ELUCIDATION OF THE PANCRATISTATIN CYTOTOXIC PHARMACOPHORE

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。背景和原理本项目旨在为癌症治疗提供新的治疗剂。从斜纹夜蛾鳞茎中提取的生物碱(+)-泛影抑素具有良好的抗肿瘤和抗病毒活性，目前正在接受美国国家癌症研究所的临床前评估。然而，由于可从隔离中获得的材料数量有限，这项研究已被搁置。S生物碱的有限可获得性也困扰了阐明其作用机制以及结构活性研究的努力，这可能是识别更有效和/或毒性更低的类似物的关键。因此，发现一条高效而灵活的化学路线，不仅可以制备天然产物本身，而且可以制备不同的类似物库，这将极大地促进这种先导化合物的进一步发展，因此它一直是科学界长期追求的目标。方法合成了一系列具有可变截断部分的泛曲他汀类化合物。一旦合成，这些化合物就被评估在体外和体内的抗癌活性。根据获得的合成孔径雷达信息，构建了泛影抑素药效团，并将其用于开发一系列类似物：(A)改善活性/毒性曲线，(B)改善水溶性，(C)简化结构，适合于即将到来的临床试验的大规模生产。结果在INBRE项目的前一年，我们开发了一种高非对映选择性的芳基铜酸盐与α-烷氧基-β-烯酸酯的加成反应，探索了它的应用范围，发现它的潜在应用不仅限于该项目，而且在合成有机化学中具有普遍的实用价值。在这一年里，我们从理论的角度进一步研究了这一方法，并开发了一个新的基于还原消除的模型来预测这些过程的立体化学结果。该模型有望在合成有机铜化学中得到普遍应用。我们应用这种方法构建了一个泛抑素B环类似物的文库，并对这些化合物的抗癌活性进行了评估。这项研究的结论是要求环B的完整性，以保持天然化合物的效力。进一步的研究由于没有发现具有开环B的泛抑素类似物的活性，我们在这方面的进一步努力将集中在C环类似物的合成上。这将通过完全合成和半合成两种方法实现。后者的基础将是分离出泛抑素的同系物那西拉辛，并将其转化为泛影抑素相关结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Background and Rationale This project is aimed at the ultimate goal of providing new therapeutic agents for the treatment of cancer. The alkaloid (+)-pancratistatin, extracted from Pancratium littorale bulbs, displays promising antineoplastic and antiviral activity and is currently undergoing preclinical evaluation by the US National Cancer Institute. However, the studies have been put on hold due to the limited quantity of material available from isolation. The alkaloid¿s limited availability has also plagued efforts towards the elucidation of its mechanism of action as well as structure ¿ activity studies, which could be crucial for the identification of more potent and/or less toxic analogues. Therefore, the discovery of an efficient and flexible chemical route enabling preparation of not only the natural product itself, but also a diverse library of its analogues will tremendously facilitate further development of this lead compound, hence it has been a long-sought objective of the scientific community. Methods This work focuses on a practical synthesis of pancratistatin-based series of compounds with variable truncated portions of the molecule. Once synthesized, the compounds are evaluated for in vitro and in vivo anticancer activity. Based on the obtained SAR information the pancratistatin pharmacophore is constructed and used for the development of a series of analogs with (a) improved activity/toxicity profiles, (b) improved water solubility, and (c) simplified structures, amenable to a large-scale production for the forthcoming clinical trials. Results In the previous year of the INBRE project we developed a highly diastereoselective arylcuprate addition to ?-alkoxy-?,?-enoates, explored its scope and found that its potential applicability is not limited to this project, but rather has a general utility in synthetic organic chemistry. In the current year we further studied this method from a theoretical perspective and developed a novel reductive elimination-based model to predict the stereochemical outcome of such processes. This model is expected to be of general use in synthetic organocuprate chemistry. We applied this method to the construction of a library of pancratistatin ring B analogues and evaluated these compounds for anticancer activity. The conclusion of this study is the requirement for the integrity of ring B to retain the potency of the natural compound. Further Study Since no activity was found with pancratistatin analogues with the open ring B, our further efforts in this area will focus on the synthesis of the ring C analogues. This will be accomplished both through totally synthetic and semisynthetic approaches. The latter will be based on isolation of narciclasine, a congener of pancratistatin, and its conversion to pancratistatin-related structures.