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1.
A concise and efficient strategy has been developed to construct a polyketide chain by employing relay asymmetric hydrogenations catalyzed by two chiral spiro iridium catalysts. By using this strategy, an enantioselective total synthesis of (?)‐doliculide has been achieved in 19 steps with 6.9 % overall yield. The route features high enantioselectivity and diastereoselectivity. The catalyst loading can be as low as 0.005 mol‐%. It is convenient to obtain natural polyketides and their analogues by this strategy. 相似文献
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Lian‐Dong Guo Xiong‐Zhi Huang Shi‐Peng Luo Wen‐Sen Cao Prof. Yuan‐Ping Ruan Dr. Jian‐Liang Ye Prof. Dr. Pei‐Qiang Huang 《Angewandte Chemie (International ed. in English)》2016,55(12):4064-4068
The first total synthesis of the alkaloid (?)‐haliclonin A is reported. The asymmetric synthesis relied on a novel organocatalytic asymmetric conjugate addition of nitromethane with 3‐alkenyl cyclohex‐2‐enone to set the stereochemistry of the all‐carbon quaternary stereogenic center. The synthesis also features a Pd‐promoted cyclization to form the 3‐azabicyclo[3,3,1]nonane core, a SmI2‐mediated intermolecular reductive coupling of enone with aldehyde to form the requisite secondary chiral alcohol, ring‐closing alkene and alkyne metathesis reactions to build the two aza‐macrocyclic ring systems, and an unprecedented direct transformation of enol into enone. 相似文献
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Prof. Dr. Hiromichi Fujioka Kenji Nakahara Naoyuki Kotoku Yusuke Ohba Yasushi Nagatomi Tsung‐Lung Wang Yoshinari Sawama Kenichi Murai Kie Hirano Tomohiro Oki Shintaro Wakamatsu Prof. Dr. Yasuyuki Kita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(43):13861-13870
A route for the asymmetric synthesis of (?)‐stenine, a member of the Stemona alkaloid family used as folk medicine in Asian countries, is described. The key features of the sequence employed include stereoselective transformations on a cyclohexane ring controlled by a chiral auxiliary unit and an intramolecular Mitsunobu reaction to construct the perhydroindole ring system. By using an intermediate in the route to (?)‐stenine, an asymmetric synthesis of 9a‐epi‐stenine was also executed. The C(9a) stereocenter in 9a‐epi‐stenine was installed by using a Staudinger/aza‐Wittig reaction of a keto–azide precursor followed by reduction of the resulting imine. The results of this effort demonstrate the applicability of the chiral auxiliary based strategy to the preparation of naturally occurring alkaloids that contain highly functionalized cyclohexane cores. 相似文献
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Prof. Dr. Lutz F. Tietze Stefan Jackenkroll Dr. Christian Raith Dr. Dirk A. Spiegl Johannes R. Reiner Maria Claudia Ochoa Campos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4876-4882
For the synthesis of (?)‐diversonol (ent‐ 1 ), an enantioselective domino‐Wacker/carbonylation/methoxylation reaction and an enantioselective Wacker oxidation were used to give the chroman in high yield and 96 % and 93 % ee, respectively. Dihydroxylation at the vinyl moiety using the Sharpless procedure and a Wittig–Horner reaction followed by hydrogenation, benzylic oxidation, and an intramolecular acylation provided the tetrahydroxanthenone, from which ent‐ 1 is accessible in a few steps. Furthermore, the synthesis of the diastereomeric diversonol rac‐1,9 a‐epi‐diversonol (rac‐ 41 ) is also described. 相似文献
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Xinkan Yang Houqiang Lv Xiaoru Shao Cheng Tao Dr. Huifei Wang Dr. Bin Cheng Dr. Yun Li Jingjing Guo Jing Zhang Prof. Dr. Hongbin Zhai 《Angewandte Chemie (International ed. in English)》2018,57(4):947-951
(?)‐Daphnilongeranin B and (?)‐daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (?)‐daphnilongeranin B and a bioinspired synthesis of (?)‐daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late‐stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline. 相似文献
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Dr. Zhengren Xu Dr. Xu Bao Dr. Qian Wang Prof. Dr. Jieping Zhu 《Angewandte Chemie (International ed. in English)》2015,54(49):14937-14940
A concise enantioselective total synthesis of (?)‐isoschizogamine, a complex bridged polycyclic monoterpene indole alkaloid, was accomplished. N‐Alkylation of an enantio‐enriched imine with an alkyl iodide afforded an iminium salt, which, upon heating by microwave irradiation in the presence of pivalic acid, was converted into the hexacyclic structure of natural product by a complex but ordered domino sequence. The one‐pot process leading to the formation of one C? C bond and three C? N bonds created three rings and three contiguous stereogenic centers with complete control of both the relative and absolute stereochemistry. 相似文献
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Szilrd Varga Pter Angyal Gbor Martin Orsolya Egyed Tams Holczbauer Tibor Sos 《Angewandte Chemie (International ed. in English)》2020,59(32):13547-13551
We report 8‐step syntheses of (?)‐minovincine and (?)‐aspidofractinine using easily available and inexpensive reagents and catalyst. A key element of the strategy was the utilization of a sequence of cascade reactions to rapidly construct the penta‐ and hexacyclic frameworks. These cascade transformations included organocatalytic Michael‐aldol condensation, a multistep anionic Michael‐SN2 cascade reaction, and Mannich reaction interrupted Fischer indolization. To streamline the synthetic routes, we also investigated the deliberate use of steric effect to secure various chemo‐ and regioselective transformations. 相似文献
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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
11.
