RESUMO
Enantioselective nickel-catalyzed arylative cyclizations of substrates containing a Z-allylic phosphate tethered to an alkyne are described. These reactions give multisubstituted chiral aza- and carbocycles, and are initiated by the addition of an arylboronic acid to the alkyne, followed by cyclization of the resulting alkenylnickel species onto the allylic phosphate. The reversible E/Z isomerization of the alkenylnickel species is essential for the success of the reactions.
RESUMO
Primary amines with either 3,5-di-O-ditriflates of α-furanosides or 2,4-di-O-triflates of ß-pyranosides form bicyclic azetidines in high yield.
Assuntos
Aminas/química , Azetidinas/síntese química , Glucose/química , Imino Açúcares/síntese química , Mesilatos/química , Azetidinas/química , Ciclização , Imino Açúcares/química , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
Although there are 32 6-azidoheptitols, there are only 16 homonojirimycin (HNJ) stereoisomers. Two epimeric azidoalditols derived from d-mannose allow the synthesis in water of eight stereoisomers of HNJ.
Assuntos
1-Desoxinojirimicina/análogos & derivados , Manose/química , 1-Desoxinojirimicina/síntese química , 1-Desoxinojirimicina/química , Euphorbiaceae/química , Estrutura Molecular , EstereoisomerismoRESUMO
The structure determination confirms the stereochemistry of the title compound, C(12)H(17)NO(3), which contains a four-membered azetidine ring system. The absolute configuration was determined by the use of d-glucose as the starting material. In the crystal, O-Hâ¯O and O-Hâ¯N hydrogen bonds link the mol-ecules into layers in the ab plane.
RESUMO
Efficient ring closure of stable crystalline 3,5-di-O-triflates of pentofuranosides with amines to form azetidines allowed preliminary evaluation of four-ring iminosugars as glycosidase inhibitors; significant and specific inhibition of nonmammalian α-glucosidases is shown by L-xylo- and L-arabino-iminosugar azetidines.
Assuntos
Azetidinas/química , Inibidores Enzimáticos/síntese química , Glicosídeo Hidrolases/antagonistas & inibidores , Imino Açúcares/síntese química , Animais , Inibidores Enzimáticos/farmacologia , Imino Açúcares/farmacologia , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
In the title compound, C(13)H(21)N(3)O(6), the six-membered ring adopts a twist-boat conformation with the azide group in the bowsprit position. The azide group is disordered over two sets of sites in a 0.642â (10):0.358â (10) ratio. The crystal structure consists of O-Hâ¯O hydrogen-bonded trimer units. The absolute configuration was determined from the use of d-mannose as the starting material.