I 1703 (OTTO) Isovaleric acid, 99% Cas 503-74-2 - used as perfumes are mainly isovalerate, propyl isovalerate. I 1703 (OTTO) Isovaleric acid, 99% Cas 503-74-2 - used in synthesis for number of pesticides. Additionally, a range of pharmaceuticals, such as butizide, are synthesized from isovaleraldehyde and its corresponding acid.