Isoamyl isovalerate

Description and usage notes:

Fresh, fruity top-note material. Useful for adding realism to the top-notes of chocolate, apple, goosberry and other fruits, Champagne and cider accords.  This material occurs widely in nature being found fruits such as apple, banana and tomato, alcoholic beverages such as beer and cognac and, perhaps less obviously, in various mint and eucalyptus oils.

Arctander gives an interesting description of this material “Peculiar fruity odor reminiscent of ripe apples, or more like the overwhelmingly choking odor of apples stored in a warehouse, almost a ‘fermented’ apple odor.”