Oxalic Acid → (R)-2-hydroxymethylmorpholine oxalate

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To a mixture of 2-hydroxymethylmorpholine and 1,4-oxazepane compound (20.0 g, 2-hydroxymethylmorpholine:1,4-oxazepane compound=75.8:24.2) synthesized in Example 5 were added methanol (100 ml) and oxalic acid (13.6 g, 0.151 mol) and the mixture was stirred for 30 min. Methanol was evaporated under reduced pressure. To the residue was added 2-propanol (50 ml) and the mixture was subjected twice to azeotropic distillation with dehydrating. To the residue after azeotropic distillation with dehydrating was added ethyl acetate (100 ml) at 40° C., and the mixture was cooled to 10° C. After crystallization, the mixture was cooled to 0° C. and stirred for 1 hr. The crystals were collected by filtration, washed withed twice with ethyl acetate (25 ml) and dried (1 mmHg, 40° C.) to give (R)-2-hydroxymethylmorpholine oxalate (12.6 g) (2-hydroxymethylmorpholine:oxalic acid=1:1, yield from (S)-epichlorohydrin 40.5%). The obtained (R)-2-hydroxymethylmorpholine oxalate was analyzed by HPLC to find an optical purity of 99% ee.

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