Reaction Steps
A mixture of ethyl (2S)-2-(tert-butoxy)-2-{4,23-dimethyl-11,22-dioxa-1,5,7,8-tetraazapentacyclo[21.2.2.16,9.113,17.02,7]nonacosa-2,4,6(29),8,13(28),14,16-heptaen-3-yl}acetate (20 mg, 0.035 mmol) and NaOH (0.035 mL, 0.035 mmol) in EtOH (2 mL) was refluxed for 2 h. It was then cooled to rt, filtered and purified by preparative HPLC to obtain (2S)-2-(tert-butoxy)-2-{4,23-dimethyl-11,22-dioxa-1,5,7,8-tetraazapentacyclo[21.2.2.16,9.113,17.02,7]nonacosa-2,4,6(29),8,13(28),14,16-heptaen-3-yl}acetic acid (17 mg, 0.031 mmol, 89% yield) as a white solid. 1H NMR (500 MHz, DMSO-d6) δ 7.41 (s, 1H), 7.33-7.24 (m, 1H), 7.16 (d, J=7.0 Hz, 2H), 6.51 (s, 1H), 5.64 (s, 1H), 4.50-4.29 (m, 5H), 3.65-3.58 (m, 1H), 3.57-3.38 (m, 3H), 2.76 (d, J=11.4 Hz, 1H), 2.51 (s, 3H), 2.66 (t, J=8.1 Hz, 2H), 1.97 (d, J=13.6 Hz, 1H), 1.89-1.51 (m, 7H), 1.22 (s, 3H), 1.15 (s, 9H). LCMS (M+1)=551.6.
