7a, R'= H; R2= Me; R3= H b, R'= Me; R2= H; R3= Et c, R'= Me; Itz= H; R3= 4-MeOC, H4 gave 6a in rather poor yield due to formation of 2-cyanopropanamide as a major byproduct. Being unsubstituted in the 3-position, 5a readily underwent ring opening to the nitrile and proved quite vulnerable to acid. The stability of the isoxazole nucleus was markedly enhanced by incorporation into the sulfamide 6a. Hydrogenation of 6a in DMF over Raney nickel ...
