Novel potassium channel openers. Part 4: transformation of the 1,4-benzoxazine skeleton into 1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroquinoxaline, indoline, and 1,5-benzoxazepine

As part of a search for a new potassium channel opener, the 1,4-benzoxazine skeleton derived from the benzopyran skeleton of cromakalim, was transformed into other fused rings such as 1,4-benzothiazine, 1,2,3,4-tetrahydroquinoline, 1,2,3,4-tetrahydroquinoxaline, indoline, and 1,5-benzoxazepine. The 1,4-benzothiazine derivative displayed approximately 20 times more potent vasorelaxant activity than cromakalim.     

Anti-Candida albicans properties of novel benzoxazine analogues

We previously reported that azole 1,4-benzothiazine derivatives have appreciable anti-Candida activity. In this study, we synthesized 1,4-benzoxazine analogues and examined their possible antifungal activity to further analyze the structure-activity relationships. Results of in vitro and in vivo experiments showed that 1,4-benzoxazine analogues show appreciable antifungal activity. In particular, they have significant capability to cure mice systemically infected with a lethal challenge of Candida albicans, as indicated by increased survival time paralleling reduction of colony forming units. Moreover, 1,4-benzoxazine derivatives also showed immunomodulating activity, as indicated by a significant increase of interleukin-12 and interferon-gamma production by splenocytes and reinforcement of a T helper type 1 protective immune response to C. albicans. In conclusion, the results demonstrate that replacement of sulfur by oxygen may improve immune response against C. albicans infection.     

Design, synthesis, and preliminary biological evaluation of 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives

We synthesized a series of novel small molecules, 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives, by tandem reduction-oxirane opening of 2-nitroaroxymethyloxiranes in moderate or excellent yields. We investigated the effects of all of the compounds on HUVEC apoptosis and A549 cell growth. The results showed that 6,8-dichloro-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine was the most effective small molecule in promoting HUVEC apoptosis and inhibiting A549 cell proliferation, but 6-amino-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine could remarkably inhibit HUVEC apoptosis and might induce the formation of microvessel.     

1,4-benzothiazine analogues and apoptosis: structure-activity relationship

We have previously shown 1,4-benzothiazine (1,4-B) derivatives induce thymocyte apoptosis in vitro and thymus cell loss in vivo. Apoptosis is mediated through a complex of biochemical events including phosphatidylcholine specific-phospholipase C (PC-PLC) activation, acidic sphingomyelinase (aSMase) activation and ceramide generation, caspase-8 and caspase-3 activation. As preliminary analysis of the structure-activity relationship (SAR) suggested some structural features were responsible for apoptosis, we synthesised several derivatives and tested for apoptosis activity at equimolar concentrations. In particular, we synthesised analogues that differed in the nature of skeleton (1,4-benzothiazine, 1,4-benzoxazine and 1,2,3,4-tetrahydroquinoline) and in the nature of side chain (imidazole, benzimidazole or piperazine as azole substituent; presence, absence or transformation of alcoholic group). Results of apoptosis induction indicate that transforming the 1,4-benzothiazine skeleton into 1,2,3,4-tetrahydroquinoline does not result in significant change. Transformation into 1,4-benzoxazine decreased activity. Replacing imidazole at the side chain with different piperazines also decreased activity while replacing it with benzimidazole does not change apoptotic activity. Finally, removal of the alcoholic group by dehydration to olefin, or by transforming it into ether, increased activity. Moreover, in an attempt to analyse further the SAR characteristics that are responsible for 1,4-B-activated apoptosis we tested the effect on caspase-8,-9 and-3 activation. 1,4-B analogues activate caspases and the structural requirements correlate with those responsible for apoptosis induction.     

1,4-Benzothiazine and 1,4-benzoxazine imidazole derivatives with antifungal activity: a docking study

We have recently described the synthesis and antifungal activity of a series of 1,4-benzothiazine and 1,4-benzoxazine imidazole derivatives that mainly showed in vivo activity against a murine experimental model of candidiasis but that very often lacked in vitro activity. Here, we report a docking study of a representative set of our molecules in a 3D model of CYP51 of Candida albicans (CA-CYP51). The model was constructed on the basis of the sequence homology relationship with the recently reported crystal structure of the CYP51 of Mycobacterium tuberculosis (MT- CYP51).     

