The tetracyclic indolo[3,2-b]quinoline ring system constitutes an important structural moiety in natural products exhibiting numerous biological activities. In particular, indolo [3, 2-b]quinoline, commonly known as linear quindo-line is of particular interest, because of its rigid structure and scope of derivatization. Although the core linear quindoline skeleton shows little or no activity in several biological systems, introduction of a methyl group on the N-5 atom leading to cryptolepine induces remarkable activity against a broad spectrum of biological targets. A number of analogs of quindoline and cryptolepine have been synthesized, incorporating various functional groups on the core quindoline skeleton leading to improved biological activities. In this review, we describe various synthetic methodologies leading to the quindoline scaffold, the biological activities and the structure activity relationships (SAR) of quindoline derivatives toward different disease states to give a better picture of the importance of this moiety in medicinal chemistry.
Cryptolepine; indoloquinolines; synthesis; structure-activity relationship (SAR) studies
The synthesis and evaluation of several benzothiazole based compounds are described in an attempt to identify novel dual-acting 5HT1A receptor and SERT inhibitors as new antidepressants. Binding affinities at the 5HT1A receptor and the serotonin transporter do not appear to be congruent and other areas of the binding sites would need to be explored in order to improve binding simultaneously at both sites. Compounds 20 and 23 show moderate binding affinity at the 5HT1A receptor and the SERT site and thus, have the potential to be further explored as dual-acting agents. In addition, compound 20 binds with low affinity to the dopamine transporter (DAT), the norepinephrine transporter (NET) and 5HT2C receptor, which are desirable properties as selectivity for SERT (and not DAT or NET) is associated with an absence of cardiovascular side-effects.
Benzothiazoles; SERT inhibition; 5HT1A binding; dual-acting antidepressants; 5HT1A agents; potential SERT inhibitors
Structure–activity relationship studies on 4-(4-(4-chlorophenyl)-1,4-diazepan-1-yl)-1-(4-fluorophenyl) butan-1-one (SYA 013), a homopiperazine analog of haloperidol has resulted in an understanding of the effect of structural modifications on binding affinity at dopamine and serotonin receptor subtypes. Further exploration, using bioisosteric replacement strategies has led to the identification of several new agents including compounds 7, 8, 11 and 12 which satisfy the initial criteria for further exploration as new antipsychotic agents. In addition, compound 18, a D3 selective tropanol, has been identified as having the potential for further optimization into a useful drug which may combat neuropsychiatric diseases.
Antipsychotics; Haloperidol analogs; Structure–activity relationship studies; Atypical antipsychotics; Homopiperazine; Benzothiazole
Previous studies have indicated that the δ-carboline (2) ring system derived from the natural product cryptolepine (1) may represent a pharmacophore for anti-infective activity. This paper describes the design and synthesis of a small library of substituted δ-carbolines and the evaluation of the antifungal and antibacterial activities. An evaluation of the anti-bacterial activity of a previously reported library of ring-opened analogs was also conducted to provide an opportunity to test the hypothesis that both group of compounds may have the same biological target. Results indicate that against a selected group of fungal pathogens, substituted δ-carbolinium analogs displayed higher potency and several fold lower cytotoxicity than cryptolepine the parent natural product. Both the δ-carbolinium compounds and their ring-opened analogs, exhibited equally high anti-bacterial activity against the selected pathogens and especially against the gram positive bacteria evaluated.
δ-carboline; antifungal; antibacterial; opportunistic; synthesis; quaternary
In addition to other receptors, including sphingosine-1-phosphate receptor 1, cannabinoid receptor 2 positions mouse marginal zone B cells within the marginal zone and also prevents their loss to the blood.
Specialized B cells residing in the splenic marginal zone (MZ) continuously survey the blood for antigens and are important for immunity to systemic infections. However, the cues that uniquely attract cells to the MZ have not been defined. Previous work demonstrated that mice deficient in cannabinoid receptor 2 (CB2) have decreased numbers of MZ B cells but it has been unclear whether CB2 regulates MZ B cell development or positioning. We show that MZ B cells are highly responsive to the CB2 ligand 2-arachidonylglycerol (2-AG) and that CB2 antagonism rapidly displaces small numbers of MZ B cells to the blood. Antagonism for longer durations depletes MZ B cells from the spleen. In mice deficient in sphingosine-1-phosphate receptor function, CB2 antagonism causes MZ B cell displacement into follicles. Moreover, CB2 overexpression is sufficient to position B cells to the splenic MZ. These findings establish a role for CB2 in guiding B cells to the MZ and in preventing their loss to the blood. As a consequence of their MZ B cell deficiency, CB2-deficient mice have reduced numbers of CD1d-high B cells. We show that CB2 deficiency results in diminished humoral responses to a CD1d-restricted systemic antigen.
