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trans‐Resveratrol‐3‐O‐β‐D‐glucupyranoside (trans‐piceid, 2) and trans‐resveratrol‐4′‐O‐β‐D‐glucupyranoside (trans‐resveratroloside 3) are the naturally occurring O‐glucoside conjugates of the polyphenolic stilbenoid trans‐resveratrol 1. Recently, attention has been drawn towards the interesting biological properties of the glucoside conjugates 2 and 3 as well as those of the aglycone 1. The fact that only limited quantities can be obtained by extraction from natural sources has prompted the development of novel syntheses of 2 and 3, based on a convergent Heck‐coupling strategy, which now conveniently allows for the preparation of multi‐milligram to gram quantities of each.

trans-Resveratrol ((E)-3,4',5-trihydroxystilbene, 1) is a phytoalexin produced naturally in plants and grape skins as a stress metabolite protecting against fungal attack. Widespread interest in this apparently structurally simple molecule and synthetic stilbene analogues has arisen in recent years due to the discovery of its antioxidant, antiinflammatory, and anti-carcinogenic activities, among others. Although O-conjugation with glucuronic acid in vivo is known to represent a significant metabolic pathway for polyphenolic compounds in general and 1 in particular, preclinical studies have been hampered by the lack of chemically pure, completely characterized reference standards of both regioisomeric 3-O-beta-d- and 4'-O-beta-d-glucuronide conjugates of 1 for adequate identification and quantification of these significant metabolites. The present work describes a concise, convergent synthesis of both 3-O-beta-d- and 4'-O-beta-d-glucuronide conjugates of 1 using a strategy based on a novel Heck coupling of iodoaryl-O-beta-d-glucuronate esters with appropriately substituted styrenes, such that highly pure multimilligram to gram quantities of both the 3-O-beta-d- and 4'-O-beta-d-glucuronide conjugates of 1 can now be conveniently synthesized.

A series of novel derivatives of oxcarbazepine (5), 10,11-dihydro-10-oxo-5H-dibenz/b,f/azepine-5-carboxamide was synthesised and evaluated for their anticonvulsant activity and sodium channel blocking properties. The oxime 8 was found to be the most active compound from this series, displaying greater potency than its geometric isomer 9 and exhibiting also the highest protective index value. Importantly, the metabolic profile of 8 differs from the already established dibenz/b,f/azepine-5-carboxamide drugs such as 1 and 5 which undergo rapid and complete conversion in vivo to several biologically active metabolites. In contrast 8 is metabolised to only a very minor extent leading to the conclusion that the observed anti-convulsant effect is solely attributable to 8. It is concluded that 8 may be as effective as 1 and 5 at controlling seizures and that the low toxicity and consequently high protective index should provide the compound with an improved side-effect profile.

7,8-Dichloro-1,2,3,4,5,6-hexahydrobenzo[ f ]quinolin-3-one 10 (R = H) is obtained by reaction of 5,6-dichloro-3,4-dihydronaphthalen-2(1H)-one pyrrolidine enamine 9 with acrylamide and is N-alkylated to 7,8-dichloro-1,2,3,4,5,6-hexahydro-4-propylbenzo[ f ]quinolin-3-one 10 (R = Prn). 6,7,8,9-Tetrahydro-2-methoxy-5H-benzo[7]annulen-6-one 5 (R = H) is converted to N,N-dipropyl(6,7,8,9-tetrahydro-2-methoxy-5H -benzo[7]annulen-6-yl)amine 8 and via the pyrrolidine enamine is reacted with acrylamide to give 2,3,4,5,6,7-hexahydro-9-methoxy-1H-benzo[3,4]cyclohepta[1,2- b]pyridin-3-one 11 (R = H) and 2,3,4,4a,5,6-hexahydro-8-methoxy-1H-benzo[5,6]cyclohepta[1,2- b]pyridin-2-one 12 (R = H). Each of these is N-alkylated to give 11 (R = Prn) and 12 (R = Prn) which are reduced individually to 2,3,4,4a,5,6,7,11b-octahydro-9-methoxy-4-propyl-1H-benzo[3,4] cyclohepta[1,2-b]pyridine 14 (X = Y = H) and 2,3,4,4a,5,6,11,11a-octahydro-8-methoxy-1-propyl-1H-benzo[5,6] cyclohepta[1,2-b]pyridine 15 (X = Y = H) respectively. The hydroxyimino derivative 19 (R = H) of 6,7,8,9-tetrahydro-1,2-dimethoxy-5H-benzo[7]annulen-5-one 18 is methylated to give 19 (R = Me) which with ethyl lithiopropiolate yields ethyl 3-(6,7,8,9-tetrahydro-5-hydroxy-1,2-dimethoxy-6-methoxyimino-5H -benzo[7]annulen-5-yl)propiolate 20 which is catalytically reduced to 21. 6,7,8,9-Tetrahydro-1,2-dimethoxy-6-propionamido-5H-benzo[7] annulen-5-one 22 prepared from 19 (R = H) is reacted with sodium borohydride to give both cis- and trans-6,7,8,9-tetrahydro-5-hydroxy-1,2-dimethoxy-6- propionamido-5H-benzo[7]annulen-5-ol 24 and 23 which are separately reduced by BH3–THF to cis- and trans-6,7,8,9-tetrahydro-5-hydroxy-1,2-dimethoxy-6- propylamino-5H-benzo[7]annulen-5-ol 26 and 25. The latter is reacted with chloroacetyl chloride and thence in two steps gives trans-2,3,4,4a,5,6,7,11b-octahydro-8,9-dimethoxy-4- propylbenzo[6,7]cyclohept[1,2-b][1,4]oxazine 29.

