P-D-arabino- wherein R represents a cyano, nitro, aminothiocarbonyl, amidino or an acetamido group and the acid addition salts thereof formed with organic or inorganic acids, if possible as well as pharmaceutical compositions containing them.

The compounds of the invention possess valuable pharmaceutical properties, especially anticoagulant activity, even when administered by the oral route.

Particularly valuable representatives of formula (I) according to the invention are the followingones: 4-cyanophenyl1,5-dithio-a-L-arabinopyranoside 4-cyanophenyl1,5-dithio- (3-L-arabinopyranoside 4-nitrophenyl 1,5-dithio-a-L-arabinopyranoside 4-nitrophenyl 1,5-dithio-ß-L-arabinopyranoside 4- (aminothiocarbonyl) phenyl 1,5-dithio-ß-L-arabinopyranoside 4-amidinophenyl1,5-dithio-ß-L-arabinopyranoside 4-acetamidophenyl1,5-dithio-a-L-arabinopyranoside 4-acetamidophenyl1,5-dithio-ß-L-arabinopyranoside 4-cyanophenyl1,5-dithio-a-D-arabinopyranoside 4-cyanophenyl 1,5-dithio-ß-D-arabinopyranoside 4-nitrophenyl1,5-dithio-a-D-arabinopyranoside 4-nitrophenyl 1,5-dithio-ß-D-arabinopyranoside 4- (aminothiocarbonyl) phenyl 1,5-dithio-a-D-arabinopyranoside 4- (aminothiocarbonyl) phenyl 1,5-dithio-ß-D-arabinopyranoside

4-acetamidophenyl1,5-dithio-a-D-arabinopyranoside Derivatives of the formula (Ia-Id), are not known from the literature. However some 1,5-dithio-D-xylopyranosides of formula (Ie) P-D-xilo- (in which the configuration of the carbohydrate moiety is D-xylose and R represents a nitro or cyano group) possess advantageous anticoagulant activity even when administered orally.

This biological activity decreased significantly in those analoges of formula (Ie) where the oxygen of the carbohydrate moiety was not replaced by sulfur. A similar decrease in activity was observed, when the chirality of the most active b-D-xylopyranosides was changed, i. e. a sugar with a configuration different from D-xylose, or an a-D-anomer was investigated [F.

Bellamy et al.: Eur. J. Med. Chem. 30,101 (1995)].

The aim of the invention was to synthesize such new carbohydrate derivatives which are stronger inhibitors of the coagulation process than the known ones and are orally active too.

Surprisingly it was found, that in contrast to the oxygen containing derivatives, the antithrombotic activity of the sulfur containing pentopyranosides can be substantially increased, by using L-or D-arabinose instead of D-xylose. Both the a-as well as the b- anomers of the so obtained thioglycosides possess a beneficial biological activity. This activity could be further increased by transforming the cyano substituent at C-4 of the aglycon into a carboxylic acid derivative.

The compounds of the invention can be synthesized by different known methods.

(Definitions: The abbreviations used in the description and in the formulas (I)- (XII) are the following according to the literature: Ac = acetyl, Bz = benzol, Me = methyl, Et = ethyl group.). a) The compound of formula (Ia), in which R represents a cyano group, can be prepared e. g. by treatment of a compound of formula (II, RI = CN, R2 = Bz) or the anomeric mixture of the formula (n + III, RI = CN, R2 = Ac) with sodium methoxide in methanol.

The glycoside of formula (II, RI = CN, R2 = Bz) is a new compound and can be prepared e. g. according to method A) when the mercapto groups of the compound of formula (IX) are removed and the so obtained aldehyde of formula (VIII)

is converted into the thiopyranose of formula (VII). The isopropylidene group of the latter is split off, and the so obtained 4-O-benzoyl derivative of formula (VI)

is transformed into the triacetate of formula (V).

The bromide of formula (IV), which is obtained from the latter, is reacted with 4-cyanothiophenol resulting the anomeric mixture of the glycosides of formula <BR> <BR> (II + m, RI = CN, R2 = Bz), which is separated by column chromatography, or according to method B) when the benzoyl group of the 4-0-benzoyl derivative of formula (VI) is split off, the so obtained thiosugar of formula (XII)

is acetylated resulting the tetraacetate of formula (XI), treatment of the latter with hydrogen bromide affords the 1-bromide of formula (X, R = Br) condensation of which with 4-cyanothiophenol gives the anomeric mixture of formula (II + III, R1 = CN, R2 = Ac).

The above reaction sequence for the preparation of the glycoside of formula (II, RI = CN, R2 = Bz) according to procedure A) can preferably be carried out by removing the ethylmercapto groups of the known [E. Bozo et al, Carbohydrate Res., 302,149 (1997)] mercaptal of formula (IX) with boron triftuoride etherate in the presence of mercury (II) oxide. The so obtained aldehyde of formula (VIII) is treated with sodium methoxide in methanol at room temperature, when acyl migration takes place and the thiopyranose of formula (VII) is obtained. The isopropylidene group of the latter is split off by aqueus acetic acid, and the obtained trihydroxy compound of formula (VI) is treated with acetic anhydride in pyridine

affording the mixture of a, (3-triacetate of formula (V). Treatment of the latter with hydrogen bromide in glacial acetic acid affords the bromide of formula (IV), which is reacted in the presence of potassium carbonate in acetone at reflux temperature according to method A) or in the presence of zinc (II) oxide in the mixture of toluene and acetonitrile at room temperature according to method B) with 4-cyanothiophenol, when the anomeric mixture of glycosides of formula (II + III, RI = CN, R2 = Bz) is obtained, which is separated by column chromatography.

The above reaction sequence for the preparation of the mixture of glycosides of formula (II + III, RI = CN, R = Ac) according to procedure B) can preferably be carried out by preparing the tetraester of formula (V) according to procedure A), the ester groups of the latter are split off with sodium methoxide in methanol and the obtained sugar of formula (XII) is converted with acetic anhydride in pyridine into its tetraacetate of formula (XI). The latter is treated with hydrogen bromide in glacial acetic acid and the obtained acetobromo derivative of formula (X, R = Br) is condensed with 4-cyanothiophenol in acetone in the presence of potassium carbonate to give the anomeric mixture of glycosides of formula (II + III, R1 = CN, R2 = Ac).

When the corresponding D-antipode is used as starting material the compounds of formula (Ic), in which R represents a cyano group, can be obtained according to procedure a). b) The compounds of formula (lb), in which R represents a cyano group can be prepared e. g. by treating the compound of formula (III, RI = CN, R2 = Bz) or (III, RI = CN, R = Ac) with sodium methoxide in methanol.

