title: Thermolytic properties of 3-(2-pyridyl)-1-propyl and 2-[N-methyl-N-(2-pyridyl)]aminoethyl phosphate/thiophosphate protecting groups in solid-phase synthesis of oligodeoxyribonucleotides.
abstract: Thermolytic groups may serve as alternatives to the conventional 2-cyanoethyl group for phosphate/thiophosphate protection in solid-phase oligonucleotide synthesis to prevent DNA alkylation by acrylonitrile generated under the basic conditions used for oligonucleotide deprotection. Additionally, thermolytic groups are attractive in the context of engineering a "heat-driven" process for the synthesis of oligonucleotides on diagnostic microarrays. In these regards, the potential application of pyridine derivatives as thermolytic phosphate/thiophosphate protecting groups has been investigated. Specifically, 2-pyridinepropanol and 2-[N-methyl-N-(2-pyridyl)]aminoethanol were incorporated into deoxyribonucleoside phosphoramidites 7a-d and 9, which were found as efficient as 2-cyanoethyl deoxyribonucleoside phosphoramidites in solid-phase oligonucleotide synthesis. Whereas the removal of 3-(2-pyridyl)-1-propyl phosphate/thiophosphate protecting groups from oligonucleotides is effected within 30 min upon heating at 55 degrees C in concentrated NH4OH or in an aqueous buffer at pH 7.0, cleavage of 2-[N-methyl-N-(2-pyridyl)]aminoethyl groups occurs spontaneously when their phosphate or phosphorothioate esters are formed during oligonucleotide synthesis. The deprotection of these groups follows a cyclodeesterification process generating the bicyclic salts 13 and 14 as side products. These salts do not alkylate or otherwise modify any DNA nucleobases and do not desulfurize a phosphorothioate diester model under conditions mimicking large-scale oligonucleotide deprotection.
authors.affiliation: Division of Therapeutic Proteins, Center for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, Maryland 20892, USA.
authors.forename: Jacek
authors.initials: J
authors.lastname: Cieślak
authors.forename: Serge L
authors.initials: SL
authors.lastname: Beaucage
mesh_terms: D001483:Base Sequence; D006358:Hot Temperature; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis* / Q000737:chemistry; D010755:Organophosphates / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D013873:Thionucleotides / Q000737:chemistry
chemical_list: D009838:Oligodeoxyribonucleotides; D010755:Organophosphates; D010710:Phosphates; D013873:Thionucleotides; C035638:thiophosphoric acid