nitrogen atmosphere powdered molsieves (4 Å) was added and the mixture cooled to −20° C. After stirring for 20 minutes trimethylsilyl trifluoromethanesulphonate (15 mol % in relation to compound  28 ) was added. After stirring for 30 minutes aqueous sodium hydrogen-carbonate was added. The mixture was filtered and the organic layer was washed with water. Concentration of the solvent gave the crude product which was purified by silicagel chromatography to give 136 mg of compound  29 . 
     TLC: Rf=0.33, toluene/ethyl acetate: 4/6, v/v 
     Compound  30   
     Compound  29  was diluted in a mixture of t-butanol (8 ml) and water (1 ml). To the solution 122 mg of 10% palladium on charcoal was added and the mixture was stirred overnight under hydrogen atmosphere. The palladium on charcoal was filtered and the solution was concentrated to give 84.5 mg of compound  30 . 
     TLC: Rf=0.49, ethyl acetate/pyridine/acetic acid/water: 13/7/1.6/4, v/v 
     Compound  31   
     Compound  30  (84.5 mg) was dissolved in 5 ml of 0.3 N sodium hydroxide and stirred and stirred for 3 hours. The reaction mixture was then neutralised with 0.5 N hydrochloric acid and evaporated. The residu was desalted on a Sephadex G25 column with water/acetonitril: 9/1 (v/v) and passed through a short column of Dowex 50WX8H + -form. After evaporation 75.6 mg of compound  31  was isolated. 
     TLC: Rf=0.43, ethyl acetate/pyridine/acetic acid/water: 8/7/1.6/4, v/v 
     Methyl O-(2,3,4-tri-O-methyl-6-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-β-D-glucopyranosyluronic acid)-(1→4)-O-(6-O-methyl 2,3-di-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-α-L-idopyranosyluronic acid)-(1→4)-3,6-di-O-methyl-2-O-sulfo-α-D-glucopyranoside, Hexasodium Salt  32   
     Compound  31  (30.6 mg) was dissolved in 2.15 ml N,N-dimethylformamide (destilled; dry) and triethylamine sulfurtrioxide complex (120 mg) was added under nitrogen atmosphere. The mixture was stirred overnight at 55° C. A suspension of sodium hydrogencarbonate in water was added. The mixture was stirred for 1 hour at room temperature and the solvent evaporated. The residu was dissolved in water (2 ml) and desalted on a Sephadex G25-column with water/acetonitril: 9/1 (v/v). The isolated product was eluted on a Dowex 50WX8Na + -column with water to give the 42.5 mg of pentasaccharide compound  32 . 
     [α] 20   D =+56.8 (c=1, H 2 O) 
     Anomeric protons chemical shifts: 5.32, 5.22, 4.97, 4.89 and 4.24 ppm. 
     Preparation of Example II (Compound  38 ) 
     Synthesis of EFGH-tetrasaccharide  34  (Scheme 4) 
     Compound  33   
     Compound  25  and compound  20  were coupled to give the title compound according the same procedures described for the preparation of compound  26 . 
     TLC: Rf=0.47, toluene/ethyl acetate: 3/7, v/v 
     Methyl-O-(Benzyl 2,4-di-O-dimethyl-β-D-glucopyranosyluronate)-(1→4)-O-(3-O-acetyl-2-O-benzyl-6-O-methyl-α-D-glucopyranosyl)-(1→4)-O-(benzyl 2,3-di-O-methyl-α-L-idopyranosyluronate)-(1→4)-2,3-di-O-benzyl-6-O-methyl-α-D-glucopyranoside  34   
     Compound  33  was converted to the title compound according the same procedures described for the preparation of compound  27 . 
     TLC: Rf=0.39, heptane/ethyl acetate: 3/7, v/v 
     Synthesis of DEFGH-pentasaccharide  38  (Scheme 4+5) (Example II) 
     Compound  35   
     Compound  34  and compound  28  were coupled to give the title compound according the same procedures described for the preparation of compound  29 . 
