An efficient synthesis of partially protected .alpha.-D-ribofuranosides from D-ribose by way of a unique selective debenzylation reaction

Synthesis of carbohydrate building blocksviaregioselective uniform protection/deprotection strategies

“…The earlier examples of regioselective de-0-benzylation include that of perbenzylated methyl lyxoside by Grignard reagent, 100 and perbenzylated methyl ribofuranoside with tin tetrachloride. 101 The selective heterogeneous catalytic transfer hydrogenolysis perbenzylated 1,6-anhydrohexoses catalyzed by palladium on charcoal was developed by Martin-Lomas. 102 1,6-Anhydro-2,3,4-tri- O -benzyl-β-D-mannopyranose 61 was treated with 10% Pd/C in refluxing 2-propanol for 4 h, to produce 1,6-anhydro-3- O -benzoyl-β-D-mannopyranose 62 in 40% yield (Scheme 12).…”

2′‐Deoxy‐2′‐α‐C‐(hydroxymethyl)adenosine as Potential anti‐HCV Agent

“…Methyl 3,5-di-O-(4-chlorobenzyl)-α-d-ribofuranoside (10) was prepared according to the method of Martin et al [17] d-Ribose was first fixed in its 1-OMe furanose form. Selective protection of positions 3 and 5 with a p-chlorobenzyl group was realized by selective deprotection of position 2 of compound 9 by reaction with tin(IV) chloride.…”

“…The solvent plays an important role in the radical reaction. Indeed, the desired 2Ј-deoxy-2Ј-α-C-styryl-3Ј,5Ј-O-(1,1,3,3-tetraisopropyldisiloxan-1,3-diyl)adenosine (17) was obtained in dry benzene but not in dry toluene. As reported by De Mesmaeker et al, [22] the radical reaction (modified BartonMcCombie reaction) led to a stereoselective introduction of a 2-phenylethenyl group at the α-side of the sugar ring because of the steric hindrance due to the presence of the base at the anomeric position on the β face.…”

Synthesis and properties of triplex-forming oligonucleotides containing 2′-O-(2-methoxyethyl)-5-(3-aminoprop-1-ynyl)-uridine

“…Synthesis of 1-O-methyl-3,5-di-O-benzyl-a-D-ribofuranoside 1-O-Methyl-3,5-di-O-benzyl-a-D-ribofuranoside (4) was prepared by minor modifications to the published methods (Scheme 1). 17,18 Firstly, D-ribose was reacted with anhydrous MeOH in the presence of Dowex-50 H + resin to produce 1-methyl-D-ribofuranoside 2 in quantitative yield. Benzylation of 2 with benzyl bromide in the presence of NaH gave the protected glycoside 3 (91% yield for two steps).…”