Alkene and Alkyne Metathesis: Navenone B (Cossy), (+)-Asperpentyn (Daesung Lee), (-)-Amphidinolide K (Eun Lee), Norhalichondrin B (Phillips)

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Allylic Alcohol ◽  
Alkyne Metathesis ◽  
University Of Illinois ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
University Of Colorado ◽  
National University ◽  
The Cross ◽  
Seoul National University ◽  
The University

A variety of antibiotics and immune-suppressive agents contain extended arrays of all- ( E )-polyenes. Samir Bouzbouz of CNS Rouen and Janine Cossy of ESPCI ParisTech devised ( Synlett 2009, 803) a simple iterative route to polyacetates such as 1 and demonstrated that after cross-metathesis, elimination, in this case to give Navenone B 3, was facile. Both ketones and esters can promote the elimination. Daesung Lee of the University of Illinois at Chicago designed (Organic Lett. 2009, 11 , 571) a clever chain-walking ring-closing ene-yne metathesis, cyclizing 4 to 5. Deprotection led to (+)-asperpentyn 6. This should be a general entry to such polyoxygenated cyclohexenes. For the structures of H2 and G2, see Organic Highlights, September 13, 2004. One of the challenges in the synthesis of (-)-amphidinoloide K 10 is the assembly of the complex conjugated diene. Eun Lee of Seoul National University found (Angew. Chem. Int. Ed. 2009, 48, 2364) a solution to this problem in the Ru-catalyzed cross-metathesis between the alkyne 7 and the alkene 8. Note that the cross-metathesis proceeded with high regioselectivity and with substantial (7.5:1) control of the product alkene geometry. For the construction of complex natural products such as norhalichondrin B 14, it is important to employ a convergent synthetic strategy. For this to be successful, efficient methods for convergent coupling are required. In the course of a synthesis of 14, Andrew J. Phillips of the University of Colorado showed (Angew. Chem. Int. Ed. 2009, 48, 2346) that Ru-mediated cross-metathesis could be used to couple the enone 11 with the alkene 12. A less congested version of H2, designed by Robert H. Grubbs of Caltech, was used for the coupling. The electron-deficient alkene of 11 and the more electron-rich alkene of 12 made a matched set, promoting the cross-coupling. Note again, in this context, the desirability of leaving the allylic alcohol of 12 unprotected to facilitate Ru-catalyzed alkene cross-metathesis.

Enantioselective Construction of Alkylated Centers: The Shishido Synthesis of (+)-Helianane

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Allylic Alcohol ◽  
National University ◽  
Cu Catalyst ◽  
Rh Catalyst ◽  
Enantioselective Acylation ◽  
Enantioselective Addition ◽  
Institute Of Technology ◽  
Enantioselective Alkylation ◽  
Seoul National University ◽  
The University

Teck-Peng Loh of Nanyang Technological University developed (Org. Lett. 2011, 13, 876) a catalyst for the enantioselective addition of an aldehyde to the versatile acceptor 2 to give 3. Kirsten Zeitler of the Universität Regensburg employed (Angew. Chem. Int. Ed. 2011, 50, 951) a complementary strategy for the enantioselective coupling of 4 with 5. Clark R. Landis of the University of Wisconsin devised (Org. Lett. 2011, 13, 164) an Rh catalyst for the enantioselective formylation of the diene 7. Don M. Coltart of Duke University alkylated (J. Am. Chem. Soc. 2011, 133, 8714) the chiral hydrazone of acetone to give 9, then alkylated again to give, after hydrolysis, the ketone 11 in high ee. Youming Wang and Zhenghong Zhou of Nankai University effected (J. Org. Chem. 2011, 76, 3872) the enantioselective addition of acetone to the nitroalkene 12. Takeshi Ohkuma of Hokkaido University achieved (Angew. Chem. Int. Ed. 2011, 50, 5541) high ee in the Ru-catalyzed hydrocyanation of 15. Gregory C. Fu, now at the California Institute of Technology, coupled (J. Am. Chem. Soc. 2011, 133, 8154) the 9-BBN borane 18 with the racemic chloride 17 to give 19 in high ee. Scott McN. Sieburth of Temple University optimized (Org. Lett. 2011, 13, 1787) an Rh catalyst for the enantioselective intramolecular hydrosilylation of 20 to 21. Several general methods have been devised for the enantioselective assembly of quaternary alkylated centers. Sung Ho Kang of KAIST Daejon developed (J. Am. Chem. Soc. 2011, 133, 1772) a Cu catalyst for the enantioselective acylation of the prochiral diol 22. Hyeung-geun Park of Seoul National University established (J. Am. Chem. Soc. 2011, 133, 4924) a phase transfer catalyst for the enantioselective alkylation of 24. Peter R. Schreiner of Justus-Liebig University Giessen found (J. Am. Chem. Soc. 2011, 133, 7624) a silicon catalyst that efficiently rearranged the Shi-derived epoxide of 26 to the aldehyde 27. Amir H. Hoveyda of Boston College coupled (J. Am. Chem. Soc. 2011, 133, 4778) 28 with the alkynyl Al reagent 29 to give 30 in high ee. Kozo Shishido of the University of Tokushima prepared (Synlett 2011, 1171) 31 by the Mitsunobu coupling of m-cresol with the enantiomerically pure allylic alcohol.

