Photochemistry of phthalimidoadamantane dipeptides: effect of amino acid side chain on photocyclization

A series of dipeptides 1 was synthesized that at the N-site contained 3-(N-phthalimidoadamantane-1-carboxylic acid and at the C-site different aliphatic or aromatic L- or D-amino acids. The photochemical reaction of dipeptides 1 under acetone-sensitized conditions gave simple decarboxylation products 6, and decarboxylation-induced cyclization products 7, as well as some secondary products 8 and 9 formed by elimination of H2O or ring enlargement, respectively. Molecules 9 undergo secondary photoinduced H-abstractions by the phthalimide chromophore, delivering more complex polycycles 11. The photodecarboxylation-induced cyclization to 7 was observed only with phenylalanine (Phe), proline (Pro), leucine (Leu) and isoleucine (Ile). Contrary to dipeptides with Phe, the cyclization takes place with almost complete racemization at the amino acid chiral center, but diastereoselectively giving only one pair of enantiomers. The conducted investigation is important as it provides the breath and the scope of dipeptide cyclizations activated by phthalimides.

Antihyperlipidemic activity of glycoconjugated phthalimides in mice submitted to a model of dyslipidemia and insulin resistance

Alterations in lipid and lipoprotein metabolism are factors that trigger several negative metabolic complications. Hyperlipidemia is the starting point for the development of comorbidities of the cardiovascular system, such as atherosclerosis. The search for compounds that reduce high levels of total cholesterol and triglycerides has been widely reported in several publications in the literature. Phthalimide derivatives have been extensively researched with various biological actions. In this study we evaluated the antihyperlipidemic ability of three phthalimide derivatives (FGT-2, FGT-3 and FGT-4) on a model of obesity and insulin resistance in mice. The animals were submitted to a hyperlipid diet for 60 days. On the thirtieth day they were treated with phthalimides (20 mg/kg). The positive control group was treated with Simvastatin (20 mg/kg) and the negative control received only the carboxymethylcellulose vehicle. Biochemical and histological analyzes of all groups were analyzed. The animals treated with phthalimidic derivatives had a reduction in total cholesterol, low density and very low density lipoproteins (LDL-c and VLDL-c), triglycerides and fasting glycemia when compared to the negative control group. The treated animals also showed good results when analyzing the atherogenic indexes Castelli i and II and the ratio Triglycerides/HDL-c. In the oral glucose tolerance test and in the insulin tolerance test, animals treated with phthalimides were more sensitive to the action of the hormone regulating carbohydrate uptake. In the evaluation of the transaminases (AST/ALT), the animals of the group treated with phthalimides presented a lower elevation than the other groups of the experiment, the same observed with the uric acid evaluation. Histological analyzes were performed on liver, kidney, heart and pancreas samples. The groups treated with the compounds FGT-2 and FGT3 presented discrete alterations in the liver and kidney. FGT-4 did not present histological alterations for both tissues and the three phthalimide derivatives did not cause alterations in the other organs. These results suggest that the phthalimides tested can act as antihyperlipidemic agents and have a pleiotropic action, by acting also reducing glycemia in insulin resistance model mimicking diabetes mellitus type 2. These compounds may appear as a new approach in the treatment of obesity and complications, which are multifaceted.

Implementation of a Pregnancy Prevention Programme (PPP) with a Controlled Distribution System (CDS) for the Generic Teratogenic Phthalimides Thalidomide, Lenalidomide and Pomalidomide

