PROTEIN-TYROSINE KINASE INHIBITORY PROPERTIES OF PLANAR POLYCYCLICS OBTAINED FROM THE MARINE SPONGE XESTOSPONGIA CF CARBONARIA AND FROM TOTAL SYNTHESIS

Nine related polycyclic quinones and hydroquinones of the halenaquinone class were isolated from two Indo-Pacific collections of the sponge Xestospongia cf. carbonaria. The halenaquinone family appears not to be of polyketide origin but can be biogenetically derived by the union of a sesquiterpene and a quinone. Four new metabolites were characterized including tetrahydrohalenaquinone B (8a), 14-methoxyhalenaquinone (9), xestoquinolide A (10), and xestoquinolide B (11). These were accompanied by five known compounds, halenaquinone (3), halenaquinol (4), halenaquinol sulfate (5), xestoquinone (6), and tetrahydrohalenaquinone A (7a). The new structures were established from 2D NMR data, and the absolute stereochemistry of the chiral centers in 7 and 8 was determined by the formation of 7b and 7c, the bis esters of O-methylmandelic acid. A series of polycyclic models of natural products 3 and 6 were synthesized and included 16-23. The more complex members of this group were assembled via a 4 + 2 cycloaddition between an o-quinodimethane and a functionalized enone. The marine natural products plus two known fungal metabolites, viridin (13) and wortmannin (14), along with halenaquinone synthetic model compounds, were each tested for their ability to inhibit the activity of pp60v-src protein tyrosine kinase (PTK). Halenaquinone and 14-methoxyhalenaquinone were the most potent with IC50 values <10 muM. The other compounds were either less potent or inactive, and a rationalization for this SAR (structure activity relationship) pattern is presented.