Organocatalyzed C–C Ring Construction: The Mihovilovic Synthesis of Piperenol B

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
State University ◽  
Air Oxidation ◽  
Microbial Oxidation ◽  
Max Planck ◽  
National Chemical Laboratory ◽  
Chemical Laboratory ◽  
Northwestern University ◽  
National University ◽  
The University ◽  
Oregon State University

M. Kevin Brown of Indiana University prepared (J. Am. Chem. Soc. 2015, 137, 3482) the cyclobutane 3 by the organocatalyzed addition of 2 to the alkene 1. Karl Anker Jørgensen of Aarhus University assembled (J. Am. Chem. Soc. 2015, 137, 1685) the complex cyclobutane 7 by the addition of 5 to the acceptor 4, followed by conden­sation with the phosphorane 6. Zhi Li of the National University of Singapore balanced (ACS Catal. 2015, 5, 51) three enzymes to effect enantioselective opening of the epoxide 8 followed by air oxidation to 9. Gang Zhao of the Shanghai Institute of Organic Chemistry and Zhong Li of the East China University of Science and Technology added (Org. Lett. 2015, 17, 688) 10 to 11 to give 12 in high ee. Akkattu T. Biju of the National Chemical Laboratory combined (Chem. Commun. 2015, 51, 9559) 13 with 14 to give the β-lactone 15. Paul Ha-Yeon Cheong of Oregon State University and Karl A. Scheidt of Northwestern University reported (Chem. Commun. 2015, 51, 2690) related results. Dieter Enders of RWTH Aachen University constructed (Chem. Eur. J. 2015, 21, 1004) the complex cyclopentane 20 by the controlled com­bination of 16, 17, and 18, followed by addition of the phosphorane 19. Derek R. Boyd and Paul J. Stevenson of Queen’s University Belfast showed (J. Org. Chem. 2015, 80, 3429) that the product from the microbial oxidation of 21 could be protected as the acetonide 22. Ignacio Carrera of the Universidad de la República described (Org. Lett. 2015, 17, 684) the related oxidation of benzyl azide (not illustrated). Manfred T. Reetz of the Max-Planck-Institut für Kohlenforschung and the Philipps-Universität Marburg found (Angew. Chem. Int. Ed. 2014, 53, 8659) that cytochrome P450 could oxidize the cyclohexane 23 to the cyclohexanol 24. F. Dean Toste of the University of California, Berkeley aminated (J. Am. Chem. Soc. 2015, 137, 3205) the ketone 25 with 26 to give 27. Benjamin List, also of the Max-Planck-Institut für Kohlenforschung, reported (Synlett 2015, 26, 1413) a parallel investigation. Philip Kraft of Givaudan Schweiz AG and Professor List added (Angew. Chem. Int. Ed. 2015, 54, 1960) 28 to 29 to give 30 in high ee.

Diels-Alder Cycloaddition: (+)-Armillarivin (Banwell), Gelsemiol (Gademann), (+)-Frullanolide (Liao), Myceliothermophin A (Uchiro), Peribysin E (Reddy), Caribenol A (Li/Yang)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Elevated Pressure ◽  
Diels Alder ◽  
Cope Rearrangement ◽  
National Chemical Laboratory ◽  
Chemical Laboratory ◽  
Enantiomerically Pure ◽  
Peking University ◽  
National University ◽  
Diastereoselective Addition ◽  
The University

