A mixture of 2.85 g of (2R,6S)-2-hydroxy-6-methyloctyl p-toluenesulfonate obtained in Step 5, 0.8 g of 3,4-dihydro-2H-pyran, 28 ml of diethyl ether, and 0.28 g of p-toluenesulfonic acid was allowed to react in a flask for 6 hours. The resulting solution was poured into 100 ml of a 1% sodium hydrogencarbonate aqueous solution, extracted with diethyl ether, washed with water, and concentrated to obtain 3.58 g of a crude product, which was then purified by HPLC to obtain 2.13 g (99%) of the titled compound.
