Concise synthesis and in vitro anticancer activity of benzo[g][1]benzopyrano[4,3-b]indol-6(13H)-ones (BBPIs), topoisomerase I inhibitors based on the marine alkaloid lamellarin.

Benzo[g][1]benzopyrano[4,3-b]indol-6(13H)-ones (BBPIs) are potent anticancer compounds having unique BBPIs ring system designed on the basis of the marine natural product lamellarin D. In this study, we describe an alternative synthesis of a 2-demethoxy series of BBPIs, employing van Leusen pyrrole synthesis and an intramolecular Heck reaction as the key reactions. Cytotoxicity of the derivatives against several cancer and normal cell lines is reported.

Synthesis and evaluation of azalamellarin N and its A-ring-modified analogues as non-covalent inhibitors of the EGFR T790M/L858R mutant.

Azalamellarin N, a synthetic lactam congener of the marine natural product lamellarin N, and its A-ring-modified analogues were synthesized and evaluated as potent and non-covalent inhibitors of the drug-resistant epidermal growth factor receptor T790M/L858R mutant. An in vitro tyrosine kinase assay indicated that the inhibitory activities of the synthetic azalamellarin analogues were higher than those of the corresponding lamellarins. The azalamellarin analogue bearing two 3-(dimethylamino)propoxy groups at C20- and C21-positions exhibited the highest activity and selectivity against the mutant kinase [IC (T790M/L858R) = 1.

Lamellarin 14, a derivative of marine alkaloids, inhibits the T790M/C797S mutant epidermal growth factor receptor.

The emergence of acquired resistance is a major concern associated with molecularly targeted kinase inhibitors. The C797S mutation in the epidermal growth factor receptor (EGFR) confers resistance to osimertinib, a third-generation EGFR-tyrosine kinase inhibitor (EGFR-TKI). We report that the derivatization of the marine alkaloid topoisomerase inhibitor lamellarin N provides a structurally new class of EGFR-TKIs.

Lamellarin alkaloids: Isolation, synthesis, and biological activity.

Lamellarins are marine alkaloids containing fused 14-phenyl-6H-[1]benzopyrano[4',3':4,5]pyrrolo[2,1-a]isoquinoline or non-fused 3,4-diarylpyrrole-2-carboxylate ring systems. To date, more than 50 lamellarins have been isolated from a variety of marine organisms, such as mollusks, tunicates, and sponges. Many of them, especially fused type I lamellarins, exhibit impressive biological activity, such as potent cytotoxicity, topoisomerase I inhibition, protein kinases inhibition, and anti-HIV-1 activity.

Lamellarin-inspired potent topoisomerase I inhibitors with the unprecedented benzo[g][1]benzopyrano[4,3-b]indol-6(13H)-one scaffold.

A new class of topoisomerase I inhibitors containing the unprecedented benzo[g][1]benzopyrano[4,3-b]indol-6(13H)-one (abbreviated as BBPI) ring system have been developed based on structure-activity relationship studies of the cytotoxic marine alkaloid lamellarin D. The pentacyclic BBPI scaffold was constructed from N-tert-butoxycarbonylpyrrole by sequential and regioselective functionalization of the pyrrole core using directed lithiation, conventional electrophilic substitution, and palladium-catalyzed cross-coupling reactions. Further N-alkylation of the scaffold followed by selective deprotection of the O-isopropyl group produced a range of N-substituted BBPI derivatives.

Design, synthesis, and evaluation of A-ring-modified lamellarin N analogues as noncovalent inhibitors of the EGFR T790M/L858R mutant.

A series of A-ring-modified lamellarin N analogues were designed, synthesized, and evaluated as potential noncovalent inhibitors of the EGFR T790M/L858R mutant, a causal factor in the drug-resistant non-small cell lung cancer. Several water-soluble ammonium- or guanidinium-tethered analogues exhibited good kinase inhibitory activities. The most promising analogue, 14f, displayed an excellent inhibitory profile against the T790M/L858R mutant [IC (WT) = 31.

Modular synthesis of lamellarins via regioselective assembly of 3,4,5-differentially arylated pyrrole-2-carboxylates.

A modular synthesis of lamellarins via 3,4,5-differentially arylated pyrrole-2-carboxylate intermediates has been developed. The key reactions employed are Br-Li exchange-methoxycarbonylation of 2,5-dibromo-1-(tert-butoxycarbonyl)-1H-pyrrole (1) followed by palladium-catalyzed iterative Suzuki-Miyaura coupling of the pyrrole core. The 3,4,5-triarylpyrrole 4 thus synthesized was readily converted to 5,6-saturated lamellarin L (2) and 5,6-unsaturated lamellarin N (3) via lactonization followed by annulation of the pyrrole nitrogen and lateral aromatic ring at C5 using 2-bromoethyl phenyl sulfide or bromoacetaldehyde dimethyl acetal as two-carbon homologation agents.

Synthesis, resolution, and biological evaluation of atropisomeric (aR)- and (aS)-16-methyllamellarins N: unique effects of the axial chirality on the selectivity of protein kinases inhibition.

