The oxidation of Josamycin (I) with CrO3 and pyridine, followed by reaction with Ac2O, AcCl and methanol gives the macrocyclic dimethyl acetal (II), which is treated with NaBH4 and a Ru catalyst to promote a ring contraction yielding the 14-member macrocycle (III). The reduction of the double bond of (III) with H2 over PtO2 affords the saturated macrocycle (IV), which is treated first with MsCl and TEA and then with NaN3 to afford the azido macrocycle (V). The treatment of (V) with TFA provides the azido aldehyde (VI), which is finally reduced to the corresponding amine and simultaneously methylated by means of H2 over Pd/C in the presence of formaldehyde to furnish the target 14-member macrocyclic lactone.

The oxidation of Josamycin (I) with CrO3 and pyridine, followed by reaction with Ac2O, AcCl and methanol gives the macrocyclic dimethyl acetal (II), which is treated with NaBH4 and a Ru catalyst to promote a ring contraction yielding the 14-member macrocycle (III). The reaction of (III), first with MsCl and TEA, and then with NaN3 affords the azido macrocycle (IV), which is reduced with PPh3 in THF/water to provide the amino compound (V). The reductive methylation of (V) with CH2O and NaBH3CN gives the dimethylamino compound (VI). Finally, compound (VI) is treated with TFA in acetonitrile to furnish the target 14-member macrocyclic lactone.