Structural studies on McN-5652-X,a high-affinity ligand for the serotonin transporter in mammalian brain

McN-5652-X, (+)-1, is a potent, selective inhibitor of serotonin reuptake in mammalian brain. When radiolabeled with (11)C, it has served as a positron-emission tomography (PET) radiotracer for in vivo imaging of central serotonin transporters. We have determined the solid-state structures of (+)-1.HClO(4) and (+)-1.(+)-(2R,3R)-tartrate by single-crystal X-ray diffraction, thereby confirming the trans relative configuration (Chemical Abstracts Service rules of nomenclature) and the 6S,10bR absolute configuration for (+)-1. Results from a vibrational circular dichroism (VCD) study on (+)-1 in CDCl(3) are consistent with the 6S,10bR absolute configuration.     

Novel cyclohexene derivatives as anti-sepsis agents: synthetic studies and inhibition of NO and cytokine production

In order to develop an anti-sepsis agent, a series of cyclohexene derivatives were synthesized and evaluated for their biological activities. Through modification of the sulfonamide spacer moiety depicted by formula II, it was found that the benzylsulfone derivative 10a had potent inhibitory activity against the production of NO. Further modifications of the phenyl ring, ester moiety, and benzyl position of benzylsulfone derivatives III were carried out. Among these compounds, (R)-(+)-10a and (6R, 1S)-(+)-22a showed strong inhibitory activity not only against NO production but also against inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in vitro. Furthermore, (R)-(+)-10a and (6R, 1S)-(+)-22a protected mice from LPS-induced lethality in a dose-dependent manner.     

Stereoselective synthesis of 2,3,7-trimethylcyclooctanone and related compounds and determination of their relative and absolute configurations by the MalphaNP acid method

The copper/chiral phosphoramidite (L(1))-catalyzed conjugate addition of dimethylzinc to cycloocta-2,7-dienone 4, followed by the methylation of the intermediate enolate, yielded a single isomer of 7,8-dimethylcyclooct-2-enone (+)-5. Compound (+)-5 was subjected to the second conjugate addition with ent-L(1) giving only one stereoisomer of 2,3,7-trimethylcyclooctanone (+)-6, which was converted to 2,3,7-trimethylcyclooctanol 7. To determine the relative and absolute configurations of these compounds, the (1)H NMR anisotropy method using (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid {(S)-(+)-MalphaNP acid} 1 was applied. Racemic alcohol (+/-)-7 was esterified with (S)-(+)-MalphaNP acid 1 yielding diastereomeric esters, which were efficiently separated by HPLC on silica gel affording the first-eluted MalphaNP ester (-)-10a and the second-eluted one (-)-10b. The relative and absolute configurations of ester (-)-10a were determined to be (S;1R,2S,3R,7S) by analyzing the (1)H and (13)C NMR spectra of (-)-10a and (-)-10b, especially their HSQC-TOCSY and NOESY spectra, and by applying the MalphaNP anisotropy method. The alcohol 7 formed from (+)-6 was similarly esterified with (S)-(+)-MalphaNP acid 1 yielding an MalphaNP ester, which was identical with (-)-10a, and the relative and absolute configurations of 2,3,7-trimethylcyclooctanone (+)-6 were determined to be (2S,3R,7S).     

Synthesis of enantiopure trans-N-Boc-3-aminobicyclo[2.2.2]octane-2-carboxylic acids and their bicyclic 1,3-amino alcohol derivatives via the [4+2] cycloaddition of 1,3-cyclohexadiene to a chiral β-nitroacrylate

The chiral β-nitroacrylate 2 derived from the (R)- or (S)-4-(3-hydroxy-4,4-dimethyl-2-oxopyrrolidin-1-yl) benzoic acid 1 acts as a reactive dienophile in a diastereoselective Diels-Alder reaction with 1,3-cyclohexadiene. The major cycloadducts have been isolated and transformed into enantiopure trans(2S,3S)- or (2R,3R)-N-Boc-3-aminobicyclic[2,2,2]octane-2-carboxylic acids 5. The trans-(2S,3S)- or (2R,3R)-N-Boc 3-(hydoxymethyl)-2-aminobicyclic[2,2,2]octane 6 derivatives were also obtained.     

