Sodium Bicarbonate → tert-Butyl 2-(N-cyclohexyl-3-(3-((4-(2,2,2-trifluoroacetyl)-1-oxa-4,9-diazaspiro[5.5]undecan-9-yl)methyl)phenethoxy)propanamido)ethyl(2-(5-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-8-yl)ethyl)carbamate

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Reaction Steps

A solution of 2,2,2-trifluoro-1-(1-oxa-4,9-diazaspiro[5.5]undecan-4-yl)ethanone trifluoroacetate [Example 9, step a] (4.5 g) in NMP (30 mL) was treated with acetic acid (0.6 mL), stirred for 5 minutes, and then added in one portion to tert-butyl 2-(N-cyclohexyl-3-(3-formylphenethoxy)propanamido)ethyl(2-(5-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-8-yl)ethyl)carbamate [Examples 81-175, step f] (6.6 g), completing the transfer with more NMP (30 mL). The resulting solution was stirred at room temperature for 4 hours and then cooled in an ice-water bath and treated with sodium triacetoxyborohydride (3.3 g) in one portion. The resulting suspension was stirred at room temperature overnight, then more sodium borohydride (2.2 g) was added and the mixture was stirred for a further 5 hours. The mixture was cautiously poured into saturated sodium bicarbonate solution and extracted twice with ethyl acetate. The combined organic phases were washed three times with water, once with brine, then dried (MgSO4), filtered and concentrated onto flash silica (100 mL) in-vacuo. The resulting powder was purified by flash chromatography on silica eluted with acetic acid:methanol:dichloromethane (1:5:94) to elute off the benzyl alcohol corresponding to reduced starting material, 100% dichloromethane to wash the column free from acetic acid, then triethylamine:methanol:dichloromethane (1:5:94) to elute off the product. Fractions containing the desired product were combined and concentrated in-vacuo to afford the subtitled compound as an off-white foam. Yield 4.6 g.

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