Cheilanthane sesterterpenes, protein kinase inhibitors, from a marine sponge of the genus Ircinia

Four cheilanthane sesterterpenoids, 25-hydroxy-13(24), 15, 17-cheilanthatrien- 19,25-olide (1), 13,16-epoxya5-hydroxy- 17-cheilanthen- 19,25-olide (2), 25-hydroxy-13(24), 17-cheilanthadien-16,19-olide (3), and 16,25-dihydroxy-13(24),17-cheilanthadien 19,25-olide (4), were isolated from the marine sponge Ircinia sp. Compounds 1, 3, and 4 are new natural products. The four compounds inhibit MSK1 (mitogen and stress activated kinase) and MAPKAPK-2 (mitogen activated protein kinase activated protein kinase), two protein kinases involved in mitogen and stress signal transduction.