Structure-affinity relationships of a unique nicotinic ligand: N(1)-dimethyl-N(4)-phenylpiperazinium iodide (DMPP)

DMPP is a well-known nicotinic agonist that does not fit any proposed pharmacophore for nicotinic binding and represents a unique ligand among the hundreds of nicotinic agonists studied in the past decades. A systematic modulation of the chemical structure of DMPP, aimed to establish its structure-affinity relationships, is reported. The research has allowed to identify molecules such as 11c, 13c, 14c, and 28c, with affinities for alpha(4)beta(2) receptors in the low nanomolar range, some 2 orders of magnitude lower than the lead compound. The agonistic properties of the most interesting compounds have been assessed by measuring their analgesic activity on mice (hot-plate test). Another result of the research was the identification of DMPP analogues, such as 3a (K(i) = 90 nM) and 14b (K(i) = 180 nM), that maintain affinity for the central nicotinic receptor when the ammonium function is changed into an aminic one and are therefore possible leads for drug development in neurodegenerative diseases.

Synthesis and screening for antiacetylcholinesterase activity of (1-benzyl-4-oxopiperidin-3-ylidene)methylindoles and -pyrroles related to donepezil

The design, synthesis, and rapid evaluation of a new class of acetylcholinesterase (AChE) inhibitors related to donepezil are reported. A molecular dynamics simulation of the complex between AChE and one representative compound of the series showed a possible inhibitor binding mode in which favorable interactions are formed between the benzylpiperidinone moiety and some active-site residues. The biochemical evaluation of this newly synthesized series was performed using a chemiluminescent method suitable for high-throughput screening.

Stereoselective synthesis, in vitro, and initial in vivo evaluation of 1-methylpiperidin-4-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (IPIP): a novel radioiodinated molecular probe with high affinity for the muscarinic receptor

1-Methylpiperidin-4-yl alpha-hydroxy-alpha-(1-iodo-1-propen-3-yl)-alpha-phenylacetate (IPIP, Fig. 1) was investigated as a potential radioiodinated molecular probe targeted to the muscarinic receptor complex. The IPIP stereoisomers were synthesized via a chiral intermediate in >95% enantiomeric excess. The R-isomers demonstrated a M(1) to M(2) subtype selectivity of approximately 3 to 1 and the S-isomers demonstrated non-subtype selective binding in vitro. IPIP was radiolabeled with iodide-125 with an average radiochemical yield of 74.4% (+/-14.8, n = 5), specific activities >800 mCi/micromol, and radiochemical purities >97%. In vivo the Z-isomers demonstrated high uniform cerebral uptake suggesting non-subtype selective binding. In contrast, E-R-IPIP, after allowing a low uptake in M(2) rich areas to clear, demonstrated a retention of activity in M(1) and M(4) rich cerebral regions. In addition, the cerebral uptake of E-R-IPIP and Z-S-IPIP were inhibited by 70-90% via pretreatment with R-QNB, an established muscarinic antagonist. An ex vivo metabolism study demonstrated Z-S-IPIP was stable at the receptor site with an absence of radiolabeled metabolites.

Unprecedented oxidation of a phenylglycinol-derived 2-pyridone: enantioselective synthesis of polyhydroxypiperidines

[reaction: see text]. The phenylglycinol-derived 2-pyridone 1 undergoes m-CPBA oxidation steroselectively leading to the chiral nonracemic unsaturated bicyclic hydroxylactam 2, from which the enantioselective synthesis of (3R,5R)-3,4,5-trihydroxypiperidine (16) and the formal synthesis of the azasugar epiisofagomine are described. The enantioselective synthesis of (S)-N-Boc-3-hydroxypiperidine and (3R,4S)-3,4-dihydroxypiperidine is also reported.

The [2+2]-photocycloaddition of aromatic aldehydes and ketones to 3,4-dihydro-2-pyridones: regioselectivity, diastereoselectivity, and reductive ring opening of the product oxetanes

