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.

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.

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.

C–O Ring Construction: The Tong Synthesis of (−)-Aculeatin A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
University Of Pittsburgh ◽  
Enantiomerically Pure ◽  
Complementary Approach ◽  
Single Diastereomer ◽  
Pure Alcohol ◽  
Peking University ◽  
Duke University ◽  
Purdue University ◽  
Leaving Groups ◽  
The University

Oxetanes are both interesting structural elements and activated leaving groups. James A. Bull of Imperial College London cyclized (Chem. Commun. 2014, 50, 5203) the tosylate 1 to the oxetane with LiHMDS, then alkylated the product using the same base to give 2. J. S. Yadav of CSIR-Indian Institute of Chemical Technology estab­lished (Org. Lett. 2014, 16, 836) conditions for the cyclization of 3 to 4. Hiroaki Sasai of Osaka University used (Chem. Commun. 2013, 49, 11224) a Pd(II)–Pd(IV) cycle to convert 5 to 6. Lauri Vares of the University of Tartu dem­onstrated (Tetrahedron Lett. 2014, 55, 3569) that the racemic epoxide 7, a mixture of diastereomers, could be cyclized to 8 as a single diastereomer in high ee. Alistair Boyer of the University of Glasgow converted (Org. Lett. 2014, 16, 1660) the tria­zole 9, prepared from the corresponding alkyne, to the intermediate 10, that could be hydrolyzed to the ketone or reduced to the amine. Subhas Chandra Roy of the Indian Association for the Cultivation of Science devised (Eur. J. Org. Chem. 2014, 2980) a Ti(III)- mediated cascade conjugate addition–cyclization for the assembly of 12 from 11. Paul E. Floreancig of the University of Pittsburgh reported (Angew. Chem. Int. Ed. 2014, 53, 4926) the highly diastereoselective reductive cyclization of 13 to 14. Arun K. Ghosh of Purdue University prepared (J. Org. Chem. 2014, 79, 5697) the ketone 16 from the enantiomerically-pure alcohol 15. Professor Ghosh also described (Org. Lett. 2014, 16, 3154) a complementary approach to tetrahydropyrans based on the hetero Diels–Alder addition of the alkynyl aldehyde 18 to the diene 17 to give 19. Xin-Shan Ye of Peking University found (J. Org. Chem. 2014, 79, 4676) that the alcohol 20 could be cyclized to 21 with NBS, and to the diastereomer with PhSeCl. Jiyong Hong of Duke University showed (Org. Lett. 2014, 16, 2406) that an organo­catalyst could be used to mediate the cyclization of 22 to the oxepane 23. Mingji Dai, also of Purdue University, reported (Angew. Chem. Int. Ed. 2014, 53, 6519) the car­bonylative macrocyclization of the diol 24 to the lactone 25.

New Methods for Carbocyclic Construction: The Kim Synthesis of Pentalenene

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Oxidative Cyclization ◽  
Enantiomerically Pure ◽  
University Of Oxford ◽  
Shanghai Institute ◽  
University Of Technology ◽  
Alkylidene Carbene ◽  
Oxidative Radical Cyclization ◽  
The University ◽  
Academy Of Sciences

Daesung Lee of the University of Illinois, Chicago, taking advantage of the facile insertion of an alkylidene carbene into a C-Si bond, established (J. Am. Chem. Soc. 2010, 132, 6640) a general method for the conversion of an α-silyl ketone 1 into the silyl cyclopropene 3. Christopher D. Bray of Queen Mary University showed (J. Org. Chem. 2010, 75, 4652) that the sulfonyl phosphonate 5 converted the enantiomerically pure epoxide 4 into the cyclopropane 6. Paul Margaretha of the University of Hamburg observed (Organic Lett. 2010, 12, 728) smooth photochemical combination of 7 and 8 to give 9 with high diastereocontrol. Tõnis Kanger of the Tallinn University of Technology devised (Organic Lett. 2010, 12, 2230) the three-component coupling of 10, 11, and diethyl amine to give, after reduction, the highly substituted cyclobutane 12. Min Shi of the Shanghai Institute of Organic Chemistry uncovered (J. Org. Chem. 2010, 75, 902) an interesting new thermal rearrangement: the conversion of 13 to 14. José G. Ávila-Zárraga of the Universidad Nacional Autónoma de México applied (Tetrahedron Lett. 2010, 51, 2232) Pd catalysis to the cyclization of the epoxy nitrile 15, redirecting the reaction from the expected cyclobutane to the cyclopentanol 16. Ullrich Jahn of the Academy of Sciences of the Czech Republic effected (J. Org. Chem. 2010, 75, 4480) the oxidative radical cyclization of 17 to 18. Initial deprotonation of the substrate with t -BuMgCl switched the product to the trans diastereomer. Jonathan W. Burton of the University of Oxford employed (Organic Lett. 2010, 12, 2738) a related oxidative cyclization for the diastereoselective conversion of 19 to 20. E. J. Corey of Harvard University reported (Organic Lett. 2010, 12, 300) a new ligand for the enantioselective Ni-mediated reduction of 21 to 22. Shu-Li You, also of the Shanghai Institute of Organic Chemistry, established (J. Am. Chem. Soc. 2010, 132, 4056) that the alcohol 23, readily prepared by oxidation of p -cresol, could be cyclized to the crystalline 25 in high ee.

