Process for the preparation of clarithromycin

The present invention includes a process involving a one-pot reaction for preparing erythromycin 9-oxime salt comprising: (a) reacting erythromycin thiocyanate with an ammonium source to obtain erythromycin free base; (b) oximating the C-9 carbonyl of the erythromycin free base by reacting the erythromycin free base with triethylamine and hydroxyl amine hydrochloride to form erythromycin oxime; and (c) reacting the erythromycin oxime obtained in step (b) with an ammonium source to obtain the erythromycin 9-oxime salt. The present invention is also drawn to a one-pot reaction for preparing clarithromycin starting with the one-pot reaction for preparing erythromycin 9-oxime salt, further comprising after step (c): (d) silylating the hydroxy groups at the oxime group, and the 2' and 4'' positions of the erythromycin 9-oxime salt to obtain a silylated derivative; (e) methylating the hydroxy group at the 6 position of the silylated derivative using at least one methylating agent in the presence of at least one inorganic base to obtain SMOP, wherein SMOP is 6-O-methyl-2',4''-bis(trimethylsilyl)-erythromycin A 9-O-(2-methoxyprop-2-yl)oxime; and (f) converting the SMOP into clarithromycin using at least one deoximating agent in the presence of aqueous ethanol.