PURPOSE: To obtain nojirimycin-δ-lactam and deoxynojirimycin by using an epoxide derivative of L-idofranoise as a branch intermediate.

CONSTITUTION: A pyridine ring is formed by connecting N between C-1 and C-5, in accompany with the reversal of configuration of 5,6anhydro3-0-benzil-1,20- isopropyridene-Lindofranose of formula I as an branch intermediate, by C-5, to obtain nojirimycinδ-lactam of formula II, or a piperidine ring is formed by connecting N between C-2 and C-6 in accompany with the reversal of configuration of the inatermediate by C-2, to obtain deoxynojirimycin of formula III. Dibenzillactam of formula VII (R is Bn) is obtained from, for example, the compound of formula I through triflate of formula IV (R is SO2CF3; Bn is benzil), glucoazide of formula V, and azidelactone of formula VI, and then the benzil group is removed, to obtain the compound of formula II.