Benzyl orsellinate

Benzyl orsellinate, Benzyl 2,4-dihydroxy-6-methylbenzoate (Orsellin-saurebenzylester, 2,4-Dihydroxy-6-methylbenzoesaurebenzylester)... 

LasalUa asiae-orientalis benzoic acid and benzyl orsellinate with TFAA and subsequent debenzylation (666, Z... 

Methyl orsellinate 31 was differentially protected and formylated to give 33 after removal of the isopropyl group with TiCl4. Benzylation and oxidation gave the benzoic acid 34 ready for a surprising conclusion to the synthesis. 

Aigialomycin D is a metabolite of the mangrove fungus Mgialus parvus and was shown to be a kinase inhibitor with modest antimalarial activity. The convergent synthesis showcased here assembled three fragments into the full carbon skeleton (Scheme 836). The ester-containing benzylic bromide 134 was prepared from methyl orsellinate, itself derived from methyl acetoacetate. Thioacetate 135 was formed from d-ribose as will be described, while homoallylic alcohol 136 was commercially available. 

Route A involves the condensation of appropriately substituted phloro-glucinol derivatives with substituted orsellinic acid derivatives in the presence of anhydrous zinc chloride and phosphorus oxychloride. The analogous condensation in the presence of trifluoroacetic anhydride yielded the xanthone (150) (C-acylated product) as a minor byproduct together with the major aryl ester (151) (0-acylated product). However trifluoroacetic anhydride has become the reagent of choice (route B) since the use of 0-methyl and 0-benzyl protecting groups has enabled good yields of the xanthones to be obtained. 

Preparation by hydrogenolysis of 2,2, 4 -tris-(benzyloxy)-3,5-dibromo-6-methoxy-4,6 -dimethyl-benzophenone (SM) in ethanol/trifluoroacetic acid mixture in the presence of 10% Pd/C at atmospheric pressure (quantitative yield). SM was obtained by condensation of 0-benzyl-0-methyl-3,5-dibromo-y-orsellinic acid— 2-(benzyloxy)-3,5-dibromo-6-methoxy-4-methylbenzoic acid—with orcinol dibenzyl ether in the presence of nifluoroacetic anhydride/trifluoroacetic acid mixture under nihogen in refluxing chloroform for 6.25 h [1376]. m.p. and Spectra (NA). 

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See also in sourсe #XX -- [ ]

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