Abstract: The present disclosure relates to new 11-O-alkyl macrolides and azalides and pharmaceutically acceptable salts and solvates thereof, and to pharmaceutical compositions thereof. The disclosure also relates to a process for the preparation of 11-O-alkyl macrolides and azalides by regioselective 11-O-alkylation of macrolides and azalides having a vicinal diol system, using diazoalkanes in the presence of transition-metal halides or boric acid as catalysts. In another aspect, the disclosure relates to uses of the 11-O-alkyl macrolides and azalides as antibacterial agents or intermediates for the synthesis of other antibacterial agents.