Inhibition of PrPSc formation in scrapie infected N2a cells by 5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine derivatives

Prion diseases are fatal, neurodegenerative diseases characterized by the structural conversion of the normal, cellular prion protein, PrP^C into an abnormally structured, aggregated and partially protease-resistant isoform, termed PrP^Sc. Although substantial research has been directed toward development of therapeutics targeting prions, there is still no curative treatment for the disease. Benzoxazines are bicyclic heterocyclic compounds possessing several pharmaceutically important properties, including neuroprotection and reactive oxygen species scavenging. In an effort to identify novel inhibitors of prion formation, several 5,7,8-trimethyl-1,4-benzoxazine derivatives were evaluated in vitro for their effectiveness on the expression levels of normal PrP^C and its conversion to the abnormal isoforms of PrP^Sc in a scrapie-infected cell culture model. The most potent compound was 2-(4-methoxyphenyl)-5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine, with a diminishing effect on the formation of PrP^Sc, thus establishing a class of compounds with a promising therapeutic use against prion diseases.     

Inhibition of PrPSc formation in scrapie infected N2a cells by 5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine derivatives

Prion diseases are fatal, neurodegenerative diseases characterized by the structural conversion of the normal, cellular prion protein, PrP^C into an abnormally structured, aggregated and partially protease-resistant isoform, termed PrP^Sc. Although substantial research has been directed toward development of therapeutics targeting prions, there is still no curative treatment for the disease. Benzoxazines are bicyclic heterocyclic compounds possessing several pharmaceutically important properties, including neuroprotection and reactive oxygen species scavenging. In an effort to identify novel inhibitors of prion formation, several 5,7,8-trimethyl-1,4-benzoxazine derivatives were evaluated in vitro for their effectiveness on the expression levels of normal PrP^C and its conversion to the abnormal isoforms of PrP^Sc in a scrapie-infected cell culture model. The most potent compound was 2-(4-methoxyphenyl)-5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine, with a diminishing effect on the formation of PrP^Sc, thus establishing a class of compounds with a promising therapeutic use against prion diseases.     

Synthesis and SAR studies of 1,4-benzoxazine MenB inhibitors: Novel antibacterial agents against Mycobacterium tuberculosis

Menaquinone is an essential component of the electron transport chain in many pathogens and consequently enzymes in the menaquinone biosynthesis pathway are potential drug targets for the development of novel antibacterial agents. In order to identify leads that target MenB, the 1,4-dihydroxy-2-naphthoyl-CoA synthase from Mycobacterium tuberculosis, a high-throughput screen was performed. Several 1,4-benzoxazines were identified in this screen and subsequent SAR studies resulted in the discovery of compounds with excellent antibacterial activity against M. tuberculosis H37Rv with MIC values as low as 0.6 μg/ml. The 1,4-benzoxazine scaffold is thus a promising foundation for the development of antitubercular agents.     

Design, synthesis and vasorelaxant evaluation of novel coumarin-pyrimidine hybrids

The main objective of the present work depends on the hybridization of coumarin moiety as a vasorelaxant scaffold and pyrimidine ring with known potential cardiovascular activity in order to prepare some new potent antihypertensive candidates. Hence, two groups of pyrimidinyl coumarin derivatives were synthesized and evaluated for their vasorelaxing activity. These compounds were prepared via two routes; either preparation of the guanidinocoumarin 4 followed by a cocktail of cyclization reactions to yield a different array of 6-(substituted pyrimidin-2-yl)aminocoumarins 5-17, or through cyclization of the precursor chalcones 22a-g with guanidine hydrochloride to generate the corresponding final compounds, 8-(6-aryl-2-aminopyrimidin-4-yl)-7-methoxycoumarins 23a-g. The effect of these compounds and the coumarin intermediates 3, 4, 21 and 22a-g on nor-epinephrine induced contracture in thoracic rat aortic rings was investigated using prazocin as reference drug. Several derivatives showed promising activities either equal or even better than that of prazocin (IC(50) 0.487 mM). The most prospective compounds; the pyrimidinylamino coumarin derivatives 8, 17 (IC(50) 0.411, IC(50) 0.421 mM) and the chalcones 22b, 22e (IC(50) 0.371, 0.374 mM) that displayed the highest activity can be a base for lead optimization and simple but efficient design of new compounds. 2D-QSAR analysis was applied to find a correlation between the experimental vasorelaxant activities of the newly synthesized coumarin derivatives and their different physicochemical parameters. The result of this study showed that the increase in aqueous solubility while retaining good hydrophobic character of the overall molecule is the key for maintaining high relaxation activity.     

