Substituted, nucleoside derivatives, methods for their preparation and pharmaceutical compositions containing them

Abstract: The invention relates to substituted nucleoside derivatives, their chemical synthesis and antivirally active pharmaceutical compositions containing said derivatives. It has been found that this novel class of substituted derivatives displays a selective inhibiting effect on HIV-1. The most preferred compounds are {1-[2', 5'-bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-methyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'', 2-dioxide) and {1-[2', 5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-ethyl-thymine}-3'-spiro-5''-{4''-amino-1'', 2''-oxathiole-2'', 2''-dioxide}.

Description: The present invention relates to substituted nucleoside derivates, as well as to their chemical synthesis and to antivirally active pharmaceutical compositions containing said compounds. The most potent and selective anti-HIV (Human Immunodeficiency Virus) agents, which seem to act through inhibition of reverse transcriptase, are the 2',3'-dideoxynucleosides. 3'-Azido-3'-deoxythymidine (AZT) has been, so far, the only approved drug for treatment of AIDS in humans. It is now well established that AZT prolongs the life of ARC and AIDS patients, decreases the frequency as well as severity of opportunistic infections, and partially restores the immunological competence of the patients. However, long-term treatment of AIDS patients with AZT is compounded by a number of toxic side effects, the main drawback being bone marrow suppression. Shortly after the discovery of AZT as an effective anti-retrovirus agent, various other 2',3'-dideoxynucleoside (ddN) analogues were identified as potent and selective HIV inhibitors, and some of these ddN analogues are now subject of clinical trials. Recently, different classes of compounds have been established to inhibit HIV-1, but not HIV-2 or SIV replication. These highly specific HIV-1 inhibitors include the 6-substituted acyclouridine derivatives, dipyridodiazepinones and pyridinones. After extensive research it has now been found that a selective inhibiting effect on HIV-1 is displayed by a novel class of substituted nucleoside derivatives according to claim 1. The prior art document EP-A-0 382 526 discloses substituted-1,3-oxathiolanes with antiviral properties. In these compounds a sulphoxide moiety is incorporated into the ring at the 3'-position. Contrary to the compounds of the invention however they do not possess a 3'-spiro-substituent or 2',5'-derivatization. The 50% effective concentration (EC₅₀) of the most active of these compounds for HIV-1 ranged from 0.034 to 0.439 µg/ml. The 50% cytotoxic concentration (CC₅₀) for MT-4 cells ranged from 2.35->200 µg/ml. Structure-activity studies revealed that the simultaneous presence of a 3'-spiro-substituent and alkylated silyl groups at the 2' an 5' positions of the ribose results in compounds which are exquisitely inhibitory. Preferred compounds comprise derivatives of formula I of claim 1 wherein B is a N³-alkylated thymine, the 3'-position of the ribose is substitued with a spiro -substituent and the 2'-and 5'-positions are both substituted with silyl substituents optionally substituted with alkyl or phenyl. The most preferred compounds are {[1-2',5'-bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-methyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2-dioxide} with EC₅₀ = 0,034 µg/ml, CC₅₀ = 139 µg/ml and Selectivity Index = 4088; or {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-ethyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide} with EC₅₀ = 0,073 µg/ml, CC₅₀ = 73 µg/ml and Selectivity Index = 1000. The substituted nucleoside derivatives are preferably synthesized by: starting with a 3'-keto nucleoside of the formula: wherein B represents a pyrimidine, purine, benzimidazole, imidazole, triazole, all of which may optionally be substituted, and silyl can optionally be substituted with alkyl, phenyl or other lipophilic moiety; replacing the 3'-keto group therein by cyanohydrin; converting said cyanohydrin to cyanomesylate; converting said cyanomesylate to a spiro group; and optionally removing one or more protecting silyl groups. Alternatively, the nucleoside derivatives of formula I can be synthesized by: using as a starting material a compound of formula: converting the 3'-keto group therein through a cyanohydrin group to a cyanomesylate group; converting the isopropylidene dioxy group in the 1,2-positions to two acetyloxy groups; replacing the acetyloxy group in the 1-position by a residue of a pyrimidine or purinebase; converting the cyanomesylate group in the 3'-position to a spiro -group; silylating one or both hydroxyl groups in the 2' and 5' position; and optionally deprotecting one of said silylated hydroxy groups. The invented compounds as well as their chemical synthesis and preparation of the starting materials are illustrated in the following examples, which should not be constructed however, to restrict the invention. SYNTHESIS EXAMPLE 1 Intermediate Compounds A and B 2',5'-Bis- O -( tert -butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-pentofuranosyl nucleosides. A mixture of a 3'-ketonucleoside (4 