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To a suspension of 7-bromo-4-fluoro-2-methoxy-9H-xanthen-9-one (25.00 g, 77 mmol) and trimethylsulfonium iodide (23.68 g, 116 mmol) in DMSO (130 mL)/THF (130 mL) was added drop wise potassium tert-butoxide (1M in THF) (116 mL, 116 mmol). After 15 min at RT trimethylsilyl azide (20.54 mL, 155 mmol) was added. The reaction mixture was stirred for additional 40 minutes and then quenched by addition of 100 ml of saturated aqueous sodium bicarbonate. After stirring for 10 minutes EtOAc (100 ml) and water (100 ml were added and the layers were separated. The organic layer was washed with water (3×100 ml), brine (100 ml) and dried over MgSO4. The solvent was removed under reduced pressure to obtain a yellow residue which was dissolved in 250 ml THF. The solution was cooled to 0° C. and LAH (1 M in THF, 108 mL, 108 mmol) was added drop wise. After 5 minutes at 0° C. the reaction mixture was allowed to warm to RT. The reaction mixture was cooled again to 0° C. and sodium sulfate decahydrate (21.98 g, 155 mmol) was added portion wise. The mixture was stirred for 5 minutes and diluted with 100 ml EtOAc. The reaction mixture was filtered through a pad of Celite and the filter cake was washed with EtOAc (100 ml). The filtrate was concentrated under reduced pressure to obtain a yellow foam which was re-crystallized from DCM to afford (9-amino-7-bromo-4-fluoro-2-methoxy-9H-xanthen-9-yl)methanol as a white solid. Step 2: A solution of (9-amino-7-bromo-4-fluoro-2-methoxy-9H-xanthen-9-yl)methanol (9.83 g, 27.8 mmol) in THF (46.3 mL) was sequentially treated with lithium t-butoxide (1 M in THF) (30.5 mL, 30.5 mmol) and 2-bromoacetonitrile (2.90 mL, 41.6 mmol) at RT. After 2.5 hours reaction time, additional 0.5 equivalent lithium t-butoxide and 2-bromoacetonitrile (1.5 mL) were added. After 4 hours reaction time, an additional 0.25 equivalent lithium t-butoxide and bromoacetonitrile (0.75 mL) were added. After 5 hours reaction time another 0.25 equivalent of lithium t-butoxide and bromoacetonitrile (0.75 mL) were added to the mixture. Water (100 ml) was added and solvents were removed under reduced pressure. The aqueous residue was filtered, the solid was washed twice with water, dried under reduced pressure and re-suspended in ethanol. The solid was filtered off, washed with ethanol and dried under reduced pressure to afford 2-((9-amino-7-bromo-4-fluoro-2-methoxy-9H-xanthen-9-yl)methoxy)acetonitrile. Step 3: To a solution of 2-((9-amino-7-bromo-4-fluoro-2-methoxy-9H-xanthen-9-yl)methoxy)acetonitrile (7.72 g, 19.63 mmol) in DCE (115 mL) was added trimethylaluminum (2M in toluene) (19.63 mL, 39.3 mmol) at RT. The reaction mixture was stirred for 10 min at RT and then heated to 75° C. for 1 hour. The reaction mixture was cooled to RT and quenched with sodium sulfate decahydrate. The reaction mixture was vigorously stirred for 30 minutes, diluted with EtOAc and stirred overnight. The mixture was filtered through a pad of celite and filter cake was washed with EtOAc. The solvent was removed under reduced pressure to obtain an oily residue which crystallized to give 7′-bromo-4′-fluoro-2′-methoxy-2,6-dihydrospiro[[1,4]oxazine-3,9′-xanthen]-5-amine (7.49 g, 19.05 mmol, 97% yield) as a cream-colored solid. Step 4: Intermediates (R)-7′-bromo-4′-fluoro-2′-methoxy-2,6-dihydrospiro[[1,4]oxazine-3,9′-xanthen]-5-amine (13A) and (S)-7′-bromo-4′-fluoro-2′-methoxy-2,6-dihydrospiro[[1,4]oxazine-3,9′-xanthen]-5-amine (13B) were obtained from racemic product, 7′-bromo-4′-fluoro-2′-methoxy-2,6-dihydrospiro[[1,4]oxazine-3,9′-xanthen]-5-amine (Intermediate 13) using similar chiral separation conditions as described herein for intermediate 10.

1. customquenched by addition of 100 ml of saturated aqueous sodium bicarbonate
2. stirringAfter stirring for 10 minutes EtOAc (100 ml) and water (100 ml
3. additionwere added
4. customthe layers were separated
5. washThe organic layer was washed with water (3×100 ml), brine (100 ml)
6. dry with materialdried over MgSO4
7. customThe solvent was removed under reduced pressure
8. customto obtain a yellow residue which
9. waitAfter 5 minutes at 0° C. the reaction mixture was allowed
10. temperatureto warm to RT
11. temperatureThe reaction mixture was cooled again to 0° C.
12. stirringThe mixture was stirred for 5 minutes
13. filtrationThe reaction mixture was filtered through a pad of Celite
14. washthe filter cake was washed with EtOAc (100 ml)
15. concentrationThe filtrate was concentrated under reduced pressure
16. customto obtain a yellow foam which
17. customwas re-crystallized from DCM