Useful Synthetic Method for Lactones

Recently, Shiina et al. have been reported a new condensation method using dehydrating condensing agents 1 and 2. In the presence of 1 or 2, carboxylic acids react with nearly equimolar amounts of alcohols or amines to obtain corresponding carboxylic esters or amides in high yields.

1 and 2 perform effectively under Lewis acidic conditions and basic conditions, respectively. Therefore, a wide variety of substrates can be used by choosing 1 and 2.

This method also applies to intramolecular reactions. For example, 1 and 2 have been used the synthesis of the lactone moieties of cephalosporolide D and octalactin B, respectively.

1 and 2 are easy to handle, and condensation reactions using these reagents in this simple procedure have obtained desired products in high yields. 1 and 2 are quite effective as dehydrating condensing agents in the synthesis of carboxylic esters and amides, especially, when synthesizing lactones and lactams.