By alkylation of sisomicin (I) with acetaldehyde (II) and sodium cyanoborohydride in water with some sulfuric acid.
The reaction of gentamicin B sulfate (betamicin sulfate) (I) with N-(S-3-benzyloxycarbonylamino)-2-hydroxypropionylsuccinimide (II) by means of triethylamine in water-methanol-DMF gives 1-N-(S-3-benzyloxycarbonylamino-2-hydropropionyl)betamicin (III), which is finally hydrogenated with H2 over Pd/C in methanol-water.
The selective triacetylation of sisomicin (I) with zinc acetate, acetic anhydride and TEA in methanol/THF gives the triacetate (II), which is then alkylated with acetic acid and NaBH4 in chloroform, affording 1-N-ethyl-3,2',6'-tri-N-acetylsisomicin (III). Finally, this compound is deacetylated by means of refluxing aqueous NaOH.