The acetylation of midecamycin (SF-837 antibiotic) (I) with acetic anhydride in hot pyridine (1,3), or with acetyl chloride and Molecular Sieve 4A-30 in dichloromethane (2,4) gives 9,2',3''-triacetylmidecamycin (II), which is partially deacetylated in hot aqueous methanol.