Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
J Am Chem Soc. 2012 Jul 18;134(28):11781-90. doi: 10.1021/ja304554e. Epub 2012 Jul 3.
Elatenyne is a small dibrominated natural product first isolated from Laurencia elata. The structure of elatenyne was originally assigned as a pyrano[3,2-b]pyran on the basis of NMR methods. Total synthesis of the originally proposed pyrano[3,2-b]pyran structure of elatenyne led to the gross structure of the natural product being reassigned as a 2,2'-bifuranyl. The full stereostructure of this highly flexible small molecule was subsequently predicted by Boltzmann-weighted DFT calculations of (13)C NMR chemical shifts for all 32 potential diastereomers, with the predicted structure being in accord with the proposed biogenesis outlined below. Herein we report two complementary total syntheses of elatenyne, which confirm the computer-predicted stereostructure. Additionally, the total syntheses of (E)-elatenyne and a related 2,2'-bifuranyl, laurendecumenyne B, are reported. This work has not only allowed the full structure determination of all of these natural products but also provides excellent supporting evidence for their proposed biogenesis. The total synthesis of elatenyne demonstrates that DFT calculations of (13)C NMR chemical shifts coupled with biosynthetic postulates, comprise a very useful method for distinguishing among large numbers of highly flexible, closely related molecules.
埃拉亭炔是一种从小的二溴化天然产物首次从海巴戟中分离得到。埃拉亭炔的结构最初根据 NMR 方法被分配为吡喃并[3,2-b]吡喃。埃拉亭炔最初提出的吡喃并[3,2-b]吡喃结构的全合成导致天然产物的总结构被重新分配为 2,2'-双呋喃基。随后，通过对所有 32 个潜在非对映异构体的（13）C NMR 化学位移进行 Boltzmann 加权 DFT 计算，预测了这个高度灵活的小分子的全立体结构，预测结构与下面概述的生物合成一致。在此，我们报告了埃拉亭炔的两种互补全合成，这证实了计算机预测的立体结构。此外，还报道了（E）-埃拉亭炔和相关的 2,2'-双呋喃基，laurendecumenyne B 的全合成。这项工作不仅允许对所有这些天然产物进行完整的结构测定，而且还为它们的生物合成提供了极好的支持证据。埃拉亭炔的全合成证明，（13）C NMR 化学位移的 DFT 计算与生物合成假设相结合，构成了一种非常有用的方法，可以区分大量高度灵活、密切相关的分子。
