A stirred solution containing 4-amino-4-methylpentanoic acid (0.90 g, 6.86 mmol, Chembridge), Na2CO3 (2.9 g, 27. mmol), and 1,4-dioxane (10 mL) was cooled in an ice bath and Fmoc-Cl (2.1 mg, 8.2 mmol) dissolved in 1,4-dioxane (10 mL) was added in over about 2 min. The mixture was stirred at about 0° C. for about 1 h and then allowed to warm to rt. The mixture was neutralized with aqueous 6 N HCl and extracted with EtOAc (3×25 mL). The combined organic layers were dried over MgSO4, filtered and concentrated under reduced pressure. The crude material was purified by flash chromatograph (40 g silica gel column, 10-60% EtOAc/Heptane) to give 4-(((9H-fluoren-9-yl)methoxy)carbonylamino)-4-methylpentanoic acid the title compound (1.2 g, 49%): LC/MS (Table 2, Method b) Rt=2.31 min.; MS m/z: 352 (M−H)+.
