Phthalimide → Benzyl [(2S)-3-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)butan-2-yl]carbamate

Participants

Reaction Steps

Under argon, 0.72 g of benzyl [(2S)-3-hydroxybutan-2-yl]carbamate (Example 133A, 3.3 mmol, 1 equivalent), 0.57 g of 1H-isoindole-1,3(2H)-dione (3.9 mmol, 1.2 equivalents) and 1.3 g of triphenylphosphine (4.9 mmol, 1.5 equivalents) were dissolved in 15 ml of THF, and 1.1 g of di-tert-butyl(E)-diazene-1,2-dicarboxylate (DIAD, 4.9 mmol, 1.5 equivalents) were added at RT. The mixture was stirred at RT overnight, 2 drops of water and Extrelut® were added and the mixture was concentrated. The residue was purified on a silica gel cartridge (Biotage SNAP Cartridge KP-Sil 25 g) (gradient cyclohexane/ethyl acetate from 5% to 100%). The crude product obtained was left in a mixture of 5 ml of methanol and 1 ml of water overnight. The solid obtained was filtered off, washed with a little methanol/water mixture and dried under reduced pressure. The filtrate was purified by preparative HPLC (Method 9). This gave a total of 692 mg (53% of theory, purity 87%) of the title compound (diastereomer mixture in a ratio of about 4:1).

Provenance & Evidence