The total synthesis of the optically active (aR)- and (aS)-16-methyllamellarins N (3a and 3b) was achieved via resolution on HPLC chiral stationary phase. The kinase inhibitory activities of both enantiomers were evaluated on eight protein kinases relevant to cancer and neurodegenerative diseases (CDK1/cyclin B, CDK2/cyclin A, CDK5/p25, GSK-3α/β, PIM1, DYRK1A, CLK3, and CK1). Isomer (aR)-3b exhibited potent but nonselective inhibition on all protein kinases except CK1, while (aS)-3a selectively inhibited only GSK-3α/β, PIM1, and DYRK1A.

Synthesis, structure-activity relationships, and mechanism of action of anti-HIV-1 lamellarin α 20-sulfate analogues.

Lamellarin α and six different types of lamellarin α 20-sulfate analogues were synthesized and their structure-activity relationships were investigated using a single round HIV-1 vector infection assay. All lamellarin sulfates having pentacyclic lamellarin core exhibited anti-HIV-1 activity at a 10 μM concentration range regardless of the number and position of the sulfate group. On the other hand, non-sulfated lamellarin α and ring-opened lamellarin sulfate analogues did not affect HIV-1 vector infection in similar concentrations.

Infection of XC cells by MLVs and Ebola virus is endosome-dependent but acidification-independent.

Inhibitors of endosome acidification or cathepsin proteases attenuated infections mediated by envelope proteins of xenotropic murine leukemia virus-related virus (XMRV) and Ebola virus, as well as ecotropic, amphotropic, polytropic, and xenotropic murine leukemia viruses (MLVs), indicating that infections by these viruses occur through acidic endosomes and require cathepsin proteases in the susceptible cells such as TE671 cells. However, as previously shown, the endosome acidification inhibitors did not inhibit these viral infections in XC cells. It is generally accepted that the ecotropic MLV infection in XC cells occurs at the plasma membrane.

Directed lithiation of N-benzenesulfonyl-3-bromopyrrole. electrophile-controlled regioselective functionalization via dynamic equilibrium between C-2 and C-5 lithio species.

Directed lithiation of N-benzenesulfonyl-3-bromopyrrole (1) with LDA in THF at -78 degrees C generated C-2 lithio species 3 selectively. Reactions of 3 with reactive electrophiles produced the corresponding 2-functionalized pyrroles 4. On the other hand, quenching with less reactive electrophiles generated the corresponding 5-substituted pyrroles 5.

Design and synthesis of lamellarin D analogues targeting topoisomerase I.

A general synthetic route to rationally designed lamellarin D analogues, 1-dearyllamellarin D (1) and 1-substituted 1-dearyllamellarin D (2), has been developed. The key pentacyclic intermediate 22 was prepared by palladium-catalyzed direct arylation of 12, which in turn was synthesized via C-2-selective lithiation of 15 followed by palladium-catalyzed cross-coupling as the key reactions. Compound 22 was converted to a wide range of C-1-substituted analogues 2 via regioselective electrophilic substitution and palladium-catalyzed cross-coupling reactions.

Synthetic approach to telomerase inhibitor dictyodendrin B: synthesis of the pyrrolo[2,3-c]carbazole core.

The core structure of the telomerase inhibitor, dictyodendrin B, was synthesized by using the palladium-catalyzed cross-coupling reaction of 3-aryl-1-(2-arylethyl)-4-hydroxy-2,5-bismethoxycarbonylpyrrole triflate with 7-alkoxyindole-3-boronate as the key step.

Anticancer alkaloid lamellarins inhibit protein kinases.

Lamellarins, a family of hexacyclic pyrrole alkaloids originally isolated from marine invertebrates, display promising anti-tumor activity. They induce apoptotic cell death through multi-target mechanisms, including inhibition of topoisomerase I, interaction with DNA and direct effects on mitochondria. We here report that lamellarins inhibit several protein kinases relevant to cancer such as cyclin-dependent kinases, dual-specificity tyrosine phosphorylation activated kinase 1A, casein kinase 1, glycogen synthase kinase-3 and PIM-1.

Molecular determinants of topoisomerase I poisoning by lamellarins: comparison with camptothecin and structure-activity relationships.

A series of lamellarin derivatives have been studied as topoisomerase I (Top1) inhibitors. Molecular models of the ternary complexes formed between the DNA-Top1 ensemble and lamellarin D (LMD) or camptothecin (CPT) fully intercalated into the duplex DNA have been built and studied by means of nanosecond molecular dynamics simulations in aqueous solution. Our results show that the 20-OH and 8-OH of LMD can participate in hydrogen-bonding interactions with the side chains of Glu356 and Asn722, respectively, the latter being consistent with the finding that CEM/C2 cells, which are resistant to CPT, are cross-resistant to LMD.

Synthesis and structure-activity relationship study of lamellarin derivatives.

Ten derivatives (3-12) of marine alkaloid lamellarin D (1) were synthesized and evaluated for cytotoxicity against a HeLa cell line in an effort to examine their structure-activity relationships. It appeared that the hydroxyl groups at positions C-8 and C-20 of 1 were important structural requirements for cytotoxic activity, while the hydroxyl group at C-14 and the two methoxy groups at C-13 and C-21 were not necessary for the activity.