mmol), water (16 mL), ethyl ether (32 mL), sodium bicarbonate (0.64 g, 8 mmol) and sodium cyanide (0.2 g, 4 mmol) was stirred vigorously at room temperature for 16 h. The organic phase was separated, and the aqueous phase was washed with ethyl ether (2x50 mL). The combined ethereal phases were dried over anhydrous sodium sulfate, filtered, and evaporated to dryness. The residue, a mixture of the two epimeric cyanohydrins, was dissolved in dry pyridine (8 mL). To this solution mesyl chloride (1.6 mL, 20 mmol) was added. The mixture was stirred at 8-10°C for 48 h, poured into ice and water, and extracted with chloroform (2 x 50 mL). The combined extracts were washed with 1N-HCl (50 mL) aqueous sodium hydrogencarbonate (50 mL), and brine (50 mL), dried over anhydrous sodium sulfate, filtered and evporated to dryness. The residue was purified by column chromatography. Compounds A-1 and B-1 1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-xylofuranosyl]thymine and 1-[2',5'-Bis- O -(tert-butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-ribofuranosyl]thymine. The residue was chromatographed with ethyl acetate/hexane (1:4) as the eluent. The fastest moving bands afforded 1.18 g (53%) of A-1 a as a white foam: IR (KBr) 1375, 1185 cm⁻¹ (SO₂); ¹H NMR (CDCl₃, 90 MHz) δ 1.96 (s, 3H, CH₃-5), 3.33 (s, 3H, CH₃SO₂), 4.05 (m, 2H, H-5'), 4.51 (m, 1H, H-4'), 4.87 (d, 1H, H-2', J 1',2' =2 Hz), 6.03 (d, 1H, H-1'), 7.28 (s, 1H, H-6), 9.12 (bs, 1H, NH-3); ¹³C NMR (CDCl₃, 20 MHz) δ 12.26 (CH₃-5), 40.24 (CH₃SO₂), 59.17 (C-5'), 81.51, 83.55 (C-2', C-4'), 82.51 (C-3'), 91.57 (C-1'), 111.87, 112.63 (CN, C-5), 134.68 (C-6), 150.22 (C-2), 163.55 (C-4). Anal. (C₂₄H₄₃N₃O₈SSi₂). C, H, N, S. The slowest moving bands afforded 0.22 g (10%) of B-1 as a white foam: IR (KBr) 1375, 1180 cm⁻¹ (SO₂); ¹H NMR (CDCl₃, 300 MHz) δ 1.94 (s, 3H, CH₃-5), 3.26 (s, 3H, CH₃SO₂), 4.04 (m, 2H, H-5', J 5'a,5'a =12, J 4',5'b =1.2, J 4',5'b =2.1 Hz), 4.51 (d, 1H, H-2', J 1',3' = 8.3 Hz), 4.73 (m, 1H, H-4'), 6.24 (d, 1H, H-1'), 7.38 (s, 1H, H-6), 8.48 (bs, 1H, NH-3); ¹³C NMR (CDCl₃, 20 MHz) δ 12.05 (CH₃-5), 40.33 (CH₃SO₂), 62.09 (C-5'), 80.34 (C-3'), 78.20, 84.10, 84.28 (C-2', C-4', C-1'), 112.24, 114.19 (C-5, CN), 133.68 (C-6), 150.42 (C-2), 163.18 (C-4). Anal. (C₂₄H₄₃N₃O₈SSi₂). C, H, N, S. Compounds A-2 and B-2 1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-xylofuranosyl]uracil and 1-[2',5'-Bis- O -(tert-butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-ribofuranosyl]uracil. The residue was chromatographed with ethyl acetate/hexane (1:4) as the eluent. The fastest moving bands afforded 0.26 g (11%) of B-2 as a white foam: IR (KBr) 1375, 1180 cm⁻¹ (SO₂); ¹H NMR (CDCl₃, 90 MHz) δ 3.23 (s, 3H, CH₃SO₂), 4.03 (m, 2H, H-5'), 4.56 (d, 1H, H-2', J 1',2' =7.5 Hz), 4.73 (m, 1H, H-4'), 5.76 (dd, 1H, H-5), 6.26 (d, 1H, H-1'), 7.80 (d, 1H, H-6), 8.96 (bs, 1H, NH-3); ¹³C NMR (CDCl₃, 20 MHz) δ 40.33 (CH₃SO₂), 62.46 (C-5'), 78.76, 80.50, 84.33, 84.93 (C-2', C-3', C-4', C-1'), 103.59 (C-5), 114.00 (CN), 138.73 (C-6), 150.27 (C-2), 162.55 (C-4). Anal. (C₂₃H₄₁N₃O₈SSi₂). C, H, N, S. From the slowest moving bands A-2 (1.25 g, 52%) was isolated as a white foam: IR (KBr) 1375, 1185 cm⁻¹ (SO₂); ¹H NMR (CDCl₃ , 90 MHz) δ 3.20 (s, 3H, CH₃SO₂), 4.03 (m, 2H, H-5'), 4.60 (m, 1H, H-4'), 4.93 (d, 1H, H-2', J 1',2' =1.5 Hz), 5.73 (d, 1H, H-5), 5.86 (d, 1H, H-1'), 7.46 (d, 1H, H-6), 9.73 (bs, 1H, NH-3); ¹³C NMR (CDCl₃, 20 MHz) δ 40.01 (CH₃SO₂), 61.88 (C-5'), 77.71, 80.06, 82.51, 86.42 (C-2', C-3', C-4', C-1'), 105.10 (C-5) 114.33 (CN), 139.10 (C-6), 149.69 (C-2), 163.00 (C-4). Anal. (C₂₃H₄₁N₃O₈SSi₂). C, H, N, S. Compounds A-3 and B-3 4- N -Acetyl-1-[2',5'-bis- O -( tert -butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-xylofuranosyl]cytosine and 4- N -acetyl-1-[2',5'-bis- O -( tert -butyldimethylsilyl)-3'- C -cyano-3'- O -mesyl-β-D-ribofuranosyl]cytosine. The residue was chromatographed with ethyl acetate/hexane (1:1) as the eluent. The fastest moving fractions afforded 1.3 g (53%) of A-3 as a white foam: IR (KBr) 1375, 1185 cm⁻¹ (SO₂); ¹H NMR (CDCl₃, 90 MHz) δ 2.28 (s, 3H, NAc), 3.17 (s, 3H, CH₃SO₂), 4.10 (m, 2H, H-5'), 4.76 (m, 1H, H-4'), 5.17 (d, 1H, H-2', J 1',2' =1.2 Hz), 5.84 (d, 1H, H-1'), 7.50 (d, 1H, H-5), 7.82 (d, 1H, H-6), 10.6 (bs, 1H, NH-4); ¹³C NMR (CDCl₃, 20 MHz) δ 40.06 (CH₃SO₂), 59.11 (C-5'), 80.51 (C-3'), 81.57, 85.30 (C-2', C-4'), 93.29 (C-1'), 96.75 (C-5), 112.78 (CN), 143.20 (C-6), 154.87 (C-2), 163.67 (C-4), 171.45 (4-NCO). Anal. (C₂₅H₄₄N₄O₈SSi₂). C, H, N, S. The slowest moving fractions gave 0.37 g (15%) of B-3 as a white foam: IR (KBr) 1375, 1180 (SO₂); ¹H NMR (CDCl₃, 90 MHz) δ 2.30 (s, 3H, NAc), 3.24 (s, 3H, CH₃SO₂), 4.04 (m, 2H, H-5'), 4.62 (d, 1H, H-2', J 1',2' =8 Hz), 4.74 (m, 1H, H-4'), 6.42 (d, 1H, H-1'), 7.45 (d, 1H, H-5), 8.23 (d, 1H, H-6), 10.28 (bs, 1H, NH-4); ¹³C NMR (CDCl₃, 50 MHz) δ 40.36 (CH₃SO₂), 62.30 (C-5'), 80.70 (C-3'), 80.07, 84.46, 85.86 (C-1', C-2', C-4'), 97.81 (C-5), 114.10 (CN), 143.60 (C-6), 154.96 (C-2), 163.23 (C-4), 171.37 (4-NCO). Anal. (C₂₅H₄₄N₄O₈SSi₂). C, H, N, S. SYNTHESIS EXAMPLE 2 General Procedure for the Synthesis of Compounds 5, 11 and 15 The {1-[2',5'-Bis- O ( tert -butyldimethylsilyl)-β-D-pentofuranosyl]nucleosides}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide} were