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Reagents and conditions: (a) for β-34a,b: propargyl alcohol, (EtO)3P·CuI, 1:1 toluene/THF, 24 h, reflux; for α-35a: propargyl alcohol, CuSO4 (0.2 eq.), sodium ascorbate (0.4 eq.), THF, H2O, 20–25 min, reflux; for α-35b: propargyl alcohol, CuSO4 (0.2 eq.), sodium ascorbate (0.4 eq.), t-BuOH, H2O, 20 h, 50 °C; (b) 40, DCI, MeCN, 45 min, r. t. (c) t-BuOOH, decane, MeCN, 45 min, r.t.; then Et2NH, MeCN, 45 min, r.t.; (d) NH4OH, MeCN, 18 h, r.t. DCI: 4,5-dicyanoimidazole.