3,4-Dihydro-2-pyridones [3,4-Dihydropyridin-2(1H)-ones] 6 were evaluated with respect to their use as alkene components in stereoselective Paternò-Büchi reactions. The parent compound 6a was shown to be a versatile synthetic building block that reacted with various photoexcited aromatic carbonyl compounds (benzaldehyde, benzophenone, acetophenone, methyl phenylglyoxylate, 3-pivaloyloxybenzaldehyde) with high regio- and diastereo-selectivity (51-63% yield). The products can be subjected to hydrogenolysis, opening a new and efficient route for the synthesis of 2-arylmethyl-3-piperidinols. As examples, the oxetanes 7a and 8a were hydrogenolytically cleaved and yielded the products 12 (88%) and 13 (93%). The ability of compound 6a to bind to a chiral lactam host through two hydrogen bonds was used favorably to differentiate the enantiotopic faces of its double bond. In the photocycloaddition to the chiral aldehyde 15, which was conducted at -10 degrees C in toluene, a high facial diastereoselectivity (>90% de. 56% yield) was recorded. The stereoselectivity results from a 1:1 association of dihydropyridone 6a to the aldehyde. The 4-substituted dihydropyridones 6b-6d (R = methyl, isopropyl, phenyl) were found to be less suited for potential use in photochemistry. The yields and facial diastereoselectivities recorded in their photocycloaddition to benzophenone remained low.

From hit to lead. Analyzing structure-profile relationships

Two compounds, obtained by random screening, and displaying micromolar activities on the mu opiate receptor were used as starting points for optimization. In that work, the traditional concept of the activity of a compound (related to one or a few targets) was extended to the comprehensive pharmacological profile of that compound on more than 70 receptors, transporters, and channels relevant to a CNS-oriented project. Using the two complementary design strategies based on two similarity concepts described in the previous paper, we have obtained analogues with IC(50) values ranging between 0.9 nM and a few micromolar on the mu receptor and displaying qualitatively different profiles. We discuss here, both on a case-by-case basis and from a statistical standpoint, the pharmacological profiles in light of the two similarity concepts.

Intramolecular Mannich reaction in the asymmetric synthesis of polysubstituted piperidines: concise synthesis of the dendrobate alkaloid (+)-241D and its C-4 epimer

[reaction: see text] The intramolecular Mannich reaction of delta-amino beta-keto esters with aldehydes and ketones is a new methodology for the synthesis of polysubstituted piperidines and is illustrated by the concise asymmetric synthesis of the dendrobate alkaloid (+)-241D and its C-4 epimer.

Organolanthanide-catalyzed intramolecular hydroamination/cyclization of amines tethered to 1,2-disubstituted alkenes

[reaction: see text] This contribution reports the organolanthanide-catalyzed intramolecular hydroamination/cyclization of amines tethered to 1,2-disubstituted alkenes to afford the corresponding mono- and disubstituted pyrrolidines and piperidines by using coordinatively unsaturated complexes of the type (eta(5)-Me(5)C(5))(2)LnCH(TMS)(2) (Ln = La, Sm), [Me(2)Si(eta(5)-Me(4)C(5))(2)]NdCH(TMS)(2), [Et(2)Si(eta(5)-Me(4)C(5))(eta(5)-C(5)H(4))]NdCH(TMS)(2), and [Me(2)Si(eta(5)-Me(4)C(5))((t)()BuN)]LnE(TMS)(2) (Ln = Sm, Y, Yb, Lu; E = N, CH) as precatalysts. [Me(2)Si(eta(5)-Me(4)C(5))((t)BuN)]LnE(TMS)(2) mediates intramolecular hydroamination/cyclization of sterically demanding amino-olefins to afford disubstituted pyrrolidines in high diastereoselectivity (trans/cis = 16/1) and in good to excellent yield.

Asymmetric synthesis of 2-substituted piperidines using a multi-component coupling reaction: rapid assembly of (S)-coniine from (S)-1-(1-phenylethyl)-2-methyleneaziridine

(S)-Coniine is made using a reaction which assembles the piperidine ring by the sequential formation of four new chemical bonds and installs the C-2 stereogenic centre with high levels of diastereocontrol (90% de).

A heterocycle-forming double michael reaction. [5 + 1] annulation route to highly substituted and functionalized piperidines

[reaction: see text]. Nitrogen-containing tethered diacids, easily prepared by reductive alkylation of diethyl aminomalonate or ethyl cyanoglycinate, undergo double Michael reactions with 3-butyn-2-one to give highly functionalized and substituted piperidines (pipecolic acid derivatives) with surprisingly high stereoselectivity. The heterocyclic double Michael adducts can be induced to undergo further cyclizations to give a variety of azabicyclic and diazabicyclic compounds.

Efficient synthesis of isofagomine and noeuromycin

Starting from D-arabinose the synthesis of the very strong glycosidase inhibitors isofagomine (2) and noeuromycin (3) was achieved in six and seven steps, respectively. Keystep in the reaction sequence is the application of an efficient C-4 oxidation method to benzyl alpha-D-arabino-pyranoside. Subsequent Henry reaction of the obtained aldoketose with nitromethane provided the required branched carbohydrate precursors, which gave access to 2 and 3 in 17-21% overall yield.