prepared as follows. To a solution of the intermediate compounds 3'- C -cyano-3'-O-mesyl pentofuranosylnucleoside A or B (1 mmol) in dry acetonitrile (10 mL), either Cs₂Co₃ (325 mg, 1 mmol) or DBU (0.14 mL, 1 mmol) was added. The mixture was stirred at room temperature for 1-24 h, then filtered and evaporated to dryness. The residue was purified by column chromatography. Compound 5 {1-[2',5'-Bis- O -(tert-butyldimethylsilyl)-β-D-ribofuranosyl]thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. According to the general procedure, intermediate compound B-1 was treated with Cs₂Co₃ for 24 h. The residue was chromatographed with ethyl acetate/hexane (1:3) to give 0.11 g (85%) of compound 5 as an amorphous solid. IR (KBr) 3400, 3320 cm⁻¹ (NH₂), 1645 (C=C-N); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 1.90 (s, 3H, CH₃-5), 4.06 (m, 2H, H-5', J 5'a,5'b =12.2 Hz), 4.31 (t, 1H, H-4', J 4',5' =3.6 Hz), 4.67 (d, 1H, H-2', J 1',2' =8.0 Hz), 5.75 (s, 1H, H-3''), 6.00 (d, 1H, H-1'), 6.47 (bs, 2H, NH₂), 7.42 (s, 1H, H-6), 10.32 (bs, 1H, NH-3); ¹³C NMR [(CD₃)₂CO, 50 MHz] δ 63.05 (C-5'), 72.12, 85.05 87.62 (C-2', C-4', C-3''), 92.25, 92.31 (C-1', C-3'), 112.20 (C-5), 136.22 (C-6), 151.60, 152.28 (C-2, C-4''), 163.72 (C-4). Anal. (C₂₄H₄₃N₃O₈SSi₂). C, H, N. Compound 11 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β-D-ribofuranosyl] uracil }-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. According to the general procedure, intermediate compound B-2 was treated with Cs₂Co₃ for 24 h. The residue was chromatographed with ethyl acetate/hexane (1:2) as the eluent to give 0.24 g (39%) of compound 11 as an amorphous solid. IR (KBr) 3390, 3310, 3190 cm⁻¹ (NH₂, NH), 1645 (C=C-N); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 4.08 (m, 2H, H-5', J 4',5'a =3.2, J 4',5'b =2.9, J 5'a,5'b =12.4 Hz), 4.35 (dd, 1H, H-4'), 4.59 (d, 1H, H-2', J 1',2' =8.1 Hz), 5.79 (s, 1H, H-3''), 5.83 (d, 1H, H-5), 6.08 (d, 1H, H-1'), 6.44 (bs, 2H, NH₂), 7.76 (d, 1H, H-6), 10.30 (bs, 1H, NH-3); ¹³C NMR [(CD₃)₂SO, 75 MHz] δ 60.20 (C-5'), 74.50 (C-2'), 84.38, 84.58 (C-4', C-3''), 89.50 (C-1'), 92.81 (C-3'), 103.23 (C-5), 139.91 (C-6), 150.92 151.32 (C-2, C-4''), 162.73 (C-4). Anal. (C₂₃H₄₁N₃O₈SSi₂). C, H, N. Compound 15 {4- N -Acetyl-1-[2',5'-bis- O -( tert -butyldimethylsilyl)-β-D-ribofuranosyl]cytosine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. Intermediate compound B-3 was treated with Cs₂CO₃ according to the general procedure for 1 h. The residue was chromatographed with chloroform/methanol (50:1) as the eluent to give 0.14 g (70%) of compound 15 as an amorphous solid. IR (KBr) 3410, 3320 cm⁻¹ (NH₂), 1650 (C=C-N); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 2.24 (s, 3H, NAc), 4.07 (m, 2H, H-5'), 4.29 (dd, 1H, H-4', J 4',5'a =3.09, J 4',5'b =4.66 Hz), 4.83 (d, 1H, H-2', J 1',2' =7,33 Hz), 5.71 (s, 1H, H-3''), 5.97 (d, 1H, H-1'), 6.61 (bs, 2H, NH₂), 7.46 (d, 1H, H-5), 8.17 (d, 1H, H-6), 9.86 (bs, 1H, NH-4); ¹³C NMR [(CD₃)₂CO, 50 MHz] δ 62.97 (C-5'), 75.94, 85.25 (C-2', C-4'), 91.12, 91.34, 91.50 (C-3', C-3'', C-1'), 97.66 (C-5), 147.13 (C-6), 152.80, 155.80 (C-2', C-4''), 164.08 (C-4), 171.64 (4-NCO). Anal. (C₂₅H₄₄N₄O₈SSi₂). C, H, N. SYNTHESIS EXAMPLE 3 General Procedure for the synthesis of Intermediate compounds C, D and E Compounds 5 and 11 can alternatively be obtained as follows. A benzoyl-isopropylidene nucleoside was treated with sodium cyanide in a two-phase ethyl ether/water system, in the presence of NaHCO₃, to obtain a ribo cyanohydrin, which was immediately transformed in a cyanomesylate. Hydrolysis of the 1,2-O-isopropylidene group with aqueous trifluoroacetic acid, followed by reaction with acetic anhydride/pyridine afforded a diacetate derivative. These were glycosylated with thymine, uracil and 5-ethyluracil to obtain intermediate compounds C-1, C-2, C-3 respectively. Treatment of these intermediate compounds with Cs₂CO₃ gave intermediate compounds D-1, D-2 and D-3. Deprotection thereof with saturated methanolic ammonia gave fully deprotected intermediate compounds E-1, E-2 and E-3 which with reaction with tert -butyldimethylsilyl chloride furnished compounds 5, 11 and 10 respectively. Compound 5 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β-D-ribofuranosyl]thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. To a suspension of E-1 (0.20 g, 0.55 mmol) in dry acetonitrile (15 mL), 4-dimethylaminopyridine (0.34 g, 2.76 mmol) and tert-butyldimethylsilyl chloride (0.414 g, 2.76 mmol), was stirred at room temperature for 24 h. The solvent was evaporated to dryness and the residue, dissolved in ethyl acetate (50 mL), was washed with cold (4°C) 1N HCl (25 mL), water (50 mL) and brine (50 mL). The organic phase was dried over anhdrous Na₂SO₄, filtered and evaporated to dryness. The residue was chromatographed with chloroform/acetone (8:1) as the eluent to give 5 (0.24 g, 74%) as an amorphous solid. Compound 11 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]uracil}-3' - spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. To a solution of the cyanomesylate C-2 (0.98 g, 2.0 mmol) in dry acetonitrile (15 mL), Cs₂CO₃ (0.65 g, 20 mmol) was added. The mixture was stirred at room temperature for 6 h, then filtered, the