FIELD: chemical technology, antibiotics. SUBSTANCE: method involves dissolving technical phenoxymethylpenicillin (basic substance content is 60%) in butyl acetate containing 1-5 wt.-% of acetic acid, separation of insoluble impurities from solution by filtration and isolation of the end product from the obtained solution. Yield of phenoxymethylpenicillin potassium salt is about 89% of theory (as measured for technical product), activity is 1515 U/mg (theoretical activity is 1530 U/mg). Phenoxymethylpenicillin acid can be obtained from its potassium salt at yield 97%. The end product is used in medicine and as an intermediate product for synthesis of semisynthetic β-lactam antibiotics. EFFECT: improved method of preparing, high yield of the end product. 1 dwg