The glycoside of formula (III, RI = CN, R2 = Bz) is a new compound and can be prepared e. g. according to procedure a).

The glycoside of formula (III, RI = CN, R2 = Ac) is a new compound and can be prepared e. g. by spliting off the 1-acetyl group of the compound of formula (XI), the so obtained 1-OH compound is transformed into trichloroacetimidate [X, R = C (=NH) CCl3] and the latter is condensed with 4-cyanothiophenol.

The above reaction sequence for the preparation of glycosides of formula (III, RI = CN, R2 = Ac) can preferably be carried out by using hydrazin acetate to split off the 1-acetyl group of the compound of formula (XI) and the obtained compound of formula (X, R = OH) is transformed into the imidate of formula [X, R = C (=NH) CCl3] with trichloroacetonitril in the presence of potassium carbonate. The latter is condensed with the aglycon in the presence of boron trifluorid etherate at low temperature, preferably at-15 °C, and the desired product is obtained by column chromatography and susequent crystallization from the formed anomeric mixture.

When the corresponding D-antipode is used as starting material the compounds of formula (Id), in which R represents a cyano group, can be obtained according to procedure b). c) The compounds of formula (Ia), in which R represents a nitro group can be prepared e. g. by treating the compound of formula (II, R1 = N02, R2 = Bz) with sodium methoxide in methanol.

The glycoside of formula (II, R1 = N02, R2 = Bz) is a new compound and can be prepared e. g. according to method A) when the bromid of formula (I is reacted with 4-nitrothiophenol in the presence of a base, and the obtained anomeric mixture of formula (II + III, RI = N02, R = Bz) is separated by column chromatography, or according to method B) when the ester of formula (V) is reacted with 4-nitrothiophenol in the presence of a promoter and the product is purifie by crystallization and/or column chromatography.

The reaction sequence mentioned in method A) can preferably be carried out by using potassium carbonate as base and acetone as solvent at reflux temperature.

The reaction sequence mentioned in method B) can preferably be carried out at room temperature, using boron trifluorid etherate as promoter and 1,2-dichloroethane as solvent.

When the corresponding D-antipode is used as starting material the compounds of formula (Ic), in which R represents a nitro group, can be obtained according to procedure c). d) The compounds of formula (Ib), in which R represents a nitro group, can be prepared e. g. by treating the compound of formula (III, RI = N02, R2 = Bz) with sodium methoxide in methanol.

The glycoside of formula (III, RI = N02, R2 = Bz) is a new compound and can be prepared e. g. according to procedure c).

When the corresponding D-antipode is used as starting material the compounds of formula (Id), in which R represents a nitro group, can be obtained according to procedure d). e) The compounds of formula (Ib), in which R represents an aminothiocarbonyl group, can be prepared e. g. by treatment of a compound of formula (Ib), wherein R represents a cyano group, with hydrogen sulfide using an organic base as solvent.

The above reaction can preferably be carried out at room temperature, using 1: 1 mixture of triethylamine-pyridine as solvent.

When the corresponding a-D-or b-D-antipode is used as starting material the compounds of formula (Ic) or (Id), in which R represents an aminothiocarbonyl group, can be obtained according to procedure e). f) The compounds of formula (Ib), in which R represents an amidino group, can be prepared e. g. by treatment of a compound of formula (Ib), wherein R represents an aminothiocarbonyl

group with a methylating agent, and reacting the so obtained compound of formula (Ib), in which R represents a-C (=NH)-SCH3 group, with ammonium acetate.

The above reaction sequence can preferably be carried out by using acetone as solvent and methyl iodide as methylating agent at reflux temperature. g) The compounds of formula (Ia), in which R represents an acetamido group, can be prepared e. g. by reducing a compound of formula (Ia), wherein R represents a nitro group, and removing the ester groups after acetylation using a lower aliphatic alcohol as solvent in the presence of a base.

The above reaction can preferably be carried out by using sodium borohydride for the reduction of the nitro group in the presence of nickel (II) chloride, acetic anhydride in pyridine for the acetylation, and sodium methoxide in methanol for removing the ester groups.

When the corresponding D-antipode is used as starting material the compounds of formula (Ic), in which R represents an acetamido group, can be obtained according to procedure g). h) The compound of formula (Ib), in which R represents an acetamido group, can be prepared e. g. by treating the compound of formula (Ib), wherein R represents a nitro group, according to procedure g).

When the corresponding D-antipode is used as starting material the compounds of formula (Id), in which R represents an acetamido group, can be obtained according to procedure h).

As mentioned in the introduction, the compounds of formula (I) of the invention possess valuable anticoagulant activity.

This anticoagulant activity of the compounds of formula (I) of the invention was determined in vivo, on male SPRD rats, using Pescador's venous thrombosis model [D.

Bagdy et al.: Thromb. Haemost. 68,125 (1992)]. Accordingly 2.0 mg of the individual

compounds was dissolved in 300 pI DMSO and this solution was diluted with 700 p1 <BR> <BR> <BR> <BR> <BR> physiological saline. From this solution a dose of 2.0 mg/kg was administered orally (p. o.) to the animals 3 h prior to provoking the thrombus.

In Table 1 the in vivo antithrombotic activity of several representatives of the compounds of the invention is given in percentage of the inhibition. Reference: 12.5 mg/kg Beciparcil = [4-cyanophenyl (EP 365.397)]. (The reference compound had to be used in 12.5 mg/kg dose, as it did not have antithrombotic activity in 2 mg/kg concentration.) Table I The oral antithrombotic activity of compounds offormula (I) in rats at a dose of 2 mglkg Example R Configuration Anomer Inhib. CN L-arabino a 33% 2CNL-arabino (340% 3 N02 L-arabino a 50% L-arabinoß65%4NO2 5-CS (NH2) L-arabino) 335% 6-C (=NH) NH2 L-arabino ß 43% 7 NHAc L-arabino a 48% L-arabinoß44%8NHAc 9 CN D-arabino a 44% D-arabinoß60%10CN 11 N02 D-arabino a 46% 12 NOs D-arabino ß 44% 13-CS (NH2) D-arabino oc 47% 14-CS (NH2) D-arabino ß 33% 15 NHAc D-arabino 3 5% Reference 44% *

* At a dose of 12.5 mg/kg As can be seen from Table 1 the antithrombotic activity of several representatives of the compounds of formula (I) of the present invention exceeds that of the reference, in certain cases to a significant degree.

