(4R)-5-Amino-4-[[(9H-fluoren-9-ylmethoxy)carbonyl]amino]-5-oxopentanoic acid

White crystalline powder

Fmoc-D-Glu-OH (59.8 g, 1.0 eq) was dissolved in anhydrous tetrahydrofuran (THF)(324 mL). DCC (40.1 g, 1.2eq) was then added while stirring in ice-water bath. The reaction mixture was allowed to warm to r.t and stirring wasmaintained for additional 8 h to produce 1, 3-dicyclohexylurea (DCU). The precipitates were filtered off, and washed withsmall amount THF. Dry ammonia gas was then bubbled through the reactants while stirring in a NaCl salt-ice bath. Thereaction was completed after 1.5 h when no more white solid was precipitated. Still standing for 30 min, small amountMeOH was added to dissolve the solid. The mixture was cooled in a ice-water bath again. Then 2.0 N HCl was addedcarefully and slowly to adjust pH to 2-3. The solvent was evaporated under vacuum. The resulting solid was dissolvedin AcOEt and then washed with diluted HCl, saturated aqueous NaHCO3 solution, and H2O sequentially. The organiclayer was separated and combined, then dried with MgSO4 overnight, filtered and evaporated under vacuum. Thenresidue was recrystallized with ethyl acetate-cyclohexane system. After filtration, 46.5g target product was obtained witha yield of 78percent. m.p.=204~205°C, [α]=-4.2°(C=10mg/mL, DMF). 1H-NMR(500MHz, DMSO): 7.88(2H, d, J=8.0Hz), 7.72(2H, m), 7.42(2H, m), 7.40(1H, m), 7.40(1H, br.s), 7.32(2H, m, 7.02(1H, br.s), 4.27(2H, m), 4.20(1H, m), 3.93(1H, dd, J=13.5 and 8.5Hz), 2.25(2H, m), 1.89(1H, m), 1.73(1H, m). 13C-NMR(125MHz, DMSO): 173.9, 173.4, 155.9, 143.8, 140.7, 127.6, 127.0, 125.3, 120.0, 65.6, 53.8, 46.6, 30.4, 27.2. ESI-MS: 369.03 [M+H]+, 759.98 [2M+Na]+. HR-MS(TOF): 369.1448 [M+H]+, 759.2623 [2M+Na]+, C20H20N2O5.

Molecular Weight:368.4
XLogP3:1.9
Hydrogen Bond Donor Count:3
Hydrogen Bond Acceptor Count:5
Rotatable Bond Count:8
Exact Mass:368.13722174
Monoisotopic Mass:368.13722174
Topological Polar Surface Area:119
Heavy Atom Count:27
Complexity:545
Undefined Atom Stereocenter Count:1
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes