Reaction Steps
tert-butyl 1-oxo-1-phenylpropan-2-ylcarbamate (40) (1.3 g, 5.0 mmol, 1.0 equiv.) was added to a 100 mL RBF followed by EtOH (39 mL). Next, a 37% solution of formaldehyde (8.1 mL, 100 mmol, 20.0 equiv.) was added to the reaction mixture and the solution heated to 35° C. Finally, a 0.5 M solution of K2CO3 (350 mg, 2.5 mmol, 5.0 mL dH2O, 0.5 equiv.) was added to the reaction flask and the solution stirred vigorously for 24 h. The solution was neutralized with 1% HCl, transferred to a separatory funnel with a 1.7 M solution of NaCl (5.0 g, 85.0 mmol, 50 mL H2O), and extracted with CH2Cl2 (5×50 mL). The organic layers were combined and dried over Na2SO4. The resulting solution was concentrated on a rotary evaporator and dried under vacuum to give a crude oil. The residue was purified by flash column chromatography (30% EtOAc/Hexanes) to give 1.1 g (79%) of 41 as a colorless oil. Rf=0.29 (50% EtOAc/Hexanes); IR (film) 3352, 2977, 1684, 1367, 1166 cm−1; 1H NMR (500 MHz, CDCl3) δ Major Rotamer: 8.00 (br s, 2H, Ph-H), 7.42 (br s, 3H, Ph-H), 5.87 (br s, 1H, carbamate-NH), 5.49 (br s, 1H, Boc-NH—CH), 4.12 (m, 2H, C—CH2), 3.76 (m, 2H, C—CH2), 3.32 (br s, 2H, CH2—OH), 1.63 (s, 3H, C—CH3), 1.26 (s, 9H, t-butyl-CH3). Minor Rotamer: 8.15 (br s, 2H, Ph-H), 7.51 (br s, 3H, Ph-H), 5.82 (br s, 1H, carbamate-NH), 3.09 (br s, 2H, CH2—OH), 1.09 (s, 9H, t-butyl-CH3); 13C NMR (125 MHz, CDCl3) Major Rotamer: δ 202.8, 155.1, 132.9, 128.5, 128.3, 80.5, 67.9, 64.4, 28.2, 21.6; LRMS (ESI-MS m/z): Mass calcd for C15H21NNaO4 [M+Na]+, 302.32. Found 302.
