Abstract The twelve isomeric gem-dimethylphenylvalerolactones may each in principle be obtained by one of the general methods:(i) selective reduction of the corresponding trisubstituted glutaric anhydride,(ii) selective reduction of a gem-dimethyl-5-oxo-5- phenylvaleric acid, or (iii) selective reaction of 2-or 3-phenylglutaric anhydride with 2 moles of methylmagnesium iodide. Substituted glutaric anhydrides for method (i) were obtained ...