Karlotoxin 2 (KmTx2) is a marine natural product isolated from the dinoflagellate Karlodinium veneficum. The absolute configuration of KmTx2 was determined by NMR analysis in combination with degradation of the natural product, and the absolute configuration at C49 was revised by computational analysis. On the other hand, we reported revision of the absolute configuration of amphidinol 3 (AM3), whose structure is similar to that of KmTx2, by comparing NMR data of the synthesized partial structures and total synthesis of AM3. In this paper, we report the synthesis of the partial structures of KmTx2 corresponding to the C30−C63 section, and the diastereomer at C37, C41−C43, and C45−C49, which is hypothetically proposed on the basis of the revised structure of AM3. Comparison of the NMR data of the synthetic specimens with those of the natural product suggested that the absolute configuration of KmTx2 is revised to be 37R, 41R, 42R, 43R, 45R, 46R, 47R, 48S, and 49S.

中文翻译：

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Karlotoxin 2 C30-C63区段的合成和立体化学

Karlotoxin 2（KmTx2）是从甲藻中分离的天然海洋产物Karlodinium veneficum。通过NMR分析结合天然产物的降解来确定KmTx2的绝对构型，并且通过计算分析来修正C49处的绝对构型。另一方面，通过比较合成的部分结构的NMR数据和AM3的全部合成，我们报道了其结构与KmTx2相似的两性酚3（AM3）的绝对构型的修订。在本文中，我们报告了KmTx2对应于C30-C63部分的部分结构以及C37，C41-C43和C45-C49处的非对映异构体的合成，这是根据AM3的修订结构提出的。合成样品的NMR数据与天然产物的NMR数据比较表明，KmTx2的绝对构型修改为37 R，41 - [R，42 - [R 43 - [R 45 - [R，46 - [R，47 - [R，48小号和49小号。