backbone is based on a ring-closing metathesisreaction of diyne 21 catalyzed by Mo[N(t-Bu)(Ar)](3) (5; Ar = 3,5-dimethylphenyl) activated in situ by CH(2)Cl(2), followed by Lindlar reduction of the resulting cycloalkyne 22. The two beta-glycosidic linkages of compound 21 were installed by means of the glucal epoxide method and a modified Koenigs-Knorr reaction promoted by AgOTf/lutidine, respectively
已经实现了微生物生物表面活性剂槐糖脂的主要成分的第一全合成。这种方法在26个成员的脂质链中跨过槐糖骨架的脂族链中包含Z构烯基的大环内酯1,是基于Mo [N(t-Bu)(Ar)]催化的二炔21的闭环易位反应。 (3)(5; Ar = 3,5-二甲基苯基)被CH(2)Cl(2)原位活化,然后Lindlar还原得到的环炔22。化合物21的两个β-糖苷键通过AgOTf /二甲基吡啶促进了葡糖环氧方法的改进和改进的Koenigs-Knorr反应。
Convergent synthesis of the ABCDE ring system of ciguatoxin CTX3C
Ciguatoxin CTX3C is a representative congener of the ciguatoxins, which are known to be the principal causative-agents of ciguatera seafood poisoning. The structure of CTX3C spans over three nanometers and is characterized by thirteen ether rings. To attain a practical construction of this molecule, efficient supplies of the structural fragments are crucial. Herein we report the convergent synthesis of the ABCDE ring fragment featuring (i) alkylative coupling of the AB ring and E ring, and (ii) ring-closing olefin metathesis. (C) 2002 Elsevier Science Ltd. All rights reserved.
Ciguatoxins, the causative toxins of ciguatera seafood poisoning, are large ladder-like polycyclic ethers, and known to have more than 20 structurally distinct congeners. In this paper, we describe a new concise synthesis of the two E-ring structures, of different ring sizes, found in ciguatoxins. From the common oxepane intermediate, the seven-membered E-ring was prepared in three steps, and the eight-membered E-ring was synthesized in seven steps using ring expansion and olefin isomerization as key reactions.
“Boomerang” Strategy in Carbohydrate Chemistry: Diastereoselective Synthesis of <i>C</i>-Glycosylated Benzothiazoles from <i>ortho</i>-Isocyanophenyl Thioglycosides