N-Demethyl roxithromycin

3-decladinosyl roxithromycin and roxithromycin Z are specified related substances to be controlled in European Pharmacopoeia 7.0

which are derived from roxithromycin. These compounds are required for its routine assay

however cannot be commercially available in China.The related substances were synthesized according to a new procedure developed from previous methods.In the producing process

erythromycin A 9-(Z)-oxime was produced from erythromycin A 9-(E)-oxime in the presence of a strong base.Roxithromycin Z was synthesized by the reaction between erythromycin A 9-(Z)-oxime and methoxyethoxy methyl chloride ether in ethyl acetate at a low temperature

such as lower than 5℃.Roxithromycin Z was then separated with silica chromatography and purified by semi-preparative HPLC.N-Demethyl roxithromycin was prepared by N-demethylation of roxithromycin with iodine and sodium acetate in aqueous solution of sodium hydroxide（pH=8—9)

and was purified by two-stage recrystallization.And 3-decladinosyl roxithromycin was obtained through a process of acidic hydrolysis catalyzed by aqueous hydrochloride at room temperature

and was also purified by silica chromatography and semi-preparative HPLC.All three compounds

N-demethyl roxithromycin

3-decladinosyl roxithromycin and roxithromycin Z were determined by HPLC to high purity of over 95%.Their structures were identified by MS

1H NMR and 13C NMR.In this paper

three producing routes of the compounds have been established successfully.The obtained compounds would provide a new standard reference of roxithromycin for drug assay in Chinese Pharmacopieia.