Martin G. Banwell of the Australian National University prepared (Org. Lett. 2013, 15, 1934) the enantiomerically pure diol 1 by fermentation of the aromatic precursor. Diels-Alder addition of cyclopentenone 2 proceeded well at elevated pressure to give 3, the precursor to (+)-armillarivin 4. Karl Gademann of the University of Basel found (Chem. Eur. J. 2013, 19, 2589) that the Diels-Alder addition of 6 to 5 proceeded best without solvent and with Cu catalysis to give 7. Reduction under free radical conditions led to gelsemiol 8. Chun-Chen Liao of the National TsingHua University carried out (Org. Lett. 2013, 15, 1584) the diastereoselective addition of 10 to 9. A later oxy-Cope rearrangement established the octalin skeleton of (+)-frullanolide 12. D. Srinivasa Reddy of CSIR-National Chemical Laboratory devised (Org. Lett. 2013, 15, 1894) a strategy for the construction of the angularly substituted cis-fused aldehyde 15 based on Diels-Alder cycloaddition of 14 to the diene 13. Further transformation led to racemic peribysin-E 16. An effective enantioselective catalyst for dienophiles such as 14 has not yet been developed. Hiromi Uchiro of the Tokyo University of Science prepared (Tetrahedron Lett. 2012, 53, 5167) the bicyclic core of myceliothermophin A 19 by BF3•Et2O-promoted cyclization of the tetraene 17. The single ternary center of 17 mediated the formation of the three new stereogenic centers of 18, including the angular substitution. En route to caribenol A 22, Chuang-Chuang Li and Zhen Yang of the Peking University Shenzen Graduate School assembled (J. Org. Chem. 2013, 78, 5492) the triene 20 from two enantiomerically pure precursors. Inclusion of the radical inhibitor BHT sufficed to suppress competing polymerization, allowing clean cyclization to 21. Methylene blue has also been used (J. Am. Chem. Soc. 1980, 102, 5088) for this purpose.

Organocatalyzed C–C Ring Construction: The Bradshaw/Bonjoch Synthesis of (−)-Cermizine B

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
San Antonio ◽  
Bond Formation ◽  
Bryn Mawr ◽  
National Chemical Laboratory ◽  
Chemical Laboratory ◽  
Enantiomerically Pure ◽  
University Of Texas ◽  
National University ◽  
Institute Of Technology ◽  
The University

In a continuation of his studies (OHL20141229, OHL20140811) of organocatalyzed 2+2 photocycloaddition, Thorsten Bach of the Technische Universität München assembled (Angew. Chem. Int. Ed. 2014, 53, 7661) 3 by adding 2 to 1. Li-Xin Wang of the Chengdu Institute of Organic Chemistry also used (Org. Lett. 2014, 16, 6436) an organocatalyst to effect the addition of 5 to 4 to give 6. Shuichi Nakamura of the Nagoya Institute of Technology devised (Org. Lett. 2014, 16, 4452) an organocatalyst that mediated the enantioselective opening of the aziridine 7 to 8. Zhi Li of the National University of Singapore cloned (Chem. Commun. 2014, 50, 9729) an enzyme from Acinetobacter sp. RS1 that reduced 9 to 10. Gregory C. Fu of Caltech developed (Angew. Chem. Int. Ed. 2014, 53, 13183) a phosphine catalyst that directed the addition of 12 to 11 to give 13. Armido Studer of the Westfälische Wilhelms-Universität Münster showed (Angew. Chem. Int. Ed. 2014, 53, 9622) that 15 could be added to 14 to give 16 in high ee. Akkattu T. Biju of CSIR-National Chemical Laboratory described (Chem. Commun. 2014, 50, 14539) related results. The photostimulated enantioselective ketone alkylation developed (Chem. Sci. 2014, 5, 2438) by Paolo Melchiorre of ICIQ was powerful enough to enable the alkyl­ation of 17 with 18 to give 19, overcoming the stereoelectronic preference for axial bond formation. David W. Lupton of Monash University established (J. Am. Chem. Soc. 2014, 136, 14397) the organocatalyzed transformation of the dienyl ester 20 to 21. James McNulty of McMaster University added (Angew. Chem. Int. Ed. 2014, 53, 8450) azido acetone 23 to 22 to give 24 in high ee. There are sixteen enantiomerically-pure diastereomers of the product 27. John C.-G. Zhao of the University of Texas at San Antonio showed (Angew. Chem. Int. Ed. 2014, 53, 7619) that with the proper choice of organocatalyst, with or without subsequent epimerization, it was possible to selectively prepare any one of eight of those diastereomers by the addition of 26 to 25. William P. Malachowski of Bryn Mawr College showed (Tetrahedron Lett. 2014, 55, 4616) that 28, readily prepared by a Birch reduction protocol, was converted by heating followed by exposure to catalytic Me3P to the angularly-substituted octalone 29.