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

scholarly journals Back-end porting of FT_MX based on LLVM compilation architecture

2021 ◽  
Vol 336 ◽  
pp. 04018
Author(s):  
Ping Deng ◽  
Xiaolong Zhu ◽  
Haiyan Sun ◽  
Yi Ren
Keyword(s):  
Open Source ◽  
High Performance ◽  
Instruction Set ◽  
University Of Illinois ◽  
Specific Process ◽  
Defense Technology ◽  
Migration Mechanism ◽  
National University ◽  
Compiler Framework ◽  
The University

The processor FT_MX is a high-performance chip independently developed by the National University of Defense Technology, with an innovative architecture and instruction set. LLVM architecture is a widely used and efficient open source compiler framework initiated by the University of Illinois. This paper introduces the basic architecture and functions of LLVM, analyzes the back-end migration mechanism of the architecture in detail, and gives the specific process of implementing FT_MX back-end migration, and realizes the support of LLVM architecture to the back-end of FT_MX processor.

Advances in Alkene and Alkyne Metathesis

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Acetic Acid ◽  
Diels Alder ◽  
Alkyne Metathesis ◽  
Santa Barbara ◽  
Ring Closing Metathesis ◽  
Enol Ethers ◽  
Cross Metathesis ◽  
Simple Filtration ◽  
The University ◽  
Academy Of Sciences

As alkene metathesis is extended to more and more challenging substrates, improved catalysts and solvents are required. Robert H. Grubbs of Caltech developed (Organic Lett. 2008, 10, 441) the diisopropyl complex 1, that efficiently formed the trisubstituted alkene 6 by cross metathesis of 4 with 5. Hervé Clavier and Stephen P. Nolan of ICIQ, Tarragona, and Marc Mauduit of ENSC Rennes found (J. Org. Chem. 2008, 73, 4225) that after cyclization of 7 with the complex 2b, simple filtration of the reaction mixture through silica gel delivered the product 8 containing only 5.5 ppm Ru. The merit of CH2Cl2 as a solvent for alkene metathesis is that the catalysts (e.g. 1 - 3) are very stable. Claire S. Adjiman of Imperial College and Paul C. Taylor of the University of Warwick established (Chem. Commun. 2008, 2806) that although the second generation Grubbs catalyst 3 is not as stable in acetic acid, for the cyclization of 9 to 10 it is a much more active catalyst in acetic acid than in CH2Cl2 . Bruce H. Lipshutz of the University of California, Santa Barbara observed (Adv. Synth. Cat . 2008, 350, 953) that even water could serve as the reaction solvent for the challenging cyclization of 11 to 12, so long as the solubility- enhancing amphiphile PTS was included. Ernesto G. Mata of the Universidad Nacional de Rosario explored (J. Org. Chem. 2008, 73, 2024) resin isolation to optimize cross-metathesis, finding that the acrylate 13 worked particularly well. Karol Grela of the Polish Academy of Sciences, Warsaw optimized (Chem. Commun. 2008, 2468) cross-metathesis with a halogenated alkene 16. Jean-Marc Campagne of ENSC Montpellier extended (J. Am. Chem. Soc. 2008, 130, 1562) ring-closing metathesis to enynes such as 19. The product diene 20 was a reactive Diels-Alder dienophile. István E. Markó of the Université Catholique de Louvain applied (Tetrahedron Lett. 2008, 49, 1523) the known (OHL 20070122) ring-closing metathesis of enol ethers to the cyclization of the Tebbe product from 23. The ether 24 was oxidized directly to the lactone 25.