A series of novel derivatives of oxcarbazepine (5), 10,11-dihydro-10-oxo-5H-dibenz/b,f/azepine-5-carboxamide was synthesised and evaluated for their anticonvulsant activity and sodium channel blocking properties. The oxime 8 was found to be the most active compound from this series, displaying greater potency than its geometric isomer 9 and exhibiting also the highest protective index value. Importantly, the metabolic profile of 8 differs from the already established dibenz/b,f/azepine-5-carboxamide drugs such as 1 and 5 which undergo rapid and complete conversion in vivo to several biologically active metabolites. In contrast 8 is metabolised to only a very minor extent leading to the conclusion that the observed anti-convulsant effect is solely attributable to 8. It is concluded that 8 may be as effective as 1 and 5 at controlling seizures and that the low toxicity and consequently high protective index should provide the compound with an improved side-effect profile.

Novel nitrocatechol-substituted heterocycles were designed and evaluated for their ability to inhibit catechol-O-methyltransferase (COMT). Replacement of the pyrazole core of the initial hit 4 with a 1,2,4-oxadiazole ring resulted in a series of compounds endowed with longer duration of COMT inhibition. Incorporation of a pyridine N-oxide residue at position 3 of the 1,2,4-oxadiazole ring led to analogue 37f, which was found to possess activity comparable to entacapone and lower toxicity in comparison to tolcapone. Lead structure 37f was systematically modified in order to improve selectivity and duration of COMT inhibition as well as to minimize toxicity. Oxadiazole 37d (2,5-dichloro-3-(5-(3,4-dihydroxy-5-nitrophenyl)-1,2,4-oxadiazol-3-yl)-4,6-dimethylpyridine 1-oxide (BIA 9-1067)) was identified as a long-acting, purely peripheral inhibitor, which is currently under clinical evaluation as an adjunct to l-Dopa therapy of Parkinson's disease.

In this work, we present a comparative case study of “ ortho- ” and “ meta -nitrated” catecholic inhibitors of catechol- O -methyltransferase (COMT), with regard to their interaction with the catalytic site of the enzyme and the in vitro regioselective formation of their mono- O -methyl ether metabolites. In particular, the effects of altering the attachment position of the inhibitors9 side-chain substituent, within the classic nitrocatechol pharmacophore, were investigated. For this purpose, we compared two simple regioisomeric nitrocatechol-type inhibitors of COMT, BIA 3-228 and BIA 8-176, which contain the benzoyl substituent attached at the meta and ortho positions, respectively, relative to the nitro group. The two compounds were slowly O -methylated by COMT in vitro, but the particular substitution pattern of each compound was shown to have a profound impact on the regioselectivity of their O -methylation. To provide a plausible interpretation of these results, a comprehensive analysis of the protein-inhibitor interactions and of the relative chemical susceptibility to O -methylation of the catechol hydroxyl groups was performed by means of docking simulations and ab initio molecular orbital calculations. The major structural and chemical factors that determine the enzyme regioselectivity of O -methylation were identified, and the X-ray structure of the complex of COMT with S -adenosyl-l-methionine and BIA 8-176 is herein disclosed. This is the first reported structure of the soluble form of COMT complexed with a nitrocatecholic inhibitor having a bulky substituent group in adjacent position ( ortho ) to the nitro group. Structural and dynamic aspects of this complex are analyzed and discussed, in the context of the present study.

