Methyl carbenoid addition to enol ethers carrying a chiral auxiliary. Stereocontrol of three chiral centers on cyclopropyl ether

1992 ◽  
Vol 33 (3) ◽  
pp. 367-368 ◽  
Author(s):  
Takashi Sugimura ◽  
Toshifumi Katagiri ◽  
Akira Tai
Author(s):  
Douglass F. Taber

Varinder K. Aggarwal of the University of Bristol showed (Angew. Chem. Int. Ed. 2009, 48, 1149) that condensation of a boronic ester 2 with a metalated aziridine 1 led, after oxidation, to the defined amino alcohol 3. Hisashi Yamamoto of the University of Chicago developed (Angew. Chem. Int. Ed. 2009, 48, 3333) conditions for the diastereoselective addition of an organometallic to an α-nitrosylated aldehyde, to give, after reduction, the diol 6. Xiaoyu Wu of Shanghai University and Gang Zhao of the Shanghai Institute of Organic Chemistry designed (Adv. Synth. Cat. 2009, 351, 158) an organocatalyst that mediated the enantioselective addition of hydroxyacetone 7 to a range of aldehydes. Andrew G. Myers of Harvard University found (J. Am. Chem. Soc. 2009, 131, 5763) that trialkylaluminum reagents opened epoxides of enol ethers at the more substituted position, delivering protected diols such as 10. Keiji Maruoka of Kyoto University created (Angew. Chem. Int. Ed. 2009, 48, 1838) an organocatalyst for the addition of an aldehyde 11 to an imine 12, to give 13. Markus Kalesse of Leibnitz Universität Hannover showed (Tetrahedron Lett. 2009, 50, 3485) that an organocatalyst could mediate the selective γ-reactivity of 15, leading to 16. Barry M. Trost of Stanford University found (J. Am. Chem. Soc. 2009, 131, 1674) that an organocatalyst directed the addition of diazoacetate 18 to an aldehyde, to give, after further reaction with a trialkylborane, the syn aldol product 19. Professor Trost also demonstrated (J. Am. Chem. Soc. 2009, 131, 4572) that a related complex mediated the conjugate addition of 22 to 21. Enantioselective construction of arrays of alkylated stereogenic centers is a particular challenge. Ji Zhang, then at Pfizer, found (Tetrahedron Lett. 2009, 50, 1167) that the chiral auxiliary of 24 directed both the conjugate addition and the subsequent protonation, and also allowed the product 25 to be brought to > 98% purity by crystallization. Tönis Kanger of Tallinn University of Technology developed (J. Org. Chem. 2009, 74, 3772) an organocatalyst for the conjugate addition of aldehydes to nitrostyrenes such as 26 to give 27.


ChemInform ◽  
2010 ◽  
Vol 29 (50) ◽  
pp. no-no
Author(s):  
Y. TAKEMOTO ◽  
Y. BABA ◽  
N. YOSHIKAWA ◽  
C. IWATA ◽  
T. TANAKA ◽  
...  

1998 ◽  
pp. 1911-1912 ◽  
Author(s):  
Yoshiji Takemoto ◽  
Toshiro Ibuka ◽  
Yoshiji Takemoto ◽  
Yasutaka Baba ◽  
Naoki Yoshikawa ◽  
...  

2020 ◽  
Author(s):  
Daniel B. Straus ◽  
Robert J. Cava

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C<sub>60</sub>(SnI<sub>4</sub>)<sub>2</sub> from icosahedral buckminsterfullerene (C<sub>60</sub>) and tetrahedral SnI4 molecules through spontaneous self-assembly. The SnI<sub>4</sub> tetrahedra template the Sn atoms into a chiral cubic three-connected net of the SrSi<sub>2</sub> type that is held together by van der Waals forces. Our results represent the remarkable emergence of a self-assembled chiral material from two of the most highly symmetric molecules, demonstrating that almost any molecular, nanocrystalline, or engineered precursor can be considered when designing chiral assemblies.


