To a suspension of the compound of formula (IX) (5 g, 21 mmol) and 2-(methylsulfonyl)ethanamine hydrochloride (4.1 g, 33 mmol) in THF (150 mL) was added acetic acid (5 g, 83 mmol) followed by DIPEA (10.5 g, 83 mmol). The mixture was stirred at 35° C. (internal temperature) for 2.5 h and was then cooled to 20° C. (internal temperature). Sodium tri-acetoxyborohydride (8.8 g, 42 mmol) was added and the mixture was stirred at ambient temperature the reaction was complete (TLC analysis). 25% Aqueous sodium hydroxide (10 mL) and water (50 mL) were added and the mixture was stirred for 30 min The liquid phases were separated and the aqueous layer was extracted with THF (50 mL). The extract was combined with the former organic layer and the mixture was washed with saturated aqueous NH4Cl (50 mL). The organic layer was concentrated under vacuum. The crude product was purified by column chromatography, eluting with 5% MeOH in DCM providing the compound of formula (XI) (3.1 g) after evaporation of the product containing fractions. The compound of formula (XI): 1H NMR (300 MHz, d6-DMSO): δ 2.94 (dt, J=13.8 Hz, J=7.05 Hz, 1H), 3.00 (s, 1H), 3.24 (t, J=6.75 Hz, 1H), 3.77 (s, 1H), 6.42 (d, J=3.3 Hz, 1H), 7.03 (d, J=3.0 Hz, 1H), 7.68 (d, J=8.4 Hz, 1H), 8.06 (s, 1H), 8.09 (dd, J=8.55 Hz, J=2.25 Hz, 1H), 8.31 (d, J=2.1 Hz, 1H).
