A Formylating Agent by Dehydration of the Natural Product DIMBOA

Abstract

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.

Elucidation of the Final Reactions of DIMBOA-Glucoside Biosynthesis in Maize: Characterization ofBx6andBx7

“…It is a distinctively more reactive compound than DIBOA. As a donor, the 7-MeO group facilitates N-O bond heterolysis (Hashimoto and Shudo, 1996) and the dehydration of DIMBOA (Hofmann and Sicker, 1999). The first process leads to the formation of a reactive, multicentered cationic electrophile; the latter results in the generation of a reactive formyl donor toward -NH2, -OH, and -SH groups.…”

A Mechanistic Dehydration Study with [2-13C]-DIMBOA

“…The crude pale brown crystals were recrystallized from CHCl 3 to yield [formyl- 13 C]-3-formyl-6-methoxybenzoxazolin-2(3H)-one (11, 66 mg, 39% isolated yield) as offwhite crystals, mp 140-142 °C; its 1 H and 13 C NMR spectra were in accordance with those of an authentic sample. 11 In the 13 C NMR spectrum the CHO peak at δ 158.4 was increased due to the complete transfer of the 13 C label to this position.…”

“…The spectroscopic data of 10 are in complete accordance with those from natural DIMBOA. All of the 13 Finally, the [2-13 C]-labeled DIMBOA gave rise to 13 C-FMBOA (11) when subjected to N-ethoxycarbonyltrichloroacetaldimine. 17 The yield for this conversion was believed higher than the isolated yield, as judged from the 1 H NMR spectrum of the crude product mixture, but the feature of FMBOA being an active formyl donor toward nucleophiles made the workup procedure laborious.…”

“…The preparative route is outlined in Scheme 1. The synthetic sequence for the isotopomers of 13 C-labeled FMBOA (11) was optimized using unlabeled compounds beforehand. The label was introduced using [2- 13 C]-glycolic acid (2).…”