Stereoselective C-N Ring Construction

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Organic Chemistry ◽  
Diels Alder ◽  
Wolff Rearrangement ◽  
Enantiomerically Pure ◽  
Amino Esters ◽  
Shanghai Institute ◽  
Single Diastereomer ◽  
Peking University ◽  
Convenient Route ◽  
The University

Ryoichi Kuwano of Kyushu University showed (J. Am. Chem. Soc. 2008, 130, 808) that diastereomerically and enantiomerically pure pyrollidines such as 2 could be prepared by hydrogenation of the corresponding pyrrole. Victor S. Martín of Universidad de la Laguna found (Organic Lett. 2008, 10, 2349) that the stereochemical outcome of the pyrrolidine-forming Nicholas cyclization could be directed by the protecting group on the N. Jianbo Wang of Peking University established (J. Org. Chem. 2008, 73, 1971) a convenient route to diazo esters such as 6. N-H insertion led to the pyrrolidine, which Zhen-Jiang Xu of the Shanghai Institute of Organic Chemistry and Chi-Ming Che of the University of Hong Kong showed (Organic Lett. 2008, 10, 1529) could be reduced with high diastereoselectivity to the hydroxy ester 7. Alternatively, Professor Wang found that photochemical Wolff rearrangement of 6 delivered the pyrrolidone 8 . Martin J. Slater and Shiping Xie of GlaxoSmithKline optimized (J. Org. Chem. 2008, 73, 3094) the hydroquinine catalyzed enantioselective 3+2 cycloaddition of 9 and 10, leading to the pyrrolidine 11 with high diastereocontrol. Shu Kobayashi of the University of Tokyo developed (Adv. Synth. Cat. 2008, 350, 647) a practical protocol for the aza Diels-Alder construction of enantiomerically-pure piperidines such as 14 . Biao Yu of the Shanghai Institute of Organic Chemistry cyclized (Tetrahedron Lett. 2008, 49, 672) the product from the proline-catalyzed enantioselective aldol of 15 and 16, leading to the substituted piperidine 17 . Michael Shipman of the University of Warwick described (Tetrahedron Lett. 2008, 49, 250) the cyclization of the aziridine derived from 18, that proceeded to give 19 as a single diastereomer, apparently via kinetic side-chain protonation. Takeo Kawabata of Kyoto University found (J. Am. Chem. Soc. 2008, 130, 4153) that intramolecular alkylation to form four, five and six-membered rings from amino esters such as 21 proceeded with remarkable enantioretention. Géraldine Masson and Jieping Zhu of CNRS, Gif-sur-Yvette, condensed (Organic Lett. 2008, 10, 1509) cinnamaldehyde 23 with cyanide and an ω-alkenyl amine to give the intramolecular aza-Diels-Alder substrate 24. Hongbin Zhai of the Shanghai Institute of Organic Chemistry acylated (J. Org. Chem. 2008, 73, 3589) 26 with 27, leading to the ring-closing metathesis precursor 28.

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.

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.

Metal-Mediated C–C Ring Construction: The Lei Synthesis of (−)-Huperzine Q

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Conjugate Addition ◽  
Harvard University ◽  
Unsaturated Ester ◽  
Pd Catalyst ◽  
Enantiomerically Pure ◽  
Shanghai Institute ◽  
Diastereoselective Addition ◽  
University Of Bristol ◽  
The University

