Construction of Arrays of Stereogenic Centers: The Zhang Synthesis of (+)-Podophyllotoxin

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Conjugate Addition ◽  
Chiral Auxiliary ◽  
Stanford University ◽  
Enol Ethers ◽  
University Of Technology ◽  
Stereogenic Centers ◽  
Diastereoselective Addition ◽  
University Of Bristol ◽  
The University

Varinder K. Aggarwal of the University of Bristol showed (Angew. Chem. Int. Ed. 2009, 48, 1149) that condensation of a boronic ester 2 with a metalated aziridine 1 led, after oxidation, to the defined amino alcohol 3. Hisashi Yamamoto of the University of Chicago developed (Angew. Chem. Int. Ed. 2009, 48, 3333) conditions for the diastereoselective addition of an organometallic to an α-nitrosylated aldehyde, to give, after reduction, the diol 6. Xiaoyu Wu of Shanghai University and Gang Zhao of the Shanghai Institute of Organic Chemistry designed (Adv. Synth. Cat. 2009, 351, 158) an organocatalyst that mediated the enantioselective addition of hydroxyacetone 7 to a range of aldehydes. Andrew G. Myers of Harvard University found (J. Am. Chem. Soc. 2009, 131, 5763) that trialkylaluminum reagents opened epoxides of enol ethers at the more substituted position, delivering protected diols such as 10. Keiji Maruoka of Kyoto University created (Angew. Chem. Int. Ed. 2009, 48, 1838) an organocatalyst for the addition of an aldehyde 11 to an imine 12, to give 13. Markus Kalesse of Leibnitz Universität Hannover showed (Tetrahedron Lett. 2009, 50, 3485) that an organocatalyst could mediate the selective γ-reactivity of 15, leading to 16. Barry M. Trost of Stanford University found (J. Am. Chem. Soc. 2009, 131, 1674) that an organocatalyst directed the addition of diazoacetate 18 to an aldehyde, to give, after further reaction with a trialkylborane, the syn aldol product 19. Professor Trost also demonstrated (J. Am. Chem. Soc. 2009, 131, 4572) that a related complex mediated the conjugate addition of 22 to 21. Enantioselective construction of arrays of alkylated stereogenic centers is a particular challenge. Ji Zhang, then at Pfizer, found (Tetrahedron Lett. 2009, 50, 1167) that the chiral auxiliary of 24 directed both the conjugate addition and the subsequent protonation, and also allowed the product 25 to be brought to > 98% purity by crystallization. Tönis Kanger of Tallinn University of Technology developed (J. Org. Chem. 2009, 74, 3772) an organocatalyst for the conjugate addition of aldehydes to nitrostyrenes such as 26 to give 27.

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.

Stereocontrolled C-N Ring Construction: The Pyne Synthesis of Hyacinthacine B 3

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Conjugate Addition ◽  
Enantioselective Hydrogenation ◽  
Pd Catalyst ◽  
University Of Michigan ◽  
Palo Alto ◽  
University Of Toronto ◽  
University Of Oxford ◽  
University Of Bristol ◽  
The University

Keiji Maruoka of Kyoto University found (Organic Lett. 2010, 12, 1668) that the diazo amide 1 derived from the Oppolzer sultam condensed with the imine 2 to give the aziridine 3 with high stereocontrol. Andrei K. Yudin of the University of Toronto observed (Angew. Chem. Int. Ed. 2010, 49, 1607) that the unprotected aziridine aldehyde 4, which exists as a mixture of dimers, condensed smoothly with the Ohira reagent 5 to give the alkynyl aziridine 6. David M. Hodgson of the University of Oxford successfully (Angew. Chem. Int. Ed. 2010, 49, 2900) deprotonated the azetidine thioamide 7 to give, after allylation, the azetidine 8. Varinder K. Aggarwal of the University of Bristol devised (Chem. Commun. 2010, 267) a Pd catalyst for the cyclocarbonylation of an alkenyl aziridine 9 to give the β-lactam 10. Iain Coldham of the University of Sheffield used (J. Org. Chem. 2010, 75, 4069) the ligand they had developed to effect enantioselective allylation of the pyrrolidine derivative 11. The corrresponding piperidine worked as well. John P. Wolfe of the University of Michigan established (Organic Lett. 2010, 12, 2322) that the Pd-mediated cyclization of 13 to 15 could be effected with high diastereocontrol. Christopher G. Frost of the University of Bath optimized (Angew. Chem. Int. Ed. 2010, 49, 1825) the tandem Ru-mediated conjugate addition/cyclization of 16 to give 18 in high ee. Barry M. Trost of Stanford University extended (J. Am. Chem. Soc. 2010, 132, 8238) their studies of trimethylenemethane cycloaddition to the ketimine 19, leading to the substituted pyrrolidine 21 in high ee. Pher G. Andersson of Uppsala University optimized (J. Am. Chem. Soc. 2010, 132, 8880) an Ir catalyst for the enantioselective hydrogenation of readily prepared tetrahydropyridines such as 22. Min Shi of the Shanghai Institute of Organic Chemistry devised (J. Org. Chem. 2010, 75, 3935) a Pd catalyst for enantioselective conjugate addition to the prochiral pyridone 24. Xiaojun Huang of Roche Palo Alto prepared (Tetrahedron Lett. 2010, 51, 1554) the monoacid 26 by enantioselective methanolysis of the anhydride. Selective formylation of the ester led to the pyridone 27.

