3.19 g (9.63 mmol) of carbon tetrabromide were added to a solution of 2.57 g (6.40 mmol) of N-(2-t-butyl-5-hydroxymethylphenyl)-2-(9H-xanthen-9-yl)acetamide (prepared as described in Preparation 14) and 2.04 g (7.77 mmol) of triphenylphosphine in 20 ml of methylene chloride, and the resulting mixture was stirred for 4 hours at room temperature. At the end of this time, the reaction mixture was placed on a column containing 100 g of silica gel and the column was eluted with a 1:9 by volume mixture of diethyl ether and methylene chloride. The eluates were combined and concentrated by evaporation under reduced pressure, to give 2.52 g (yield 85%) of the title bromide as crystals, melting at 229°-231° C. (after recrystallization from ethyl acetate).
