Occurrence of Aldehydes and Ketones

Natural Products

Aldehydes and ketones are widespread in nature, often combined with other functional groups. Example are shown in the following diagram. The compounds in the top row are found chiefly in plants or microorganisms; those in the bottom row have animal origins. With the exception of the first three compounds (top row) these molecular structures are all chiral. When chiral compounds are found in nature they are usually enantiomerically pure, although different sources may yield different enantiomers. For example, carvone is found as its levorotatory (R)-enantiomer in spearmint oil, whereas, caraway seeds contain the dextrorotatory (S)-enantiomer.
Note that the aldehyde function is often written as –CHO in condensed or complex formulas.