Metal-Mediated Carbocyclic Construction: The Simpkins Synthesis of Ialibinones A and B

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Gold Catalyst ◽  
Conjugate Addition ◽  
South Florida ◽  
Pt Catalyst ◽  
General Strategy ◽  
Ru Catalyst ◽  
University Of Technology ◽  
Rh Catalyst ◽  
Institute Of Technology ◽  
The University

Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen devised (J. Am. Chem. Soc. 2010, 132, 14349) what promises to be a general strategy for the construction of enantiomerically pure cyclopropanes, based on conjugate addition to acceptors such as 1 . X. Peter Zhang of the University of South Florida developed (J. Am. Chem. Soc. 2010, 132, 12796) a Co catalyst for the enantioselective cyclopropanation of α-olefins such as 3. Seiji Iwasa of Toyohashi University of Technology designed (Angew. Chem. Int. Ed. 2010, 49, 8439) a resin-bound Ru catalyst that could be used repeatedly for the enantioselective cyclization of the ester 6. Rai-Shung Lin of National Tsing-Hua University showed (Angew. Chem. Int. Ed. 2010, 49, 9891) that a gold catalyst could expand the alkyne 8 to the cyclobutene 9. Takao Ikariya of the Tokyo Institute of Technology reported (J. Am. Chem. Soc. 2010, 132, 16637) a detailed study of the enantioselective conjugate addition of malonate 11 to cyclopentenone 10. Vladimir A. D’yakonov of the Russian Academy of Sciences, Ufa, showed (Tetrahedron Lett. 2010, 51, 5886) that a cyclic alkyne 13 could be annulated to the cyclopentenone 14. Shunichi Hashimoto of Hokkaido University also designed (Angew. Chem. Int. Ed. 2010, 49, 6979) a resin-bound Rh catalyst that could also be used repeatedly for the enantioselective cyclization of the ester 15. Tushar Kanti Chakraborty of the Central Drug Research Institute used (Tetrahedron Lett. 2010, 51, 4425) Ti(III) to mediate the diastereoselective cyclization of 17 to 18. Alexandre Alexakis of the University of Geneva extended (Synlett 2010, 1694) enantioselective conjugate addition of isopropenyl to the more difficult enone 19. Joseph P. A. Harrity of the University of Sheffield showed (Org. Lett. 2010, 12, 4832) that Pd could catalyze the rearrangement of 21 to 22. Strategies for the controlled construction of polycyclic ring systems are also important. Günter Helmchen of the Universität Heidelberg showed (J. Org. Chem. 2010, 75, 7917) that 23 was efficiently cyclized to the diene with Pt catalyst. The reaction could be carried out in the presence of the dienophile 24 to give 25 directly.

