A trisaccharide (G1calpha1-4Glcalpha1-6Glc) and a tetrasaccharide (Glcalpha1-4Glcalphal-4Glcoalpha1-6Glc) the structures of which are related to that of repeating unit of pullulan have been obtained, exploiting the transglycolytic activity of Aspergillus niger cyclodextrin glucanotransferase. Both products were obtained in one-pot reaction using as a donor the alpha-cyclodextrin and as an acceptor the disaccharide isomaltose. The regioselectivity of the reaction was 85% for the tetrasaccharide and 80% for the trisaccharide. The yield of reaction resulted to be 42% for the synthesis of trisaccharide and 25% for that of tetrasaccharide. Purification of products was performed by size exclusion chromatography and by semipreparative reverse phase HPLC after reversible derivatization with 2-aminopyridine. Structural characterization was performed by capillary electrophoresis, ion-spray mass spectrometry, and by C-13-NMR spectroscopy. A comparison of these results with those obtained by using alpha-D-glucosidase, which had been effective for the synthesis of the disaccharide isomaltose, is reported. (C) 2002 Elsevier Science (USA). All rights reserved.