Modified 4′-nucleosides as antiviral agents

1. A compound which is a β-D- and β-L-nucleoside or a pharmaceutically acceptable salt thereof, having a structure defined by formula (I) or by formula (II):

wherein:

X is hydrogen, F, Cl, Br, I, NH 2 , NHR 4 , NR 4 R 5 , NHOH, NHOR 4 , NHNH 2 , NR 4 NH 2 , NHNHR 4 , SH, SR 4 , S(O) b R 4 , OH, OR 4 , N 3 , CN, or CF 3 ;

Y is hydrogen, F, Cl, Br, I, NH 2 , NHR 4 , NR 4 R 5 , NHOH, NHOR 4 , NHNH 2 , NR 4 NH 2 , NHNHR 4 , SH, SR 4 , S(O) b R 4 , OH, OR 4 , N 3 , CN, CF 3 , hydroxymethyl, methyl, substituted or unsubstituted ethyl, substituted or unsubstituted vinyl, substituted or unsubstituted 2-bromovinyl, or substituted or unsubstituted ethynyl;

R 1 is F or N 3 ;

R 2 is OH, OR 4 , OC(O)R 4 , —OP(O)(OQ) a (NHR 4 ) b , SH, SR 4 , S(O) b R 4 , SC(O)R 4 , NH 2 , NHC(O)R 4 , NHR 4 , NR 4 R 5 , NHOH, NHOR 4 , NHNH, NR 4 NH 2 , or NHNHR 4 ;

R 3 is F, cyano, azido, ethynyl, chlorovinyl, fluorovinyl, alkyl (C 2-6 ), one to three halogen substituted alkyl (C 1-6 ), alkenyl or alkynyl (C 2-6 );

Z is O, S, CH 2 or C═CH 2 ;

A is N, CH, or CF; and

R 4 and R 5 are the same or different and are lower alkyl, lower alkenyl, acyl of carbon 1-17, aryl, or aralkyl;

M is at least one member selected from the group consisting of H + , Na + , and K + ;

and

a has a value of 0 or 1, b has a value of 1 or 2, and Q is M or R 4 .

2. The compound of claim 1 , wherein the nucleoside is a 4′-C-substituted-3′-fluoro-2′,3′-dideoxynucleoside.

3. The compound of claim 1 , wherein the nucleoside is a 4′-C-substituted-3′-azido-2′,3′-dideoxynucleoside.

4. The compound of claim 1 , wherein the nucleoside is a 4′-C-ethynyl-3′-fluoro-2′,3′-dideoxynucleoside.

5. The compound of claim 1 , wherein the nucleoside is a 4′-C-ethynyl-3′-azido-2′,3′-dideoxynucleoside.

6. The compound of claim 1 , wherein the nucleoside is a 4′-C-ethynyl-3′-fluoro-3′-deoxythymidine.

7. The compound of claim 1 , wherein the nucleoside is a 4′-C-ethynyl-3′-azido-3′-deoxythimidine.