General procedure: Potassium hydride (KH, 30% in mineral oil, 4.0 g) was suspended in 50 mL of dimethylformamide (DMF). It was cooled in an ice-water bath, and solid 3H-quinazolin-4-one (4.3 g) was added in. After 30 min, a solution of oxirane 14 (3.5 g) in 10 mL of DMF was added in. The reaction mixture was then heated at 80 C for 8 h under nitrogen atmosphere. It was partitioned between ethyl acetate (75 mL) and water (75 mL), separated organic layer was washed with water (3 × 50 mL), then brine (50 mL), dried over anhydrous sodium sulfate, and evaporated in a rotary evaporator under reduced pressure to furnish the crude product. Silica gel flash chromatography (75% ethyl acetate in hexanes) furnished 15 as off white solid. Yield: 79%.General procedure: Potassium hydride (KH, 30% in mineral oil, 4.0 g) was suspended in 50 mL of dimethylformamide (DMF). It was cooled in an ice-water bath, and solid 3H-quinazolin-4-one (4.3 g) was added in. After 30 min, a solution of oxirane 14 (3.5 g) in 10 mL of DMF was added in. The reaction mixture was then heated at 80 C for 8 h under nitrogen atmosphere. It was partitioned between ethyl acetate (75 mL) and water (75 mL), separated organic layer was washed with water (3 × 50 mL), then brine (50 mL), dried over anhydrous sodium sulfate, and evaporated in a rotary evaporator under reduced pressure to furnish the crude product. Silica gel flash chromatography (75% ethyl acetate in hexanes) furnished 15 as off white solid. Yield: 79%.General procedure: Potassium hydride (KH, 30% in mineral oil, 4.0 g) was suspended in 50 mL of dimethylformamide (DMF). It was cooled in an ice-water bath, and solid 3H-quinazolin-4-one (4.3 g) was added in. After 30 min, a solution of oxirane 14 (3.5 g) in 10 mL of DMF was added in. The reaction mixture was then heated at 80 C for 8 h under nitrogen atmosphere. It was partitioned between ethyl acetate (75 mL) and water (75 mL), separated organic layer was washed with water (3 × 50 mL), then brine (50 mL), dried over anhydrous sodium sulfate, and evaporated in a rotary evaporator under reduced pressure to furnish the crude product. Silica gel flash chromatography (75% ethyl acetate in hexanes) furnished 15 as off white solid. Yield: 79%.General procedure: Potassium hydride (KH, 30% in mineral oil, 4.0 g) was suspended in 50 mL of dimethylformamide (DMF). It was cooled in an ice-water bath, and solid 3H-quinazolin-4-one (4.3 g) was added in. After 30 min, a solution of oxirane 14 (3.5 g) in 10 mL of DMF was added in. The reaction mixture was then heated at 80 C for 8 h under nitrogen atmosphere. It was partitioned between ethyl acetate (75 mL) and water (75 mL), separated organic layer was washed with water (3 × 50 mL), then brine (50 mL), dried over anhydrous sodium sulfate, and evaporated in a rotary evaporator under reduced pressure to furnish the crude product. Silica gel flash chromatography (75% ethyl acetate in hexanes) furnished 15 as off white solid. Yield: 79%.