C–O Natural Products: (–)-Hybridalactone (Fürstner), (+)-Anthecotulide (Hodgson), (–)-Kumausallene (Tang), (±)-Communiol E (Kobayashi), (–)-Exiguolide (Scheidt), Cyanolide A (Rychnovsky)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Max Planck ◽  
Enantiomerically Pure ◽  
University Of Oxford ◽  
University Of Wisconsin ◽  
Favorskii Rearrangement ◽  
Alternative Approach ◽  
Ether Oxygen ◽  
Institute Of Technology ◽  
The University ◽  
Complementary Strategy

Control of the absolute configuration of adjacent alkylated stereogenic centers is a classic challenge in organic synthesis. In the course of the synthesis of (–)-hybridalactone 4, Alois Fürstner of the Max-Planck-Institut Mülheim effected (J. Am. Chem. Soc. 2011, 133, 13471) catalytic enantioselective conjugate addition to the simple acceptor 1. The initial adduct, formed in 80% ee, could readily be recrystallized to high ee. In an alternative approach to high ee 2,3-dialkyl γ-lactones, David M. Hodgson of the University of Oxford cyclized (Org. Lett. 2011, 13, 5751) the alkyne 5 to an aldehyde, which was condensed with 6 to give 7. Coupling with 8 then delivered (+)-anthecotulide 9. The enantiomerically pure diol 10 is readily available from acetylacetone. Weiping Tang of the University of Wisconsin dissolved (Org. Lett. 2011, 13, 3664) the symmetry of 10 by Pd-mediated cyclocarbonylation. The conversion of the lactone 11 to (–)-kumausallene 12 was enabled by an elegant intramolecular bromoetherification. Shoji Kobayshi of the Osaka Institute of Technology developed (J. Org. Chem. 2011, 76, 7096) a powerful oxy-Favorskii rearrangement that enabled the preparation of both four-and five-membered rings with good diastereocontrol, as exemplified by the conversion of 13 to 14. With the electron-withdrawing ether oxygen adjacent to the ester carbonyl, Dibal reduction of 14 proceeded cleanly to the aldehyde. Addition of ethyl lithium followed by deprotection completed the synthesis of (±)-communiol E. En route to (–)-exiguolide 18, Karl A. Scheidt of Northwestern University showed (Angew. Chem. Int. Ed. 2011, 50, 9112) that 16 could be cyclized efficiently to 17. The cyclization may be assisted by a scaffolding effect from the dioxinone ring. Dimeric macrolides such as cyanolide A 21 are usually prepared by lactonization of the corresponding hydroxy acid. Scott D. Rychnovsky of the University of California Irvine devised (J. Am. Chem. Soc. 2011, 133, 9727) a complementary strategy, the double Sakurai dimerization of the silyl acetal 19 to 20.

Alkenes

2017 ◽  
Author(s):  
Allison K. Griffith ◽  
Tristan H. Lambert
Keyword(s):  
State University ◽  
One Pot ◽  
Colorado State University ◽  
University Of Oxford ◽  
University Of British Columbia ◽  
University Of Wisconsin ◽  
Unsaturated Carbonyl Compound ◽  
Institute Of Technology ◽  
University Of Zurich ◽  
The University