Synthesis and cytotoxicity evaluation of 2-amino- and 2-hidroxy-3-ethoxycarbonyl-N-substituted-benzo[f]indole-4,9-dione derivatives

Reaction between 2,3-dichloronaphthoquinone (I) and ethyl cyanoacetate or diethyl malonate under different conditions gave the starting materials, 2-chloro-3-(alpha-cyano-alpha-ethoxycarbonyl-methyl)-1,4-naphthoquinone (A) or 2-chloro-3-(diethoxycarbonyl-methyl)-1,4-naphthoquinone (B). The 2-amino-3-ethoxycarbonyl-N-substituted-benzo[f]indole-4,9-dione derivatives [A-(1-10)] and 2-hydroxy-3-ethoxycarbonyl-N-substituted-benzo[f]indole-4,9-dione derivatives [B-(1-12)] were prepared from compounds A and B, respectively, by using various alkyl-, and arylamines. The cytotoxic activities of the prepared compounds were evaluated by SRB (Sulforhodamine B) assay against the following tumor cell lines: A459 (human lung), SK-OV-3 (human ovarian), SK-MEL-2 (human melanoma), XF498 (human CNS), and HCT 15 (human colon). Many of the derivatives mentioned exhibited more potent cytotoxic effects against SK-OV-3 and XF498 than etoposide. Significantly, 2-amino-3-ethoxycarbonyl-N-(3-methyl-phenyl)-benzo[f]indole-4,9-dione (A-8) showed potent activity against all tumor cell lines, and in particular, its cytotoxic effect against SK-OV-3 was much higher than doxorubicin.     

Vasorelaxant activity of 2-fluoromethylbenzopyran K channel openers

Synthesis and vasorelaxant activity of 2-fluoromethylbenzopyrans are explained. These 2-fluoromethyl derivatives showed a potent smooth muscle relaxant activity.     

Discovery of a new insecticide lead by optimizing a target-diverse scaffold: tetrazolinone derivatives

In order to discover lead compounds with novel action mechanism, a series of tetrazolinone derivatives bearing structurally diverse substituents, 1-aryl-4-substituted-1,4-di-hydro-5H-tetrazol-5-ones 2, 1-((5-(alkylthio)-1,3,4-oxadiazol-2-yl)methyl)-4-(substituted)- phenyl-1H-tetrazol-5(4H)-ones 5, and 1-((5-(alkylthio)-1,3,4-thiadiazol-2-yl)methyl)-4- (substituted)phenyl-1H-tetrazol-5(4H)-ones 7, were designed and synthesized in good yields by a multiple-step synthetic procedure. The results of greenhouse in vivo test indicated that all the target compounds did not displayed herbicidal activity, however, some of them exhibited excellent in vivo insecticidal activity against Tetranychus cinnabarinus at the concentration of 250 mg L-1. To our knowledge, this is the first report about the insecticidal activity of tetrazolinone derivatives, which indicated that the tetrazolinone scaffold could be identified as a novel insecticidal lead structure. The present work demonstrated that optimizing a target-diverse scaffold is an effective way to discover new lead compounds with new action mechanism or biological activity.     

Novel benzodiazepines derivatives as analgesic modulating for Transient receptor potential vanilloid 1

A new series of derivatives of 3-(7-chloro-5-(2-fluorophenyl)-2-oxo-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)propanoic acid were designed and synthesized as analgesic modulating for Transient receptor potential vanilloid 1. They were investigated for TRPV1 antagonistic activity in vitro, analgesic activity and sedative activity in vivo and aqueous solubility. Preliminary studies identified 3-(7-chloro-5-(2-fluorophenyl)-2-oxo-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)-N,N-dimethylpropanamide(Compound 11), as a potent analgesic modulating for TRPV1 with potent activity and good aqueous solubility.     

Microbial transformation of 8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine by fungi.

The microbial transformation of 8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine (compound I) was undertaken to obtain new derivatives. Compound I was transformed by Hormodendrum sp. (NRRL 8133) to 8-chloro-10,11-dihydrodibenz(b,f)(1,4)oxazepine-11-one (compound II) and 2-(2-amino-4-chlorophenoxy)benzyl alcohol (compound IV). Microbial cleavage of the nonaromatic ring to form compound IV was accomplished by several other fungi. Compound I was transformed to 8-chlorodibenz(b,f)(1,4)oxazepine (compound III) by Hormodendrum cladosporioides (NRRL 8132).     

Vasorelaxant activity of 2-substituted 6-nitro-2H-1-benzopyran-4-carbothioamide K channel openers

Synthesis and vasorelaxant activity of 2-substituted 6-nitro-2H-1-benzopyran-4-carbothioamides 5 are described. Potent smooth muscle relaxant activity was displayed by 5c, 5h, and 5i.     

Relaxant activity of 2-(substituted phenyl)-1H-benzimidazoles on isolated rat aortic rings: design and synthesis of 5-nitro derivatives

The relaxant activity of 2-(o, p-substituted phenyl)-1H-benzimidazole derivatives with various 5- and 6-position substituents (-H, -CH3, -NO2, -CF3), namely 1-7, was recorded using the in vitro rat aorta ring test. Compounds 3 and 6 [2-(5-nitro-1H-benzimidazol-2-yl)phenol and 2-(4-methoxyphenyl)-5-nitro-1H-benzimidazole] were prepared using a short route, and were the most potent compounds of the series, showing IC50 value of 0.95 and 1.41 (with endothelium) and 2.01 and 3.61 microM (without endothelium), respectively. Studying further structure-activity relationships through the use of bioisosteric substitution in these benzimidazole derivatives should provide novel vasorelaxant leads and possibly against hypertensive diseases.     