Novel regioisomeric "ortho-nitrated" catechols related to the catechol-O-methyltransferase (COMT) inhibitors BIA 3-202 3 and BIA 3-335 4 were synthesized and biologically evaluated. Changing the position of the nitro group from the "classical" meta- to the ortho-position relative to the side-chain substituent of the nitrocatechol pharmacophore exerted profound effects on selectivity and duration of COMT inhibition. Alkylaryl compounds 7a-d possessed shorter duration of action than their regioisomers, but 7b displayed reversed selectivity over 3 at 3 and 6 h, exhibiting preferential central inhibition. In the amino-substituted series, ortho-nitrated regioisomer 14k was less peripherally selective than 4 and short-acting, whereas decahydroquinoline 14g displayed an unprecedented combination of long-acting and selective peripheral inhibition. 7b could provide a useful tool to probe the pharmacological utility of short-acting, centrally selective COMT inhibitors in the treatment of depression in Parkinsonian patients, and 14g represents a promising candidate for clinical evaluation as an adjunct to L-Dopa therapy.

A novel series of potent, peripherally selective, and long-acting inhibitors of catechol-O-methyltransferase (COMT) has been synthesized. The introduction and nature of heteroatom-containing substituents to the side-chain of the nitrocatechol pharmacophore was found to have a profound effect on both peripheral selectivity and duration of COMT inhibition in the mouse. This approach led to the discovery of 1-(3,4-dihydroxy-5-nitrophenyl)-3-[4-[3-(trifluoromethyl)phenyl]-1-piperazinyl]-1-propanone hydrochloride 35 (BIA 3-335), which was found to possess a superior inhibitory profile in vivo over both the nonselective inhibitor tolcapone 1 and the peripherally selective but short-acting entacapone 2. In this model, 35 retained 75% inhibition of peripheral COMT at 6 h after oral administration, yet significantly, only a minor reduction of central (cerebral) COMT activity was observed. Molecular modeling techniques were applied to review the analysis of the ternary enzyme-inhibitor complex previously determined by X-ray crystallography and to provide a deeper understanding of the structure-activity relationships within this novel series. Furthermore, a computational approach was applied in an effort to elucidate the particular structural factors relevant to the poor blood-brain permeability of 35. In conclusion, the improved biological properties herein reported reveal 35 as a candidate for clinical studies as an adjunct to L-DOPA therapy for Parkinson's disease.

Catechol-O-methyltransferase (COMT, EC 2.1.1.6) plays a central role in the metabolic inactivation of neurotransmitters and neuroactive xenobiotics possessing a catechol motif. 1-(3,4-Dihydroxy-5-nitrophenyl)-2-phenyl-ethanone (BIA 3-202) is a novel nitrocatechol-type inhibitor of COMT, the potential clinical benefit of which is currently being evaluated in the treatment of Parkinson's disease. In the present work we characterize the molecular interactions of BIA 3-202 within the active site of COMT and discuss their implication on the regioselectivity of metabolic O-methylation. Unrestrained flexible-docking simulations suggest that the solution structure of this complex is better described as an ensemble of alternative binding modes, in contrast to the well defined bound configuration revealed by the X-ray structures of related nitrocatechol inhibitors, co-crystallized with COMT. The docking results wherein presented are well supported by experimental evidence, where the pattern of in vitro enzymatic O-methylation and O-demethylation reactions are analyzed. We propose a plausible explanation for the paradoxical in vivo regioselectivity of O-methylation of BIA 3-202, as well as of its related COMT inhibitor tolcapone. Both compounds undergo in vivo O-methylation by COMT at either meta or para catechol hydroxyl groups. However, results herein presented suggest that, in a subsequent step, the p-O-methyl derivatives are selectively demethylated by a microsomal enzyme system. The overall balance is the accumulation of the m-O-methylated metabolites over the para-regioisomers. The implications for the general recognition of nitrocatechol-type inhibitors by COMT and the regioselectivity of their metabolic O-methylation are discussed.

