[O:1]1[C:5]2([CH2:9][CH2:8][NH:7][CH2:6]2)[O:4][CH2:3][CH2:2]1.[CH:10]12[O:16][CH:11]1[CH2:12][CH2:13][CH2:14][CH2:15]2>O>[O:1]1[C:5]2([CH2:9][CH2:8][N:7]([C@H:10]3[CH2:15][CH2:14][CH2:13][CH2:12][C@@H:11]3[OH:16])[CH2:6]2)[O:4][CH2:3][CH2:2]1A mixture of 1,4-dioxa-7-azaspiro[4.4]nonane (23.54 g, step iv, no more than 182 mmol), cyclohexene oxide (22.6 mL, 98%, 219 mmol) and water (7.8 mL) was heated at 80° C. for 2 hours. The reaction mixture was then partitioned between 40% sodium hydroxide aqueous solution (60 mL) and diethyl ether (120 mL). The basic aqueous layer was extracted twice more with diethyl ether (2×120 mL). The combined organic extracts were dried over sodium sulfate and concentrated in vacuo. The residue was then pumped under high vacuum at 50° C. for 1 hour under stirring (to remove the excess of cyclohexene oxide) to yield 32.79 g of the crude title compound (yield 79.3%).
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