The α-C–H functionalization of piperidine catalyzed by tantalum complex 1 to pro­duce amine 2 was developed (Org. Lett. 2013, 15, 2182) by Laurel L. Schafer at the University of British Columbia. An asymmetric diamination of diene 3 with diaziri­dine reagent 4 under palladium catalysis to furnish cyclic sulfamide 5 was developed (Org. Lett. 2013, 15, 796) by Yian Shi at Colorado State University. Enantioenriched β-fluoropiperdine 8 was prepared (Angew. Chem. Int. Ed. 2013, 52, 2469) via amino­fluorocyclization of 6 with hypervalent iodide 7, as reported by Cristina Nevado at the University of Zurich. Erick M. Carreira at ETH Zürich disclosed (J. Am. Chem. Soc. 2013, 135, 6814) a ruthenium-catalyzed hydrocarbamoylation of allylic formamide 9 to yield pyrrolidone 10. Hans-Günther Schmalz at the University of Köln disclosed (Angew. Chem. Int. Ed. 2013, 52, 1576) an asymmetric hydrocyanation of styrene 11 with Ni(cod)₂ and phosphine–phosphite ligand 12 to yield exclusively the branched cyanide 13. A simi­lar transformation of styrene 11 to the hydroxycarbonylated product 15 was catalyzed (Chem. Commun. 2013, 49, 3306) by palladium complex 14, as reported by Matthew L. Clarke at the University of St Andrews. Feng-Ling Qing at the Chinese Academy of Sciences found (Angew. Chem. Int. Ed. 2013, 52, 2198) that the hydrotrifluoromethylation of unactivated alkene 16 to 17 was catalyzed by silver nitrate. The same transformation was also reported (J. Am.Chem. Soc. 2013, 135, 2505) by Véronique Gouverneur at the University of Oxford using a ruthenium photocatalyst and the Umemoto reagent 18. Clark R. Landis at the University of Wisconsin, Madison reported (Angew. Chem. Int. Ed. 2013, 52, 1564) a one-pot asymmetric hydroformylation using 21 followed by Wittig olefination to transform alkene 19 into the γ-chiral α,β-unsaturated carbonyl compound 20. Debabrata Mati at the Indian Institute of Technology Bombay found (J. Am. Chem. Soc. 2013, 135, 3355) that alkene 22 could be nitrated stereoselectively with silver nitrite and TEMPO to form alkene 23. Damian W. Young at the Broad Institute disclosed (Org. Lett. 2013, 15, 1218) that a macrocyclic vinylsiloxane 24, which was synthesized via an E-selective ring clos­ing metathesis reaction, could be functionalized to make either E- or Z-alkenes, 25 and 26.

Enantioselective Construction of Alkylated Stereogenic Centers

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Ni Catalyst ◽  
Max Planck ◽  
Enantiomerically Pure ◽  
University Of Oxford ◽  
Princeton University ◽  
Oxidation Reduction ◽  
Single Diastereomer ◽  
Rh Catalyst ◽  
The University ◽  
Diastereomeric Excess

Carsten Bolm of RWTH Aachen developed (Angew. Chem. Int. Ed. 2008, 47, 8920) an Ir catalyst that effected hydrogenation of trisubstituted enones such as 1 with high ee. Benjamin List of the Max-Planck-Institut Mülheim devised (J. Am. Chem. Soc. 2008, 130, 13862) an organocatalyst for the enantioselective reduction of nitro acrylates such as 3 with the Hantzsch ester 4. Gregory C. Fu of MIT optimized (J. Am. Chem. Soc. 2008, 130, 12645) a Ni catalyst for the enantioselective arylation of propargylic halides such as 6. Both enantiomers of 6 were converted to the single enantiomer of 8. Michael C. Willis of the University of Oxford established (J. Am. Chem. Soc. 2008, 130, 17232) that hydroacylation with a Rh catalyst was selective for one enantiomer of the allene 9, delivering 11 in high ee. Similarly, José Luis García Ruano of the Universidad Autónoma de Madrid found (Angew. Chem. Int. Ed. 2008, 47, 6836) that one enantiomer of racemic 13 reacted selectively with the enantiomerically- pure anion 12, to give 14 in high diastereomeric excess. Ei-chi Negishi of Purdue University described (Organic Lett. 2008, 10, 4311) the Zr-catalyzed asymmetric carboalumination (ZACA reaction) of the alkene 15 to give the useful chiron 16. David W. C. MacMillan of Princeton University developed (Science 2008, 322, 77) an intriguing visible light-powered oxidation-reduction approach to enantioselective aldehyde alkylation. The catalytic chiral secondary amine adds to the aldehyde to form an enamine, that then couples with the radical produced by reduction of the haloester. Two other alkylations were based on readily-available chiral auxiliaries. Philippe Karoyan of the Université Pierre et Marie Curie observed (Tetrahedron Lett . 2008, 49, 4704) that the acylated Oppolzer camphor sultam 20 condensed with the Mannich reagent 21 to give 22 as a single diastereomer. Andrew G. Myers of Harvard University developed the pseudoephedrine chiral auxiliary of 23 to direct the construction of ternary alkylated centers. He has now established (J. Am. Chem. Soc. 2008, 130, 13231) that further alkylation gave 24, having a quaternary alkylated center, in high diastereomeric excess.

