Synthetic studies towards (+)-Dihydroampullicin. Michael addition of N-Boc-2-(tert-butyldimethylsiloxy)-3-methyl-pyrrole to α-methylene lactones

The Michael addition of N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsiloxy)-3-methyl-pyrrole (4) to several alpha -methylene lactones catalyzed by fluoride ions yielded the corresponding homologated products (26-30) with good yields. Application of this reaction to the sililoxy bicyclic lactone (5) allowed us to isolate the tricyclic lactone (26), a highly valuable intermediate in our synthetic strategy leading to the growth regulator (+)-Dihydroampullicin (1). (C) 2000 Elsevier Science Ltd. All rights reserved.