Reagents
and conditions: (i)
DPPA, DBU, dioxane, then TBAI, 15-crown-5, NaN3, reflux,
88%; (ii) Br2, NaOAc buffer (1M, pH 3.9), rt, 24 h, 99%;
(iii) propargyl chloride, NaH, TBAI, DMF, rt, 16 h, 72%; (iv) CuSO4·5H2O, sodium ascorbate, tBuOH-H2O, rt, 16 h, 71%; (v) Na2Cl4Pd, PhB(OH)2, TPPTS, Na2CO3, MeCN–H2O, 80 °C, 1 h, 21%; (vi) 0.1 M H2SO4, 80 °C, 24%.