aReagents and conditions: (i) sodium azide, ammonium chloride, methanol/water (91%); (ii) tert-butyl propiolate, N,N-diisopropylethylamine, acetic acid, dichloromethane (82% crude); (iii) diethylaminosulfur trifluoride, pyridine, dichloromethane (45%); (iv) 10% palladium hydroxide on carbon, hydrogen, ethyl acetate (101% crude); (v) 4-toluenesulfonyl chloride, 4-dimethylaminopyridine, dichloromethane (84% crude); sodium iodide, acetone (91%).