PROBLEM TO BE SOLVED: To obtain a new compound strongly inhibiting human α-amylase and therefore useful for prophylactic and/or therapy of such diseases as hyperglycemia, e.g. diabetes and diseases caused thereby. SOLUTION: This new compound is a compound of formula I (n is 0-3; X is H or a hydrophobic group), for example, (3R, 4R, 5R, 6S)-hexahydro-3,5,6- trihydroxy-1H-azepin-4-yl O-(6-deoxy-α-D-glucopyranosyl)-(1→4)-α-D- glucopyranoside. The compound of formula I is obtained, for example, by reacting a compound of formula II with p-toluenesulfonyl chloride in pyridine, and, as necessary, separating 61-tosyl, 63-modified maltooligosaccharide in a usual way, thereafter, obtaining 61-azide, 63-modified maltooligosaccharide by reacting the above-mentioned oligosaccharide with sodium azide in N,N- dimethylformamide, separating it in a usual way, and then reducing it in the presence of Pd-C by adding hydrogen gas thereto.