Figure 1.
A. The synthesis scheme of Sali-ABA and Sali-ABA-MPBH. B. An ESI-MS spectrum of a purified reaction product between ABA and Sali. Several major molecular ion peaks are labelled. C. An ESI-MS spectrum of purified reaction product between Sali-ABA and MPBH. The insert is the expected chemical structure of the Sali-ABA-MPBH conjugate. The peak that matches the MW of Sali-ABA-MPBH is evident. The presence of peaks of MPBH and Sali-ABA of this purified conjugate suggests that the hydrazone bond inside the conjugate is not stable under the ESI-MS experimental conditions.