Pseudomonic acid (10.00 g, 20 mmole) was dissolved in methyl tertbutyl ether (150 ml) at 45° C. Calcium-2-ethyl-hexanoate (3.32 g, 10 mmole) was suspended in water (30 ml). The solution of pseudomonic acid was added to the calcium-2-ethyl-hexanoate suspension, and the resulting two phases system were stirred for 14 hours. The two phases were then separated, and water (20 ml) and methyl tertbutyl ether (50 ml) was added to the aqueous phase, and was stirred for 10 minutes. The resulting two phases were separated, and any traces of methyl tertbutyl ether was evaporated from the aqueous phase. The aqueous mupirocin calcium suspension was cooled in a refrigerator at 5° C. The solid mupirocin calcium dihydrate was filtered, washed with 20 ml water and dried under vacuum at 35° C. for 5 hours. The mass of product was 5.88 grams.
