The determination of stereochemistry of organic molecules still represents one of the major obstacles in the structure elucidation procedure in drug discovery. Although the application of residual dipolar couplings (RDCs) has revolutionized this field, residual chemical shift anisotropies (RCSAs) which contain valuable structural information for nonprotonated carbons, have only been scarcely employed so far. In this study, we present a simple but highly effective solution to extract RCSAs of the analytes in a liquid crystalline phase formed by AAKLVFF oligopeptides. This method does not require any special instruments, devices or correction during post-acquisition data analysis, and thus can be easily applied in any chemistry laboratory. To illustrate the potential of this method, the relative configurations of four known natural products (1-4) belonging to different structural classes were confirmed. Moreover, we unambiguously elucidated the stereochemistry of spiroepicoccin A (5), a rare thiodiketopiperazine marine natural product whose configuration could not be assigned based on conventional NMR methods.

中文翻译：

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从液晶相中残留的化学位移各向异性对天然产物的立体化学阐明

有机分子立体化学的测定仍然是药物发现中结构解析过程中的主要障碍之一。尽管残余偶极耦合 (RDC) 的应用彻底改变了该领域，但迄今为止，几乎没有使用包含非质子化碳的有价值结构信息的残余化学位移各向异性 (RCSA)。在本研究中，我们提出了一种简单但高效的解决方案，用于提取 AAKLVFF 寡肽形成的液晶相中分析物的 RCSA。这种方法在采集后的数据分析过程中不需要任何特殊的仪器、设备或校正，因此可以很容易地应用于任何化学实验室。为了说明这种方法的潜力，确认了属于不同结构类别的四种已知天然产物 (1-4) 的相对构型。此外，我们明确阐明了螺皮球菌素 A (5) 的立体化学，这是一种稀有的硫代二酮哌嗪海洋天然产物，其构型无法根据常规 NMR 方法进行分配。