     TLC: Rf=0.60, toluene/ethyl acetate: 3/7, v/v 
     Compound  36   
     Compound  35  was converted to the title compound according the same procedure described for the preparation of compound  30 . 
     TLC: Rf=0.39, ethyl acetate/pyridine/acetic acid/water: 13/7/1.6/4, v/v 
     Compound  37   
     Compound  36  was converted to the title compound according the same procedures described for the preparation of compound  31 . 
     TLC: Rf=0.32, ethyl acetate/pyridine/acetic acid/water: 13/7/1.6/4, v/v 
     Methyl O-(2,3,4-tri-O-methyl-6-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-β-D-glucopyranosyluronic acid)-(1→4)-O-(6-O-methyl-2,3-di-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-α-L-idopyranosyluronic acid)-(1→4)-6-O-methyl-2,3-di-O-sulfo-α-D-glucopyranoside, Heptasodium Salt  38   
     Compound  37  was converted to the title compound according the procedures described for the preparation of compound  32 . 
     [α] 20   D =+53.6 (c=1, H 2 O) 
     Anomeric protons chemical shift: 5.32, 5.23, 4.99, 4.9 and 4.23 ppm. 
     Preparation of Example III (Compound  56 ) 
     Synthesis of GH-disaccharide  50  (Scheme 1+2) 
     Compound  39   
     Compound  2  was converted to the title compound according the same procedures described for the preparation of compound  11 . 
     TLC: Rf=0.52, dichloromethane/acetone: 98/2 v/v 
     Compound  40   
     Compound  39  (32.0 g) was dissolved in methanol (538 ml). p-Toluenesulfonic acid (1.57 g) was added and the mixture was stirred for 1.5 hour at room temperature. After neutralization with triethylamine the mixture was concentrated. Purification by silicagel chromatography gave 11.9 g of compound  40 . 
     TLC: Rf=0.56, dichloromethane/methanol: 9/1, v/v 
     Compound  41   
     Compound  40  was converted to the title compound according the same procedures described for the preparation of compound  5 . 
     TLC: Rf=0.18, toluene/ethyl acetate: 7/3, v/v 
     Compound  42   
     Compound  6  was converted to the title compound according the same procedure described for compound  24 . 
     Compound  43   
     Compound  42  was converted to the title compound according the same procedures described for the preparation of compound  25 . 
     Compound  44   
     The coupling reaction of compound  43  with compound  41  was performed under the same conditions as described for compound  26 . 
     TLC: Rf=0.28, toluene/ethyl acetate: 6/4, v/v 
     Compound  45   
     Compound  44  was converted to the title compound according the same procedures described for the preparation of compound  9 . 
     TLC: Rf=0.09, toluene/ethyl acetate: 3/7, v/v 
     Compound  46   
     Compound  45  was converted to the title compound according the same procedures described for the preparation of compound  10 . 
     TLC: Rf=0.52, ethyl acetate 
     Compound  47   
     Compound  46  (10.4 g) was dissolved in pyridine (dry) (102 ml) under nitrogen atmosphere. A mixture of acetic anhydride (34 ml) and pyridine (dry) (102 ml) and 10 mg of 4-dimethylaminopyridine was added. After stirring for 1 hour at room temperature the reaction mixture was concentrated and coevaporated with dry toluene to give 11.9 g of compound  47 . 
     TLC: Rf=0.50, toluene/ethyl acetate: 1/1, v/v 
     Compound  48   
     After dissolving compound  47  (11.9 g) in methanol (90 ml), 180 mg of p-toluenesulphonic acid was added and the mixture was stirred overnight at room temperature. The mixture was diluted with ethyl acetate, washed with water (2×) and concentrated. Purification of the crude product by silicagel chromatography gave 6.2 g of compound  48 . 