filtrate was neutralized with acetic acid, and finally, evaporated to dryness. The residue (The spiro derivative D2) was deprotected with saturated methanolic ammonia (20 mL). After standing at room temperature overnight, the solvent was evaporated to dryness. The residue was dissolved in methanol (2 mL) and then treated with chloroform. The solid (the deprotected nucleoside E2) was filtered and suspended in dry acetonitrile (15 mL) and then, 4-dimethylaminopyridine (0.53 g, 4.4 mmol) and tert -butyldimethylsilyl chloride (0.66 g, 4.4 mmol) were added, stirred at room temperature for 48 h, and evaporated to dryness. The residue was treated with ethyl acetate (100 mL) and water (50 mL). The organic phase was separated, and the aqueous phase was extracted with ethyl acetate (2 x 50 mL). The combined organics were succesively washed with cold (4°C) 1N HCl (25 mL), water (50 mL) and brine (50 mL) and, finally, dried over anhydrous Na₂SO₄, filtered and evaporated to dryness. The residue was chromatographed with chloroform/acetone (8:1) as the eluent to give 11 (0.28 g, 24%) as an amorphous solid. Compound 10 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-5-ethyl-uracil}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. A solution of cyanomesylate C3 (1.0 g, 1.91 mmol) in dry acetonitrile (16 mL) was treated with CsCO₃ (0.62 g, 1.91 mmol) for 4 h at room temperature. A similar treatment to that described for the synthesis of compound 5 afforded a residue that was chromatographed with chloroform/acetone (10:1) to give 0.37 g (32%) of compound 10 as an amorphous solid. IR (KBr) 3500, 3420 cm⁻¹ (NH₂), 1650 (C=C-N); ¹H NMR [(CD₃)₂SO, 200 MHz] δ 1.05 (t, 3H, C H ₃CH₂-5), 2.26 (m, 2H, CH₃C H ₂), 3.87 (m, 2H, H-5', J 5'a,5'b = 11.4, J 4',5'a = 4.8, J 4',5'b = 7.5 Hz), 4.19 (dd, 1H, H-4'), 4.52 (d, 1H, H-2', J 1',2' = 8.4 Hz), 5.73 (s, 1H, H-3''), 5.89 (d, 1H, H-1'), 6.93 (bs, 2H, NH₂), 7.56 (s, 1H, H-6), 11.55 (bs, 1H, NH-3); ¹³ C NMR [(CD₃)₂CO, 50 MHz] δ 14.17 ( C H₃CH₂), 21.20 (CH₃ C H₂), 62.99 (C-5'), 74.99 (C-2'), 85.07, 88.66 (C-4', C-3''), 91.85 (C-3'), 91.98 (C-1'), 118.20 (C-5), 136.56 (C-6), 151.55, 152.28 (C-2, C-4''), 163.23 (C-4). Anal. (C₂₅H₄₅N₃O₈SSi₂) C, H, N SYNTHESIS EXAMPLE 4 Synthesis of compounds 16 and 14 Compounds 5 and 11 were reacted further so as to obtain compounds 16 and 14, respectively. Compound 16 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-5-methyl-cytosine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. To a solution of compound 5 (0.15 g, 0.25 mmol) in dry pyridine (2 mL), a solution of 1,2,4-triazole (0.069 g, 1.01 mmol) and POCl₃ (0.05 mL, 0.5 mmol) in dry pyridine (5 mL) was added. The resulting solution was stirred at room temperature for 4 h, then chilled on ice, and aqueous ammonia (2 mL) was added. After stirring at room temperature for 30 min, the solvent was evaporated to dryness. The residue was treated with 20 mL of a (1:1) mixture of chloroform: methanol. The solid was filtered and the filtrate, after evaporating to dryness, was purified by column chromatography with chloroform/acetone (1:1) as the eluent to give compound 16 (0.10 g, 67%) as an amorphous solid: IR (KBr) 3350, 3190 cm⁻¹ (NH₂), 1650 (C=C-N); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 2.05 (s, 3H, CH₃-5), 4.02 (dd, 1H, H-5'a, J 5'a,5'b = 11.7, J 4',5'a = 6.8 Hz), 4.09 (dd, 1H, H-5'b, J 4',5'b =2.5 Hz), 4.14 (dd, 1H, H-4'), 5.09 (d, 1H, H-2', J 1',2' = 6.6 Hz), 5.51 (d, 1H, H-1'), 5.60 (s, 1H, H-3''), 6.92 (bs, 2H, NH₂-4''), 7.64 (s, 1H, H-6), 8.22 (bs, 2H, NH₂-4); ¹³ C NMR [(CD₃)₂CO, 50 MHz]δ 13.19 (CH₃-5), 62.64 (C-5'), 74.38 (C-2'), 84.57, 88.98, 95.19 (C-4', C-3'', C-1'), 89.58 (C-3'), 104.06 (C-5), 138.42 (C-6), 154.63, 156.63 (C-2, C-4''), 167.10 (C-4). Anal. (C₂₄H₄₄N₄O₇SSi₂) C, H, N. Compound 14 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]- cytosine }-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. Compound 11 (0.18 g, 0.031 mmol) was reacted with 1,2,4-triazole (0.085 g, 1.24 mmol) and POCl₃(0.06 mL, 0.62 mmol) for 4 h, and then treated with aqueous ammonia, following a similar procedure to that described for the synthesis of compound 16. The residue was chromatographed with chloroform/ethyl acetate (1:2) to yield 0.15 g (84%) of 14 as an amorphous solid; IR (KBr) 3410, 3350, 3200 cm⁻¹ (NH₂), 1650 (C=C-N); ¹H NMR [(CD₃)₂SO, 300 MHz] δ 3.87 (m, 2H, H-5', J 4',5' = 5.3 Hz), 4.15 (t, 1H, H-4'), 4.60 (d, 1H, H-2', J 1',2' =7.8 Hz), 5.73 (s, 1H, H-3''), 5.87 (d, 1H, H-5), 5.90 (d, 1H, H-1'), 6.96 (bs, 2H, NH₂-4''), 7.42 (bs, 2H, NH₂-4), 7.74 (d, 1H, H-6).Anal (c₂₃H₄₂N₄O₇SSi₂) C, H, N. SYNTHESIS EXAMPLE 5 General Procedure for the Synthesis of Compounds 6, 7, 8, 9 and 13. (3- N -Alkyl-Nucleosides)-3'-spiro-5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide). To a solution of the spironucleoside 5 or 11 (1 mmol) in acetone (12 mL), K₂CO₃ (0.5 mmol) and the corresponding alkyl halide (1.1-2.0 mmol), were added. The reaction mixture was refluxed for 3-8 h. After removal of the solvent, the residue was purified by column chromatography. Other reaction parameters were as follows. Compound 6 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-methyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide} Compound 5 (0.15 g, 0.25 mmol) and methyl iodide (0.07 mL, 0.5 mmol) reacted according to the general procedure for 4h. The residue was chromatographed with hexane/ethyl acetate (3:1) to give 6 (0.083 g, 55%) as white foam; IR (KBr) 3390 cm⁻¹ (NH₂), 1715, 1675 (C=O), 1645 (C=C-N)); ¹H NMR [(CD₃)₂CO, 200 MHz] δ 1.95 (s, 3H, CH₃-5),3.26 (s, 3H, N-CH₃), 4.09 (m, 2H, H-5', J gem = 12.2 , J 4',5' = 3.5 Hz), 4.34 (t, 1H, H-4'), 4.66 (d, 1H, H-2', J 1',2' = 8.1 Hz), 5.76 (s, 1H, H-3''), 6.08 (d, 1H, H-1'), 6.45 (bs, 2H, NH₂), 7.50 (s, 1H, H-6). 