A Facile Synthesis of 1-Substituted β-Carboline Derivatives via Minisci-Reaction

Photocatalytic Enantioselective Radical Cascade Multicomponent Minisci Reaction of β-Carbolines Using Diazo Compounds as Radical Precursors

Here, a photocatalytic asymmetric multicomponent cascade Minisci reaction of β-carbolines with enamides and diazo compounds is reported, enabling an effective enantioselective radical C─H functionalization of β-carbolines with high yields and enantioselectivity (up to 83% yield and 95% ee). This enantioselective multicomponent Minisci protocol exhibits step economy, high chemo-/enantio-selective control, and good functional group tolerance, allowing access to a variety of valuable chiral β-carbolines. Notably, diazo compounds are suitable radical precursors in enantioselective cascade radical reactions. Moreover, the efficiency and practicality of this approach are demonstrated by the asymmetric synthesis of bioactive compounds and natural products.

Photocatalytic enantioselective Minisci reaction of β-carbolines and application to natural product synthesis

A highly efficient enantioselective direct C-H functionalization of β-carbolines via a Minisci-type radical process under a photo-redox and chiral phosphoric acid cooperative catalytic system has been disclosed. Through this protocol, a wide range of C1 aminoalkylated β-carbolines were constructed directly with high levels of enantioselectivities from readily available β-carbolines and alanine-derived redox-active esters. This transformation allows straightforward access to highly valuable enantioenriched β-carbolines, which are an intriguing structural motif in valuable natural products and synthetic bio-active compounds. This protocol has been utilized as a highly efficient synthetic strategy for the concise asymmetric total synthesis of marine alkaloids eudistomin X, (+)-eudistomidin B and (+)-eudistomidin I.

Innovation in the discovery of the HIV-1 attachment inhibitor temsavir and its phosphonooxymethyl prodrug fostemsavir

The discovery and development of fostemsavir (2), the tromethamine salt of the phosphonooxymethyl prodrug of temsavir (1), encountered significant challenges at many points in the preclinical and clinical development program that, in many cases, stimulated the implementation of innovative solutions in order to enable further progression. In the preclinical program, a range of novel chemistry methodologies were developed during the course of the discovery effort that enabled a thorough examination and definition of the HIV-1 attachment inhibitor (AI) pharmacophore. These discoveries helped to address the challenges associated with realizing a molecule with all of the properties necessary to successfully advance through development and this aspect of the program is the major focus of this retrospective. Although challenges and innovation are not unusual in drug discovery and development programs, the HIV-1 AI program is noteworthy not only because of the serial nature of the challenges encountered along the development path, but also because it resulted in a compound that remains the first and only example of a mechanistically novel class of HIV-1 inhibitor that is proving to be very beneficial for controlling virus levels in highly treatment-experienced HIV-1 infected patients.

Further investigation of harmicines as novel antiplasmodial agents: Synthesis, structure-activity relationship and insight into the mechanism of action

The rise of the resistance of the malaria parasite to the currently approved therapy urges the discovery and development of new efficient agents. Previously we have demonstrated that harmicines, hybrid compounds composed from β-carboline alkaloid harmine and cinnamic acid derivatives, linked via either triazole or amide bond, exert significant antiplasmodial activity. In this paper, we report synthesis, antiplasmodial activity and cytotoxicity of expanded series of novel triazole- and amide-type harmicines. Structure-activity relationship analysis revealed that amide-type harmicines 27, prepared at N-9 of the β-carboline core, exhibit superior potency against both erythrocytic stage of P. falciparum and hepatic stages of P. berghei. Notably, harmicine 27a, m-(trifluoromethyl)cinnamic acid derivative, exhibited the most favourable selectivity index (SI = 1105). Molecular dynamics simulations revealed the ATP binding site of P. falciparum heat shock protein 90 as a druggable binding location, confirmed the usefulness of the harmine's N-9 substitution and identified favourable N-H … π interactions involving Lys45 and the aromatic phenyl unit in the attached cinnamic acid fragment as crucial for the enhanced biological activity. Thus, those compounds were identified as promising and valuable leads for further derivatization in the search of novel, more efficient antiplasmodial agents.

Discovery and preliminary mechanism of 1-carbamoyl β-carbolines as new antifungal candidates

Natural β-carboline alkaloids are ideal models for the discovery of pharmaceutically important entities. Various 1-substituted β-carbolines were synthesized from commercially inexpensive tryptophan and demonstrated significant in vitro antifungal activity against G. graminis. Significantly, compound 4m (EC₅₀ = 0.45 μM) with carboxamide at 1-position displayed the best efficacy and nearly 20 folds enhancement in antifungal potential compared to Silthiopham (EC₅₀ = 8.95 μM). Moreover, compounds 6, 7, and 4i exhibited excellent in vitro antifungal activities and in vivo protective and curative activities against B. cinerea and F. graminearum. Preliminary mechanism studies revealed that compound 4m caused reactive oxygen species accumulation, cell membrane destruction, and deregulation of histone acetylation. These findings indicated that 1-carbamoyl β-carboline can be selected as a promising model for the discovery of novel and broad-spectrum fungicide candidates.

Tunicyclin L, a cyclic peptide from Psammosilene tunicoides: Isolation, characterization, conformational studies and biological activity

Tunicyclin L (1), cyclo (L-Pro¹-Gly-L-Phe¹-L-Ile-L-Pro²-L-Phe² -L-Thr-L-Val), and 11 known compounds, including one cyclic peptide (2), eight carboline alkaloids (3 -10), one lignan (11) and one flavone (12) were isolated from the roots of Psammosilene tunicoides. Their structures were elucidated on the basis of extensive UV, IR, MS, NMR spectroscopic data and comparison with literature. Single-crystal X-ray diffraction results revealed the stereochemistry of the 24-membered ring cyclic peptide (1). Among these known compounds, compound 6 was found to be a new natural product, and compounds 3, 4, and 11 were isolated from this plant for the first time. Five compounds (1, 3, 4, 7, and 9) showed moderate anti-acetylcholinesterase (AChE) activity.

A new antitrypanosomal alkaloid from the Red Sea marine sponge Hyrtios sp

The antitrypanosomally active crude extract of the sponge Hyrtios sp. was subjected to metabolomic analysis using liquid chromatography coupled with high resolution electrospray ionization mass spectrometry (LC-HR-ESIMS) for dereplication purposes. As a result, a new alkaloid, hyrtiodoline A (1), along with other four known compounds (2-5) were reported. The structures of compounds 1-5 were determined by spectroscopic analyses, including 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HRESI-MS) experiments, as well as comparison to the literature. We further investigated the antitrypanosomal activity of the five compounds, where compound 1 exhibited the most potent antitrypanosomal activity, with a half-maximal inhibitory concentration (IC₅₀) value of 7.48 µM after 72 h.