Clarithromycin related compound C

In the manufacturing process for Biaxin (clarithromycin), erythromycin-A oxime, an intermediate, is obtained in high yield, when erythromycin-A is treated with hydroxylamine/isopropyl alcohol in the presence of acetic acid. An unusual impurity, the desosamine hydrazinium salt, is generated in this step of the synthetic pathway, and has been isolated and characterized by using one and two-dimensional NMR spectroscopy in conjunction with MS and EDS.

A series of novel 3-O-(3-aryl-propenyl)clarithromycin derivatives were designed, synthesized and evaluated for their in vitro antibacterial activities. Regioselective allylation at 3-OH was efficiently achieved in the presence of 9-oxime ether, compared with 9-keto. Most of the side chains were identified as the 3-O-(3-aryl-Z-prop-1-enyl) group, not the expected 3-O-(3-aryl-E-prop-2-enyl) group. Some derivatives of this series showed improved activities against erythromycin-resistant Staphylococcus aureus and Staphylococcus pneumoniae compared with the reference compound, clarithromycin, but weaker activities against susceptible strains.

A series of O-alkylated derivatives of erythromycin (EM) has been prepared and their biological properties were evaluated. Among them, clarithromycin (CAM, 6-O-methylerythromycin) exhibits most potent in vitro and in vivo antibacterial activities, higher acid-stability than EM and favorable pharmacokinetic properties as an antibiotic. CAM was originally synthesized via methylation of 2'-O,3'-N-bis(benzyl-oxycarbonyl)-N-demethylerythromycin in low yield, because of the less selectivity of 6-O-methylation. The selective 6-O-methylation was achieved using the erythromycin 9-oxime derivative as a key intermediate. By the further investigation on the protective groups of 9-oxime and desosamine moiety, the production process of CAM on an industrial scale has been established via methylation of 2',4''-O-bis(trimethylsilyl)erythromycin 9-[O-(1-isopropoxycyclohexyl)oxime] in more than 45% overall yield. CAM has the same antibacterial spectra as EM and is active against aerobic Gram-positive bacteria, some Gram-negative bacteria, anaerobic bacteria, Mycoplasma and Chlamydia.

2',4''-O-Bis(trimethylsilyl)erythromycin A-9-O-(1-isopropoxycyclohexyl)oxime (2',4''-TMS-EMIPCH) and 2',4''-O-bis(trimethylsilyl)-6-O-methylerythromycin A-9-O-(1-isopropoxycyclohexyl)oxime (2',4"-TMS-IPCH) are the key intermediates for manufacturing clarithromycin. A qualitative and quantitative method for baseline separation of E- and Z-isomers and related process substances has been established. A DIKMA-Inertsil ODS-3 column (150 mm x 4.6 mm i.d., 5 microm) was used. The column temperature was maintained at 40 degrees C. The mobile phase was CH3CN-H2O (95:5, v/v). The flow rate was 1.5 mL/min and the detection wavelength was UV 205 nm. Good linearities for E-2',4''-TMS-EMIPCH and E-2',4''-TMS-IPCH were obtained in the ranges of 6-60 microg (r = 0.9994) and 6-72 microg (r = 0.9998), respectively. The method described has also been demonstrated to work equally well on other 2',4''-O-bis(trimethylsilyl)erythromycin 9-oxime hydroxyl derivatives, which provided the criterion for optimizing the protective groups at 9-oxime hydroxyl position and the study of regioselectivity of methylation at the 6-OH position.