     TLC: Rf=0.28, toluene/ethyl acetate: 3/7, v/v 
     Compound  49   
     Compound  48  was converted to the title compound according the same procedures described for the preparation of compound  15 . 
     TLC: Rf=0.24, dichloromethane/methanol: 9/1, v/v 
     Methyl O-(Benzyl 2-O-acetyl-3-O-methyl-α-L-idopyranosyluronate)-(1→4)-2-O-benzyl-3,6-di-O-methyl-α-D-glucopyranoside  50   
     Compound  49  was converted to the title compound according the same procedures described for the preparation of compound  16 . 
     TLC: Rf=0.37, dichloromethane/methanol: 9/1, v/v 
     Synthesis of EFGH-tetrasaccharide  52  (Scheme 4) 
     Compound  51   
     Compound  25  and compound  50  were coupled to give the title compound according the same procedures described for the preparation of compound  26 . 
     TLC: Rf=0.52, dichloromethane/methanol: 98/2, v/v 
     Methyl-O-(Benzyl 2,4-di-O-dimethyl-β-D-glucopyranosyluronate)-(1→4)-O-(3-O-acetyl-2-O-benzyl-6-O-methyl-α-D-glucopyranosyl-(1→4)-O-(benzyl 2-O-acetyl-3-O-methyl-α-L-idopyranosyluronate)-(1→4)-2-O-benzyl-3,6-di-O-methyl-α-D-glucopyranoside  52   
     Compound  51  was converted to the title compound according the same procedures described for the preparation of compound  27 . 
     TLC: Rf=0.26, dichloromethane/methanol: 98/2, v/v 
     Synthesis of DEFGH-pentasaccharide  56  (Scheme 4+5) (Example III) 
     Compound  53   
     Compound  28  and compound  52  were coupled to give the title compound according the same procedures described for the preparation of compound  29 . 
     TLC: Rf=0.63, dichloromethane/methanol: 98/2, v/v 
     Compound  54   
     Compound  53  was converted to the title compound according the same procedures described for the preparation of compound  30 . 
     TLC: Rf=0.51, dichloromethane/methanol: 8/2, v/v 
     Compound  55   
     Compound  54  was converted to the title compound according the same procedures described for the preparation of compound  31 . 
     TLC: Rf=0.32, ethyl acetate/pyridine/acetic acid/water: 10/7/1.6/4, v/v 
     Methyl O-(2,3,4-tri-O-methyl-6-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-β-D-glucopyranosyluronic acid)-(1→4)-O-(6-O-methyl-2,3-di-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(3-O-methyl-2-O-sulfo-α-L-idopyranosyluronic acid)-(1→4)-3,6-di-O-methyl-2-O-sulfo-α-D-glucopyranoside, Heptasodium Salt  56   
     Compound  55  was converted to the title compound according the same procedures described for the preparation of compound  32 . 
     [α] 20   D =+50.2 (c=1.05, H 2 O) 
     Anomeric protons chemical shifts: 5.32, 5.29 and 4.89 ppm. 
     Preparation of Example IV (Compound  80 ) 
     Synthesis of EF-disaccharide  66  (Scheme 6) 
     Compound  58   
     Et 3 N (43 ml, 0.3 mmol), 4-dimethylaminopyridine (156 mg, 1.3 mmol) and Ac 2 O (23 ml, 0.29 mol) were added to a solution of  57  (36.2 g, 0.128 mol) (Petroni et al. Aust. J. Chem. 1988, 41, 91-102) in CH 2 Cl 2  (360 ml). After 30 min. the mixture was successively washed with 5% aq KHSO 4 , H 2 O, saturated aqueous NaHCO 3 , H 2 O and dried (Na 2 SO 4 ). The evaporation gave crude  58 : TLC, R f 0.41, 3:1 cyclohexane/EtOAc. 
     Compound  59   
