Inappropriate activity of p90 ribosomal S6 kinase (RSK) has been implicated in various human cancers as well as other pathologies. We previously reported the isolation, characterization, and synthesis of the natural product kaempferol 3-O-(3 ″, 4 ″-di-O-acetyl- α-l-rhamnopyranoside), termed SL0101 [Smith, JA; Poteet-Smith, CE; Xu, Y.; Errington, TM; Hecht, SM; Lannigan, DA Cancer Res., 2005, 65, 1027–1034: Xu, Y.-M; Smith, JA; ...