Reaction Steps
A mixture of ethyl (2S)-2-(tert-butoxy)-2-{4,16,24-trimethyl-11,23-dioxa-1,5,7,8-tetraazapentacyclo[22.2.2.16,9.02,7.013,18]nonacosa-2,4,6(29),8,13(18),14,16-heptaen-3-yl}acetate (30 mg, 0.051 mmol) and NaOH (0.152 mL, 0.152 mmol) in EtOH (2 mL) was refluxed for 2 h. It was then cooled to rt and purified by preparative HPLC to obtain (2S)-2-(tert-butoxy)-2-{4,16,24-trimethyl-11,23-dioxa-1,5,7,8-tetraazapentacyclo[22.2.2.16,9.02,7.013,18]nonacosa-2,4,6(29),8,13(18),14,16-heptaen-3-yl}acetic acid (24 mg, 0.042 mmol, 84% yield) as a white solid. 1H NMR (500 MHz, DMSO-d6) δ 7.25 (d, J=7.3 Hz, 1H), 7.03-6.96 (m, 2H), 6.49 (s, 1H), 5.76 (br. s., 1H), 4.87-4.76 (m, 2H), 4.72 (d, J=12.1 Hz, 1H), 4.58 (d, J=12.1 Hz, 1H), 4.54-4.46 (m, 1H), 3.66-3.58 (m, 2H), 3.39 (m, 1H), 3.12 (br. s., 1H), 2.69-2.60 (m, 2H), 2.55 (br. s., 4H), 2.27 (s, 3H), 1.92-1.50 (m, 8H), 1.18 (s, 3H), 1.15 (s, 9H). LCMS (M+1)=565.4.
