Synthesis and pharmacological properties of 1-substituted 3-dimethylaminoalkoxy-1H-indazoles

Promising hit compounds against resistant trichomoniasis: Synthesis and antiparasitic activity of 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles

A series of 11 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles (2-12) has been prepared starting from 1-benzyl-5-nitroindazol-3-ol 13, and evaluated against sensitive and resistant isolates of the sexually transmitted protozoan Trichomonas vaginalis. Compounds 2, 3, 6, 9, 10 and 11 showed trichomonacidal profiles with IC₅₀ < 20 µM against the metronidazole-sensitive isolate. Moreover, all these compounds submitted to cytotoxicity assays against mammalian cells exhibited low non-specific cytotoxic effects, except compounds 3 and 9 which displayed moderate cytotoxicity (CC₅₀ = 74.7 and 59.1 µM, respectively). Those compounds with trichomonacidal effect were also evaluated against a metronidazole-resistant culture. Special mention deserve compounds 6 and 10, which displayed better IC₅₀ values (1.3 and 0.5 µM respectively) than that of the reference drug (IC₅₀ MTZ = 3.0 µM). The high activity of these compounds against the resistant isolate reinforces the absence of cross-resistance with the reference drug. The remarkable trichomonacidal results against resistant T. vaginalis isolates suggest the interest of 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles to be considered as good prototypes to continue in the development of new drugs with enhanced trichomonacidal activity, aiming to increase the non-existent drugs to face clinical resistance efficiently for those patients in whom therapy with 5-nitroimidazoles is contraindicated.

Syntheses of 1-Aryl-5-nitro-1H-indazoles and a General One-Pot Route to 1-Aryl-1H-indazoles

An efficient route to substituted 1-aryl-1H-indazoles has been developed and optimized. The method involved the preparation of arylhydrazones from acetophenone or benzaldehyde substituted by fluorine at C2 and nitro at C5, followed by deprotonation and nucleophilic aromatic substitution (S_NAr) ring closure in 45–90%. Modification of this procedure to a one-pot domino process was successful in the acetophenone series (73–96%), while the benzaldehyde series (63–73%) required a step-wise addition of reagents. A general one-pot protocol for 1-aryl-1H-indazole formation without the limiting substitution patterns required for the S_NAr cyclization has also been achieved in 62–78% yields. A selection of 1-aryl-1H-indazoles was prepared in high yield by a procedure that requires only a single laboratory operation.

1-[(7E)-7-(2-Chlorobenzylidene)-3-(2-chlorophenyl)-3,3a,4,5,6,7-hexahydro-2H-indazol-2-yl]ethanone

In the title compound, C22H20Cl2N2O, the diazole ring adopts a shallow envelope conformation with the methine C atom bonded to the adjacent chlorobenzene ring as the flap. The dihedral angles between the heterocyclic ring and the pendant chlorobenzene rings are 61.4 (2) and 80.3 (2)°. In the crystal, weak C—H...Cl interactions connect the molecules into [001] chains.

Propan-2-yl r-4-(4-fluoro-phen-yl)-3-hy-droxy-c-6-methyl-2-phenyl-4,5-dihydro-2H-indazole-t-5-carboxyl-ate

In the title compound, C₂₄H₂₃FN₂O₃, the cyclo­hexene ring adopts a screw-boat conformation. The fluorobenzene ring attached to the cyclo­hexene ring and the phenyl ring attached to the indazole moiety are inclined to one another by 57.77 (13)°. In the crystal, mol­ecules are linked by O—H⋯N and C—H⋯O hydrogen bonds, forming chains with C(5) and C(10) graph-set motifs. There are also C—H⋯π inter­actions present. The isopropoxycarbonyl group undergoes considerable thermal motion.

4,6-Bis(4-fluoro-phen-yl)-2-phenyl-1H-indazol-3(2H)-one

In the title compound, C₂₅H₁₆F₂N₂O, the pyrazole ring is almost planar (r.m.s. deviation = 0.028 Å) and makes a dihedral angle of 5.86 (11)° with the indazole benzene ring. The dihedral angle between the pyrazole ring and the unsubstituted phenyl ring is 28.19 (11)°. The dihedral angles between the unsubstituted phenyl and the two fluoro­phenyl groups are 57.69 (10) and 18.01 (10)°. In the crystal, mol­ecules are linked by inter­molecular N—H⋯O and C—H⋯F inter­actions, forming infinite chains along the b axis with graph-set motif R₃²(19). The crystal structure is further consolidated by π–π stacking [centroid–centroid distances = 3.5916 (13) and 3.6890 (13) Å] and C—H⋯π inter­actions.

The biology of spermatogenesis: the past, present and future

The physiological function of spermatogenesis in Caenorhabditis elegans, Drosophila melanogaster and mammals is to produce spermatozoa (1n, haploid) that contain only half of the genetic material of spermatogonia (2n, diploid). This half number of chromosomes from a spermatozoon will then be reconstituted to become a diploid cell upon fertilization with an egg, which is also haploid. Thus, genetic information from two parental individuals can be passed onto their offspring. Spermatogenesis takes place in the seminiferous epithelium of the seminiferous tubule, the functional unit of the mammalian testis. In mammals, particularly in rodents, the fascinating morphological changes that occur during spermatogenesis involving cellular differentiation and transformation, mitosis, meiosis, germ cell movement, spermiogenesis and spermiation have been well documented from the 1950s through the 1980s. During this time, however, the regulation of, as well as the biochemical and molecular mechanisms underlying these diverse cellular events occurring throughout spermatogenesis, have remained largely unexplored. In the past two decades, important advancements have been made using new biochemical, cell and molecular biology techniques to understand how different genes, proteins and signalling pathways regulate various aspects of spermatogenesis. These include studies on the differentiation of spermatogonia from gonocytes; regulation of spermatogonial stem cells; regulation of spermatogonial mitosis; regulation of meiosis, spermiogenesis and spermiation; role of hormones (e.g. oestrogens, androgens) in spermatogenesis; transcriptional regulation of spermatogenesis; regulation of apoptosis; cell-cell interactions; and the biology of junction dynamics during spermatogenesis. The impact of environmental toxicants on spermatogenesis has also become an urgent issue in the field in light of declining fertility levels in males. Many of these studies have helped investigators to understand important similarities, differences and evolutionary relationships between C. elegans, D. melanogaster and mammals relating to spermatogenesis. In this Special Issue of the Philosophical Transactions of the Royal Society B: Biological Sciences, we have covered many of these areas, and in this Introduction, we highlight the topic of spermatogenesis by examining its past, present and future.

