First Total Synthesis of the Benzotropolone/Bis(pulvinone) Natural Product Aurantricholone Exploiting New Strategies for Establishing Benzotropolones and Z-Configured Pulvinones

Aurantricholone as well as its calcium and lithium salts, all of which represent the coloring principle of the fungus Tricholoma aurantium, were synthesized for the first time, namely in 15 steps, 10 of which were our longest linear sequence. We developed an access to benzotropolones after dibromocyclopropanating alkyl or silyl enol ethers of 1-tetralones. Successive treatments with DMAP-N-oxide and Ac₂O effected ring-enlargement, oxidation, and acetylation. O-acetyl-1-bromo-3,4-dimethoxybenzotropolone obtained thereby – similarly as unsubstituted benzotropolone – was brominated at C-8 in two steps by adopting our recently published bromination protocol for otherwise unsubstituted O-acetylbenzotropolone. Thereafter, a double and doubly Z-selective Suzuki-coupling with a newly introduced boronate established the O-methylated pulvinone moiety as well as the O-methylated “pulvinone-like” motif of what altogether equaled the completed aurantricholone scaffold. Its deprotection (two steps) furnished the title compound either as its protonated form or its calcium or lithium salt.     

天然产物 Gymnothecaoxazoles A的全合成

以2,3-二羟基苯甲酸为起始原料,通过酯化、Williams、水解、酰胺化、Robinson-Gabriel环化、脱保护等一系列反应成功合成了gymnothecaoxazoles A,总收率为20.0%,其结构经~1H NMR、~(13)C NMR和HRMS确证。此方法原料廉价易得,反应条件温和,操作简单,为快速制备gymnothecaoxazoles A提供了参考。     

Synthesis of 1-alkylselenocyclobutene via intermediate allenyl selenoketene

Reactions of 2-alkynyl arylethynyl selenide 1 with alkyl iodides 3 in the presence of lithium aluminium hydride via allenyl selenoketene 2 afforded cyclobutene 4. Allenyl group of the intermediate allenyl selenoketene 2 was monitored by React IR.     

Total Synthesis and Structure Revision of Halioxepine

The first total synthesis of halioxepine is accomplished using a 1,4-addition for constructing the quaternary center at C10 and a halo etherification for the generation of the tertiary ether at C7. The correct structure of halioxepine was determined by assembling different enantiomeric building blocks and by changing the relative configuration between C10 and C15.     

Synthesis and Structure Revision of Dichrocephones A and B

Herein, we report the first enantioselective synthesis of dichrocephones A and B, which are cytotoxic triquinane sesquiterpenes with a dense array of stereogenic centers within a strained polycyclic environment. Key features include the application of a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Double reductive ring cleavage yielded the proposed structure of dichrocephone A. Mismatched spectroscopic data for our synthetic material compared to the natural isolate led us to revise the previously proposed configuration based on biosynthetic considerations and NMR calculations. Implementation of these findings culminated in the synthesis of dichrocephones A and B.     

天然产物Luxenchalcone的全合成

以对羟基苯甲醛和2,4-二羟基苯乙酮为起始原料,经过甲氧甲基化、溴代、Ullmann反应、羟醛缩合和脱保护等反应,完成了天然产物双查尔酮Luxenchalcone的全合成,关键步骤为Ullmann反应,重要中间体和目标产物的化学结构经 ¹H NMR,¹³C NMR和ESI-MS等表征确认.     

A simple and efficient synthesis of 2-alkylazulenes

The annulation method based on 2H-cyclohepta[b]furan-2-ones was applied for the synthesis of 2-alkylazulenes; 2-R-azulene (R = Et, i-Pr, n-Pr, i-Bu). Tropolone p-toluenesulfonate was used as a starting compound. By the two step synthesis, 1-carboxylic-3-cyanoazulene derivatives were obtained. Treatment of 1-carboxylic-3-cyanoazulene derivatives with aq H₂SO₄ resulted in decarboxylation and elimination of cyano group to give 2-alkylazulenes in good yields.     

Synthesis of Optically Active trans-2-Aminocyclopropanecarboxylic Esters

The research on optical alicyclic β-amino acids has recently attracted increasingly attention due to their significant pharmacological properties endowed by rigid frameworks, stable conformation1. Numerous biologically active peptides, β-lactams and some other natural products2 contain optical alicyclic β-amino acids. Cyclopropyl-modified alanines have been proved to be useful intermediates in medicine synthesis because of their rigid framework and reactive functional groups (amino and carb…     

Stereoselective Halogenation in Natural Product Synthesis

At last count, nearly 5000 halogenated natural products have been discovered. In approximately half of these compounds, the carbon atom to which the halogen is bound is sp³‐hybridized; therefore, there are an enormous number of natural products for which stereocontrolled halogenation must be a critical component of any synthesis strategy. In this Review, we critically discuss the methods and strategies used for stereoselective introduction of halogen atoms in the context of natural product synthesis. Using the successes of the past, we also attempt to identify gaps in our synthesis technology that would aid the synthesis of halogenated natural products, as well as existing methods that have not yet seen application in complex molecule synthesis. The chemistry described herein demonstrates yet again how natural products continue to provide the inspiration for critical advances in chemical synthesis.     

