A. F. M. Motiur Rahman

Chapter Five - Gefitinib

Gefitinib (Iressa®) is a selective inhibitor of epidermal growth factor, a growth factor that plays a pivotal role in the control of cell growth, apoptosis, and angiogenesis. Gefitinib is clinically used for the treatment of chemoresistant non-small cell lung cancer patients. Gefitinib is freely soluble in dimethylsulphoxide but slightly soluble in methanol and ethanol. Several methods of gefitinib synthesis are included in this review. UV spectroscopy of gefitinib showed a λmax of approximately 331 nm, whereas IR spectroscopy principal peaks were observed at 3400 cm− 1 (NH), 2956 cm− 1 (CH2, CH, alkyl), 1625 cm− 1 (CC, CN), 1500 cm− 1 (HCCH, aryl), 1110 cm− 1 (CO), 1028 cm− 1 (CF). In addition, different analytical methods for determination of gefitinib are also described in this review. Pharmacokinetically, after oral administration, gefitinib is slowly absorbed with bioavailability of approximately 60% in human. Gefitinib is metabolized extensively in the liver into five metabolites by cytochrome P450s, primarily by CYP3A4 and to a lesser extent by CYP3A5 and CYP2D6. Gefitinib is eliminated mainly hepatically with total plasma clearance of 595 mL/min after intravenous administration. Most of the adverse effects associated with gefitinib therapy are mild to moderate in severity and are usually reversible and manageable with appropriate intervention, such as diarrhea, dry skin, rash, nausea, and vomiting.

Chapter 9 – Sunitinib Malate

Sunitinib malate (Sutent®, Pfizer Inc.) is a multitargeted tyrosine kinase inhibitor that inhibits tumor cell proliferation and angiogenesis. It is approved for the treatment of renal cell carcinoma (RCC) and imatinib-resistant gastrointestinal stromal tumor (GIST). Sunitinib malate salt is a photosensitive yellowish powder soluble in DMSO, whereas very poorly soluble in ethanol and water. Several methods of sunitinib synthesis are included in this review. UV spectroscopy of sunitinib showed a λmax of approximately 430 nm, whereas IR spectroscopy of sunitinib base were reported at 3298, 3230, 2968, 1676, 1627, 1590, 1544, 1498, 1334 cm-1. In addition, chromatographic, spectrofluorimetric, and immunoassay methods for the analysis of sunitinib are also described. Pharmacokinetically, following a single oral dose in healthy and cancer subjects, peak plasma sunitinib concentrations occur between 6 and 12h post dose, with prolonged half-lives of approximately 40 h. Sunitinib is primarily metabolized by CYP3A4 to produce its primary active metabolite, SU12662, which is further metabolized by CYP3A4 into inactive metabolites. Sunitinib is primarily eliminated with the feces (61%), with renal elimination accounting for only 16% of the administered dose.

2,2-dimethyl-2H-pyran-derived alkaloids I. Practical synthesis of acronycine and benzo[b]acronycine and their biological properties.

The 2,2-dimethyl-2H-pyran-derived alkaloids acronycine and its demethylated congeners were prepared in three steps from anthranilic acid and phloroglucinol. The phenylboronic acid-mediated interamolecular cyclization reaction of 1,3-dihydroxyacridone and 3-methylbut-2-enal was employed as a key step, which was also applied to the synthesis of related cytotoxic benzo[b]acronycine. Inhibitory activities of the compounds prepared on topoisomerase I and II as well as their cytotoxicities were evaluated. Cytotoxicity of 2 is closely related to the strong inhibitory activity against topo II at 20 μM level.

A concise synthesis and evaluation of new malonamide derivatives as potential α-glucosidase inhibitors.

A series of new malonamide derivatives were synthesized by Michael addition reaction of N(1),N(3)-di(pyridin-2-yl)malonamide into α,β-unsaturated ketones mediated by DBU in DCM at ambient temperature. The inhibitory potential of these compounds in vitro, against α-glucosidase enzyme was evaluated. Result showed that most of malonamide derivatives were identified as a potent inhibitors of α-glucosidase enzyme. Among all the compounds, 4K (IC50=11.7 ± 0.5 μM) was found out as the most active one compared to standard drug acarbose (IC50=840 ± 1.73 μM). Further cytotoxicity of 4a-4m were also evaluated against a number of cancer and normal cell lines and interesting results were obtained.