Synthesis and biological evaluation of novel pyrazoles and indazoles as activators of the nitric oxide receptor, soluble guanylate cyclase

Database searching and compound screening identified 1-benzyl-3-(3-dimethylaminopropyloxy)indazole (benzydamine, 3) as a potent activator of the nitric oxide receptor, soluble guanylate cyclase. A comprehensive structure-activity relationship study surrounding 3 clearly showed that the indazole C-3 dimethylaminopropyloxy substituent was critical for enzyme activity. However replacement of the indazole ring of 3 by appropriately substituted pyrazoles maintained enzyme activity. Compounds were evaluated for inhibition of platelet aggregation and showed a general lipophilicity requirement. Aryl-substituted pyrazoles 32, 34, and 43 demonstrated potent activation of soluble guanylate cyclase and potent inhibition of platelet aggregation. Pharmacokinetic studies in rats showed that compound 32 exhibits modest oral bioavailability (12%). Furthermore 32 has an excellent selectivity profile notably showing no significant inhibition of phosphodiesterases or nitric oxide synthases.

Antitumor Imidazotetrazines. 35. New Synthetic Routes to the Antitumor Drug Temozolomide

Three new pathways to the antitumor drug temozolomide (4) have been explored via intermediates 3, 6, and 7. The key intermediate 5-amino-1-(N-methylcarbamoyl)imidazole-4-carboxamide (6) has been successfully converted to 4 in 45% yield by employing sodium nitrite in aqueous tartaric acid at 0-5 degrees C. Compound 6 is prepared from nitrophenyl carbamate 14a and methylamine or directly from 5-aminoimidazole-4-carboxamide (13) and either methyl isocyanate or N-methylcarbamoyl chloride. Temozolomide (4) is also prepared from 8-cyano-3-methylimidazo[5,1-d]-1,2,3,5-tetrazin-4(3H)-one (7) by hydrolysis to the hydrochloride salt of 4 in 10 M hydrochloric acid. Compound 7is prepared from either 5-diazoimidazole-4-carbonitrile (28) and methyl isocyanate or by diazotization of 5-amino-1-(N-methylcarbamoyl)imidazole-4-carbonitrile (25). Attempts to cyclize 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide (3) with phosgene or phosgene equivalents were unsuccessful: only 2-azahypoxanthine (11) was isolated.

Photodegradation of benzydamine: phototoxicity of an isolated photoproduct on erythrocytes

Benzydamine hydrochloride (Tantum, 1) is a photoallergic and phototoxic anti-inflammatory and analgesic agent. This drug is photolabile under aerobic and anaerobic conditions. Irradiation of a methanol solution of benzydamine under oxygen or argon at 300 nm affords 5-hydroxybenzydamine (2) and 2-beta-dimethylaminopropyl-1-benzylindalolin-3-one (3) as the main isolated and spectroscopically identified photoproducts. A radical intermediate was evidenced by thiobarbituric acid that was used as a radical sonde, as well as by the dimerization of cysteine. Erythrocyte lysis photosensitized by 1, 2, and 3 was investigated.

Photoproducts of benzydamine and azapropazone: demonstration of their phototoxicity in vitro

Red blood cell lysis, photosensitized by the products of the aerobic photolysis of benzydamine (1) and azapropazone (4), was investigated. Irradiation of a methanol solution of 1 and 4 under oxygen produces the photoproducts 3-hydroxy-benzydamine, (2), 2-(3-dimethylaminopropyl)-1-benzylindazolin-3-one (3) and 3-dimethylamino-7-methyl-1,2,4-benzotriazine (5). The mechanism of the photodegradation of 1 was examined. Photoproducts 3 and 5 produce singlet oxygen as demonstrated by trapping with 2,5-dimethylfuran. The photohemolysis rate for the photoproducts 3 and 5 was enhanced by deuterium oxide and oxygen. No change was observed in the presence of reduced glutathione. The photohemolysis rate was low under anaerobic conditions.

Structural study of benzidamine salicylate in the solid state and in solution

The vibrational (IR and Raman) and 1H and 13C NMR spectra of the analgesic and anti-inflammatory benzidamine salicylate (Benzasal) have been examined, and the results are described. The crystal structure of this compound has been determined by X-ray diffraction. To assist in interpretation of the spectroscopic data, some measurements of benzidamine, benzidamine hydrochloride, and salicylic acid have also been made. The most important intermolecular interactions of benzidamine salicylate in the solid state are N(+)H...O(-)...-C hydrogen bonds involving both salicylate oxygen atoms (d = 2.658 A and 3.228 A). At least the stronger hydrogen bond remains in CDCl3 solution. Moreover, the strong intramolecular hydrogen bond O-H...O(-)...-C within the salicylate anion has also been observed in the solid state and in solution.