Synthesis and antibacterial activity of O-methyl derivatives of azalide antibiotics: I. 4″, 11 and 12-OMe derivatives via direct methylation

A series of O-Me derivatives of 9-deoxo-8a-aza-8a-homoerythromycin has been prepared and evaluated for antibacterial activity. The relative rates of methylation of the four available hydroxyls (4″, 6, 11 and 12) in 2′, 3′ -bis-Cbz protected 9-deoxo-8a-aza-8a-homoerythromycin were compared to those given in a published report for the similarly protected 9a-azalide. An incongruity in the results prompted reinvestigation of the O-methylation of the 9a-azalide, and an error in structure assignment in the published report was discovered: the compound reported as the 6-OMe-9a-azalide has been determined to be the 12-OMe derivative.