Dicyclohexylcarbodiimide → bis-Boc-L-Ornithyl-D-Homophenylalanine Benzyl ester

Participants

Reaction Conditions

Reaction Steps

D-Homophenylalanine Benzyl ester Tosylate (2.48 g, 5.6 mmol) was suspended in ethyl acetate (25 mL) and a saturated solution of sodium bicarbonate in water was added in portions (25 mL) with stirring at 25° C. The water layer was extracted with ethyl acetate (3×10 mL). The combined organic extract was dried over anhydrous sodium sulfate, filtered and concentrated to dryness to afford D-Homophenylalanine Benzyl ester. The ester was dissolved in acetonitile (25 mL). NaNd-bis-Boc-L-Ornithine (2.0 g, 6.0 mmol) was then added followed by N-hydroxysuccinimide (50 mg) and dicyclohexylcarbodiimide (1.28 g, 6.2 mmol). The reaction was stirred at 25° C. for 30 hr, filtered and the filtrate concentrated to dryness to afford crude product. It was purified by column chromatography on silica gel (hexane:ethyl acetate=3:1), which gave the title product (2.80 g) as white solid.

Provenance & Evidence