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S. M. Hecht, U. Jordis:
"Synthesis of 7-alkylamino-3-methylpyrazolo[4,3-d]pyrimidines";
Patent: USA, No. US 4282361; submitted: 03-16-1978, granted: 08-04-1981.

The title compds., useful as cytokinin antagonists (no data), were prepd. from 3-methyl-4-nitro-5-pyrazolecarboxylic acid (I) in a series of reactions. I was converted to the Et ester, the ester and NH3 gave II (R = NO2), and the latter was reduced in a medium contg. HCO2H to yield II (R = HCONH) (III). III was heated with NaOMe in DMF to give pyrazolopyrimidine deriv. IV (R1 = OH), the product was treated with POCl3, and the IV (R1 = Cl) obtained reacted with Me(CH2)4NH2 to give IV [R1 = NH(CH2)4Me].