Glucoside carbamate

The synthesis of BOA-6-O-glucoside is catalyzed by constitutive enzymes that may be upregulated. A glucosyltransferase that accepted BOA-6-OH as a substrate was measurable in protein extracts of corn roots harvested from control plants. Detoxification via glucoside carbamate synthesis is inducible and seems to be more complicated than simple A/-glucosylation (data unpublished). The biosynthesis of the compounds is part of our ongoing research. 

Supposed biosynthesis of gentiobioside carbamate by glucosylation of glucoside carbamate. 

BOA-metabolites are not stable constituents of incubated plants but are exuded, at least partially, as found with corn roots.69 Corn seedlings transferred to soil filled pots after BOA incubation lost the extractable metabolites within 5-6 days. In other experiments, the seedlings were transferred to tap water basins after incubation. The water was removed every day and evaporated to dryness. The residue contained relatively high amounts of glucoside carbamate and low concentrations of gentiobioside carbamate. Since the experimental conditions were... 

We tested a number of dicot species for their ability to detoxify BOA. Most of them were incubated as seedlings but some as adult plants when germination failed under laboratory conditions. Applied BOA concentration was 100 and 500 pM, incubation time was 24 h. The plants were separated into roots and shoots after incubation and the material extracted with 30% methanol. HPLC analyses of the extracts revealed remarkable differences in the detoxification capacities. Major detoxification appeared within the roots, whereas shoots were only involved when roots seemed to be overtaxed. All species tested were able to perform BOA-6-O-glucoside synthesis, but with regard to glucoside carbamate synthesis, differences became obvious (Table 4.2). 

BOA detoxification capacity of several weeds with regard to glucoside carbamate synthesis within 24 h. 

It is clear that BOA detoxification, mainly via glucoside carbamate production of the species tested, is not a feature of certain plant families but is rather combined with their occurrence in defined plant communities where benzoxazinone containing character species exist with high density covers. Plantago major is regarded as an exception. 

High Digitaria sanguinalis BOA-6-O-glucoside glucoside carbamate (major product) Poaceae Amarantho- Chenopodion... 

Sicker, D., Schneider, B., Hennig, L., Knop, M., and Schulz, M. 2001. Glucoside carbamate from benzoxazolin-2(3H)-one detoxification in extracts and exudates of corn roots. Phytochemistry 58, 819-825... 

In our early work, we attempted the alkylation of the amine 81 with various carbohydrate triflates, namely 82-84 [57]. Somewhat disappointingly, the main products isolated were the alkenes, e.g. 85 and 86. Only a small amount of the desired N-linked carbasugar, e. g. 87 was ever obtained. At one stage we attempted an alkylation of the amine 81 with the triflate 82 and with the triflate 84 in the presence of potassium carbonate to our surprise, carbamates were formed, 88 and 89 These two carbamates have subsequently been deprotected to give the methyl -o-glucoside 90 and the free sugar 91, interesting candidates for enzyme inhibition studies [57]. 

Figure 3. 4-Nitrophenyl carbamate content during the reaction of dextran with 4-nitrophenyl chloroformate in DMSO/pyridine (vol. ratio 1/1) at 0°C. [anhydro glucosides]0 = 0.1 M [chloroformate = (X) 90 mM, (A) 50 mM, ( ) 12 mM, (O) 8 mM.

Figure 4. Total carbamate content ( ) and 4-nitrophenyl carbamate content (O) during the activation of dextran with 4-nitrophenyl chloroformate [anhydro glucosides]0 =0.1 M [chlorofor-mate]Q = 50 mM.

Species BOA-6-O-glucoside Glucose carbamate Gentiobioside carbamate... 

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