For therapeutical purposes, the compounds of the present invention as well as their pharmaceutically acceptable salts can be used as such or suitably in the form of pharmaceutical compositions. These compositions also fall within the scope of the present invention.

These pharmaceutical compositions contain an amount required to exert the therapeutical effect of a compound of formula (I) or its pharmaceutically acceptable salt, in admixture with known carriers, excipients, diluents and/or other additives commonly used in the pharmaceutical practice.

The above carriers, diluents or filling materials can be water, alcohols, gelatine, lactose, saccharose, starch, pectin, magnesium stearate, stearic acid, talcum, various oils of animal or plant origin, furthermore glycols, e. g. propylene glycol or polyethylene glycol. The pharmaceutical excipients can be preservatives, various natural or synthetic emulgeators, dispersing or wetting agents, colouring materials, flavouring agents, materials promoting disintegration and other materials improving the bioavailability of the active ingredient.

For oral administration the antithrombotic compound is formulated in capsules or tablets which may contain excipients such as binders, lubricants, disintegration agents and the

like. For parenteral administration the antithrombotic compound is formulated in a pharmaceutically acceptable diluent, e. g. physiological saline (0.9 %), 5% dextrose, Ringer's solution and the like.

The doses required to exert the therapeutical effect of the compounds according to the invention may be varied depending on the individual condition and age of the patient to be treated and finally these doses are determined by the attending physician. However, for the prevention and/or treatment of diseases, where the application of an anticoagulant is desirable, daily doses of these compounds falling between about 0.1 mg/kg of body weight and about 100 mg/kg of body weight and, preferably between about 0.25 mg/kg of body weight and about 25 mg/kg of body weight are used by the oral or parenteral, e. g. intravenous, route.

The compounds according to the invention and the process for the preparation thereof are illustrated in detail by the following not limiting Examples.

The Rf values given in the experimental part were determined by TLC, using E.

Merck precoated Silica Gel 60 F'-754 plates, with the following solvents: (A) benzene-methanol (9: 1) (B) benzene-methanol (4: 1) (C) hexane-ethyl acetate (2: 1) (D) hexane-ethyl acetate (3: 1) (E) ethyl acetate-pyridine-water-acetic acid (60: 20: 11: 6) Spots were detected by spraying the plates with a 0.02 M solution of iodine and a 0.30 M solution of potassium iodide in 10% aq sulfuric acid solution followed by heating at ca. 200 °C. For column chromatography, Kieselgel 60 was used. Mp's are uncorrected. Optical rotations were determined at 20 °C. NMR spectra were recorded with a Varian XL-400 spectrometer at 400 MHz (1H) and 100 MHz (13C) or with a Bruker AC 250 spectrometer at 250 MHz (1H) and 62.9 MHz (13C) (Me4Si was used as internal standard). Multiplicities of

the 13C NMR spectra were obtained from DEPT experiments. The assignments of the protons were based on homonuclear decoupling and DNOE experiments. Connectivities between identified protons and protonated carbons were determined by HETCOR experiments. MS spectra were recorded with a Finnigan MAT 8430 mass spectrometer. In the case of FAB spectra samples were dissolved in 3-nitrobenzaldehyde or in glycerin.

The"usual processing"during the work-up of acylation reactions, carried out in pyridine means, that if the product did not crystallize on pouring the reaction mixture on ice- water, it was extracted with dichloromethane and the organic solution was washed with 1 M sulfuric acid until a pH of-3 was reached, then with water, with 5% aq sodium hydrogen carbonate and finally with water. Organic solutions were dried over sodium sulfate prior to concentration which was carried out under diminished pressure.

Example 1 4-Cyanophenyl 1, 5dithio-ce-L-arabinopyranoside (la, R = CN) Procedure A) Method A) To a solution of 1.3 g of 4-cyanophenyl arabino-pyranoside (II, R1 = CN, R2 = Bz) in 30 ml of dry methanol 0.1 ml of 1 M methanolic sodium methoxide was added at room temperature. After 1 h, the mixture was neutralized with carbon dioxide, the precipitated crystalls were filtered off, washed with methanol and ether to yield 0.52 g (67%) of the title compound. Mp.: 220-222 °C, Rf (B) = 0 3, [°C] D =-108° (c = 0.5, pyridine). NMR (DMSO-d6), 1H: 4.42 (H-1), 3.88 (H-2), 3.44 (H-3), 4.02 (H-4), 2.70 (H-5a, 5b), 5.44,4.95 and 4.82 (OH), 7.76-7.56 ppm (aromatic H) ; J1 2 7.3, J2,3 7.2, J3,4 2.6 Hz. 13C: 51.0 (C-1), 75.9,73.8 and 72.3 (C-2,3,4), 30.9 (C-5), 144.1-107.7 (aromatic C), 119.0 ppm (CN).

The starting material (II, RI = CN, R2 = Bz) can be prepared e. g. the following way:

Step a) 5-S-Benzoyl-2,3-O-isopropylidene-5-thio-L-arabinose(VIII) To a stirred slurry of 18 g of mercury (II) oxide and 12 ml of boron trifluoride etherate in 400 ml oftetrahydrofuran and 45 ml of water 16.6 g of 5-S-benzoyl-2, 3-O-isopropylidene- 5-thio-L-arabinose diethylmercaptal (IX) [E. Bozó et al., Carbohydrate Res., 302,149 (1997)] was added in 40 ml of tetrahydrofuran dropwise at 0 °C over 30 min. Stirring was continued at 20 °C for 1 h, then the reaction mixture was poured into 500 ml of ether, which contained 20 g of sodium carbonate. The organic layer was washed with 10% aq potassium carbonate until a pH of#9 was reached, then with water and was concentrated after drying to yield 12.4 g (-100%) of the title compound. According to NMR spectroscopy this contains (VIII)-hydrate as well. Rf (C) = 0.5. NMR (CDCl3), (Va) 1H : 9.85 (H-1), 4.52 (H-2), 4.30 (H-3), 3.0-4.6 (H-4,5a, 5b), 1.40 and 1.46 ppm (CMe2); I1,2 1. 2, J2 3 6.5, J3 4 4.2 Hz. 13C: 201.1 (aldehyde), 96.0 ppm (aldehyde-hydrate).

