To a solution of 5-cyclohex-1-enyl-3-[(trans-4-hydroxy-cyclohexyl)-(trans-4-methyl-cyclohexanecarbonyl)-amino]-thiophene-2-carboxylic acid methyl ester (1 g, 2.18 mmol) in dichloromethane (10 mL) was added diisopropyl ethylamine (0.6 mL, 3.3 mmol), chloromethyl methyl ether (250 μL, 3.3 mmol) and DMAP (40 mg, 0.33 mmol). The reaction mixture was refluxed for 12 h. Solvents were removed and the residue as purified by silica gel column chromatography using ethyl acetate and hexane (1:3) as eluent to obtain 5-cyclohex-1-enyl-3-[(trans-4-methoxymethoxy-cyclohexyl)-(trans-4-methyl-cyclohexanecarbonyl)-amino]-thiophene-2-carboxylic acid methyl ester (780 mg, 71%) as a syrup.