13C NMR[(CD₃)₂ CO, 50MHz] 13.10 (CH₃-5, CH₃N), 63.14(C-5'), 75.43 (C-2'), 85.18, 88.27 (C-4', C-3''), 92.47 (C-1', C-3'), 111.33 (C-5), 134.47 (C-6), 152.17, 152.24 (C-2, C-4''), 163.37 (C-4). Anal. (C₂₅H₄₅N₃O₈SSi₂) C, H, N. Compound 7 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-ethyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide} Compound 5 (0.15 g, 0.25 mmol) and ethyl iodide (0.077 mL, 0.5 mmol) reacted, according to the general procedure, for 8h. The residue was chromatographed with hexane/ethyl acetate (3:1) to yield 0.12 g (77%) of 7 as an amorphous solid; IR (KBr)3400, 3320 cm⁻¹ (NH₂), 1715, 1670 (C=O) , 1645 (C=C-N)); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 1.15 (t, 3H, N-CH₂C H ₃, J=7.05 Hz), 1.94 (s, 3H, CH₃-5), 3.95 (q, 2H, N-C H ₂CH₃), 4.11 (m, 2H, H-5', J gem = 12.2 , J 4',5'a = 3.6, J 4',5'b = 3.5 Hz), ), 4.34 dd, 1H, H-4'), 4.66 (d, 1H, H-2', J 1',2' = 8.15 Hz), 5.77 (s, 1H, H-3''), 6.10 (d, 1H, H-1'), 6.48 (bs, 2H, NH₂), 7.49 (s, 1H, H-6); ¹³ C NMR [(CD₃)₂CO, 50 MHz]δ 13.00 (CH₃-5, C H₃CH₂N), 36.98 (CH₃ C H₂N), 63.14 (C-5'), 75.32 (C-2'), 85.14 (C-4'), 88.00 (C-3''), 92.52 ( C-1', C-3'), 111.56 (C-5), 134.56 (C-6), 151.89, 152.20 (C-2, C-4''), 162.98 (C-4). Anal. (C₂₆H₄₇N₃O₈SSi₂) C, H, N. Compound 8 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-allyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. Compound 5 (0.15 g, 0.25 mmol) was reacted with allyl bromide (0.023 mL, 0.27 mmol), according to the general procedure, for 3 h. The residue was chromatographed with chloroform/acetone (10:1) to afford 8 (0.10 g, 65%) as an amorphous solid; IR (KBr) 3400, 3320 cm⁻¹ (NH₂), 1710, 1670 (C=O) , 1645 (C=C-N)); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 1.96 (s, 3H, CH₃-5), 4.10 (m, 2H, H-5', J gem = 12.2 , J 4',5'a = 3.73, J 4',5'b = 3.56 Hz), 4.35 ( dd, 1H, H-4'), 4.52 (d, 2H, N-CH₂-), 4.70 (d, 1H, H-2', J 1',2' = 8.14 Hz), 5.12-5.25 (m, 2H, C H ₂=CH), 5.78 (s, 1H, H-3''), 5.86 (m, 1H, CH₂=C H ), 6.10 (d, 1H, H-1'), 6.49 (bs, 2H, NH₂), 7.54 (s, 1H, H-6); ¹³ C NMR [(CD₃)₂CO, 50 MHz] δ 13.07 (CH₃-5), 43.88 (N-CH₂), 63.14 (C-5'), 75.25 (C-2'), 85.17, 88.21 (C-4',C-3''), 92.50 ( C-1', C-3'), 111.52 (C-5), 118.04 ( C H₂=CH), 132.98 (CH₂= C H), 134.83 (C-6), 151.78, 152.22 (C-2, C-4''), 162.87 (C-4). Anal. (C₂₇H₄₇N₃O₈SSi₂) C, H, N. Compound 9 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-(3-methyl-2-butenyl)-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. According to the general procedure, compound 5 (0.15 g, 0.25 mmol) and 4-bromo-2-methyl-2-butene (0.93 mL, 1.0 mmol) reacted for 2.5 h. The residue was chromatographed with chloroform/acetone (15:1) to give 9 (0.115 g, 70%) as a white solid. mp 194-195°C (chloroform/hexane); IR (KBr) 3400, 3320 cm⁻¹ (NH₂), 1710, 1675 (C=O) , 1645 (C=C-N)); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 1.67, 1.79 [2s, 6H, (CH₃)₂C=C], 1.94 (s, 3H, CH₃-5), 4.08 (m, 2H, H-5', J gem = 12.21, J 4',5'a = 3.56, J 4',5'b = 3.51 Hz), 4.34 (dd, 1H, H-4'), 4.50 (d, 2H, N-CH₂), 4.66 (d, 1H, H-2', J 1',2' = 8.06 Hz), 5.20 (m, 1H, C=C H -CH₂), 5.77 (s, 1H, H-3''), 6.10 (d, 1H, H-1'), 6.48 (bs, 2H, NH₂), 7.49 (s, 1H, H-6); ¹³ C NMR [(CD₃)₂CO, 50 MHz]δ 39.90 (N-CH₂), 63.14 (C-5'), 75.34 (C-2'), 85.14, 88.07 (C-4',C-3''), 92.54 (C-1', C-3'), 111.55 (C-5),119.06 (C= C H), 134.60 (C-6), 137.16 [(CH₃)₂ C =CH], 151.84, 152.21 (C-2, C-4''), 162.98 (C-4). Anal. (C₂₉H₅₁N₃O₈SSi₂) C, H, N. Compound 13 {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3- N -allyl-uracil}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. According to the general procedure, compound 11 (0.15 g, 0.26 mmol) reacted with allyl bromide (0.09 mL, 1.04 mmol), for 6 h. The residue was chromatographed with chloroform/acetone (15:1) to give compound 13 (0.143 g, 89%) as an amorphous solid; IR (KBr) 3400, 3330 cm⁻¹ (NH₂), 1720, 1675 (C=O) , 1645 (C=C-N)); ¹H NMR [(CD₃)₂CO, 300 MHz] δ 4.07 (m, 2H, H-5', J gem = 12.45 Hz), 4.37 ( dd, 1H, H-4', J 4,5a = 2.7, J 4',5'b = 3.2 Hz), 4.48 (m, 2H, N-CH₂), 4.59 (d, 1H, H-2', J 1',2' = 8.06 Hz), 5.16 (m, 2H, C H ₂=CH), 5.80 (s, 1H, H-3''), 5.83 (m, 1H, CH₂=C H ), 5.94 (d, 1H, H-5), 6.15(d, 1H, H-1'), 6.45 (bs, 2H, NH₂), 7.79 (s, 1H, H-6). Anal. (C₂₆H₄₅N₃O₈SSi₂) C, H, N. Pharmaceutical compositions comprising compounds of formula I as an active ingredient for treatment of AIDS and/or AIDS-related diseases in humans and animals, might take the form of suspensions, powders, solutions, sprays, emulsions, unguents or creams and can be used for topical administration, intranasal, rectal, vaginal as well as oral or parenteral (intravenous, intradermal, intramuscular, intrathecal etc.) administration. Such compositions can be prepared by