Step b) 4-0-Benzoyl-2, 3-0-isopropylidene-5-thio-J-arabinopyranose (VII) To a stirred solution of 10.9 g of crude aldehyde (VIII) in 50 ml of dry methanol 1 ml of 4 M methanolic sodium methoxide was added at room temperature. After 15 min, the solution was neutralized with carbon dioxide, filtered, and concentrated to yield 105 g (97%) of the title compound, which is a 15: 85 mixture of the a-and ß-anomer. Rf (C) = 0.5. NMR (DMSO-d6), (VIIa) iH: 5.12 (H-1), 4.35 (H-2), 3.45 (H-3), 5.68 (H-4), 3.03 (H-5a), 2.90 (H-5b); J1,2 9.1, J2,3 9. 3, J3,2.3, J4, Sa 2.3, J4, 5b 3 4, Jsa, 5b 14.9 Hz. (VII (3) 5.42 (H-1), 4.55 (H-2), 4.18 (H-3), 5.85 (H-4), 3.32 (H-5a), 2.95 (H-5b), 1.32 and 1.40 (CMe2), 7.45- 8.08 ppm (aromatic H); J2,39.5,J3,42.2,J4,5a1.8,J4,5b3.5,J5a,5b14.9,J1,512.7,

Hz. 13C : 74.6,73.3,71.8 and 69.1 (C-1,2,3,4), 28.5 (C-5), 165.7 (CO), 133.1-128. 3 (aromatic C), 26.4 and 26.6 (CMe2), 108.1 ppm (CMe2).

Step c) 4-0-Benzoyl-5-thio-L-arabinopyranose (VI) To a solution of 3.1 g of 4-O-benzoyl-2, 3-O-isopropylidene-5-thio-L-arabinopyranose (VII) in 30 ml of acetic acid 10 ml of water was added, the solution was boiled on a water bath for 30 min and then concentrated. Toluene was evaporated from the residue twice, and the residue was crystallized with acetone-ether to yield 1.7 g (63%) of the ß-anomer of the title compound. Mp.: 136-138 °C, Rf (D) = 0.4, [a] = +295° (c = 1, acetone), [a] D = +326 ° (5 min) o +250° (4 h), (c = 1, pyridine). Concentration of the mother liquor gave 0.9 g<BR> (34%) of the title compound as a 1: 3 mixture of the a-and ß-anomer. NMR (DMSO-d6), (VIa) 1H: 4.60 (H-1), 3.90 (H-2), 3.65 (H-3), 5.35 (H-4), 2.75-3.10 (H-5a, 5b), 6.14,5.25, 5.05 (OH), ppm (aromatic H); J1 2 6.7, Hz. (VIß) 4.96 (H-1), 3.95 (H-2), 3.88 (H-3), 5.42 (H-4), 3.03 (H-5a), 2.81 H-5b), 5.98,5.08,4.96 (OH), 7.52-8.04 ppm (aromatic H); J2.3,/23-342.4,5a4'45b'S,Ja5b-9,15IH.C: 72.8 and 68.6 (C-1,2,3,4), 26.0 (C-5), 165.5 (CO), ppm (aromatic C).

Step d) 4-0-Benzoyl-1,2,3-tri-0-acetyl-5-thio-L-arabinopyranose (V) To a solution of 2.7 g of 4-0-benzoyl-5-thio-L-arabinopyranose (VI) in 15 ml of pyridine 10 ml of acetic anhydride was added. The mixture was kept at room temperature for 24 h to give after usual processing 3.44 g (87%) of the title compound as a 1: 4 mixture of the a-and (3-anomer. Rf (D) = 0.6; NMR (CDC13), (Va) 1H: 5. 80 (H-1), 5.45 (H-2), 5.28 (H-

3), 5.63 (H-4), 3.31 (H-5a), 2.81 (H-5b), 2.12 (OAc), 7.52-8.04 ppm (aromatic H) J1,2 4.7, J4,5a 9.4, J4,5b 3. 3, J5a, 5b 13.5 Hz. (Vß) 6.24 (H-1), 5.65 (H-2), 5.43 (H-3), 5.85 (H-4), 3.43 (H-5a), 2.88 H-5b), 1.99 (OAc), 7.45-8.15 ppm (aromatic H); J1,23.0, J2, 3 10.8, J3,4 2. 9, J4,5a 1.4, J4,5b 4. 3, J5a 5b 14.9 Hz.

Step e) 4-O 3-di-O-acetyl-5-thio-L-arabinopyranosyl bromide (IV) To a solution of 1 g of 4-O-benzoyl-1, 2, 3-tri-O-acetyl-5-thio-L-arabinopyranose (V) in 10 ml of dry dichloromethane 5 ml of 33% hydrogen bromide in glacial acetic acid was added, the mixture was stirred at room temperature for 1 h, then poured into ice-water. The organic layer was extracted with dichloromethane, the combined organic phases were washed with 5% aq sodium hydrocarbonate, water, dried and concentrated to yield 1.0 g (95%) of the title compound [Rf (C) = 0. 6].

Step f) <BR> <BR> <BR> <BR> 4-Cyanophenyl 4-0-benzoyl-2, 3-di-O-acetyl-1, 5-dithio-a-and-, l3-L-arabino-pyranoside (II<BR> <BR> <BR> <BR> <BR> <BR> <BR> and III, R1 = CN, R2 = Bz) To a srirred solution of the acetobromo derivative (IV) obtained in the previous step in 45 ml of dry acetone, 0.45 g of 4-cyanothiophenol and 0.5 g of potassium carbonate were added. The mixture was refluxed for 1 h, then cooled to room temperature, the precipitated salts were filtered off and washed with acetone. The filtrate was concentrated and the residue was purified by column chromatography (solvent C). Concentration of the first fraction gave 250 mg (22%) of the P-L-anomer of the title compound (III, RI = CN, R2 = Bz). Mp.: 161- 163 °C, Rf (C) = 0.6, la] D = +386° (c = 0.5, chloroform); NMR (CDCl3), 1H: 4.96 (H-1), 5.67 (H-2), 5.48 (H-3), 5.76 (H-4), 3.36 (H-5a), 2.95 (H-5b), 2.02 es 1.98 (OAc), 7.4-8.08

ppm (aromatic H); Jl 2 3 9, J2 3 9.5, J3,4 2.9, J4,5a #2, J4,5b 5. 5, J5a,5b 14. 6 Hz. 13C: 51.4 (C-1), 71.4,69.1 and 68.5 (C-2,3,4), 28.1 (C-5), 169.9,169.5 and 165.4 (CO), 140.4- 110.7 (aromatic C), 118.2 (CN), 20.6,20.6 ppm (COMe).

