[O:1]=[C:2]1[CH2:5][CH:4]([NH:6][C:7](=[O:13])[O:8][C:9]([CH3:12])([CH3:11])[CH3:10])[CH2:3]1.C1COCC1.[BH4-].[Li+].[Cl-].[NH4+]>CCOC(C)=O.CCCCCC.O.CCOC(C)=O>[C:9]([O:8][C:7](=[O:13])[NH:6][C@H:4]1[CH2:5][C@@H:2]([OH:1])[CH2:3]1)([CH3:12])([CH3:10])[CH3:11]
tert-Butyl (3-oxocyclobutyl)carbamate (43.2 g, 233 mmol) was charged into a 2 L 3-necked flask equipped with a thermometer and an addition funnel. THF (0.7 L) was added and the mixture was cooled to −73° C. internal temperature. Lithium borohydride, 2M in THF (140 mL, 280 mmol) was added over 30 minutes via the addition funnel, during which time the temperature did not exceed −72° C. After stirring for an additional 1 h at that temperature, TLC analysis indicated reaction was complete. Saturated aqueous ammonium chloride (0.3 L) was added and the mixture was warmed to 0° C. After gas evolution ceased, EtOAc (0.3 L) and water (0.3 L) were added and the mixture was stirred vigorously for 1 h. The layers were then separated and the aqueous layer was extracted with EtOAc (1×). The combined extracts were dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo to give a yellow solid. This solid was suspended in 3:1 EtOAc/hexane and heated to boiling. The remaining solid was filtered off and additional hexane (100 mL) was added to the filtrate. The filtrate was then cooled in the freezer overnight. The resulting solid was collected by filtration and washed with cold 1:1 EtOAc/hexane solution, then dried to give tert-butyl(cis-3-hydroxycyclobutyl)carbamate (25.8 g, 59.0% yield) as a white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 1.36 (s, 9 H) 1.68 (qd, J=8.54, 2.93 Hz, 2 H) 2.33-2.45 (m, 2 H) 3.34-3.44 (m, 1 H) 3.65-3.76 (m, 1 H) 4.98 (d, J=5.67 Hz, 1 H) 7.03 (d, J=7.82 Hz, 1 H).
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