NMR evidence for syn-anti interconversion of a trans opened (10R)-dA adduct of benzo[a]pyrene (7S,8R)-diol (9R,10S)-epoxide in a DNA duplex

2D NMR has been used to examine the structure and dynamics of a 12-mer DNA duplex, d(T(1)A(2)G(3)T(4)C(5)A(6)A(7)G(8)G(9)G(10)C(11)A(12))-d(T(13)G(14)C( 15)C(16)C(17)T(18)T(19)G(20)A(21)C(22)T(23)A(24)), containing a 10R adduct at dA(7) that corresponds to trans addition of the N(6)-amino group of dA(7) to (-)-(7S,8R,9R,10S)-7,8-dihydroxy-9, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(-)-(S,R,R,S)-BP DE-2]. This DNA duplex contains the base sequence for the major dA mutational hot spot in the HPRT gene when Chinese hamster V79 cells are given low doses of the highly carcinogenic (+)-(R,S,S,R)-BP DE-2 enantiomer. NOE data indicate that the hydrocarbon is intercalated on the 5'-side of the modified base as has been seen previously for other oligonucleotides containing BP DE-2 (10R)-dA adducts. 2D chemical exchange-only experiments indicate dynamic behavior near the intercalation site especially at the 10R adducted dA, such that this base interconverts between the normal anti conformation and a less populated syn conformation. Ab initio molecular orbital chemical shift calculations of nucleotide and dinucleotide fragments in the syn and anti conformations support these conclusions. Although this DNA duplex containing a 10R dA adduct exhibits conformational flexibility as described, it is nevertheless more conformationally stable than the corresponding 10S adducted duplex corresponding to trans opening of the carcinogenic isomer (+)-(R,S,S, R)-BP DE-2, which was too dynamic to permit NMR structure determination. UV and imino proton NMR spectral observations indicated pronounced differences between these two diastereomeric 12-mer duplexes, consistent with conformational disorder at the adduct site and/or an equilibrium with a nonintercalated orientation of the hydrocarbon in the duplex containing the 10S adduct. The existence of conformational flexibility around adducts may be related to the occurrence of multiple mutagenic outcomes resulting from a single DE adduct.     

Synthesis and antibacterial properties of new N4-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids

Direct interaction between 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid and primary α-amino acids (exemplified by glycine, alanine, and l-valine) in aqueous ethanolic NaHCO(3) at 70-80°C for 24-72?h produced the respective N-(4-oxoquinolin-7-yl)-α-amino acids (6a-c). The latter derivatives underwent reductive lactamization upon treatment with Na(2)S(2)O(4) in aqueous ethanol to afford moderate yields of the corresponding pyrido[2,3-f]quinoxaline-8-carboxylic acids (8a-c). Acetylation of 8a-c using acetyl chloride afforded N(4)-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids (9a-c). The structures, assigned to these new heterocyclic products, are supported by analytical and spectral data. The synthesized compounds (6a-c/9a-c) showed appreciable antibacterial activity as compared with ciprofloxacin.     

Facile synthetic route to enantiopure unsymmetric cis-2,5-disubstituted pyrrolidines

The (+/-)-cis-5-arylcarbamoyl-2-ethoxycarbonylpyrrolidines 6a-g were firstly synthesized in 53-64% yields by using meso-diethyl-2,5-dibromoadipate 3 and (S)-(-)-1-phenylethylamine in three steps. The diastereomeric mixture (S;2S,5R)-(-)-7 and (S;2R,5S)-(+)-8 were prepared by the Grignard reaction and separated by a flash column chromatography in 29 and 52% yields. The absolute configurations of (+)-8 was confirmed by X-ray crystallographic analysis and the enantiopure pyrrolidines (2S,5R)-(-)-9/(2R,5S)-(+)-9 and (2S,5R)-(-)-10/(2R,5S)-(+)-10 were obtained in good yields.     

Conformational response of tartaric acid to derivatization: role of 1,3-dipole-dipole interactions

The four-carbon chain in (R,R)-tartaric acid derivatives is predominantly antiperiplanar (trans) in the acid, its salts, esters, and NH-amides, while (-)-synclinal (gauche) conformer is the most abundant in N,N'-tetraalkyltartramides. Trialkylsilylation or tert-butylation of the hydroxy groups at C2 and C3 does not appear to affect the conformational preference of NH-tartramides, but it does change the conformational equilibrium in the case of tartrates (toward (-)-gauche) and N,N'-tetraalkyltartramides (toward trans), as judged from the NMR data. X-ray diffraction data point to the stabilizing role of antiparallel dipole-dipole interactions due to the 1,3-CO/CH bonds. These interactions can be found in the trans and (-)-gauche conformers but are not possible for the (+)-gauche conformers of (R,R)-tartaric acid derivatives. This rationalizes small proportion of (+)-gauche conformers in tartaric acid derivatives and points to a significance of 1,3-dipole-dipole interactions. The conformation around the C1-C2 (and C3-C4) bond is different in tartrates (O-C-C=O, syn) and tartramides (O-C-C=O, anti); the CD data (n-pi* band) show that O-silylation or O-tert-butylation brings about conformational changes around the C1-C2 bond in the case of N,N'-tetraalkyldiamides only.     

