Unexpected α,β-unsaturated products of reductive amination of the macrolide antibiotic josamycin

Reductive amination of the macrolide antibiotic josamycin with alkyl amines, using three different reducing agents: NaBH3CN, NaBH4 and NaBH(OAc)3, yields surprisingly different major products which are identified as either Lewis complexes, aminoalkyl derivatives or α,β-unsaturated derivatives of josamycin by 1H and 13C NMR, FT-IR and ESI MS methods.