The changing faces of halogenated marine natural products:: Total synthesis of the reported structures of elatenyne and an enyne from Laurencia majuscula
The changing faces of halogenated marine natural products:: Total synthesis of the reported structures of elatenyne and an enyne from Laurencia majuscula
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DOI：
10.1002/anie.200602211
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Burton, Jonathan W.
中科院分区：
文献类型：
--
作者：
Sheldrake, Helen M.;Jamieson, Craig;Burton, Jonathan W.
复杂的天然产物的结构最好通过独立合成或X射线结晶学来确认。在过去的20年里，核磁共振光谱学的进步极大地提高了复杂分子结构的易解性；然而，在不可能进行结晶学的情况下，区域和立体控制的合成仍然是结构确认的最佳方法。在许多情况下，通过杂原子确定连接性成为核磁共振波谱结构分配中的一个重大挑战，特别是在其他密切相关的分子中。例如，考虑两个天然产物(E)-dactomelyne(1)和notoryne(2).[1，2]它们都含有相同的碳和质子连接性，因此仅基于核磁共振实验进行明确的结构分配将是具有挑战性的。天然产物1和2属于从红藻和以劳伦西亚为食的海洋生物中分离出来的更广泛的C15代谢物。[3]1986年，二溴天然产物elatenyne被Hall和Reiss分离，并在广泛的1H和13C核磁共振分析的基础上被命名为吡喃[3，2-b]吡喃结构3。[4]最近，从大黑藻中分离的卤化C15天然产物的结构被揭示为吡喃[3，2-b]吡喃4，再次，在广泛的核磁共振波谱分析的基础上，通过与结构3(报道为elatenyne)和(E)-dactomelyne(1)的比较，Elatenyne和L.Majuscula enyne是吸引人的全合成目标，因为它们具有密集的官能化的吡喃[3，2-b]吡喃核心和嵌入的C2对称性。[6，7]在这里，我们报道了这些卤代次级代谢产物的有效的双向路线，它迅速建立了中心吡喃[3，2-b]吡喃核心并最终完成了结构3和4的全合成。[8，9]合成的吡喃[3，2-b]吡喃的光谱数据2-b]吡喃3和4与已报道的天然产物不一致，我们认为这两个天然产物在结构上都与诺托林2有关，因为它们具有核心的2，2‘-联苯并呋喃结构。
The structures of complex natural products are best confirmed by independent synthesis or X-ray crystallography. Advances in NMR spectroscopy over the last 20 years have greatly improved the ease with which the structures of complex molecules are solved; however, in cases where crystallography is not possible, regio-and stereocontrolled synthesis remains the best method for structure confirmation. In many cases, determining the connectivity through heteroatoms becomes a significant challenge in structure assignment by NMR spectroscopy, especially in otherwise closely related molecules. For example, consider the two natural products (E)-dactomelyne (1) and notoryne (2).[1, 2] They both contain the same carbon and proton connectivity, and hence unambiguous structure assignment would be challenging on the basis of NMR experiments alone. The natural products 1 and2 belong to a much wider group of C15 metabolites isolated from red algae and from marine organisms that feed on Laurencia species.[3] In 1986, the dibrominated natural product elatenyne was isolated by Hall and Reiss, and was assigned the pyrano [3, 2-b] pyran structure 3 on the basis of extensive 1H and 13C NMR spectroscopic analyses.[4] More recently, the structure of a halogenated C15 natural product isolated from L. majuscula was disclosed as the pyrano [3, 2-b] pyran 4, again on the basis of extensive NMR spectroscopic analyses and by comparison with the structures 3 (reported for elatenyne) and (E)-dactomelyne (1).[5] Elatenyne and the L. majuscula enyne were attractive targets for total synthesis because of their densely functionalized pyrano [3, 2-b] pyran cores and embedded C2 symmetry.[6, 7] Herein, we report an efficient two-directional route to these halogenated secondary metabolites which rapidly established the central pyrano [3, 2-b] pyran core and culminated in the total synthesis of structures 3 and 4.[8, 9] The spectroscopic data for the synthetic pyrano [3, 2-b] pyrans 3 and 4 are inconsistent with those reported for the natural products, and we propose that both natural products are structurally related to notoryne 2 by having a core 2, 2’-bifuranyl structure.