Keitaro Senga

A New, Convenient Synthesis of 2-Alkyl- and 2-Vinylpyrazolo [3,4-d]pyrimidine Derivatives

Treatment of 1,3-dimethyl-6-hydrazinouracil with the appropriate dimethylformamide dialkylacetal afforded the, corresponding 2-alkyl-5,7-dimethylpyrazolo[3,4-d]pyrimidine-4,6-(5H,7H)diones. The reaction of 1,3-dimethyl-6-(α-methylbenzylidenehydrazino)uracils with dimethylformamide dimethylacetal or triethyl orthoformate gave the corresponding 5,7-dimethyl-2-vinylpyrazolo[3,4-d]pyrimidine-4,6(5H,7H)diones, respectively. Similarly, treatment of 1,3-dimethyl-6-(α-methylbenzylidenehydrazino)uraeils with triethyl orthopropionate yielded the corresponding 5,7-dimethyl-3-ethyl-2-vinylpyrazolo[3,4-d]pyrimidine-4,6(5H,7H)diones.

Synthesis of pyrazolo[3,4-d]pyrimidines by intramolecular cycloaddition of azahexatrienes

Treatment of aldehyde pyrimidin-6-ylhydrazones with aromatic aldehydes (or treatment of 6-hydrazinopyrimidines with aromatic aldehydes in excess) in dimethylformamide under reflux gave 2,3-disubstituted pyrazolo[3,4-d]pyrimidines.

A new synthesis of disubstituted 8-aminopurine derivatives

Treatment of 6-amino-5-nitrosopyrimidines with the Vilsmeier reagent (dimethylformamide and phosphorus oxychloride) afforded in general the respective 8-dimethylaminopurines; treatment of 6-amino-4-hydroxy-2-methyl-5-nitrosopyrimidine gave 2-chloromethyl-8-dimethylamino-6-hydroxypurine.

1,3-Dipolar cycloaddition of a thiazolo [5,4-d]pyrimidine 1-oxide to dimethyl acetylenedicarboxylate. New ring transformation to a pyrrolo-[3,2-d]pyrimidine via a pyrimido [4,5-b][1,4]thiazine

1,3-Dipolar cycloaddition of a thiazolo[5,4-d]-pyrimidine 1-oxide to dimethyl acetylenedicarboxylate resulted in the ring transformation of the thiazole moiety to give a pyrrolo [3,2-d] pyrimidine via a pyrimido [4,5-b]thiazine.

Stability of Pulverized Salbutamol Sulfate Tablets.

Content uniformity test of six commercial salbutamol sulfate tablets as well as their stability after pulverization was undertaken, and it was found that Venetlin is the most suitable tablet for the large scale preparation of triturated powders.On the basis of these findings, Venetlin was subjected to pulverization, and was triturated with corn starch to give powders (10mg/g as salbutamol).The studies on content uniformity test, stability, and compatibility on the triturated powders exhibited satisfactory quality for practical use.