Patent ID: 6916792

Claim:
A process for producing an erythromycin compound which is a 2′-O-acetyl-4″-O-formyl-8,9-anhydroerythromycin A 6,9-hemiketal compound 4 represented by the formula (4): wherein R 1 and R 2 each independently represent a lower alkyl group, which comprises reacting a 2′-O-acetylerythromycin A compound 2 represented by the formula (2): wherein R 1 and R 2 have the same meanings as defined above, with a formylating agent to obtain a 2′-O-acetyl-4″-O-formylerythromycin A compound 3 represented by the formula (3): wherein R 1 and R 2 have the same meanings as defined above, then, reacting Compound 3 with an acid to subject to hemiketalation, and adding an aqueous basic solution in an aqueous solution to precipitate Compound 4 as free crystals.