1: 3-methoxy-2-methyl-2-cyclopenten-1-one With lithium diisopropyl amide in tetrahydrofuran T=-78°C; Metallation; 1.5 h; 2: methyl iodide in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide T=-78°C; Methylation; 1 h;