105-20-4

Histalog,Lilly,US,1953

ChEBI: Pyrazole in which a hydrogen adjacent to one of the nitrogen atoms is substituted by a 2-aminoethyl group. It is a histamine H2-receptor agonist used clinically to test gastric secretory function.

A solution of 55 grams (1.1 mol) of hydrazine hydrate in 100 ml of methanol was cooled in a water bath and stirred while a solution of 48 grams (0.50 mol) of pure γ-pyrone in 100 ml of methanol was added over a period of about 15 minutes. After the addition was complete, the solution was allowed to stand at room temperature for about 1 hour, and was placed in a 1 liter hydrogenation bomb. 25 ml of liquid ammonia were added cautiously with stirring, followed by about 15 cc of Raney nickel catalyst. The bomb was charged with hydrogen to 1,800 pounds pressure, heated to 90°C and agitated. The quantity of hydrogen required to convert the hydrazone into the desired aminoethylpyrazole was taken up in about 3 hours. The bomb was cooled and opened, and the contents filtered. The filtrate was evaporated under reduced pressure to remove the methanol and the residual liquid was distilled under reduced pressure, whereby there were obtained 44.5 grams (81% yield) of 3-β-aminoethylpyrazole boiling at 118°-123°C at a pressure of 0.5 mm of Hg.

Histalog (Lilly).

Diagnostic aid (gastric secretion)