2’-deoxy-5’,8-cyclonucleosides

In a similar way, 5-O-acetylthymidine was converted into the 3-deoxy-3-iodo derivative 72 in 55% yield. In this case, the replacement of the hydroxyl group by iodine was presumed to have taken place by retention of the configuration at C-3. The first intermediate in the reaction was proposed to be the phosphonate (70) which rapidly collapses to an O-3-cyclonucleoside (71) and the latter is subsequently attacked by iodide ion to give the product 72. It was also observed (106) that treatment of nucleosides containing a cis vicinal diol grouping such as 5-0-acetyluridine with triphenylphosphite methiodide failed to provide iodinated products but gave phosphonate derivatives instead. 

Synthesis of 2 -Deoxy-2 -oc-fluoro Pyrimidine Nucleosides via Cleavage of Cyclonucleosides... 

The synthesis of 2 -deoxy-2 -a-fluoro purine nucleosides via cleavage of purine O-cyclo-nucleosides (see Scheme 7.2) has not been reported, presumably for the following reasons [18] (i) the synthesis of purine O-cyclonucleosides is not so easy as that of pyrimidine O-cyclonucleosides (ii) the glycosyl bond of purine nucleosides is rather unstable under severe reaction conditions such as the use of HF and (iii) it is not easy to remove the... 

Ikehara, M. and Imura, J. (1981) Studies on nucleosides and nucleotides. LXXXVII. Purine cyclonucleosides. XLII. Synthesis of 2 -deoxy-2 -fluoroguanosine. Chem. Pharm. Bull., 29, 1034-1038. 

A soln. of 6-amino-9-(2,3-0-isopropylidene-5-deoxy- -D-eAyr/zr<7-pent-4-enofurano-syl)purine in dry chloroform cooled, stirred, and treated dropwise at 10° with a soln. of bromine in the same solvent, and allowed to stand 12 hrs. at 0° -> 5 -bromo-5 -deoxy-2, 3 -0-isopropylidene-N3- -cycloadenosine bromide. Y 89%. -This is the first reported N3- -4 -furanose cyclonucleoside. J. R. McCarthy, Jr., R. K. and M. J. Robins, Am. Soc. 90, 4993 (1968). 

NudeosideSy Nucleotides, and their Derivatives.—3, 5 -Di-0-acetyluridine/ 5-0-acetyl-l -(2-deoxy-a-D-cryt/iro-pentofuranosyl)uracil/° 2-thiouridine, 4-deoxy-3-deazauridine/° S-nitrouridine, 2, 3 -C -isopropylideneuridine, 2, 3 -0-(S)-methoxymethyleneuridme, ° the cyclonucleosides (653 R = H and Me), 0 3 2 -0-acetyluridine 3, 5 -(benzyl phosphate)/ (uridine 5 -phos-phate)(2,2 -dipyridylamine)copper(ii). ... 

Syntheses of the 2, 3 -0-isopropylidene-8,5 ( S)-cycloderivatives of adenosine and guanosine have been achieved by selenium dioxide oxidation of the 5 -deoxy-8,5 -cyclonucleosides to give the 5 -oxo compounds, followed by stereoselective reduction with sodium borohydride. The 8,5 -(R) series was obtained by inversion of the (5) isomer via the 5 -mesyloxy derivative. Hydrolytic deamination of the adenosine derivatives gave the inosine counterparts. Their c.d. spectra reflected the chirality at the 5 -position. ... 

Carbocyclic analogues of 2 -azido- and 2 -amino-2 -deoxyuridine (58) have been made from the known carbocyclic uridine via the 2,2 -cyclonucleoside.ii i The carbocyclic analogue of 2 -deoxy-2 -fluoro-ara-G (59)... 

Reduction (tributyltin hydride) of 7V -dibenzoyl-5 -deoxy-5 -iodo-2, 3 -0-iso-propylideneadenosine afforded the carbon-bonded cyclonucleoside (399) and its... 

M. Ikehara, A. Hasegawa, J. Imura, Studies of nucleosides and nucleotides LXXXV. Purine cyclonucleosides 41. A new synthesis of 2 -deoxy-2-fluoro-adenosine by the use of tetrahydropyranyl protecting group. J. Carbohyd. Nucleosides Nucleotides 7 131 (1980). 

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