Enantioselective Construction of Alkylated Centers: The Maier Synthesis of Platencin

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Unsaturated Ketone ◽  
West Virginia University ◽  
Aryl Iodide ◽  
Quaternary Centers ◽  
University Of New Mexico ◽  
Conjugate Reduction ◽  
Complementary Approach ◽  
Stereogenic Centers ◽  
The University

Jaesook Yun of Sungkyunkwan University devised (J. Org. Chem. 2009, 74, 4232) a method, based on conjugate addition to a cyano alkyne, for the preparation of nitriles such as 1 with high geometric control. Enantioselective conjugate reduction then delivered the doubly arylated stereogenic center of 2 in high ee. Pher G. Andersson of Uppsala University described (J. Am. Chem. Soc. 2009, 131, 8855) a similar approach to diarylated ternary stereogenic centers. Motomu Kanai and Masakatsu Shibasaki of the University of Tokyo developed (J. Am. Chem. Soc. 2009, 131, 3858) a complementary approach to dialkylated stereogenic centers based on enantioselective conjugate cyanation of α-methylene N-acylpyrroles such as 3. Cathleen M. Crudden of Queen’s University established (J. Am. Chem. Soc. 2009, 131, 5024) that a benzylic organoborane, prepared by enantioselective hydroboration of styrene, coupled with an aryl iodide such as 6 in good yield and with > 90% retention of ee. Kwunmin Chen of National Taiwan Normal University devised ( Adv. Synth. Cat. 2009, 351, 1273) an organocatalyst for the enantioselective Michael addition of an α,α,-dialkyl aldehyde such as 9 to a nitroalkene. Wenhu Duan of the East China University of Science and Technology and Wei Wang of the University of New Mexico together developed (Organic Lett. 2009, 11, 2864) an organocatalyst for the enantioselective addition of nitromethane 12 to an unsaturated ketone such as 11. Xiaodong Shi of West Virginia University found (Angew. Chem. Int. Ed. 2009, 48, 1279) that commercial diphenyl prolinol effectively promoted enantioselective conjugate addition of 15 to 14. Enantioselective methods for the construction of alkylated quaternary centers have also been put forward. Kin-ichi Tadano of Keio University devised (Tetrahedron Lett. 2009, 50, 1139) a glucose-derived chiral auxiliary that effectively directed the absolute sense of the alkylation of 17. Li Deng of Brandeis University reported (Tetrahedron 2009, 65, 3139) further details of his elegant Cinchona -mediated conjugate addition of 19 to 20. Francesca Marini of the Università degli Studi di Perugia extended (Adv. Synth. Cat. 2009, 351, 103) this approach to selenones, effecting, over two steps, enantioselective vinylation.

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.

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.

Construction of Oxygenated and Aminated Stereogenic Centers

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Indiana University ◽  
University Of Alberta ◽  
University Of Toronto ◽  
Stereogenic Centers ◽  
University Of Calgary ◽  
Cu Catalyst ◽  
Korea Research Institute ◽  
Hydrolysis Of Esters ◽  
The University

Computational analysis of the Novozyme 435 active site led (Tetrahedron Lett. 2010, 51, 309) Liyan Dai and Hongwei Yu of Zhejiang University, Hangzhou, to t-butanol for the enantioselective monoesterification of 1 to 2. Bruce H. Lipshutz of the University of California, Santa Barbara, devised (J. Am. Chem. Soc. 2010, 132, 7852) a Cu catalyst that mediated the enantioselective 1,2-reduction of α-branched enones such as 3. Qi-Lin Zhou of Nankai University found (J. Am. Chem. Soc. 2010, 132, 1172) that an α-alkoxy unsaturated acid 5 could be hydrogenated with high ee. Tohru Yamada of Keio University desymmetrized (J. Am. Chem. Soc. 2010, 132, 4072) the tertiary alcohol 7, delivering the enol lactone 8. Zachary D. Aron of Indiana University established (Organic Lett. 2010, 12, 1916) that the simple aldehyde 10 effected rapid racemization of the α-amino ester 9. Running the epimerization in the presence of an enantioselective esterase produced 11 high ee. Robert A. Batey of the University of Toronto devised (Organic Lett. 2010, 12, 260) a Pd catalyst for the enantioselective rearrangement of 12 to 13. In the course of a synthesis of dapoxetine, Hyeon-Kyu Lee of the Korea Research Institute of Chemical Technology showed (J. Org. Chem. 2010, 75, 237) that the Rh*-mediated intramolecular C-H insertion of 14 to 15, as developed by Du Bois, gave the opposite absolute configuration to that originally assigned. To prepare α-quaternary amines, Thomas G. Back of the University of Calgary explored (J. Org. Chem. 2010, 75, 1612) the selectivity of the PLE hydrolysis of esters such as 16. Daniel R. Fandrick and colleagues at Boehringer Ingelheim reported (J. Am. Chem. Soc. 2010, 132, 7600) a general method for the catalytic enantioselective propargylation of aldehydes, including 18. Dennis G. Hall of the University of Alberta devised (J. Am. Chem. Soc. 2010, 132, 5544) a route to α-hydroxy esters such as 22 by enantioselective conjugate addition to 21. Alexandre Alexakis of the University of Geneva prepared (Chem. Commun. 2010, 46, 4085) disubstituted epoxides such as 25 by the conjugate addition of 23 to 24.

