Abstract An efficient methodology for converting Δ 2-milbemycin A 4 is described, whereby the Δ 2-isomer is initially converted to the C 2 epimer which in turn is epimerized at C 2 to its natural configuration. The key transformation is a Dess-Martin type oxidation at C 5 of the C 2 epimer in order to enhance the stability of the Δ 3-double bond and facilitate epimerization.