Concentration of the second fraction yielded 375 mg (33%) of the a-L-anomer of the title compound (II, RI = CN, R2 = Bz) as a syrup, Rf (C) = 0.5, [a] D = +15° (c = 0.5, chloroform); NMR (CDC13), 4.38 (H-1), 5.56 (H-2), 5.15 (H-3), 5.68 (H-4), 3.20-2.98 (H- 5a, 5b), 2.07 and 2.04 (OAc), 7.48-8.05 ppm (aromatic H); J1,2 8.3, J2,3 8.3, J3,4 2. 8, J4,5a 2.9, J4,5b 5.6, J5a,5b #14 Hz. 13C : 50.4 (C-1), 71.7,70.6 and 69.0 (C-2,3,4), 29.6 (C- 5), 169.6,169.5 and 165.4 (CO), 140.1-111.0 (aromatic C), 118.2 (CN), 20.6,20.6 ppm (COMe).

Method B) Steps a)-e) of method B) are identical with steps a)-e) of method A).

Step f) 4-Cyanophenyl 4-0-benzoyl-2, 3-di-0-acetyl-1, 5-dithio-a- and-/. 3-L-arabino-pyranoside (II and III, R1 = CN, R2 = Bz) To a stirred solution of 1 g of acetobromo derivative (IV) in 10 ml of dry toluene and 10 ml of dry acetonitril 0.4 g of 4-cyanothiophenol and 0.3 g of zinc (II) oxide were added.

The mixture was stirred at room temperature for 30 min, filtered through Celite, the filtrate was concentrated and the residue was submitted to column chromatography (solvent C).

Concentration of the first fraction gave 220 mg (19%) of the P-L-anomer of the title compound (III, RI = CN, R2 = Bz), which is identical with the compound of step f) of method A).

Concentration of the second fraction yielded 330 mg (29%) of the a-L-anomer of the title <BR> <BR> <BR> <BR> compound (II, RI = CN, R2 = Bz) as a syrup, which is identical with the compound of step f) of method A).

Procedure B) To a solution of a-1: 1 anomeric mixture of 1.1 g of 4-cyanophenyl 2,3,4-tri-O- acetyl-1,5-dithio-a- and-b-L-arabinopyranoside (II + III, RI = CN, R2 = Ac) in 25 ml of dry methanol 0.1 ml of 1 M methanolic sodium methoxide was added. After 1 h, the reaction mixture was neutralized with carbon dioxide, the precipitated crystalls were filtered off, washed with methanol and ether to yield 220 mg (26%) of the title compound (la), which is identical with the compound obtained according to procedure A). Concentration of the mother liquor and subsequent column chromatography (solvent B) gave 410 mg (54%) of a -1: 3 mixture of the a-and-p-anomer (Ia + Ib, R = CN), but these can not be separated by crystallization or column chromatography.

The starting material (II, RI = CN, R2 = Ac) can be prepared e. g. the following way: Step a) 5-Thio-L-arabinopyranose (XII) To a solution of 8 g of the mixed ester (V) described in step d) of the first example in 50 ml of dry dichloromethane and 50 ml of dry methanol 0.1 ml of 1 M methanolic sodium methoxide was added. After 1 h at room temperature, the mixture was neutralized with carbon dioxide, filtered, the filtrate was concentrated and the residue was crystallized with ethanol to yield 2.4 g (72%) of the title compound. Mp.: 172-174 °C, [a] D = +303° (5 min) o +285° (24 h), (c = 0.5, water).

Step b) 1,2,3,4-Tetra-O-acetyl-5-thio-b-L-arabinopyranose (XI) To a solution of 8.3 g of 5-thio-L-arabinopyranose (XII) in 60 ml pyridine 45 ml of acetic anhydride was added. After 24 h at room temperature the reaction mixture was processed in the usual way to give 16 g (93%) of the title compound. Mp.: 114-116 °C, Rf (C) = 0.5, [a] D = +299° (c = 1, chloroform) Step c) 2,3,4-Tri-O-acetyl-5-thio-L-arabinopyranosyl bromide (X, R = Br) To a solution of 1.67 g of 1,2,3,4-tetra-O-acetyl-5-thio-b-L-arabinopyranose (XI) in 20 ml of dry dichloromethane 6 ml of 33% hydrogen bromide in glacial acetic acid was added and the mixture was stirred at room temperature for 1 h, then processed as desribed in step e) of method A) to yield 1.5 g (84.5%) of the title compound, Rf (C) = 0.7.

Step d) 4-Cyanophenyl 2,3, 4-tri-O-acetyl-1,5-dithio-α- and -ß-L-arabinopyranoside (II + III, R1 = CN, R2 = Ac) To a stirred solution of 1.5 g of acetobromo compound (X, R = Br) obtained in the previous step in 85 ml of dry acetone 0.8 g of 4-cyanothiophenol and 0.85 g of potassium carbonate were added, and the mixture was refluxed for 2 h. After cooling to room temperature, the precipitated salts were filtered off, washed with acetone and the residue obtained upon concentration of the filtrate was submitted to column chromatography (solvent C) to yield 1.1 g (64%) of the title compound, which is a-1: 1 mixture of a-and-ß-anomer (II + III, R = CN). Rf (C) = 0.5.

Example 2 4-Cyanophenyl I, 5-dithio-b-L-arabinopyranoside (lb, R = CN) Method A) To a solution of 1.0 g of 4-cyanophenyl 2, 3-di-O-acetyl-4-O-benzoyl-1,5-dithio-b-L- arabinopyranoside (III, RI = CN, R2 = Bz) in 70 ml of dry methanol 0.2 mi of 1 M methanolic sodium methoxide was added. After 1 h at room temperature, the mixture was neutralized with carbon dioxide, concentrated and the residue was submitted to column chromatography (solvent B) to yield 0.40 g (67%) of the title compound (Ib). Mp.: 181-183 °C, Rf (B) = 0.3, [a] D = +162° (c = 0.5, pyridine). NMR (DMSO-d6), 1H: 4.75 (H-1), 4.06 (H-2), 3.66 (H-3), 4.00 (H-4), 2.94 (H-5a), 2.26 (H-Sb), 5.60,5.10 and 4.90 (OH), 7.74-7.52 ppm (aromatic H); Jl, 2 2. 0, J2 3 5. 3, J3 4 1 8, J4 5a 9 6, J4 5b 3 5, J5a 5b 12 5 Hz 13C: 48.9 (C-1), 73.6,72.6 and 65.9 (C-2,3,4), 29.4 (C-5), 143.6-107.8 (aromatic C), 119.0 ppm (CN).

