Structural and spectroscopic studies on 2-pyranones.

Experimental methods of infrared, Raman and electronic absorption spectroscopy and DFT calculations using B3LYP functionals and 6-31G** and 6-311++G** basis sets have been used to understand the structural and spectral characteristics of 2-pyranones, 6-phenyl-4-methylsulfanyl-2-oxo-2H-pyran and 6-phenyl-4-methylsulfanyl-2-oxo-2H-pyran-3-carbonitrile in the electronic ground (S(0)) and first excited (S(1)) states. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). Based on TD-DFT calculations using 6-31+G**5D basis set, an assignment of absorption peaks in the UV-VIS region has been suggested. The S(1) state is found to be a (1)(pi,pi*) state. A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra and calculated frequency and intensity of the vibrational bands and potential energy distribution over the internal coordinates. Characteristic vibrational bands of the 2-pyranone ring and methylsulfanyl and carbonyl groups have been identified.

Carbanion-induced base-catalyzed synthesis of 1H-isothiochromenes, benzo[c]thiochromenes through ring-transformation reactions of 6-aryl-2H-pyran-2-ones.

An innovative approach to the one-pot synthesis of highly functionalized 3,4-dihydro-1H-isothiochromenes (3), 6H-benzo[c]thiochromenes (5, 6), 6H-benzo[c]chromenes (8), and 2,3-dihydro-1-benzothiophenes (10, 11) is delineated from the reaction of a suitably functionalized 6-aryl-3-carbomethoxy-4-methylthio-2H-pyran-2-one (1) and a carbanion generated from tetrahydrothiopyran-4-one, 4-thiochromanone, 4-chromanone, and tetrahydrothiophene-3-one through ring-transformation reactions.

Natural products of plant origin as anticancer agents.

Natural products have been used as effective remedies for the treatment of various ailments. Numerous plant products in the form of decoction, tincture, tablets and capsules have been clinically used for the treatment of different kinds of cancer. This review covers some of the important plants with clinically proven anticancer activity, including Catharanthus roseus, Podophyllum peltatum, Taxus brevifolia, Camptothecin acuminata, Cephalotaxus harringtonia, Viscum album, Onchrosia elliptica, Annona bullata, Asmina triloba and Rhizoma zedoariae. Synthetic analogues in some cases have also been prepared to improve the efficacy and decrease the side effects of parent compounds. The modes of action of clinically used drugs are also delineated.

Herbal preparations as a source of hepatoprotective agents.

Mono- and polyherbal preparations with potent antihepatotoxic activity in various liver disorders, made from traditionally used herbs with proven efficacy, have been described. More than 700 mono- and polyherbal preparations in the form of decoction, tincture, tablets and capsules from more than 100 plants are in clinical use. Some of the herbs--such as Silybum marianum, Picrorhiza kurroa, Andrographis paniculata and Glycyrrhizae radix--are very common in most of the polyherbal preparations. This review covers the preparations of widely used herbs such as S. marianum, Schisandra chinensis, Phyllanthus amarus, P. kurroa, A. paniculata, G. radix, Lycium chinense and Cochlospermum tinctorium as hepatoprotectants and includes the mode of action of these preparations. Some polyherbal preparations such as Livex, HD-03, Hepatomed and Hepatoguard with proven efficacy are also described in this review.

Oxygenated chalcones and bischalcones as potential antimalarial agents.

Oxygenated chalcones (3a,b) and bischalcones (4a-j) have been synthesized and evaluated for antimalarial activity against chloroquine sensitive and resistant strains of Plasmodium berghei in mice. Some of the screened compounds, 3a, 4c, 4e, 4f and 4i, have shown significant activity at 100 mg/kg dose against sensitive strain.

Suitably functionalised pyrimidines as potential antimycotic agents.

Various suitably functionalized pyrimidine derivatives have been synthesized to explore their potential as antimycotic agents. Some of the synthesized compounds 4c, 4d, 8a-e have shown highly significant in vitro antifungal activity against five human pathogenic fungi.

A highly functionalized ferrocenylpyrazolo[2,3-a]pyridine.