Functional Group Interconversion

2015 ◽  
Author(s):  
Tristan H. Lambert
Keyword(s):  
Carboxylic Acid ◽  
High Yield ◽  
Staudinger Ligation ◽  
University Of Alberta ◽  
University Of Tennessee ◽  
University Of British Columbia ◽  
National University ◽  
Seoul National University ◽  
Oxidative Amidation ◽  
The University

Glenn M. Samm is at the University of British Columbia reported (Angew. Chem. Int. Ed. 2012, 51, 10804) the photofluorodecarboxylation of aryloxyacids such as 1 using Selectfluor 2. Jean-François Paquin at the Université Laval found (Org. Lett. 2012, 14, 5428) that the halogenation of alcohols (e.g., 4 to 5) could be achieved with [Et2NSF2]BF4 (XtalFluor-E) in the presence of the appropriate tetraethylammonium halide. A method for the reductive bromination of carboxylic acid 6 to bromide 7 was developed (Org. Lett. 2012, 14, 4842) by Norio Sakai at the Tokyo University of Science. Professor Sakai also reported (Org. Lett. 2012, 14, 4366) a related method for the reductive coupling of acid 8 with octanethiol to produce thioether 9. The esterification of primary alcohols in water-containing solvent was achieved (Org. Lett. 2012, 14, 4910) by Michio Kurosu at the University of Tennessee Health Science Center using the reagent 11, such as in the conversion of alcohol 10 to produce 12 in high yield. Hosahudya N. Gopi discovered (Chem. Commun. 2012, 48, 7085) that the conversion of thioacid 13 to amide 14 was rapidly promoted by CuSO4. A ruthenium-catalyzed dehydrative amidation procedure using azides and alcohols, such as the reaction of 15 with phenylethanol to produce 16, was reported (Org. Lett. 2012, 14, 6028) by Soon Hyeok Hong at Seoul National University. An alternative oxidative amidation was developed (Tetrahedron Lett. 2012, 53, 6479) by Chengjian Zhu at Nanjing University and the Shanghai Institute of Organic Chemistry who utilized catalytic tetrabutylammonium iodide and disubstituted formamides to convert alcohols such as 17 to amides 18. A redox catalysis strategy was developed (Angew. Chem. Int. Ed. 2012, 51, 12036) by Brandon L. Ashfeld at Notre Dame for the triphenylphosphine-catalyzed Staudinger ligation of carboxylic acid 19 to furnish amide 20. For direct catalytic amidation of carboxylic acids and amines such as in the conversion of 21 to 23, Dennis G. Hall at the University of Alberta reported (J. Org. Chem. 2012, 77, 8386) that the boronic acid 22 was a highly effective catalyst that operated at room temperature.

C–O Ring Construction: The Oger/Lee/Galano Synthesis of 7(RS)-ST-Δ8-11-dihomo-Isofuran

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Ring Expansion ◽  
Radical Mechanism ◽  
Columbia University ◽  
University Of Michigan ◽  
Max Planck ◽  
University Of British Columbia ◽  
University Of Technology ◽  
National University ◽  
Seoul National University ◽  
The University

Shaorong Yang and Huanfeng Jiang of the South China University of Technology assembled (Angew. Chem. Int. Ed. 2014, 53, 7219) the β-lactone 3 by the Pd-catalyzed addition of 2 to the alkyne 1. Jack R. Norton of Columbia University observed (J. Am. Chem. Soc. 2015, 137, 1036) that the vanadium-mediated reduc­tive cyclization of 4 proceeded by a free radical mechanism, leading to the cis 3,4-disubstituted tetrahydrofuran 5. The cyclization of 6 to 7 developed (J. Org. Chem. 2015, 80, 965) by Glenn M. Sammis of the University of British Columbia also involved H atom transfer. Amy R. Howell of the University of Connecticut devised (J. Org. Chem. 2015, 80, 5196) the ring expansion of the β-lactone 8 to the tet­rahydrofuran 9. Dmitri V. Filippov and Jeroen D. C. Codée of Leiden University showed (J. Org. Chem. 2015, 80, 4553) that the net reductive alkylation of the lac­tone 10 led to 11 with high diastereocontrol. A. Stephen K. Hashmi of the Ruprecht-Karls-Universität Heidelberg optimized (Chem. Eur. J. 2015, 21, 427) the gold-mediated rearrangement of the ester 12 to the lactone 13. This reaction apparently proceeded by the coupling of the metalated lac­tone with a propargylic carbocationic species. Benjamin List of the Max-Planck-Institut für Kohlenforschung developed (Angew. Chem. Int. Ed. 2015, 54, 7703) an organocatalyst that mediated the addition of 15 to 14, leading to 16 in high ee. Scott E. Denmark of the University of Illinois published (Nature Chem. 2015, 6, 1056) a detailed study of the enantioselective cyclization of 17 to 18. Shunichi Hashimoto of Hokkaido University established (Tetrahedron Lett. 2015, 56, 1397) that his catalyst was effective for the cycli­zation of 19 to 20. Debendra K. Mohapatra of the Indian Institute of Chemical Technology showed (J. Org. Chem. 2015, 80, 1365) that allyl trimethylsilane could trap the intermediate from the cyclization of 21, leading to 22 with high diastereocontrol. Young-Ger Suh of Seoul National University used (Chem. Commun. 2015, 51, 9026) a Pd catalyst to cyclize 23 to (−)-deguelin 24. John Montgomery of the University of Michigan showed (Org. Lett. 2015, 17, 1493) that the Ni-catalyzed reduc­tive cyclization of 25 to 26 proceeded with high diastereoselectivity.

