Modified fluorinated nucleoside analogues

1. A (2′R)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D or β-L) or its pharmaceutically acceptable salt of the structure:

wherein Base is a pyrimidine base represented by the following formula

X is O; R 1 and R 7 are independently H, a monophosphate, a diphosphate, a triphosphate, a H-phosphonate, alkyl, an alkyl sulfonyl, or an arylalkyl sulfonyl; and

R 3 is H and R 4 is NH 2 or OH.

2. The (2′R)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D or β-L) of claim 1 or its pharmaceutically acceptable salt thereof, wherein R 7 is H and R 1 is a monophosphate, or diphosphate, or a triphosphate.

3. The (2′R)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D) of claim 1 or its pharmaceutically acceptable salt thereof, R 7 is H and R 1 is a diphosphate or a triphosphate.

4. A (2′R)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D or β-L) of claim 1 or its pharmaceutically acceptable salt thereof wherein R 7 is H and R 1 is a triphosphate.

5. (2′)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D or β-L) of claim 1 or its pharmaceutically acceptable salt thereof wherein R 1 and R 7 are H.

6. A (2′R)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D) or its pharmaceutically acceptable salt thereof of the formula:

7. A pharmaceutical composition comprising the nucleoside of claim 1 or its pharmaceutically acceptable salt and a pharmaceutically acceptable carrier.

8. The pharmaceutical composition comprising the nucleoside of claim 2 or its pharmaceutically acceptable salt and a pharmaceutically acceptable carrier.

9. The pharmaceutical composition comprising the nucleoside of claim 3 or its pharmaceutically acceptable salt and a pharmaceutically acceptable carrier.

10. A pharmaceutical composition comprising the nucleoside of claim 4 or its pharmaceutically acceptable salt and a pharmaceutically acceptable carrier.

11. A pharmaceutical composition comprising the nucleoside of claim 5 or its pharmaceutically acceptable salt and a pharmaceutically acceptable carrier.

12. A pharmaceutical composition comprising the nucleoside of claim 6 or its pharmaceutically acceptable salt and a pharmaceutically acceptable carrier.

13. A method of synthesizing a nucleoside of claim 1 , which comprises glycosylating the pyrimidine with a compound having the following structure;

wherein R is lower alkyl, acyl, benzoyl, or mesyl; and Pg is selected from among C(O)-alkyl, C(O)Ph, C(O)aryl, CH 3 , CH 2 -alkyl, CH 2 -alkenyl, CH 2 Ph, CH 2 -aryl, CH 2 O-alkyl, CH 2 O-aryl, SO 2 -alkyl, SO 2 -aryl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, or both Pg's may come together to for a 1,3-(1,1,3,3-tetraisopropyldisiloxanylidene).

14. A method of synthesizing the nucleoside of claim 1 , which comprises selectively deprotecting a 3′-OPg or a 5′-OPg of a compound having the following structure:

wherein each Pg is independently a protecting group selected from among C(O)-alkyl, C(O)Ph, C(O)aryl, CH 3 , CH 2 -alkyl, CH 2 -alkenyl, CH 2 Ph, CH 2 -aryl, CH 2 O-alkyl, CH 2 O-aryl, SO 2 -alkyl, SO 2 -aryl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, or both Pg's may come together to for a 1,3-(1,1,3,3-tetraisopropyldisiloxanylidene).

15. A (2′R)-2′-deoxy-2′-fluoro-2′-C-methyl nucleoside (β-D) or its pharmaceutically acceptable salt thereof of the formula:

16. A pharmaceutical composition comprising the nucleoside of claim 15 or its pharmaceutically acceptable salt and optionally a pharmaceutically acceptable carrier.

17. A liposomal composition comprising liposomes comprising the compound of claim 1 and optionally a pharmaceutically acceptable carrier.

18. A liposomal composition comprising liposomes comprising the compound of claim 6 and optionally a pharmaceutically acceptable carrier.

19. A liposomal composition comprising liposomes comprising the compound of claim 15 and optionally a pharmaceutically acceptable carrier.