Cytidine 5 -bromo

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... 

This leaves positions (3 ), (4 ), and (S ) as possible points for the union. However, position (S ) is excluded because bromine reacts with uridine to give S -bromo-uridine, and nitric acid gives a 6 -nitro derivative which, on hydrolysis, yields S -nitro-uracil. Position (4 ) is excluded because treatment of bromo-uridine with phenylhydrazine gives 4 -S -diphenylhydrazino-uridine. Hence in both uridine and cytidine the ribose residue is situated at position (3 ) of the base. This conclusion has been verified by indirect methods. ... 

Deoxycytidylate deaminase was first isolated from sea urchin e s by Scarano and has since been demonstrated in many animal tissues the deaminases from spleen and chick embryo have been partly purified (23, 24). The enzyme requires that the substrate must be a 4-aminopyrimidine deoxyribonucleoside 5 -monophosphate, and will accept the following substituents at the pyrimidine 5-position methyl, hydroxymethyl, fluoro, iodo, and bromo. Notably, the following are not deaminated cytidine, deoxycytidine, eytidylate, dCDP, and dCTP. The concentration of this enzyme in cells appears to be related to their proliferative state in that the enzyme is found in growing tissues, but activities are low in adult tissues such as liver. 

Nucleosides and their Analogues and Derivatives Thereof.- l-(3, 5 -Di-0-benzoyl-r-C-allyl-P-D-arabino-furanosyl)uraciI 69, 3-P-D-ribofuranosyl-6,7-dihydro-9H-thiazolo(3,2-a]purin-9-onc 70,and sodium 5-bromo-cytidine-5 -phosphate. The X-ray structure of 3-methyl-7-deazainosine (71) showed a conformation fixed anti about the glycosidic bond. 2 3 -Dideoxy-3 -methylamino-ribosylthymine (ddT(3 NHMe)), P-5-isopropyl-2 -deoxyuridine, 5-... 

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. 

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). ... 

The sialic acid-cytidine conjugate 83 has been synthesized, the units being linked by displacement of a 5 -bromo-substituent on the nucleoside by a 2-thio-sialyl nucleophile. ... 

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