Base Modification and the Phosphoramidite Approach

Abstract
Oligodeoxynucleotides 18–150 bases in length were synthesized with both 0-(2-cyanoethyl)- and 0-(methyl)-phosphoramidites. After enzymatic degradation of the purified products, base modification and composition were evaluated by HPLC. Additionally, synthesis of 5′-d[GCGCGCTT] with O-(methyl) phosphorus protection generated 3-methylthymidine when thiophenoxide was omitted from the deprotection protocol.