The crystal structure of [2-(4-bromophenyl)-4-cyano-5-ferrocenylpyrazolo[2,3-a]pyridin-7-yl]acetonitrile, C(26)H(17)N(4)FeBr or [Fe(C(5)H(5))(C(21)H(12)BrN(4))], shows that the pyrazolopyridine ring system (PP), the bromophenyl ring (BP) and the cyclopentadiene ring (Cp) are nearly planar. The PP ring system is twisted out of the plane of the BP and Cp rings by about 20 degrees.

Present status of hepatoprotectants.

Perpetual exposure of liver to xenobiotics and therapeutic agents leads to toxic manifestations of a complex and diverse nature. Not a single curative therapeutic agent has been found so far which could provide lasting remedy to patients suffering from hepatic disorders. In fact, the remedies available in the modern system of medicine provide only symptomatic relief without any significant changes on the disease process. Moreover, their use is associated with severe side effects and chances of relapses. Except some natural products claimed to be effective, no safe synthetic product is yet available for the management of hepatic disorders. Lack of effective, least toxic and curative hepatoprotectants made the task difficult to discover newer drugs. This review is an attempt to provide an overall view of the development of synthetic and natural products as hepatoprotective agents.

Past and present scenario of hepatoprotectants.

The liver plays a significant role not only in metabolism and disposition of the chemicals to which it is exposed directly or indirectly but also plays a pivotal role in the metabolism of fats, carbohydrates, proteins and immunomodulations. The impairment of liver generally results from viral or portozoal infections, excessive use of alcohol, drugs and xenobiotics. This review provides an overall view about the past and present status of the hepatoprotectants resulted from synthetic and plant origins.

Functionalized 1,3-teraryls as a new class of hepatoprotectants. Part V.

Functionalized 1,3-teraryls, synthesized through ring transformation of 6-aryl-3-carbomethoxy-4-methylthio-2H-pyran-2-one from arylketone have been screened for their hepatoprotective activity and of them have demonstrated significant protection in animal model.

Chemotherapeutic agents, XXI: Synthesis of Pi-deficient pyrimidines as leishmanicides.

Synthesis of 5-cyano-6-(3-pyridyl)-2-thiouracil (1) has been described from 3-pyridinecarboxaldehyde, thiourea, and ethyl cyanoacetate. Alkylation of 1 with mono- and dihaloalkanes under different conditions, provided 2a,b, 3a,b, and 4a-i. Halogenation of 4g with POCl3 yielded 5 which underwent nucleophilic substitution with amines to give 6a-g. Fusion of 4a with aromatic and heterocyclic amines at 160 degrees C gave the substitution products 7a-c. Some of the compounds were screened for antileishmanial activity but only one of them (6d) demonstrated very significant activity.

Chemotherapeutic agents, XVIII: Synthesis of pi-deficient pyrimidines and fused pyrimidines as leishmanicidal agents.

Synthesis of 6-aryl-5-cyano-2-thiouracils 1a-d from the condensation-cyclization of an aromatic aldehyde, thiourea and ethyl cyanoacetate has been described. Alkylation of 1a-d under different reaction conditions with mono- and dihalo-alkanes yielded 2, 3, and 6. Interaction of 1 with POCl3 provided halopyrimidines 8a,b. Nucleophilic substitution on 8 and 3 with aromatic amines gave 9a-d and 7a-d respectively. 6-Chloro-5-nitro-3-methyluracil (11) obtained by nitration of 10 underwent nucleophilic substitution with amines providing 12. Some of the compounds screened as leishmanicides did not exhibit any significant activity.

Synthesis and structural requirements of N-substituted norapomorphines for affinity and activity at dopamine D-1, D-2, and agonist receptor sites in rat brain.

A series of N-substituted analogues of (R)-(-)-norapomorphine were synthesized to study the optimal structural requirements of the N-alkyl side chain to interact with D-1 and D-2 dopaminergic receptors as well as dopamine (DA) agonist binding sites. Evaluations included testing the affinity of these compounds for DA receptor sites in rat striatal tissue and assessing stereotypy as a behavioral index of dopaminergic activity. The electronic, steric, and lipophilic properties of the N-alkyl side chain were found to be related to affinity, D-2 selectivity, and dopaminergic activity. All 11 compounds evaluated had relatively low affinity at D-1 sites. Optimum D-2 and agonist-site affinity as well as agonist activity were exhibited by N-cyclopropylmethyl (7) greater than or equal to N-allyl (8) greater than or equal to N-propyl (4) or N-ethyl (3) substituted compounds. Branching of the N-alkyl side chain as in N-isopropyl (5) and N-isobutyl (6) markedly reduced the D-2 affinity and activity, presumably due to steric effects. The N-trifluoroethyl (10) and N-pentafluoropropyl (11) derivatives had low affinity for all their dopamine receptor sites and no agonistic activity; evidently, the highly electronegative F atoms decrease basicity of the N atom and therefore decrease the ability of the N atom to be cationic at physiological pH, a proposed requirement for high-affinity binding to DA receptors.