Synthesis and pharmacological evaluation of 4H-1,4-benzothiazine-2-carbonitrile 1,1-dioxide and N-(2-cyanomethylsulfonylphenyl)acylamide derivatives as potential activators of ATP sensitive potassium channels

1,2,4-Thiadiazine derivatives, like 3-methyl-7-chlorobenzo-4H-1,2,4-thiadiazine 1,1-dioxide, diazoxide and 7-chloro-3-isopropylamino-4H-benzo-1,2,4-thiadiazine 1,1-dioxide, BPDZ 73, are potent openers of Kir6.2/SUR1 K(ATP) channels. To explore the structure-activity relationship of this series of K(ATP) openers, 4H-1,4-benzothiazine-2-carbonitrile 1,1-dioxide and N-(2-cyanomethylsulfonylphenyl)acylamide derivatives were synthesized from 2-acetylamino-5-chloro-benzenesulfonic acid pyridinium salt or 2-aminobenzenethiols. The 4H-1,4-benzothiazine-2-carbonitrile 1,1-dioxide derivatives (e.g., 7-chloro-3-isopropylamino-4H-1,4-benzothiazine-2-carbonitrile 1,1-dioxide, 3f) were found to activate K(ATP) channels as indicated by their ability to hyperpolarize beta cell membrane potential, to inhibit glucose-stimulated insulin release in vitro and to increase ion currents through Kir6.2/SUR1 channel as measured by patch clamp. The potency and efficacy of, for example, 3f is however significantly reduced compared to the corresponding 4H-1,2,4-benzothiadiazine 1,1-dioxide derivatives. Opening of the 4H-1,2,4-thiadiazine ring to get (e.g., 2-cyanomethylsulfonyl-4-fluorophenyl) carbamic acid isopropyl ester (4c) gives rise to compounds, which are able to open K(ATP) channels but with considerable reduced potency compared to, for example, diazoxide. Compound 3a, 7-chloro-3-methyl-4H-1,4-benzothiazine-2-carbonitrile 1,1-dioxide, which inhibits insulin release in vitro from beta cells and rat islets, reduces plasma insulin levels and blood pressure in anaesthetized rats upon intravenous administration.     

Synthesis and hypoxic-cytotoxic activity of some 3-amino-1,2,4-benzotriazine-1,4-dioxide derivatives

A series of 3-amino-1,2,4-benzotriazine-1,4-dioxide derivatives 1 have been synthesized and evaluated for their cytotoxic activity in vitro against human leukemia cell lines: Molt-4, K562, HL60, human liver cancer cell Hep-G2, human prostate cancer cell PC-3 in hypoxia. Most of the compounds showed more potent activity than TPZ. Compounds 1i and 1m displayed encouraging superior activity against Molt-4 and HL-60 cell lines. Three potential derivatives received the test of the activity in hypoxia and in normoxia against Molt-4 and HL-60 cell lines and showed obvious hypoxia selectivity. Further mechanism study revealed that the cytotoxic activities of compounds 1i and 1k in Molt-4 cells might be mediated by modulation of p53 protein expression and mitochondrial membrane potential (DeltaPsi(m)).     

Distinct patterns of autophagy evoked by two benzoxazine derivatives in vascular endothelial cells

Macroautophagy (referred to as autophagy) is an evolutionarily conserved, bulk-destruction process in eukaryotes. During this process, the cytoplasm containing long-lived proteins and organelles is engulfed into double-membrane autophagosomes, and ultimately undergoes enzymatic degradation within lysosomes. Autophagy serves as a prosurvival machinery, or it may contribute to cell death. Accumulating evidence indicates that autophagy is involved in the pathogenesis and intervention of various human diseases. Pharmacological autophagy modulators are arousing interest from biologists and clinical physicians in light of their potential for disease therapy and increasing our understanding of the mechanism of autophagy. In this study, we identified two autophagy enhancers, 6-amino-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine (ABO) and 6,8-dichloro-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine (DBO), in human umbilical vein endothelial cells (HUVEC s) by autophagy assays, and demonstrate that ABO and DBO could stimulate autophagy in an mtor-independent and mtor-dependent manner, respectively; ABO-stimulated autophagy was attributed to the elevation of the Ca2+ channel annexin A7 (ANXA7), whereas DBO's effect was due to the level of intracellular reactive oxygen species (ROS). Importantly, we found that ANXA7 was essential for autophagy induction via modulating the intracellular calcium concentration ([Ca2+]i) in HUVEC s. In summary, our work introduced two distinct autophagy enhancers and highlighted the critical role of ANXA7 in endothelial autophagy.