Progress in Alkene and Alkyne Metathesis: (+)-5- epi -Citreoviral(Funk) and ( ± )-Poitediol (Vanderwal)

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Active Form ◽  
Catalytic Amount ◽  
Max Planck ◽  
Fischer Carbene ◽  
Cross Metathesis ◽  
Mo Catalyst ◽  
Peking University ◽  
Ru Complexes ◽  
University Of Zurich ◽  
The University

The Fischer carbene 2 at 0.5 mol % gives only 12% conversion of 1 to 4 after 18 hours. Debra J. Wallace of Merck Process showed (Adv. Synth. Cat. 2009, 351, 2277) that addition of a catalytic amount of the inexpensive 3 activated 2 , leading to 95% conversion of 1 to 4 after 18 hours. Shazia Zaman of the University of Canterbury and Andrew D. Abell of the University of Adelaide found (Tetrahedron Lett. 2009, 50, 5340) that the catalyst 5, incorporating a polyethylene glycol (PEG) chain, was readily recovered in active form by precipitation and could be reused at least fi ve times. Zhu Yinghuai of the Institute of Chemical and Engineering Sciences, Singapore (Adv. Synth. Cat. 2009, 351, 2650), and Chao Che, Zhen Yang, and Biwang Jiang of Peking University (Chem. Commun. 2009, 5990) independently described the preparation of Ru complexes such as 5 bound to magnetic nanoparticles. The catalysts were easily recycled and reused, leaving < 4 ppm Ru in the product. Reto Dorta of the University of Zurich reported (J. Am. Chem. Soc. 2009, 131, 9498) that the complex 6 (Ar = 2,7-diisopropylnaphthyl) was a separable mixture of syn- and anti-isomers. The very reactive anti-isomer at 50 ppm converted neat 1 into 2 in 2 hours at room temperature. Richard R. Schrock of MIT devised (J. Am. Chem. Soc. 2009, 131, 10840) an efficient Mo catalyst for a long-sought transformation—the ethenolysis of long-chain alkenes such as 7. Robert A. Stockman of the University of Nottingham developed (Chem. Commun. 2009, 4399) a related Ru-catalyzed procedure: cross-metathesis ring opening with methyl acrylate 11. Amir A. Hoveyda of Boston College, a coauthor on the Schrock paper, used (J. Am. Chem. Soc. 2009, 131, 10652) a very similar Mo catalyst for the rapid cross-metathesis of an alkyne with ethene, leading after subsequent ring-closing metathesis to products such as 14. Alois Fürstner of the Max-Planck-Institut, Mülheim, described (J. Am. Chem. Soc. 2009, 131, 9468) a well-characterized Mo nitride complex that efficiently catalyzed the conversion of 15 into 16. Samir Bouzbouz of the Université de Rouen and Janine Cossy of ESPCI ParisTech established (Organic Lett. 2009, 11, 5446) conditions for the metathesis of alkenes with the linchpin 18.

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.

scholarly journals A Brief History of the T4 Radiation Law

2009 ◽  
Author(s):  
John Crepeau
Keyword(s):  
Heat Exchange ◽  
Electromagnetic Radiation ◽  
Far Infrared ◽  
Working Fluid ◽  
Radiative Heat Exchange ◽  
Carnot Cycle ◽  
Max Planck ◽  
University Of Berlin ◽  
The Individual ◽  
The University

