Abstract: This invention provides 4-N-acylfortimicin B derivatives of the structure ##STR1## wherein R is acyl, aminoacyl, N-monoloweralkylaminoacyl, N,N-diloweralkylaminoacyl, hydroxy-substituted aminoacyl, or substituted aminoacyl of the formula ##STR2## where R.sup.1 is an acyl radical derived from an amino acid or a short peptide, and the pharmaceutically acceptable salts thereof.The compounds are useful as intermediates for preparing 4-N-alkyl or substituted alkylfortimicin B derivatives. In addition to their utility as intermediates, some of the compounds of this invention are also useful as antimicrobial agents.

Abstract: Described are 3-de-O-methylfortimicins A and B and 4-N-acyl and 4-N-alkyl-3-de-O-methylfortimicin B derivatives, and their preparation, which compounds are useful as antibiotics or as intermediates for preparing other useful derivatives having antibacterial activity. The compounds have the following structural formula ##STR1## wherein R is hydrogen, acyl, aminoacyl, N-monoloweralkylaminoacyl, N.N-diloweralkylaminoacyl, hydroxy-substituted aminoacyl, alkyl, aminoalkyl, N-monoloweralkylaminoalkyl, N.N-diloweralkylaminoalkyl or hydroxy-substituted aminoalkyl and the pharmaceutically acceptable salts thereof, for example, salts formed from hydrochloric, sulfuric, and phosphoric acids.