Carbon-Carbon Bond Formation

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Alkyl Halide ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Phenyl Isocyanate ◽  
Ni Catalyst ◽  
Reductive Coupling ◽  
Carbon Carbon Bond ◽  
University Of Technology ◽  
Osaka Prefecture ◽  
The University

Akiya Ogawa of Osaka Prefecture University found (Tetrahedron Lett. 2010, 51, 6580) that the Sm-mediated reductive coupling of a halide 1 with CO2 to give the carboxylic acid 2 was strongly promoted by visible light. Gregory C. Fu of MIT designed (Angew. Chem. Int. Ed. 2010, 49, 6676) a Ni catalyst for the coupling of a primary borane 4 with a secondary alkyl halide 3. James P. Morken of Boston College devised (Org. Lett. 2010, 12, 3760) conditions for the carbonylative conjugate addition of a dialkyl zinc to an enone 6 to give the 1,4-dicarbonyl product 7. Louis Fensterbank of the Institut Parisien de Chimie Moléculaire developed (Angew. Chem. Int. Ed. 2010, 49, 8721; not illustrated) a protocol for the conjugate addition of alkyl boranes to enones. Hyunik Shin of LG Life Science, Daejeon, and Sang-gi Lee of Ewha Womans University showed (Tetrahedron Lett. 2010, 51, 6893) that the intermediate from Blaise homologation of a nitrile 8 was a powerful nucleophile, smoothly opening an epoxide 10 to deliver 11. Sébastien Reymond and Janine Cossy of ESPCI ParisTech found (J. Org. Chem. 2010, 75, 5151) that FeCl3 smoothly catalyzed the coupling of an alkenyl Grignard 13 with the primary iodide 12. The Ti-mediated coupling of an alkyne 16 with an allylic alkoxide 15 (J. Am. Chem. Soc. 2010, 132, 9576) developed by Glenn C. Micalizio of Scripps/Florida was the key step in the total synthesis (J. Am. Chem. Soc. 2010, 132, 11422) of lehualide B. Huanfeng Jiang of the South China University of Technology observed (Chem. Commun. 2010, 46, 8049) that KI added to a bromoalkyne 18 to give the dihalide 19 with high geometric control. Haruhiko Fuwa of Tohoku University improved (Org. Lett. 2010, 12, 5354) the selective hydroiodination of a methyl alkyne 20 to 21. Takuya Kurahashi and Seijiro Matsubara of Kyoto University devised (Chem. Commun. 2010, 46, 8055) the Ni-catalyzed three-component coupling of an alkyne 22, methyl acrylate 23, and phenyl isocyanate to give the doubly homologated lactam 24. Patrick H. Toy of the University of Hong Kong showed (Synlett 2010, 1997; Org. Lett. 2010, 12, 4996 for a polymer with covalently attached base) that resin-bound triphenylphosphine participated efficiently in the Wittig coupling of 26 with an aldehyde 25.

Arrays of Stereogenic Centers: The Carbery Synthesis of Mycestericin G

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Dipolar Cycloaddition ◽  
General Strategy ◽  
Stanford University ◽  
Keto Ester ◽  
Stereogenic Centers ◽  
Crystalline Adduct ◽  
Enantioselective Addition ◽  
The University ◽  
Pais Vasco