Cytotoxic activity of 2-aminomethylene-3(2H)-benzofuranones against human oral tumor cell lines

A total of 23 newly-synthesized 2-aminomethylene-3(2H)-benzofuranone and structurally-related compounds were compared for their cytotoxic activity against both normal (human gingival fibroblast HGF) and tumor cells (human oral squamous cell lines HSC-2, HSC-3 and human salivary gland tumor cells HSG). There was a significant variability of drug sensitivity among the oral tumor cell lines. In general, HSC-2 cells were the most sensitive, followed by HSG cells, while HSC-3 cells were the most resistant. HGF normal cells were highly resistant to all compounds, suggesting their tumor-specific cytotoxic action. The cytotoxic activity of the compounds with morpholine, 1-methylpiperazine or piperidine structure was generally elevated by the introduction of fluorine, but not chlorine and methoxy functional groups, to the benzofuranone structure, whereas that of compounds attached by 1-phenylpiperazine or 1-(2-pyridyl)piperazine was rather reduced. The most active compounds induced internucleosomal DNA fragmentation in human promyelocytic leukemia HL-60 cells, but not in HSG, further confirming that oral tumor cell lines are resistant to DNase digestion.

N-Acyl-N-phenyl ureas of piperidine and substituted piperidines endowed with anti-inflammatory and anti-proliferative activities

Six series of N-acyl-N-phenyl ureas 1-6 of piperidine (1), and 2-ethyl- (2), 3-methyl- (3), 4-methyl- (4), 4-phenyl- (5), cis-2,6-dimethyl- (6) piperidine were synthesised and evaluated for their anti-inflammatory, anaesthetic, anti-pyretic properties. Some derivatives of series 1 and 5 were also assayed for anti-proliferative activity. Several compounds showed an anti-inflammatory activity comparable or slighty inferior to that of indomethacin in rats (1c,d, 2a,b,g,h, 3b, 4h, 5d,e). Moreover, an appreciable anti-inflammatory activity was also found in 2c,e, 3e,f,g, 4g, 5a,b,c,f,h, and 6a,b,d. All the compounds were devoid of anti-pyretic activity and only a few of them exhibited a low level of infiltration anaesthesia in mice. Compound 5a showed a broad spectrum anti-cancer activity (at low micromolar concentrations), particulary significant against leukemia subpanel.

Solid-phase synthesis of aspartic peptidase inhibitors: 3-alkoxy-4-aryl piperidines

[reaction: see text]. The 3-alkoxy-4-aryl piperidines are non-peptide peptidomimetic inhibitors of several aspartic peptidases. The solid-phase functionalization of 3,4-disubstituted piperidine scaffolds using a traceless linker strategy is described. Synthesis of diverse analogues based on this scaffold provides the potential to generate selective inhibitors of this important class of peptidase.

5-HT(3)R binding of lerisetron: an interdisciplinary approach to drug-Receptor interactions

The design, synthesis, and use of lerisetron-based molecular probes to investigate the 5-HT(3)R binding site are described. A SAR study, which involved distance and electronic parameter modifications of lerisetron's N-benzyl group, resulted in the discovery of a partial agonist.

Conformationally restricted indolopiperidine derivatives as potent CCR2B receptor antagonists

The preparation and biological evaluation of a series of indolopiperidine CCR2B receptor antagonists possessing a conformationally restricted C-5 linker chain in combination with a restricted piperidine ring are described. Compared to the parent compound 1, analogue 8 shows a dramatic improvement in selectivity against a range of 5-HT and dopaminergic receptors.

Discovery of (R)-1-[2-hydroxy-3-(4-hydroxy-phenyl)-propyl]-4-(4-methyl-benzyl)-piperidin-4-ol: a novel NR1/2B subtype selective NMDA receptor antagonist

Starting from Ro-25-6981 as a lead compound, highly potent and selective NR1/2B subtype selective NMDA receptor antagonists, with low activity at alpha(1) adrenergic receptors were developed.

Novel 4-piperidinopyridine inhibitors of oxidosqualene cyclase-lanosterol synthase derived by consideration of inhibitor pK(a)

Potent inhibition of rat microsomal oxidosqualene cyclase-lanosterol synthase (OSC) was maintained after structural modification of the 4-piperidinopyridine OSC inhibitor series. These novel analogues with a much lower pK(a) range (5.8-6.7) gave potent oral inhibition of rat cholesterol biosynthesis (8 ED(80) 0.7 mg/kg), and diminished effects on rat feeding after a 100 mg/kg oral dose.

