Hassan Abdalla E A, Parker William B, Allan Paula W, Secrist John A
Southern Research Institute, Drug Discovery Division, Birmingham, Alabama, USA.
Nucleosides Nucleotides Nucleic Acids. 2009 May;28(5):642-56. doi: 10.1080/15257770903091938.
Metalation of 6-methyl-9-(tetrahydro-2H-pyran-2-yl)purine (10) with lithiating agents of varying basicities such as n-BuLi and LiHMDS in THF at -78 degrees C resulted in metalation at both of the 6-CH(3) moiety and the 8-CH position, irrespective of the molar equivalence of the base. On the other hand, a regioselective metalation at the 6-CH(3) moiety of 10 was observed with NaHMDS or KHMDS, under similar conditions. Treatment of the potassium salts of 10 and of the protected riboside derivative 6-methyl-9-(beta-D-2,3,5-tri-O-tert-butyldimethylsilylribofuranosyl)purine (22) with N-fluorobenzenesulfonamide (NFSI) at -78 degrees C gave the corresponding 6-fluoromethylpurine derivatives 11 and 23, respectively, in good yields. Deprotection of 11 and 23 under standard conditions gave 6-fluoromethylpurine (6-FMeP, 3) and 6-fluoromethyl-9-(beta-D-ribofuranosyl)purine (6-FMePR, 4), respectively, in high yield. Both 3 and 4 demonstrated cytotoxic activity against CCRF-CEM cells in culture. 6-FMePR is a good substrate for E. coli purine nucleoside phosphorylase (E. coli PNP) with a comparable substrate activity to that of the parent nucleoside, 6-methyl-9-(beta-D-ribofuranosyl)purine (6-MePR, 21). The cytotoxic activity of 6-FMeP along with the substrate activity of 6-FMePR with E. coli PNP meet the fundamental requirements for using 6-FMeP as a potential toxin in PNP/prodrug based cancer gene therapy.
在-78℃的四氢呋喃中，用不同碱度的锂化剂（如正丁基锂和双(三甲基硅基)氨基锂）对6-甲基-9-(四氢-2H-吡喃-2-基)嘌呤（10）进行金属化反应，无论碱的摩尔当量如何，都会导致6-CH(3)部分和8-CH位置都发生金属化。另一方面，在类似条件下，用六甲基二硅基氨基钠或六甲基二硅基氨基钾时，观察到10的6-CH(3)部分发生区域选择性金属化。在-78℃下，用N-氟苯磺酰胺（NFSI）处理10的钾盐和受保护的核糖苷衍生物6-甲基-9-(β-D-2,3,5-三-O-叔丁基二甲基硅烷基呋喃核糖基)嘌呤（22），分别以良好的产率得到相应的6-氟甲基嘌呤衍生物11和23。在标准条件下对11和23进行脱保护，分别以高产率得到6-氟甲基嘌呤（6-FMeP，3）和6-氟甲基-9-(β-D-呋喃核糖基)嘌呤（6-FMePR，4）。3和4在培养中均对CCRF-CEM细胞表现出细胞毒性活性。6-FMePR是大肠杆菌嘌呤核苷磷酸化酶（大肠杆菌PNP）的良好底物，其底物活性与母体核苷6-甲基-9-(β-D-呋喃核糖基)嘌呤（6-MePR，21）相当。6-FMeP的细胞毒性活性以及6-FMePR与大肠杆菌PNP的底物活性满足了将6-FMeP用作基于PNP/前药的癌症基因治疗中潜在毒素的基本要求。
