Complex Cyclic Ethers: (+)-Conocarpan (Hashimoto), (-)-Brevisamide (Satake/ Tachibana), (+)-Bruguierol A (Fañanás/ Rodríguez), (-)-Berkelic Acid (Snider), and (-)-Aigialomycin D (Harvey)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Absolute Configuration ◽  
Cyclic Ether ◽  
Membered Ring ◽  
Open Pit ◽  
Relative Configuration ◽  
Enantiomerically Pure ◽  
Berkelic Acid ◽  
The Absolute ◽  
Berkeley Pit ◽  
The University

( + )-Conocarpan 3, isolated from the wood of Conocarpus erectus , exhibits insecticidal, antifungal and antitrypanosomal activity. Shunichi Hashimoto of Hokkaido University developed (J. Org. Chem. 2009, 74 , 4418) a chiral Rh (II) carboxylate that effected the cyclization of 1 to 2, setting the absolute configuration of 3. The dinoflagellate Karenia brevis produces the brevetoxins, a family of complex polyethers. Recently, the first N-containing cyclic ether, (-)-Brevisamide 6, was isolated from K. brevis . Masayuki Satake and Kazuo Tachibana of the University of Tokyo, in their synthesis of 6 (Organic Lett. 2009, 11, 217) found it convenient to set the relative configuration around the six-membered ring by double hydroboration/oxidation of the diene 4. ( + )-Bruguierol A 9, isolated from the mangrove Bruguiera gymmorrhiza, has an unusual bridged structure. Francisco J. Fañanás and Félix Rodríguez of the Universidad de Oviedo conceived (J. Org. Chem. 2009, 74, 932) an elegant approach to the construction of 9, based on the Pt-mediated addition of the alcohol of 7 to the alkyne to give a transient enol ether. It is not clear whether the subsequent intramolecular electrophilic addition to the aromatic ring is mediated by the Pt, or by a trace of adventitious acid. The overall transformation was remarkably efficient. The Berkeley Pit in Butte, Montana, is an abandoned open-pit copper mine filled with 30 billion gallons of pH = 2.5 water heavily contaminated with, inter alia , copper, cadmium, arsenic and zinc. Remarkably, microorganisms can be cultured from that water. (-)-Berkelic Acid 13 , isolated from a Penicillium fungus, showed selective activity against OVCAR-3 ovarian cancer. Barry B. Snider of Brandeis University set (Angew. Chem. Int. Ed. 2009, 48, 1283) the absolute configuration of the central five-membered ring ether of 13 by conjugate addition of the enantiomerically-pure reagent 11 to the prochiral lactone 10. (-)-Aigialomycin D 17, isolated from the mangrove fungus Aigialus parvus , was found to be a selective inhibitor of the kinases CDK1, CDK5 and GSK3.

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.

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.

CD-Spectroscopic Investigations for the Determination of the Absolute Configuration of α-Alkylated 1,4-CycIohexanedione Derivatives

2000 ◽  
Vol 55 (11) ◽  
pp. 1011-1014 ◽  
Author(s):  
Jörg Fleischhauer ◽  
Sven Gabriel ◽  
Dieter Ender ◽  
Anja Nühring ◽  
Axel Wollmer
Keyword(s):  
Absolute Configuration ◽  
Membered Ring ◽  
Cd Spectra ◽  
Pure Material ◽  
Enantiomerically Pure ◽  
System 2 ◽  
The Absolute ◽  
Stereogenic Center ◽  
Rotational Strengths

The absolute configuration of the conformationally flexible six membered ring system 2-methyl- and 2,6-dimethyl-l,4-cyclohexanedione monoethylene acetal was determined by comparison of measured and calculated CD spectra. The rotational strengths were calculated by means of the CNDO/S-method assuming R at the stereogenic center. The results were compared with the predictions made by the octant rule. The enantiomerically pure material was synthesized via the corresponding SAMP- and RAMP-hydrazones.

Stereocontrolled Construction of C-N Rings: The Vanderwal Synthesis of Norfluorocurarine

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Absolute Configuration ◽  
Enantiomeric Excess ◽  
Silver Catalyst ◽  
West Virginia University ◽  
Science And Engineering ◽  
Enantiomerically Pure ◽  
The Absolute ◽  
Asymmetric Transformation ◽  
The University ◽  
Stereogenic Center