Chi-Ming Che of the University of Hong Kong devised (Chem. Commun. 2011, 47, 11204) a manganese catalyst for the enantioselective cis-dihydroxylation of electron-deficient alkenes such as 1. Christine Greck of Université de Versailles-St-Quentin effected (Tetrahedron Lett. 2012, 53, 1085) enantioselective alkoxylation of 3, remarkably without β-elimination. Keiji Maruoka of Kyoto University developed (J. Am. Chem. Soc. 2012, 134, 7516) an organocatalyst for the enantioselective anti addition of 5 to 6 to give 7. Barry M. Trost of Stanford University developed (J. Am. Chem. Soc. 2012, 134, 2075) a Mg catalyst for the enantioselective addition of ethyl diazoacetate to an aldehyde 8, and carried the adduct onto 9. Professor Maruoka designed (Angew. Chem. Int. Ed. 2012, 51, 1187) for the enantioselective addition of a ketone 10 to the alkynyl ketone 11 to give 12. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry found (Org. Lett. 2012, 14, 3108) that 14 could be added under very soft conditions to 13 to give the anti adduct 15. René Peters of the Universität Stuttgart added (Adv. Synth. Catal. 2012, 354, 1443) the azlactone formed in situ to 17 in a conjugate sense to give 18. Kaïss Aouadi and Jean-Pierre Praly of the Université de Lyon prepared (Tetrahedron Lett. 2012, 53, 2817) the nitrone 19 from the inexpensive (–)-menthone. Dipolar cycloaddition to a range of alkenes proceeded with substantial diastereocontrol, as illustrated for 20, which gave the crystalline adduct 21. Jeffrey S. Johnson of the University of North Carolina reduced (J. Am. Chem. Soc. 2012, 134, 7329) the α-keto ester 22 under equilibrating conditions to give the lactone 23. Claudio Palomo of the Universidad del País Vasco alkylated (J. Org. Chem. 2012, 77, 747) the aldehyde 24 with 25 to give the diester 26. Damien Bonne and Jean Rodriguez of Aix-Marseille Université added (Adv. Synth. Catal. 2012, 354, 563) the α-keto ester 27 to 28 in a conjugate sense to give 29. Glenn C. Micalizio of Scripps/Florida developed (Angew. Chem. Int. Ed. 2012, 51, 5152) a general strategy for the stereocontrolled construction of skipped-conjugate dienes such as 30.

C-O Ring Natural Products: (-)-Serotobenine (Fukuyama-Kan), (-)-Aureonitol (Cox), Salmochelin SX (Gagné), Botcinin F (Shiina), (-)-Saliniketal B (Paterson), Haterumalide NA (Borhan)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Indole Alkaloid ◽  
Chiral Auxiliary ◽  
Michigan State University ◽  
State University ◽  
Ene Reaction ◽  
Enantiomerically Pure ◽  
Cambridge University ◽  
Stereogenic Centers ◽  
Ready Access ◽  
The University

Tohru Fukuyama of the University of Tokyo and Toshiyuki Kan of the University of Shizuoka devised ( J. Am. Chem. Soc. 2008, 130, 16854) the chiral auxiliary-directed Rh-mediated cyclization of 1, setting the two stereogenic centers of 2 with high stereocontrol. The ester 2 was carried on to the indole alkaloid (-)-Serotobenine 3. In the course of a synthesis of (-)-Aureonitol 6, Liam R. Cox of the University of Birmingham developed (J. Org. Chem. 2008, 73, 7616) the diastereoselective intramolecular addition of an allyl silane 4 to give the tetrahydrofuran 5. In analogy to what is known about the intramolecular ene reaction, the diastereocontrol observed for this cyclization may depend on the allyl silane being Z. Michel R. Gagné of the University of North Carolina found (J. Am. Chem. Soc. 2008, 130, 12177) that the Ni-catalyzed coupling of organozinc halides could be extended to glycosyl halides such as 7. This opened ready access to C -alkyl and C -aryl glycosides, including Salmochelin SX 10. Isamu Shiina of the Tokyo University of Science established (Organic Lett. 2008, 10, 3153) that the acid-mediated cyclization of the Sharpless-derived epoxide 10 proceeded with clean inversion, to give 11. The highly-substituted tetrahydropyran core 11 was then elaborated to the antifungal Botcinin F 12. Ian Paterson of Cambridge University optimized (Organic Lett. 2008, 10, 3295) the Pd-catalyzed spirocyclization of the ene diol 13, leading to 14, the enantiomerically-pure bicyclic core of (-)-Saliniketal B 15. Haterumalide NA 18 presented the particular challenge of assembling the geometrically-defined chloroalkene, in addition to closing the macrolide ring. Babak Borhan of Michigan State University addressed (J. Am. Chem. Soc. 2008, 130, 12228) both of these challenges together, electing to employ a chlorovinylidene chromium carbenoid, as developed by Falck and Mioskowski, to effect the macrocyclization of 16 to 17.

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