Synthesis and biological evaluation of diastereoisomerically pure N,O-nucleosides

New 3-(Dibenzyloxyphosphoryl)isoxazolidine Conjugates of N1-Benzylated Quinazoline-2,4-diones as Potential Cytotoxic Agents against Cancer Cell Lines

In this study, a new series of cis and trans 5-substituted-3-(dibenzyloxyphosphoryl)isoxazolidines 16a-g were synthesized by the 1,3-dipolar cycloaddition reaction of N-benzyl-C-(dibenzyloxyphosphoryl)nitrone and selected N1-allyl-N3-benzylquinazoline-2,4-diones. All the obtained trans-isoxazolidines 16a-g and the samples enriched in respective cis-isomers were evaluated for anticancer activity against three tumor cell lines. All the tested compounds exhibited high activity against the prostate cancer cell line (PC-3). Isoxazolidines trans-16a and trans-16b and diastereoisomeric mixtures of isoxazolidines enriched in cis-isomer using HPLC, namely cis-16a/trans-16a (97:3) and cis-16b/trans-16b (90:10), showed the highest antiproliferative properties towards the PC-3 cell line (IC50 = 9.84 ± 3.69-12.67 ± 3.45 μM). For the most active compounds, induction apoptosis tests and an evaluation of toxicity were conducted. Isoxazolidine trans-16b showed the highest induction of apoptosis. Moreover, the most active compounds turned out safe in vitro as none affected the cell viability in the HEK293, HepG2, and HSF cellular models at all the tested concentrations. The results indicated isoxazolidine trans-16b as a promising new lead structure in the search for effective anticancer drugs.

1,3-Dipolar cycloaddition of nitrones: synthesis of multisubstituted, diverse range of heterocyclic compounds

The 1,3-dipolar cycloaddition reaction of nitrone is one of the most important methods for the synthesis of different sizes of heterocycles which have enormous applications in natural products, biologically active molecules and pharmaceuticals.

Advancement in the development of heterocyclic nucleosides for the treatment of cancer - A review

Cancer diseases are widely recognised as an important medical problem and killing millions of people in a year. Chemotherapeutic drugs are successful against cancer in many cases and different compounds, including the analogues of natural substances, may be used for anticancer agents. Nucleoside analogues also have become a necessity for the treatment of cancer diseases. Nucleoside, nucleotide and base analogues have been utilised for decades for the treatment of viral pathogens, neoplasms and in anticancer chemotherapy. This review focuses on the different types of nucleosides and their potential role as anticancer agents. It also discusses the nucleoside analogues approved by FDA and in process of approval. The effect of the substitution on the nucleoside analogues and their pharmacological role is also discussed in the review. Owing to the advances in computational chemistry, it concludes with the future advancement and possible outcome of the nucleoside analogues. Also, it depicts the development of heterocyclic nucleoside analogues, explores the QSAR of the synthesised compounds and discusses the 3 D QSAR pharmacophore modelling in order to examine their potential anti-cancer activities.

Ene Reaction of Nitrosocarbonyl Mesitylene with the Cinnamyl Alcohol: Metabolic Activity and Apoptosis of the Synthetized 6-Chloropurine N,O-Nucleoside Analogues

Nitrosocarbonyl mesitylene intermediate undergoes an ene reaction with cinnamyl alcohol affording the corresponding 5-hydroxy-isoxazolidine in fair yields. The synthesized 5-acetoxy-isoxazolidine serves as synthon for the preparation of 6-chloropurine N,O-nucleoside analogues, according to the Vorbrüggen reaction. The compounds were evaluated for their metabolic and apoptotic activity, and their structure-activity relationship is discussed.

Antiproliferative activity of novel isatinyl/indanyl nitrones (INs) as potential spin trapping agents of free radical intermediates

A series of ketonitrones derived from isatin and indanone (INs) were synthesized and evaluated for their antiproliferative activities against several human cancer cell lines. Then, the antioxidant properties of these substrates were measured by the DPPH test to report their biological activity in terms of their spin trapping action. In particular, one substrate has showed very high biological and scavenging activity, probably due to the strong correlation between its spin trapping activity and structure.

KuQuinones Equilibria Assessment for Biomedical Applications

A small library of pentacyclic quinoid compounds, called KuQuinones (KuQs), has been prepared through a one-pot reaction. KuQuinones complex structure is made up by two naphthoquinone units connected by a five-membered ring. Due to KuQs structural features, keto-enol tautomerization in solution likely occurs, leading to the generation of four different species, i.e., the enol, the enolate, the external enol and the diquinoid species. The interchange among KuQ tautomers leads to substantial spectral variations of the dye depending on the experimental conditions used. The comprehension of tautomeric equilibria of this new class of quinoid compounds is strongly required in order to explain their behavior in solution and in biological environment. UV-vis, ¹H NMR spectroscopies, and DFT calculations resulted appropriate tools to understand the nature of the prevalent KuQuinone species in solution. Moreover, due to the structural similarity of KuQuinones with camptothecin (CPT), a largely used anticancer agent, KuQs have been tested against Cisplatin-resistant SKOV3 and SW480 cancer cell lines. Results highlighted that KuQs are highly active toward the analyzed cell lines and almost nontoxic for healthy cell, indicating a high specific activity.

