PREPARATION OF SPIROKETALS BY REACTION OF ANIONS FROM 2-BENZENESULPHONYLTETRAHYDROPYRANS WITH EPOXIDES:SYNTHESIS OF THE C-11 TO C-25 FRAGMENT OF THE MILBEMYCINS

Article abstract of DOI:10.1016/S0040-4039(00)85190-4

Deprotonation of 2-benzenesulphonyltetrahydropyrans with n-butyllithium affords anions which react with substituted epoxides to give spiroketals upon acidification.Using this approach a highly convergent synthesis of the C-11 to C-25 fragment of the milbemycins was achieved.