These are a kind of cyclic ester. They are formed when the acid and alcohol functions are part of the same molecule. In other words, they are cyclic esters and occur in a wide range of natural substances.

Wine lactone

An ester with a sweet coconut odour was recently found to cause the smell and flavour of many white wines.

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This molecule (3a, 4, 5, 7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one) has been identified in a number of wines, as well as being synthesised. There are three chiral carbons, and the one of the eight isomers (all have been synthesised) that has the highest activity has been identified; it is identical with the lactone found in the wines.

It has also been found in orange juice and in black pepper.