Synthesis and Conformational Analysis of 1-[2,4-Dideoxy-4-C-hydroxymethyl-α-l-lyxopyranosyl]thymine

Citations Over Time

Abstract

Previously different types of nucleosides with a six-membered carbohydrate moiety have been evaluated for their potential antiviral and antibiotic properties and as building blocks in nucleic acid synthesis. However, a pyranose nucleoside with a 1,4-substitution pattern like 1-[2,4-dideoxy-4-C-hydroxymethyl-alpha-l-lyxopyranosyl]thymine (4) has not been studied yet. Modeling suggested that this nucleoside would show the (4)C(1) conformation in contrast to anhydrohexitol nucleosides (1) whose most stable conformation is (1)C(4). The key to the synthesis of 4 involves the stereoselective introduction of the hydroxymethyl group onto the C-4 carbon of the pyranose sugar. Attempts to achieve this via hydroboration/oxidation of a C-4'-exocyclic vinylic intermediate selectively yielded the undesired alpha-directed hydroxymethyl group. Therefore, we envisaged another approach in which the C-4 substituent was introduced upon treatment of 2,3-O-isopropylidene-1-O-methyl-4-O-phenoxythiocarbonyl-alpha-l-lyxopyranose with beta-tributylstannyl styrene. This allowed stereoselective beta-directed introduction of a 2-phenylethenyl group at C-4, which was converted via oxidation/reduction (OsO(4), NaIO(4)/NaBH(4)) into the desired 4-hydroxymethyl group (20). The resulting 1-O-methyl-2,3,6-tri-O-acetyl-protected sugar was coupled with silylated thymine, using SnCl(2) as Lewis acid (22). After suitable protection, Barton deoxygenation of the 2'-hydroxyl function of the obtained ribo-nucleoside yielded the desired 2'-deoxynucleoside 4, indeed showing the expected equatorial orientation of the thymine ring ((4)C(1)).

Related Papers

• → Reductive Deoxygenation of Alcohols: Catalytic Methods Beyond Barton–McCombie Deoxygenation(2013)118 cited
• → 1,2-Deoxygenation of vic-Dihydroxyindenoimidazoles: Optimization of a Novel Deoxygenation Reagent(2004)11 cited
• → Decomposition of glucose with in situ deoxygenation in a low H2 pressure environment – Part I: Monometallic catalysts(2018)7 cited
• → Study of new facile deoxygenation methods in cyclodextrin induced room temperature phosphorescence(1997)22 cited
• → Deoxygenation of Alcohols and CC Coupling Reactions(1998)