Highly Stereoselective Diels-Alder-Based Strategy for the Synthesis of 3- epi -Formicin A and 1- epi -Formicin B.

The first enantioselective approach based on a highly stereoselective Diels-Alder reaction for the synthesis of 3- epi -formicin A and 1- epi -formicin B with rare N -acetylcysteamine-containing indenone thioesters is reported. The strategy utilizes a key Diels-Alder reaction to form the core hydrindane system with three contiguous stereocenters in very high levels of diastereo- and regioselectivity and one-pot oxidation/isomerization/dehydrogenation. The scope of this method was tested with different substrates to give cycloadducts in a highly diastereoselective manner.