The product from Example 23, as the free base (0.330 g, 1 mmol) and triethylamine (0.15 mL, 1.05 mmol) were stirred in 10.0 mL tetrahydrofuran and cooled briefly in an ice bath. To the mixture was added dropwise valeryl chloride (0.12 mL, 1 mmol) and the resulting mixture was stirred 18 h at room temperature and filtered, and the filtrate was evaporated to 0.385 g oil. Crystallization from diethyl ether provided 0.176 g colorless crystals. Mp 107°-109° C. Mass spectrum, m+ =413. Anal (C23H35N5O2) theory C, 66.80; H, 8.53; N, 16.93; found C, 66.59; H, 8.66; N, 17.04.
