Biotransformation of the Brassica Phytoalexin Brassicanal A by the Blackleg Fungus

Pedras, M. Soledade C.; Khan, Adnan

doi:10.1021/jf960098u

Cited by 51 publications

(32 citation statements)

References 12 publications

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“…This afforded 21.9 mg of brassicanal A (100% yield): HPLC tr ) 10.2 min. Remaining data were identical to those previously reported (Pedras and Khan, 1996;Monde et al, 1990).…”

Section: Methodssupporting

confidence: 87%

Strategies of Cruciferous Pathogenic Fungi: Detoxification of the Phytoalexin Cyclobrassinin by Mimicry

Pedras

Okanga

1999

J. Agric. Food Chem.

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The remarkable metabolism of the cruciferous phytoalexin cyclobrassinin by the phytopathogenic root rot (Rhizoctonia solani Kuhn) and blackleg [Phoma lingam (Tode ex Fr.) Desm., asexual stage of Leptosphaeria maculans (Desm.) Ces. et de Not.] fungi is reported. It was established that R. solani metabolized and detoxified cyclobrassinin via the phytoalexin brassicanal A, which was further transformed into nontoxic products. Detoxification of cyclobrassinin in P. lingam avirulent isolate Unity occurred via the phytoalexin brassilexin, whereas the detoxification in P. lingam virulent isolate BJ 125 occurred via the phytoalexin dioxibrassinin. The chemistry involved in the structure determination of the intermediates of these three apparently different pathways and their antifungal activities are described. In addition, efficient syntheses of both phytoalexins brassicanal A and brassilexin by mimicry of the fungal biotransformation route are reported. Implications of these unprecedented transformations are discussed.

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“…This afforded 21.9 mg of brassicanal A (100% yield): HPLC tr ) 10.2 min. Remaining data were identical to those previously reported (Pedras and Khan, 1996;Monde et al, 1990).…”

Section: Methodssupporting

confidence: 87%

Strategies of Cruciferous Pathogenic Fungi: Detoxification of the Phytoalexin Cyclobrassinin by Mimicry

Pedras

Okanga

1999

J. Agric. Food Chem.

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“…Sulfides 1a-1g [12,[69][70][71] and racemic sulfoxides [12] (applied as standards for the determination of the ee values) were prepared according to the reported procedures. Unless otherwise stated the 1 H and 13 C NMR spectra were recorded in CDCl 3 on Varian 300 or 400 MHz spectrometers.…”

Section: Methodsmentioning

confidence: 99%

Mechanism of the Asymmetric Sulfoxidation in the Esomeprazole Process: Effects of the Imidazole Backbone for the Enantioselection

2009

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Abstract:The asymmetric sulfoxidation reaction of imidazole-based prochiral sulfides was studied to explore the mechanistic details of the highly efficient esomeprazole process, which is one of the few industrial scale catalytic asymmetric procedures. The synthetic studies revealed that the smallest subunit governing the selectivity in the esomeprazole process is an imidazole ring. Thus, by using the esomeprazole procedure methyl imidazole sulfide could be oxidized as efficiently as its several functionalized derivatives, including pyrmetazol. However, alkylation of the imidazole nitrogen led to a major drop of the enantioselectivity. Our atmospheric pressure chemical ionization-mass spectrometry (APCI/MS) studies indicate that addition of small amounts of water to the reaction mixture facilitates the formation of mononuclear titanium species, which are the active catalytic intermediates of the selective oxidation reaction. One of the most important features of the esomeprazole procedure is that amine additives increase the enantioselectivity of the oxidation process. The NMR studies of the presumed reaction intermediates show that under catalytic conditions the amines are able to coordinate to titanium and dissociate the coordinated imidazole substrate. The density functional theory (DFT) modelling studies provided new insights in the mechanism of the asymmetric induction. It was found that the oxidation requires a lower activation energy if the imidazole sulfide precursor does not coordinate to titanium. Two possible reaction paths were explored for this out of sphere oxidation mechanism. The most important interaction governing the enantioselection is hydrogen bonding between the N À H of the imidazole ring and the chiral tartrate ligand on titanium. Furthermore, the oxidation reaction imposes an important structural constraint to the TS structure involving a linear arrangement of the peroxide oxygens and the sulfur atom. This constraint and the N coordination of imidazole leads to a very strained structure for the inner sphere mechanism of the oxidation, which leads to a much higher activation barrier than the corresponding out of sphere process, and therefore it is unlikely.

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“…maculans (virulent isolate BJ-125, IBCN collection, AAFC) was grown on V8 agar under continuous light at 23 ± 1°C; after 15 days, the fungal spores were collected and stored at À20°C (Pedras and Khan, 1996). Liquid cultures were initiated by inoculating minimal media (Pedras and Biesenthal, 1998) with fungal spores at different concentrations described below in Erlenmeyer flasks followed by incubation on a shaker under constant light at 23 ± 1°C.…”

Section: Fungal Cultures and Antifungal Assaysmentioning

confidence: 99%

Camalexin induces detoxification of the phytoalexin brassinin in the plant pathogen Leptosphaeria maculans

Pedras¹,

Jha²,

Okeola³

2005

Phytochemistry

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Biotransformation of the Brassica Phytoalexin Brassicanal A by the Blackleg Fungus

Cited by 51 publications

References 12 publications

Strategies of Cruciferous Pathogenic Fungi: Detoxification of the Phytoalexin Cyclobrassinin by Mimicry

Strategies of Cruciferous Pathogenic Fungi: Detoxification of the Phytoalexin Cyclobrassinin by Mimicry

Mechanism of the Asymmetric Sulfoxidation in the Esomeprazole Process: Effects of the Imidazole Backbone for the Enantioselection

Camalexin induces detoxification of the phytoalexin brassinin in the plant pathogen Leptosphaeria maculans

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