Garsubellin A 是一种能够增强胆碱乙酰转移酶的类萜,人们认为胆碱乙酰转移酶水平的降低在阿尔茨海默病的症状中发挥着重要作用。由于潜在有用的生物活性以及新颖的桥连和稠合环状分子结构,加苏贝林 A 引起了人们的广泛合成兴趣,但其绝对立体结构尚未确定。我们在这里报告了 (+)-garsubellin A 的第一个对映选择性全合成。我们的合成依赖于环己酮框架的立体选择性形成和 1,2-乙二硫醇的双共轭加成,促进羟醛环化以构建双环 [3.3.1] 骨架。十二步无保护基合成路线使得天然 (-)-garsubellin A 及其非天然 (+)-对映体的合成能够用于生物学评价。
The stereoselective total synthesis of garsubellin A is described. The total synthesis was achieved through the stereoselective construction of a bicyclo[3.3.1]nonane derivative via a three-step sequence: intramolecular cyclopropanation, formation of a germinal dimethyl group, and regioselective ring opening of cyclopropane. To complete the total synthesis of garsubellin A, chemo- and stereoselective
The first total synthesis of garsubellin A, a neurotrophic compound with potent choline acetyltransferase-inducing activity, is described. Keys for success were (1) stereoselective intermolecular aldol reaction at the C-4 position with acetaldehyde, (2) stereoelective Claisen rearrangement to introduce an allyl group to the most sterically crowded position at C-6, (3) ring-closing metathesis to construct the B-ring, and (4) Wacker-type oxidative C-ring formation. This synthetic route can be extended to an asymmetric synthesis of garsubellin A using the Koga catalytic enantioselective alkylation, which produced enantioenriched alpha-prenyl cyclohexenone with excellent enantioselectivity (95% ee).
Total Synthesis of Garsubellin A
作者:Dionicio R. Siegel、Samuel J. Danishefsky
DOI:10.1021/ja057418n
日期:2006.2.1
A concise approach to the laboratory synthesis of garsubellin A is described. Garsubellin A, an effective inducer of choline acetyltransferase (ChAT), has been shown to have potential as a therapeutic agent for the treatment of Alzheimer's disease. Starting from 3,5-dimethoxyphenol, the synthesis has provided garsubellin A in an 18-step sequence. Notable transformations include dearomative allylation, diastereoselective vinylogous lactonization, iodocarbocyclization, transannular Wurtz, and bridgehead functionalization reactions.