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Zhen‐Gao Feng Wen‐Ju Bai Thomas R. R. Pettus 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(6):1884-1887
The total syntheses of medicarpin, sophoracarpan A, and kushecarpin A from a common intermediate are achieved by using ortho‐ and para‐quinone methide chemistry. Additionally, the relative stereochemistry of sophoracarpan A and B have been reassigned. 相似文献
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Cedric L. Hugelshofer Thomas Magauer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(42):11533-11537
The first asymmetric total synthesis of the antifeedant terpenoids (+)‐norleucosceptroid A, (−)‐norleucosceptroid B, and (−)‐leucosceptroid K has been accomplished. This highly concise synthetic route was guided by our efforts to develop a platform for the collective synthesis of a whole family of antifeedant natural products. The synthesis features a Hauser–Kraus‐type annulation followed by an unprecedented, highly efficient intramolecular dilactol aldol‐type condensation reaction to produce the 5,6,5 skeleton. The developed synthetic route proceeds for norleucosceptroid A and B in 16 steps (longest linear sequence) from known compounds. 相似文献
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Dylan Dagoneau Zhengren Xu Qian Wang Jieping Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(2):770-773
A divergent total synthesis of three structurally distinct natural products from imine 9 was accomplished through an approach featuring: 1) a Pd‐catalyzed decarboxylative cross‐coupling, and 2) heteroannulation of 9 with bromoacetaldehyde and oxalyl chloride to give tetrahydroindolizine 6 and dioxopyrrole 7 , respectively. The former was converted into (−)‐rhazinilam, while the latter was converted into (−)‐leucomidine B and (+)‐leuconodine F. A substrate‐directed highly diastereoselective reduction of a sterically unbiased double bond by using a homogeneous palladium catalyst was developed. A self‐induced diastereomeric anisochronism (SIDA) phenomenon was observed for leucomidine B. 相似文献
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Tantalum Cluster in an Oxidic Matrix – Synthesis and Structures of Mixed-Valence Oxotantalates M2–δTa15O32 (M = K, Rb (δ = 0); M = Sr (δ = 0.15), Ba (δ = 0.12)) The mixed-valent oxides Sr1.85Ta15O32 ( 1 ), Ba1.88Ta15O32 ( 2 ), K2Ta15O32 ( 3 ), Rb2Ta15O32 ( 4 ) were prepared from appropriate mixtures of Ta2O5, tantalum and the corresponding carbonate at 1520–1670 K in sealed tantalum tubes. According to X-ray single crystal structure analyses the oxides crystallize in the space group R3¯, Z = 1. The lattice parameters in the hexagonal setting are a = 777.36(11), c = 3516.2(7) pm for 1 , a = 778.87(11), c = 3548.1(7) pm for 2 , a = 780.7(2), c = 3573.1(11) pm for 3 , and a = 781.90(11), c = 3593.0(7) pm for 4 . The oxide ions form a defect dense packing with the layer sequence chhhh. Anti-cuboctahedral sites are completely occupied by the alkali metal cations. The alkaline earth cations occupy 92 to 94% of such sites; they are displaced from the centres. Smaller voids are located in the centres of the cuboctahedral Ta6O12 clusters forming the characteristic structural unit of these low-valent oxotantalates. In case of 3 and 4 the clusters have 13 electrons, in case of 1 and 2 they have close to 15 electrons available for Ta–Ta-bonding. Moreover, the structures of the alkali and alkaline earth metal compounds differ notably with respect to the spectrum of Ta–O and Ta–Ta distances in the Ta3O13 octahedra triples forming another characteristic structural unit for these oxides. Such differences are traced back to distinct local charge balances for the uni- and divalent cations. The oxides 2 , 3 are semiconductors with band gaps ranging from 130 to 360 meV. 相似文献
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Unified Total Syntheses of (−)‐Medicarpin, (−)‐Sophoracarpan A,and (±)‐Kushecarpin A with Some Structural Revisions 下载免费PDF全文
Zhen‐Gao Feng Wen‐Ju Bai Prof. Thomas R. R. Pettus 《Angewandte Chemie (International ed. in English)》2015,54(6):1864-1867
The total syntheses of medicarpin, sophoracarpan A, and kushecarpin A from a common intermediate are achieved by using ortho‐ and para‐quinone methide chemistry. Additionally, the relative stereochemistry of sophoracarpan A and B have been reassigned. 相似文献
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Yuichi Momoi Dr. Kei‐ichiro Okuyama Dr. Hiroki Toya Dr. Kenji Sugimoto Dr. Kentaro Okano Prof. Dr. Hidetoshi Tokuyama 《Angewandte Chemie (International ed. in English)》2014,53(48):13215-13219
The enantiocontrolled total synthesis of (?)‐haouamine B pentaacetate was accomplished via an optically active indane‐fused β‐lactam, which was prepared by a newly developed Friedel–Crafts reaction. Subsequent cleavage of the β‐lactam and an intramolecular McMurry coupling reaction provided the core indane‐fused tetrahydropyridine, which led to the elucidation of the structure, as proposed by Trauner and Zubía. 相似文献
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Jie Ouyang Rui Yan Xianwei Mi Prof. Dr. Ran Hong 《Angewandte Chemie (International ed. in English)》2015,54(37):10940-10943
The first total synthesis of (?)‐hosieine A was accomplished and features an unprecedented nitroso–ene cyclization to construct the 2‐azabicyclo[3.2.1]octane ring system. Phosphine‐enabled stereoselective bromohydrination provided interesting mechanistic insights into the anti‐Markovnikov process. Also noteworthy is the retention of stereochemistry at C9 in the facile radical debromination initiated by Et3B/air. 相似文献
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Total synthesis of the polyhydroxy caprolactam amide natural product, bengamide E, is accomplished starting from tartaric acid. Key reactions in the synthesis include desymmetrization of the bis(dimethylamide) unit of tartaric acid, Zn(BH4)2‐mediated anti‐selective reduction, and a Horner–Wadsworth–Emmons olefination. 相似文献
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Prof. Dr. Lutz F. Tietze Dr. Ling Ma Johannes R. Reiner Stefan Jackenkroll Sven Heidemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8610-8614
Blennolide A can be synthesized through an enantioselective domino‐Wacker/carbonylation/methoxylation reaction of 7 a with 96 % ee and an enantioselective Wacker oxidation of 7 b with 89 % ee. Further transformations led to the α,β‐unsaturated ester (E)‐ 17 , which was subjected to a highly selective Michael addition, introducing a methyl group to give 18 a . After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (?)‐blennolide A (ent‐ 1 ) in a few steps. 相似文献
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We discuss the dynamic solid‐state properties of crystalline phases E(XMe3)4 as seen by solid‐state NMR and powder X‐ray diffraction. In the first part we will qualitatively describe some of the NMR tools suitable for such investigations. In the second part we will give examples from the group of solid compounds E(XMe3)4 with E = C, Si, Ge and X = Si, Sn. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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