combining (e.g. by mixing, dissolving etc.) of the active ingredient of formula I in the form of a free acid or salt with pharmaceutical excipients of a neutral character (such as aqueous or non-aqueous solvents, stabilizers, emulsifiers, detergents, additives) and further if necessary, with dyes and aromatizers. The concentration of the active ingredients in a pharmaceutical composition may vary widely between 0.1% to 100%, depending on the nature of treatment and mode of administration. Further, the dose of the active ingredients to be administered may vary between 0.1 mg to 100 mg per kg bodyweight. The anti-HIV properties of the 2',3',5'-substituted nucleoside derivates according to the invention are documented by the following examples which should not be read in a restricted sense. The viruses used were moloney murine sarcoma virus (MSV), HIV-1 (strain HTLV-III B , kindly provided by R.C. Gallo and M. Popovic, National Cancer Institute, Bethesda, MD), HIV-2 (strain LAV-2(ROD)), kindly provided by L. Montagnier (Pasteur Institute, Paris, France), simian immunodeficiency virus (SIV) (strain SIV MAC251 , kindly provided by C. Bruck, RIT-Smith-Kline, Rixensart, Belgium). The radiolabelled nucleosides [ methyl -³H]dThd (specific radioactivity: 40 Ci/mmol), [5-³H]dUrd (specific radioactivity: 27 Ci/mmol), [5-³H]dCyd (specific radioactivity: 18.2 Ci/mmol) and the radiolabelled amino acid L-[4,5-³H]leucine (specific radioactivity: 52 Ci/mmol were derived from the Radiochemical Centre (Amersham, England); [5-³H]Urd (specific radioactivity: 21 Ci/mmol) and [5-³H]Cyd (specific radioactivity: 21 Ci/mmol) and were obtained from Moravek Biochemicals Inc. (Brea, Ca). EXAMPLE 1 Anti-retrovirus activity of purine and pyrimidine nucleoside analogues. In order to evaluate the inhibitory effects against retrovirus-induced cytopathogenicity in MT-4 cells, said cells (5 x 10⁵ cells/ml) were suspended in fresh culture medium and infected with HIV-1, HIV-2 or SIV at 100 times the cell culture infective dose-50 (CCID₅₀) per ml cell suspension (1 CCID₅₀ being the dose infective for 50% of the cell cultures). Then, 100 µl of the infected cell suspension were transferred to microplate wells, mixed with 100 µl of the appropriate dilutions of the test compounds, and further incubated at 37°C. After 5 days, the number of viable cells was determined in a blood cell-counting chamber by trypan blue staining for both virus-infected and mock-infected cell cultures. The 50% effective concentration (EC₅₀) and 50% cytotoxic concentration (CC₅₀) were defined as the compound concentrations required to reduce by 50% the number of viable cells in the virus-infected and mock-infected cell cultures, respectively. The toxicity of test compounds upon a 2-hr incubation period was determined by exposing MT-4 cells (3.5 x 10⁵ cells/ml) to 100, 20, 4, 0.8 or 0.16 µg/ml of the test compounds for 2 hours at 37°C. Subsequently the cells were washed with culture medium. The pre-treated cells were seeded in microplate wells at 70 x 10³ cells/200 µl-well and allowed to grow for 3 days at 37°C. Control cultures received similar concentrations of the test compounds during the whole incubation period. Then, cells were counted in a Coulter counter (Harpenden Hertz, England) and the CC₅₀ values were determined for each compound. The substituents on the test compounds as well as the results are listed in Table 1. From the data in Table 1, it is clear that the presence of a 3'- spiro group together with substituted silyl groups at both C-2' and C-5' of the ribose are required for optimal inhibitory activity together with low cytotoxicity, thus resulting in a high selectivity Index (S.I.). It is also obvious that the presence of the silyl groups at C-2' and C-5', but not the 3'-spirosubstituent are responsible for the cytotoxic activity of the compounds. The compounds listed in Table 1 that are inhibitory against HIV-1 (HTLV-III B ), were also found to be active against the HIV-1/HE strain at the same order of magnitude. None of the test compounds listed in Table 1 proved effective against HIV-2 (strain ROD) SIV (strain MAC₂₅₁) in MT-4 cells or MSV in C3H/3T3 cells at subtoxic concentrations (data not shown). Compounds 9, 12, 14, 16, 17, were also found inactive against another HIV-2 strain (EHO). EXAMPLE 2 Antiviral and cytotoxic activity of the test compounds upon delayed addition to HIV-1-infected MT-4 cells. MT-4 cells were suspended in culture medium, infected with HIV-1 and brought into microplate wells as described above. Then, 100 µl of the appropriate dilutions of the test compounds 5, 6 and 10, as well as the reference compounds AZT and TIBO were added to the HIV-1-infected MT-4 cell cultures at the time of infection (0 hr), or at 8, 16, 24, 40 or 48 hours after infection. After 5 days, the number of viable cells was determined and the EC₅₀ and CC₅₀ values for the test compounds were defined as described in example 1. Delay of addition of the test compounds by 17-24 hours resulted in a 10-fold decrease of antiviral activity for compounds 5, 6 and 10, and a 2- to 5-fold decrease in activity for AZT and TIBO (data not shown). If the addition of the compounds was delayed by 41 to 48 hours, the antiviral activity of