GB1329848A - Process for preparing dibenzofuran derivatives - Google Patents

Abstract

1329848 Usnic acid analogues MEDICA AB OY 1 Dec 1970 [10 Dec 1969] 57033/70 Headings C2A and C2C Usnic-acid-like antibiotics having the Formula Ia or Ib: wherein R 1 is C 1 to C 3 alkyl and R 2 is an acyl group of a hydrocarbyl carboxylic acid in which the hydrocarbyl group contains 2 to 8 carbons, are prepared by oxidizing a phloroglucinol derivative of formula by treatment in a solvent with manganese<SP>III</SP> acetylacetonate to give a hydrousnic acid derivative of formula and then removing one molecule of water from the hydrousnic acid derivative. The preferred compounds (Ia) and (Ib) are those wherein R 1 is as above and R 2 is a butyryl, caproyl or phenyl-acetyl group. The reaction solvent may be aqueous alkali, acetonitrile, chloroform or carbon disulphide, and the reaction solution is preferably purged with nitrogen to remove oxygen before the manganese salt is added. The hydrousnic acid intermediate is preferably isolated, e.g. by extraction with aqueous alkali or by extracting the acidified reaction mixture with chloroform, before the dehydration. The latter procedure is effected by boiling the intermediate with toluene and ptoluenesulphonic acid. The solution is then filtered and extracted with ethanol, and the extract is cooled to crystallize the desired product as a mixture of the isomers (Ia) and (Ib). The isomers may be separated from each other by chromatography and/or crystallization. The compounds (Ia) and (Ib) are said to be novel. They have antibacterial activity against Gram-positive bacteria.