Syntheses for 2-amino and 2-mercapto-2H-1,4-benzoxazin-3(4H)-one and 2H-1,4-benzothiazin-3(4H)-one as aza and thio analogues of the natural product blepharigenin

2-Amino-2H-1,4-benzoxazin-3(4H)-one 3 , 2-amino-2H-1,4-benzothiazin-3(4H)-one 4 , 2-mercapto-2H-1,4-benzoxazin-3(4H)-one 7 , and 2-mercapto-2H-1,4-benzothiazin-3(4H)-one 8 representing aza and thio analogues of the natural product's aglucone Blepharigenin (2-hydroxy-2H-1,4-benzoxazin-3(4H)-one) from Gramineae and Acantnaceae species have been synthesized for the first time from their 2-bromo precursors 1 and 2 . Attempts to similarly prepare the 4-hydroxy derivatives of 7 and 8 , which would represent new thio analogues of the naturally occurring cyclic hydroxamic acid, 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one, have failed.     

In vitro evaluation of the antioxidant and antimicrobial activity of DIMBOA [2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one]

The aim of this study was to evaluate the in vitro antioxidant and antimicrobial properties of the natural cyclic hydroxamic acid: 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA). Antioxidant activity of the isolated DIMBOA was examined using DPPH, FRAP and ABTS tests. It was found that DIMBOA exhibits a potent free-radical scavenging activity and a weaker iron (III) ions reducing activity. Antimicrobial activity against selected G(+), G(–) bacterial strains and against yeasts-like reference strains of fungi was investigated using disk-diffusion method. It has been shown that DIMBOA possess growth inhibitory properties against many strains of studied bacteria and fungi, such as Staphylococcus aureus, Escherichia coli as well as against Saccharomyces cerevisiae.     

Separation of enantiomers and diastereomers of 4-hydroxy-2H-1,4-benzoxazin-3(4H)-one derivatives by capillary electrophoresis

Summary A high performance capillary electrophoresis (HPCE) procedure for the enantioseparation of the methyl acetals3 and4 of the natural products DIBOA1 and DIMBOA2, respectively, has been developed using borate buffers (pH 9–10 range), cyclodextrins as chiral additives and addition of up to 20% methanol. A mixture of GDIBOA5 and GDIMBOA6 of natural origin was also clearly separated. HPCE proved to be superior to HPLC by the first separation of GDIBOA5 and three of its diastereomers resulting from a synthetic approach to this acetalglucoside.     

Synthesis of 2H-1,4-thiazin-3(4H)-one 1-oxide and 2H-1,4-thiazin-3-(4H)-one 1,1-dioxide,structural analogs of uracil

The synthesis of 1,4-thiazine 1-oxide and 1,1-dioxide analogs of the antibiotic emimycin is described. Reaction of methylthioglycolate with 1-bromo-2,2-diethoxyethane gave methyl (2,2-diethoxyethylthio)acetate ( 2 ). Treatment of 2 with methanolic ammonia followed by cyclization furnished 2H-1,4-thiazin-3(4H)-one ( 5 ). Oxidation of 5 with m-chloroperoxybenzoic acid converted it to 2H-1,4-thiazin-3(4H)-one 1-oxide ( 6 ). Oxidation of 2 with potassium permanganate, followed by treatment with methanolic ammonia, and cyclization gave 2H-1,4-thiazin-3(4H)-one 1,1-dioxide.     

The mass spectra of intramolecularly hydrogen bonded 2(1H)-quinoxalinone and 2H-1,4-benzoxazin-2-one

The mass spectra of those 3-phenacyl derivatives of 2(1H)-quinoxalinone and 2H-1,4-benzoxazin-2-one with an intramolecular hydrogen bonding showd that: (1) the primary elimination of the shole sidchain is reduced as compared with an unchelated derivative; (2) the importan t fragmentation routes in the quinoxalinone series are ring cleavage with loss of CO followed by recyclization and expulsion of a hydrogen atom, and this can also occur in the reverse order; (3) this reverse process is virtually absent in the benzoxazinone series. Finally, the doubly charged molecular ions appear to undergo an analogous decomposition giving fairly intense [M-CO]²⁺ or [M-(CO+H or CI]²⁺ ions.     

Syntheses for 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one derivatives as thio analogues of natural hemiacetals

Reductive cyclizations of methyl 2-(2-nitrophenylthio)acetate 2 by means of electrochemistry or by catalytic hydrogenation have been used as key steps in the syntheses of the hemiacetals 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one 10 and its 4-hydroxy derivative 9 representing thio analogues of allelo chemicals found in Gramineae and Acanthaceae. In contrast to its natural counterpart 2,4-dihydroxy-2H-1,4-benzoxa-zin-3(4H)-one hydroxamic acid 9 did not undergo degradation by extrusion of formic acid.     

Synthesis and structure of 2-(nitromethylene)-2H-1,4-benzothiazin-3(4H)-one

A new representative of benzothiazines, (2Z)-2-(nitromethylene)-2H-1,4-benzothiazin-3(4H)-one, was synthesized, and its structure was studied. According to ¹H NMR, IR, and UV spectral and X-ray diffraction data, the molecules are planar highly conjugated structures that exist in crystal as centrosymmetric dimers; the latter form layers overlapping with each other and held together by strong π-π interaction between the carbonyl groups of neighboring layers.     

