Oxidation of α,β‐Unsaturated Esters and Lactones with Selenium Dioxide to γ‐Oxo or γ‐Hydroxy Derivatives; Synthesis of (±)‐A 26771 B and Norpyrenophorin

The γ‐oxo α,β‐unsaturated lactone moiety COCHCHCOO , which occurs in many macrolide antibiotics, can be synthesized by multicomponent reaction (see previous communication) and oxidation of the lactones thus obtained with SeO 2 . An example is norpyrenophorin 1. The Oxidation with SeO 2 /3% H 2 O yields γ‐hydroxy derivatives.