Forrest E. Michael of the University of Washington described (Organic Lett. 2009, 11, 1147) the Pd-catalyzed aminative cyclization of 1 to the differentially-protected diamine 3. Peter Somfai of KTH Chemical Science and Engineering observed (Organic Lett. 2009, 11, 919) that [1,2]-rearrangement of 4 proceeded to deliver 5 with near-perfect maintenance of enantiomeric excess. Tushar Kanti Chakraborty of the Central Drug Research Institute, Lucknow applied (Tetrahedron Lett. 2009, 50, 3306) the Ti(III) reduction of epoxides to the Sharpless-derived ether 6, leading to the pyrrolidine 7. Chun-Jiang Wang of Wuhan University devised (Chem. Commun. 2009, 2905) a silver catalyst that directed the absolute sense of the dipolar addition of 9 to 8 to give 10. Homoallyic azides such as 11 are readily prepared in high enantiomeric excess from the corresponding alcohol. Bernhard Breit of Albert-Ludwigs-Universität, Freiburg and André Mann of the Faculté de Pharmacie, Illkirch showed (Organic Lett. 2009, 11, 261) that Rh-mediated hydroformylation could be effected in the presence of the azide. Subsequent reduction delivered the piperidine 12. Jan-E. Bäckvall of Stockholm University applied (J. Org. Chem. 2009, 74, 1988) the protocol for dynamic kinetic asymmetric transformation (DYKAT) that he had developed to the cyanodiol 13. Remarkably, a single enantiomerically- pure diasteromer emerged, which he carried on to 14. Xiaodong Shi of West Virginia University found (Organic Lett. 2009, 11, 2333) that the stereogenic center of 17, even though it ended up outside the ring, directed the absolute configuration of the other centers of 18 as they formed. Jan Vesely of Charles University and Albert Moyano and Ramon Rios of the Universitat de Barcelona established (Tetrahedron Lett. 2009, 50, 1943) that an organocatayst directed the absolute configuration in the addition of 19 to 20 to give 21. Osamu Tamura of Showa Pharmaceutical University effected (Organic Lett. 2009, 11, 1179) cyclization of the malic acid-derived amide 22 to give 23 with high diastereocontrol.

Enzymes in organic synthesis. 33. Stereoselective pig liver esterase-catalyzed hydrolyses of meso cyclopentyl-, tetrahydrofuranyl-, and tetrahydrothiophenyl-1,3-diesters

1985 ◽  
Vol 63 (2) ◽  
pp. 452-456 ◽  
Author(s):  
J. Bryan Jones ◽  
R. Scott Hinks ◽  
Philip G. Hultin
Keyword(s):  
Organic Synthesis ◽  
Absolute Configuration ◽  
Enantiomeric Excess ◽  
Membered Ring ◽  
Pig Liver ◽  
Pig Liver Esterase ◽  
Preparative Scale ◽  
Liver Esterase ◽  
The Absolute ◽  
Enzymes In Organic Synthesis

Preparative-scale pig liver esterase-catalyzed hydrolyses of five-membered ring meso-1,3-diesters are enantiotopically selective. While pro-S enantiotopic selectivity is exhibited in each case, the absolute configuration sense of the hydrolysis in the cyclopentyl series is opposite to that of both the tetrahydrofuranyl and tetrahydrothiophenyl diesters. The enantiomeric excess levels induced are in the 34–46% range.

Alkaloid Synthesis: (-)-Aurantioclavine (Stoltz), (-)-Esermethole (Nakao/Hiyama/ Ogoshi), (-)-Kainic Acid (Tomooka), Dasycarpidone (Bennasar), (-)-Cephalotaxine (Ishibashi) and Lysergic Acid (Fujii/Ohno)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Kainic Acid ◽  
Absolute Configuration ◽  
Lysergic Acid ◽  
Ni Catalyst ◽  
Cascade Cyclization ◽  
Alkaloid Synthesis ◽  
Radical Cascade ◽  
The Absolute ◽  
The University ◽  
Stereogenic Center

Intriguing strategies have been developed for the stereocontrolled assembly of complex alkaloid structures. Brian M. Stoltz of Caltech prepared (J. Am. Chem. Soc. 2008, 130, 13745) the enantiomerically-pure alcohol precursor to the secondary amine 1 by enantioselective oxidation of the racemic alcohol. Intramolecular Mitsunobu coupling of 1 then led to (-)-Aurantioclavine 3. Yoshiaki Nakao and Tamejiro Hiyama of Kyoto University and Sensuke Ogoshi of Osaka University developed (J. Am. Chem. Soc. 2008, 130, 12874) an enantioselective Ni catalyst for the cyclization of 4 to 5. Oxidation and cyclization then delivered (-)-Esermethole 6. Although the sulfonamide 7 appears to be prochiral, in fact its two most stable conformations are bent, and enantiomers of each other, with a significant barrier for interconversion. Katsuhiko Tomooka of Kyushu University separated (Tetrahedron Lett. 2008, 49, 6327) the enantiomers of 7, then carried the enantiomercially-pure 7 on, by Pd-catalyzed Cope rearrangement, to 8 and so to (-)-Kainic Acid 9. M.-Lluïsa Bennasar of the University of Barcelona prepared (J. Org. Chem. 2008, 73, 9033) the acyl selenide 11 from the indole 10. While the radical derived from 11 might have been expected to undergo 5-exo cyclization, in the event the 6-endo mode dominated, to give Dasycarpidone 12 and its diastereomer. Hiroyuki Ishibashi of Kanazawa University showed (Organic Lett. 2008, 10, 4129) that the radical cascade cyclization of the enamine 13, derived from diethyl tartrate, proceeded with remarkable diastereocontrol, to give 14. The amide 14 was converted to (-)-Cephalotaxine 15. Nobutaka Fujii and Hiroaki Ohno, also of Kyoto University, used (Organic Lett. 2008, 10, 5239) a Pd catalyst to mediate the cascade cyclization of 16 to 17. Although 16 has two stereogenic centers, including the allene, it is the aminated stereogenic center of 17 that sets the absolute configuration of the product Lysergic Acid 18. One intermediate in the conversion of 16 to the tetracyclic 17 is the tricyclic π-allyl Pd complex. If all the material could be channeled through that pathway, there is a good chance that the chiral Trost catalyst could effectively control the absolute configuration of the aminated stereogenic center as it is formed, leading to the enantiomerically enriched product 18.

