10b-Substituted hexahydropyrrolo-isoquinolines: studies on diastereoselective formation of a quaternary carbon stereocenter via N-acyliminium ion cyclization

cis-Dihydroxylated α-Trifluoromethylated N,O-Acetal from l-Tartaric Acid: Synthesis of Tetrasubstituted Stereocenter via Diastereoselective Pictet-Spengler Cyclization of N-Acyliminium Ions

The synthesis of cyclic, chiral α-trifluoromethylated N,O-acetals having a protected cis-diol moiety has been readily achieved in two steps from a known bis-Weinreb amide derived from l-tartaric acid. The reaction of O-acetyl analogues of these N,O-acetals with triflic acid in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) at 0 °C generated in situ the corresponding electrophilic α-trifluoromethyl N-acyliminium ions that undergo Pictet-Spengler-type cyclizations. After only 10 min of reaction, the original enantiopure aza-tricyclic scaffolds bearing a trifluoromethyl substituent at the bridgehead position were obtained with diastereoselectivities ranging from 75:25 to 97:3.

Anticancer Effect of a Novel Octahydropyrazino[2,1-a:5,4-a']diisoquinoline Derivative and Its Synergistic Action with Nigella sativa in Human Gastric Cancer Cells

Many studies have shown that naturally occurring compounds may support prevention and treatment of various diseases, including cancer. Pharmacological investigations revealed a wide spectrum of Nigella sativa biological activities. Combining natural compounds together with synthetic drugs may increase the anticancer activity and limit severe side effects of such a treatment and may be an alternative to monotherapy. The aim of the study was to evaluate the cytotoxic and proapoptotic effects of a novel octahydropyrazino[2,1-a:5,4-a']diisoquinoline derivative and its effect in combination with Nigella sativa seed oil or extract in human gastric cancer cells (AGS). Etoposide was used as a reference. Our studies proved that combination strategy based on novel octahydropyrazino[2,1-a:5,4-a']diisoquinoline derivative (OM-90) with Nigella sativa seed oil or extract represents the strongest efficacy in AGS cancer cells as compared to monotherapy and combined treatment with Nigella sativa seed oil or extract together with etoposide. Such a combination also leads to the activation of mitochondrial pathway, which plays a significant role in molecular mechanism of induction of apoptosis by these compounds.

Diastereoselective Ritter-like Reaction on Cyclic Trifluoromethylated N,O-Acetals Derived from l-Tartaric Acid

Despite the presence of the highly electron-withdrawing fluorinated substituent, cyclic α-trifluoromethylated N-acyliminium ions were successfully generated from fluorinated O-acetyl-N,O-acetal l-tartaric acid derivatives. The addition of nitriles on these intermediates occurred with high to excellent syn diastereoselectivity and led, in most cases, to oxazolines and amides as single diastereomers. The diastereoselectivity of the addition and the nature of the reaction product depend on the substituents on the hydroxyl groups of the tartaric acid scaffold. This methodology gave access to enantiopure, highly functionalized 5-(trifluoromethyl)pyrrolidin-2-one derivatives, bearing the fluorinated substituent on a tetrasubstituted carbon.

Biological evaluation of octahydropyrazin[2,1-a:5,4-a']diisoquinoline derivatives as potent anticancer agents

In this study, we evaluated the cytotoxic activity and antiproliferative potency of novel octahydropyrazin[2,1-a:5,4-a']diisoquinoline derivatives (1-7) in MCF-7 and MDA-MB-231 breast cancer cell lines. Annexin V binding assay and disruption of the mitochondrial potential were performed to determine apoptosis. The activity of caspases 3, 8, 9, and 10 was measured after 24 h of incubation with tested compounds to explain detailed molecular mechanism of induction of apoptosis. The results from experiments were compared with effects obtained after incubation in the presence of camptothecin and etoposide. Our study demonstrated that the most active compounds in both analyzed breast cancer cell lines were compounds 3 and 4. We also observed that all compounds induced apoptosis. We demonstrated the higher activity of caspases 3, 8, 9, and 10, which confirmed that induction of apoptosis is associated with external and internal cell death pathway. Our study revealed that the novel compounds in group of diisoquinoline derivatives are promising candidates in anticancer treatment by activation of both extrinsic and intrinsic apoptotic pathways.

Asymmetric Synthesis of Isoquinoline Alkaloids: 2004-2015

In the past decade, the asymmetric synthesis of chiral nonracemic isoquinoline alkaloids, a family of natural products showing a wide range of structural diversity and biological and pharmaceutical activity, has been based either on continuation or improvement of known traditional methods or on new, recently developed, strategies. Both diastereoselective and enantioselective catalytic methods have been applied. This review describes the stereochemically modified traditional syntheses (the Pictet-Spengler, the Bischler-Napieralski, and the Pomeranz-Fritsch-Bobbitt) along with strategies based on closing of the nitrogen-containing ring B of the isoquinoline core by the formation of bonds between C₁-N₂, N₂-C₃, C₁-N₂/N₂-C₃, and C₁-N₂/C₄-C_4a atoms. Methods involving introduction of substituents at the C1 carbon of isoquinoline core along with syntheses applying various biocatalytic techniques have also been reviewed.