- A simplified and efficient route to 2′-O, 4′-C-methylene-linked bicyclic ribonucleosides (locked nucleic acid)
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A novel efficient method for the synthesis of locked nucleic acid (LNA) monomers is described. The LNA 5′,3′-diols containing thymine, 4-N-acetyl- and 4-N-benzoylcytosine, 6-N-benzoyladenine, and 2-N-isobutyrylguanine as nucleobases were prepared via convergent syntheses. The method is based on the use of the common sugar intermediate 1,2-di-O-acetyl-3-O-benzyl-4-C-methanesulfonoxymethyl- 5-O-methanesulfonyl-D-erythro-pentofuranose (8) that easily can be prepared from D-glucose in multigram scale. Four different nucleobases were stereoselectively coupled to 8 using a modified Vorbrueggen procedure to give the corresponding 4′-C-branched nucleoside derivatives. Subsequent ring closing furnished the protected LNA nucleosides. The 5′-O-mesyl groups were efficiently displaced by nucleophilic substitution using sodium benzoate. Saponification of the 5′-benzoates followed by catalytic removal of the 3′-O-benzyl groups afforded the free LNA diols. The exocyclic amino groups of adenosine and cytidine were selectively acylated to give 4-N-acetyl- or 4-N-benzoyl-LNA-C and 6-N-benzoyl-LNA-A. The isobutyryl group of guanine was retained during the preparation of 2-N-isobutyryl-LNA-G. The LNA-T diol and base-protected LNA diols can be directly converted into LNA-phosphoramidites for automated chemical synthesis of LNA containing oligonucleotides.
- Koshkin,Fensholdt,Pfundheller,Lomholt
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- Synthesis of 2′-O,4′-C-alkylene-bridged ribonucleosides and their evaluation as inhibitors of HCV NS5B polymerase
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The synthesis of 2′-O,4′-C-methylene-bridged bicyclic guanine ribonucleosides bearing 2′-C-methyl or 5′-C-methyl modifications is described. Key to the successful installation of the methyl functionality in both cases was the use of a one-pot oxidation-Grignard procedure to avoid formation of the respective unreactive hydrates prior to alkylation. The 2′-C-methyl- and 5′-C-methyl-modified bicyclic guanosines were evaluated, along with the known uracil-, cytosine-, adenine-, guanine-LNA and guanine-ENA nucleosides, as potential antiviral agents and found to be inactive in the hepatitis C virus (HCV) cell-based replicon assay. Examination of the corresponding nucleoside triphosphates, however, against the purified HCV NS5B polymerase indicated that LNA-G and 2′-C-methyl-LNA-G are potent inhibitors of both 1b wild type and S282T mutant enzymes in vitro. Activity was further demonstrated for the LNA-G-triphosphate against HCV NS5B polymerase genotypes 1a, 2a, 3a and 4a. A phosphorylation by-pass prodrug strategy may be required to promote anti-HCV activity in the replicon assay.
- Chapron, Christopher,Glen, Rebecca,La Colla, Massimiliano,Mayes, Benjamin A.,McCarville, Joseph F.,Moore, Stephen,Moussa, Adel,Sarkar, Ruhul,Seifer, Maria,Serra, Ilaria,Stewart, Alistair
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supporting information
p. 2699 - 2702
(2014/06/09)
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- Chemoenzymatic convergent synthesis of 2'-o,4'-c-methyleneribonucleosides
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Novozyme-435-catalyzed efficient regioselective acetylation of one of the two diastereotopic hydroxymethyl functions in 3-O-benzyl-4-C-hydroxymethyl-1,2- O-isopropylidene-α-d-ribofuranose has been achieved. The enzymatic methodology has been successfully
- Sharma, Vivek K.,Kumar, Manish,Olsen, Carl E.,Prasad, Ashok K.
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supporting information
p. 6336 - 6341
(2014/07/21)
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- IMPROVED SYNTHESIS OF ?2.2.1|BICYCLO NUCLEOSIDES
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A synthesis of [2.2.1]bicyclo nucleosides which is shorter and provides higher overall yields proceeds via the key intermediate of the general formula III, wherein R4 and R5 are, for instance, sulfonates and R7 is, for instance, a halogen or an acetate. F
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Page/Page column 17; 34; 38
(2008/06/13)
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