Previous studies on the indoloquinoline alkaloid, cryptolepine (2), revealed that it has antiinfective properties among other activities. Using Structure Activity Relationship (SAR) techniques, several ring-opened analogs of cryptolepine (3-phenylaminopyridinium and 3-phenylaminoquinolinium derivatives) were designed to improve the potency and lower the cytotoxicity shown by several of the precursor agents. Results indicate that these ring-opened analogs constitute new anti-infective agents with over a 100-fold potency and several fold lower cytotoxicity than cryptolepine from which they are derived.
Substitution around 5-methyl benzothieno[3,2-b]quinolinium (2) ring system was explored in order to identify positions of substitution that could improve its antifungal profile. The 3-methoxy (10b) was active against C. albicans, C. neoformans and A. fumigatus and the 4-chloro (10f) analog showed moderate increases in anti-cryptococcal and anti-aspergillus activities. The effectiveness of 10b and 10f were validated in murine models of candidiasis and cryptococcosis respectively. The efficacy of 10f in reducing brain cryptococcal infection and its observation in the brain of mice injected with this quaternary compound confirm the capacity of these compounds to cross the blood-brain barrier of mice. Overall, several of the chloro and methoxy substituted compounds showed significant improvements in activity against A. fumigatus, the fungal pathogen prevalent in patients receiving organ transplant. Opening the benzothiophene ring of 2 to form 1-(5-cyclohexylpentyl)-3-(phenylthio)quinolinium compound (3) resulted in the identification of several novel compounds with over 50-fold increases in potency (cf 2) while retaining low cytotoxicities. Thus, compound 3 constitutes a new scaffold for development of drugs against opportunistic infections.
The title compounds, 2-chloroanilinium dihydrogen phosphate (2CADHP) and 4-chloroanilinium dihydrogen phosphate (4CADHP), both C6H7NCl+·H2PO4
−, form two-dimensional supramolecular organic–inorganic hybrid frameworks. In 2CADHP, the dihydrogen phosphate anions form a double-stranded anionic chain generated parallel to the  direction through O—H⋯O hydrogen bonds, whereas in 4CADHP they form a two-dimensional supramolecular net extending parallel to the crystallographic (001) plane into which the cations are linked through strong N—H⋯O hydrogen bonds.
In the title compound, C20H27N3O4, both cyclohexane rings adopt chair conformations. The benzene ring and the amide group are oriented at a dihedral angle of 62.1 (2)°. In the crystal structure, intermolecular N—H⋯O and C—H⋯O hydrogen bonds link the molecules into chains propagating in , which contain R
2(12) ring motifs.
In the title compound, C28H38N2O3, the central ring of the acridinedione system adopts a boat conformation, while one of the outer rings adopts a half-chair conformation and the conformation of the other outer ring is between a sofa and a half-chair. The acridinedione system is buckled, with an angle of 22.01 (3)°. The crystal packing comprises layers of molecules laid parallel to the ac plane, being reinforced by an intermolecular C—H⋯O interaction.
Fas (CD95, APO-1, TNFRSF6) is a TNF receptor superfamily member that directly triggers apoptosis and contributes to the maintenance of lymphocyte homeostasis and prevention of autoimmunity. Although FADD and caspase-8 have been identified as key intracellular mediators of Fas signaling, it is not clear how recruitment of these proteins to the Fas death domain leads to activation of caspase-8 in the receptor signaling complex. We have used high-resolution confocal microscopy and live cell imaging to study the sequelae of early events in Fas signaling. These studies have revealed a new stage of Fas signaling in which receptor ligation leads to the formation of surface receptor oligomers that we term signaling protein oligomerization transduction structures (SPOTS). Formation of SPOTS depends on the presence of an intact Fas death domain and FADD but is independent of caspase activity. Analysis of cells expressing Fas mutations from patients with the autoimmune lymphoproliferative syndrome (ALPS) reveals that formation of SPOTS can be disrupted by distinct mechanisms in ALPS.