Rosowsky A, Forsch R A, Moran R G
Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
J Med Chem. 1989 Mar;32(3):709-15. doi: 10.1021/jm00123a037.
(6R,6S)-5,8,10-Trideaza-5,6,7,8-tetrahydropteroic acid was synthesized in several steps from 4,4-(ethylenedioxy)-cyclohexanone and [4-(tert-butyloxycarbonyl)benzyl]triphenylphosphonium bromide and was elaborated to (6R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydropteroyl-L-glutamic acid and (6R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydropteroyl-L-ornithin e. Compound 1 was found to be a good substrate for partially purified mouse liver folypolyglutamate synthetase (FPGS), with a Michaelis constant (Km = 15 microM) comparable to that reported for the reduced folate substrate (6S)-5,6,7,8-tetrahydropteroyl-L-glutamic acid and for (6R,6S)-5,10-dideaza-5,6,7,8-tetrahydropteroyl-L-glutamic acid (DDATHF). However, in striking contrast to DDATHF, which is potently cytotoxic, 1 failed to inhibit tumor cell growth in culture at concentrations of up to 100 microM. These results suggested that the NH at position 8 of DDATHF is important for cytotoxic activity but not for polyglutamylation. Just as 1 was a good substrate for FPGS, the ornithine analogue 2 proved to be among the more potent competitive inhibitors of this enzyme discovered to date, with a Ki,s of 10 microM. While the binding affinity of 2 was lower than that reported for 5,6,7,8-tetrahydropteroyl-L-ornithine (H4PteOrn), very substantial FPGS inhibition was observed even though N5,N8, and N10 in H4PteOrn were replaced by carbon. Binding to FPGS thus appears to be tolerant of bioisosteric replacements made simultaneously in ring B and the bridge region. Neither 1 nor 2 was active in preventing cell growth in culture at concentrations of up 100 microM. The N delta-hemiphthaloyl derivative of 2, synthesized as a potential prodrug, was also inactive.
(6R,6S)-5,8,10-三氮杂-5,6,7,8-四氢蝶酸由4,4-(乙二氧基)-环己酮和[4-(叔丁氧羰基)苄基]三苯基溴化鏻经多步合成，并进一步制备得到(6R,6S)-5,8,10-三氮杂-5,6,7,8-四氢蝶酰-L-谷氨酸和(6R,6S)-5,8,10-三氮杂-5,6,7,8-四氢蝶酰-L-鸟氨酸。发现化合物1是部分纯化的小鼠肝脏叶酸多聚谷氨酸合成酶(FPGS)的良好底物，其米氏常数(Km = 15 microM)与报道的还原型叶酸底物(6S)-5,6,7,8-四氢蝶酰-L-谷氨酸和(6R,6S)-5,10-二氮杂-5,6,7,8-四氢蝶酰-L-谷氨酸(DDATHF)相当。然而，与具有强细胞毒性的DDATHF形成鲜明对比的是，在浓度高达100 microM时，1未能抑制培养中的肿瘤细胞生长。这些结果表明，DDATHF第8位的NH对细胞毒性活性很重要，但对多聚谷氨酸化不重要。正如1是FPGS的良好底物一样，鸟氨酸类似物2被证明是迄今为止发现的该酶更强效的竞争性抑制剂之一，其抑制常数Ki,s为10 microM。虽然2的结合亲和力低于报道的5,6,7,8-四氢蝶酰-L-鸟氨酸(H4PteOrn)，但即使H4PteOrn中的N5、N8和N10被碳取代，仍观察到非常显著的FPGS抑制作用。因此，与FPGS的结合似乎能耐受在B环和桥区域同时进行的生物电子等排体替换。在浓度高达100 microM时，1和2均无抑制培养中细胞生长的活性。作为潜在前药合成的2的Nδ-半邻苯二甲酰衍生物也无活性。
