Natacillin,Bristol Banyu,Japan,1970
To 100 grams of α-aminobenzylpenicillin slurried in 2,500 ml of acetone is
added 200 ml of a 22% solution of potassium ethylhexanoate in dry n-butanol
and the mixture is warmed to 45°C whereupon the acid dissolves. After the
mixture is agitated for 1 hour at 40° to 45°C, the product begins to crystallize
out. Agitation is continued for 4 hours at 45°C after which the product, the
potassium salt of hetacillin, is collected by filtration, washed with 500 ml of
dry acetone, dried for 17 hours at 40°C and found to weigh 70.0 grams.