Abstract A reaction of raffinose with an excess amount of 2,2-dimethoxypropane and p-toluenesulfonic acid as a catalyst in N,N′-dimethylformamide, followed by acetylation, gave seven kinds of mono-, di, or tri-O-isopropylideneraffinose peracetates with at least five kinds of minor products. A reaction of raffinose with a limited amount of 2,2-dimethoxypropane gave a new isopropylidene derivative with some of the derivatives described above. The isopropylidenation occurred at 1′,2-, 2,3-, 2″,3″-, 3,4-, 3″,4″-, and 4″,6″-positions. The structures of these compounds were established by 1H and 13C NMR analyses.