Margarita Vega

Stereoselective synthesis of oxiranes using oxazolidines derived from 2-amino-2-deoxy-d-allose as chiral auxiliaries

Abstract The synthesis of 2,3-epoxyamide derivatives of 2-amino-2-deoxy- d -allose is described. Epoxidation of the corresponding α,β-unsaturated amides with m -CPBA took place with better stereoselectivity when an oxazolidine ring was fused to the 2,3-positions of the sugar molecule. In most cases, both stereoisomers could be isolated and characterized. The stereochemistry of the new stereogenic centers was then determined by cleavage of the oxirane moiety from the chiral auxiliary, which was also recovered.

Stereoselective synthesis of oxazolidines from 2-amino-2-deoxy-d-allose derivatives and their reactivity with nucleophiles

Abstract The use of 2-amino-2-deoxy- d -allose in the synthesis of oxazolidines is described. The reaction takes place with total stereoselectivity in the preparation of both simple oxazolidines (from aldehydes as reagent) and bicyclic oxazolidines (from chlorocarbonyl compounds and keto-acids as reagents). The reactivity of the obtained oxazolidines with hydride and alkylmagnesium chlorides is also described.

Electron impact and chemical ionization mass spectra of N -alkyl and N,N -dialkylaminosugar derivatives

The electron impact mass spectra of 46 new alkyl 4,6-O-benzylidene-2-amino-N-alkyl and N,N-dialkyl-2-deoxy-D-hexopyranosides were examined. Three general pathways of fragmentation were encountered, the importance of which depends above all on the nature of aglycon and also on the nature of nitrogen substituents.

Mass Spectra of N-Alkyl and N,N- Dialkylaminosugar Derivatives. Chemical Evidence for the Different Pathways of Fragmentation

The electron impact ionization mass spectra of new alkyl (and phenyl) 4,6-benzylidene-2-amino-N-alkyl- and N,N-dialkyl-2-deoxy-D-hexopyranosides and benzyl (and phenyl) 4,6-O-benzylidene-2,3-di-O-alkyl-D- hexopyranosides were examined. Three general pathways of fragmentation were encountered. The competition the two most important pathways of fragmentation ([M - R 1 O→]# and H routes) depends primarily on the nature of the aglycone and secondarily on the nature of nitrogen substituents. In addition, relationships between the different peak intensities in each pathways of fragmentation depend exclusively on the nature of nitrogen substituents. Definitive chemical evidence for different pathways of fragmentation was found.