Three analogues of phenyl α-maltoside which is a long known synthetic substrate of Taka-amylase A [EC 3.2.1. 1] were synthesized. Two of the new compounds, phenyl 2-O-methyl-α-maltoside and phenyl 2-deoxy-α-maltoside were found to be not susceptible to the enzyme. They showed considerable inhibitory action against the enzyme when phenyl α-maltoside was used as a substrate. One of the new compounds, phenyl 4-O-α-glucosyl-α-mannoside, was also found to be immune to the enzyme. Rather amazingly, the last compound showed no inhibitory action against the enzyme.