Reactions of Alkenes: The Usami Synthesis of (−)-Pericosine E

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Aldol Condensation ◽  
Indian Institute ◽  
Ortho Position ◽  
State University ◽  
Air Oxidation ◽  
National Chemical Laboratory ◽  
Chemical Laboratory ◽  
Georgia State University ◽  
Institute Of Technology ◽  
La Jolla

Dasheng Leow of the National Tsing Hua University used (Eur. J. Org. Chem. 2014, 7347) photolysis to activate the air oxidation of hydrazine to generate diimide, that then reduced 1 selectively to 2. Kevin M. Peese of Bristol-Myers Squibb effected (Org. Lett. 2014, 16, 4444) ring-closing metathesis of 3 followed by in situ reduction to form 4. Jitendra K. Bera of the Indian Institute of Technology Kanpur effected (J. Am. Chem. Soc. 2014, 136, 13987) gentle oxidative cleavage of cyclooctene 5 to the dialde­hyde 6. Arumugam Sudalai of the National Chemical Laboratory observed (Org. Lett. 2014, 16, 5674) high regioselectivity in the oxidation of the alkene 7 to the ketone 8. Hao Xu of Georgia State University also observed (J. Am. Chem. Soc. 2014, 136, 13186) high regioselectivity in the oxidation of the alkene 9 with 10, leading to the urethane 11. Justin Du Bois of Stanford University developed (J. Am. Chem. Soc. 2014, 136, 13506) mild conditions for the net double amination of the alkene 12 with 13, leading to 14. Jiaxi Xu and Pingfan Li of the Beijing University of Chemical Technology devised (Org. Lett. 2014, 16, 6036) a protocol for the allylic thiomethylation of an alkene with 16, converting 15 to 17. Matthias Beller of the Leibniz-Institüt für Katalyse combined (Chem. Eur. J. 2014, 20, 15692) hydroformylation, aldol condensation, and reduction to convert the alkene 18 to the ketone 19. Phil S. Baran of Scripps/La Jolla added (Angew. Chem. Int. Ed. 2014, 53, 14382) the diazo dienone 21 to the alkene 20 to give, after exposure to HCl, the arylated product 22. Markus R. Heinrich of the Friedrich-Alexander-Universität Erlangen-Nürnberg employed (Chem. Eur. J. 2014, 20, 15344) Selectfluor as both an oxidizing and a fluorinating agent in the related addition of 24 to 23 to give 25. Debabrata Maiti at the Indian Institute of Technology Bombay activated (J. Am. Chem. Soc. 2014, 136, 13602) the ortho position of 27, then added that interme­diate to 26 to give 28.

Functional Group Protection: The Pohl Synthesis of β-1,4-Mannuronate Oligomers

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Iron Catalyst ◽  
Gold Catalyst ◽  
State University ◽  
Allyl Ester ◽  
National Chemical Laboratory ◽  
Chemical Laboratory ◽  
Benzyl Ethers ◽  
Institute Of Technology ◽  
Tokyo Medical ◽  
The University

D. Srinivasa Reddy of the National Chemical Laboratory converted (Org. Lett. 2015, 17, 2090) the selenide 1 to the alkene 2 under ozonolysis conditions. Takamitsu Hosoya of the Tokyo Medical and Dental University found (Chem. Commun. 2015, 51, 8745) that even highly strained alkynes such as 4 can be generated from a sulfinyl vinyl triflate 3. An alkyne can be protected as the dicobalt hexacarbonyl complex. Joe B. Gilroy and Mark S. Workentin of the University of Western Ontario found (Chem. Commun. 2015, 51, 6647) that following click chemistry on a non-protected distal alkyne, deprotection of 5 to 6 could be effected by exposure to TMNO. Stefan Bräse of the Karlsruhe Institute of Technology and Irina A. Balova of Saint Petersburg State University showed (J. Org. Chem. 2015, 80, 5546) that the bend of the Co complex of 7 enabled ring-closing metathesis, leading after deprotection to 8. Morten Meldal of the University of Copenhagen devised (Eur. J. Org. Chem. 2015, 1433) 9, the base-labile protected form of the aldehyde 10. Nicholas Gathergood of Dublin City University and Stephen J. Connon of the University of Dublin developed (Eur. J. Org. Chem. 2015, 188) an imidazolium catalyst for the exchange deprotection of 11 to 13, with the inexpensive aldehyde 12 as the acceptor. Peter J. Lindsay-Scott of Eli Lilly demonstrated (Org. Lett. 2015, 17, 476) that on exposure to KF, the isoxa­zole 14 unraveled to the nitrile 15. Masato Kitamura of Nagoya University observed (Tetrahedron 2015, 71, 6559) that the allyl ester of 16 could be removed to give 17, with the other alkene not affected. Benzyl ethers are among the most common of alcohol protecting groups. Yongxiang Liu and Maosheng Cheng of Shenyang Pharmaceutical University showed (Adv. Synth. Catal. 2015, 357, 1029) that 18 could be converted to 19 simply by expo­sure to benzyl alcohol in the presence of a gold catalyst. Reko Leino of Åbo Akademi University developed (Synthesis 2015, 47, 1749) an iron catalyst for the reductive benzylation of 20 to 21. Related results (not illustrated) were reported (Org. Lett. 2015, 17, 1778) by Chae S. Yi of Marquette University.