Stereocontrolled Carbocyclic Construction: The Trauner Synthesis of the Shimalactones

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Allylic Alcohols ◽  
Max Planck ◽  
Chiral Amine ◽  
Ene Reaction ◽  
Enantiomerically Pure ◽  
University Of Wisconsin ◽  
Single Diastereomer ◽  
Enantioselective Epoxidation ◽  
The University ◽  
Technological University

Benjamin List of the Max Planck Institute, Mülheim devised (J. Am. Chem. Soc. 2008, 130, 6070) a chiral primary amine salt that catalyzed the enantioselective epoxidation of cyclohexenone 1 . Larger ring and alkyl-substituted enones are also epoxidized with high ee. Three- and four-membered rings are versatile intermediates for further transformation. Tsutomu Katsuki of Kyushu University developed (Angew. Chem. Int. Ed. 2008, 47, 2450) an elegant Al(salalen) catalyst for the enantioselective Simmons-Smith cyclopropanation of allylic alcohols such as 3. Kazuaki Ishihara of Nagoya University found (J. Am. Chem. Soc. 2007, 129, 8930) chiral amine salts that effected enantioselective 2+2 cycloaddition of α-acyloxyacroleins such as 5 to alkenes to give the cyclobutane 7 with high enantio- and diastereocontrol. Gideon Grogan of the University of York overexpressed (Adv. Synth. Cat. 2008, 349, 916) the enzyme 6-oxocamphor hydrolase in E. coli . The 6-OCH so prepared converted prochiral diketones such as 8 to the cyclopentane 9 in high ee. Richard P. Hsung of the University of Wisconsin found (Organic Lett. 2008, 10, 661) that the carbene produced by oxidation of the ynamide 10 cyclized to 11 with high de. Teck-Peng Loh of Nanyang Technological University extended (J. Am. Chem. Soc. 2008, 130, 7194) butane-2,3-diol directed cyclization to the preparation of the cyclopentane 15. Note that sidechain relative configuration is also controlled. We established (J. Org. Chem. 2008, 73, 3467) that the thermal ene reaction of 17 delivered the tetrasubstituted cyclopentane 18 as a single diastereomer. Tony K. M. Shing of the Chinese University of Hong Kong devised (J. Org. Chem. 2007, 72, 6610) a simple protocol for the conversion of carbohydrate-derived lactones such as 19 to the highly-substituted, enantiomerically-pure cyclohexenone 21. Hiromichi Fujioka and Yasuyuki Kita of Osaka University established (Organic Lett. 2007, 9, 5605) a chiral diol-mediated conversion of the cyclohexadiene 22 to the diastereomerically pure cyclohexenone 24. Dirk Trauner, now of the University of Munich, reported (Organic Lett. 2008, 10, 149) an elegant assembly of the neuritogenic polyketide shimalactone A 28.

C–O Ring Construction: The Georg Synthesis of Oximidine II

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Max Planck ◽  
Enantiomerically Pure ◽  
Michael Adduct ◽  
University Of Oxford ◽  
Mo Catalyst ◽  
Peking University ◽  
Duke University ◽  
The Individual ◽  
The University ◽  
Academy Of Sciences

Chun-Bao Miao and Hai-Tao Yang of Changzhou University constructed (J. Org. Chem. 2011, 76, 9809) the oxetane 2 by exposing the Michael adduct 1 to I2 and air. Huanfeng Jiang of the South China University of Science and Technology carboxylated (Org. Lett. 2011, 13, 5520) the alkyne 3 in the presence of a nitrile to give the three-component coupled product 4. Alois Fürstner of the Max-Planck-Institut Mülheim cyclized (Angew. Chem. Int. Ed. 2011, 50, 7829) 5 with a Mo catalyst, released in situ from a stable precursor, to give 6 in high ee. Hiromichi Fujioka of Osaka University rearranged (Chem. Commun. 2011, 47, 9197) 7 to the cyclic aldehyde, largely as the less stable diastereomer 8. Edward A. Anderson of the University of Oxford cyclized (Angew. Chem. Int. Ed. 2011, 50, 11506) 9 to 10 with excellent stereochemical fidelity. Similarly, Michal Hocek of the Academy of Sciences of the Czech Republic, Andrei V. Malkov, now at Loughborough University, and Pavel Kocovsky of the University of Glasgow combined (J. Org. Chem. 2011, 76, 7781) the individual enantiomers of 11 and 12 to give 13 as single enantiomerically pure diastereomers. Daniel Romo of Texas A&M University cyclized (Angew. Chem. Int. Ed. 2011, 50, 7537) the bromo ester 14 to the lactone 15. Xin-Shan Ye of Peking University condensed (Synlett 2011, 2410) the sulfone 16 with 17 to give the sulfone 18, with high diastereocontrol. Jiyong Hong of Duke University found (Org. Lett. 2011, 13, 5816) that 19 could be cyclized to either diastereomer of 20 by judicious optimization of the reaction conditions. Stacey E. Brenner-Moyer of Brooklyn College showed (Org. Lett. 2011, 13, 6460) that cyclization of racemic 21 in the presence of 22 and the Hayashi catalyst delivered an ~1:1 mixture of 23 and 24, each with good stereocontrol. Kyoko Nakagawa-Goto of the University of North Carolina showed (Synlett 2011, 1413) that the MOM ether 25, prepared in high de by Evans alkylation, cyclized efficiently to 26. Armen Zakarian of the University of California Santa Barbara cyclized (Org. Lett. 2011, 13, 3636) 27, readily prepared in high ee by asymmetric Henry addition, to the enone 28.