Chemotherapeutic agents, XV. Synthesis of 4-amino-3-pyrazolo-1,2,4-triazoles as antimicrobial agents.

4-Amino-3-hydrazino-5-H/methyl-1,2,4-triazole dihydrochlorides (2a,b) were obtained by cyclization of triamino-guanidine-HCl in formic and acetic acids, respectively. Condensation of 2a with pyrazol-4-carbaldehydes in ethanol yielded 3a,b. Cyclocondensation of 2a,b with dimethylmercaptocyanoacrylonitrile, methyl dimethylmercapto-cyanoacrylate, ethoxymethylenemalononitrile and ethyl ethoxymethylenecyanoacetate individually provided 4a-d and 5a-d, respectively. The hydrazones 6a,b were obtained by refluxing 4-amino-3-(5-amino-4-ethoxycarbonyl pyrazol-1-yl)-1,2,4-triazole (5b) with aryl aldehydes in ethanol. Interaction of 2a with acetylacetone and 2-ethoxycarbonylcyclopentanone separately yielded 7 and 8 while reaction with 2-ethoxycarbonylcyclohexanone provided the bicyclic compounds 9a,b. Some of the compounds were screened for antibacterial and antifungal activities but none of them showed any significant activity.

S(+)methylenedioxy-N-n-propylnoraporphine: an orally active inhibitor of dopamine selective for rat limbic system.

The 10-11-methylenedioxy (MDO) derivative of S(+)N-n-propylnorapomorphine (NPA) was prepared and tested as a possible active prodrug to S(+)NPA, which we have recently found to exert in vivo activity suggestive of selective antagonism of dopamine receptors in the limbic forebrain but not the extrapyramidal basal ganglia. Like S(+)NPA, S(+)MDO-NPA inhibited the behavioral arousal induced by dopamine injected into nucleus accumbens of the rat, but not the head-turning response to dopamine injected into the corpus striatum. However, only MDO-NPA was orally active and it was somewhat longer-acting than NPA. The activity of S(+)MDO-NPA was prevented by pretreatment with the oxidase inhibitor SKF-525A. These properties are analogous to those of R(-)MDO-NPA, which we had previously reported as an orally active prodrug of the dopamine agonist R(-)NPA. Thus the methylenedioxy derivatives of the two entantiomers of NPA have properties desirable in a potentially clinically useful dopamine agonist and limbic dopamine antagonist, respectively.

Effects of N-substituted phenyltetrahydropyridines on cerebral high-affinity synaptosomal uptake of dopamine and other monoamines in several mammalian species.

Effects of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (N-methyl-PTP) and its N-propyl congener (N-propyl-PTP) on the high-affinity uptake of tritiated dopamine (DA), norepinephrine, and serotonin by striatal or cerebral cortical synaptosomes were evaluated in several species (rat, guinea pig, rabbit, calf, and man). Both compounds inhibited uptake of 0.1 microM labeled amines at IC50s of 5-10 microM. Effects of N-methyl-PTP were competitive, reversible, somewhat more potent, and more selective for serotonin than were actions of N-propyl-PTP. Similar effects were found in all species. Neither agent inhibited binding of 3H-labeled spiperone or ADTN to DA receptor sites. 3H-N-methyl-PTP did not appear to be taken up selectively into DA neurons. N-methyl-PTP was highly toxic to the rat in doses that did not alter the metabolism of DA or serotonin in brain. These results, overall, do not provide strong support for the hypothesis that reported neurotoxic actions of N-methyl-PTP are mediated by neuron-specific local transport and intracellular accumulation, or account for species differences in the actions of this toxin, but do suggest interactions with brain monoamine neurons. The actions of the neurotoxic effects of N-methyl-PTP remain unclear.

Comparative assessment of dopamine agonist aporphines as anticonvulsants in two models of reflex epilepsy.

