Enantioselective Diels-Alder reaction of (E)-1-trimethylsilyloxy-1,3-butadiene with chiral glyoxylates

1990 ◽  
Vol 55 (1) ◽  
pp. 230-244 ◽  
Author(s):  
Otakar Červinka ◽  
Aleš Svatoš ◽  
Petr Trška ◽  
Pavel Pech
Keyword(s):  
Nmr Spectroscopy ◽  
Quantum Chemical Calculations ◽  
Absolute Configuration ◽  
Quantum Chemical ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Chemical Correlation ◽  
The Absolute ◽  
C Nmr

Enantioselective Diels-Alder reaction of (E)-1-trimethylsilyloxy-1,3-butadiene (I) with chiral (-)-menthyl (II) and (-)-8-phenylmenthyl (III) glyoxylates in various solvents without or with catalysts was studied. The reactions gave a mixture of trans-and cis-isomers of (-)-menthyl (IV) and (-)-8-phenylmenthyl (V) 2-trimethylsilyloxy-5,6-dihydro-2H-pyran-6-carboxylates. The regioselectivity of the reaction was explained by quantum-chemical calculations, the enantioselectivity was determined using 13C NMR spectroscopy and the absolute configuration of the addition products was assigned on the basis of chemical correlation with (S)-(-)-dimethyl malate.

The synergy of different solid-state techniques to elucidate the supramolecular assembly of two 1H-benzotriazole polymorphs

2019 ◽  
Vol 21 (36) ◽  
pp. 19879-19889
Author(s):  
María Mar Quesada-Moreno ◽  
Juan Ramón Avilés-Moreno ◽  
Juan Jesús López-González ◽  
Fco. Javier Zúñiga ◽  
Dolores Santa María ◽  
...  
Keyword(s):  
Solid State ◽  
Quantum Chemical Calculations ◽  
Absolute Configuration ◽  
Quantum Chemical ◽  
Supramolecular Structure ◽  
Supramolecular Assembly ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Absolute

4aα (chiral) and 4aβ (achiral) polymorphs of 1H-benzotriazole are studied by X-ray crystallography, SSNMR, IR, Raman, VCD, and quantum chemical calculations. The absolute configuration of the supramolecular structure of 4aα polymorph is determined.

Synthese und Absolute Konfiguration von (+)-1-Amino-2-propanthiol·HCl / Synthesis and Absolute Configuration of ( + )-1-Amino-2-propanethiol · HCl

1987 ◽  
Vol 42 (5) ◽  
pp. 617-622 ◽  
Author(s):  
Sigurd Elz ◽  
Martin Dräger ◽  
Hans-Joachim Sattler ◽  
Walter Schunack
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
X Ray ◽  
Single Diastereomer ◽  
Important Intermediate ◽  
The Absolute ◽  
C Nmr

)-4a-The structure of (-)-5-methyl-2-phenylthiazolidine (( -)-4a), an intermediate in the synthesis of (+)-1-amino-2-propanethiol · HCl ((+)-2 · HCl), was elucidated by 1H and 13C NMR spectroscopy. In contrast to earlier findings it was shown that the important intermediate ( -)-4a is not a single diastereomer but represents a 1:1 mixture of (2R,5Sand ((2S,5S)-4a-diastereomers. The absolute configuration of the (2S,3S)-di-O-(4-toluoyl)tartrate of the disulfide (5) derived from (+)-2 · HCl was determined to be (S,S) using X-ray technique.