New Methods for Reduction and for Oxidation

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Carboxylic Acid ◽  
Primary Alcohol ◽  
Direct Oxidation ◽  
University Of Florida ◽  
Co Catalyst ◽  
Princeton University ◽  
National University ◽  
Texas Tech University ◽  
Seoul National University ◽  
The University

Clemens Krempner of Texas Tech University devised (Chem. Eur. J. 2014, 20, 14959) a very active Al catalyst for the Meerwein-Ponndorf-Verley reduction of a ketone 1 to the alcohol 2. Louis Fensterbank and Cyril Ollivier of UMPC and Jean-Philippe Goddard of the Université de Haute-Alsace showed (Adv. Synth. Catal. 2014, 356, 2756) that visible light could mediate the reduction of the O-thiocarbamate 3 to 4. Soon Hyeok Hong of Seoul National University used (Org. Lett. 2014, 16, 4404) hydrogen from the diol 6 to reduce the nitrile 5, leading directly to the protected amine 7. Alex Adronov of McMaster University (J. Org. Chem. 2014, 79, 7728) and Thibault Cantat of Gif- sur-Yvette (Chem. Commun. 2014, 50, 9349) observed that an aryl amide 8 could be reduced to the amine 9 under conditions that left alkyl amides unchanged. Paul J. Chirik of Princeton University developed (J. Am. Chem. Soc. 2014, 136, 13178) a Co catalyst for the alcohol- directed reduction of a proximal alkene, converting 10 selectively to 11. Yoichiro Kuninobu and Motomu Kanai of the University of Tokyo used (Synlett 2014, 25, 1869) stoichiometric Mo(CO)₆ to desulfurize 12 to 13. Utpal Bora of Tezpur University oxidized (Tetrahedron Lett. 2014, 55, 5029) the alcohol 14 to the aldehyde 15 with t-butyl hydroperoxide, using the inexpensive and reusable VOSO₄ as the catalyst. The oxidation of an alcohol to the acid is often car­ried out in two steps, alcohol to aldehyde and aldehyde to carboxylic acid. Kenneth B. Wagener of the University of Florida developed (Tetrahedron Lett. 2014, 55, 4452) a protocol for the direct oxidation of an alcohol 16 to the acid 17. Prodeep Phukan of Gauhati University devised (Tetrahedron Lett. 2014, 55, 5358) a catalyst-free procedure for the oxidation of a primary alcohol 18 to the ester 19. The aldehyde cor­responding to 18 (not illustrated) was also efficiently oxidized to 19. Katsuhiko Moriyama and Hideo Togo of Chiba University effected (Org. Lett. 2014, 16, 3812) the oxidative debenzylation of 20 to the ketone 21.

PEDIATRICS IN THE REPUBLIC OF KOREA

PEDIATRICS ◽  
1960 ◽  
Vol 26 (4) ◽  
pp. 696-699
Author(s):  
Eldon B. Berglund
Keyword(s):  
United States ◽  
Public Administration ◽  
The United States ◽  
Republic Of Korea ◽  
University Of Minnesota ◽  
National University ◽  
The Republic ◽  
Seoul National University ◽  
The University

In The spring of 1959, Dr. John Anderson, Professor of Pediatrics at the University of Minnesota, asked me to go to Korea as adviser in pediatrics to Seoul National University. The University of Minnesota has a contract with the United States Operations Mission (USOM) to help rehabilitate Seoul National University in the schools of Agriculture, Public Administration, Engineering and Medicine. This contract has been in effect since 1954, has involved the spending of several millions of dollars, the sending of medical advisers from Minnesota to Seoul and of medical participants, as they are called, from Seoul National University (SNU) to the University of Minnesota.

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