Abstract: Pure Form II crystals of clarithromycin can be prepared by a simple, high-yield process comprising the steps of treating crude clarithromycin or different crystal forms of clarithromycin with formic acid in an organic solvent to obtain crystalline clarithromycin formate and neutralizing the clarithromycin formate with a base in a mixture of water and a water-miscible organic solvent.

Abstract: High purity Form II crystals of clarithromycin can be easily prepared in a high yield by a process comprising the steps of: protecting the 9-oxime hydroxy group of erythromycin A 9-oxime or a salt thereof with a tropyl group and the 2′- and 4″-hydroxy groups with trimethylsilyl groups; reacting 2′,4″-O-bis(trimethylsilyl)erythromycin A 9-O-tropyloxime with a methylating agent; removing the protecting groups and the oxime group of 2′,4″-O-bis(trimethylsilyl)-6-O-methylerythromycin A 9-O-tropyloxime to obtain crude clarithromycin; treating the crude clarithromycin with methanesulfonic acid in a mixture of a water-miscible organic solvent and water to obtain crystalline clarithromycin mesylate trihydrate; and neutralizing the crystalline clarithromycin mesylate trihydrate with aqueous ammonia in a mixture of a water-miscible organic solvent and water.

Abstract: The present invention elates to a process for preparing paclitaxel represented by formula (1) characterized in that: (a) an oxazolidine derivative represented by formula (2) or its salt in which X represents halogen, is coupled with a 7-trihaloacetyl-baccatin III represented by formula (3) in which R.sub.1 represents trihaloacetyl, in a solvent in the presence of a condensing agent to produce an oxazolidine substituent-containing taxane represented by formula (4) in which X and R.sub.1 are each as previously defined; (b) the oxazolidine ring is opened in a solvent in the presence of an acid, and the product thus obtained is reacted with benzoyl chloride in the presence of a base to produce a protected paclitaxel wherein the hydroxy group at 7-position is protected with trihaloacetyl group represented by formula (5) in which R.sub.1 is as previously defined; (c) then the protecting group at 7-position is removed by ammonia or a salt of ammonia with a weak acid in a solvent.