Oligomeric compounds comprising 4′-thionucleosides for use in gene modulation

1. A compound of formula (I):

wherein:

T 1 is H or a protecting group;

T 2 is a phosphoramidite group;

Bx is hydrogen or a nucleobase;

X is fluoro, substituted or unsubstituted —O—C 1 -C 12 alkyl, substituted or unsubstituted —O—C 2 -C 12 alkenyl, or substituted or unsubstituted —O—C 2 -C 12 alkynyl.

2. The compound of claim 1 , wherein X is a group of formula Ia:

wherein:

R b is O;

R d is a single bond, O, S or C(═O);

R e is C 1 -C 10 alkyl, N(R k )(R m ), N(R k )(R n ), N═C(R p )(R q ), N═C(R p )(R r ) or has formula Ic;

R p and R q are each independently hydrogen or C 1 -C 10 alkyl;

R r is —R x —R y ;

each R s , R t , R u and R v is, independently, hydrogen, C(O)R w , substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 2 -C 10 alkenyl, substituted or unsubstituted C 2 -C 10 alkynyl, alkylsulfonyl, arylsulfonyl, a chemical functional group or a conjugate group, wherein the substituent groups are selected from hydroxyl, amino, alkoxy, carboxy, benzyl, phenyl, nitro, thiol, thioalkoxy, halogen, alkyl, aryl, alkenyl and alkynyl;

or optionally, R u and R v , together form a phthalimido moiety with the nitrogen atom to which they are attached;

each R w is, independently, substituted or unsubstituted C 1 -C 10 alkyl, trifluoromethyl, cyanoethyloxy, methoxy, ethoxy, t-butoxy, allyloxy, 9-fluorenylmethoxy, 2-(trimethylsilyl)-ethoxy, 2,2,2-trichloroethoxy, benzyloxy, butyryl, iso-butyryl, phenyl or aryl;

R k is hydrogen, an amino protecting group or —R x —R y ;

R x is a bond or a linking moiety;

R y is a chemical functional group, a conjugate group or a solid support medium;

each R m and R n is, independently, H, an amino protecting group, substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 2 -C 10 alkenyl, substituted or unsubstituted C 2 -C 10 alkynyl, wherein the substituent groups are selected from hydroxyl, amino, alkoxy, carboxy, benzyl, phenyl, nitro, thiol, thioalkoxy, halogen, alkyl, aryl, alkenyl and alkynyl;

or R m and R n , together, are an amino protecting group, are joined in a ring structure that optionally includes an additional heteroatom selected from N and O or are a chemical functional group;

m a is 1 to about 10;

each mb is, independently, 0 or 1;

mc is 0 or an integer from 1 to 10;

m d is an integer from 1 to 10; and

provided that when mc is 0, and is greater than 1.

3. The compound of claim 1 , wherein X is selected from fluoro or substituted or unsubstituted —O—C 1 -C 12 alkyl.

4. The compound of claim 1 , wherein X is selected from fluoro, —O—CH 3 , or —O—CH 2 CH 2 —O—CH 3 .

5. The compound of claim 1 , wherein X is O-allyl, O—(CH 2 ) ma —O—N(R m )(R n ) or O—CH 2 —C(═O)—N(R m )(R n );

wherein:

each R m and R n is, independently, H, an amino protecting group, substituted or unsubstituted C 1 -C 10 alkyl, substituted or unsubstituted C 2 -C 10 alkenyl, substituted or unsubstituted C 2 -C 10 alkynyl; and

ma is from 1 to about 10.

6. The compound of claim 1 , wherein said phosphoramidite group is —P[N[(CH(CH 3 ) 2 ] 2 )O(CH 2 ) 2 CN.