The starting material (III, RI = CN, R2 = Bz) can be prepared e. g. according to step f) of method A) or B) of procedure A) of the first example.

Method B) To a solution of 200 mg of 4-cyanophenyl 2,3,4-tri-O-acetyl-1,5-dithio-b-L- arabinopyranoside (III, RI = CN, R2 = Ac) in 10 ml of dry methanol 0.05 ml of 1 M methanolic sodium methoxide was added at room temperature. After 1 h the mixture was neutralized with carbon dioxide, concentrated and the residue was submitted to column

chromatography (solvent A) to yield 80 mg (95%) of the title compound (Ib), which was identical with the compound prepared according to method A).

The starting material (III, RI = CN, R2 = Ac) can be prepared e. g. the following way: Step a) 2,3,4-Tri-O-acetyl-5-thio-L-arabinopyranose (X, R = OH) Under argon, to a stirred solution of 1.0 g of 1,2,3,4-tetra-O-acetyl-5-thio-b-L- arabinopyranose (XI) in 30 ml of dry N, N-dimethylformamide 0.4 g of hydrazin acetate was added at room temperature. After 1 h the reaction mixture was poured into a mixture of 50 ml of ethyl acetate and 50 ml of dichloromethane, the organic layer was washed with 2x30 ml of brine, dried and concentrated. The residue was submitted to column chromatography (solvent C) to yield 0.58 g (66%) of the title compound, Rf (C) = 0.3.

Step b) <BR> <BR> <BR> <BR> 0-(2, 3, 4Tri-O-acetyl-5-thio-b-L-arabinopyranosyl) trichloroacetimidate (X R<BR> <BR> <BR> <BR> <BR> <BR> <BR> O-C (=NH) CC13) Under argon, to a stirred solution of the triacetate obtained in the previous step in 10 ml of dry dichloromethane 2.05 ml of trichloroacetonitril and 2.8 g of potassium carbonate were added. Stirring was continued for 24 h, then 20 ml of ether was added, the reaction mixture was filtered through Celite and concentrated. The residue was submitted to column chromatography (solvent C) to yield 0.74 g (86%) of the title compound. Mp.: 148-153 °C, Rf (C) = 0.7, [a] D = +313° (c = 0.5, chloroform). NMR (CDCl3), 1H: 6.30 (H-1), 5.58 (H- 2), 5.40 (H-3), 5.60 (H-4), 3. 34 (H-5a), 2.77 (H-5b), 2.16,2.02 and 2.00 (OAc), 8.65 ppm (NH); J1, 2 3. 1, 12,3 10. 7, J3,4 3. 0, J4, 5a 1. 4, J4,Sb 4. 4, J5a, 5b 14.8 Hz. 13C: 77.1 (C-1),

70.0,68.8 and 68.3 (C-2,3,4), 27.8 (C-5), 170.2,170.0 and 169.8 (CO), 160.8 (C (=NH) CC13), 90.8 (C (=NH) CC13), 21.0,20.7 and 20.6 ppm (COMe).

Step c) 4-Cyanophenyl 2, 3, 4-tri-O-acetyl-1, 5-dithio-b-L-arabinopyranoside (III, RI = CN, R2 = <BR> <BR> <BR> <BR> Ac)<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> Under argon, to a stirred solution of 1.8 g of trichloroacetimidate (X, R = O-C (=NH) CC13) in 80 ml of dry 1,2-dichloroethane 2.08 g of 4-cyanothiophenol and 2.4 g of 4 L molecular sieves were added at room temperature. The reaction mixture was stirred for 30 min, then cooled to-15 °C and 5 ml of 0.1 M boron trifluorid etherate in 1,2- dichloroethane was added. Stirring was continued at-15 °C for 15 min, then the mixture was neutralized with triethylamine (pH-7), filtered through Celite and concentrated. The residue was submitted to column chromatography (solvent C) to yield 1.56 g (92%) of the title compound (II + III, Rl = CN, R2 = Ac), as al: 4 mixture of the a-and-ß-anomer. This was recrystalized from ether to give 1.1 g (65%) of the pure title compound. Mp.: 148-150 °C, Rf (C) = 0.5. NMR (CDCl3), 1H: 4.85 (H-1), 5.55 (H-2), 5.35 (H-3), 5.46 (H-4), 3.18 (H-5a), 2.85 (H-5b), 7.60-7.48 (aromatic H), 2.12,2.06 and 2.00 ppm (OAc); J1 9, 9, J2 2.7, J4,5a 1. 7, J4, 5b 6.0, J5a, 5b 14.4 Hz.

Example 3 4-Nitrophenyl I, 5-dithio-a-L-arabinopyranoside (la, R = N02) To a solution of 530 mg of 4-nitrophenyl 2,3-di-O-acetyl-4-O-benzoyl-1, 5-dithio-a- L-arabinopyranoside (II, Ri = NO2, R2 = Bz) in 25 ml of dry methanol 0.1 ml of 1 M methanolic sodium methoxide was added at room temperature. After 1 h, the mixture was neutralized with carbon dioxide, concentrated and the residue was submitted to column

chromatography (solvent A) to yield 260 mg (79%) of the title compound. Mp. : 175-177 °C, Rf (A) = 0.2, [a] D =-106° (c = 0.5, pyridine). NMR (DMSO-d6), 1H: 4.50 (H-1), 3.95 (H- 2), 3.48 (H-3), 4.04 (H-4), (H-5a, 5b), 5.50,4.98 and 4.84 (OH), 8.12-7.55 ppm (aromatic H); JI, 2 7.0, 3 6.8, J3 4 2.5 Hz.