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

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

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

scholarly journals Colletinin A and 2,2″-Diepicolletinin A: Two New Bisflavan-3-ols from Rhododendron Collettianum

2008 ◽  
Vol 3 (5) ◽  
pp. 1934578X0800300
Author(s):  
Viqar Uddin Ahmad ◽  
Farman Ullah ◽  
Hidayat Hussain ◽  
Gilles Dujardin ◽  
Arnaud Martel ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
2D Nmr ◽  
Nmr Analysis ◽  
Relative Configuration ◽  
The Absolute

Two new bisflavan-3-ols, named colletinin A (1) and 2,2″-diepicolletinin A (2) have been isolated from Rhododendron collettianum. Their structures were determined by means of 1D and 2D NMR analysis, aided by HREIMS data. The relative configuration was determined by means of 1H-1H NOESY correlation but the absolute configuration could not be established.

Relative configuration, absolute configuration and absolute structure of three isomeric 8-benzyl-2-[(4-bromophenyl)(hydroxy)methyl]-8-azabicyclo[3.2.1]octan-3-ones

2013 ◽  
Vol 69 (3) ◽  
pp. 303-306 ◽  
Author(s):  
Krzysztof Brzezinski ◽  
Ryszard Lazny ◽  
Aneta Nodzewska ◽  
Katarzyna Sidorowicz
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Crystal Structures ◽  
Absolute Configuration ◽  
Compound I ◽  
Relative Configuration ◽  
Enantiomerically Pure ◽  
Space Groups ◽  
Intramolecular Hydrogen ◽  
Absolute Structure

The title compounds, C21H22BrNO2, are isomeric 8-benzyl-2-[(4-bromophenyl)(hydroxy)methyl]-8-azabicyclo[3.2.1]octan-3-ones. Compound (I), the (±)-exo,syn-(1RS,2SR,5SR,9SR) isomer, crystallizes in the hexagonal space groupR\overline{3}, while compounds (II) [the (+)-exo,anti-(1R,2S,5S,9R) isomer] and (III) [the (±)-exo,anti-(1RS,2SR,5SR,9RS) isomer] crystallize in the orthorhombic space groupsP212121andPna21, respectively. The absolute configuration was determined for enantiomerically pure (II). For the noncentrosymmetric crystal of (III), its absolute structure was established. In the crystal structures of (I) and (II), an intramolecular hydrogen bond is formed between the hydroxy group and the heterocyclic N atom. In the crystal structure of racemic (III), hydrogen-bonded chains of molecules are formedviaintermolecular O—H...O interactions. Additionally, face-to-edge π–π interactions are present in the crystal structures of (I) and (II). In all three structures, the piperidinone rings adopt chair conformations and theN-benzyl substituents occupy the equatorial positions.

scholarly journals Absolute configuration of (1S,3R,8R)-10-bromomethyl-2,2-dichloro-3,7,7-trimethyltricyclo[6.4.0.01,3]dodec-9-ene

2013 ◽  
Vol 69 (11) ◽  
pp. o1692-o1693 ◽  
Author(s):  
Abdoullah Bimoussa ◽  
Aziz Auhmani ◽  
My Youssef Ait Itto ◽  
Jean-Claude Daran ◽  
Abdelwahed Auhmani
Keyword(s):  
Absolute Configuration ◽  
Title Compound ◽  
Van Der Waals ◽  
Chair Conformation ◽  
Molecular Packing ◽  
Membered Ring ◽  
Van Der Waals Interactions ◽  
Compound C ◽  
The Absolute

The absolute configuration of the title compound, C16H23BrCl2, has been deduced from the chemical pathway and fully confirmed by refinement of the Flack and Hooft parameters. The six-membered ring adopts a half-chair conformation, whereas the seven-membered ring is a twisted chair. The molecular packing within the crystal is stabilized only by van der Waals interactions.

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