The syntheses of unsubstituted (4), 6-methyl- (6), cis-6,7-dimethyl- (8), cis-2,6,7-trimethyl- (10), cis-6,7-dimethyl-2-thioxo-(1H)- (12) and cis-6,7-dimethyl-2-methylthio- (13) 5,6,7,8- tetrahydropteridin -4(3H)-one and the deuterated derivatives (5), (7), (9) and (14), and a cis and trans mixture of 2-amino-6,7-dimethyl-5,6,7,8- tetrahydropteridin-4(3H)- thione (11) are described. The existence of the transient quinonoid species (15)-(17) had been previously demonstrated by showing that they are substrates for the enzyme dihydropteridine reductase from human brain. We report that the transient quinonoid species cis-2,6,7-trimethyl-(18), cis-2-methylthio-6,7-dimethyl-(25), cis-2-methylamino-6,7-dimethyl-(26), and 2-amino-6,8-dimethyl-(29)7,8-dihydropteridin-4(6H)-one, and 2-amino- 6,7-dimethyl-7,8-dihydropteridin-4(6H)- thione (28), but not cis-6,7- dimethyl-2-thio-7,8-dihydropteridin-4(6H)-one (27) are substrates for this enzyme showing that a variety of substituents in position 2 of the pteridine ring can be tolerated, and confirming that the predominant tautomer (1) of the quinonoid species in aqueous solution is also the reactive tautomer at the active site of this enzyme.
合成了未取代的 (4)、6-甲基- (6)、顺式-6,7-二甲基- (8)、顺式-2,6,7-三甲基- (10)、顺式-6,7-二甲基-2-硫酮-(1H)- (12) 和顺式-6,7-二甲基-2-甲硫基- (13) 5,6,7、8- 四氢蝶啶-4(3H)-酮和氘代衍生物 (5)、(7)、(9) 和 (14),以及 2-氨基-6,7-二甲基-5,6,7,8- 四氢蝶啶-4(3H)-硫酮 (11) 的顺式和反式混合物。瞬时醌类化合物(15)-(17)是人脑中二氢蝶啶还原酶的底物,从而证明了瞬时醌类化合物的存在。我们报告了瞬时醌类化合物顺式-2,6,7-三甲基-(18)、顺式-2-甲硫基-6,7-二甲基-(25)、顺式-2-甲氨基-6,7-二甲基-(26)和 2-氨基-6、8-二甲基-(29)7,8-二氢蝶啶-4(6H)-酮和 2-氨基-6,7-二甲基-7,8-二氢蝶啶-4(6H)-硫酮 (28),但不包括顺式-6,7-二甲基-2-硫-7、8-二氢蝶啶-4(6H)-酮 (27) 是这种酶的底物,这表明蝶啶环第 2 位上的各种取代基都可以被容忍,并证实水溶液中喹啉类物质的主要同分异构体 (1) 也是这种酶活性位点上的活性同分异构体。