Stereoselective, Ag-Catalyzed Cyclizations To Access Polysubstituted Pyran Ring Systems: Synthesis of C1-C12 Subunit of Madeirolide A.

The exploration into the scope of a silver-catalyzed cyclization (AgCC) of propargyl benzoates for accessing pyran ring systems has been reported. The impact of the degree of substitution, nature of the substitution on the carbon backbone/benzoate moiety, and stereochemistry has been evaluated. The application of this methodology to the synthesis of the C1-C12 southern fragment of madeirolide A is disclosed.