Identification of the first trans-(3R,4R)- dimethyl-4-(3-hydroxyphenyl)piperidine derivative to possess highly potent and selective opioid kappa receptor antagonist activity

A structurally novel opioid kappa receptor selective ligand has been identified. This compound, (3R)-7-hydroxy-N-((1S)-1-[[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl]-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic, 10) demonstrated high affinity for the kappa receptor in the binding assay (kappa K(i) = 0.3 nM) and highly potent and selective kappa antagonism in the [(35)S]GTP-gamma-S assay using cloned opioid receptors (kappa K(i) = 0.006 nM, mu/kappa ratio = 570, delta/kappa ratio > 16600).

Design, synthesis, and structure-activity relationships of a series of 3-[2-(1-benzylpiperidin-4-yl)ethylamino]pyridazine derivatives as acetylcholinesterase inhibitors

Starting from the 3-[2-(1-benzylpiperidin-4-yl)ethylamino]-6-phenylpyridazine 1, we performed the design, the synthesis, and the structure-activity relationships of a series of pyridazine analogues acting as AChE inhibitors. Structural modifications were achieved on four different parts of compound 1 and led to the following observations: (i) introduction of a lipophilic environment in the C-5 position of the pyridazine ring is favorable for the AChE-inhibitory activity and the AChE/BuChE selectivity; (ii) substitution and various replacements of the C-6 phenyl group are possible and led to equivalent or slightly more active derivatives; (iii) isosteric replacements or modifications of the benzylpiperidine moiety are detrimental to the activity. Among all derivatives prepared, the indenopyridazine derivative 4g was found to be the more potent inhibitor with an IC(50) of 10 nM on electric eel AChE. Compared to compound 1, this represents a 12-fold increase in potency. Moreover, 3-[2-(1-benzylpiperidin-4-yl)ethylamino]-5-methyl-6-phenylpyridazine 4c, which showed an IC(50) of 21 nM, is 100-times more selective for human AChE (human BuChE/AChE ratio of 24) than the reference compound tacrine.

CuI-catalyzed coupling reaction of beta-amino acids or esters with aryl halides at temperature lower than that employed in the normal Ullmann reaction. Facile synthesis of SB-214857

[reaction: see text] The CuI-catalyzed coupling reaction of aryl halides with beta-amino acids or beta-amino esters is completed at 100 degrees C in 48 h, which indicates that the structure of the beta-amino acid has an accelerating effect for the Ullmann-type aryl amination reaction. This coupling reaction can be used to prepare enantiopure N-aryl beta-amino acids. An efficient synthetic route to SB214857, a potent GPIIb/IIIa receptor antagonist, is developed using this method.

A short synthesis of argatroban. a potent selective thrombin inhibitor

Argatroban was synthesized in seven steps from 4-methylpiperidine. The condensation of (+/-)-trans-benzyl 4-methylpipecolic acid ester with N(alpha)-Boc-N(omega)-nitro-L-arginine led to two diastereomers that were separated. One of them is the precursor of argatroban.

Synthesis and pharmacological activity of metabolites of the 5-HT(4) receptor antagonist SB-207266

Three metabolites of N-[(1-butyl-4-piperidinyl)methyl]-3,4-dihydro-2H-[1,3]-oxazino[3,2_a]indole-10-carboxamide (SB-207266) (1) were synthesised and their pharmacological activity determined.

Novel (4-piperidin-1-yl)-phenyl sulfonamides as potent and selective human beta(3) agonists

A series of novel (4-piperidin-1-yl)-phenyl sulfonamides was prepared and evaluated for their biological activity on the human beta(3)-adrenergic receptor (AR). Replacement of the 3,4-dihydroxyl group of the catechol moiety with 4-hydroxyl-3-methyl sulfonamide on the left-hand side of the compounds resulted in a number of potent full agonists at the beta(3) receptor. Modification of the right-hand side of the compounds by incorporation of a free carboxylic acid resulted in a few potent human beta(3) agonists with low affinities for beta(1)- and beta(2)-ARs. N-Alkyl substitution on the 4-piperidin-1-yl-phenylamine further increased the beta(3) potency while maintaining the selectivity. For example, sulfonamide 48 is a potent full beta(3) agonist (EC(50)=0.004 microM, IA=1.0) with > 500-fold selectivity over beta(1)- and beta(2)-ARs.