title: Permanent or reversible conjugation of 2'-O- or 5'-O-aminooxymethylated nucleosides with functional groups as a convenient and efficient approach to the modification of RNA and DNA sequences.
abstract: 2'-O-Aminooxymethyl ribonucleosides are prepared from their 3',5'-disilylated 2'-O-phthalimidooxymethyl derivatives by treatment with NH(4)F in MeOH. The reaction of these novel ribonucleosides with 1-pyrenecarboxaldehyde results in the efficient formation of stable and yet reversible ribonucleoside 2'-conjugates in yields of 69-82%. Indeed, exposure of these conjugates to 0.5 M tetra-n-butylammonium fluoride (TBAF) in THF results in the cleavage of their iminoether functions to give the native ribonucleosides along with the innocuous nitrile side product. Conversely, the reaction of 5-cholesten-3-one or dansyl chloride with 2'-O-aminooxymethyl uridine provides permanent uridine 2'-conjugates, which are left essentially intact upon treatment with TBAF. Alternatively, 5'-O-aminooxymethyl thymidine is prepared by hydrazinolysis of its 3'-O-levulinyl-5'-O-phthalimidooxymethyl precursor. Pyrenylation of 5'-O-aminooxymethyl thymidine and the sensitivity of the 5'-conjugate to TBAF further exemplify the usefulness of this nucleoside for modifying DNA sequences either permanently or reversibly. Although the versatility and uniqueness of 2'-O-aminooxymethyl ribonucleosides in the preparation of modified RNA sequences is demonstrated by the single or double incorporation of a reversible pyrenylated uridine 2'-conjugate into an RNA sequence, the conjugation of 2'-O-aminooxymethyl ribonucleosides with aldehydes, including those generated from their acetals, provides reversible 2'-O-protected ribonucleosides for potential applications in the solid-phase synthesis of native RNA sequences. The synthesis of a chimeric polyuridylic acid is presented as an exemplary model.
authors: Division of Therapeutic Proteins, Center for Drug Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, MD 20892, USA.
authors: Jacek
authors: J
authors: Cieslak
authors: Andrzej
authors: A
authors: Grajkowski
authors: Cristina
authors: C
authors: Ausín
authors: Alexei
authors: A
authors: Gapeev
authors: Serge L
authors: SL
authors: Beaucage
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry; D011072:Poly U / Q000138:chemical synthesis / Q000737:chemistry; D012313:RNA / Q000138:chemical synthesis / Q000737:chemistry*; D012263:Ribonucleosides / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D010091:Oximes; D012263:Ribonucleosides; D011072:Poly U; D012313:RNA; D004247:DNA