[OH:1][C@H:2]([CH3:14])[CH2:3][C:4]1[C:12]2[C:7](=[CH:8][CH:9]=[C:10]([OH:13])[CH:11]=2)[NH:6][N:5]=1.C(=O)([O-])[O-].[K+].[K+].[CH2:21](Br)[C:22]#[CH:23]>C(O)C.O>[CH2:23]([O:13][C:10]1[CH:11]=[C:12]2[C:7](=[CH:8][CH:9]=1)[NH:6][N:5]=[C:4]2[CH2:3][C@H:2]([OH:1])[CH3:14])[C:22]#[CH:21]To a stirred mixture of the product from Step A (1.50 g, 7.81 mmol) in a mixture of ethanol in water (50 mL/10 mL) was added potassium carbonate (1.62 g, 11.7 mmol) and propargyl bromide (80% in toluene, 1.74 g, 1.30 mL, 11.7 mmol). The mixture was heated at 75° C. for 2 hours under nitrogen, evaporated to dryness, mixed with a saturated aqueous solution of sodium bicarbonate (50 mL) and extracted with ethyl acetate. Chromatography on silica (gradient, 25% to 95% ethyl acetate in hexane) gave an oil (1.25 g, 69%): LC/MS (+APCI) m/z 231 (M+H).
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