Reactions of 4-acetoxy-2H-1,4-benzoxazin-3-ones with some nucleophiles

O-Acetates of 4-hydroxy and 4-hydroxy-7-methoxy-2H-1,4-benzoxazin-3-ones reacted with nucleophiles such as phenols, indoles and ethanethiol. The major reaction center is the positively-charged nitrogen atom. In the reaction with 2-methylindole, 6-position of the benzoxazinone ring is another major reaction center.     

The preparation of 2H-1,4-benzoxazin-3-(4H)-ones via palladium-catalyzed intramolecular C-O bond formation

Pd/PtBu(3)-catalyzed intramolecular C-O bond formation has been used to access aryl- and alkyl-substituted benzoxazinones.     

Recyclization of 3-phenacylidene-3,4-dihydro-2H-1,4-benzoxazin-2-one under the influence of o-phenylenediamine

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, p. 856, June, 1991.     

Synthesis of 3-phenyl-2H-1,4-benzoxazin-2-one. Revision of some structural assignments

The reported synthesis of 3-phcnyl-2H-1,4-benzoxazin-2-one (II) via brominution of o-acel-amidophenyl phcnaeyl ether (Scheme) leads in lael to the 7-bromo-3-phenyl-2H-1,4-benzoxazin-2-ol (VIII). The structure of the other synthetic intermediates is also revised and a one-step synthesis of the lactone II is reported hy condensation of methyl phenylglyoxalale and o-amino-phenol.     

2-Carbethoxymethyl-4H-3,1-benzoxazin-4-one. 3. Condensation of o-phenylenediamive

3-(2-Benzimidazolyl)-4-hydroxy-2-quinolone was unexpectedly obtained as the principal reaction product on fusion of 2-carbethoxymethyl-4H-3,1-benzoxazin-4-one with o-phenylenediamine. A possible mechanism of its formation is presented.For Communication 2 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–241, February, 1992.     

Facile Synthesis of 2H-1,4-Benzothiazin-3(4H)-ketoximes and 2H-1,4-Benzoselenazin-3(4H)-ketoximes Promoted by SmI2

Abstract

2H-1,4-Benzothiazin-3(4H)-ketoximes and 2H-1,4-benzoselenazin-3(4H)-ketoximes were synthesized by the reductive cyclization of bis(o-nitrophenyl) disulfides or diselenides with aromatic or aliphatic β-nitroethylenes using SmI₂ in moderate to good yields under mild conditions.     

Nitro-substituted 2-phenyl- and 2-(2-tosylaminophenyl)-4H-3,1-benzoxazin-4-one

Nitro-substituted 2-phenyl- and 2-(2-tosylaminophenyl)-4H-3,1-benzoxazin-4-ones were synthesized. The UV, IR, and luminescence spectra were studied. The position of the nitro group affects the strength of the intramolecular hydrogen bond (IHB). The luminescence properties of nitro-substituted 2-(2-tosylaminophenyl)-4H-3,1-benzoxazin-4-ones are associated with the strength of the IHB. The luminescence maximum is shifted to the short-wave region as the IHB becomes stronger.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 616–621, May, 1972.     

Molecular and crystal structure of N-[2H-1,4-benzoxazin-3(4H)-ylidene]-cyclohexane aminium chloride

X-ray diffraction investigation showed that protonation of 4H-benzo-[1,4]-oxazin-3-ylidene-cyclohexylamine occurs at the exocyclic nitrogen atom. In crystal, the cation has a structure with a distinct exocyclic C=N bond.     

Reaction of 2-trifluoromethyl-4H-3,1-benzoxazin-4-one derivatives with carboethoxymethylenetriphenylphosphorane

Treatment of a series of 2-trifluoromethyl-4H-3,1-benzoxazin-4-one derivatives 1 with carboethoxymethyl-enetriphenylphosphorane 2 yielded the phosphoranes 3 in boiling toluene solution. Thermolysis of these phosphoranes 3 gave esters 6.     

2-Carbethoxymethyl-4H-3,1-benzoxazin-4-one. 4. Reaction with anilines

In a solution of DMF, 2-carbethoxymethyl-4H-3,1-benzoxazin-4-one reacts with primarily aromatic amines basically with the formation of the corresponding 2-carbethoxymetlzyl-3-arylquinazolin-4(3H)-ones. Possible mechanisms of these chemical transformations are reported and discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 225–228, February, 1994. Original article submitted June 28, 1993.     

Enantioseparation of 2-O-beta-D-glucopyranosyl-2H-1,4-benzoxazin-3(4H)-one and its 7-chloro-derivative by capillary zone electrophoresis using native and substituted beta-cyclodextrins as chiral additives

Efficient, rapid and inexpensive methods were established for the chiral separation of two glucopyranosyl compounds from plant extracts, by capillary zone electrophoresis (CZE). Baseline separation was achieved for both compounds. Several native cyclodextrins and their derivatives were tried as chiral selectors. CM-beta-CD and HP-beta-CD (with addition of acetonitrile in the buffer) gave rise to optimal chiral separation for the two compounds, respectively, each within a few minutes. The effects of several parameters on the chiral separation were studied.