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0 °C

Under an atmosphere of nitrogen, a mixture of 250 mg of magnesium, 2.8 g of 5-bromo-1-(tetrahydropyran-2-yloxy)pentane, 200 μl of ethyl bromide, a trace amount of iodine and 4 ml of tetrahydrofuran was refluxed with heating for one hour. To it were added 516 mg of crotonic acid sec-butyl ester and 14 mg of cuprous chloride at 0° C. over a period of 30 minutes, the mixture stirred at 0° C. for 15 minutes, and then at room temperature for one hour. The reaction mixture was poured into a saturated aqueous solution of ammonium chloride, extracted with ethyl acetate, the extract washed with a saturated aqueous solution of sodium chloride, dried over magnesium sulphate and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel using a mixture of methylene chloride and ethyl acetate (20:1) as eluent to give 529 mg of the subtitle compound having the following physical characteristics:

1. temperaturewith heating for one hour
2. waitat room temperature for one hour
3. extractionextracted with ethyl acetate
4. washthe extract washed with a saturated aqueous solution of sodium chloride
5. dry with materialdried over magnesium sulphate
6. concentrationconcentrated under reduced pressure
7. customThe residue was purified by column chromatography on silica gel using
8. additiona mixture of methylene chloride and ethyl acetate (20:1) as eluent