1: 3,4,5,6-Tetrahydro-2H-pyran-4-carboxylic acid With n-butyllithium; diisopropylamine in tetrahydrofuran; hexane T=0 - 50°C; 3.41667 h; 2: methyl iodide in tetrahydrofuran; hexane T=0 - 20°C; 3: With water; citric acid in tetrahydrofuran; hexane

sodium hydroxide in water T=20°C; 24 h;