Synthesis and binding affinities of 2 beta-(3-iodoallyloxycarbonyl)-3 beta-(4-substituted-aryl)tropane analogues as ligands for the dopamine transporter studies.

Tropane analogues from cocaine, which is known to be one of the most reinforcing and addictive compounds, were designed, synthesized, and characterized for inhibition of presynaptic uptake of dopamine (DA) in brain. Eight new derivatives of 3 beta-aryl-2 beta-(3-iodoallyloxycarbonyl)tropanes were synthesized and tested for their potential abilities to displace [(3)H]2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (WIN 35,428) binding to the rat striatal membranes.

Serotonin receptor and transporter ligands - current status.

The serotonin (5-HT) receptor system has 14 different subtypes classified by pharmacology and function. Many ligands are widely used for therapeutic and diagnostic purposes in some severe human diseases. Most of the ligands that are specific for each 5-HT receptor have distinctive chemical structures with regard to pharmacophore elements including 4-arylpiperazine, benzimidazole, benzamide, chroman, aminopyridazine, tetralin, and polycycles. However, their affinity and selectivity for 5-HT, dopamine and alpha1 receptors depend on their substituents and linker spacers. 5-HT transporter inhibitors have also been developed as potential antidepressants. In contrast to classical tricyclic compounds, newly developed secondary amine derivatives such as paroxetine and tetralin show high binding affinity and selectivity. Radioisotope-labeled ligands have also been developed, including [carbonyl-(11)C]WAY 100635 for 5-HT1A receptor, [(11C) or (18)F]ketanserine derivatives for 5-HT(2) receptor, [(125)I]DAIZAC for 5-HT(3) receptor, and [123I]IDAM for 5-HT transporter, and these are accumulated in brain regions that are rich in the respective receptors. This review summarizes the recent development of 5-HT receptor- and transporter-specific ligands and their pharmacological properties on the basis of their chemical structures.

Facile oxidation of fused 1,4-dimethoxybenzenes to 1,4-quinones using NBS: fine-tuned control over bromination and oxidation reactions.

[figure: see text] Fused 1,4-dimethoxybenzenes could be oxidized to benzoquinones by either direct oxidation or demethylation-oxidation. The oxidative demethylation of 5,8-dimethoxy-2-methylquinoline using 1.1 equiv of NBS in aqueous THF and a catalytic amount of H2SO4 at 20 degrees C for 5 min gave 2-methylquinoline-5,8-dione in 98% yield without bromination. Moreover, we can control either bromination or oxidative demethylation, or both reactions.

Radiolabeling of paclitaxel with electrophilic 123I.

123I-Labeled paclitaxel, [123I]-1 was prepared by electrophilic aromatic radioiodination of 3'-N-(p-trimethylstannylbenzoyl)-3'-debenzoylpaclitaxel 2 with 123I- in the presence of peracetic acid.

Syntheses and binding affinities of 6-nitroquipazine analogues for serotonin transporter. Part 1.

6-Nitroquipazine has been known as one of the most potent and selective inhibitors of serotonin transporter in vitro and in vivo. Nine derivatives of 6-nitroquipazine were synthesized and tested for their potential abilities to displace [3H]citalopram binding to the rat cortical membranes.

Synthesis and in vitro antibacterial activity of 3-[N-methyl-N-(3-methyl-1,3-thiazolium-2-yl)aminolmethyl cephalosporin derivatives.

The new cephalosporins having N-linked quarternary ammonium salt at C-3 position were prepared from the reaction of 2-methylimino-3-methyl-1,3-thiazoline derivatives with cephalosporins. Also antimicrobial activities of those compounds were determined.

Syntheses and biological evaluation of (18)F-labeled 3-(1-benzyl-piperidin-4-yl)-1-(1-methyl-1H-indol-3-yl)propan-1-ones for in vivo mapping of acetylcholinesterase.

We synthesized novel (18)F-labeled acetylcholinesterase (AChE) inhibitors, 3-[1-(3- and 4-[(18)F]fluoromethylbenzyl)piperidin-4-yl]-1-(1-methyl-1H-i ndol-3-yl )propan-1-ones ([(18)F]1 and [(18)F]2) and 3-[1-(4-[(18)F]fluorobenzyl)piperidin-4-yl]-1-(1-methyl-1H-i ndol-3-yl )propan-1-one ([(18)F]3) in high yields (decay-corrected, 25%-40%) and with high effective specific activities (>37 GBq/micromol). Tissue distribution studies of the [(18)F]1 and the [(18)F]3 in mice showed the nonspecific bindings in brain regions, with metabolic defluorination of the [(18)F]1. The result suggests that these radioligands may not be suitable agents for in vivo mapping of AChE, despite their potent in vitro anti-AChE activities.

[18F]fluoromethylbenzylsulfonate ester: a rapid and efficient synthetic method for the N-[18F]fluoromethylbenzylation of amides and amines.

We have prepared 4-[18F]fluoromethylbenzylsulfonate esters as fluoromethylbenzylating agents. These agents are readily prepared by an [18F]fluoride ion displacement of the corresponding bissulfonate esters. The application of these 4-[18F]fluoromethylbenzylsulfonate esters to N-alkylation reaction of spiperone and 1-phenylpiperazine shows that the products 3-N-(4-[18F]fluoromethylbenzyl)spiperone and 1-N-(4-[18F]fluoromethylbenzyl)-4-phenylpiperazine are rapidly produced with high radiochemical yields under a no-carrier-added condition.

Spin-labeled psoralen probes for the study of DNA dynamics.

