PURPOSE: To provide new compounds excellent in assays for α-anglase activities and useful in diagnosis of pancreatopathy.

CONSTITUTION: A compound of formula I (wherein R is a silyl; R1 is a hydrogen; R2 is oligoglucoside residue containing at least two glucose units; X is a hydrogen or a label group which exhibits an optically measurable change), for example 6-O-thexyldimethylsilyl-4-nitrophenyl-α-D-maltoheptaoside, is provided by reacting a compound of formula II (wherein R and R1 are each a protecting group) with an acid anhydride to obtain an acyl derivative, reacting the obtained acyl derivative with an acid or a base which eliminate a protecting group of R and R1 and then contacting the reaction mixture to a silylating agent to eliminate the acyl group.