title: O-selectivity and utility of phosphorylation mediated by phosphite triester intermediates in the N-unprotected phosphoramidite method.
abstract: Previously, O-selective phosphorylation on polymer supports in the N-unprotected phosphoramidite method could not be carried out because the amino groups of dA and dC have high reactivity toward tervalent phosphorus(III)-type phosphitylating reagents. In this paper, we developed a new coupling strategy named the "activated phosphite method" in which the phosphitylation is mediated by phosphite triester intermediates 1. Application of 1-hydroxybenzotriazole as the promoter to the solid-phase synthesis resulted in excellent O-selectivity of more than 99.7%. This O-selectivity was explained by the frontier molecular orbital interactions between the reactive intermediates and the nucleophiles such as the amino or hydroxyl groups of nucleosides. Furthermore, longer oligonucleotides were synthesized not only by a manual operation but also by a DNA synthesizer. The utility of our new method was demonstrated by the successful synthesis of a base-labile modified oligodeoxyribonucleotide having 4-N-acetyldeoxycytidine residues. Finally, DNA 20-mers containing dA or dC could be synthesized in good yields by use of a combined reagent of 6-trifluoromethyl-1-hydroxybenzotriazole and benzimidazolium triflate.
authors.affiliation: Contribution from the Department of Life Science, Tokyo Institute of Technology, Division of Bioscience and Biotechnology, Frontier Collaborative Research Center, 4259 Nagatsuta, Midoriku, Yokohama 226-8501, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ohkubo
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ezawa
authors.forename: Kohji
authors.initials: K
authors.lastname: Seio
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Sekine
mesh_terms: D004247:DNA / Q000737:chemistry; D003839:Deoxyadenosines / Q000737:chemistry; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000737:chemistry; D008958:Models, Molecular; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis* / Q000737:chemistry; D009841:Oligonucleotides / Q000138:chemical synthesis* / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000737:chemistry*; D017905:Phosphites / Q000737:chemistry*; D010766:Phosphorylation; D013816:Thermodynamics
chemical_list: D003839:Deoxyadenosines; D009838:Oligodeoxyribonucleotides; D009841:Oligonucleotides; D009943:Organophosphorus Compounds; D017905:Phosphites; C434331:phosphoramidite; D003841:Deoxycytidine; D004247:DNA