Wallichanol类天然产物ABC环系合成研究

Wallichanol是一类具有独特桥环结构的二萜天然产物.以2-甲基-1,3-环己二酮作为起始原料,通过高立体选择性的Diels-Alder反应和金催化的炔烃碳环化反应构建Wallichanol的ABC三环核心骨架,共七步路线,总收率为42%.该合成工作为Wallichanol类天然产物全合成奠定了研究基础.     

Enantioselective synthesis of saframycin A and evaluation of antitumor activity relative to ecteinascidin/saframycin hybrids

[formula: see text] A short synthesis of saframycin A is described which begins with a readily available intermediate previously utilized for the total synthesis of ecteinascidin 743. A key step in this synthesis is the use of 1-fluoro-3,5-dichloropyridinium triflate to oxidize a phenolic ring to a 1,4-benzoquinone unit while simultaneously cleaving a methoxymethyl ether of a different phenolic ring to the corresponding phenol (4-->5). The common intermediate (2) for the synthesis of saframycin A (1) and ecteinascidin 743 also allowed the synthesis of two hybrids of these structures (6 and 7). Whole cell bioassays for antitumor activity using lung, colon, melanoma, and prostate-derived tumor cell lines allowed a clear correlation of structure with biological activity in this series.     

Total synthesis of (+)-frondosin A. Application of the Ru-catalyzed [5+2] cycloaddition

The first total synthesis of (+)-frondosin A was accomplished in 19 longest linear and 21 total steps from commercially available materials. The key features of the synthesis include a Ru-catalyzed [5+2] cycloaddition, a Claisen rearrangement, and a ring expansion to construct the core of the frondosin A in a diastereoselective and regioselective fashion. This is the first application of a Ru-catalyzed [5+2] cycloaddition in the total synthesis of a natural product. Through this synthesis, the absolute configuration of (+)-frondosin A was established.     

Core structure of eremophilanes and bakkanes through niobium catalyzed Diels-Alder reaction: synthesis of (+/-)-bakkenolide A

A suitable intermediate for the synthesis of eremophilanes and bakkanes was prepared by a highly regioselective and stereoselective one-step synthesis through a niobium catalyzed Diels-Alder reaction. As a demonstration of the versatility of this intermediate, a total synthesis of (+/-)-bakkenolide A is described.     

Synthesis of eudistomin C and E: improved preparation of the indole unit

An improved synthesis of the indole unit, a key intermediate for eudistomin C, was established utilizing Makosza's indole synthesis. A concise total synthesis of eudistomin E was achieved on the basis of the improved synthesis.     

Synthesis of maremycins A and D1 via cycloaddition of a nitrone with (E)-3-ethylidene-1-methylindolin-2-one

A concise synthesis of maremycins A and D1 has been accomplished via cycloaddition of a chiral cyclic nitrone with ( E)-3-ethylidene-1-methylindolin-2-one as a key step. This synthesis clarifies the stereochemistry of the maremycins and is suitable for large-scale synthesis for biological screening.     

Total Synthesis and Biological Evaluation of the Glycosylated Macrocyclic Antibiotic Mangrolide A

The macrocyclic antibiotic mangrolide A has been described to exhibit potent activity against a number of clinically important Gram‐negative pathogens. Reported is the first enantioselective total synthesis of mangrolide A and derivatives. Salient features of this synthesis include a highly convergent macrocycle preparation, stereoselective synthesis of the disaccharide moiety, and two β‐selective glycosylations. The synthesis of mangrolide A and its analogues enabled the re‐examination of its activity against bacterial pathogens, and only minimal activity was observed.     

Total synthesis of bafilomycin A1

A convergent synthesis of bafilomycin A(1), a potent inhibitor of V-type ATPases, is presented. The synthesis relies on the zinc triflate mediated diastereoselective addition of a complex enyne to a sensitive aldehyde as the key fragment coupling. A ruthenium-catalyzed trans-reduction of the resulting propargylic enyne efficiently installs the required C10-C13 trans,trans-diene subunit, implementing an alternative strategy to traditional palladium-catalyzed cross-coupling strategies. A highly selective oxidation of a secondary hydroxyl group in a triol sets the stage for the completion of the synthesis.     

Regioselective preparation of 2-substituted 3,4-diaryl pyrroles: a concise total synthesis of ningalin B

Methylisocyanoacetate undergoes a 2 + 3 cycloaddition with alpha,beta-unsaturated nitriles to provide a regioselective synthesis of 2-substituted 3,4-diaryl pyrroles. The ease of preparation of alpha,beta-unsaturated nitriles allows the rapid synthesis of pyrroles with varied substituents. Using this method, a key intermediate (1) for the synthesis of the marine natural products lukianol A, lamellarin O, and lamellarin Q was prepared in two steps. A total synthesis of ningalin B (11) was also accomplished utilizing this methodology.     

