The natural aglucone 2,4-dihydroxy-7-methoxy-2H-1, 4-benzoxazin-3(4H)-one (DIMBOA, 1) of maize underwent spontaneous dehydration and rearrangement to form 3-formyl-6-methoxybenzoxazolin-2(3H)-one (FMBOA, 2) on reaction with N-ethoxycarbonyl-trichloroacetaldimine. Compound 2 was proven to be a reactive formyl donor toward N-, O-, and S-nucleophiles, which may be important in case 2 is formed under biological conditions.