title: Novel method of synthesis of 5''-phosphate 2'-O-ribosyl-ribonucleosides and their 3'-phosphoramidites.
abstract: Synthesis of 5''-phosphate 2'-O-ribosylribonucleosides [Nr(p)] of four common ribonucleosides, and 3'-phosphoramidites of 5''-phosphate 2'-O-ribosyladenosine and 2'-O-ribosylguanosine using the H-phosphonate chemistry is described. An additional ring protected by benzoyl groups was incorporated into the main ribosyl ring in the reaction with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose in the presence of SnCl4. The obtained 2'-O-ribosylribonucleosides (Nr) were applied in the subsequent transformations with selective deprotection. Ethanolamine was applied as a very convenient reagent for selective removal of benzoyl groups. Additionally, the tetraisopropyldisiloxane-1,3-diyl (TIPDSi) group was found to be stable under these deprotection conditions. Thus, the selectively deprotected 5''-hydroxyl group of Nr was transformed into an H-phosphonate monoester which was found to be stable under the following conditions: the removal of the TIPDSi group with triethylammonium fluoride and the dimethoxytritylation of the 5''-hydroxyl function. The 5''-H-phosphonate of Nr precursors was easily transformed to the corresponding dicyanoethyl 5''-O-phosphotriesters before phosphitylation, which gave 3'-phosphoramidite units of Nr(p) in high yield. The derived phosphoramidite units were used in an automated oligonucleotide synthesizer to produce dimer Ar(p)T via the phosphoramidite approach. The obtained products were fully deprotected under standard deprotection conditions giving dimers with a 5''-phosphate monoester function. Application of an alkaline phosphatase to prove the presence of an additional phosphate group was described.
authors.forename: Marcin K
authors.initials: MK
authors.lastname: Chmielewski
authors.affiliation: Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, Poznan PL-61704, Poland. markwt@ibch.poznan.pl.
authors.forename: Wojciech T
authors.initials: WT
authors.lastname: Markiewicz
mesh_terms: D002851:Chromatography, High Pressure Liquid; D020650:Combinatorial Chemistry Techniques; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000032:analysis / Q000138:chemical synthesis*; D012263:Ribonucleosides / Q000032:analysis / Q000138:chemical synthesis*
chemical_list: D009943:Organophosphorus Compounds; D012263:Ribonucleosides; C434331:phosphoramidite