Organocatalytic C-C Ring Construction: (+)-Ricciocarpin A (List) and (-)-Aromadendranediol (MacMillan)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Aldol Condensation ◽  
Catalytic Amount ◽  
Heterocyclic Carbenes ◽  
University Of Pennsylvania ◽  
State University ◽  
Max Planck ◽  
Mannich Condensation ◽  
The University ◽  
Oregon State University ◽  
Prochiral Ketone

Yoshiji Takemoto of Kyoto University designed (Organic Lett. 2009, 11, 2425) an organocatalyst for the enantioselective conjugate addition of alkene boronic acids to γ-hydroxy enones, leading to 1 in high ee. Attempted Mitsunobu coupling led to the cyclopropane 2, while bromoetherification followed by intramolecular alkylation delivered the cyclopropane 3. Jeffrey W. Bode of the University of Pennsylvania demonstrated (Organic Lett. 2009, 11, 677) a remarkable dichotomy in the reactivity of N-heterocyclic carbenes. A triazolium precatalyst combined 4 and 5 to give 6, whereas an imidazolium precatalyst combined 4 and 5 to give 7. Xinmiao Liang of the Dalian Institute of Chemical Physics and Jinxing Ye of the East China University of Science and Technology devised (Organic Lett. 2009, 11, 753) a Cinchona -derived catalyst that converted the prochiral cyclohexenone 8 into the diester 10 in high ee. Rich G. Carter of Oregon State University found (J. Org. Chem. 2009, 74, 2246) a simple sulfonamide-based proline catalyst that effected the Mannich condensation of the prochiral ketone with ethyl glyoxalate 12 and the amine 13, leading to the amine 14. In the first pot of a concise, three-pot synthesis of (-)-oseltamivir, Yujiro Hayashi of the Tokyo University of Science combined (Angew. Chem. Int. Ed. 2009, 48, 1304) 15 and 16 in the presence of a catalytic amount of diphenyl prolinol TMS ether to give an intermediate nitro aldehyde. Addition of the phosphonate 17 led to a cyclohexenecarboxylate, that on the addition of the thiophenol 18 equilibrated to the ester 19. Ying-Chun Chen of Sichuan University used (Organic Lett. 2009, 11, 2848) a related diaryl prolinol TMS ether to direct the condensation of the readily-prepared phosphorane 20 with the unsaturated aldehyde 21 to give the cyclohexenone 22. Armando Córdova of Stockholm University also used (Tetrahedron Lett. 2009, 50, 3458) diphenyl prolinol TMS ether to mediate the addition of 24 to 23. The subsequent intramolecular aldol condensation proceeded with high diastereocontrol, leading to 25. Benjamin List of the Max-Planck Institut, Mülheim employed (Nat. Chem. 2009, 1, 225) a MacMillan catalyst for the reductive cyclization of 26.