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.

Other Methods for Carbocyclic Construction: The Porco Synthesis of (-)-Hyperibone K

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Oxidative Cyclization ◽  
Florida State University ◽  
State University ◽  
Colorado State University ◽  
Intramolecular Alkylation ◽  
University Of Wisconsin ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
University Of Bristol ◽  
The University

Varinder K. Aggarwal of the University of Bristol described (Angew. Chem. Int. Ed. 2010, 49, 6673) the conversion of the Sharpless-derived epoxide 1 into the cyclopropane 2. Christopher D. Bray of Queen Mary University of London established (Chem. Commun. 2010, 46, 5867) that the related conversion of 3 to 5 proceeded with high diastereocontrol. Javier Read de Alaniz of the University of California, Santa Barbara, extended (Angew. Chem. Int. Ed. 2010, 49, 9484) the Piancatelli rearrangement of a furyl carbinol 6 to allow inclusion of an amine 7, to give 8. Issa Yavari of Tarbiat Modares University described (Synlett 2010, 2293) the dimerization of 9 with an amine to give 10. Jeremy E. Wulff of the University of Victoria condensed (J. Org. Chem. 2010, 75, 6312) the dienone 11 with the commercial butadiene sulfone 12 to give the highly substituted cyclopentane 13. Robert M. Williams of Colorado State University showed (Tetrahedron Lett. 2010, 51, 6557) that the condensation of 14 with formaldehyde delivered the cyclopentanone 15 with high diastereocontrol. D. Srinivasa Reddy of Advinus Therapeutics devised (Tetrahedron Lett. 2010, 51, 5291) conditions for the tandem conjugate addition/intramolecular alkylation conversion of 16 to 17. Marie E. Krafft of Florida State University reported (Synlett 2010, 2583) a related intramolecular alkylation protocol. Takao Ikariya of the Tokyo Institute of Technology effected (J. Am. Chem. Soc. 2010, 132, 11414) the enantioselective Ru-mediated hydrogenation of bicyclic imides such as 18. This transformation worked equally well for three-, four-, five-, six-, and seven-membered rings. Stefan France of the Georgia Institute of Technology developed (Org. Lett. 2010, 12, 5684) a catalytic protocol for the homo-Nazarov rearrangement of the doubly activated cyclopropane 20 to the cyclohexanone 21. Richard P. Hsung of the University of Wisconsin effected (Org. Lett. 2010, 12, 5768) the highly diastereoselective rearrangement of the triene 22 to the cyclohexadiene 23. Strategies for polycyclic construction are also important. Sylvain Canesi of the Université de Québec devised (Org. Lett. 2010, 12, 4368) the oxidative cyclization of 24 to 25.

Metal-Mediated C–C Ring Construction: The Carreira Synthesis of (+)-Asperolide C

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Ring Expansion ◽  
Ethyl Acrylate ◽  
Heck Cyclization ◽  
University Of Oxford ◽  
Silyl Enol Ether ◽  
Emory University ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

