3,4-Dibenzyloxyphenacyl bromide → 2-[1,1-Dimethyl-2-(2-phenylacetamido)ethyl]amino-3',4'-bis(benzyloxy)acetophenone hydrobromide

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A solution of 2-bromo-3',4'-bis(benzyloxy)acetophenone (5.24 g.) and N-(2-amino-2-methylpropyl)-2-phenylacetamide (5.5 g.) in dioxan (25 ml.) was stirred for 2 hours at room temperature. The reaction mixture was diluted with dry ether (200 ml.) and the precipitate of N-(2-amino-2-methylpropyl)-2-phenylacetamide hydrobromide was separated by filtration. The ethereal filtrate was washed with water (3×50 ml.), brine (100 ml.) dried (MgSO4) and then a fresh solution of saturated ethereal hydrogen bromide was added until the solution was just acid. After 18 hours at 0°-5° C. the precipitate which had formed was collected to give 2-[1,1-dimethyl-2-(2-phenylacetamido)ethyl]amino-3',4'-bis(benzyloxy)acetophenone hydrobromide as a solid (6.85 g.) m.p. 155°-160° C. This hydrobromide (5.0 g.) was dissolved in absolute ethanol (300 ml.) and the solution was hydrognated at atmospheric pressure using 10% w/w palladium-on-carbon (3.0 g.) as catalyst. When the uptake of hydrogen was complete (about 3 hours), the catalyst was removed by filtration and the ethanolic filtrate was evaporated at a temperature below 30° C. to give 2-[1,1-dimethyl-2-(2-phenylacetamido)ethyl]amino-3',4'-dihydroxyacetophenone hydrobromide as a foam (3.7 g.) which was used directly for further acylation.

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