Condensation of tetramethyl methylenebisphosphonate with 2,3-O-isopropylidene-5-O-trityl-D-ribose gave a mixture of 2,5-anhydro-1-deoxy-1-(diethoxyphosphinyl)-2,3 -O-isopropylidene-5-O-trityl-D-altritol and -allitol. Separation of the isomers and deprotection gave 2,5-anhydro-1-deoxy-1-phosphono-D-altritol and -allitol. The former is the stable isosteric methylenephosphonate analogue of alpha-D-ribose 1-phosphate, the ribose donor in nucleoside phosphorylase catalyzed nucleoside biosynthetic reactions. It did not, however, inhibit purine nucleoside phosphorylase at concentrations of 6 mM.

It has been previously shown by others7 that upon warming related diaza olefins noncharacterizable black materials are generated. Also upon treatment of either 6 or 7 with hydride ion (NaH, xylene, reflux) rapid deg-radation occurs to give a similar black, high-melting solid (H. C. R. Taylor, unpublished results). N-Alkylation reactions of 3-bromopyrazolo[4,3-d]pyrimidin-7-one and 3-bromo-7-chloro-and 3-bromo-7methoxypyrazolo[4,3-d]pyrimidineswere studied. Alkylations in aqueous base yielded predominately N -l alkyl products, as did trimethysilylation using hexamethyldisilazane. In contrast, alkylation with 2-chlorotetrahydropyran and sodiutn hydride in dimethylformamide or with dihydropyran and an acid catalyst in ethyl acetate yielded predominantly N-2 alkyl products. Formation of 3-lithio derivatives of N -l and N-2 alkylated 7-alkoxypyrazolo[4,3-d]pyrimidines from the corresponding 3-bromo compounds was accomplished by treatment with n-butyllithium at low temperatures. N-1 alkyl compounds yield complex mixtures of products, including those of N-dealkylation and rearrangement with rupture of the pyrazole ring. The N-2 alkylated compound, 3-lithio-7-methoxy-2-tetr~ihydropyran-2'-ylpyrazolo[4,3-d]pyrimidine, was stable and reacted with benzaldehyde in high yield.

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Treatment of adenosine cyclic 3′,5′‐phosphate with liquid H2S in aqueous pyridine provided a convenient, one‐step synthesis of 9‐β‐D‐ribofuranosylpurine‐6(1H) thione cyclic 3′,5′‐phosphate.