Lancifodilactone G的不对称全合成

Lancifodiilactone G is a novel and complex member of nortriterpenoid which isolated from the leaves and stems of S.lancifolia. The structure represents following features: 1. It shows a distinct octacylic scaffold consist by various connections of 5-, 7- and 8-membered ring, including fused cyclic, spirocyclic and oxo-bridge moieties. 2. The structure contains 12 stereocenters, 6 of which are tetrasubstituted carbons. 3. It contains a novel 7-8-5 all-carbon tricyclic skeleton and a [5,5,5] double-spirocyclic moiety, as well as a special stable enol structure on the 8-member ring, which is unique among reported natural products. 4. The skeleton is highly oxygenated, with function groups like hydroxyl groups, carbonyl groups of ketones and esters, ketals etc., which shows the structure complexity...In our research group’s previous effort on the total synthesis of Schindilactone A, a universal synthetic strategy for this family natural products was developed. Based on this strategy, several key reactions and their combination will be tested to finish the total synthesis of lancifolactone G, so that to achieve the divergent total synthesis of the whole family. This study will provide important information on understanding the biosynthesis pathway of the family.

Lancifodilactone G是从狭叶五味子的茎和叶中分离得到的一种复杂的降三萜类化合物，其结构具有以下特点：1. 整个分子具有8个环系，包含五元环、七元环、八元环等不同大小的环系，以并环、螺环以及氧桥环等多种方式进行连接；2. 结构中含有12个手性中心，其中包含6个四取代手性中心；3. 分子中包含了全新的7-8-5全碳核心骨架和[5,5,5]双螺环结构，更为独特的是分子中八元环上存在稳定的烯醇式结构，是迄今为止唯一报道的具有该结构的天然产物；4. 该分子骨架高度氧化，包含了羟基、酮羰基、酯羰基和双螺缩酮结构，体现了结构单元的复杂多样性。. 本课题组在完成该家族化合物Schindilactone A的过程中发展了一条普适性的路线，我们将在该分子的全合成中尝试通过关键反应的组合，实现该家族天然产物集体合成策略，为研究该家族天然产物的生源合成途径打下基础。

Lancifodilactone G是从狭叶五味子的茎和叶中分离得到的一种复杂的降三萜类 化合物。整个分子具有8个环系,包含五元环、七元环、八元环等不同大小的环系,以并环、 螺环以及氧桥环等多种方式进行连接。分子中含有12个手性中心,其中包含6个四取代手性 中心,并且还有一个罕见的孤立稳定存在的烯醇结构,在合成上具有相当的挑战性。.在本课题组此前发展的针对该家族天然产物的多样性导向合成线路基础上,我们进一步 完善了该策略,并完成了乙酰化Lancifodilactone G的首次全合成。该合成从不对称Diels- Alder反应产物出发,经环丙烷化-扩环反应,烯烃关环复分解(RCM)反应,TMTU促进的 Pauson-Khand反应,选择性的格式加成-烯烃复分解(CM)-酯化反应,Dickman缩合反应 构建了分子核心骨架,最终以27步完成了合成工作。该合成首次实现了具有孤立稳定存在的 烯醇结构的化合物的合成,完善了针对该家族天然产物的多样性导向合成策略。