Deoxy ribofuranose

The crystal structures of the important ribofuranoses or 2-deoxy-ribofuranoses have not been determined, since these forms are in the minority with respect to the pyranoses in solution. There are numerous examples, however, in the crystal structures of the nucleosides and nucleotides. Those that contain the ribofuranose moieties quite commonly display vicinal 0(2 )H 0(3 ) or O(30H 0(2 ) intramolecular hydrogen bonding as the minor component of a three-center bond. This type of hydrogen bonding is described in Part IB, Chapter 9. 

There have been many reports of syntheses of deoxy nucleosides by standard sugar-base condensation reactions. These include 5 -deoxy-ribo nucleosides and 5 -mono- or 5",5-di-deuterated analogues, as well as derivatives of 5-deoxy-D-xylose and 5-deoxy-D-glucose, 5-alkylated thymidine derivatives, 2 -deoxy-6-methyl-5-azacytidine and its a-anomer, the thymidine analogue 4-(2-deoxy-B-D-erythro-pento-furanosyl)-6-methyl-l,2,4-triazine 3(HH)-one-1-oxide, 6-aza-3-deaza analogues of 2 -deoxy-cytidine and 2 -deoxyuridine,3 -deoxycytidine from a 3-deoxy-ribofuranose obtained from a fermentation broth producing the 3 -deoxy nucleoside antibiotic, cordycepin, 4-deoxy-DL-threo-pentopyranosyl pyrimidine nucleosides, and 5 -C-methyluridines derived from 6-deoxy-D-allose and 6-deoxy-D-talose. A range... 

The most important derivatives of pyrimidines and purines are nucleosides Nucleosides are N glycosides m which a pyrimidine or purine nitrogen is bonded to the anomeric carbon of a carbohydrate The nucleosides listed m Table 28 2 are the mam building blocks of nucleic acids In RNA the carbohydrate component is d ribofuranose m DNA It IS 2 deoxy d ribofuranose... 

Of the four possible 5-deoxy-pent-4-enofuranoses, the D-erythro-isomer was of interest as a potential source of derivatives of L-lyxofuranose. For this purpose, a vinyl ether having the D-en/ hro-configuration has been prepared from derivatives of D-ribose. Condensation of D-ribose with acetone in the presence of methanol, cupric sulfate and sulfuric acid at 30°C., as described by Levene and Stiller(30) afforded a sirupy product consisting mainly of methyl 2,3-O-isopropylidene-D-ribofuranose (40). Treatment of a pyridine solution of the sirup with tosyl chloride... 

Deoxy-5 -fluoroadenosine (911) and the analogs 910, 912, 913 were prepared by coupling of 5-deoxy-5-fluoro-D-ribofuranose and 6-chloro-purine. 2, 5 -Dideoxy-5 -fluoroadenosine (914) was prepared through a displacement reaction of the corresponding 5 -0-tosyl precursor with fluoride (BU4NF in DMF). The carbocyclic nucleosides 915 and 916 have been prepared and their antiviral activities evaluated. 

C19H24BrN09S 5-0-(p-Bromophenylsulfonyl)-3-deoxy-3-C-(R)-(ethox-ycarbonylformamido)methyl-l,2-0-isopropylidene-a-D-ribofuranose (BDEIRF)284... 

Preparation of 5-(3-benzoylpropionyl)-3-deoxy-3-diisopropoxyphosphinylmethyl-l,2-di-0-acetyl-D-ribofuranose — Reaction of an alkyl bromide in a carbohydrate series with triisopropyl phosphite... 

A solution of 5-0-(3-benzoylpropionyl)-3-deoxy-3-bromomethyl-l,2-di-O-acetyl-D-ribofuranose (2.35 g, 4.89 mmol) in triisopropyl phosphite (17 g, 81 mmol) was heated at 160 to 180°C with exclusion of moisture for 72 h. Volatile materials were removed under reduced pressure, and the residue was purified by chromatography on a silica gel column (48 x 2.7 cm) eluting with chloroform ethyl acetate (1 1). From the 150 to 500 ml eluent, there was isolated the pure 5-(3-benzoylpropionyl)-3-deoxy-3-diisopropoxyphosphinylmethyl-l,2-di-O-acetyl-D-ribofuranose (1.73 g, 68%) as an oil that exhibited IR and NMR spectra and analyses in accord with the proposed structure. 

A stereochemical dependence has been observed for the 5/f,h-i values observed for a number of 3-deoxy-3-C-(fluoromethylene)-l,2 5,6-di-0-isopropylidene-a-D-ribofuranose derivatives n. =... 

The conformational properties of furanose rings have received considerable attention in recent years because of the impact these properties may have in mediating biological processes . Most notable in this respect are the p-D-ribofuranose 1 and 2-deoxy-p-D-erythro-pentose 2 (Scheme 1) components of ribo- (RNA) and deoxyribonucleic (DNA) acids. It is well known that the furanose ring adopts specific shapes depending on its local structural environment in a biopolymer. For example, in tRNA, the... 

Figure 6. (a) a-D-Ribofuranose oxyanion (b) 2-deoxy-a-n-ribofuranose oxyanion... 

D-Ribofuranose-type phospha sugars 50 (R=OH, Et, and Ph) and 2-deoxy-D-ribofuranose analogues 51 (R=OH and Me) in Fig. 3 have been prepared via longer reaction pathways by a similar ring closing intramolecular addition reaction of a P - H group to an aldehyde of sugars shown in Scheme 14 [17-20]. 

In 1970, 1 was prepared by direct glycosylation of the silylated 5-azacytosine with acylated 1-halo sugars, but the yields were very low.20 In this procedure, 1,3,5-tri-O-acetyl-2-deoxy-D-ribofuranose (9) was converted into 3,5-di-0-acetyl-2-deoxy-D-ribofuranosyl chloride (10).21 The trimethylsilyl derivative of 5-azacytosine (11),22 prepared from 4-amino-6-pyrimidine by treatment with hexamethyldisilazane, was then allowed to react with intermediate 10 in acetonitrile over 7 days to give a mixture of anomers of l-(3,5-di-(9-acetyl-2-deoxy-D-ribofuranosyl)-5-azacytosine (12) in 10% overall yield. The anomeric mixture was treated with ethanolic ammonia to remove the acetyl groups. The resulting a and p anomers were separated by a combination of fractional crystallization and preparative layer chromatography on silica gel to give pure decitabine (1) and its a-anomer 13 in 7% and 52% yield, respectively. 

Neufellner, E. et al. A Novel Access to Derivatives of 3-Azido-3-deoxy-4a-carba-a-DL-ribofuranose, Potential Intermediates for the Synthesis of Carbachryscandin and Carbapuromycin. 2.4 1998 [158]... 

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