Synthesis and Biological Activity of Truncated Fluorocyclopentenyl Pyrimidine Nucleosides

Abstract

Carbocyclic nucleoside 합성에 여러 가지로 이용이 가능한 중간체인 cyclopentenone 유도체 (16)는 D-ribose로부터 Ring-closing methasis 반응을 포함한 6단계의 효과적인 반응을 거쳐 높은 수득률로 얻어졌다. fluorocyclopentene ring을 포함한 pyrimidine nucleosides를 합성하기 위해 중간체인 D-cyclopentenone (16)을 시작으로 electrophilic fluorination 이라는 주된 반응 과정을 거쳐 D-fluorocyclopentenone 유도체 (21)을 합성하게 되었다. 이 후, Mitsunobu 반응을 하여 잠재적으로 부작용이 적은 항암제로 기대되는 pyrimidine base를 condensation하여 최종 목표인 truncated fluorocyclopentenyl cytosine (9)를 합성하였다. 다음 목표 물질인 truncated fluorocyclopentenyl cytosine (10)을 합성하기 위하여, 합성된 uracil derivative (9)에 acetlyation을 시킨 물질 (26)을 1,2,4-triazole, phosphous oxychloride, triethylamine과 반응시켰다. 하지만 최종 목표 물질 (10)이 되기까지의 총 수득률이 3 %에 그치고 말았다. 이 문제를 해결하기 위해 다른 합성 방법을 모색하던 중, 2',3'-O-isopropyl protect된 uracil derivative pyrimidine (23)으로부터 직접 cytosine conversion을 시도하게 되었다. 물질 23을 pyridine 존재 하에 1,2,4-triazole과 4-chlorophenyldichlorophosphate과 반응시키는 등, 총 3단계의 반응을 거쳐 총 수득률 28 %라는 높은 수율로 최종 목표 물질인 cytosine derivative nucleoside (10)을 합성할 수 있었다. 이는 전 과정에 비해 반응 단계도 짧고 수득률도 높아진 결과라 할 수 있다. 이렇게 합성된 물질들로 human lung cancer cell line A549, human fibro sarcoma cell line HT1080, human stomach cancer cell line SNU-638, human leukemia cell line K562, human colon cancer cell line HCT116에 대한 항암 효과를 시험하게 되었다. 결과, 100μM의 농도에도 불구하고 특별한 암세포 억제효과를 보여주는 물질을 찾을 수 없었다. 그리고 E.coli. JM 109 containing the plasmid pPROKcd20 균주를 통해서 본 SAH hydrolase 억제 시험 결과, uracil derivative nucleoside (9)만이 미약한 효과를 보였다. 이 결과로부터, fluorocyclopentenyl pyrimidine이 viral replication에 관여하기 위해서는 cellular kinase에 의한 4'-hydroxy methyl group의 인산화가 매우 중요함을 알 수 있었다.;Highly efficient and practical methodology for the synthesis of D-cyclopentenone derivative (16) has been developed via a ring-closing metathesis reaction from D-ribose in 6 steps. Novel pyrimidine nucleosides with fluorocyclopentene ring were synthesized from D-cyclopentenone via electrophilic fluorination as a key step. The utility of D-fluorocyclopentenone derivative (21) is demonstrated by their application for the synthesis of various truncated fluorocyclopentenyl pyrimidine nucleosides using Mitsunobu reaction as a key step. Truncated fluorocyclopentenyl pyrimidine nucleosides might be served as a potent anti-tumor agent with less toxicity. Towards this, Mitsunobu condensation between fluorocyclopentenone derivative (21) and N³-benzoyl-uracil gave fluorocyclopentenone uracil derivative (9), which was converted to cytosine derivative (10) by a conventional method. Treatment of the acetylated derivative (26) with 1,2,4-triazole in presence of phosphous oxychloride, and triethylamine followed by mild ammonolysis gave truncated fluorocyclopentenyl cytosine (10) in 3 % overall yield. In order to overcome this low yield problem, we slightly modified the synthetic route. Treatment of the 2',3'-O-isopropyl protected derivative (23) with 1,2,4-triazole, 4-chlorophenyldichlorophosphate in pyridine followed by mild ammonolysis gave cytosine derivative (10) in 28 % overall yield (3 steps from 23), which is much more improved in view of overall yield and the number of steps, in comparison with previous procedure. Synthesized compounds were evaluated as potential anti-tumor agents against human lung cancer, human fibro sarcoma, human stomach cancer, human leukemia, human colon cancer. However, they did not show any significant inhibitory activity against broad range of cell growth up to 100 μM. Surprisingly, only uracil derivative (9) exhibited moderate anti-SAH hydrolase activity. From this study, we can conclude that 4'-hydroxymethyl group of fluorocyclopentenyl pyrimidine nucleoside played an important role in phosphorylation by cellular kinase.