Synthesis of Macrocyclic Dilactones by Cyclization of Sulfonium Salts

Article abstract of DOI:10.1021/jo00040a013

An efficient method for the formation of macrocyclic dilactones via cyclization of (ω-carboxyalkyl)diphenylsulfonium salts 3 containing an ester linkage under mild conditions is described.These sulfonium salts 3 were cyclized in the presence of cesium carbonate under high-dilution conditions to give 11- to 16-membered dilactones 4 in good yields.The cyclization of sulfonium salt 22 was successfully carried out for the synthesis of 11-membered dilactonic pyrrolizidine alkaloid, 13,13-dimethyl-1,2-didehydrocrotalanine 23.