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1.
Jiuzhou Guo Bo Li Weihao Ma Mallesham Pitchakuntla Yanxing Jia 《Angewandte Chemie (International ed. in English)》2020,59(35):15195-15198
A practically useful method for the formation of the highly oxygenated bicyclo[3.2.1]octane ring system through Mn(OAc)3‐mediated radical cyclization of alkynyl ketones was developed, which opens up a new avenue for the total synthesis of a number of highly oxidized diterpenoids. Application of this method enabled the first total synthesis of (?)‐glaucocalyxin A. Other salient features of the synthesis include a highly enantioselective conjugate addition/acylation cascade reaction, a Yamamoto aldol reaction, and an intramolecular Diels–Alder reaction to assemble the A/B ring system. 相似文献
2.
Bo Xu Bingyang Wang Wen Xun Fayang G. Qiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5810-5813
A concise and highly stereoselective total synthesis of the Daphniphyllum alkaloids (?)‐daphenylline has been accomplished. The synthesis was started from (S)‐carvone and proceeded via a stereoselective Mg(ClO4)2‐catalyzed intramolecular amide addition cyclization, an intramolecular Diels–Alder reaction to construct the ABCD tetracyclic core architecture, and a Robinson annulation coupled with an oxidative aromatization sequence. Finally, the DF ring system was installed through an intramolecular Friedel–Crafts cyclization. The total synthesis of (?)‐daphenylline is achieved in 19 steps in the longest reaction sequence and in 7.6 % overall yield. 相似文献
3.
Dr. Nina Toelle Dr. Harald Weinstabl Dr. Tanja Gaich Prof. Dr. Johann Mulzer 《Angewandte Chemie (International ed. in English)》2014,53(15):3859-3862
An asymmetric synthesis of the diterpenoid 17‐deoxyprovidencin is described. Key steps include an aldol addition, a base‐catalyzed Wipf‐type furan formation, a Z‐selective ring‐closing metathesis for macrocyclization, a photochemical E/Z isomerization to a highly strained and conformationally restricted ring system, and the stereoselective formation of two epoxides on the ring. 相似文献
4.
Directed Remote Lateral Metalation: Highly Substituted 2‐Naphthols and BINOLs by In Situ Generation of a Directing Group
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Dr. Jignesh J. Patel Dr. Marju Laars Dr. Wei Gan Dr. Johnathan Board Dr. Matthew O. Kitching Prof. Victor Snieckus 《Angewandte Chemie (International ed. in English)》2018,57(30):9425-9429
A general synthesis of highly substituted 2‐naphthols based on a new carbanionic reaction sequence is demonstrated. The reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with either LiNEt2 or LiNiPr2 into Z‐cinnamamides, thus generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation for ring closure to give the aryl 2‐naphthols in good to excellent yields. These transformations can be combined to provide a more efficient one‐pot process. Mechanistic insight into the remote lateral metalation step, demonstrating the requirement of Z‐cinnamamide, is described. Application of this methodology to the synthesis of highly substituted 3,3′‐diaryl BINOL ligands is also reported. 相似文献
5.
Ming Gao Ye‐Cheng Wang Kai‐Rui Yang Dr. Wei He Prof. Dr. Xiao‐Liang Yang Prof. Dr. Zhu‐Jun Yao 《Angewandte Chemie (International ed. in English)》2018,57(40):13313-13318
The first and enantioselective total synthesis of (+)‐plumisclerin A, a novel unique complex cytotoxic marine diterpenoid, has been accomplished. Around the central cyclopentane anchorage, a sequential ring‐formation protocol was adopted to generate the characteristic tricycle[4.3.1.01,5]decane and trans‐fused dihyrdopyran moiety. Scalable enantioselective LaIII‐catalyzed Michael reaction, palladium(0)‐catalyzed carbonylation and SmI2‐mediated radical conjugate addition were successfully applied in the synthesis, affording multiple grams of the complex and rigid B/C/D‐ring system having six continuous stereogenic centers and two all‐carbon quaternary centers. The trans‐fused dihyrdopyran moiety with an exo side‐chain was furnished in final stage through sequential redox transformations from a lactone precursor, which overcome the largish steric strain of the dense multiring system. The reported total synthesis also confirms the absolute chemistries of natural (+)‐plumisclerin A. 相似文献
6.
A highly stereoselective route to the polysubstituted chiral octahydrobenzofuran 12 , a potential synthon for the E‐ring core in the (?)‐reserpine synthesis, is described. The α‐bromo acetal 11 was obtained from inexpensive (?)‐shikimic acid ( 3 ) through a series of highly stereoselective chemical reactions (Scheme). Et3B/Bu3SnH‐Mediated intramolecular radical cyclization of 11 led to compound 12 with the required configuration. 相似文献
7.
