L-Isoleucine → N-[2(S)-[t-butoxycarbonylamino]-3-methylpentyl]-isoleucine

Participants

Reaction Steps

Isoleucine (1.31 g, 9.95 mmol) was suspended in anhydrous methanol (10 ml) and trifluoroacetic acid (1.133 g, 0.77 ml, 9.95 mmol) was added. The mixture was stirred until all the isoleucine had dissolved and the solvent was then removed under reduced pressure. Anhydrous DMF (10 ml) was added to the resulting isoleucine trifluoroacetate salt followed by 3 Å molecular sieves and a solution of 2 (1.47 g, 4.9 mmol) in anhydrous DMF (5 ml). After 15 minutes the solution was treated with sodium triacetoxy borohydride (1.58 g, 7.45 mmol) and stirred overnight. The resulting suspension was filtered through celite, diluted with ethyl acetate (50 ml) and washed with saturated sodium chloride solution (2×35 ml). The organic extracts were dried over magnesium sulfate, filtered, and the solvent removed under reduced pressure to yield the acid (1.36 g, 84%) as a yellow oil.

Provenance & Evidence