Biosynthesis of trans,trans- and cis,trans-farnesols by soluble enzymes from tissue cultures of Andrographis paniculata

A cell-free system obtained from tissue cultures of Andrographis paniculata produces 2-trans,6-trans-farnesol (trans,trans-farnesol) and 2-cis,6-trans-farnesol (cis,trans-farnesol) (5:1), incorporating 10% of the radioactivity from 3R-[2-(14)C]mevalonate. There is total loss of (3)H from 3RS-[2-(14)C,(4S)-4-(3)H(1)]mevalonate and total retention from the (4R) isomer in both the trans,trans-farnesol and cis,trans-farnesol formed. When 3RS-[2-(14)C,5-(3)H(2)]mevalonate is used as substrate, there is total retention of (3)H in the trans,trans-farnesol, but loss of one-sixth of the (3)H in the cis,trans-farnesol. With (1R)- and (1S)-[4,8,12-(14)C(3),1-(3)H(1)]-trans,trans -farnesol and (1R)- and (1S)-[4,8,12-(14)C(3),1-(3)H(1)]-cis, trans-farnesol as substrates, the label is lost from the (1R)-cis,trans and (1S)-trans,trans isomers but retained in the (1R)-trans,trans and (1S)-cis,trans isomers; this shows that the pro-1S hydrogen is exchanged in the conversion of trans,trans-farnesol into cis,trans-farnesol and the pro-1R hydrogen in the conversion of cis,trans-farnesol into trans,trans-farnesol. (1R)-[1-(3)H(1)]-trans,trans-Farnesol and (1R)-[1-(3)H(1)]-cis,trans-farnesol have been synthesized by asymmetric chemical synthesis and exchanged with liver alcohol dehydrogenase. Both the trans- and the cis-alcohol exchange the pro-1R hydrogen atom.     

Absolute configuration of the alpha-methylbutyryl residue in longipinene derivatives from Stevia pilosa

The absolute configuration of the alpha-methylbutyryl residue in (4R,5S,7S,8S,9S,10R,11R,2'S)-7-angeloyloxy-9-hydroxy-8-(alpha-methylbutyryloxy)-longipin-2-en-L-one and (4R,5S,7S,8R,10R,11R,2'S)-7-angeloyloxy-8-(alpha-methylbutyryloxy)- longipin-2-en-L-one was determined by chemical correlation with (S)-(+)-benzyl alpha-methylbutyrate prepared from authentic (S)-(+)-alpha-methylbutyric acid. Both compounds were isolated from the hexane extracts of roots of Stevia pilosa Lag. together with four other longipinene derivatives. The developed correlation method is useful to ascertain the chirality of natural alpha-methylbutyryl esters found in nature and to reinforce the hypotheses on the biogenetic origin of these residues.     

Preparation and configuration of racemic and optically active analgesic dialkylaminoalkylnaphthalenes

The alkylaminoalkylnaphthalene 3 shows interesting opioid-like analgesic properties, μ-selective ligand competition, and enkephalin hydrolyzing enzyme inhibition. 3 possesses two chiral centers and can exist as two racemic pairs and four diastereomers. Since the binding of opioids with the receptor is stereoselective, it was important to have the two racemic pairs as well as the four diastereomers. In this paper the synthesis of the (1R,2R/1S,2S)- and (1R,2S/1S,2R)-racemates and the (1R,2R)- and (1S,2S)-enantiomers of the 1-ethyl-1-hydroxy-1-[2-(6-hydroxynaphthyl)]-2-methyl-3-dimethylaminopropane 3 is considered and the determination of absolute configuration is described. The (1R,2R/1S,2S)- 3 and (1R,2S/1S,2R)- 3 racemates and the (1R,2R)- 3 and (1S,2S)- 3 enantiomers were prepared by reaction of the racemic and optically active 1-dimethylamino-2-methylpentan-3-one 2 , respectively, with the lithiation product obtained from 2-bromo-6-tetrahydropyranyloxynaphthalene and acidic hydrolysis. The optical resolution of aminoketone 2 was carried out via fractional crystallization of salts (+)- and (?)-dibenzoyltartrates. The configuration of the optically active compounds was determined by X-ray analysis of a crystal of (+)-(1R,2R)- 3 · HCl · H₂O. Preliminary pharmachological tests showed that (+)-(1R,2R)- 3 enantiomer is able to induce opioid-like analgesia with a relative potency 2.5 times that of (1R,2R/1S,2S)- 3 and about 4 times that of morphine. © 1994 Wiley-Liss, Inc.     