Following the Szymoniak protocol, Morwenna S. M. Pearson-Long and Philippe Bertus of the Université du Maine added (Synthesis 2015, 47, 992) the Grignard rea­gent 2 to the nitrile 1 to give the cyclopropyl amine 3. Chen-Guo Feng of the Shanghai Institute of Organic Chemistry prepared (Chem. Commun. 2015, 51, 8773) the cyclobutane 6 by enantioselective conjugate addition of 5 to the unsaturated ester 4. Martin Kotora of Charles University showed (Eur. J. Org. Chem. 2015, 2868) that the zirconacycle from the eneyne 7 reacted with the aldehyde 8 to give, after iodina­tion, the alcohol 9. Xiaoming Feng of Sichuan University used (Angew. Chem. Int. Ed. 2015, 54, 1608) a scandium catalyst to effect the intramolecular Roskamp cyclization of 10 to 11. Celia Dominguez of CHDI observed (Org. Lett. 2015, 17, 1401) that the double alkylation of the ester 12 with the dibromide 13 proceeded with high diaste­reoselectivity, to give 14. Hirokazu Tsukamoto of Tohoku University cyclized (Chem. Commun. 2015, 51, 8027) 15 to 16 in high ee. Daniel J. Weix of the University of Rochester found (J. Am. Chem. Soc. 2015, 137, 3237) that under the influence of an enantiomerically-pure Ti catalyst, the organon­ickel species derived from 18 opened the prochiral epoxide 17 to give 19 in high ee. John F. Bower of the University of Bristol optimized (J. Am. Chem. Soc. 2015, 137, 463) conditions for the highly diastereoselective Rh-mediated cyclocarbonylation of 20 to 21. Margaret A. Brimble of the University of Auckland initiated (J. Org. Chem. 2015, 80, 2231) the construction of the cyclohexenone 24 by the diastereoselective addition of 23 to the unsaturated ester 22. Olivier Baslé and Marc Maduit of ENSC Rennes devised (Chem. Eur. J. 2015, 21, 993) conditions for the preparation of 26 by enantioselective conjugate addition to the cyclohexenone 25. Yoshito Kishi of Harvard University demonstrated (Tetrahedron Lett. 2015, 56, 3220) that the carbenoid generated from the epoxide 27 cyclized to 28 with high dia­stereoselectivity. Wenjun Tang, also of the Shanghai Institute of Organic Chemistry, developed (Angew. Chem. Int. Ed. 2015, 54, 3033) a Pd catalyst for the diastereoselec­tive (because it is enantioselective) cyclization of 29 to 30.

Substituted Benzenes: The Garg Synthesis of Tubingensin A

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
University Of Pennsylvania ◽  
Ni Catalyst ◽  
Indiana University ◽  
Aryl Iodide ◽  
Shanghai Institute ◽  
Peking University ◽  
Normal University ◽  
La Jolla ◽  
The University

John F. Hartwig of the University of California, Berkeley devised (Science 2014, 343, 853) conditions for the regioselective silylation of an arene 1 to give 2. The silyl group can directly be converted, inter alia, to halo, amino, alkyl, or hydroxyl. Jin-Quan Yu of Scripps La Jolla effected (Angew. Chem. Int. Ed. 2014, 53, 2683) regioselective alkenylation of the arene 3 with 4 to give 5. Wei-Liang Duan of the Shanghai Institute of Organic Chemistry described (Org. Lett. 2014, 16, 500) a related alkenyl­ation protocol. Deping Wang of Henyang Normal University developed (Eur. J. Org. Chem. 2014, 315) inexpensive conditions for the conversion of an aryl bromide 6 to the corre­sponding phenol 7. Mamoru Tobisu and Naoto Chatani of Osaka University used (J. Am. Chem. Soc. 2014, 136, 5587) a Ni catalyst to convert the lactam 8 to the aryl boro­nate 9. Patrick J. Walsh of the University of Pennsylvania found (Adv. Synth. Catal. 2014, 356, 165) conditions for the clean monoarylation of the amide 11 with 10 to give 12. In an application of the Catellani approach, Zhi- Yuan Chen of Jiangxi Normal University coupled (Chem. Eur. J. 2014, 20, 4237) the aryl iodide 13 with 14 to give the amino ester 15. Frederic Fabis of the Université de Caen-Basse-Normandie used (Chem. Eur. J. 2014, 20, 7507) Pd to catalyze the ortho halogenation (and alkoxylation) of the N-sulfonylamide 16 to give 17. Wen Wan of Shanghai University and Jian Hao of Shanghai University and the Shanghai Institute of Organic Chemistry effected (Chem. Commun. 2014, 50, 5733) ortho azidination of the aniline 18 with 19, leading to 20. Jianbo Wang of Peking University found (Angew. Chem. Int. Ed. 2014, 53, 1364) that the N-aryloxy amide 21 could be combined with the α-diazo ester 22 to give the ortho-alkenyl phenol 23. Silas P. Cook of Indiana University uncovered (Org. Lett. 2014, 16, 2026) remarkably simple conditions for the enantiospecific cyclization of 24 (65% ee) to 25 (63% ee). The development of arynes as reactive intermediates continues unabated. Xiaoming Zeng of Xi’an Jiaotong University developed (Org. Lett. 2014, 16, 314) the reagent 27 for the bis-functionalization of the aryne derived from 26.

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.

