Elimination in Furanuronate Derivatives

On treatment of the terminally oxidized polynucleotides (ribo or 2 -de-oxyribo) with alkali, the / -eliminative cleavage of the pentofuranuronate residue was observed, resulting in the mononucleoside unit (144) having the characteristic 3,4-unsaturated 3-deoxypentofuranuronate residue. In addition, a shortened polynucleotide chain (145) was obtained, in 

The alkali-catalyzed, )8-eliminative degradation of model compounds was examined by Todd and coworkers,starting, for example, from uridine, adenosine, guanosine, and thymidine, and their 3 -phosphates. These investigations led to the conclusion that 8-eliminative degradation is not a quantitative reaction important proportions of by-products are formed, and hence, in its present form, this method does not seem to have any practical significance. 

Vizsolyi and Tener have reported a modified method of / -eliminative degradation in which the pentofuranuronate conjugates obtained by selective oxidation with platinum and hydrogen peroxide were converted into the propylamides. The degradation products were isolated by treatment of the pentofuranuronamides with dilute alkali-metal hydroxide at 100°. 

The isopropylidene acetal group was used as the leaving group in the conversion of 9-(methyl 2,3-0-isopropylidene- 8-D-ribofuranosyluronate)- 

The common feature in the enolacetal-forming, yS-elimination reactions on pentose conjugates just outlined is that the initiator of elimination, namely, the proton on C-4, is activated by a carboxyl group. 

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