Enantioselective Nickel-Catalyzed Intramolecular Allylic Alkenylations Enabled by Reversible Alkenylnickel E/Z Isomerization.

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.

N-Benzyl-1,3-dide-oxy-1,3-imino-l-xylitol.

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-H⋯O and O-H⋯N hydrogen bonds link the mol-ecules into layers in the ab plane.

2-Azido-3,4;6,7-di-O-isopropyl-idene-α-d-glycero-d-talo-heptopyran-ose.

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 0.642 (10):0.358 (10) ratio. The crystal structure consists of O-H⋯O hydrogen-bonded trimer units. The absolute configuration was determined from the use of d-mannose as the starting material.

Azetidine iminosugars from the cyclization of 3,5-di-O-triflates of α-furanosides and of 2,4-di-O-triflates of ß-pyranosides derived from glucose.

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.

Eight stereoisomers of homonojirimycin from D-mannose.

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.

Inhibition of nonmammalian glycosidases by azetidine iminosugars derived from stable 3,5-di-O-triflates of pentoses.

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.