Catechol- O -methyltransferase (COMT; E.C. 2.1.1.6) is a ubiquitous enzyme in nature that plays an important role in the metabolism of catechol neurotransmitters and xenobiotics. In particular, inactivation of drugs such asl-3,4-dihydroxyphenylalanine (l-DOPA) via O -methylation is of relevant pharmacological importance, because l-DOPA is currently the most effective drug used in the treatment of Parkinson's disease. This justified the interest in developing COMT inhibitors as potential adjuncts to l-DOPA therapy. The kinetics of inhibition by BIA 3-335 (1-[3,4-dihydroxy-5-nitrophenyl]-3-( N -3′-trifluormethylphenyl)-piperazine-1-propanone dihydrochloride) were characterized using recombinant rat soluble COMT. BIA 3-335 was found to act as a potent, reversible, tight-binding inhibitor of COMT with a K i of 6.0 ± 1.6 nM and displaying a competitive inhibition toward the substrate binding site and uncompetitive inhibition toward the S -adenosyl-l-methionine (SAM) binding site. The 2.0-A resolution crystal structure of COMT in complex with its cosubstrate SAM and a novel inhibitor BIA 3-335 shows the atomic interactions between the important residues at the active site and the inhibitor. This is the first report of a three-dimensional structure determination of COMT complexed with a potent, reversible, and tight-binding inhibitor that is expected to have therapeutic applications.

A homologous series of novel nitro-catechol structures (7a-7e) were synthesized and tested as inhibitors of the enzyme catechol-O-methyltransferase (COMT). Increasing chain length was found to have significant impact on both brain penetration and duration of COMT inhibition in the rat. Of this series, compound 7b (1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone) was found to exhibit the most potent and selective inhibition of peripheral COMT, with an inhibition profile more similar to entacapone 2 than tolcapone 1 (an equipotent peripheral and central inhibitor) but with much improved duration of action (7b, 70% inhibition and 2, 25% inhibition at 9 h after administration). The effects of structural modifications to 7b on COMT inhibitory profile were investigated, and it is concluded that the carbonyl group and preferably unsubstituted aromatic ring are essential features to maintain prolonged peripheral COMT inhibition. The introduction of the alpha-methylene group, the major structural difference between 7b and 1, would appear responsible for the observed enhancement in selectivity of peripheral COMT inhibition of 7b, which has more limited access to the brain than 1.

A series of esters of the major metabolite of oxcarbazepine (2), 10, 11-dihydro-10-hydroxy-5H-dibenz[b,f]azepine-5-carboxamide, were synthesized and evaluated for their anticonvulsant and brain sodium channel-blocking properties. The compounds were assayed intraperitoneally and per os in rats against seizures induced by maximal electroshock (MES). Neurologic deficit was evaluated by the rotarod test. The enantiomeric acetates (R)-11 and (S)-12 were the most active of the series against MES-induced seizures with oral ED(50) values at t(max) of 10.9 +/- 2.3 and 4.7 +/- 0.9 mg/kg, respectively. After intraperitoneal administration, carbamazepine (1) behaved more potently than 2 and all other new dibenz[b, f]azepine-5-carboxamide derivatives in the MES test; compounds 2 and 12 were equally potent. In the rotarod test, low doses of 1 produced considerable motor impairment, which did not occur with 2, enantiomeric alcohols (S)-6, (R)-7, and racemic alcohol 8, or racemic acetate 10 or (R)-11. The potencies of the racemic and enantiomerically pure alcohols 8, (S)-6, and (R)-7 derived from 2 in the MES and rotarod test were found to be similar between them, and consequently they exhibit similar protective index values. All three forms of the alcohol and their corresponding acetates (pairs 8 & 10, 6 & 12, and 7 & 11) were found to differ in the MES or rotarod tests; the ED(50) value for (S)-6 against MES-induced seizures was nearly 3-fold that for (S)-12. The protective index also differed markedly between all stereoisomers of the alcohol and their corresponding acetates, most pronouncedly for compound (S)-12 which attained the highest value (12.5) among all compounds tested. Blockade of voltage-sensitive sodium channels was studied by investigating [(3)H]batrachotoxinin A 20-alpha-benzoate ([(3)H]BTX) binding. Acetates (R)-11 and (S)-12 were more potent than the standards 1 and 2 at inhibiting the binding of [(3)H]BTX to sodium channels and the influx of (22)Na(+) into rat brain synaptosomes. It is concluded that acetates (R)-11 and (S)-12 are not simple metabolic precursors of alcohols (R)-7 and (S)-6 in rodents but that they possess anticonvulsant and sodium channel-blocking properties in their own right.

Novel 5-aryloxy substituted 3-phenyl-1,3,4-oxadiazol-2(3H)-ones were prepared and identified as potent inhibitors of FAAH. In vitro SAR are discussed. Structural variations of the selected lead compound were explored in order to optimise in vivo efficacy and selectivity.