The starting material (II, RI = NO2, R2 = Bz) can be prepared e. g. the following way: Method A) To a stirred solution of 1 g of 4-O-benzoyl-2, 3-di-O-acetyl-5-thio-L-arabinopyranosyl bromide (fiv), prepared according to step e) of the first example, in 45 ml of dry acetone 0.65 g of 4-nitrothiophenol and 0.5 g of potassium carbonate were added. The reaction mixture was refluxed for 2 h, then cooled to room temperature, the precipitated salts were filtered off and washed with acetone. The filtrate was concentrated and the residue was submitted to column chromatography (solvent C). Concentration of the first fraction gave 210 mg (18%) of the ß-L-anomer of formula (III, RI = NO2, R2 = Bz). Mp.: 173-176 °C, Rf (C) = 0.6, [a ] D = +363° (c = 0.4, chloroform); NMR (CDCl3), lH: 5.02 (H-1), 5.70 (H-2), 5.48 (H-3), 5.75 (H-4), 3.36 (H-5a), 2.96 (H-5b), 2.05 and 2.04 (OAc), ppm (aromatic H) ; J1,23.9,2,39.5,3,43-0,4,5aL5,J4,5b5.6,./5a,5b14.5 Hz. 13C: 51.3 (C-1), 71.4,69.0 and 68.5 (C-2,3,4), 28.2 (C-5), 169.9,169.5 and 165.5 (CO), 146.5-124.0 (aromatic C), 20.6 and 20.6 ppm (COMe).

Concentration of the second fraction yielded 280 mg (24%) of the a-L-anomer of formula (II, RI = N02, R2 = Bz) as syrup, Rf (C) = 0.5, [a] D = +1° (c = 0.5, chloroform); NMR (CDCl3), 1H: 4.42 (H-1), 5.58 (H-2), 5.18 (H-3), 5.70 (H-4), 3.20-3.00 (H-5a, 5b), 2.10 and 2.07 (OAc), 8.18-7.45 ppm (aromatic H); J1,2 8 1, J2, 3 8 1, J3,4 2.6, J4, #3, J4,5b #5.9, J5a, 5b-14. 3 Hz. 13C: 50.3 (C-1), 71.6,70.6 and 69.0 (C-2,3,4), 29.5 (C-5), 169.6,169.5 and 165.4 (CO), 146.8-124.0 (aromatic C), 20.7 and 20.7 ppm (COMe).

Method B) To a stirred solution of 1.14 g of 4-O-benzoyl-1,2,3-tri-O-acetyl-5-thio-L- arabinopyranose (V), prepared according to step d) of the first example, in 15 ml of dry 1,2- dichloroethane 0.62 g of 4-nitrothiophenol and 0.35 ml of boron trifluoride etherate were added at room temperature. After 24 h, the reaction mixture was poured into ice-cooled 30 ml of 5% aq sodium hydrocarbonate, the organic layer was washed with water, dried and concentrated. The residue was crystallized with ether to yield 0.75 g (53%) of the P-L- anomer of formula (III, R1 = N02, R2 = Bz), which was identical with the compound prepared according to method A).

Concentration of the mother liquor and subsequent column chromatography (solvent C) gave 0.4 g (28%) of the a-L-anomer of formula (II, R1 = N02, Ri = Bz) as a syrup, which was identical with the compound prepared according to method A).

Example 4 4-Nitrophenyl 1, 5-dithio-b-L-arabinopyranoside (Ib, R = N02) To a solution of 390 mg of 4-nitrophenyl 2,3-di-O-acetyl-4-O-benzoyl-1,5-dithio-b-L- arabinopyranoside (III, RI = N02, R2 = Bz) in 20 ml of dry methanol 0.1 ml of 1 M methanolic sodium methoxide was added. After 1 h, the mixture was neutralized with carbon dioxide, concentrated and the residue was submitted to column chromatography (solvent A) to yield 200 mg (83%) of the title compound. Mp.: 183-185 °C, Rf (A) = 0.2, [ D = +165° (c = 0.5, pyridine). NMR (DMSO-d6), 1H: 4.82 (H-1), 4.12 (H-2), 3.70 (H-3), 4.05 (H-4), 2.96 (H-5a), 2.32 (H-5b), 5.68,5.08 and 4.88 (OH), 8.15-7.60 ppm (aromatic H) ;i 2 L9, J2, 3 5. 0, J3,4 2.3, J4, 5a 10.3, J4, 5b 3.3, J5a, 5b 12.6 Hz.

The starting material (II, RI = NO2, R2 = Bz) can be prepared e. g. according to method A) or method B) of the third example.

Example 5 (Ib,R=CS(NH2))4-(Aminothiocarbonyl)phenyl1,5-dithio-b-L-arab inopyranoside A solution of 0.87 g of 4-cyanophenyl 1,5-dithio-ß-L-arabinopyranoside (Example 1) in 20 ml of pyridine and 20 ml of triethylamin was saturated with a slow stream of dry hydrogen sulfide for 5 h. The mixture was kept at room temperature overnight and was then concentrated. The residue was recrystallized from methanol to yield 0.89 g (92%) of the title compound. Mp.: 214-218 °C, Rf (B) = 0.2, [a] D = +110° (c = 0.5, pyridine). NMR (DMSO- <BR> <BR> <BR> d6), 1H: 4. 70 (H-1), 4.08 (H-2), 3.66 (H-3), 4.00 (H-4), 2.92 (H-5a), 2.27 (H-5b), 5.40,5.15 and 4.90 (OH), 9.85 and 9.50 (NH2), 7.85-7.30 ppm (aromatic H) ; J1 2 2.2, , 3 5.2, J3, 4 2.3, J4, 5a 10 7, J4, 5b 3.4, J5a, 5b 12.2 Hz.

Example 6 4-Amidinophenyl 1, 5-dithio-3-L-arabinopyranoside (Ib, R = C (=NH)-NH2) To a solution of 0.7 g of 4- (aminothiocarbonyl) phenyl 1,5-dithio-b-L- arabinopyranoside (Ib) (Example 5) in 160 ml of dry acetone 0.4 ml of methyl iodide was added and the reaction mixture was refluxed for 2.5 h. Then 0.4 ml of methyl iodide was added again and reflux was continued for 2.5 h. The residue obtained upon concentration was crystallized with ether to yield 0.5 g (49%) of 4- (imino) (methylthio) methylphenyl 1,5-dithio-ß -L-arabinopyranoside (Ib, R = C (=NH)-SCH3) as a very hygroscopic hydroiodide salt. This was dissolved in 50 ml of ethanol, 0.3 g of ammonium acetate was added and the mixture was stirred at 60 °C for 4 h. The reaction mixture was cooled, concentrated, the residue was dissolved in 10% aq acetic acid and purified on a Varian AD (acetate phase) ion-exchange resin, washing with 5% aq acetic acid. Concentration of the proper fractions yielded 300 mg <BR> <BR> <BR> (66%) of the title compound as its diacetate. Rf (E) = 0.7,

la] = +70° (c = 0.5, MeOH). NMR (DMSO-d6), lH: 4.77 (H-1), 4.08 (H-2), 3.68 (H-3), 4.00 (H-4), 2.92 (H-5a), 2.32 (H-5b), (OH, NH), ppm (aromatic H); Je, 2 5.3,J3,42.3,J4,5a10.6,J4,5b3.4,J5a,5b12.6Hz.2.2,J2,3 Example 7 4-Acetamidophenyl 1, 5-dithio-a-L-arabinopyranoside (Ia, R = NHAc) To a stirred solution of 330 mg 4-nitrophenyl 1,5-dithio-a-L-arabino-pyranoside (Ia, R = NO2) (Example 3) in 75 ml of ethanol 140 mg of sodium borohydride and 15 mg of nickel (II) chloride were added and stirring was continued for 30 min at room temperature.