Enantioselective Organocatalytic C-C Ring Construction

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Catalyst System ◽  
Max Planck ◽  
Cascade Cyclizations ◽  
Silyl Enol Ether ◽  
Northwestern University ◽  
National University ◽  
University Of Oslo ◽  
Robinson Annulation ◽  
The University

Ming Yan of Sun Yat-sen University, Guangzhou, optimized (Synlett 2010, 266) the organocatalyzed addition of 2 to a cyclic enone 1, establishing the cyclopropane 3 with high diastereo- and enantiocontrol. Benjamin List of the Max-Planck-Institut Mülheim devised (Angew. Chem. Int. Ed. 2010, 49, 4136) an organocatalyst for the enantioselective methanolysis of the anhydride 4. Other ring sizes worked as well. Hisashi Yamamoto of the University of Chicago reported (Organic Lett. 2010, 12, 2476) the organocatalyzed addition of the ketone silyl enol ether 6 to the aldehyde 7, to give the syn aldol product 8 in high ee. Gang Zhao of the University of Science and Technology, Hefei, established (Angew. Chem. Int. Ed. 2010, 49, 4467) an organocatalyst for the enantioselective addition of the allene ester 10 to 9. Marcus A. Tius of the University of Hawaii uncovered (J. Am. Chem. Soc. 2010, 132, 8266) conditions for the enantioselective Nazarov cyclization of 12 to 13. Karl A. Scheidt of Northwestern University devised (Organic Lett. 2010, 12, 2830) an easily scaled protocol for the cyclization of the prochiral diketone 14 to the β-lactone 15. Thermolysis then converted 15 to the corresponding cyclopentene. Yixin Lu of the National University of Singapore showed (Organic Lett. 2010, 12, 2278) that the simple combination of commercial cinchonidine with (+)-camphorsulfonic acid gave a catalyst that effected the room-temperature conjugate addition of 16 to 1. Hiyoshizo Kotsuki of Kochi University combined (Organic Lett. 2010, 12, 1616) 1,2-diaminocyclohexane with cyclohexane-1,2-bis carboxylate to give a similarly simple catalyst system, that effected Robinson annulation of 18 to 20. Binding an organocatalyst to a polymer simplifies recovery and reuse. Tore Hansen of the University of Oslo reported (J. Org. Chem. 2010, 75 , 1620) a bottom-up approach to such polymer-bound catalysts. The bound proline worked well for the condensation of 21 with 22. The corresponding polymeric diphenyl OTMS (Jørgensen-Hayashi) catalyst was sluggish, but it effected the three-component coupling of 24, 25, and 26 in high ee. Two cascade cyclizations warrant particular mention. The racemic cyclization of 28 is expected to be facile in the presence of HCl.

New Methods for C-C Bond Construction: The Burke Synthesis of (-)-Peridinin

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Ohio State University ◽  
Florida State University ◽  
State University ◽  
University Of Kansas ◽  
University Of Mississippi ◽  
Max Planck ◽  
Enantiomerically Pure ◽  
University Of Wisconsin ◽  
Northwestern University ◽  
The University

Hideki Yorimitsu and Koichiro Oshima of Kyoto University observed (J. Am. Chem. Soc. 2010, 132, 8878) that Rh-catalyzed addition of 2 to a terminal allene 1 generated an allylic organometallic, which coupled with electrophiles to give the branched product 3. Regan J. Thomson of Northwestern University devised (Nat. Chem. 2010, 2, 294) the reagent 5, which added to an aldehyde 4 to give the reduced allylically coupled product 6. Nuno Maulide of the Max-Planck-Institut, Mülheim, noted (Angew. Chem. Int. Ed. 2010, 49, 1583) the remarkable rearrangement of 7 to 8. Jon A. Tunge of the University of Kansas showed (Organic Lett. 2010, 12, 740) that nitronate allylation could be effected by the Pd-mediated decarboxylation of 9. Takashi Tomioka of the University of Mississippi developed (Organic Lett. 2010, 12, 2171) a convenient reagent for the conversion of an aldehyde 11 to the Z -unsaturated nitrile 12 . Xiaodong Shi of the University of West Virginia established (Organic Lett. 2010, 12, 2088) that Au-mediated rearrangement of 13 led to the Z -iodo enone 14. T. V. RajanBabu of Ohio State University developed (Organic Lett. 2010, 12, 2622) a Pd catalyst for the selective double functionalization of a terminal alkyne 15 to the stannane 16. The subsequent tandem Stille and Suzuki couplings proceeded efficiently. The controlled construction of tetrasubstituted alkenes is particularly challenging. Kohei Endo and Takanori Shibata of Waseda University put forward (J. Org. Chem. 2010, 75, 3469) what promises to be a general solution to this problem: the addition of the bis-boronate 17 to a ketone 18. Alkynes are usually prepared by direct alkylation. Gérard Cahiez of the Université de Paris 13 established (Angew. Chem. Int. Ed. 2010, 49, 1278) an alternative: the coupling of a Grignard reagent with a 1-bromoalkyne 20. Gregory B. Dudley of Florida State University developed (J. Org. Chem. 2010, 75, 3260) a complementary route to internal alkynes based on the fragmentation of 22. Enantiomerically pure allenes are ubiquitous components of physiologically active natural products. Weiping Tang of the University of Wisconsin optimized (J. Am. Chem. Soc. 2010, 132, 3664) the bromolactonization of a Z enyne 24 to give the allene 25.

