Concise asymmetric syntheses of novel phenanthroquinolizidines

The first preparation of enantioenriched phenanthroquinolizidines with a quaternary center at C14a was accomplished in seven steps from readily available starting materials. Key steps were an efficient dynamic kinetic allylation of a diastereomeric mixture of chiral tert-butylsulfinyl ketimines and the construction of a piperidine E ring by rhodium catalyzed hydroformylation. The Stevens rearrangement of the corresponding N-benzyl derivatives took place smoothly, allowing the installation of a benzyl moiety at C9 in a trans relationship with the methyl group. The cytoxicity of the prepared phenanthroquinolizidines was evaluated against different human cancer cell lines.We thank the Spanish Ministerio de Ciencia e Innovación (CTQ2011-24165) and the University of Alicante (VIGROB-173) for financial support. C. A.-T. thanks the ISO for a grant

Syntheses and Cytotoxicity of (R)- and (S)-7-Methoxycryptopleurine

Two efficient protocols are described for the transformation of a key chiral homoallyllic sulfinamine intermediate in four steps into enantioenriched 7-methoxycryptopleurine. While one of the protocols relied on a rhodium catalyzed linear hydroformylation process, the alternative approach was based on a ring-closing metathesis from the corresponding N-allyl-sulfinamine. The cytotoxic evaluation of both enantiomers of the target compound demonstrated that the (R)-compound is much more potent than its antipode against the four cancer cell lines examined.We thank the Spanish Ministerio de Ciencia e Innovación (CTQ2011-24165) for financial support. I.B. acknowledges the Generalitat Valenciana for a postdoctoral fellowship (ACIF/2011/159). C.A.-T. thanks the ISO for a grant

Cryptopleurine Targets NF-κB Pathway, Leading to Inhibition of Gene Products Associated with Cell Survival, Proliferation, Invasion, and Angiogenesis

Cryptopleurine, a phenanthroquinolizidine alkaloid, was known to exhibit anticancer activity; however, the underlying mechanism is poorly understood. Because the nuclear factor-κB (NF-κB) transcription factors control many physiological processes including inflammation, immunity, and development and progression of cancer, we investigated the effects of cryptopleurine on tumor necrosis factor alpha (TNF-α)-induced NF-κB activation pathway and on the expression of NF-κB-regulated gene products associated with many pathophysiological processes.MDA-MB231, MDA-MB435, MCF-7, HEK293, RAW264.7 and Hep3B cells were used to examine cryptopleurine's effect on the NF-κB activation pathway. Major assays were promoter-reporter gene assay, electrophoretic mobility shift assay (EMSA), in vitro immune complex kinase assay, real-time PCR, Western blot analysis, and Matrigel invasion assay. Experiments documenting cell proliferation and apoptosis were analyzed by MTT method and flow cytometry, respectively. The results indicated that cryptopleurine suppressed the NF-κB activation through the inhibition of IκB kinase (IKK) activation, thereby blocking the phosphorylation and degradation of the inhibitor of NF-κB alpha (IκBα) and the nuclear translocation and DNA-binding activity of p65. The suppression of NF-κB by cryptopleurine led to the down-regulation of gene products involved in inflammation, cell survival, proliferation, invasion, and angiogenesis.Our results show that cryptopleurine inhibited NF-κB activation pathway, which leads to inhibition of inflammation, proliferation, and invasion, as well as potentiation of apoptosis. Our findings provide a new insight into the molecular mechanisms and a potential application of cryptopleurine for inflammatory diseases as well as certain cancers associated with abnormal NF-κB activation

Design, Synthesis, and Biological Studies of New Phenanthroindolizidine

The overall goals of this research were to design and synthesize novel phenanthroindolizidine and phenanthroquinolizidine analogs, study corresponding structure-activity relationships, and explore their potential mechanisms of action as a new class of anticancer agents. A new series of phenanthrene-based tylophorine analogs was designed and synthesized, among which compounds 13, 19, 21, and 22 were found to have comparable or higher in vitro anticancer activity than previously reported analog PBT-1. Mechanistic studies suggested that these new analogs, like PBT-1, inhibit cancer cell growth through the inhibition of Akt phosphorylation and NF-[kappa]B signaling pathways. In view of the scarcity of SAR research for this class of natural products, a new synthetic strategy was designed and established. An important characteristic of this method was preparation of the key intermediate 44 that can be used to generate a versatile pool of molecules possessing interesting anticancer profiles. The new methodology opened up an avenue to study SAR on the E-ring of these natural alkaloids. Compound 50c with a 7-membered E-ring was synthesized for the first time and displayed greatly improved selectivity against A549 and HCT-8 cancer cell lines, suggesting a potential role of the E-ring size in determining potency. Based on the new synthetic approach, new derivatives with an opened E-ring or a heteroatom (N or O) incorporated in the E-ring were obtained. These new analogs still exhibited strong anticancer potency, and among them, compound 110 showed significant anticancer activity (average IC50's around 20 nM) comparable with R-cryptopleurine. Compound 110 also exhibited improved cell-line selectivity, as well as increased polarity as predicted by BBB penetration ratio, which could potentially lead to reduced CNS toxicity. An in vivo study suggested that this compound had significant tumor growth inhibition against HT-29 human colorectal adenocarcinoma. This improved synthetic methodology also allwed direct introduction of polar groups, such as hydroxyl and amino, at different positions in the E-ring of antofine and cryptopleurine. These proposed new derivatives should provide potentially useful information for SAR investigation and, most importantly, development of promising clinical trial candidate compounds