     Ethanolamine (4.9 ml, 80 mmol)) was added, at +4° C., to a solution of crude  58  (11.8 g, 32 mmol) in THF (220 ml). After 16 h at +4° C., trichloroacetonitrile (65 ml, 644 mmol) and K 2 CO 3  (8.3 g, 64.4 mmol) were added under argon to the above mixture. After 16 h at room temperature, the solution was filtered and concentrated. Column chromatography (4:1 cyclohexane/EtOAc) afforded  59  in 79% yield: TLC R f 0.49, 1:1 cyclohexane/EtOAc. 
     Compound  61   
     A solution of trimethylsilyl triflate (0.04 M in CH 2 Cl 2 ; 96 ml, 3.8 mmol) was added dropwise, under argon, to a cooled (−20° C.) solution of the donor imidate  59  (11.93 g, 25 mmol) and acceptor  60  (9.2 g, 19.8 mmol) (P. J. Garegg, H. Hultberg Carbohydr. Res. 1961, 93, C10) in CH 2 Cl 2  (190 ml) containing 4 Å powdered molecular sieves. After 30 minutes solid NaHCO 3  was introduced, and the solution was filtered, washed with water, dried (Na 2 SO 4 ) and concentrated. The residue crystallized in Et 2 O gave  61  (82% yield). mp: 138° C. 
     Compound  62   
     Sodium (373 mg, 0.65 mmol) was added to a solution of compound  61  (1 g, 1.3 mmol) in 2:1 methanol/CH 2 Cl 2  (ml). The mixture was stirred for 1 h at room temperature, and then neutralized with Dowex 50 H +  resin, filtered and concentrated to afford crude  62 . 
     Compound  63   
     NaH (40.5 mg, 1.68 mmol) was added portionwise to a cooled (0° C.) solution of crude  62  (950 mg,) and MeI (0.1 ml, 1.55 mmol) in DMF (9 ml). After 2 h at room temperature, MeOH was introduced, and the mixture was poured into H 2 O. The product was extracted with EtOAc, washed with H 2 O, dried (Na 2 SO 4 ) and concentrated. Column chromatography (3:1 cyclohexane/EtOAc) of the residue gave pure  63  (86% yield from  62 ): mp 137° C. (Et 2 O). 
     Compound  64   
     A solution of  63  (1.16 g, 1.56 mmol) in 1:3 H 2 O/MeOH (40 ml) was heated at 80° C. in presence of p-toluenesulfonic acid (230 mg, 1.56 mmol). After 3 h, the mixture was neutralized with NaHCO 3  and concentrated. Column chromatography (3:1 cyclohexane/acetone) of the residue gave  64  (89% yield): TLC R f 0.28, 2:1 cyclohexane/acetone. 
     Methyl O-(benzyl 2,3-di-O-methyl-β-D-glucopyranosyluronate)-(1→4)-2,3,6-tri-O-benzyl-α-D-glucopyranoside  66   
     To a solution of  64  (860 mg, 1.3 mmol) in CH 2 Cl 2  (4 ml) were added 2,2,6,6-tetramethyl-1-piperidinyl oxy (2.3 mg), saturated aqueous NaHCO 3  (2.5 ml), KBr (13.5 mg) and tetrabutylammonium chloride (18 mg). To the above cooled (0° C.) solution was added the mixture of solutions saturated aqueous NaCl (2.8 ml), saturated aqueous NaHCO 3  (1.4 ml) and NaOCl (1.3 M, 3.2 ml). After 1 h, the mixture was extracted with CH 2 Cl 2 , washed with H 2 O, dried (Na 2 SO 4 ) and concentrated to give the crude acid  65 . 
     The crude above acid in DMF was treated with BnBr (1.6 ml, 13 mmol) and KHCO 3  (650 mg, 6.5 mmmol). After 16 h, the product was extracted with EtOAc, washed with H 2 O, dried (Na 2 SO 4 ) and concentrated to give  66  in 77% yield. 
     Synthesis of DEF-trisaccharide  70  (Scheme 7) 
     Compound  67   
     A solution of trimethylsilyl triflate (0.04 M in CH 2 Cl 2 ; 1.88 ml, 0.075 mmol) was added dropwise, under argon, to a cooled (−20° C.) solution of 6-O-acetyl-2,3,4-tri-O-methyl-D-glucopyranose trichloroacetimidate  28  (290 mg, 0.711 mmol) (P. Westerduin et al. Bioorg Med. Chem. 1994, 2, 1267-83) and acceptor  66  (300 mg, 0.4 mmol) in CH 2 Cl 2  (20 ml) containing 4 Å powdered molecular sieves. After 30 minutes solid NaHCO 3  was introduced, and the solution was filtered and concentrated. Column chromatography (3:1 toluene/EtOAc) of the residue gave pure  67  (56% yield): TLC R f 0.32, 3:2 toluene/EtOAc. 
