Disaccharides of formula (I) are derived from a-maltosyl fluoride, wherein
R.sup.1 and R.sup.2 are defined. Such disaccharides are useful as
glycosyl donors in transglycosylation reactions catalyzed by
glycoside-hydrolazes or in transfer reactions catalyzed by
transglycosylases during the preparation of oligosaccharides or
polysaccharides.