Completion of the spectroscopical data for the synthesis of

Cyclic hydroxamic acids like 2,4-dihydroxy-7-methoxy-2H-I ,4-benzoxazin-3(4 H)-one (DIM BOA) and 2,4-dihydroxy-2H-I ,4-benzoxazin-3(4H)-one (DIBOA) are found in several plants playing an important role in the defense-system of plants against a variety of enemies. To investigate new mechanism and effects we synthesized the molecules using known synthetic pathways. Since the chemical data of DIMBOA are not complete or even false, we decided to publish the missing ones in this journal. toluene1 ethyl 1.8 g


Introduction
Benzoxazinoids are naturally occuring in a variety of plants like Secale cereale L. [I], Triticum aestivum L. or Zea mays L. [2] and especially in many important crop plants of the family Gramineae. These compounds are chemical resistance factors against insects, fungi, bacteria and virus in these plants [3], but inhibitory effects on human cancer cells are also reported [4].

Results and discussion
The chemical and physical data of DlBOA are reported complete [5] and are identical to our results. On the other hand the synthesis of DIMBOA is not described fully in the current publications.
The first step is the synthesis of 5-methoxy-2-nitrophenol (1) which is also available from commercial suppliers but it is quite expensive and only available in small amounts. Hartenstein and Sicker [7] describe a convenient method starting from 3-methoxyphenol which was nitrosylated and then oxidized to yield the corresponding nitro-product.
The potassium salt of 1 reacted with methyl 2-bromo-2-methoxyacetate via &-reaction to yield the corresponding acetale 2. This molecule is quite unstable and only characterized by its melting point in the patent published by Jernow and Rosen [8]. In our work we present the missing data for compound 2. O$OMe

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The following reduction was easily managed according to literature [6] with NaBH4 and 10% palladium on charcoal in waterl dioxane. The nmr data were completed with I3c nmr values given for the cyclic hydroxamic acid 3.
The demethylation of the acetale 3 was carried out with BC13 in CH2C12 followed by the reaction with Ag2C03 in waterl THF as proposed in literature [6]. Although the yield was poor the desired molecule 4 (DIMBOA) could be obtained and the chemical data could be completed or corrected, respectively, since the mass spectrum of the compound was published wrong. In conclusion, we could obtain the desired molecules DlBOA and DIMBOA following the literature and we could complete the physical and chemical data for the synthesis of DIMBOA.

Experimental
The melting points were determined on a Kofler hot-stage apparatus and are uncorrected. The 'H and I3c nmr spectra were recorded on a Bruker Avance DPx200. The ppm-values are related to tetramethylsilane as internal standard. The mass spectra were recorded on a Shimadzu QP-5000 mass spectrometer.
The solution is stirred at room temperature for 2.5 hours. After this 8 ml of THF is added and the mixture is given into a seperatory funnel. Then 15 rnl water is added, the organic layer is removed, the aqueous layer extracted again with ethyl acetate and the combined organic layers are evaporated without drying to a dark oil. This oil is resolved in 15 ml THF and the solution is added over 10 minutes to a rapidly stirring suspension of 6 mmol (1.6 g) silver carbonate in a 2:l water-THF mixture and stirred for 20 minutes. The suspension is then filtered and extracted with ethyl acetate until the aqueous layer shows no color with FeCI3. The combined organic layers are washed with brine, dried over sodium sulfate and concentrated to 10 ml. Then 10 ml hexane is added and the mixture is cooled overnight in a refridgerator. The precipitate is filtered off to yield 0.190 g (30%) of 4 (mp 150-155 "C  8, 156.0, 141.6, 122.4, 113.7,