Nitrones and nucleobase-containing spiro-isoxazolidines derived from isatin and indanone: solvent-free microwave-assisted stereoselective synthesis and theoretical calculations

Here, we present a highly efficient approach to nucleobase-containing spiro-isoxazolidines with potential biological activity starting from isatinyl/indanyl nitrones.

Isoxazolidine: A Privileged Scaffold for Organic and Medicinal Chemistry

The isoxazolidine ring represents one of the privileged structures in medicinal chemistry, and there have been an increasing number of studies on isoxazolidine and isoxazolidine-containing compounds. Optimization of the 1,3-dipolar cycloaddition (1,3-DC), original methods including electrophilic or palladium-mediated cyclization of unsaturated hydroxylamine, has been developed to obtain isoxazolidines. Novel reactions involving the isoxazolidine ring have been highlighted to accomplish total synthesis or to obtain bioactive compounds, one of the most significant examples being probably the thermic ring contraction applied to the total synthesis of (±)-Gelsemoxonine. The unique isoxazolidine scaffold also exhibits an impressive potential as a mimic of nucleosides, carbohydrates, PNA, amino acids, and steroid analogs. This review aims to be a comprehensive and general summary of the different isoxazolidine syntheses, their use as starting building blocks for the preparation of natural compounds, and their main biological activities.

Novel isoxazolidine analogues of homonucleosides and homonucleotides

Isoxazolidine analogues of homonucleos(t)ides were synthesized from nucleobase-derived nitrones 20a-20e (uracil, 5-fluorouracil, 5-bromouracil, thymine, adenine) employing 1,3-dipolar cycloadditions with allyl alcohol as well as with alkenylphosphonates (allyl-, allyloxymethyl- and vinyloxymethyl- and vinylphosphonate). Besides reactions with vinylphosphonate the additions proceeded regioselectively to produce mixtures of major cis and minor trans 3,5-disubstituted isoxazolidines (d.e. 28–82%). From vinylphosphonate up to 10% of 3,4-disubstituted isoxazolidines was additionally produced. Vicinal couplings, shielding effects and 2D NOE correlations were employed in configurational assignments as well as in conformational analysis to find out preferred conformations for several isoxazolidines and to observe anomeric effects (pseudoaxial orientation of phosphonylmethoxy groups) for those obtained from vinyloxymethylphosphonate. None of the tested compounds were endowed in vitro with antiviral activity against a variety of DNA and RNA viruses at subtoxic concentrations (up to 250 μM) nor exhibited antiproliferative activity towards L1210, CEM, and HeLa cells (IC₅₀ = ≥100 μM).

Novel 5-arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates as nucleotide analogues

A series of 5-substituted 3-phosphonylated isoxazolidines have been obtained via cycloaddition of N-methyl-C-(diethoxyphosphoryl)nitrone with N-heteroaromatic acrylamides. Good trans/cis diastereoselectivities (d.e. 58-76%) of isomeric (3-diethoxyphosphoryl)isoxazolidines were observed. cis- and trans-Isoxazolidine phosphonates were evaluated for their antiviral activity against a broad range of DNA and RNA viruses but were found inactive. Their cytostatic activity toward L1210, CEM, and HeLa cells was also established, and compounds cis-12r and trans-11r having a 2,2-difluorobenzo[d][1,3]dioxole moiety slightly inhibited proliferation of HeLa cells at IC50 values of 186 and 179 μM, respectively.

Design, synthesis, antiviral, and cytostatic evaluation of novel isoxazolidine analogues of C-nucleotides

5-Aryl-2-methylisoxazolidin-3-yl-3-phosphonates have been synthesised from N-methyl-C-diethoxyphosphorylnitrone and vinyl aryls in good yields. Isoxazolidine phosphonates obtained herein were evaluated for activity against a broad range of DNA and RNA viruses. None of the compounds were endowed with antiviral activity nor cytostatic activity at 100 to 250 μM concentrations.

Modified N,O-Nucleosides: Design, Synthesis, and Anti-tumour Activity

A preliminary library of modified N,O-nucleosides was prepared and tested on a selected number of human cancer lines that include SKOV3, SW480, and K562. Thymine, N-benzyl substituents, and aromatic rings contribute to an increase of the biological activity, up to 10–25 μM, that appeared also reliant on the calculated lipophilicity of the nucleosides, expressed as cLogP, where P represents the partition coefficient of a solute between n-octanol and water.

Design, synthesis, antiviral and cytostatic evaluation of novel isoxazolidine nucleotide analogues with a carbamoyl linker

5-Arylcarbamoyl-2-methylisoxazolidin-3-yl-3-phosphonates have been synthesised from N-methyl-C-diethoxyphosphorylnitrone and N-arylacrylamides in good yields. cis- and trans-isoxazolidine phosphonates obtained herein were evaluated for activity against a broad range of DNA and RNA viruses. None of the compounds were endowed with antiviral activity at subtoxic concentrations. Isoxazolidines having phenyl substituted with halogen (Ar = 2-F-C₆H₄; 3-Br-C₆H₄; and 4-Br-C₆H₄) have been found to inhibit proliferation of L1210, CEM as well as HeLa cells with IC₅₀ in the 100–170 μM range.