compounds 5, 6 and 10, as well as that of AZT and TIBO, was almost totally lost. However, toxicity of compound 5 for MT-4 cells was not affected by the time that the compound had remained in contact with the cells. In fact, exposure of the MT-4 cells to the test compounds for as short as 24 hours or even 2 hours proved almost as inhibitory to MT-4 cell proliferation as a 1-, 3- or 5-day exposure period. This contrasts with AZT that becomes less cytostatic the shorter its exposure time to MT-4 cells (data not shown). EXAMPLE 3 Inhibition of the incorporation of radiolabelled DNA, RNA or protein precursors into TCA-insoluble MT-4 cell material. The incorporation of [ methyl -³H]dThd, [5-³H]dUrd, [5-³H]dCyd, [5-³H]Urd, [5-³H]Cyd and L-[4,5-³H]1eu into TCA-insoluble MT-4 cell material was measured in wells of a 96-well microtiter plate (Falcon-3072, Becton-Dickinson, New Jersey). To each well were added 10⁵ MT-4 cells, 0.25 µCi of the radiolabelled precursor and a given amount of test compound. The cells were allowed to proliferate for 20 to 24 hr at 37°C in a humidified, CO₂-controlled atmosphere. At the end of this incubation period, the contents of the wells (200 µl) were brought onto 25-mm glass fiber filters (type A/E, Gelman Instrument Company, Ann Arbor, MI), and mounted on a Millipore 3025 sampling manifold apparatus. The filters were washed twice with 2 ml and 5 ml cold NaCl/Pi (phosphate-buffered saline), twice with 2 and 5 ml cold 10% trichloroacetic acid (TCA), twice with 5 and 7.5 ml cold 5% TCA, and twice with 1 ml cold ethanol. The results are shown in Table 2. Most of the most active nucleoside derivatives, including the thymine (5), N³-methylthymine (6), N³-allylthymine (8), N³-dimethylallylthymine (9), uracil (11), cytosine (14) and 5-methylcytosine (16) derivatives, that were not cytotoxic at 100 µg/ml to MT-4 cells (Table 1) did not markedly inhibit the incorporation of dThd, dUrd or dCyd into DNA, or incorporation of Urd or Cyd into RNA or incorporation of leucine into protein at a concentration of 100 µg/ml (Table 2). However, those compounds that proved inhibitory to MT-4 cell proliferation (i.e. compounds 5, 11 and 16) were equally inhibitory to the incorporation of the precursors into DNA, RNA or protein (Table 2). Thus, neither the thymine (5) nor the uracil (11) or 5-methylcytosine (16) derivative showed preferential inhibition of the incorporation of the precursors (dThd, dUrd, dCyd, Urd, Cyd, leu) over the others. EXAMPLE 4 Determination of the partition coefficient (P a ). Partition of the test compounds between 1-octanol (Merck, Darmstadt, Germany) and 10 mM potassium phosphate buffer, pH 7.5 (Merck), was measured as described in Balzarini et al., Biochem, Biophys. Res. Commun. 158: 413-422 (1989). Briefly, a 50 µM concentration of the test compound in potassium phosphate buffer was thoroughly mixed with an equal volume of 1-octanol for 30 min at room temperature. Then, the mixture was further equilibrated at room temperature and UV absorption was measured for the aqueous and alcoholic liquid phases. The partition coëfficient (P a ) was calculated as the ratio of the compound concentration present in the 1-octanol phase to the compound concentration present in the aqueous phase. Thus the partition coëfficients (P a ) were determined for a number of test compounds listed in Table 1. 3'-Azido-2',3'-dideoxythymidine (AZT) was included for comparative purpose. The P a values for AZT and compound 1 were 1.12 and 0.117, respectively. Compounds 2, 3, 4, 5, 6, 7, 8, 11, 14, 15 were found to be present in the n-octanol phase by more than 95% compared to the aqueous phase. Consequently, the P a values could not be accurately determined but were invariably higher than 20. The high P a values of the nucleoside anologues suggest that they might easily cross the blood-brain barrier, a property that should be beneficial in the light of the observations that HIV has marked tropism for the central nervous system. Due to their lipophilic nature, the test compounds most likely also penetrate into the cells by passive diffusion, rather than by a facilitated transport carrier mechanism. Inhibitory effects of substituted nucleoside dervatives according to the present invention on the incorporation of [ methyl -³H]dThd, [5-³H]dUrd, [5-³H]dCyd, [5-³H]Urd, [5-³H]Cyd and L-[4,5-³H]leucine into MT-4 cell DNA, RNA or protein synthesis, respectively. Compound IC₅₀ (µg/ml) [ methyl -³H]dThd [5-³H]dUrd [5-³H]dCyd [5-³H]Urd [5-³H]Cyd L-[4,5-³H]leucine 5 13 9.1 16 11 8.0 11.6 6 >100 >100 >100 >100 >100 >100 8 >100 >100 >100 >100 >100 >100 9 >100 >100 >100 >100 >100 >100 11 38 12 18 11 11 14 14 >100 >100 >100 >100 >100 >100 16 14 9.9 14 8.9 11 13

