Inosine 2,3-0-isopropylidene-5-0-

Inosine, 2, 3 -0-isopropylidene-dipole moment, 5, 522 [Pg.31]

Phosphorylation of XLVII with phosphorus oxychloride in pyridine solution, followed by hydrolysis to remove the methyl and isopropylidene residues, gave D-ribose 5-phosphate (XLVIII) which, as its barium salt, was found to be identical with the barium salt of the D-ribose phosphate from inosinic acid. By way of further confirmation of the structure of D-ribose 5-phosphate, Levene, Harris and Stiller129 showed that in methanolic hydrogen chloride solution both the natural and synthetic material mutarotated in a manner characteristic of a sugar which can form only a furanoside. 

Levene and Tipson discovered that inosine will condense with acetone in the presence of zinc chloride to give a mono-isopropylidene-inosine, the structure of which was demonstrated as follows. On treatment with p-toluenesulfonyl chloride in pyridine it gives a monotosyl-isopropylidene-inosine which reacts readily with sodium iodide in acetone to give mono-iodo-isopropylidene-inosine, showing that the tosyl group... 

On phosphorylation of isopropylidene-inosine, followed by hydrolysis of the acetone residue, muscle inosinic acid (which, as will be seen later, is definitely known to be 5-phospho-inosine) is formed. This confirms the above formulations for isopropylidene-inosine and inosine. 

Finally, muscle inosinic acid itself was synthesized by Levene and Tipson. This was the first (partial) synthesis of a naturally occurring nucleotide. Phosphorylation of 2,3-isopropylidene-inosine, the structure of which has already been discussed, gave the corresponding 5-phospho derivative, from which the isopropylidene group was cautiously hydrolyzed, yielding 5-phosphoinosine which proved to be identical with muscle inosinic acid. 

Syntheses of the 2, 3 -0-isopropylidene-8,5 ( S)-cycloderivatives of adenosine and guanosine have been achieved by selenium dioxide oxidation of the 5 -deoxy-8,5 -cyclonucleosides to give the 5 -oxo compounds, followed by stereoselective reduction with sodium borohydride. The 8,5 -(R) series was obtained by inversion of the (5) isomer via the 5 -mesyloxy derivative. Hydrolytic deamination of the adenosine derivatives gave the inosine counterparts. Their c.d. spectra reflected the chirality at the 5 -position. ... 

D-Ribose 5-phosphate is a normal metabolite in plants and animals. It was first prepared by acid hydrolysis of inosinic acid or from adenosine 5 -phosphate . It is formed enzymically from ribose and ATP . Synthesis has been carried out by phosphorylating 2,3-isopropylidene-methyl-D-ribofuranoside °. ... 

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