Design, synthesis, topoisomerase I & II inhibitory activity, antiproliferative activity, and structure-activity relationship study of pyrazoline derivatives: An ATP-competitive human topoisomerase IIα catalytic inhibitor.

A series of pyrazoline derivatives (5) were synthesized in 92-96% yields from chalcones (3) and hydrazides (4). Subsequently, topo-I and IIα-mediated relaxation and antiproliferative activity assays were evaluated for 5. Among the tested compounds, 5h had a very strong topo-I activity of 97% (Camptothecin, 74%) at concentration of 100 μM. Nevertheless, all the compounds 5a-5i showed significant topo II inhibitory activity in the range of 90-94% (Etoposide, 96%) at the same concentration. Cytotoxic potential of these compounds was tested in a panel of three human tumor cell lines, HCT15, BT474 and T47D. All the compounds showed strong activity against HCT15 cell line with IC50 at the range of 1.9-10.4 μM (Adriamycin, 23.0; Etoposide, 6.9; and Camptothecin, 7.1 μM). Moreover, compounds 5c, 5f and 5i were observed to have strong antiproliferative activity against BT474 cell lines. Since, compound 5d showed antiproliferative activity at a very low IC50 thus 5d was then selected to study on their mode of action with diverse methods of ATP competition assay, ATPase assay and DNA-topo IIα cleavable complex assay and the results revealed that it functioned as a ATP-competitive human topoisomerase IIα catalytic inhibitor. Further evaluation of endogenous topo-mediated DNA relaxation in cells has been conducted to find that, 5d inhibited endogenous topo-mediated pBR322 plasmid relaxation is more efficient (78.0 ± 4.7% at 50 μM) than Etoposide (36.0 ± 1.7% at 50 μM).

A preliminary study of arecoline and guvacoline presence in the saliva of a "betel-quid" chewer using liquid-chromatography ion trap mass spectrometry.

It has been reported that the parasympathomimetic alkaloid arecoline and the nootropic agent guvacoline have been detected in areca nut (Areca catechu L.) during extraction using a basic medium. Here, we have studied the detection of arecoline and guvacoline in vivo in saliva of a “betel-quid” chewer using liquid-chromatography ion trap mass spectrometry. In this paper, we provide evidence that guvacoline is absent in the neutral aqueous extract of betel nut, but is present in abundance in the aqueous extract with added lime (pH 11.9). In an in vivo experiment, we demonstrated that guvacoline is present in the salivary extracts in the mouth with lime (pH 9.5) and without lime (pH 5.3).

In vitro investigation of metabolic profiling of newly developed topoisomerase inhibitors (ethyl fluorescein hydrazones, EtFLHs) in RLMs by LC–MS/MS

Metabolic profiling of newly reported five topoisomerase inhibitors namely ethyl fluorescein hydrazones (EtFLHs) were studied in rat liver microsomes (RLMs) and the data were acquired in a liquid chromatography (LC) ion trap mass spectrometry. Hydroxyl group containing EtFLHs derivatives (1-3) were bio-transformed into hydrolyzed, mono-hydroxylated and hydrolyzed together with mono-hydroxylated metabolites. On the other hand, nitro and methoxy groups containing EtFLHs derivatives (4-5) were bio-transformed into hydrolyzed, hydrolyzed together with mono-hydroxylated and azo-reductive metabolites in the presence of NADPH. No metabolites were observed in the absence of either NADPH or microsomes for the compounds (1-5), indicating a likely involvement of CYP450 enzymes and cofactor NADPH in the metabolisms.

