[O:1]1[CH:6]=[CH:5][CH2:4][CH2:3][CH2:2]1.[OH:7][C@H:8]([CH3:17])[C:9]([N:11]1[CH2:16][CH2:15][O:14][CH2:13][CH2:12]1)=[O:10].O.C1(C)C=CC(S(O)(=O)=O)=CC=1>ClCCl>[O:1]1[CH2:2][CH2:3][CH2:4][CH2:5][CH:6]1[O:7][C@H:8]([CH3:17])[C:9]([N:11]1[CH2:12][CH2:13][O:14][CH2:15][CH2:16]1)=[O:10]3,4-Dihydro-2H-pyran (90.5 ml, 1.2 eq) was added dropwise to a mixture of 4-[(R)-2-hydroxypropionyl]morpholine (132 g) and p-toluenesulfonic acid monohydrate (500 mg, 0.003 eq) in dry dichloromethane (500 ml) over a period of 15 min with stirring at 0° C. After being stirred for 30 min at 0° C., the mixture was washed with aqueous sodium bicarbonate, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. Purification of the residue by silica gel chromatography, using n-hexane: ethyl acetate (8:1)˜ethyl acetate as an eluent, gave 4-[(2R)-2-(3,4,5,6-Tetrahydro-2H-pyran-2-yloxy)propionyl]morpholine (191.6 g, 95% yield) as a pale yellow oil.
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