Emodin synthesis

Previously, we determined that the only known mode of action that is selective for grasses/monocots is acetyl CoA carboxylase inhibition.6 This enzyme is the first of two enzymes involved in de novo fatty acid biosynthesis. This mode of action prevents the synthesis of many essential wax compounds. In order to screen our compounds for this mode of action, we used resistant oat (Avena sp.) seeds. The emodin analogues caused dose-dependent bleaching (Fig. 1.7) and a severe decrease in germination for both resistant and nonresistant grasses. 

Little is known about the biosynthetic origin of hypericin(s) they are related to the anthranoid metabolism and emodin anthrone is possibly their precursor. Synthesis in vitro of hypericin following alkaline dimerization of emodin and oxidation of its reduction derivative, emodine anthrone, has in fact been demonstrated [35,36]. 

The biogenesis of barbaloin has not yet been studied, but its synthesis gives rise to some legitimate speculations thereon. A phenoxide ion can be alkylated on an oxygen atom or on a carbon atom, as shown in the reaction sequence below which reaction predominates depends on the phenol, the conditions employed, and the alkylating agent used. The glycosylation of the anion from aloe-emodin anthrone is an example of reaction b, whereas... 

The synthesis of barbaloin from aloe-emodin anthrone and tetra-0-acetyl-a-D-glucopyranosyl bromide leads to one product only, and no isobarbaloin is formed. It seems justified to assume that this product is a /3-D-glycopyranosyl derivative in which case, one possible explanation of the isobarbaloin-barbaloin relationship is to presume that isobarbaloin is... 

Methylanthracene—Cichrysophanic acid, emodin, or aloin with zinc-dust. 

Genotoxicity tests were performed with senna fruit, senna leaf extract, sennosides, rhein, and aloe-emodin. Senna fruit, sennosides, and rhein did not increase mutation frequencies in the following test systems bacterial systems, mammalian cell culture tests, mouse lymphoma test, chromosome aberration test with Chinese hamster ovary (CHO) cells, bone marrow micronucleus test, chromosome aberration tests, and melanoblast cell test. With aloe-emodin, mutagenic effects were observed only in vitro in the chromosome aberration test with CHO cells and in the Salmonella reverse mutation test. In the in vitro gene mutation test with V79 cells, no mutagenic potential of aloe-emodin was observed. In vivo studies indicated no mutagenic activity of aloe-emodin, and aloe-emodin did not induce unscheduled DNA synthesis in an ex vivo assay performed with hepato-cytes of male rats (Heidemann et al. 1993). 

Biomimetic synthesis of emodine 19 involving intramolecular aldol reactions. 

A new synthesis of emodin has been reported 165) (Scheme 17). Thus the Friedel-Crafts acylation of methyl 3,5-dimethoxybenzoate with 2-methoxy-4-methylbenzoyl chloride followed by hydrolysis of the ester yielded the benzophenone (160). Cyclisation and demethylation was accomplished by treating (160) with an aluminium chloride-sodium chloride melt yielding emodin (161). 

Sala, T., M. V. Sargent, and J. A. Elix Depsidone Synthesis. Part 15. New Metabolites of the Lichen Buellia canescens (Dicks.) De Not Novel Phthalide Catabolites of Depsidones. J. Chem. Soc. (London) Perkin Trans. I 1981, 849. Sankawa, U., Y. Ebizuka, and S. Shibata Biosynthetic Incorporation of Emodin and Emodinanthrone into the Anthraquinoids of Penicillium brunneum and P. islandicum. Tetrahedron Letters 1973, 2125. 

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