Catalytic Asymmetric Crotylation of Aldehydes: Application in Total Synthesis of (−)‐Elisabethadione 下载免费PDF全文
Dr. Paul S. O'Hora Dr. Celia A. Incerti‐Pradillos Dr. Mikhail A. Kabeshov Sergei A. Shipilovskikh Dr. Aleksandr E. Rubtsov Dr. Mark R. J. Elsegood Prof. Dr. Andrei V. Malkov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4551-4555
A new, highly efficient Lewis base catalyst for a practical enantio‐ and diastereoselective crotylation of unsaturated aldehydes with E‐ and Z‐crotyltrichlorosilanes has been developed. The method was employed as a key step in a novel asymmetric synthesis of bioactive serrulatane diterpene (?)‐elisabethadione. Other strategic reactions for setting up the stereogenic centers included anionic oxy‐Cope rearrangement and cationic cyclization. The synthetic route relies on simple, high yielding reactions and avoids use of protecting groups or chiral auxiliaries. 相似文献
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Prof. Dr. J. Stephen Clark Dr. Chao Xu 《Angewandte Chemie (International ed. in English)》2016,55(13):4332-4335
A highly efficient 12‐step synthesis of the marine alkaloid (?)‐nakadomarin A has been accomplished. The key advanced intermediate, a tetracyclic ketone derivative, was constructed in just seven steps using a sequence that includes an asymmetric Pauson–Khand reaction, an Overman rearrangement reaction, a ring‐closing metathesis reaction, and an amination reaction. Late introduction of the furan ring during the synthesis of (?)‐nakadomarin A means that the key tetracyclic ketone derivative has the potential to serve as an advanced intermediate for the synthesis of related marine alkaloids. 相似文献
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Daisuke Yamashita Yoshihisa Murata Dr. Naotsuka Hikage Dr. Ken‐ichi Takao Prof. Dr. Atsuo Nakazaki Dr. Susumu Kobayashi Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(8):1404-1406
No bones about it : (?)‐Norzoanthamine, a promising candidate for an anti‐osteoporotic drug, was the target of a total synthesis (see scheme). The final bisaminal formation with AcOH/H2O gave the DEFG ring, while the cyclization precursor was prepared by installing the remaining bisaminal unit after oxidative cleavage of the cyclopentanol moiety.
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Ryosuke Yamada Dr. Yohei Adachi Dr. Satoshi Yokoshima Prof. Tohru Fukuyama 《Angewandte Chemie (International ed. in English)》2016,55(20):6067-6070
Total synthesis of (?)‐daphenylline, a hexacyclic Daphniphyllum alkaloid, was achieved. Construction of the tricyclic DEF ring system was initiated by asymmetric Negishi coupling followed by an intramolecular Friedel–Crafts reaction. Installation of a side chain onto the tricyclic core was carried out through Sonogashira coupling, stereocontrolled Claisen rearrangement by taking advantage of the characteristic conformation of the tricyclic DEF core, and the stereoselective alkylation of a lactone. After the introduction of a glycine unit, the ABC ring system was stereoselectively constructed through intramolecular cycloaddition of the cyclic azomethine ylide. 相似文献
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Zhuliang Zhong Donghui Ma Gaoyuan Zhao Huilin Li Dengyu Xu Dr. Xingang Xie Prof. Dr. Xuegong She 《化学:亚洲杂志》2015,10(12):2599-2603
The first asymmetric total synthesis of kravanhin B has been accomplished with a linear reaction sequence of 13 steps starting from (R)‐(?)‐carvone. The synthesis features an intramolecular aldol cyclization to construct the desired cis‐fused decalin skeleton and an acid‐catalyzed dehydration and olefin isomerization to install the γ‐butenolide ring. 相似文献
19.
We have developed an efficient total synthesis of (?)‐morphine in 5 % overall yield with the longest linear sequence consisting of 17 steps from 2‐cyclohexen‐1‐one. The cyclohexenol unit was prepared by means of an enzymatic resolution and a Suzuki–Miyaura coupling as key steps. Construction of the morphinan core features an intramolecular aldol reaction and an intramolecular 1,6‐addition. Furthermore, mild deprotection conditions to remove the 2,4‐dinitrobenzenesulfonyl (DNs) group enabled the facile construction of the morphinan skeleton. We have also established an efficient synthetic route to a cyclohexenol unit containing an N‐methyl‐DNs‐amide moiety. 相似文献
20.
Biomimetic Total Syntheses of (−)‐Leucoridines A and C through the Dimerization of (−)‐Dihydrovalparicine 下载免费PDF全文
Praveen Kokkonda Keaon R. Brown Trevor J. Seguin Dr. Steven E. Wheeler Dr. Shivaiah Vaddypally Dr. Michael J. Zdilla Dr. Rodrigo B. Andrade 《Angewandte Chemie (International ed. in English)》2015,54(43):12632-12635
Concise biomimetic syntheses of the Strychnos‐Strychnos‐type bis‐indole alkaloids (?)‐leucoridine A ( 1 ) and C ( 2 ) were accomplished through the biomimetic dimerization of (?)‐dihydrovalparicine ( 3 ). En route to 3 , the known alkaloids (+)‐geissoschizoline ( 8 ) and (?)‐dehydrogeissoschizoline ( 10 ) were also prepared. DFT calculations were employed to elucidate the mechanism, which favors a stepwise aza‐Michael/spirocyclization sequence over the alternate hetero‐Diels–Alder cycloaddition reaction. 相似文献