Long Min Yang Zhang Xuefeng Liang Junrong Huang Wenli Bao Dr. Chi‐Sing Lee 《Angewandte Chemie (International ed. in English)》2014,53(42):11294-11297
A highly diastereoselective and practical biomimetic total synthesis of (±)‐basiliolide B has been achieved through the study of the two proposed biosynthetic pathways (O‐methylation and O‐acylation) for the unprecedented 7‐methoxy‐4,5‐dihydro‐3H‐oxepin‐2‐one (C ring). The synthesis featured a cyclopropanation/ring opening strategy for establishing the stereogenic centers at C8 and C9, a biomimetic 2‐pyrone Diels–Alder cycloaddition for the synthesis of the ABD ring system, and finally a highly efficient biomimetic intramolecular O‐acylation for the C ring formation. This result provides an important perspective on the biosynthetic origin of the unprecedented 7‐membered acyl ketene acetal moiety of the C ring. 相似文献
8.
Dr. Bernhard Kräutler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(29):9032-9045
The synthesis of cobyrinic acid derivatives by reduction of dehydrocobyrinates is largely unexplored. It is, however, a rational path to B12 analogues that lack specific substituents of the corrin moiety of natural B12 derivatives. The partial syntheses of four epimeric 7‐decarboxymethyl‐cobyrinates is described, which is achieved by reduction of Δ7‐dehydro‐7‐de[carboxymethyl]‐cobyrinate with zinc or with the ‘prebiotic’ reducing agent formic acid. A direct and remarkably efficient route was found to 7‐decarboxymethyl‐cobyrinates, which are cobyrinic acid derivatives in which the c‐side chain at ring B of vitamin B12 is missing. The structures of the hexamethyl‐7‐decarboxymethyl‐cobyrinates were characterized and the stereochemical and conformational properties at their newly saturated ring B were analyzed. The stereochemical outcome of the reduction was found to depend strongly on the reaction conditions. In 7‐decarboxymethyl‐cobyrinates, both peripheral carbon centres of ring B carry a hydrogen atom, and the characteristic quaternary carbon centre at C7 of the cobyrinic acid moiety of vitamin B12 is lacking. The still highly substituted 7‐decarboxymethyl‐cobyrinates are readily dehydrogenated in the presence of dioxygen, furnishing 7‐de[carboxymethyl]‐Δ7‐dehydro‐cobyrinate as the common, unsaturated oxidation product. The noted stability of vitamin B12 and of other CoIII‐cobyrinates in the presence of air is a consequence of their highly substituted corrin macrocycle, a finding of interest in the context of chemical rationalizations of the B12 structure. 相似文献
9.
Oxidant‐Controlled Catalytic Transformations of Phenols with Unexpected Cleavage of Aromatic Rings
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Wei Li Dr. Feijie Song Prof. Dr. Jingsong You 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):13913-13918
Oxidative transformations of phenols have attracted significant attention of chemists due to their importance in biological process and organic synthesis. In contrast to the relatively well‐developed oxygenation and coupling reactions of phenols, the highly efficient and selective oxidative ring cleavage of phenols is under‐represented. This work describes a novel CuCl‐catalyzed tandem homocoupling/skeletal rearrangement of phenols that realizes the cleavage of the phenol ring by using air or Ag2CO3 as the oxidant. Interestingly, simply changing the oxidant to K2S2O8 results in the oxidative coupling/cyclization of phenols to give dibenzofurans. These results set an important precedent of oxidant‐controlled catalytic transformations of phenols. 相似文献
10.
Zakir Hussain Thomas Oeser Henning Hopf 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(11):o652-o653
The title compound, C14H16O4, was obtained during the synthesis of 2,6‐disubstituted azulene derivatives. In the partially reduced azulene skeleton, the absence of a H atom at the ester substitutent position of the seven‐membered ring, as well as lengthened double bonds, indicate a conjugative stabilized system with two overlaid tautomers. 相似文献
11.
