Molecular Function of Naturally Occurring Anti-microtubule Agent Phenylahistin (Determination of Structural Components Necessary for the Anti-microtubule activity t and Molecular Design for Drugs)

紫杉烷类和长春花生物碱是临床上常用的抗微管药物，但经过长期治疗后，肿瘤通常会对这些化合物产生耐药性。因此，开发用于临床肿瘤学的新型抗微管药物具有重要的意义。作为候选药物之一，我们将重点放在真菌产物苯基组蛋白（phenylahitin， PLH）上，它属于一类新的肽型秋水仙碱样微管结合剂，对多种肿瘤细胞系具有细胞毒性活性。（-）- phenylahitin(-)-1是一种二酮哌嗪衍生物，由l -苯丙氨酸和咪唑环5位上具有季碳的独特异丙烯化脱氢组氨酸残基组成。为了在二酮哌嗪衍生物的基础上开发更有效的抗肿瘤药物，我们研究了(-)-1抗微管活性所需的结构成分，并进行了1的全合成，建立了其衍生物的合成路线。从合成的PLH衍生物的生物学评价中，我们发现一个刚性的平面伪三环结构和咪唑环5位的宝石二甲基结构的存在是引发强细胞毒活性的重要因素。利用已建立的合成路线，我们合成了(-)-1的几个衍生物，其在咪唑环5位的取代基被不同的烷基链修饰，以确定这部分对生物活性的影响。从衍生物的评价来看，在这个位置上存在宝石二甲基结构对于引起更高的细胞毒活性是重要的。利用该合成方法进一步衍生(-)-1，将有助于更好地了解苯基组化蛋白的构效关系，并开发基于二酮哌嗪结构的更有效的抗肿瘤药物。

Taxanes and the vinca alkaloids are routinely used as the anti-microtubule agents in the clinic, however after long-term treatment, tumors typically become resistant to these compounds. Hence, there is a significant interest in the development of novel anti-microtubule agents for use in clinical oncology. As one of such candidates, we are focusing on a fungal product, phenylahistin (PLH), which belongs to a new class of peptidic colchicine-like microtubule-binding agents that exhibits cytotoxic activity against a wide variety of tumor cell lines. (-)-Phenylahistin (-)-1, a diketopiperazine derivative, consists of L-phenylalanine and a unique isoprenylated dehydrohistidine residue with a quaternary carbon at the 5-position of the imidazole ring. To develop more potent anti-tumor agents based on this diketopiperazine derivative, we investigated to elucidate the structural components necessary for the anti-microtubule activity of (-)-1, then performed the total synthesis of 1 for establish the synthetic route of its derivatives as well. From the biological evaluation of synthetic PLH derivatives, we found that a rigid and planar pseudo-tricyclic structure and the existence of the gem-dimethyl structure at the 5-position of the imidazole ring are important factors to elicit the potent cytotoxic activity. By utilizing this established synthetic route, we synthesized several derivatives of (-)-1, whose substituent at the 5-position of the imidazole ring was modified with different alkyl chains, to determine the effect of this moiety on the biological activity. From the evaluation of derivatives, it is suggested that the existence of the gem-dimethyl structure at this position is important to elicit higher cytotoxic activity.Further derivatization of (-)-1 using the developed synthetic method will contribute to a better understanding on the structure-activity relationship of phenylahistin and to develop more potent antitumor agents based on the diketopiperazine structure.