scholarly journals Why Age Matters to Higher Education: Age-Friendly Tools and Techniques for Culture Change

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 551-551
Author(s):  
David Burdick ◽  
Karen Rose ◽  
Dana Bradley
Keyword(s):  
University Presidents ◽  
Steering Committee ◽  
State University ◽  
Community Members ◽  
University Leadership ◽  
Drexel University ◽  
College Of Nursing ◽  
Tools And Techniques ◽  
The University ◽  
Oregon State University

Abstract Momentum is growing for the Age-Friendly University Network as proponents, primarily gerontology educators, have successfully encouraged university presidents to sign nonbinding pledged to become more age-friendly in programs and policies, endorsing 10 Age-Friendly University Principles. While this trend is inspiring, more is needed to fully achieve benefits for universities, students, communities, and older adults. Four presentations discuss innovative ways of deepening university commitment, weaving the principles into the fabric of the university. The first paper describes thematic content analysis from five focus groups with admissions and career services staff at Washington University in St. Louis and the recommendations that emerged for the provision of programs and services for post-traditional students. The second paper describes efforts to utilize community-impact internships and community partnerships to build support for Age-Friendly University initiatives at Central Connecticut State University, particularly in the context of the university’s recent Carnegie Foundation Engaged Campus designation. The third paper describes how Drexel University became Philadelphia’s first Age-Friendly University and current efforts in the Drexel College of Nursing and Heatlh Care Profession’s AgeWell Collaboratory to convene university-wide leadership for an AFU Steering Committee working on four mission-driven efforts to ensure AFU sustainability. The fourth paper describes steps taken by AFU proponents at Western Oregon State University to gain endorsement from university leadership and community, including mapping the 10 AFU Principles to the university’s strategic plan, faculty senate endorsement, and survey/interview results of older community members’ use of the university, which collectively have enhanced deeper and broader campus buy-in of AFU.

Transition Metal-Mediated Construction of Carbocycles: Dimethyl Gloiosiphone A (Takahashi), Pasteurestin A (Mulzer), and Pentalenene (Fox)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Transition Metal ◽  
South Florida ◽  
Health Science ◽  
Pt Catalyst ◽  
Max Planck ◽  
Au Catalyst ◽  
Ru Catalyst ◽  
National University ◽  
Rh Catalyst ◽  
The University