Thalidomide (α-phthalimidoglutaride) was marketed in the 1950s and early 1960s; it was promoted as a sedative-hypnotic agent with minimal hangover. It was available in some countries as an over-the-counter medicine. Publications reporting profound teratogenic effects with thalidomide brought about major revisions to the monitoring of the safety of medicines. As a consequence of previously unrecognised teratogenic effects, it has been estimated that over 12,000 children were born with a range of defects and disabilities, including severe congenital anomalies. Notably, it has been hypothesised that around 40% of babies with thalidomide-induced malformations born during the 1950s and 1960s died in the neonatal period. The commonest causes of death were atresia of the small bowel, cardiac or renal malformations. Nevertheless, phocomelia (as a typical manifestation of thalidomide´s teratogenic effects) has been reported once again after thalidomide was approved for use in areas where leprosy is endemic. As a result, thalidomide embryopathy remains an important topic in countries such as Brazil. Nowadays thalidomide is approved around the world for the treatment of a wide range of conditions, including leprosy, Crohn's disease, multiple myeloma, and certain malignant solid tumours. Second-generation immunmodulatory drugs including lenalidomide and pomalidomide have received approval for use in the management of various forms of neoplastic disease. Based on clinical experience with thalidomide and its derivatives, learnings have been transferred to further research on a subset of substituted phthalimides each of which has a high risk of causing teratogenic effects. This group of phthalimides is classified within regulatory science as human teratogens. In order to gain approval, a Pregnancy Prevention Programme (PPP), along with a Controlled Distribution System (CDS) is required. The challenges of PPPs in particular for a generic manufacturer have been described, including Raising of awareness, and education; Special aspects of data collection and evaluation; Ethically and socially relevant aspects, and Utilising existing information technology and infrastructure. This paper highlights the risks of unplanned pregnancies, provides information on the regulatory background, and regulatory expectations. Our aim is to provide insights and practical learnings that have impacted operational risk management with the teratogenic phthalimides. Opportunities are presented that may support the implementation of harmonised approaches for PPP and CDS using existing IT-systems across countries and companies.

Tautomeric influence on the photoinduced birefringence of 4-substituted phthalimide 2-hydroxy Schiff bases in PMMA matrix

The photoinduced birefringence of two 4-substituted phthalimide 2-hydroxy Schiff bases, containing salicylic (4) and 2-hydroxy-1-naphthyl (5) moieties has been investigated in PMMA matrix. Their optical behaviour as nanocomposite films was revealed by combined use of DFT quantum chemical calculations (in ground and excited state) and experimental optical spectroscopy (UV-Vis and fluorescence). The results have shown that solid-state reversible switching takes place by enol/keto tautomerization and Z/E isomerization. Birefringence study was performed in the PMMA nanocomposite films using pump lasers at λ_rec = 355 nm and λ_rec = 442 nm. Fast response time and high stability of anisotropy up to 58% for (4) and 95% for (5) after turning off the excitation laser, was observed, which makes these materials appropriate candidates for cutting-edge optical information technology materials. The possibility for multiple cycles of recording, reading and optical erasure of the photoinduced birefringence at λ_rec = 442 nm in 5 has been demonstrated. The obtained results have shown that the maximum value of the measured birefringence is close to the anisotropic characteristics of the most frequently used azo materials.

Indirect solvent assisted tautomerism in 4-substituted phthalimide 2-hydroxy-Schiff bases

The paper presents the synthesis and characterization of two 4-substituted phthalimide 2-hydroxy-Schiff bases containing salicylic (4) and 2-hydroxy-1-naphthyl (5) moieties. The structural differences of 2-hydroxyaryl substituents, resulting in different enol/keto tautomeric behaviour, depending on the solvent environment were studied by absorption UV-Vis spectroscopy. Compound 5 is characterized by a solvent-dependent tautomeric equilibrium (K_T in toluene = 0.12, acetonitrile = 0.22 and MeOH = 0.63) while no tautomerism is observed in 4. Ground state theoretical DFT calculations by using continuum solvation in MeOH indicate an energy barrier between enol/keto tautomer 5.6 kcal mol^-1 of 4 and 0.63 kcal mol^-1 of 5, which confirms the experimentally observed impossibility of the tautomeric equilibrium in the former. The experimentally observed specific solvent effect in methanol is modeled via explicit solvation. The excited state intramolecular proton transfer (ESIPT) was investigated by steady state fluorescence spectroscopy. Both compounds show a high rate of photoconversion to keto tautomers hence keto emissions with large Stokes shifts in five alcohols (MeOH, EtOH, 1-propanol, 1-butanol, and 1-pentanol) and various aprotic solvents (toluene, dichlormethane, acetone, AcCN). According to the excited state TDDFT calculations using implicit solvation in MeOH, it was found that enol tautomers of 4 and 5 are higher in energy compared to the keto ones, which explains the origin of the experimentally observed keto form emission.

