Water → 4,4-Dimethyl-3,5,8-trioxabicyclo[5.1.0]octane

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Reaction Steps

Heptane-toluene (9:1, volume ratio, 350 ml) was added to (S)-1,1′-bi-2-naphthol (1.89 g), and titanium tetraisopropoxide (Ti(OPri)4, 1.95 ml) was added under a nitrogen atmosphere, which was followed by stirring for 10 min at room temperature. (R)-1-Phenethylamine (compound [2], 85 ml), water (0.5 ml) and 4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0]octane (compound [1′], 100 g) obtained by a known method were successively added with stirring, and the mixture was stirred at 40° C. for 24 hr. Toluene was added to the reaction mixture and the mixture was stirred at 40° C. for 1 hr. Then, the mixture was cooled to 10° C. or less over one hour and stirred for one more hour. The crystals in the reaction mixture were collected by filtration and washed with heptane-toluene (2:1, volume ratio) to give (5R,6S)-2,2-dimethyl-6-[(R)-1-phenethylamino]-1,3-dioxepan-5-ol (compound [3′], 159 g, yield 91%) as yellow crystals. mp. 108-109° C.

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