Stereoselective pharmacokinetics of 3,4-methylenedioxymethamphetamine in the rat

Studies to characterize the pharmacokinetics of the enantiomers of MDMA were conducted in rats using the iliac arterial cannulation. Two routes of administration, intravenous and subcutaneous, were evaluated at two dose levels for each route [20 and 40 mg/kg (+/-)-MDMA for subcutaneous, 10 and 20 mg/kg (+/-)-MDMA for intravenous administrations]. The average half-life (+/- SD) for all dosing groups was 2.5 +/- 0.8 h for (-)-(R)-MDMA and 2.2 +/- 0.8 h for (+)-(S)-MDMA. The more rapid clearance of (+)-(S)-MDMA compared with (-)-(R)-MDMA is consistent with the area under the curve (AUC) data of the parent drug and its primary metabolite MDA. The mean (+/- SD) AUC S/R ratios of MDMA and MDA were 0.70 +/- 0.05 and 3.1 +/- 0.8, respectively. Following a 20 mg/kg dose of racemic MDMA iv the mean (+/- SD) of the percent dose excreted as (-)-(R)-MDMA, (+)-(S)-MDMA, (-)-(R)-MDA, and (+)-(S)-MDA were 20 +/- 10, 12 +/- 6, 3 +/- 1, and 6 +/- 2, respectively.     

Absolute configuration of labdanes and ent-clerodanes from Chromolaena pulchella by vibrational circular dichroism

The aerial parts of Chromolaena pulchella biosynthesize two groups of diterpenes belonging to opposite enantiomeric series, specifically, the furanoid ent-clerodanes (5R,8R,9S,10R)-(-)-hardwikiic acid (1), methyl (5R,8R,9S,10R)-(-)-hardwikiate (2), (5S,8R,9S,10R)-(-)-hautriwaic acid lactone (3), methyl (5R,8R,9S,10R)-(-)-nidoresedate (4) and methyl (8R,9R)-(-)-strictate (5), as well as the labdanes (5S,8R,9R,10S)-(+)-(13E)-labd-13-ene-8,15-diol (6) and (5S,8R,9R,10S)-(+)-isoabienol (7). The absolute configuration of the two groups of diterpenes was unambiguously assigned by comparison of the vibrational circular dichroism spectra of 3 for ent-clerodanes, and of 7 for labdanes with their theoretical spectra obtained by density functional theory calculations. The results support a biogenetic proposal to diterpenes found in the studied botanical species.     

A single site-specific trans-opened 7,8,9,10-tetrahydrobenzo[a]pyrene 7,8-diol 9,10-epoxide N2-deoxyguanosine adduct induces mutations at multiple sites in DNA

Site-specific mutagenicity of trans-opened adducts at the exocyclic N(2)-amino group of guanine by the (+)-(7R,8S,9S,10R)- and (-)-(7S,8R,9R,10S)-enantiomers of a benzo[a]pyrene 7,8-diol 9,10-epoxide (7-hydroxyl and epoxide oxygen are trans, BPDE-2) has been determined in Chinese hamster V79 cells and their repair-deficient counterpart, V-H1 cells. Four vectors containing single 10S-BPDE-dG or 10R-BPDE-dG adducts positioned at G(0) or G(-1) in the analyzed 5'-ACTG(0)G(-1)GA sequence of the non-transcribed strand were separately transfected into the cells. Mutations at each of the seven nucleotides were analyzed by a novel primer extension assay using a mixture of one dNTP complementary to the mutated nucleotide and three other ddNTPs and were optimized to quantify levels of a mutation as low as 1%. Only G --> T mutations were detected at the adducted sites; the 10S adduct derived from the highly carcinogenic (+)-diol epoxide was 40-50 and 75-140% more mutagenic than the 10R adduct in V79 and V-H1 cells, respectively. Importantly, the 10S adducts, but not the 10R adducts, induced separate non-targeted mutations at sites 5' to the G(-1) and G(0) lesions (G(0) --> T and C --> T, respectively) in both cell lines. Neither the T 5' to G(0) nor sites 3' to the lesions showed mutations. Non-targeted mutations may enhance overall mutagenicity of the 10S-BPDE-dG lesion and contribute to the much higher carcinogenicity and mutagenicity of (+)-BPDE-2 compared with its (-)-enantiomer. Our study reports a definitive demonstration of mutations distal to a site-specific polycyclic aromatic hydrocarbon adduct.     