Synthesis of Naturally Occurring Cyclic Ethers: Boivivianin B (Murakami), SC- Δ 13 -9-IsoF (Taber), Brevisamide (Panek, Lindsley,Ghosh), Gambierol (Mori)

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Absolute Configuration ◽  
Cyclic Ether ◽  
Diels Alder ◽  
Synthetic Methods ◽  
Hydroxy Ketone ◽  
Total Syntheses ◽  
Enantiomerically Pure ◽  
Boston University ◽  
Gambierdiscus Toxicus ◽  
The University

The challenge of controlling the relative and absolute configuration of highly substituted cyclic ether-containing natural products continues to stimulate the development of new synthetic methods. Masahiro Murakami of Kyoto University showed (J. Org. Chem. 2009, 74, 6050) that Rh-mediated addition of an aryl boronic acid to 1 proceeded with high syn diastereocontrol, giving 3. This set the stage for Au-mediated rearrangement, leading to 4. We found (J. Org. Chem. 2009, 74, 5516) that asymmetric epoxidation of 5 followed by exposure to AD-mix could be used to prepare each of the four diastereomers of 6. We carried 6 on the isofuran 7, using a stereodivergent strategy that allowed the preparation of each of the 32 enantiomerically pure diastereomers of the natural product. Following up on the synthesis of brevisamide 16 described (Organic Highlights, November 16, 2009) by Kazuo Tachibana of the University of Tokyo, three groups reported alternative total syntheses. James S. Panek of Boston University prepared (Organic Lett. 2009, 11, 4390) the cyclic ether of 16 by addition of the enantiomerically pure silane 9 to 8. Craig W. Lindsley of Vanderbilt University used (Organic Lett. 2009, 11, 3950) SmI2 to effect the cyclization of 11 to 12. Arun K. Ghosh of Purdue University employed (Organic Lett. 2009, 11, 4164) an enantiomerically pure Cr catalyst to direct the absolute configuration in the hetero Diels-Alder addition of 14 to 13. Rubottom oxidation of the enol ether so formed led to the α-hydroxy ketone 15. Yuji Mori of Meijo University described (Organic Lett. 2009, 11, 4382) the total synthesis of the Gambierdiscus toxicus ladder ether gambierol 19. A key strategy, used repeatedly through the sequence, was the exo cyclization of an epoxy sulfone, illustrated by the conversion of 17 to 18. The epoxy sulfones were prepared by alkylating the anions derived from preformed epoxy sulfones such as 20.

Heteroaromatics: The Zhou/Li Synthesis of Goniomitine

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Oxidative Cyclization ◽  
Silyl Ether ◽  
Keto Ester ◽  
Transfer Protein ◽  
Shanghai Institute ◽  
Lanzhou Institute ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

Xin-Yan Wu of East China University of Science and Technology and Jun Yang of the Shanghai Institute of Organic Chemistry added (Tetrahedron Lett. 2014, 55, 4071) the Grignard reagent 1 to propargyl alcohol 2 to give an intermediate that could be bory­lated, then coupled under Pd catalysis with an anhydride, leading to the furan 3. Fuwei Li of the Lanzhou Institute of Chemical Physics constructed (Org. Lett. 2014, 16, 5992) the furan 6 by oxidizing the keto ester 4 in the presence of the enamide 5. Yuanhong Liu of the Shanghai Institute of Organic Chemistry prepared (Angew. Chem. Int. Ed. 2014, 53, 11596) the pyrrole 9 by reducing the azadiene 7 with the Negishi reagent, then adding the nitrile 8. Yefeng Tang of Tsinghua University found (Tetrahedron Lett. 2014, 55, 6455) that the Rh carbene derived from 11 could be added to an enol silyl ether 10 to give the pyrrole 12. Pazhamalai Anbarasan of the Indian Institute of Technology Madras reported (J. Org. Chem. 2014, 79, 8428) related results. Zheng Huang of the Shanghai Institute of Organic Chemistry established (Angew. Chem. Int. Ed. 2014, 53, 1390) a connection between substituted piperidines and pyridines by dehydrogenating 13 to 15, with 14 as the acceptor. Joseph P. A. Harrity of the University of Sheffield conceived (Chem. Eur. J. 2014, 20, 12889) the cascade assembly of the pyridine 18 by cycloaddition of 16 with 17 followed by Pd-catalyzed coupling. Teck-Peng Loh of Nanyang Technological University converted (Org. Lett. 2014, 16, 3432) the keto ester 19 into the azirine, then eliminated it to form an aza­triene that cyclized to the pyridine 20. En route to a cholesteryl ester transfer protein inhibitor, Zhengxu S. Han of Boehringer Ingelheim combined (Org. Lett. 2014, 16, 4142) 21 with 22 to give an intermediate that could be oxidized to 23. Magnus Rueping of RWTH Aachen used (Angew. Chem. Int. Ed. 2014, 53, 13264) an Ir photoredox catalyst in conjunction with a Pd catalyst to cyclize the enamine 24 to the indole 25. Yingming Yao and Yingsheng Zhao of Soochow University effected (Angew. Chem. Int. Ed. 2014, 53, 9884) oxidative cyclization of 26 to 27.