     Compound  68   
     To a solution of  67  (201 mg, 0.20 mmol) in acetic anhydride (7.6 ml) at −20° C. a mixture of concentrated sulfuric acid in acetic anhydride (1.5 ml, 0.1:1 v/v) was added. After stirring 1 h sodium acetate (780 mg) was added. The mixture was diluted was EtOAc, washed with H 2 O, dried (Na 2 SO 4 ) and concentrated to give, after column chromatography (1:1 toluene/EtOAc),  68  (82% yield): TLC R f 0.32, 1:1 toluene/EtOAc. 
     Compound  69   
     Benzylamine (0.58 ml, 5.26 mmol) was added to a solution of the  68  (125.4 mg) in THF (5 ml). After 7 h at room temperature the solution was washed with 1 M aqueous HCl, H 2 O, dried, and concentrated. Column chromatography (3:2 toluene/EtOAc) afforded pure  69  (75% yield): TLC R f 0.33, 2:3 toluene/EtOAc. 
     O-(6-O-acetyl-2,3,4-tri-O-methyl-α-D-glucopyranosyl)-(1→4)-O-(benzyl 2,3-di-O-methyl-β-D-glucopyranosyluronate)-(1→4)-3,6-di-O-acetyl-2-O-benzyl-D-glucopyranosyl Trichloroacetimidate  70   
     Trichloroacetonitrile (69 μl, 0.675 mmol), and cesium carbonate (66 mg, 0.202 mmol), were added under argon to a solution of  69  (89.2 mg, 0112 mmol) in CH 2 Cl 2  (2 ml). After 2 h the solution was filtered and concentrated. Column chromatography of the residue (1:1 toluene/EtOAc) afforded  70  (88% yield): TLC R f 0.44, 1:1 toluene/EtOAc. 
     Synthesis of GH-disaccharide  76  (Scheme 2) 
     Compound  72   
     Sodium methoxide (570 mg, 106 mmol) was added to a solution of compound  71  (2.5 g, 3.53 mol) (M. Petitou er al. J. Med. Chem. 1997, 40, 1600-1607) in 1:1 methanol/CH 2 Cl 2  (35 ml). After 2 h Dowex 50 H +  resin was introduced until neutralisation and filtered. After concentration, column chromatography (2:1 cyclohexane/EtOAc) of the residue gave  72  (100% yield): TLC R f 0.32, 2:1 cyclohexane/EtOAc. 
     Compound  73   
     MeI (0.41 ml, 6.61 mmol) was added, at 0° C., to a solution of  72  (2 g, 3.3 mmol), and NaH (0.12 g, 5 mmol), in THF (20 ml). After 2 h MeOH was introduced dropwise, and after 15 min the product was extracted with CH 2 Cl 2 . The solution was washed with H 2 O, dried (Na 2 SO 4 ), and concentrated. Column chromatography (5:1 cyclohexane/EtOAc) gave pure  73  (89% yield): [α] D  +12° (c 1; CH 2 Cl 2 ). 
     Compound  74   
     Aqueous CF 3 COOH (70%, 3.14 ml) was added to a solution of  73  (1.76 g, 2.84 mmol) in CH 2 Cl 2  (16 ml). After 50 min at room temperature the solution was diluted with CH 2 Cl 2 , washed with cold saturated aqueous NaHCO 3 , H 2 O, and dried (Na 2 SO 4 ). After concentration, column chromatography (11:2 CH 2 Cl 2 /acetone) of the residue yielded  74  in 88% yield): [α] D  +10° (c 1; CH 2 Cl 2 ). 
     Methyl O-(benzyl 2,3-di-O-methyl-α-L-idopyranosyluronate)-(1→4)-2,6-di-O-benzyl-3-O-methyl-α-D-glucopyranoside  76   
     To a solution of  74  (1.39 g, 2.4 mmol) in THF (8 ml) were added 2,2,6,6-tetramethyl-1-piperidinyl oxy (37.4 mg), saturated aqueous NaHCO 3  (14.4 ml), KBr (120 mg) and tetrabutylammonium chloride (180 mg). To the above cooled (0° C.) solution was added the mixture of solutions saturated aqueous NaCl (2.8 ml), saturated aqueous NaHCO 3  (1.4 ml) and NaOCl (1.3 M, 3.2 ml). After 1 h, the mixture was extracted with CH 2 Cl 2 , washed with H 2 O, dried (Na 2 SO 4 ) and concentrated to give the crude acid  75 . 
