U.S.-Croatia Chemistry Research on Biomimetic Rearrangements in Carbocations

这项由耶鲁大学的Martin Saunders和他的合作伙伴、萨格勒布大学的Olga Kronja合作的美国-克罗地亚研究项目，研究了类固醇和三萜类化合物形成过程中重要的生物途径。研究人员寻求关于碳正离子的物理有机化学的新的基础知识，包括动物中的原甾基阳离子和植物中的达马烯基阳离子。这些将使用实验技术和量子化学计算进行研究。美国-克罗地亚团队打算确定生物合成中自然发生的碳正离子重排所特有的结构特征。为此，研究人员将研究以下模型碳阳离子及其母醇或氯化物：1)叔戊基阳离子，2)2-环烯丙基阳离子的甲基化和氢化衍生物，以及3)在C-1和C-8具有不同烷基的双环[3.2.0]农名的碳正离子衍生物。研究计划包括：(A)模型碳正离子及其同位素标记类似物在非亲核溶液中稳定溶液的核磁共振研究，(B)模型阳离子和天然阳离子本身的量子化学计算，以及(C)模型化合物在水或非极性溶剂中的重排过程的分析。这些结果应该会对与类固醇生物合成中涉及的碳正离子的化学行为相关的结构和重排的细节产生新的见解。如果成功，这可能会对未来旨在合成人工激素的医学研究产生影响。这个化学有机动力学项目通过使美国和中欧的顶尖专家能够在相互感兴趣和能力很强的领域结合互补的人才和汇集资源，实现了促进科学知识的计划目标。

This U.S.-Croatian research project between Martin Saunders of Yale University and his partner, Olga Kronja of the University of Zagreb, examines the biological pathways important in the formation of steroids and triterpenoids. The researchers seek new fundamental knowledge about the physical organic chemistry of carbocations, including protosteryl cation in animals and dammarenyl cation in plants. These are to be investigated using both experimental techniques and quantum chemical calculations.The US-Croatian team intends to determine the structural features specific for rearrangement of naturally occurring carbocation in biosynthesis. To do so the researchers will investigate the following groups of model carbocations and their parent alcohols or chlorides: 1) the tert-amyl cation, 2) the methylated and deuterated derivatives of 2-cyclopenyl-e-propyl cation and 3) the carbocation derivatives of bicyclo[3.2.0]noname with various alkyl groups at C-1 and C-8. The research plan includes: (a) NMR spectroscopic studies on stable solutions of model carbocations and their isotopically labeled analogues in non-nucleophillic solution, (b) quantum chemical calculations with the model cation and natural cations themselves, and (c) analysis of the rearrangement processes of the model compound in aqueous or nonpolar solvents. Results should yield new insight into details of structure and rearrangements related to chemical behavior of the carbocations involved in biosynthesis of steroids. If successful, this may have implications for future medical research designed to synthesize artificial hormones.This project in organic dynamics of chemistry fulfills the program objective of advancing scientific knowledge by enabling leading experts in the United States and Central Europe to combine complementary talents and pool resources in areas of strong mutual interest and competence.