Strained Alkenes in Natural Product Synthesis

Strained molecules continue to challenge the ingenuity of chemists as their high‐energy bonds serve as fuel for the promotion of complex synthetic transformations. Developments in this area have resulted in the recent emergence of strained alkenes as intermediates in natural product synthesis. This Minireview highlights these recent advances along with current developments toward understanding the unique reactivity of strained alkenes.     

Synthesis of Natural Product Inspired Compound Collections

Mimicking nature synthetically : The successful development of multistep stereoselective syntheses gives access to natural product inspired compound collections having carbo‐, oxa‐,and azacyclic scaffold structures which promise to provide sources for new reagents in medicinal chemistry and chemical biology research.

     

天然产物骆驼宁碱A及其衍生物的合成研究进展

骆驼宁碱A是从骆驼蒿中分离出来的喹唑啉酮类生物碱, 骆驼蒿在中国民间用来治疗风湿病、炎症、脓肿及其他疾病. 由于骆驼宁碱A的药理活性, 有关其合成方法受到了关注. 综述了该化合物的合成方法, 根据闭环方式的不同把合成方法分为六大类, 大部分方法都围绕中间体喹啉吡咯烷酮的合成, 一般步骤较长, 产率过低, 虽然有的路线步骤短, 产率高, 但原料不易得到. 因此, 经济的产业化方法还有待进一步研究.     

Synthesis and Structure of trans-1,2-Bisaromatic Heterocycle Substituted Cyclopropanes

Trans-1,2-bis(2'-(5 '-phenyl-1 ',3',4'-oxadiazolyl)) cyclopropane (BDCP) and its eleven substituted novel derivatives were synthesized. Besides four derivatives of l,2-bis(2'-(5'-phenyl-l ' , 3 ' , 4 ' -ox-adiazo1yl))ethane (BPDS) were also synthesized as model compounds. The crystal structure of ethyl BDCP was determined and the cyclopropane ring was found to be able to transmit conjugation between the aromatic groups directly bonding with it by studying the ultraviolet and fluorescent spectra of the above compounds.     

Concise Large-Scale Synthesis of Tomatidine,A Potent Antibiotic Natural Product

Tomatidine has recently generated a lot of interest amongst the pharmacology, medicine, and biology fields of study, especially for its newfound activity as an antibiotic agent capable of targeting multiple strains of bacteria. In the light of its low natural abundance and high cost, an efficient and scalable multi-gram synthesis of tomatidine has been developed. This synthesis uses a Suzuki–Miyaura-type coupling reaction as a key step to graft an enantiopure F-ring side chain to the steroidal scaffold of the natural product, which was accessible from low-cost and commercially available diosgenin. A Lewis acid-mediated spiroketal opening followed by an azide substitution and reduction sequence is employed to generate the spiroaminoketal motif of the natural product. Overall, this synthesis produced 5.2 g in a single pass in 15 total steps and 15.2% yield using a methodology that is atom economical, scalable, and requires no flash chromatography purifications.     

First Total Synthesis,Structure Revision,and Natural History of the Smallest Cytochalasin: (+)‐Periconiasin G

The total synthesis of the smallest cytochalasin isolated so far, periconiasin G, which bears a seven‐membered ring in lieu of the usual macrocycle, has been performed from both enantiomers of citronellal, relying on an intramolecular Diels–Alder reaction in favor of the natural endo stereochemistry. We show that, among the four synthesized stereoisomers, including the exo isomers, the one matching the NMR data of the natural product was not that assigned in the original report, imposing structure revision. The natural product, previously isolated from a plant‐mutualistic fungus, was biologically investigated taking into account its natural history, showing significant effects against the phytopathogenic fungus Botrytis cinerea and thus opening new opportunities in combating this pest.     

Total Synthesis of the Antimitotic Marine Natural Product (+)-Curacin A

The structurally novel antimitotic agent curacin A was prepared in 15 steps and in 2.6% yield for the longest linear sequence. Key steps in our synthesis are the use of a hydrozirconation-transmetalation protocol for the preparation of divinyl alcohol 8, the stereoselective formation of the acyclic triene segment 11 via enol triflate chemistry, and a second hydrozirconation of the conjugated triene followed by an isocyanide insertion. For the preparation of the heterocyclic moiety of curacin A, the oxazoline --> thiazoline conversion offered an efficient access to the sensitive marine natural product.     

天然产物色胺酮及其衍生物的仿生合成

以药用植物体内存在的生物合成前体吲哚醌和邻氨基苯甲酸为反应物,用POCl3作催化剂,仿生合成了天然产物色胺酮(1),结构表征结果与标准品一致.该反应所用原料易得,避免了使用较昂贵的靛红酸酐,适合实验室小规模简便合成.采用此方法合成了14个色胺酮衍生物,可见其具有广泛的适应性.