Diels–Alder Cycloaddition: Sarcandralactone A (Snyder), Pseudopterosin (−)-G-J Aglycone (Paddon-Row/Sherburn), IBIR-22 (Westwood), Muironolide A (Zakarian), Platencin (Banwell), Chatancin (Maimone)

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Absolute Configuration ◽  
Alder Reaction ◽  
Diels Alder ◽  
University Of California ◽  
Enantiomerically Pure ◽  
Protein Protein Interaction ◽  
South Wales ◽  
National University ◽  
The Absolute ◽  
The University

En route to sarcandralactone A 3, Scott A. Snyder of Scripps Florida effected (Angew. Chem. Int. Ed. 2015, 54, 7842) Diels–Alder cycloaddition of the activated enone 1 to the Danishefsky diene. On exposure to trifluoroacetic acid, the adduct was unraveled to the ene dione 2. Michael N. Paddon-Row of the University of New South Wales and Michael S. Sherburn of the Australian National University prepared (Nature Chem. 2015, 7, 82) the allene 4 in enantiomerically-pure form. Sequential cycloaddition with 5 followed by 6 gave an adduct that was decarbonylated to 7. Further cycloaddition with nitro­ethylene 8 led to the pseudopterosin (−)-G-J aglycone 9. The protein–protein interaction inhibitor JBIR-22 12 contains a quaternary α-amino acid pendant to a bicyclic core. Nicholas J. Westwood of the University of St. Andrews set (Angew. Chem. Int. Ed. 2015, 54, 4046) the absolute configuration of the core 11 by using an organocatalyst to activate the cyclization of 10. Metal catalysts can also be used to set the absolute configuration of a Diels–Alder cycloaddition. In the course of establishing the structure of the marine natural prod­uct muironolide A 15, Armen Zakarian of the University of California, Santa Barbara cyclized (J. Am. Chem. Soc. 2015, 137, 5907) the enol form of 13 preferentially to the diastereomer 14. Unactivated intramolecular Diels–Alder cycloadditions have been carried out with more and more challenging substrates. A key step in the synthesis (Chem. Asian. J. 2015, 10, 427) of (−)-platencin 18 by Martin G. Banwell, also of the Australian National University, was the cyclization of 16 to 17. In another illustration of the power of the unactivated intramolecular Diels–Alder reaction, Thomas J. Maimone of the University of California, Berkeley cyclized (Angew. Chem. Int. Ed. 2015, 54, 1223) the tetraene 19 to the tricycle 20. Allylic chlo­rination followed by reductive cyclization converted 20 to chatancin 21.

Construction of Alkylated Stereogenic Centers: The Zhu Synthesis of (−)-Rhazinilam

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
University Of California ◽  
Shanghai Institute ◽  
Stereogenic Centers ◽  
Cu Catalyst ◽  
The University

Zheng Huang of the Shanghai Institute of Organic Chemistry (J. Am. Chem. Soc. 2014, 136, 15501) and Zhan Lu of Zhejiang University (Org. Lett. 2014, 16, 6452) effected enantioselective hydroboration of α-alkyl styrenes, as illustrated by the conversion of 1 to 2. Stephen L. Buchwald of MIT devised (J. Am. Chem. Soc. 2014, 136, 15913) a Cu catalyst for the anti-Markovnikov hydroamination of 3 with 4 to give 5. John F. Hartwig of the University of California, Berkeley developed (Angew. Chem. Int. Ed. 2014, 53, 8691, 12172) an Ir catalyst for the enantioselective coupling of 6 with 7 to give 8.

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