Dehydration of a 2-13C-labeled synthetic sample of the natural aglucone 2, 4-dihydroxy-7- methoxy-2 H-1, 4-benzoxazin-3 (4 H)-one ([2-13C]-DIMBOA, 10) using N- ethoxycarbonyltrichloroacetaldimine led to 3-formyl-6-methoxybenzoxazolin-2 (3 H)-one (13C-labeled FMBOA, 11) with complete transfer of the 13C label into the-CHO group. On the basis of this finding, a mechanism for the dehydration is proposed.
![[2-(13)C]-methoxymethoxyacetic acid methyl ester Structure](https://image.chemsrc.com/caspic/269/415724-87-7.png)
