(2S)-5-{[(benzyloxy)carbonyl]amino}-2-{[(tert-butoxy)carbonyl]amino}pentanoic acid → (2S)-5-amino-2-{[(tert-butoxy)carbonyl]amino}pentanoic acid

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Reaction Steps

Boc-Orn-OH (0.51 g) [obtained by catalytically reducing Boc-Orn(Z)-OH in methanol in a stream of hydrogen using 10% Pd-carbon as a catalyst] was dissolved in DMF, and the solution was cooled with ice. TEA (0.61 ml) and PhCOONB [prepared from PhCOOH (0.30 g), HONB (0.47 g) and DCC (0.54 g)] were added thereto, followed by stirring overnight. The reaction solution was concentrated, and the residue was dissolved in AcOEt. The resulting solution was washed with 10% aqueous citric acid. After washing with water, the solution was dried with Na2SO4 and concentrated. Then, ether and dicyclohexylamine (438 μl) were added to the residue to separate out a precipitate, which was collected by filtration.

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