Djamaladdin G. Musaev and Huw M. L. Davies of Emory University effected (Chem. Sci. 2013, 4, 2844) enantioselective cyclopropanation of ethyl acrylate 2 with the α-diazo ester 1 to give 3 in high ee. Philippe Compain of the Université de Strasbourg used (J. Org. Chem. 2013, 78, 6751) SmI2 to cyclize 4 to the cyclobutanol 5. Jianrong (Steve) Zhou of Nanyang Technological University effected (Chem. Commun. 2013, 49, 11758) enantioselective Heck addition of 7 to the prochiral ester 6 to give the cyclopentene 8. Liu-Zhu Gong of USTC, Hefei added (Org. Lett. 2013, 15, 3958) the Rh enolate from the enantioselective ring expansion of the α-diazo ester 9 to the nitroalkene 10, to give 11 in high de. Stephen P. Fletcher of the University of Oxford set (Angew. Chem. Int. Ed. 2013, 52, 7995) the cyclic quaternary center of 14 by the enantioselective conjugate addition to 12 of the alkyl zirconocene derived from 13. Alexandre Alexakis of the University of Geneva reported (Chem. Eur. J. 2013, 19, 15226) high ee from the conjugate addition of alkenyl Al reagents (not illustrated) to 12. Paultheo von Zezschwitz of Philipps-Universität Marburg prepared (Adv. Synth. Catal. 2013, 355, 2651) the silyl enol ether 17 by trapping the intermediate from the conjugate addition of 16 to 15. Stefan Bräse of the Karlsruhe Institute of Technology effected (Eur. J. Org. Chem. 2013, 7110) conjugate addition to the prochiral dienone 18 to give the highly substi­tuted cyclohexenone 19. Ping Tian and Guo-Qiang Lin of the Shanghai Institute of Organic Chemistry cyclized (J. Am. Chem. Soc. 2013, 135, 11700) 20 to the kinetic, less stable epimer of the diketone 21. Rh-mediated intramolecular C–H insertion has been a powerful tool for the con­struction of cyclopentane derivatives. Douglass F. Taber of the University of Delaware found (J. Org. Chem. 2013, 78, 9772) that the Rh carbene derived from 22 was dis­criminating enough to target the more nucleophilic C–H bond, leading to the cyclohexanone 23. Kozo Shishido of the University of Tokushima observed (Org. Lett. 2013, 15, 3666) high diastereoselectivity in the intramolecular Heck cyclization of 24 to 25.

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.

Alkylated Stereogenic Centers: The Jia Synthesis of (−)-Goniomitine

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Bimetallic Catalyst ◽  
The Other ◽  
Wild Type Enzyme ◽  
Enantiomerically Pure ◽  
Unsaturated Lactone ◽  
University Of Oxford ◽  
Stereogenic Centers ◽  
The University

John W. Wong of Pfizer and Kurt Faber of the University of Graz used (Adv. Synth. Catal. 2014, 356, 1878) a wild-type enzyme to reduce the nitrile 1 to 2 in high ee. Takafumi Yamagami of Mitsubishi Tanabe Pharma described (Org. Process Res. Dev. 2014, 18, 437) the practical diastereoselective coupling of the racemic acid 3 with the inexpensive pantolactone 4 to give, via the ketene, the ester 5 in high de. Takeshi Ohkuma of Hokkaido University devised (Org. Lett. 2014, 16, 808) a Ru/Li catalyst for the enantioselective addition of in situ generated HCN to an N-acyl pyrrole 6 to give 7 in high ee. Yujiro Hayashi of Tohoku University found (Chem. Lett. 2014, 43, 556) that an aldehyde 8 could be condensed with formalin, leading in high ee to the masked aldehyde 9. Stephen P. Fletcher of the University of Oxford prepared (Org. Lett. 2014, 16, 3288) the lactone 12 in high ee by adding an alkyl zirconocene, prepared from the alkene 11, to the unsaturated lactone 10. In a remarkable display of catalyst control, Masakatsu Shibasaki of the Institute of Microbial Chemistry and Shigeki Matsunaga of the University of Tokyo opened (J. Am. Chem. Soc. 2014, 136, 9190) the racemic aziridine 13 with malonate 14 using a bimetallic catalyst. One enantiomer of the aziridine was converted specifically to the branched product 15 in high ee. The other enantiomer of the aziridine was converted to the regioisomeric opening product. Kimberly S. Peterson of the University of North Carolina at Greensboro used (J. Org. Chem. 2014, 79, 2303) an enantiomerically-pure organophosphate to selec­tively deprotect the bis ester 16, leading to 17. Chunling Fu of Zhejiang University and Shengming Ma of the Shanghai Institute of Organic Chemistry showed (Chem. Commun. 2014, 50, 4445) that an organocatalyst could mediate the brominative oxi­dation of 18 to 19. The ee of the product was easily improved via selective crystalliza­tion of the derived dinitrophenylhydrazone. James P. Morken of Boston College developed (Org. Lett. 2014, 16, 2096) condi­tions for the allylation of an allylic acetate such as 20 with 21, to deliver the coupled product 22 with high maintenance of ee.

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