Quantum-chemical investigation of the Diels-Alder reaction in condensed isoindoles with a nodal nitrogen atom

1988 ◽  
Vol 24 (2) ◽  
pp. 179-185
Author(s):  
V. A. Kovtunenko ◽  
Z. V. Voitenko ◽  
L. I. Savranskii ◽  
A. K. Tyltin ◽  
F. S. Babichev
Keyword(s):  
Nitrogen Atom ◽  
Quantum Chemical ◽  
Alder Reaction ◽  
Diels Alder ◽  
Chemical Investigation ◽  
Quantum Chemical Investigation ◽  
Diels Alder Reaction

Diastereoselectivity and asymmetric induction in the Diels–Alder reaction of o-quinodimethanes

1986 ◽  
Vol 64 (4) ◽  
pp. 720-725 ◽  
Author(s):  
James L. Charlton
Keyword(s):  
Maleic Anhydride ◽  
Methyl Acrylate ◽  
Dimethyl Fumarate ◽  
Alder Reaction ◽  
Diels Alder ◽  
Asymmetric Induction ◽  
Diels Alder Reaction ◽  
The Absolute ◽  
Alkoxy Groups

The extent of asymmetric induction in the bimolecular Diels–Alder reactions of chiral o-quinodimethanes with dimethyl fumarate, methyl acrylate, and maleic anhydride has been studied. o-Quinodimethanes with chiral α-alkoxy groups were prepared from 1-alkoxy-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4a–f or 1-alkoxy-3-phenyl-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4g–h by thermolysis. These alkoxybenzosulfones were prepared from the corresponding hydroxybenzosulfones 8 and 1-phenylethanol, 2-phenyl-1-propanol, 4-phenyl-2-butanol, 1-phenyl-2-propanol, 3,3-dimethyl-2-butanol, or 1-cyclo-hexylethanol. The 1-phenylethoxy substituent yielded the largest asymmetric induction. The absolute configurations of the major cycloadducts of methyl acrylate with the o-quinodimethanes generated from 1-(R- 1-phenylethoxy)- and 1-(S-1-phenylethoxy)-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4i and 4j have been determined to be 1S,2S-1-(R-1-phenylethoxy)- and 1R,2R-1-(S-1-phenylethoxy)-2-carbomethoxy-1,2,3,4-tetrahydronaphthalene 11i and 11j, respectively. The proposition that a chiral alkoxy substituent can block one face of the o-quinodimethane towards addition of a dienophile is discussed.

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.

Immobilisierung von Cytidin und Uridin über 2'.3'-O-cyclische Acetalderivate an Agarose / Im mobilisation of Cytidine and Uridine via 2',3'-O-Cyclic Acetal Derivatives to Agarose

1978 ◽  
Vol 33 (1-2) ◽  
pp. 56-60 ◽  
Author(s):  
Frank Seela ◽  
Helmut Roseineyer
Keyword(s):  
Nmr Spectroscopy ◽  
Absolute Configuration ◽  
Alkaline Hydrolysis ◽  
Carboxyl Groups ◽  
Cyclic Acetal ◽  
Ethyl Group ◽  
Ethyl Levulinate ◽  
The Absolute ◽  
Hydrolysis Of ◽  
C Nmr

Abstract Condensation of cytidine or uridine with ethyl levulinate leads to the acetals 1a/2a. The reac­tion would be expected to give mixtures of diastereoisom ers. As shown by 1H and 13C NMR spectroscopy only one diastereoisomer is formed. By spectroscopic comparison of 1a/2a with the corresponding adenosine acetal the absolute configuration of the new chiral centre was found to be R. The acetal m ethyl group of 1a/2a in exo-location can serve to distinguish the two m ethyl signals of O-2′,3′-isopropylidenecytidine and -uridine in the NM R spectra. On alkaline hydrolysis of the esters the acids 1b and 2b are formed, which can be condensed through their carboxyl groups with 6-aminohexylagarose. The affinity resins 3 and 4 contain 7.1 μmol and 7.6 μmol ligand/g moist gel respectively. A biospecificity of the new polymers to cytidine-and uridine converting enzymes is expected.

scholarly journals Z and E rotamers of N -formyl-1-bromo-4-hydroxy-3-methoxymorphinan-6-one and their interconversion as studied by 1 H/13 C NMR spectroscopy and quantum chemical calculations

2012 ◽  
Vol 51 (2) ◽  
pp. 82-88 ◽  
Author(s):  
Agnieszka Sulima ◽  
Kejun Cheng ◽  
Arthur E. Jacobson ◽  
Kenner C. Rice ◽  
Klaus Gawrisch ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
C Nmr
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