substance isolated according to prior art processes the structure was confirmed by ir spectroscopy fig1 mass spectroscopy fig2 nmr fig3 and uv spectroscopy fig4 fermentation broth 1000 ml obtained by the fermentation of aspergillus terreus atcc 20542 or aspergillus oryzae atcc 74135 and having a ph value of 4 8 an age of 120 hours and a lovastatin content of 300 u03bcg ml lactone acid was acidified with hcl 36 to a ph of 3 5 the fermentation broth was then cooled below 20 u00b0 c butyl acetate 500 ml was added and it was extracted for 4 hours at this tempetrature after the extraction was complete it was centrifuged and the aqueous and organic phases were separated the mycelium and the aqueous phase were discarded and the organic phase was further treated it was concentrated by vacuum distillation at a temperature above 40 u00b0 c to a volume of 50 ml simultaneously with the concentration the lactonisation process took place as well the concentrate was then cooled to a temperature below 20 u00b0 c and left to stand a few hours so that lovastatin crystallized the obtained crude product was recrystallized lovastatin 170 mg in the lactone form having a purity above 90 was obtained fermentation broth 1000 ml obtained by the fermentation of aspergillus terreus atcc 20542.