Synthesis and biological activity of new phthalimides as potential anti-inflammatory agents

The overproduction of nitric oxide (NO) plays an important role in a variety of pathophysiological processes, including inflammation. Therefore, the suppression of NO production is a promising target in the design of anti-inflammatory agents. In the present study, a series of phthalimide analogs was synthesized, and their anti-inflammatory activities were evaluated using lipopolysaccharide (LPS)-stimulated NO production in cultured murine macrophage RAW264.7 cells. A structure-activity relationship study showed that the free hydroxyl group at C-4 and C-6 and the bulkiness of the N-substituted alkyl chain are associated with biological activity. Among the series of phthalimide derivatives, compound IIh exhibited potent inhibitory activity, with an IC₅₀ value of 8.7µg/mL. Further study revealed that the inhibitory activity of compound IIh was correlated with the down-regulation of the mRNA and protein expression of LPS-stimulated inducible nitric oxide synthase (iNOS). Compound IIh also suppressed the induction of the pro-inflammatory cytokines tumor necrosis factor-α and interleukin-1β in LPS-stimulated RAW 264.7 cells. The anti-inflammatory activity of compound IIh was also found to be associated with the suppression of the Toll-like receptor (TLR)4 signaling pathway by down-regulating the activation of interferon regulatory factor 3 (IRF-3) and interferon-β and signal transducer expression. These findings demonstrate that novel phthalimides might be potential candidates for the development of anti-inflammatory agents.

Thalidomide analogues: Tumor necrosis factor-alpha inhibitors and their evaluation as anti-inflammatory agents

A series of related thalidomide derivatives (2-9) were synthesized by microwave irradiation and evaluated for anti-inflammatory activity. Such activity was assessed in vivo and ex vivo. Compounds 2, 8 and 9 showed the highest levels of inhibition of TNF-α production. On rat paw edema and hyperalgesia assays, compound 9, (1,4-phthalazinedione) demonstrated the highest in vivo anti-inflammatory activity. Thus, compound 9 can be considered as a promising compound to be subjected to further modification to obtain new agents for the treatment of inflammatory diseases.

Structure-based design of phthalimide derivatives as potential cyclooxygenase-2 (COX-2) inhibitors: anti-inflammatory and analgesic activities

A group of 30 cyclic imides (1-10a-c) was designed for evaluation as a selective COX-2 inhibitor and investigated in vivo for anti-inflammatory and analgesic activities. Compounds 6a, 6b, 7a and 7b exhibit optimal COX-2 inhibitory potency (IC50 = 0.18, 0.24, 0.28 and 0.36 μM; respectively) and selectivity index (SI) range of 363-668. In vitro COX-1/COX-2 inhibition structure-activity studies identified compound 6a as a highly potent (IC50 = 0.18 μM), and an extremely selective [COX-2 (SI) = 668] comparable to celecoxib [COX-2 (SI) > 384], COX-2 inhibitor that showed superior anti-inflammatory activity (ED50 = 54.0 mg/kg) relative to diclofenac (ED50 = 114 mg/kg). Molecular Docking study of the synthesized compound 6a into the active site of COX-2 revealed a similar binding mode to SC-558, a selective COX-2 inhibitor. Docking study showed that the methoxy moeities of 6a inserted deep inside the 2°-pocket of the COX-2 active site, where the O-atoms of such groups underwent an H-bonding interaction with His(90) (3.02 Å), Arg(513) (1.94, 2.83 Å), and Gln(192) (3.25 Å).

Antiproliferative and antiviral activity of three libraries of adamantane derivatives

Three libraries of adamantane derivatives were synthesized and evaluated for antiviral and antiproliferative activities against a broad variety of DNA and RNA viruses. Whereas none of the compounds exhibit antiviral activity at subtoxic concentrations, antiproliferative activity was found against murine leukemia cells (L1210), human T-lymphocyte cells (CEM), and cervix carcinoma cells (HeLa) for 4, 8, and 10.