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1.
Org Lett ; 10(3): 369-72, 2008 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-18181633

RESUMO

Decomposition of a diazo beta-ketoamide derived from N-trityl serine imidazolide and N-protected acetanilides provides, instead of the expected 3-acyloxindole product, an enantiomerically pure (EP) beta-lactam. The amino acid stereocenter is incorporated, the second chiral center is induced, and trityl protection of the beta-lactam ring is realized for the first time. The desired 3-acyloxindole is obtained from oxindole and Tr-Ser(OBn)-imidazole, the X-ray of which provides the first structural determination of an EP amino acid imidazolide.


Assuntos
Imidazóis/química , beta-Lactamas/síntese química , Acetanilidas/química , Aminoácidos/química , Indóis/síntese química , Indóis/química , Estrutura Molecular , Serina/química , Estereoisomerismo
2.
Org Lett ; 9(4): 567-70, 2007 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-17249679

RESUMO

Covalent attachment of quinine to a salen framework through a racemic linker gave a new mixed ligand in a 1:1 diastereomeric mixture, from which an active Lewis acid-Lewis base (LA*-LB*) bifunctional catalyst derived from Co(II) was discovered by the screening of metal complexes. The remarkable intramolecular bifunctional catalytic activity (1 mol % catalyst loading) of the new catalyst was demonstrated using a proof-of-principle reaction. [reaction: see text].

3.
Org Lett ; 4(23): 4121-4, 2002 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-12423101

RESUMO

Derivatives of methyl 5-hydroxy-2-oxo-1-cyclohexanecarboxylate react with aryllead(IV) reagents in high yield and with wide variation in diastereoselectivity. Ab initio calculations are consistent with a heretofore unrecognized attraction between the carbanionic center of the beta-ketoester intermediate and the distal OSiR(3) group. This attractive interaction stabilizes the silyl group in the axial conformation and leads to the excellent trans diastereoselection in the formation of quaternary centers. [reaction: see text]

4.
Org Lett ; 10(18): 3969-72, 2008 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-18702502

RESUMO

The synthesis of both the AEFG macrolactam and the CDEFG bis-indole/tyrosine units found in the marine natural product diazonamide A is presented. Key to the success of the synthesis is the highly stereoselective direct C-arylation of an oxindole by an aryllead(IV) reagent derived from tyrosine.


Assuntos
Compostos Heterocíclicos de 4 ou mais Anéis/química , Oxazóis/química , Benzofuranos/química , Compostos Heterocíclicos de 4 ou mais Anéis/síntese química , Indóis/química , Oxazóis/síntese química , Oxindóis , Estereoisomerismo , Especificidade por Substrato , Tirosina/química
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