Precursors for use in the synthesis of polynucleotides are disclosed. The precursors include a heterocyclic base having an exocyclic amine group and a substituted or unsubstituted triaryl methyl protecting group bound to the exocyclic amine group. In particular embodiments, the precursor has the structure:wherein:O and H represent oxygen and hydrogen, respectively,R1 is hydrido, hydroxyl, protected hydroxyl, lower alkyl, modified lower alkyl, or alkoxy,one of R2 or R3 is a hydroxyl protecting group; and the other of R2 or R3 is a reactive group capable of reacting with a reactive site hydroxyl,Base is a heterocyclic base having an exocyclic amine group, andTram is a triaryl methyl group having the structure (V)wherein the broken line represents a bond to the amino nitrogen of the exocyclic amine group, and R4, R5 and R6 are independently selected from unsubstituted or substituted aryl groups, provided that at least one of R4, R5, and R6 is an aryl group other than phenyl and other than substituted phenyl.