Chapter Nine – Vardenafil Dihydrochloride

Vardenafil (VAR) is synthetic, highly selective, and potent inhibitor of phosphodiesterase-5 which competitively inhibits cyclic guanosine monophosphate (cGMP) hydrolysis and thus increases cGMP levels. It is clinically approved for treatment of erectile dysfunction in men, including diabetic and postprostatectomy patients. Several methods of VAR synthesis are included in this review. UV spectroscopy of VAR showed a λmax of approximately 270nm, and IR spectroscopy principal peaks were observed at 3420 (NH), 1724 (CO), 1600 (CC, and CN), 1491 (CHCH) cm(-1). Characteristic carbonyl (CO) carbon was observed in nuclear magnetic resonance spectroscopy at 162.44ppm. The molecular mass was observed at m/z=488.9 (molecular weight=488.2) and the fragmentation pattern was studied using ion trap mass spectrometry. In addition, different analytical methods for determination of vardenafil are also described in this profile. Pharmacokinetic properties of VAR have great impact on efficacy. VAR is rapidly absorbed and slowly metabolized, with an absolute bioavailability of 15%. It is extensively metabolized by CYP3A4 into several metabolites, the most pharmacologically active of which is N-desethyl VAR (M1). The elimination half-life of VAR and M1 is about 4-5h. VAR is primarily excreted as metabolites in the feces and to a small extent in urine. VAR is generally well tolerated, with a favorable safety profile and few transient side effects, including headache, flushing, dyspepsia, and rhinitis.

Synthesis and Fragmentation Behavior Study of n-alkyl/benzyl Isatin Derivatives Present in Small/Complex Molecules: Precursor for the Preparation of Biological Active Heterocycles

N-Alkyl/benzyl substituted isatin derivatives are intermediates and synthetic precursors for the preparation of biolog- ical active heterocycles. N-alkyl/benzyl isatins have showed various biological activities, such as cytotoxicity, antiviral, caspase inhibition, cannabinoid receptor 2 agonists for the treatment of neuropathic pain, etc. In this study, N-alkyl/benzyl isatin deriva- tives were synthesized from isatin and alkyl/benzyl halides in presence of K2CO3 in DMF and excellent to quantitative yields (~95%) were obtained. Isatins and benzyl-isatins were condensed with fluorescein hydrazide to form fluorescein hydrazone. All the compounds were subjected to their fragmentation behavior study using LC/MS n . N-Alkyl substituted isatin derivatives frag- mented at nitrogen-carbon (N-C) bond, hence gave daughter ion as (RN+H) + . Whereas, N-benzyl substituted isatin derivatives fragmented at carbon-carbon (C-C) bond of alkyl chain which linked with nitrogen molecules, therefore gave N-methyl frag- ments (RNCH2) + . This study demonstrated that, isatin moiety present in a small/large molecule or in a matrix of reaction mixture with/without N-alkyl/benzyl substituents can be identified by mass spectroscopic fragmentation behavior study.

Synthesis and properties of ruthenium(II) complexes of 3,3′-polymethylene-2-(pyrid-2′-yl)benzo[b]-1,10-phenanthrolines

Coordination abilities of unsymmetrical tridentate ligands, 3,3′-polymethylene-2-(pyrid-2′-yl)-benzo[b]-1,10-phenanthrolines (4) were studied. Reactions of the 3,3′-di- and 3,3′-trimethylene-2-(pyrid-2′-yl)benzo[b]-1,10-phenanthrolines (4b and 4c) with RuCl3 ⋅ 3H2O afforded [Ru(4b)2]2+ and [Ru(4c)2]2+ in 57% and 78% yield, respectively, while reactions of the parent non-bridged ligand (4a), tetramethylene-bridged ligand (4d), and fully aromatized ligand (4e) afforded a messy mixture. Reactions of 4 with Ru(tpy)Cl3 (tpy = 2,2′;6′,2″-terpyridine) afforded [Ru(tpy)(4)]2+ in 61–72% yields. UV absorption spectra of the ligands showed four ligand-centered (LC) π–π* transitions and their Ru complexes showed four LC π–π* transitions and one Ru(dπ) → ligand(π*) MLCT. The ligands showed three major emission maxima (λ emission) in the region of 393–418, 416–445, and 437–471 nm in which λ emission is highly dependent on the length of the methylene bridge connecting C3 of benzo[b]-1,10-phenanthroline and C3 of pyridine. Ru complexes with fully aromatic ligand, [Ru(tpy)(4e)]2+, and the most distorted ligand, [Ru(tpy)(4d)]2+, showed two emission maxima at 410 and 444–446 nm, while the others showed one emission at 410 nm. Each of the emission maxima is bathochromatically shifted from the complex with the most distorted ligand (4d) to the complex with fully aromatized planar ligand (4e) indicating lower energy emission.