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UBC Theses and Dissertations

Bioactive marine natural products : analogue synthesis, SAR, and target identification Yan, Luping


3,6,7-trihydroxycoumarin C11 (2.14) was first isolated from the green alga Dasycladus vermicularis in 1983. C11 and 3,7,8-trihydroxycoumarin C21 (2.15), alongside their precursors C12 (2.18) and C22 (2.20), were synthesized for a target-based screen for anti-HCV drugs, where ideal hits eliminate fluorescence signals by inhibiting the proteolytic activity of HCV NS3pro/Pep4A against a synthetic peptide “BS-IQFS”. With C12 and C22 serving as negative controls, C11 and C21 inhibited the NS3pro/Pep4A activity in vitro. The IC₅₀’s of C11 and C21 were 3.07 μM and 2.10 μM, respectively. A bioassay-guided fractionation identified sintokamides A – E (3.11 – 3.15) from extracts of the sponge Dysidea sp. in 2008. In a phenotypic screen, the chlorinated dipeptides showed strong to modest inhibition of luciferase activity caused by AR NTD transactivation in LNCaP cells. Larger quantities of sintokamides A and B were isolated from the sponge for further biological study. After developing a practical synthetic route, a comprehensive SAR of the sintokamides was available from the in vitro activities of 29 synthetic analogues/precursors based on a 1,17-dinorsintokamide skeleton. LPY26 [(4R,10R)-3.233] showed the best biological activity in the synthetic analogues prepared to date and it was selected as a drug lead. Mechanism of action study using synthetic probes LPY30 (4.7) and LPY31 (4.8) revealed that the hexachlorinated 1,17-dinorsintokamides covalently bound to the AR, but not to the same AF1 region in the AR NTD as EPI-001 (3.8). The structure of latonduine A (5.1) isolated from the sponge Stylissa carteri and its total synthesis were published in 2003. Later, latonduine A was shown to be active in a phenotypic screen to find drug leads for the treatment of cystic fibrosis caused by the F508del mutation. Latonduine A could efficiently correct immunofluorescent F508del-CFTR trafficking from the endoplasmic reticulum to the plasma membrane in the engineered cells. Synthetic latonduine A and N-biotinylated latonduine A (5.17) were prepared to support biological studies aimed at identifying its cellular protein target(s). These studies culminated in the finding that latonduine A is an inhibitor of PARP-3 with an EC₅₀ of 400 pM in CFBE41o­- cells.

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