451-28-5Relevant academic research and scientific papers
Synthesis of di- and tri-substituted imidazole-4-carboxylates via PBu3-mediated [3+2] cycloaddition
Hsu, Mei-Yuan,Dietrich, Justin,Hulme, Christopher,Shaw, Arthur Y.
, p. 1538 - 1542 (2013/05/21)
Some new di- and trisubstituted imidazole-4-carboxylates were prepared from amidoacetic acids 3 in the present report. The key step to establish such imidazole- 4-carboxylates stemmed from the PBu3-mediated [3+2] cycloaddition between in situ-generated Δ2-oxazolinone 4 and ethyl cyanoformate6. Our results indicated that trisubstituted imidazoles 7-20 were afforded in better yields than those of disubstituted imidazoles 21-27. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications1 to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
A tandem [3+2] cycloaddition-elimination cascade reaction to generate pyrrolo-[3,4-c]pyrrole-1,3-diones
Martinez-Ariza, Guillermo,Dietrich, Justin,De Moliner, Fabio,Hulme, Christopher
, p. 1801 - 1804 (2013/09/12)
An efficient tandem [3+2] cycloaddition-elimination cascade sequence has been developed enabling assembly of the pharmacologically relevant pyrrolo-[3,4-c]pyrrole-1,3-dione chemotype. The strategy involves simple mixing of readily accessible oxazolin-2-on
Bispalladacycle-catalyzed Michael addition of in situ formed azlactones to enones
Weber, Manuel,Jautze, Sascha,Frey, Wolfgang,Peters, René
supporting information, p. 14792 - 14804 (2013/01/15)
The development and further evolution of the first catalytic asymmetric conjugate additions of azlactones as activated amino acid derivatives to enones is described. Whereas the first-generation approach started from isolated azlactones, in the second-generation approach the azlactones could be generated in situ starting from racemic N-benzoylated amino acids. The third evolution stage could make use of racemic unprotected α-amino acids to directly form highly enantioenriched and diastereomerically pure masked quaternary amino acid products bearing an additional tertiary stereocenter. The step-economic transformations were accomplished by cooperative activation by using a robust planar chiral bis-Pd catalyst, a Br?nsted acid (HOAc or BzOH; Ac=acetyl, Bz=benzoyl), and a Br?nsted base (NaOAc). In particular the second- and third-generation approaches provide a rapid and divergent access to biologically interesting unnatural quaternary amino acid derivatives from inexpensive bulk chemicals. In that way highly enantioenriched acyclic α-amino acids, α-alkyl proline, and α-alkyl pyroglutamic acid derivatives could be prepared in diastereomerically pure form. In addition, a unique way is presented to prepare diastereomerically pure bicyclic dipeptides in just two steps from unprotected tertiary α-amino acids. Flourishing step economy: The evolution of the catalytic asymmetric addition of azlactones to enones is described. The first-generation approach started from isolated azlactones. In the second-generation approach azlactones could be generated in situ from racemic N-benzoylated amino acids. The third evolution stage could directly use racemic unprotected α-amino acids to form a large number of highly enantioenriched quaternary amino acids derivatives (see figure). Copyright
Characterization of amino acids and steroids by fluorine-19 nuclear magnetic resonance spectrometry of p-fluorobenzoyl derivatives
Spratt,Meng,Dorn
, p. 76 - 81 (2007/10/02)
The utility of p-fluorobenzoyl chloride as an analytical **1**9F NMR reagent to characterize sterols and amino acids is reported. The **1**9F chemical shift data for approximately 30 sterols and amino acids are presented. The interaction of the p-fluorobenzoyl group with the steroid ring system makes a significant contribution to the **1**9F chemical shift of these steroid derivatives. These results suggest a convenient technique for characterizing different steroids (e. g. , estrogens, pregnanes, androstanes, etc. ).
