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. Author manuscript; available in PMC: 2021 Oct 8.
Published in final edited form as: Tetrahedron Lett. 2020 Aug 29;61(41):152398. doi: 10.1016/j.tetlet.2020.152398

Fig. 3.

Fig. 3.

(a) Raw-stacked 31P NMR data for the hydrolysis of 6 (11.6 ppm) at pH 5.0 and formation of its hydrolytic product (3.0 ppm), referenced to the external standard (40 mM TPPO, 27 ppm). (b) Compiled and fitted pH-dependent decay data for the area of 6 at pH 7.4 (blue), pH 6.0 (green), pH 5.5 (yellow), pH 5.0 (orange) and pH 4.5 (red) normalized to a 40 mM TPPO standard. For pH 4.5, hydrolysis complete after 2 h. Half-lives calculated based on linearized first-order kinetics model (p < 0.0001 for all pHs except pH 7.4). (c) HPLC studies showing amount of MMAE released after 8 h, using 1 as an internal standard. Studies was carried out in 100 mM buffers (in triplicate) and quenched with 1 N NaOH after 8 h.