1: (rac)-4,4'-dihydroxy-7,7'-dimethoxy-5,5'-dimethyl-2H,2'H-8,8'-bichromene-2,2'-dione With sodium hydride in N,N,N',N',N'',N''-hexamethylphosphoric triamide 2: dimethyl sulfate in N,N,N',N',N'',N''-hexamethylphosphoric triamide T=20°C; 2 h;