FIGURE 3.

Identification of N-palmitoyl-l-leucine as an active pre-fraction component. A, MS/MS spectra of an isolated splicing inhibitor. The chemical structure of the deduced active compound N-palmitoyl-l-leucine is shown in the inset. B, NMR spectra for purified active natural product (top) and synthetic compound (bottom). Peak assignments are shown in the inset table. C, UPLC-MS analysis of chiral derivatization of natural product mixture; natural product mixture alone (top), coinjection of natural product mixture with N-palmitoyl-d-leucyl-l-alanine tert-butyl ester (middle), coinjection of natural product mixture with N-palmitoyl-l-leucyl-l-alanine tert-butyl ester (bottom).