Yonglei Que Hao Shao Haibing He Shuanhu Gao 《Angewandte Chemie (International ed. in English)》2020,59(19):7444-7449
The asymmetric total synthesis of farnesin, a rearranged ent‐kaurenoid, was achieved through a convergent approach involving photo‐Nazarov and intramolecular aldol cyclizations to build the syn‐syn‐syn hydrofluorenol ABC ring system and bicyclo[3.2.1]octane CD ring system in the first application of a UV‐light‐induced excited‐state Nazarov cyclization of a non‐aromatic dicyclic divinyl ketone in a total synthesis. Unlike the conventional acid‐promoted ground‐state Nazarov reaction, the excited‐state Nazarov reaction enables stereospecific formation of the highly strained syn‐syn‐syn‐fused hydrofluorenone scaffold through a disrotatory cyclization. 相似文献
12.
《中国化学》2018,36(4):273-279
o‐Carboryne (1,2‐dehydro‐o‐carborane) is a very useful synthon for the synthesis of a variety of carborane‐functionalized molecules. Diels‐Alder reaction of o‐carboryne with furans gave a series of carborane‐fused oxanorbornenes in moderate to high yields using 1‐OTf‐1,2‐C2B10H11 as carboryne precursor. The resultant cycloadducts can undergo hydrogenation, cyclic oxidation, bromination, [4 + 2]/[2 + 2] cycloaddition and nucleophilic ring opening reaction to afford a variety of highly functionalized carboranes that may find applications as useful basic units in medicine and materials science. 相似文献
13.
[4 + 2] Heterocyclization for Efficient Formation of Substituted Quinoxalines through Carbon–Oxygen Bonds Cleavage
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Man‐Su Tu Hai‐Wei Xu Wei Fan Bo Jiang Shu‐Jiang Tu 《Journal of heterocyclic chemistry》2015,52(3):719-725
A new domino strategy for efficient synthesis of highly functionalized quinoxaline derivatives via [4 + 2] heterocyclization involving ring‐opening of oxirane process has been developed. The reaction promoted by Cs2CO3 was easy to perform in a simple operation from common and inexpensive starting materials. The bisfunctionalization of quinoxaline framework including C2 benzylation and C3 arylation was readily achieved in domino fashion that involved the cleavage of three C–O bonds of 1,3‐diaryl‐2,3‐epoxypropan‐1‐one. 相似文献
14.
Philipp Waser Karl‐Heinz Altmann 《Angewandte Chemie (International ed. in English)》2020,59(40):17393-17397
The total synthesis of the potent new antibiotic disciformycin B ( 2 ) is described, which shows significant activity against methicillin‐ and vancomycin‐resistant Staphylococcus aureus (MRSA/VRSA) strains. The synthetic route is based on macrocyclization of a tetraene substrate to the 12‐membered macrolactone core by ring‐closing olefin metathesis (RCM). Although macrocyclization was accompanied by concomitant cyclopentene formation by an alternative RCM pathway, conditions were established to give the macrocycle as the major product. Key steps in the construction of the RCM substrate include a highly efficient Evans syn‐aldol reaction, the asymmetric Brown allylation of angelic aldehyde, and the stereoselective Zn(BH4)2‐mediated 1,2‐reduction of an enone. The synthesis was completed by late‐stage dehydrative glycosylation to introduce the d ‐arabinofuranosyl moiety and final chemoselective allylic alcohol oxidation. 相似文献
15.
Gold(I)‐Catalyzed Desymmetrization of 1,4‐Dienes by an Enantioselective Tandem Alkoxylation/Claisen Rearrangement
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Hongmiao Wu Dr. Weiwei Zi Prof. Dr. Guigen Li Prof. Dr. Hongjian Lu Prof. Dr. F. Dean Toste 《Angewandte Chemie (International ed. in English)》2015,54(29):8529-8532
An enantioselective alkoxylation/Claisen rearrangement reaction was achieved by a strategic desymmetrization of 1,4‐dienes under the catalysis of (S)‐DTBM‐Segphos(AuCl)2/AgBF4. This reaction system was highly selective for the formation of 3,3‐rearrangement products, providing cycloheptenes with various substitutions in good yield and good to excellent enantioselectivity. This transformation was further extended to bicyclic ring substrates, providing the opportunity to easily assemble 5,6‐ and 6,7‐fused ring systems. 相似文献
16.
Lina Ma Wenjuan Li Hui Xi Xiaohui Bai Enlu Ma Dr. Xiaoyu Yan Prof. Dr. Zhiping Li 《Angewandte Chemie (International ed. in English)》2016,55(35):10410-10413
Exploiting catalytic carbonyl–olefin metathesis is an ongoing challenge in organic synthesis. Reported herein is an FeCl3‐catalyzed ring‐closing carbonyl–olefin metathesis. The protocol allows access to a range of carbo‐/heterocyclic alkenes with good efficiency and excellent trans diastereoselectivity. The methodology presents one of the rare examples of catalytic ring‐closing carbonyl–olefin metathesis. This process is proposed to take place by FeCl3‐catalyzed oxetane formation followed by retro‐ring‐opening to deliver metathesis products. 相似文献
17.
