title: Prevention of guanine modification and chain cleavage during the solid phase synthesis of oligonucleotides using phosphoramidite derivatives.
abstract: Phosphoramidite reagents can phosphitylate guanine bases at the O6-position during solid phase synthesis and serious chain cleavage occurs if the base phosphitylation is not eliminated before the iodine/water oxidation step. This can be accomplished by blocking the O6-position with a 2-cyanoethyl protecting group for deoxyribonucleotides or with a p-nitrophenylethyl group for ribonucleotides, regenerating the guanine base with water or acetate ions, or using N-methylanilinium trifluoroacetate (TAMA) as the phosphoramidite activator. The effectiveness of these methods was demonstrated by both 31P NMR studies and by the synthesis of d(Gp)23G, (Gp)14G, and d-(Gp)13rG sequences.
mesh_terms: D000577:Amides; D004591:Electrophoresis, Polyacrylamide Gel; D006147:Guanine; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008722:Methods; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis*; D010756:Phosphoric Acids; D013329:Structure-Activity Relationship
chemical_list: D000577:Amides; D007202:Indicators and Reagents; D009838:Oligodeoxyribonucleotides; D010756:Phosphoric Acids; D006147:Guanine; C011067:phosphoramidic acid