Then the mixture was neutralized with 4% aq hydrochloric acid, filtered and concentrated.

The residue was dissolved in 15 ml of pyridine and 7.5 ml of acetic anhydride, and was processed in the usual way after 24 h. The residue obtained upon concentration was dissolved in 20 ml of dry methanol and 0.1 ml of 1 M methanolic sodium methoxide was added. After 1 h at room temperature the mixture was neutralized with carbon dioxide, concentrated and the residue was submitted to column chromatography (solvent B) to yield 190 mg (55%) of the title compound. Mp.: 195-198 °C, Rf (B) = 0.2, [a] D =-29° (c = 0.5, pyridine). NMR (DMSO-d6), 1H: 3.96 (H-1), 3.78 (H-2), 3.36 (H-3), 3.95 (H-4), 2.75-2.55 (H-5a, 5b), 2.04 (NAc), 5.23,4.75 and 4.60 (OH), 10.01 (NH), 7.54-7.40 ppm (aromatic H); J1,2 7.5, J2, 3 7-5, J3, 4 2.6, Y5a, 5b 13. 5 Hz.

Example 8 4-Acetamidophenyl l, 5-dithio-b-L-arabinopyranoside (Ib, R = NHAc) When 340 mg of 4-nitrophenyl 1,5-dithio-ß-L-arabinopyranoside (Ib, R = NO2) (Example 4) was used as starting material and processed according to Example 7,250 mg (71%) of the title compound was obtained. Mp.: 207-210 °C, Rf (B) = 0.2, [a] D = +78° (c =

0.5, pyridine). NMR (DMSO-d6), 1H: 4.41 (H-1), 4.05 (H-2), 3.64 (H-3), 3.98 (H-4), 2.80 (H-5a), 2.22 (H-5b), 2.04 (NAc), 5.39,4.96 and 4.78 (OH), 10.02 (NH), 7.56-7.38 ppm (aromatic H) ; J1 2 2.0, J2, 3 5.1, J3,4 2. 3, J4,5a 10. 5, J4, 5b 3 4, J5a, 5b 12 5 Hz.

Example 9 4-Cyanophenyl l, 5-dithio-a-D-arabinopyranoside (Ic, R = CN) When the corresponding D-enantiomer was used as starting material and processed according to Example 1,0.5 g (64%) of the title compound of formula (Ic) was obtained.

Mp.: 219-221 °C, Rf (B) = 0.3, [α]D = +106° (c = 0.5, pyridine).

Example 10 4-Cyanophenyl 1, 5-dithio-ßD-arabinopyranoside (Id, R = CN) When the corresponding D-enantiomer was used as starting material and processed according to Example g (67%) of the title compound of formula (Id) was obtained.

Mp.: 181-183 °C, Rf (B) = 0.3, [a] D =-161° (c = 0.5, pyridine).

Example I I 4-Nitrophenyl 1, 5-dithio-a-D-arabinopyranoside (Ic, R = N02) When the corresponding D-enantiomer was used as starting material and processed according to Example 3,260 mg (79%) of the title compound was obtained. Mp.: 175-177 °C, Rf(A) = 0. 2, [a] D = +106° (c = 0.5, pyridine).

Example 12

4-Nitrophenyl 1,5-dithio-b-D-arabinopyranoside (Id, R = N02) When the corresponding D-enantiomer was used as starting material and processed according to Example 4, 200 mg (83%) of the title compound was obtained. Mp.: 180-183 °C, Rf (A) = 0.2, [a] D =-165° (c = 0.5, pyridine).

Example 13 4- (Aminothiocarbonyl) phenyl 1, 5-dithio-a-D-arabinopyranoside (Ic, R = CS (NHJ) A solution of 420 mg of 4-cyanophenyl 1,5-dithio-a-D-arabinopyranoside (Example 9) in 10 ml of pyridine and 10 ml of triethylamine was saturated with a slow stream of hydrogen sulfide for 5 h. The mixture was kept at room tamperature overnight and was then concentrated. The residue was recrystallized from methanol to yield 410 mg (87%) of the title comound. Mp.: 205-209 °C, Rf (B) = 0.2, [a] D = +68° (c = 0.5, pyridine). NMR (DMSO- d6), 1H: 4.31 (H-1), 3.86 (H-2), 3.41 (H-3), 4.00 (H-4), 2.72-2.62 (H-5a, 5b), 5.37,4.87 and 4.76 (OH), 9.85 and 9.40 (NH2), 7.85-7.30 ppm (aromatic H) ; J1 2 7. 2, J2 3 7. J3,4 2.4, J4,5a"2.5, J4, 5b 5. 3, J5a, 5b 13.2 Hz.

Example 14 4-(Aminothiocarbonyl) phenyl I, 5-dithio-b-D-arabinopyranoside (Id, R = CS (a2)) When the corresponding D-enantiomer was used as starting material and processed according to Example 5,0.89 g (92%) of the title compound was obtained. Mp.: 214-218 °C, Rf (B) = 0.2, [a] D =-110° (c = 0.5, pyridine).

Example 15 4-Acetamidophenyl I, 5-dithio-a-D-arabinopyranoside (Ic, R = NHAc)

When the corresponding D-enantiomer was used as starting material and processed according to Example 7,210 mg (61%) of the title compound was obtained. Mp.: 195-198 °C, Rf(B) = 0. 2, [a] D = +31 ° (c = 0.5, pyridine).

Example 16 4-Acetamidophenyl 1, 5-dithio-b-D-arabinopyranoside (Ic, R = NHAc) When the corresponding D-enantiomer was used as starting material and processed according to Example 8,182 mg (51%) of the title compound was obtained. Mp.: 209-212 °C, Rf (B) = 0.2, [a] D =-83° (c = 0.5, pyridine).