Oligonucleotides having alkylphosphonate linkages and methods for their preparation

A process of preparing an alkylphosphonate compound of the structure:

• wherein
• each M1 and M2 independently, are hydrogen or a hydroxyl protecting group or one of M1 and M2 is hydrogen or a hydroxyl protecting group and the other of M1 and M2 is a covalent attachment to a solid support;
• each J is, independently, hydrogen, a 2′-substituent group, or a protected 2′-substituent group;
• R1 is an electron withdrawing group;
• X2 is hydrogen or —(CH2)m—E2;
• E2 is hydrogen, alkyl, aryl, aralkyl, substituted aryl, a heterocycle, mixed heterocycle or heteroaryl;
• m is 0, 1, 2 or 3;
• and
• Bx is a heterocyclic base moiety;
• comprising the steps of:
• a) selecting a dimeric trialkylphosphite compound of the structure:
• and
• b) treating said dimeric trialkylphosphite compound, in a solvent, with a base under conditions of time temperature and pressure to form said alkylphosphonate compound.