Nucleic Acids Research, 1986, Vol. 14, No. 16 6453-6470
© 1986
Articles |
Prevention of guanine modification and chain cleavage during the solid phase synthesis of oligonucleotides using phosphoramidite derivatives
Department of Medical Biochemistry, University of Calgary Calgary, Alberta T2N 4N1 1Department of Chemistry, McGill University Montreal, Quebec H3A 2K6, Canada
*To whom correspondence should be addressed
Received June 5, 1986. Revised August 4, 1986. Accepted August 4, 1986.
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 i) blocking the O6-position with a 2-cyanoethyl protecting group for deoxyribonucleotides or with a p-nitrophenylethyl group for ribonucleotides, ii) regenerating the guanine base with water or acetate ions, or iii) 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.