Targeting a ribonucleoprotein complex containing the caprin-1 protein and the c-Myc mRNA suppresses tumor growth in mice: an identification of a novel oncotarget

Tylophorine compounds have been the focus of drug development for decades. Tylophorine derivatives exhibit anti-cancer activities but their cellular targets remain unknown. We used a biotinylated tylophorine derivative to probe for the interacting cellular target(s) of tylophorine. Tylophorine directly binds to caprin-1 and consequently enhances the recruitment of G3BP1, c-Myc mRNA, and cyclin D2 mRNA to form a ribonucleoprotein complex. Subsequently, this tylophorine targeted ribonucleoprotein complex is sequestered to the polysomal fractions and the protein expressions of the associated mRNA-transcripts are repressed. Caprin-1 depleted carcinoma cells become more resistant to tylophorine, associated with decreased formation of the ribonucleoprotein complex targeted by tylophorine. Consequently, tylophorine downregulates c-Myc and cyclins D1/D2, causing hypophosphorylation of Rb and suppression of both processing-body formation and the Warburg effect. Gene expression profiling and gain-of-c-Myc-function experiments also revealed that the downregulated c-Myc contributes to the anti-oncogenic effects of tylophorine compounds. Furthermore, the potent tylophorine derivative dibenzoquinoline-33b elicited a similar effect, as c-Myc protein levels were also decreased in xenograft tumors treated with dibenzoquinoline-33b. Thus, tylophorine compounds exert anti-cancer activity predominantly by targeting and sequestering the caprin-1 protein and c-Myc mRNA associated ribonucleoprotein complex

Antitumor Agents. 274. A New Synthetic Strategy for E-Ring SAR Study of Antofine and Cryptopleurine Analogues

A new versatile synthetic methodology for the synthesis of enantiomerically pure natural phenanthroindolizidines and phenanthroquinolizidines has been established and described. Natural products R-antofine and R-cryptopleurine, as well as a novel E-ring expanded analog 13c (E7), 12-oxo-S-antofine (17), and 12N-methyl-12-aza-S-antofine (18) were synthesized with the new method. This strategy will greatly facilitate future SAR studies on the natural alkaloids with E-ring variations

Carbopalladation/Suzuki Coupling Cascade for the Generation of Quaternary Centers. Access to Pyrrolo[1,2-b]isoquinolines

A convergent route to pyrrolo[1,2-b]isoquinolines with a quaternary center at C-10 has been developed, that implies a sequential Pd(0)-catalyzed carbopalladation followed by cross-coupling reaction with boronic acids. The adequate catalytic system and experimental conditions, with and without the use of phosphane ligands, have been selected to control the chemoselectivity of the process, allowing a 6-exo-carbopalladation to generate a quaternary center, and avoiding a direct Suzuki coupling. A variety of electron rich and electron deficient arylboronic acids can be used providing an efficient route to substituted pyrrolo[1,2-b]isoquinolines in moderate to good yields (up to 94%, 22 examples).Ministerio de Economía y Competitividad (CTQ2016-74881-P) // Gobierno Vasco (IT1045-16

Alkaloids: Therapeutic Potential against Human Coronaviruses

Alkaloids are a class of natural products known to have wide pharmacological activity and have great potential for the development of new drugs to treat a wide array of pathologies. Some alkaloids have antiviral activity and/or have been used as prototypes in the development of synthetic antiviral drugs. In this study, eleven anti-coronavirus alkaloids were identified from the scientific literature and their potential therapeutic value against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is discussed. In this study, in silico studies showed an affinity of the alkaloids for binding to the receptor-binding domain of the SARS-CoV-2 spike protein, putatively preventing it from binding to the host cell. Lastly, several mechanisms for the known anti-coronavirus activity of alkaloids were discussed, showing that the alkaloids are interesting compounds with potential use as bioactive agents against SARS-CoV-2

DCB-3503, a Tylophorine Analog, Inhibits Protein Synthesis through a Novel Mechanism

BACKGROUND: DCB-3503, a tylophorine analog, inhibits the growth of PANC-1 (human pancreatic ductal cancer cell line) and HepG2 (human hepatocellular cancer cell line) tumor xenografts in nude mice. The inhibition of growth leads to cancer cell differentiation instead of cell death. However, the mechanisms of action of tylophorine analogs is unknown. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we show that DCB-3503 suppresses the expression of pro-oncogenic or pro-survival proteins with short half-lives, including cyclin D1, survivin, beta-catenin, p53, and p21, without decreasing their mRNA levels. Proteasome inhibitor reversed the inhibitory effect of DCB-3503 on expression of these proteins. DCB-3503 inhibited the incorporation of radiolabeled amino acid and thymidine, and to a much lesser degree of uridine, in a panel of cell lines. The mechanism of inhibition of protein synthesis is different from that of cycloheximide (CHX) as assayed in cell culture and HeLa in vitro translation system. Furthermore, in contrast to rapamycin, DCB-3503 does not affect protein synthesis through the mTOR pathway. DCB-3503 treatment shifts the sedimentation profiles of ribosomes and mRNAs towards the polysomal fractions while diminishing monosome abundance, indicative of the inhibition of the elongation step of protein synthesis. Preferential down regulation of several studied proteins under these conditions is likely due to the relative short half-lives of these proteins. CONCLUSION/SIGNIFICANCE: The inhibitory effect of DCB-3503 on translation is apparently distinct from any of the current anticancer compounds targeting protein synthesis. Translation inhibitors with novel mechanism could complement current chemotherapeutic agents for the treatment of human cancers and suppress the occurrence of drug resistance