Studies of Nucleosides and Nucleotides. LVII. Purine Cyclonucleosides. (20). Synthesis and Reactions of 8, 5'-S-Cycloadenosine Derivatives

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Starting from 2', 3'-isopropylidene-8, 5'-anhydro-8-mercaptoinosine (II), synthesized from the corresponding adenosine derivative (I) by deamination with sodium nitrite, various 6-substituted analogs were synthesized. Compound (II) was converted to 6-chloropurine derivative (III) by the reaction with POCl₃ and tri-n-butylamine at refluxing temperature in 75% yield. Compound (III) was allowed to react either with methylamine, dimethylamine or sodium methylmercaptide to give N⁶-methyl (IV), N⁶-dimethyl (IX) and 6-methylmercapto (X) derivatives, respectively. Ultraviolet spectrum, circular dichroism and mass spectra of these compounds are listed. Compound (IV) was alternatively obtained by a Dimroth type rearrangement of N¹-methyl derivative of I by heating in sodium hydroxide solution at pH 8-9. The same type of rearrangement occured also with unprotected 1-methyladenosine-8, 5'-S-cyclonucleoside to give compound (VIII).