Halo- and Deoxy-nucleosides

2 -[ Br]-2 -Bromo-2-deoxy-uridine has been prepared either from 2,2 -anhydro-uridine using radio labelled ammonium bromide or by irradiation of unlabelled 

Reagents i, Dihydrofuran-H ii, HjS-py iii, Raney Ni iv, NaH-CFjSOjCl v, BU4NF vi, HOAc-HjO 

Using preformed 3-halo-3-deoxy-D-xylofuranose acetates, the series of 3 -halo-3 -deoxy-cytosine derivatives (44) have been prepared, together with the corresponding xylo-nucleoside derivatives (44, X = OMs or OTs), which were used in anti-leukaemic studies in comparison with Ara C.  

Reagents i, Me,C(0Me),-Me,C0-MeOH-CuS04-H,S04 ii, Ac,0-py Hi, Av iv, C F3SOj S iMej-2,4-bistrimethylsilyloxy-5 -fluoropyrimidine 

The synthesis of a series of 2 -fluoro-5-substituted arabinofuran-osyl-cytosines and -uracils has been described. 5-Methyluracil and 5-iodocytosine derivatives were the most effective against herpes simplex virus. The arabino configuration was essential for antibiotic activity, and corresponding chloro and bromo analogues were less effective.5 -Bromo-, 5 -fluoro-, and 5 -iodo-deriv-atives of 5-fluorouracil have been prepared conventionally. The a-anomer of 5 -fluoro-5 -deoxyuridine has been synthesized from a 1,2-oxazoline derivative of 5-deoxy-5-fluoro-D-ribose, in turn prepared by a sulphonate displacement using pyridinium fluoride. Treatment of 1-(o-D-arabinofuranosyl)-uracil with diphenylcarbonate yielded the 1,4-oxazin derivative (23) which yielded the 2 -chloro-2 -deoxy-arabino-a-nucleoside (24) on chlorination this was then reduced to the 2 -deoxy analogue (25). 5-Fluorouridine has been 

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 

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