Claims: Substituted nucleoside derivatives of the general formula: wherein: B represents: a pyrimidine of the general formula: wherein: X₅ is a sidechain selected from the group consisting of H, alkyl, alkenyl, alkynyl, benzyl, halogen, cyano, thiocyano, -CH=CHR, hydroxymethyl, -CH₂CH₂-halogen, nitro, amino; X₄ is a sidechain selected from the group consisting of OH, SH, NH₂, NHCH₃, N(CH₃)₂, NHCOCH₃; X₃ is a sidechain selected from the group consisting of H, alkyl, alkenyl, alkynyl, benzyl; X₂ is a sidechain selected from the group consisting of O, S, Se; or aza- and deaza-derivatives thereof; a purine of the general formula: wherein X₆ is a sidechain selected from the group consisting of H, OH, halogen, NH₂, NHCH₃, N(CH₃)₂; X₇ is a sidechain selected from the group consisting of H, alkyl, monomethoxytrityl; or aza- and deazaderivatives thereof; a benzimidazole of the general formula: wherein X₈ are sidechains selected from the group consisting of halogen, amino, alkyl, alkenyl, alkynyl, mercapto; an imidazole of the general formula: wherein: X₉ is a sidechain selected from the group consisting of H, alkyl, alkenyl, alkynyl, amino, mercapto; a triazole of the general formula: wherein X₁₀ is a sidechain selected from the group consisting of H, alkyl, alkenyl, alkynyl, amino, mercapto; a sidechain of the formula R₃' represents a sidechain of the formula: wherein R₁ is a sidechain selected from the group consisting of H, alkyl, alkenyl, alkynyl; or a sidechain of the general formula: wherein R₂ is a sidechain selected from the group consisting of H, alkyl, alkenyl, alkynyl, amino, mercapto; R₅' and R₂' are the same or different and represent a side-chain selected from the group consisting of trimethylsilyl, tert -butyldimethylsilyl, tert -butyldiphenylsilyl, dimethylphenylsilyl, alkyl (optionally substituted with amino, hydroxyl, ether) aryl, (CH₂) n phenyl with n=1-4; wherein the sugar is a pentose selected from the group consisting of ribose, arabinose, lyxose, xylose; or a hexose selected from the group consisting of glucose, mannose, galactose. Nucleoside-derivative as claimed in claim 1, wherein the derivative is a N³-alkylated 2',5'-silylated 3'-spiro-5''-[4''-amino-1'',2''-oxathiole-2'',2''-dioxide]thymidine analogue. Nucleoside-derivative as claimed in claim 2, wherein the derivative is {1-[2',5'-bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-methyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2-dioxide}. Nucleoside-derivative as claimed in claim 2, wherein the derivative is {1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-ethyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide}. Therapeutic composition for use in the treatment of AIDS- or AIDS-related diseases which comprises as an active ingredient a nucleoside-derivative of formula I or II. Therapeutic composition as claimed in claim 5, comprising said active ingredient in a concentration ranging from about 0.1-100% by weight. Therapeutic composition as claimed in claim 6, having the form which is selected from the group consisting of powders, suspensions, solution, sprays, emulsions, unguents and creams. A nucleoside-derivative of formula I or II for use in the treatment of AIDS and AIDS-related diseases. N3-alkylated 2',5'-silylated 3'-spiro-5''-[4''-amino-1'',2''-oxathiole-2'',2''-dioxide]thymidine analogue for use in the treatment of AIDS and AIDS-related diseases. 1-[2',5'-bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-methyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide} for use in the treatment of AIDS and AIDS-related diseases. 1-[2',5'-Bis- O -( tert -butyldimethylsilyl)-β- D -ribofuranosyl]-3-N-ethyl-thymine}-3'-spiro-5''-{4''-amino-1'',2''-oxathiole-2'',2''-dioxide} for use in the treatment of AIDS and AIDS-related diseases. The use of a nucleoside-derivative of formula I or II for preparing a therapeutic composition against AIDS- or AIDS-related diseases. Method for preparing substituted nucleoside derivatives of formula I or II. a) by starting with a 3'-keto nucleoside of the formula: wherein B represents a pyrimidine, purine, benzimidazole, imidazole or triazole; Si can optionally be substituted with alkyl or phenyl replacing the 3'-keto group therein by cyanohydrin; and the pentose ring can optionally be a hexose ring b) converting said cyanohydrin to cyanomesylate; c) converting said cyanomesylate to a spiro group; and d) optionally removing one or more protecting silyl groups. Method for preparing substituted nucleoside derivatives of formula I or II by : a) using as a starting material a compound of formula: wherein the pentose ring can also be a hexose ring; b) converting the 3'-keto group therein through a cyanohydrin group to a cyanomesylate group; c) converting the isopropylidene dioxy group in the 1,2-positions to two acetyloxy groups; d) replacing the acetyloxy group in the 1-position by a residue of a pyrimidine or purine; e) converting the cyanomesylate group in the 3'-position to a spiro -group; f) silylating one or both hydroxyl groups in the 2' and 5'position; and g) optionally deprotecting one of said silylated hydroxy groups.

Inventors: BALZARINI JAN MARIA RENE, CAMARASA-RIUS MARIA-JOSE, DE CLERCQ ERIK DESIRE ALICE, PEREZ-PEREZ MARIA-JESUS, SAN-FELIX-GARCIA ANA, BALZARINI, JAN MARIA RENE, CAMARASA-RIUS, MARIA-JOSE, DE CLERCQ, ERIK DESIRE ALICE, PEREZ-PEREZ, MARIA-JESUS, SAN-FELIX-GARCIA, ANA, Balzarini, Jan Maria René , Camarasa-Rius, Maria-José, De Clercq, Erik Désiré Alice, Pérez-Pérez, Maria-Jesùs, San-Félix-Garcia, Ana
Applicants: CONSEJO SUPERIOR INVESTIGACION, STICHTING REGA V Z W, CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS, STICHTING REGA V.Z.W.
Application year: 1991
Main classification: C07H19
IPC codes: A61K31, C07H19, C07D473, A61P31