To a solution of 0.467 g of the product of Example 40 in 5 ml of hexamethylphosphoramide was added 0.163 g of cesium carbonate, 0.304 g of 2-bromoethyl methyl ether, 0.137 g of 45% aqueous potassium hydroxide and 0.017 g of potassium iodide. The suspension was stirred in the dark under argon for 8 days. Ether (40 ml) was added and the mixture was extracted successively with water, brine and water. The ether layer was discarded. The aqueous layers were extracted with chloroform, the chloroform extracts were dried over sodium sulfate and then evaporated, finally at <100° and 0.06 mm. to remove hexamethylphosphoramide. Two recrystallizations of the solid residue from methylene chloride-n-heptane gave 0.424 g of ivory-colored needles, m.p. 138°-141° C. The product was easily soluble in water and in 0.1 M phosphate buffer, pH 7.5.
