An unequivocal set of procedures for the synthesis of 4-amino-1,5,6,8-tetrahydropyrido[2,3-d]pyrimidine-2,7-diones (7) and 2-amino-3,5,6,8-tetrahydropyrido[2,3-d]pyrimidine-4,7-diones (8), in a maximum of four steps from an α,β-unsaturated ester 1, is reported. Thus, the acid hydrolysis of the 2,4-diaminopyrido[2,3-d]pyrimidines 3 yields the 4-amino-2-oxopyrido[2,3-d]pyrimidines 7 while the cyclization of the Michael adducts 9 (formed by reaction of 1 and methyl cyanoacetate) with guanidine affords the corresponding 2-amino-4-oxopyrido[2,3-d]pyrimidines 8. Both isomers were also obtained by hydrolysis of the 4-amino-2-bromo- and 2-amino-4-bromo-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones 5 and 6, respectively.
一种无歧义的程序集,用于从α,β-不饱和酯1最多经过四个步骤合成4-氨基-1,5,6,8-四氢吡啶并[2,3-d]嘧啶-2,7-二酮(7)和2-氨基-3,5,6,8-四氢吡啶并[2,3-d]嘧啶-4,7-二酮(8)。因此,2,4-二氨基吡啶并[2,3-d]嘧啶3的酸水解产生4-氨基-2-氧代吡啶并[2,3-d]嘧啶7,而Michael加合物9(由1和氰乙酸甲酯反应形成)与胍嘧啶的环化则得到相应的2-氨基-4-氧代吡啶并[2,3-d]嘧啶8。这两种异构体也可通过4-氨基-2-溴和2-氨基-4-溴-5,6-二氢吡啶并[2,3-d]嘧啶-7(8H)-酮5和6的水解分别获得。