Asymmetric Construction of Pyrrolidines Bearing a Trifluoromethylated Quaternary Stereogenic Center via CuI‐Catalyzed 1,3‐Dipolar Cycloaddition of Azomethine Ylides with β‐CF3‐β,β‐Disubstituted Nitroalkenes
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Dr. Li‐Wei Tang Bao‐Jing Zhao Li Dai Man Zhang Prof. Dr. Zhi‐Ming Zhou 《化学:亚洲杂志》2016,11(17):2470-2477
A direct and convenient method has been developed for the synthesis of optically active pyrrolidines bearing a quaternary stereogenic center containing a CF3 group at the C‐3 position of the pyrrolidine ring. The synthesis system, CuI/Si‐FOXAP‐catalyzed exo‐selective 1,3‐dipolar cycloaddition of azomethine ylides with β‐CF3‐β,β‐disubstituted nitroalkenes, provides pyrrolidines with high diastereoselectivities (up to >98:2 d.r.) and excellent enantioselectivities (up to >99.9 ee) and performs well for a broad scope of substrates under mild conditions. 相似文献
18.
Soonho Hwang Prof. Dr. Deukjoon Kim Prof. Dr. Sanghee Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9977-9982
A highly stereoselective and efficient total synthesis of trans‐dihydronarciclasine from a readily available chiral starting material was developed. The synthesis defines two of the five stereogenic centers of the natural product by an amino acid ester–enolate Claisen rearrangement. The other three stereogenic centers are created in a highly stereocontrolled fashion via a six‐ring vinylogous ester intermediate, which is generated from the γ,δ‐unsaturated ester functional group of the Claisen rearrangement product in an efficient three‐step sequence. This concise total synthesis exemplifies the use of a highly regioselective Friedel–Crafts‐type cyclization to form the B ring via an isocyanate intermediate derived from an N‐Boc group, which is superior to the conventional method using an imino triflate intermediate. This same N‐Boc group is employed to give high selectivity in the Claisen rearrangement earlier in the sequence. 相似文献
19.
David J. Wiedenfeld Vladimir N. Nesterov Mark A. Minton Crystal L. Montoya 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(7):o536-o538
The title compounds, 1‐chloro‐3,6‐dimethoxy‐2,5‐dimethylbenzene, (IIIa), and 1‐chloro‐3,6‐dimethoxy‐2,4‐dimethylbenzene, (IIIb), both C10H13ClO2, were obtained from 2,5‐ and 2,6‐dimethyl‐1,4‐benzoquinone, respectively, and are intermediates in the synthesis of ammonium quinone derivatives. The isomers have different substituents around the methoxy groups and crystallize in different space groups. In both molecules, the methoxy groups each have different orientations with respect to the benzene ring. In both cases, one methoxy group lies in the plane of the ring and can participate in conjugation with the aromatic system, while the second is almost perpendicular to the plane of the aromatic ring. The C—O—C bond angles around these substituents are also different: 117.5 (4) and 118.2 (3)° in (IIIa) and (IIIb), respectively, when the methoxy groups lie in the plane of the ring, and 114.7 (3) and 113.6 (3)° in (IIIa) and (IIIb), respectively, when they are out of the plane of the ring. 相似文献
20.
Matthias Zeller Virginia B. Pett LeRoy W. Haynes 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(6):o343-o346
The reaction of 2‐chloro‐5‐nitropyridine with two equivalents of base produces the title carbanion as an intermediate in a ring‐opening/ring‐closing reaction. The crystal structures of the tetra‐n‐butylammonium salts of the intermediates, C16H36N+·C5H3N2O3−, revealed that pseudo‐cis and pseudo‐trans isomers are possible. One crystal structure displayed a mixture of the two isomers with approximately 90% pseudo‐cis geometry and confirms the structure predicted by the SN(ANRORC) mechanism. The pseudo‐cis intermediate undergoes a slow isomerization over a period of months to the pseudo‐trans isomer, which does not have the appropriate geometry for the subsequent ring‐closing reaction. The structure of the pure pseudo‐trans isomer is also reported. In both isomers, the negative charge is highly delocalized, but relatively small differences in C—C bond distances indicate a system of conjugated double bonds with the nitro group bearing the negative charge. The packing of the two unit cells is very similar and largely determined by the interactions between the planar carbanion and the bulky tetrahedral cation. 相似文献