Since the 1700s, natural philosophers understood that heat exchange between two bodies was not precisely linearly dependent on the temperature difference, and that at high temperatures the discrepancy became greater. Over the years, many models were developed with varying degrees of success. The lack of success was due to the difficulty obtaining accurate experimental data, and a lack of knowledge of the fundamental mechanisms underlying radiation heat exchange. Josef Stefan, of the University of Vienna, compiled data taken by a number of researchers who used various methods to obtain their data, and in 1879 proposed a unique relation to model the dependence of radiative heat exchange on the temperature: the T4 law. Stefan’s model was met with some skepticism and was not widely accepted by his colleagues. His former student, Ludwig Boltzmann, who by then had taken a position at the University of Graz in Austria, felt that there was some truth to the empirical model proposed by his mentor. Boltzmann proceeded to show in 1884, treating electromagnetic radiation as the working fluid in a Carnot cycle, that in fact the T4 law was correct. By the time that Boltzmann published his thermodynamic derivation of the radiation law, physicists became interested in the fundamental nature of electromagnetic radiation and its relation to energy, specifically determining the frequency distribution of blackbody radiation. Among this group of investigators was Wilhelm Wien, working at Physikalisch-Technische Reichsanstalt in Charlottenburg, Berlin. He proposed a relation stating that the wavelength at which the maximum amount of radiation was emitted occurred when the product of the wavelength and the temperature was equal to a constant. This became known as Wien’s Displacement Law, which he deduced this by imagining an expanding and contracting cavity, filled with radiation. Later, he combined his Displacement Law with the T4 law to give a blackbody spectrum which was accurate over some ranges, but diverged in the far infrared. Max Planck, at the University of Berlin, built on Wien’s model but, as Planck himself stated, “the energy of radiation is distributed in a completely irregular manner among the individual partial vibrations...” This “irregular” or discrete treatment of the radiation became the basis for quantum mechanics and a revolution in physics. This paper will present brief biographies of the four pillars of the T4 radiation law, Stefan, Boltzmann, Wien and Planck, and outline the methodologies used to obtain their results.

Diels–Alder Cycloaddition: Pancratistatin (Cho), Nootkatone (Reddy), Platensimycin (Zhang/Lee), Scabronine G (Nakada), Isoglaziovianol (Trauner)

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Aldol Condensation ◽  
Diels Alder ◽  
Cancer Center ◽  
Columbia University ◽  
National Chemical Laboratory ◽  
Chemical Laboratory ◽  
Intramolecular Cycloaddition ◽  
Enantiomerically Pure ◽  
Peking University ◽  
The University

Samuel J. Danishefsky of Columbia University and the Memorial Sloan-Kettering Cancer Center made (Proc. Natl. Acad. Sci. 2013, 110, 10904) the unexpected obser­vation that methylation of the enolate derived from conjugate addition to the readily-prepared 1 followed by intramolecular alkene metathesis led to the trans fused ketone 2. This can be contrasted to the diastereo- and regioisomer 3, the product from Diels-Alder cycloaddition of 2-methylcyclohexenone to isoprene. The trans ring fusion of 2 is particularly significant because ozonolysis followed by aldol condensation would deliver the angularly-methylated trans-fused 6/5 C–D ring system of the steroids and related natural products. Cheon-Gyu Cho of Hanyang University added (Org. Lett. 2013, 15, 5806) the activated dienophile 4 to the dienyl lactone to give, after oxidation, the dibro­mide 5. Debromination followed by oxidation led to the antineoplastic lactam pancratistatin 6. D. Srinivasa Reddy of CSIR-National Chemical Laboratory Pune devised (J. Org. Chem. 2013, 78, 8149) a cascade protocol of Diels-Alder cycloaddition of 8 to the diene 7, followed by intramolecular aldol condensation, to give the enone 9. Oxidative manipulation followed by methylenation completed the synthesis of the commercially important grapefruit flavor nootkatone 10. Xinhao Zhang and Chi-Sing Lee of the Peking University Shenzen Graduate School uncovered (J. Org. Chem. 2013, 78, 7912) another cascade transformation, intermolecular addition of 11 to 12 followed by intramolecular Conia-ene cyclization, to give the tricyclic 13. Further manipulation led to an established intermediate for the total synthesis of platensimycin 14. Masahisa Nakada of Waseda University prepared (Angew. Chem. Int. Ed. 2013, 52, 7569) the enantiomerically-pure allene 15. Oxidation of the phenol to the monoketal of the cyclohexadienone set the stage for intramolecular cycloaddition to give 16. Oxidative cleavage followed by intramolecular alkene metathesis led to (+)-scabronine G 17. Dirk Trauner of the University of Munich assembled (Org. Lett. 2013, 15, 4324) the enantiomerically-pure alcohol 18. Oxidation gave the quinone, leading to intra­molecular Diels–Alder cycloaddition. The free alcohol then added to the exocyclic alkene of that product, to give, after further oxidation, the ether 19. Deprotection fol­lowed by reduction then completed the synthesis of (−)-isoglaziovianol 20.

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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