Thiocarbon-protecting groups for rna synthesis

A method comprising:

• (a) providing a nucleoside residue, wherein said nucleoside residue comprises an unprotected hydroxyl group and a 2′-protected nucleotide monomer, wherein said 2′-protected nucleotide monomer has the structure of formula (II):
• wherein:
• BP is a protected or unprotected heterocyclic group having a 3 to 20 membered ring system;
• one of R1 and R2 is a protecting group, and the other of R1 and R2 is a phosphoramidite group;
• W is —NH2, —NH—R4 or —NR4—R5, —NH—O—R4 or —NR4—O—R5, wherein R4 and R5 are independently selected from a hydrocarbyl, a substituted hydrocarbyl, an aryl or a substituted aryl, wherein R4 and R5 are optionally cyclically linked;
• and
• (b) contacting said nucleoside residue with said 2′-protected nucleotide monomer under conditions sufficient to covalently bond said phosphoramidite group of said 2′-protected nucleotide monomer to said unprotected hydroxyl group of said nucleoside residue and produce an internucleotide bond.

A 2′-O-protected nucleic acid comprising the structure:

• wherein:
• BP is a protected or unprotected heterocyclic group having a 3 to 20 membered ring system;
• Q is a thiocarbon protecting group having one of the following structures:
• —C(═S)—W,
• W is NH2, —NH—R4 or —NR4—R5, —NH—O—R4 or —NR4—O—R5, wherein R4 and R5 are independently selected from a hydrocarbyl, a substituted hydrocarbyl, an aryl or a substituted aryl, wherein R4 and R5 are optionally cyclically linked;
• R12 is selected from the group consisting of hydrogen, a hydrocarbyl, a substituted hydrocarbyl, an aryl and a substituted aryl;
• and
• m is an integer of at least 1.