合成路线1

The selective acetylation of erythromycin B (I) with acetic anhydride in methylene chloride gives the 2'-O-acetyl derivative (II), which is treated with thiocarbonyldiimidazole (CSDI) and DMAP in dichloromethane to yield the 4''-O-thiocarbonyl derivative (III). The reduction of (III) with Bu3SnH in refluxing toluene affords 2'-O-acetyl-4''-deoxyerythromycin B (IV), which is deacetylated in refluxing methanol giving 4''-deoxyerythromycin B (V). The reaction of (V) with AcOH and NaHCO3 yields the hemiketal (VI), which is demethylated at the NMe2 group by means of I2, NaOAc and Na2S2O3 affording the methylamino compound (VII). Finally, this compound is submitted to a reductive alkylation with acetaldehyde (VII) and H2 over Pd/C in methanol.