NEW ONE-STEP PROCESS FOR THE SYNTHESIS OF FUNCTIONALIZED 1,6-DIOXASPIRO[4,5]DECANES

beta-Phenylsulfonyl dihydrofurans 1 were readily prepared by reduction of alpha-phenylsulfonyl-gamma-lactones with DIBAL-H, followed by dehy dration with MsCl-Et(3)N. Dihydrofurans 1 were deprotonated with n-BuL i and the resulting alpha-lithiated carbanion reacted with a wide vari ety of electrophiles. Particularly interesting is its reaction with ga mma-lactones because affords 1,6-dioxaspiro[4,5]decanes in good yields in one-step procedure. This new method of synthesis of spiroketals, i n non-acid conditions, is thermodynamically controlled and occurs with high stereoselectivity at C-4, C-5 and C-7, but not at C-2.