Cycloacylation 3-lactone synthesis

Lactones are among the most abundant substructures in natural products." This fact had kindled enormous activity in the field of y-lactone synthesis." 7-Lactones have been prepared by direct cycloacylation of 7-hydroxy acids, eiAer as such or generated as transient intermediates, and by cycloalkyl ation, either of 7-halocarboxylates or of 3,7- or 7,S-unsaturated acids by additions to the double bond. 

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