Error-prone translesion synthesis by human DNA polymerase eta on DNA-containing deoxyadenosine adducts of 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene

When human DNA polymerase eta (pol eta) encounters N6-deoxyadenosine adducts formed by trans epoxide ring opening of the 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BaP DE) isomer with (+)-7R,8S,9S,10R configuration ((+)-BaP DE-2), misincorporation of A or G and incorporation of the correct T are equally likely to occur. On the other hand, the enzyme exhibits a 3-fold preference for correct T incorporation opposite adducts formed by trans ring opening of the (-)-(7S,8R,9R,10S)-DE-2 enantiomer. Adducts at dA formed by cis ring opening of these two BaP DE-2 isomers exhibit a 2-3-fold preference for A over T incorporation, with G intermediate between the two. Extension one nucleotide beyond these adducts is generally weaker than incorporation across from them, but among mismatches the (adducted A*) x A mispair is the most favored for extension. Because mutations can only occur if mispairs are extended, this observation is consistent with the occurrence of A x T to T x A transversions as common mutations in animal cells treated with BaP DE-2 isomers. Adducts with S absolute configuration at the point of attachment of the hydrocarbon to the base inhibit incorporation and extension by pol eta to a lesser extent than their R counterparts. Template-primers containing each of the four isomeric dA adducts derived from BaP DE-2 and two adducts derived from 9,10-epoxy-7,8,9,10-tetrahydrobenzo-[a]pyrene in which the 7- and 8-hydroxyl groups of the DEs are replaced with hydrogens exhibit reduced electrophoretic mobilities relative to the unadducted oligonucleotides. This effect is largely independent of DNA sequence. Decreased mobility correlates with an increased rate of incorporation by pol eta, suggesting a systematic relationship between the overall DNA structure and efficiency of the enzyme.     

Microbial transformation of (+)-nootkatone and the antiproliferative activity of its metabolites

Six metabolites were obtained as a result of microbial transformation of (+)-nootkatone (1) by the fungal strains: Botrytis, Didymosphaeria, Aspergillus, Chaetomium and Fusarium. Their structure were established as (+)-(4R,5S,7R,9R)-9α-hydroxynootkatone (2), (+)-(4R,5S,7R)-13-hydroxynootkatone (3) and (+)-(4R,5S,7R,9R,11S)-11,12-epoxy-9α-hydroxynootkatone (4), (+)-(4R,5S,7R,11S)-11,12-epoksynootkatone (5), (+)-(4R,5S,7R)-11,12-dihydroxynootkatone (6) and (+)-(4R,5S,7R)-7,11,12-trihydroxynootkatone (7) on the basis of their spectral data. Two products: (4) and (7) were not previously reported in the literature. The antiproliferative activity of (+)-nootkatone (1) and isolated metabolites (2-7) of its biotransformation has been evaluated.     

Initial reactions in the oxidation of 1,2-dihydronaphthalene by Sphingomonas yanoikuyae strains.

