Nucleic acid chemical modifications

The nucleoside of claim, 1 represented by formula (3):

• or isomers thereof, wherein:
• one of D1 and D2 is H or a hydroxyl protecting group and the other of D1 and D2 is H, a hydroxyl protecting group, or a reactive phosphorus group;
• B is selected from the group consisting of hydrogen, unsubstituted or substituted aliphatic, a natural nucleobase, a modified nucleobase, and a universal base;
• Q is selected from the group consisting of O, S, NR10, and CH2;
• W is absent, O, S or NR′;
• R100 and R200 are each independently selected from the group consisting of hydrogen, unsubstituted and substituted aliphatic, aryl, halogen, heteroaryl, and heterocyclic;
• R300 and R400 are each independently selected from the group consisting of hydrogen, unsubstituted or substituted aliphatic, aryl, halogen, heteroaryl, and heterocyclic;
• or R300 and R400 are taken together with the atom to which they are bound to form a carbonyl, thiocarbonyl, ═NR20, ═N—NR20R30, or ═N—NR20C(O)R10;
• Z is selected from the group consisting of OR10, COR10, CO2R10,
• NR20R30, CONR20R30, CON(H)NR20R30, ONR20R30, CON(H)N═CR40R50, N(R20)C(═NR30)NR20R30, N(R20)C(O)NR20R30, N(R20)C(S)NR20R30, OC(O)NR20R30, SC(O)NR20R30, N(R20)C(S)OR10, N(R20)C(O)OR10, N(R20)C(O)SR10, N(R20)N═CR40R50, ON═CR40R50, SO2R10, SOR10, SR10, and substituted or unsubstituted heterocyclic;
• R20 and R30 are each independently selected from the group consisting of hydrogen, acyl, unsubstituted or substituted aliphatic, aryl, heteroaryl, heterocyclic, OR10, COR10, CO2R10, and NR10R10′;
• or R20 and R30 are taken together with the atom to which they are bound to form a heterocyclic ring;
• R40 and R50 are each independently selected from the group consisting of hydrogen, acyl, unsubstituted or substituted aliphatic, aryl, heteroaryl, heterocyclic, OR10, COR10, CO2R10, and NR10R10′;
• and
• R10 and R10′ are each independently hydrogen, unsubstituted or substituted aliphatic, aryl, heteroaryl, or heterocyclic.

An oligonucleotide comprising at least one nucleoside of formula (2):

• or isomers thereof, wherein:
• m is an integer from 1 to 15;
• B is selected from the group consisting of hydrogen, unsubstituted or substituted aliphatic, a natural nucleobase, a modified nucleobase, and a universal nucleobase;
• Q is selected from the group consisting of O, S, NR10, and CH2;
• W is absent, O, S or NR′;
• V is a straight or branched, substituted or unsubstituted alkylene, substituted or unsubstituted alkoxylene, substituted or unsubstituted alkenylene, or substituted or unsubstituted alkynylene, wherein the backbone of the alkylene, alkoxylene, alkenylene, or alkynylene may contain one or more of O, S, S(O), SO2, N(R′), C(O), substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted heterocyclic, or substituted or unsubstituted cycloalkyl;
• R′ is hydrogen, acyl, unsubstituted or substituted aliphatic;
• Z is selected from the group consisting of OR10, COR10, CO2R10,
• NR20R30, CONR20R30, CON(H)NR20R30, ONR20R30, CON(H)N═CR40R50, N(R20)C(═NR30)NR20R30, N(R20)C(O)NR20R30, N(R20)C(S)NR20R30, OC(O)NR20R30, SC(O)NR20R30, N(R20)C(S)OR10, N(R20)C(O)OR10, N(R20)C(O)SR10, N(R20)N═CR40R50, ON═CR40R50, SO2R10, SOR10, SR10, and substituted or unsubstituted heterocyclic;
• R20 and R30 for each occurrence are independently selected from the group consisting of hydrogen, acyl, unsubstituted or substituted aliphatic, aryl, heteroaryl, heterocyclic, OR10, COR10, CO2R10, and NR10R10′;
• or R20 and R30 are taken together with the atom to which they are bound to form an unsubstituted or substituted heterocyclic ring;
• R40 and R50 for each occurrence are independently selected from the group consisting of hydrogen, acyl, unsubstituted or substituted aliphatic, aryl, heteroaryl, heterocyclic, OR10, COR10, CO2R10, and NR10R10′;
• and
• R10 and R10′ are each independently hydrogen, unsubstituted or substituted aliphatic, aryl, heteroaryl, or heterocyclic;
• provided that when W is O and Z is OR10, V is not an unsubstituted alkylene or an unsubstituted alkoxylene.