DIBAL-H mediated triple and quadruple debenzylations of perbenzylated cyclodextrins.

Diisobutylaluminium hydride (DIBAL-H) mediated reductive removal of benzyl groups was investigated for perbenzylated alpha-, beta- and gamma-cyclodextrins using DIBAL-H in hexane as the reagent. It was found that under the new conditions, the debenzylation can be better controlled to provide sequentially tri- and tetra-debenzylated products in moderate yields and in a regioselective manner. In the case of alpha-cyclodextrin, the removal of the third and fourth benzyl groups took a different path involving the secondary rim, compared to beta- and gamma-cyclodextrins which both gave only 6-O-debenzylated products.

Regio- and stereocontrolled selective debenzylation and substitution reactions of C-2 formyl glycals. Application in the synthesis of constrained beta-sugar amino acids.

O-Benzyl-protected C-2 formyl glycals are regioselectively deprotected and acetylated first at C-3 and then at C-6 upon treatment with a ZnCl2-Ac2O-AcOH reagent combination. Treatment of the thus-obtained C-3 acetate with various nucleophiles leads to substitution at C-3 with retention of stereochemistry in the galactal series, whereas mixed results were obtained with glucal-derived compounds. Two of the azido-substituted products were converted into the corresponding beta-sugar amino acids.

New method for chloroamidation of olefins. Application in the synthesis of N-glycopeptides and anticancer agents.

Chloroamidation of olefins using a new reagent system (COCl)2-AgNO3-CH3CN was observed. Various glycals with this reagent system produce 2-chloro-1-acetamido sugars in good yields which, in turn, were converted to free amino derivatives and various glycopeptides. The acetamido sugar derivatives and free amines were found to be promising anticancer agents against the U-87 malignant glyoma (a brain tumor) cell line with IC-50=1 nm-22 microM, and they were found to be far less cytotoxic against a normal human embryonic kidney cell line.

Controlled synthesis of linear alpha-cyclodextrin oligomers using copper-catalyzed Huisgen 1,3-dipolar cycloaddition.

The design and efficient synthesis of a novel class of linear oligomers based on cyclodextrins are described. These supramolecules have relatively rigid structures with well-defined topology and sizes, which could provide them with the ability to be used as scaffolds to present bioactive molecules to their receptors as well as host molecules.