Concentrated sufuric acid (13 ml) is added dropwise to a stirred slurry of the compound of Example 11 (13 mmol) and sodium azide (52 mmol) in chloroform at -20° C. The reaction mixture is allowed to warm to ambient temperature and then heated at reflux temperature for 36 hr. The reaction mixture is then cooled to 0° C. and water (100 ml) added. The mixture is carefully basified with 50% sodium hydroxide solution. The chloroform layer is separated and the aqueous layer is extracted with methylene chloride. The combined organic layers are dried and concentratedto obtain the product which is purified by standard procedures.