     The above crude acid  75  in DMF (31 ml) was treated with BnBr (2.84 ml, 23.9 mmol) and KHCO 3  (1.2 g, 12 mmmol). After 16 h, the product was extracted with EtOAc, washed with H 2 O, dried (Na 2 SO 4 ). After concentration, column chromatography (3:2 cyclohexane/EtOAc) of the residue gave  76  (78% yield from  74 ): [α] D  +7.3° (c 1.1; CH 2 Cl 2 ). 
     Synthesis of DEFGH-pentasaccharide  80  (Scheme 8) (Example IV) 
     Compound  77   
     Trimethylsilyl triflate (170 μL, 0.0068 mmol) was added under argon to a stirred, cooled (−20° C.) solution of imidate  70  (91 mg, 0.097 mmol), and  76  (66.2 mg, 0.097 mmol), in CH 2 Cl 2  (2 ml) containing 4 Å molecular sieves. After 30 min, solid NaHCO 3  (0.1 g) was introduced, and stirring was prolonged overnight. The solution was filtered, washed with H 2 O, dried, and concentrated. Column chromatography (2:1 cyclohexane/acetone) provided the pentasaccharide  77  (71.6% yield): TLC R f 0.4, 2:1 cyclohexane/acetone. 
     Methyl O-(2,3,4-tri-O-methyl-6-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-β-D-glucopyranosyluronic acid)-(1→4)-O-(2,3,6-tri-O-sulfo-α-D-glucopyranosyl)-(1→4)-O-(2,3-di-O-methyl-α-L-idopyranosyluronic acid)-(1→4)-3-O-methyl-2,6-di-O-sulfo-α-D-glucopyranoside, Octasodium Salt  80   
     A solution of  77  (50 mg, 0.032 mmol) in DMF (5 ml) was stirred during 16 h under a weak stream of H 2  in the presence of 10% Pd/C catalyst (50 mg). After filtration, the solution was concentrated to give  78 . 
     Aqueous NaOH (5 M, 0.46 ml) was added to a solution of the above crude compound in MeOH (26 ml). After 5 h Dowex 50 H +  was introduced until neutral pH. The solution was concentrated, and the residue was layered on top of a Sephadex G 25 column eluted with H 2 O. Concentration of the pooled fractions gave crude  79 . 
     Et 3 N/SO 3  complex (174 mg, 0.96 mmol) was added to a solution of the above compound in DMF (6 ml), and the solution was heated at 55° C. for 20 h. NaHCO 3  (0.33 mg dissolved in H 2 O) was then introduced, and the solution was layered on top of a sephadex G 25 column (1.6×100 cm) equilibrated in 0.2 M NaCl. The fractions were pooled, concentrated, and desalted on the same gel filtration column, equilibrated in H 2 O. Lyophilisation then gave pentasaccharide  80  (95% yield from  77 ): [α] D  +49° (c 1; H 2 O). 
     Example V 
     The biological activity of the compounds of the present invention can be determined in the anti-factor Xa assay. 
     Activated Factor X (Xa) is a factor in the coagulation cascade. The anti-Xa activity of compounds of the present invention was assessed by measuring spectrophotometrically the rate of hydrolysis of the chromogenic substrate s-2222 exerted by Xa. This assay for anti-Xa activity in a buffer system was used to assess the IC 50 -value of the test compound. 
     Reference compound: benzamidine 
     Test medium: Tromethamine-NaCl-polyethylene glycol 6000 (TNP) buffer 
     Vehicle: TNP buffer. 
     Solubilisation can be assisted with dimethylsulphoxide, methanol, ethanol, acetonitrile or tert.-butyl alcohol which are without adverse effects in concentrations up to 1% (for DMSO) and 2.5% (for the other solvents) in the final reaction mixture. 
     Technique Reagents* 
     * All ingredients used are of a analytical grade. For aqueous solutions ultrapure water (Milli-Q quality) is used.  
     1. Tromethamine-NaCl (TN) buffer 
     Composition of the buffer: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Tromethamine (Tris) 
                 6.057 
                 g (50 mmol) 
               