2018 ◽  
Author(s):  
Tanner C. Jankins ◽  
Robert R. Fayzullin ◽  
Eugene Khaskin

We report a one-step, Ru(II)-catalyzed cyclopropanation reaction that is conceptually different from the previously reported protocols that include Corey-Chaykovsky, Simmons-Smith, and metal catalyzed carbene attack on olefins. Under the current protocol, various alcohols are transformed into sulfone substituted cyclopropanes with excellent isolated yields and diastereoselectivities. This new reaction forms highly congested cyclopropane products with three new C–C bonds, three or two new chiral centers and one new quaternary carbon center. 22 examples of isolated substrates are given. Previously reported synthetic routes for similar substrates are all multi-step, linear routes that proceed with overall low yields and poor control of stereochemistry. Experimental mechanistic investigations suggest initial metal-catalyzed dehydrogenation of the alcohol substrate and catalyst independent stepwise attack of two equivalents of sulfone on the aldehyde under basic conditions. While the Ru(II) is only responsible for the initial dehydrogenation step, the rate of aldehyde formation is crucial to maintaining the right balance of intermediates needed to afford the cyclopropane product.


2018 ◽  
Author(s):  
Zhanyu Li ◽  
Mengru Zhang ◽  
Yu Zhang ◽  
Shuang Liu ◽  
Jinbo Zhao ◽  
...  

Deployment of organoboron in lieu of the strongly basic <br>organometallic reagents as carbon source in Cu-catalyzed <br>cyclopropene carbometallation opens unprecedented three-<br>component reactivity for stereoselective synthesis of poly-substituted cyclopropanes. A proof-of-principle demonstration of this novel carbometallation strategy is presented herein for a highly convergent access to poly-substituted aminocyclopropane framework via <br>carboamination. Preliminary results on asymmetric desymmetrization with commercial bisphosphine ligands attained high levels of enantioselection, offering a straightforward access to enantioenriched aminocyclopropanes bearing all-three chiral centers, including an all-carbon quaternary center. This strategy may underpin a host of novel synthetic protocols for poly-substituted cyclopropanes. <br>


2020 ◽  
Vol 24 (4) ◽  
pp. 354-401 ◽  
Author(s):  
Keisham S. Singh

Marine natural products (MNPs) containing pyrone rings have been isolated from numerous marine organisms, and also produced by marine fungi and bacteria, particularly, actinomycetes. They constitute a versatile structure unit of bioactive natural products that exhibit various biological activities such as antibiotic, antifungal, cytotoxic, neurotoxic, phytotoxic and anti-tyrosinase. The two structure isomers of pyrone ring are &#947;- pyrone and &#945;-pyrone. In terms of chemical motif, &#947;-pyrone is the vinologous form of &#945;- pyrone which possesses a lactone ring. Actinomycete bacteria are responsible for the production of several &#945;-pyrone compounds such as elijopyrones A-D, salinipyrones and violapyrones etc. to name a few. A class of pyrone metabolites, polypropionates which have fascinating carbon skeleton, is primarily produced by marine molluscs. Interestingly, some of the pyrone polytketides which are found in cone snails are actually synthesized by actinomycete bacteria. Several pyrone derivatives have been obtained from marine fungi such as Aspergillums flavus, Altenaria sp., etc. The &#947;-pyrone derivative namely, kojic acid obtained from Aspergillus fungus has high commercial demand and finds various applications. Kojic acid and its derivative displayed inhibition of tyrosinase activity and, it is also extensively used as a ligand in coordination chemistry. Owing to their commercial and biological significance, the synthesis of pyrone containing compounds has been given attention over the past years. Few reviews on the total synthesis of pyrone containing natural products namely, polypropionate metabolites have been reported. However, these reviews skipped other marine pyrone metabolites and also omitted discussion on isolation and detailed biological activities. This review presents a brief account of the isolation of marine metabolites containing a pyrone ring and their reported bio-activities. Further, the review covers the synthesis of marine pyrone metabolites such as cyercene-A, placidenes, onchitriol-I, onchitriol-II, crispatene, photodeoxytrichidione, (-) membrenone-C, lihualide-B, macrocyclic enol ethers and auripyrones-A & B.


2014 ◽  
Vol 18 (5) ◽  
pp. 525-546 ◽  
Author(s):  
Carmen Hernandez-Cervantes ◽  
Miriam Alvarez-Corral ◽  
Manuel Munoz-Dorado ◽  
Ignacio Rodriguez-Garcia

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