Closely related to EC 2.3.1.74, naringenin-chalcone synthase. The product, 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one, is phloroisovalerophenone. Also acts on isobutyryl-CoA as substrate to give phlorisobutyrophenone. The products are intermediates in the biosynthesis of the bitter (¦Á) acids in hops (Humulus lupulus).