Cyclodextrin glycosyltransferase enzyme from Bacillus circulans catalyzed the effective conversion of 4-thio-α-maltosyl fluoride into cyclo-α-(1 → 4 2 )-thiomalto -tetraoside , -pentaoside, -hexaoside and linear hemithiomaltooligosaccharides. However, under the same conditions, C-maltosyl fluoride afforded only linear modified maltotetraose, maltohexaose and maltooctaose in moderate yield.