               
                   
                 NaCl 
                 5.844 
                 g (100 mmol) 
               
               
                   
                 Water to 
                 1 
                 l 
               
               
                   
                   
               
             
          
         
       
     
     The pH of the solution is adjusted to 7.4 at 37° C. with HCl (10 mmol.l −1 ). 
     2. TNP buffer 
     Polyethylene glycol 6000 is dissolved in TN buffer to give a concentration of 3 g.l −1 . 
     3. S-2222 solution 
     One vial S-2222 (15 mg; Kabi Diagnostica, Sweden) is dissolved in 10 ml water to give a concentration of 1.5 mg.ml −1  (2 mmol.l −1 ). 
     4. Xa solution 
     Bovine Factor Xa Human (71 nKat.vial −1 ; Kabi Diagnostica) is dissolved in 10 ml TNP buffer and then further diluted with 30 ml TNP buffer to give a concentration of 1.77 nKat.ml −1 . The dilution has to be freshly prepared. 
     Preparation of Test and Reference Compound Solutions 
     The test and reference compounds are dissolved in Milli-Q water to give stock concentrations of 10 −2  mol.l −1 . Each concentration is stepwise diluted with the vehicle to give concentrations of 10 −3 , 10 −4  and 10 −5  mol.l −1 . The dilutions, including the stock solution, are used in the assay (final concentrations in the reaction mixture: 3·10 −3 ; 10 −3 ; 3·10 −4 ; 10 −4 ; 3·10 −5 ; 10 −5 ; 3·10 −6  and 10 −6  mol.l −1 , respectively). 
     Procedure 
     At room temperature 0.075 ml and 0.025 ml test compound or reference compound solutions or vehicle are alternately pipetted into the wells of a microtiter plate and these solutions are diluted with 0.115 ml and 0.0165 ml TNP buffer, respectively. An aliquot of 0.030 ml S-2222 solution is added to each well and the plate is pre-heated and pre-incubated with shaking in an incubator (Amersham) for 10 min. at 37° C. Following pre-incubation the hydrolysis of S-2222 is started by addition of 0.030 ml thrombin solution to each well. The plate is incubated (with shaking for 30 s) at 37° C. Starting after 1 min of incubation, the absorbance of each sample at 405 nm is measured every 2 min for a period of 90 min. using a kinetic microtiter plate reader (Twinreader plus, Flow Laboratories). 
     All data are collected in an IBM personal computer using LOTUS-MEASURE. For each compound concentration (expressed in mol.l −1  reaction mixture) and for the blank the absorbance is plotted versus the reaction time in min. 
     Evaluation of responses: For each final concentration the maximum absorbance was calculated from the assay plot. The IC 50 -value (final concentration, expressed in μmol.l −1 , causing 50% inhibition of the maximum absorbance of the blank) was calculated using the logit transformation analysis according to Hafner et al. (Arzneim.-Forsch./Drug Res. 1977; 27(II): 1871-3). 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Anti-factor Xa activity 
               
             
          
           
               
                   
                 Compound (example) 
                 IC 50  (μg · l −1 ) 
               
               
                   
                   
               
               
                   
                 32 (1) 
                 22 
               
               
                   
                 38 (2) 
                 12 
               
               
                   
                 56 (3) 
                 12 
               
               
                   
                 80 (4) 
                 &lt;2 
               
               
                   
                   
               
             
          
         
       
     
     Abbreviations 
     (Ph=phenyl; Me=methyl; Ac=acetyl; Im=trichloroacetimidyl; Bn=benzyl; Bz=benzoyl; Mbn=4-methoxybenzyl; Lev=levulinoyl)