5-Bromo-deoxy-cytidine

Crystallographic analyses of nucleosides and their derivatives have revealed that the values of Q)CN for the vast majority of these compounds correspond to the anti conformation The exceptions observed to date which possess the syn conformation are 3, 5 -cyclic guanosine (when it is in a crystalline complex with 5-bromo-2 -deoxy-cytidine), the nucleoside antibiotic formycin , 8-bromoguanosine and 8-bromoadenosine Solution measurements, based on NMR, circular dichroism and optical rotatory dispersion are generally in agreement with the X-ray data, (see paper of Ts o et al and literature cited thereii however, studies using Nuclear Overhauser NMR suggest that AMP may also prefer the syn conformation. 

In contrast to uridine,389 cytidine does not yield a 5 -chloro-5 -deoxy derivative on reaction with N,N-dimethyl(chlorometh-animinium) chloride instead 2,2 -anhydrocytidine is formed.395 However, thionyl chloride or bromide in hexamethylphosphor-amide at room temperature achieves this selective replacement of the primary hydroxyl group of halogen in cytidine, and also in adenosine, in respective yields of 80 and 75% for the chloro compounds, and 55 and 30% for the bromo analogs.396... 

D-lyxopyranosyl nucleosides with hydrogen halides to give the 3 -bromo- or 3 -chloro-3 -deoxy-nucleosides (406), or a mixture of the 2 - and 3 -fluoro-deoxy-nucleosides (407). 9-(3-Deoxy-3-iodo-)3-D-xylofuranosyl)hypoxanthine has been synthesized and converted into 3 -amino-3 -deoxy- and 3, 4 -unsatu-rated nucleosides as shown in Scheme 138. Both l-(2-deoxy-2-fluoro- and 2-chloro-2-deoxy-j8-D-arabinofuranosyl)cytidine have been prepared from the corresponding halogeno-sugar derivatives by standard methods (see Schemes 43 and 46). ... 

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