α-Isomethyl ionone, also known as α-cetone, is a synthetically made and naturally occurring organic compound found in Brewer's yeasts or the species known as Saccharomyces cerevisiae.

[6] Perfume fragrances that α-isomethyl ionone is used in are for example, amber, chypre, violet, mimosa, reseda, iris, orris, cyclamen, chypre, berries, woody notes, ylang-ylang, leather, orange, nut, pistachio, muscatel, and tobacco.

[6] α-Isomethyl ionone would be classified as a norsesquiterpenoid, having 14 carbon atoms (1 less than the 15 of three consecutive isoprene units).

[6] The synthesis of α-isomethyl ionone involves a cross-aldol condensation of citral with methyl ethyl ketone[8] A high temperature and strong alkali is used.

The ratio between the n-form and iso-form is controlled in order to obtain methyl pseudo-ionone and allow ring formation to occur.