Concise total synthesis of (-)-spongotine A

The first asymmetric total synthesis of spongotine A is described. The oxidative synthesis of the imidazoline/ketone unit from keto aldehyde and diamine is a key step in this synthesis. The absolute stereochemistry of the asymmetric center of natural spongotine A is revealed as the (S)-configuration.     

A metalation strategy for the construction of functionalized naphthalenes: the first synthesis of guieranone A

The first synthesis of the natural product guieranone A is described, demonstrating a one-pot procedure for the synthesis of protected-1,3,6,8-tetraoxygenated naphthalenes and a subsequent directed metalation synthesis of 2-keto naphthalenes.     

Total synthesis of (−)-Englerin A

A novel and efficient total synthesis of Englerin A is reported. The synthesis featured an intramolecular olefin metathesis ring closure reaction and a highly stereoselective oxygen bridge formation induced by an iodonium ion. This strategy can be used for the synthesis of natural products Englerin A and Englerin B and can provide flexibility in the preparation of various 9-substituted analogues of Englerin A for further structure–activity relationship studies.     

The Total Synthesis of the Anti-Coccidial Agents Ws-5995

A total synthesis of the three anti-coccidial agents WS-5995 A, B, and C by a Diels-Alder route is described. An intramolecular lactonization involving the displacement of a chlorine atom on a naphthoquinone was the key step in the synthesis of A.     

Total synthesis of natural (−)- and unnatural (+)-Melearoride A

This communication details the first total synthesis of the 13-membered macrolide, (?)-Melearoride A, as well as unnatural (+)-Melearoride A. The synthesis features a concise 13 step synthesis (11 steps longest linear sequence) that offers flexible stereo-control and multiple opportunities for unnatural analog synthesis to delve into antifungal SAR. The route features a cuprate addition, an Evans asymmetric alkylation, and a ring-closing metathesis (RCM) to close the 13-membered macrocyclic core.     

Synthetic studies of pseurotin A: preparation of an advanced lactam aldehyde intermediate

An efficient synthesis of the lactam core of pseurotin A has been accomplished. Key features of this synthesis include a tandem oxidation-cyclization to form the lactam from an acetylenic amide precursor. Although coupling of a lactam aldehyde with an appropriate side chain was not effective, it is anticipated that incorporating a partial side chain at an earlier stage should permit completion of the total synthesis of pseurotin A.     

Enantioselective synthesis of the C10-C20 fragment of fusicoccin A

A synthesis of the fully protected C-ring fragment of the tricyclic diterpene fusicoccin A is reported. The desired cyclopentenyl halides 5a,b are obtained in a total of nine steps. Key transformations of the synthesis sequence are a nonconventional Cr-catalyzed allylic oxidation of a protected intermediate cylcopentenone, a diastereoselective addition of a propenyl Grignard/CeCl(3) reagent to the unmasked cyclopentenone, and an asymmetric hydroboration of the isopropenyl substituent. The protected and suitably functionalized C-ring fragment paves the way to explore further the total synthesis of fusicoccin A.     

A total synthesis of millingtonine A

A total synthesis of millingtonine A, a diglycosylated alkaloid, has been accomplished. Millingtonine A possesses a unique racemic tricyclic core structure not known from any other natural or synthetic source until now. The synthesis features a key bond-forming radical Ueno-Stork cyclization to form the heterocyclic core.     

离子热法合成分子筛的研究进展

离子热法是以离子液体或低共熔混合物为介质的一种新型的分子筛合成方法, 它提供了一种离子态的独特合成环境, 为合成新型分子筛及研究分子筛的生成机理提供了机会. 本文综述了离子热法在分子筛合成方面取得的一些进展, 包括合成方法的创新、合成机理的研究、新材料的合成以及新型催化剂的制备等, 并展望了其发展前景.     

Synthesis of the proposed structure of phaeosphaeride A

The first total synthesis of the proposed structure of phaeosphaeride A has been achieved via six-membered-ring formation by means of an intramolecular vinyl-anion aldol reaction as the key step. This synthesis suggests a revised configurational assignment for phaeosphaeride A.     

Concise total synthesis of (+)-brefeldin A: a combined beta-lactone/cross-metathesis-based strategy

[reaction: see text] A highly convergent total synthesis of (+)-brefeldin A that relies on a diastereoselective, beta-lactone-based cyclopentane synthesis combined with complex cross-metathesis reactions is described. The utility of beta-lactones for natural product synthesis and the versatility of cross-metathesis in this context were demonstrated, including the tolerance of an epimerizable aldehyde and a beta-lactone.