Scheme 10.
Reagents and conditions (a) MOMCl, NaH, Et2O/DMF, 0 °C to rt (96%); (b) n-BuLi, B(OMe)3, THF then AcOH, H2O2, 0 °C to rt (95%); (c) LiCl, MS 3A, HFIP/toluene, ethyl glyoxalate, rt (97%); (d) 4-nitrophenyltriflate, K2CO3, DMF, rt (94%); (e) trimethyl boroxine, K3PO4, Pd(PPh3)4, 1,4-dioxane, reflux (93%); (f) SOBr2, benzotriazole, CH2Cl2, rt (91%).