The anticonvulsant action of various aporphine derivatives that act on dopamine receptors has been investigated in two genetically determined animal models--DBA/2 mice with sound-induced seizures and baboons Papio papio with photically-induced seizures. Protection against the clonic and tonic phases of the seizures response in DBA/2 mice was seen for 15-60 min after (-)2,10,11-trihydroxy-N-n-propylnoraporphine (1.25 mg/kg) and (-)10,11-methyl-enedioxy-N-n-propylnoraporphine (0.625-1.25 mg/kg) and for 30-60 min after (-)2,10,11-trihydroxyaporphine (31.25 mg/kg). Short-lasting protection (up to 30 min) was seen following (-)2,10,11-trihydroxy-N-ethyl-noraporphine (1.25-6.25 mg/kg). Changes in audiogenic seizure susceptibility were accompanied by piloerection, ptosis and loss of spontaneous locomotor and exploratory behaviour. No protection was seen after (-)norapomorphine (0.05-18.75 mg/kg). All the compounds (including norapomorphine) significantly lowered rectal temperature, although the time course of this effect was often longer than that of protection against audiogenic seizures. In baboons, marked reductions in photomyoclonic responses were seen following (-)10,11-methylenedioxy-N-n-propylnoraporphine (0.25 mg/kg, lasting up to 2h); (-)2,10,11-trihydroxy-N-n-propylnoraporphine (0.5-2.5 mg/kg, lasting up to 7 h); (-)2,10,11-trihydroxyaporphine (5 mg/kg, duration of action 1-4 h) and (-)2,10,11-trihydroxy-N-ethylnoraporphine (6.25 mg/kg, lasting 2 h). Little change in responsiveness followed administration of (-)norapomorphine 1.25 or 6.25 mg/kg. Changes in photosensitivity were accompanied by yawning and pupil dilatation. (-)10,11-Methylenedioxy-N-n-propylnoraporphine (0.5-6.25 mg/kg) was also administered orally in baboons.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral effects of (-)10,11-methylenedioxy-N-n-propylnoraporphine, an orally effective long-acting agent active at central dopamine receptors, and analogous aporphines.

Substituted and unsubstituted 10,11-methylenedioxy derivatives of apomorphine (APO) or its N-propyl congener (NPA) were synthesized and evaluated for their ability to alter motor activity or to induce stereotyped behavior in the rat. Of these, (-)10,11-methylenedioxy-N-n-propylnoraporphine hydrochloride (MDO-NPA) was the most active, and the only compound which was found to be active after oral administration. Also, MDO-NPA was more potent than NPA or APO in producing stereotypy, but large doses of these three aporphines were equipotent in stimulating motor activity. The duration of action of MDO-NPA exceeded that of NPA and APO, and increased with increasing doses. The effects of MDO-NPA on general activity were biphasic: larger doses stimulated activity: smaller doses markedly inhibited it and induced catalepsy. Catalepsy did not occur with NPA or APO and their motor-inhibitory effects were apparent only in aroused rats. The stereotypic effects of MDO-NPA were blocked by small doses of haloperidol, but not by large doses of reserpine. The effects due to large or small doses of MDO-NPA were also blocked by a microsomal enzyme inhibitor which did not interfere with the actions of NPA. These results suggest that MDO-NPA is a long-acting, orally effective prodrug of NPA with depot properties and dose-dependent agonistic and antagonistic interactions with central dopamine-mediated systems.

Aporphines. 39. Synthesis, dopamine receptor binding, and pharmacological activity of (R)-(-)- and (S)-(+)-2-hydroxyapomorphine.

The enantiomers (6aR and 6aS) of 2,10,11-trihydroxyaporphine (THA) were synthesized from thebaine and bulbocapnine and evaluated pharmacologically in vitro in comparison with (-)-apomorphine [(-)-APO] and dopamine by competition with tritiated apomorphine, ADTN, and spiroperidol for binding to a membrane fraction of calf caudate nucleus, as well as for ability to stimulate adenylate cyclase. In all four tests, the rank order of potency was (-)-APO greater than (-)-THA much greater than (+)-THA. Thus, these results extend the impression that the 6aR configuration for hydroxyaporphines is preferred for interactions with putative dopamine receptors and that 2-hydroxylation reduces potency in comparison with 10,11-dihydroxyaporphines.