There continue to be new developments in transition metal- and lanthanide-mediated construction of carbocycles. Although a great deal has been published on the asymmetric cyclopropanation of styrene, relatively little had been reported for other classes of alkenes. Tae-Jeong Kim of Kyungpook National University has devised (Tetrahedron Lett. 2007, 48, 8014) a Ru catalyst for the cyclopropanation of simple α-olefins such as 1. X. Peter Zhang of the University of South Florida has developed (J. Am.Chem. Soc. 2007, 129, 12074) a Co catalyst for the cyclopropanation of alkenes such as 5 having electron-withdrawing groups. Alexandre Alexakis of the Université de Genève has reported(Angew. Chem. Int. Ed. 2007, 46, 7462) simple monophosphine ligands that enabled enantioselective conjugate addition to prochiral enones, even difficult substrates such as 8. Seunghoon Shin of Hanyang University has found (Organic Lett. 2007, 9, 3539) an Au catalyst that effected the diastereoselective cyclization of 10 to the cyclohexene 11, and Radomir N. Saicic of the University of Belgrade has carried out (Organic Lett. 2007, 9, 5063), via transient enamine formation, the diastereoselective cyclization of 12 to the cyclohexane 13. Alois Fürstner of the Max-Planck- Institut, Mülheim has devised (J. Am. Chem. Soc. 2007, 129, 14836) a Rh catalyst that cyclized the aldehyde 14 to the cycloheptenone 15. Some of the most exciting investigations reported in recent months have been directed toward the direct diastereo- and enantioselective preparation of polycarbocyclic products. Rai-Shung Liu of National Tsing-Hua University has extended (J. Org. Chem. 2007, 72, 567) the intramolecular Pauson-Khand cyclization to the epoxy enyne 16, leading to the 5-5 product 17. Michel R. Gagné of the University of North Carolina has devised (J. Am. Chem. Soc. 2007, 129, 11880) a Pt catalyst that smoothly cyclized the polyene 18 to the 6-6 product 19. Yoshihiro Sato of Hokkaido University and Miwako Mori of the Health Science University of Hokkaido have described (J. Am. Chem. Soc. 2007, 129, 7730) a Ru catalyst for the cyclization of 20 to the 5-6-5 product 21. Each of these processes proceeded with high diastereocontrol.

C-O Ring Containing Natural Products: Paeonilactone B (Taylor), Deoxymonate B (de la Pradilla), Sanguiin H-5 (Spring), Solandelactone A (White), Spirastrellolide A (Paterson)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Oxidative Coupling ◽  
Claisen Rearrangement ◽  
Cyclic Carbonate ◽  
Membered Ring ◽  
State University ◽  
Enantiomerically Pure ◽  
University Of Cambridge ◽  
Spirastrellolide A ◽  
The University ◽  
Oregon State University

Richard J. K. Taylor of the University of York has developed (Angew. Chem. Int. Ed. 2008, 47, 1935) the diasteroselective intramolecular Michael cyclization of phosphonates such as 2. Quenching of the cyclized product with paraformaldehyde delivered ( + )-Paeonilactone B 3. Roberto Fernández de la Pradilla of the CSIC, Madrid established (Tetrahedron Lett. 2008, 49, 4167) the diastereoselective intramolecular hetero Michael addition of alcohols to enantiomerically-pure acyclic sulfoxides such as 4 to give the allylic sulfoxide 5. Mislow-Evans rearrangement converted 5 into 6, the enantiomerically-pure core of Ethyl Deoxymonate B 7. The ellagitannins, represented by 10, are single atropisomers around the biphenyl linkage. David R. Spring of the University of Cambridge found (Organic Lett. 2008, 10, 2593) that the chiral constraint of the carbohydrate backbone of 9 directed the absolute sense of the oxidative coupling of the mixed cuprate derived from 9, leading to Sanguiin H-5 10 with high diastereomeric control. A key challenge in the synthesis of the solandelactones, exemplified by 14, is the stereocontrolled construction of the unsaturated eight-membered ring lactone. James D. White of Oregon State University found (J. Org. Chem. 2008, 73, 4139) an elegant solution to this problem, by exposure of the cyclic carbonate 11 to the Petasis reagent, to give 12. Subsequent Claisen rearrangement delivered the eight-membered ring lactone, at the same time installing the ring alkene of Solandelactone E 14. AD-mix usually proceeds with only modest enantiocontrol with terminal alkenes. None the less, Ian Paterson, also of the University of Cambridge, observed (Angew. Chem. Int. Ed. 2008, 47, 3016, Angew. Chem. Int. Ed. 2008, 47, 3021) that bis-dihydroxylation of the diene 17 proceeded to give, after acid-mediated cyclization, the bis-spiro ketal core 18 of Spirastrellolide A Methyl Ester 19 with high diastereocontrol.

Sign in / Sign up

Export Citation Format

Share Document