The substrate oxidation profiles of Sphingomonas yanoikuyae B1 biphenyl-2,3-dioxygenase and cis-biphenyl dihydrodiol dehydrogenase activities were examined with 1,2-dihydronaphthalene and various cis-diols as substrates. m-Xylene-induced cells of strain B1 oxidized 1,2-dihydronaphthalene to (-)-(1R,2S)-cis-1,2-dihydroxy-1,2-3,4-tetrahydronaphthalene as the major product (73% relative yield). Small amounts of (+)-(R)-2-hydroxy-1,2-dihydronaphthalene (15%), naphthalene (6%), and alpha-tetralone (6%) were also formed. Strain B8/36, which lacks an active cis-biphenyl dihydrodiol dehydrogenase, formed (+)-(1R,2S)-cis-1,2-dihydroxy-1,2-dihydronaphthalene (51%), in addition to (-)-(1R,2S)-cis-1,2-dihydroxy-1,2,3,4-tetrahydronaphthalene (44%) and (+)-(R)-2-hydroxy-1,2-dihydronaphthalene (5%). The cis-biphenyl dihydrodiol dehydrogenase of strain B1 oxidized both enantiomers of cis-1,2-dihydroxy-1,2-dihydronaphthalene, but only the (+)-(1S,2R)-enantiomers of cis-1,2-dihydroxy-1,2,3,4-tetrahydronaphthalene and cis-1,2-dihydroxy-3-phenylcyclohexa-3,5-diene. The results show that biphenyl dioxygenase expressed by S. yanoikuyae catalyzes dioxygenation, monooxygenation, and desaturation reactions with 1,2-dihydronaphthalene as the substrate, and cis-biphenyl dihydrodiol dehydrogenase catalyzes the enantioselective dehydrogenation of (+)-(1S,2R)-cis-1,2-dihydroxy-1,2,3,4-tetrahydronaphthalene and (+)-(1S,2R)-cis-1,2-dihydroxy-3-phenylcyclohexa-3,5-diene.     

Behavioural and electrophysiological responses of the bark beetle, Ips typographus, to potential pheromone components

ABSTRACT. Field tests showed ( S )-(-)- cis -verbenol and ( R )-(+)- trans -verbenol in combination with a second pheromonal component, 2-methyl-3-buten-2-ol, more attractive than the combination with their optical antipodes. Inhibition of response to the attractant component, ( S )-(-)- cis -verbenol, by high concentrations of its optical antipode did not occur. No significant differences were noted for response to the attractant, ( S )-(-)- cis -verbenol and 2-methyl-3-buten-2-ol, with the addition of either ipsdienol enantiomer or a racemic mixture of ipsdienol enantiomers. Electroantennogram (EAG) studies correlated well with the behavioural studies. EAGs recorded from male and female beetles revealed both sexes to have a lower threshold for the pheromone, ( S )-(-)- cis -verbenol, than its host terpene precursor, (-)- alpha -pinene. EAGs showed a greater number of acceptors for (-)- alpha-pinene in males than in females. EAGs at acceptor saturation to the enantiomers of alpha -pinene and the verbenol isomers showed males more responsive to (-)- alpha -pinene, (±)- cis -verbenol, and ( R )-(+)- trans -verbenol. Significantly greater EAGs were elicited in females than in males to (-)- alpha -pinene, and (±)- and ( S )-(-)- cis -verbenol. No significant differences in EAGs of females to the enantiomers of trans -verbenol were noted. EAGs showed similar thresholds in males and females to the pheromone component, 2-methyl-3-buten-2-ol; however, female response at threshold was significantly greater than male response. The results are discussed with regard to olfactory acceptor evolution.     

Novel chiral isoxazole derivatives: synthesis and pharmacological characterization at human beta-adrenergic receptor subtypes

Isoxazole derivative (+/-)-4 and the three pairs of stereoisomeric 3-bromo-isoxazolyl amino alcohols (S,R)-(-)-7a/(R,R)-(+)-7b, (S,R)-(-)-8a/(R,R)-(+)-8b, and (S,R)-(-)-9a/(R,R)-(+)-9b were synthesized and assayed for their affinity and efficacy at human beta(1)-, beta(2)-, and beta(3)-adrenergic receptors (beta-ARs) in membranes from Chinese hamster ovary (CHO) cells stably transfected with the respective receptor subtype. Whereas derivative (+/-)-4 did not bind at all three beta-ARs, stereoisomers (S,R)-7a-(S,R)-9a behaved as high-affinity ligands at beta(1)- and, particularly, at beta(2)-ARs (K(i) 2.82-66.7 nM). The K(i) values of isomers (R,R)-7b-(R,R)-9b at beta(1)- and beta(2)-subtypes were about 30-100 times higher than those of their (S,R)-7a-9a counterparts, indicating a sizable stereochemical effect. The affinity at beta(3)-ARs was negligible for all the investigated compounds. When submitted to a functional assay, the three stereoisomeric pairs showed a comparable pattern of efficacy at all three beta-AR subtypes. The highest value of efficacy (75-90%) was observed at beta(2)-ARs, whereas all compounds behaved as partial agonists (30-60%) at the beta(3)-subtype. The lowest degree of efficacy (15-35%) was found at beta(1)-ARs. The affinity/efficacy profile of the derivatives under study has been compared with that of the two model compounds, Broxaterol [(+/-)-1] and BRL 37344 [(+/-)-6].