Synthesis and In Vitro Antitumor Activity of New Isoxazolo[5,4‐d]Pyrimidine Systems

Abstract

The reaction of 5‐amino‐3‐methylisoxazole (1) with aldimines 2, 3, 4, 5, 6, 7 gave basic side chain 5‐amino‐3‐methylisoxazole derivatives 8, 9, 10, 11, 12, 13. Annulations of derivatives 8, 9, 10, 11, 12, 13 with anisaldehyde afforded the target isoxazolo[5,4‐d]pyrimidines 14, 15, 16, 17. Treatment of 1 with isatin ketimine anil 18 resulted in the formation of derivative 19, which further cyclized with anisaldehyde afforded the spirotetracyclic system 20. Mannich reaction of 1 with primary amine such as methylamine and benzylamine gave the corresponding isoxazolo[5,4‐d]pyrimidine derivatives 21 and 22, respectively. The newly synthesized compounds were tested for their antitumor activity.