Six nitroxide spin-labeled psoralen derivative have been synthesized and evaluated as probes for structural and dynamic studies. Sequence specific photoaddition of these derivatives to DNA oligonucleotides resulted in site-specifically cross-linked and spin-labeled oligomers. Comparison of the general line shape features of the observed electron paramagnetic resonance (EPR) spectra of several duplexes ranging in size from 8 to 46 base pairs with simulated EPR spectra indicate that the nitroxide spin-label probe reports the global tumbling motion of the oligomers. While there is no apparent large amplitude motion of the psoralen other than the overall tumbling of the DNA on the time scales investigated, there are some indications of bending and other residual motions. The (A)BC excinuclease DNA repair system detects structural or dynamic features of the DNA that distinguish between damaged and undamaged DNA and are independent of the intrinsic structure of the lesion. NMR studies have shown that psoralen-cross-linked DNA has altered backbone dynamics and conformational populations in the immediate vicinity of the adduct [Emsley et al. (1993) J. Am. Chem. Soc. 115, 7765-7771; Spielmann et al. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 2345-2349]. We suggested that the signal for recognition of a lesion to be repaired is in the sugar--phosphate backbone and not in the damaged base(s).

6 alpha-[18F]fluoroprogesterone: synthesis via halofluorination-oxidation, receptor binding and tissue distribution.

We have evaluated 6 alpha-[18F]fluoroprogesterone as a potential imaging agent for progesterone receptor (PgR)-positive breast cancer. 6 alpha-Fluoroprogesterone (1) was obtained via halofluorination of the C-5 double bond in pregnenolone, followed by oxidation of the 3 beta-OH group, elimination of HBr from C-4,5, and epimerization at the C-6 center. The relative binding affinity (RBA) of 6 alpha-fluoroprogesterone (1) to PgR is 11 (R5020 = 100), and its binding selectivity index (BSI, i.e. the ratio of the RBA to the non-specific binding, NSB) is 14.4; these values are similar to those of progesterone. 17 alpha-Acetoxy-6 alpha-fluoroprogesterone (2) was also prepared by the same method, but was not used for fluorine-18 labeling studies because its binding affinity for PgR is very low (0.9). The synthesis of 1 was adapted to fluorine-18 labeling and although the overall radiochemical yield was low (decay-corrected, 0.3%), progestin [18F]1 was obtained in moderately high effective specific activity (147 Ci/mmol). In vivo distribution studies using estrogen-primed immature female rats showed that 6 alpha-fluoroprogesterone ([18F]1) has low uterine uptake, low target tissue selectivity, and high fat uptake, presumably due to its low RBA and BSI. High uptake in bone, which indicates extensive metabolic defluorination, suggests that the C-6 position of steroids may not be a good site for fluorine-18 labeling.

Synthesis of 11 beta-[18F]fluoro-5 alpha-dihydrotestosterone and 11 beta-[18F]fluoro-19-nor-5 alpha-dihydrotestosterone: preparation via halofluorination-reduction, receptor binding, and tissue distribution.

We have prepared 11 beta-fluoro-5 alpha-dihydrotestosterone (11 beta-F-DHT, 1) and 11 beta-fluoro-19-nor-5 alpha-dihydrotestosterone (11 beta-F-19-nor-DHT, 2) in order to investigate the properties of these new androgens labeled with fluorine-18 as potential androgen receptor (AR)-based imaging agents for prostate cancer. These compounds were synthesized in 6 steps from hydrocortisone and in 13 steps from 1,4-androstadiene-3,11,17-trione, respectively. Relative binding affinities (RBA) of 11 beta-F-DHT and 11 beta-F-19-nor-DHT to AR are 53.1 and 75.3 (R1881 = 100), respectively, the latter being the highest reported among fluorine-substituted androgens. The fluorination step, which involves addition of halogen fluoride across the 9(11)-double bond, followed by reductive dehalogenation at the 9 alpha-position has been adapted to introduce a fluorine-18-label at the 11 beta-position of DHT and 19-nor-DHT. The two high-affinity F-18-labeled ligands [18F]-1 and [18F]-2 were evaluated in vivo, in tissue distribution studies using diethylstilbestrol-pretreated mature male rats. 11 beta-F-DHT shows high prostate uptake and selective prostate to blood and prostate to muscle uptake ratios, the latter two ratios increasing from 5 and 8 at 1 h to 12 and 19 at 4 h postinjection. Moreover, this compound has low uptake in bone, displaying the lowest in vivo defluorination among all androgens labeled with fluorine-18 tested so far. The in vivo properties of 11 beta-F-DHT in rats are thus favorable for imaging of prostate cancer. On the other hand, 11 beta-F-19-nor-DHT shows low prostate uptake with low selectivity and high uptake in liver, kidney, and bladder. Even though this ligand has the highest RBA and undergoes little metabolic defluorination, it appears to suffer from rapid metabolism in vivo. Therefore, it is apparent that the biodistribution properties of androgens are affected by their structure and metabolism as well as by their RBA.

Crystal structure of doisynolic acid and the structure of other products formed during its synthesis.

The crystal structure of the D-seco-estrogen doisynolic acid shows it to have the natural S configuration at the position derived from C-14 in estrone. Two major by-products during the synthesis of doisynolic acid from estrone are shown to be dimeric steroids. One is an aldol condensation product, and the other appears to arise from an alkaline cleavage of the aldol product.

Homodimeric and heterodimeric bis(amino thiol) oxometal complexes with rhenium(V) and technetium(V). Control of heterodimeric complex formation and an approach to metal complexes that mimic steroid hormones.

We have investigated the possibility of preparing complexes of rhenium and technetium whose shape resembles that of ligands for steroid receptors. The general structure of N2S2 complexes of oxorhenium(V) and oxotechnetium(V) is such that they could replace the BC ring system of steroid, thereby generating a metal complex system with considerable size and shape similarity to a steroid. Such a metal-integrated steroid-shaped complex can be constructed as a heterodimer of two different amino thiols; complexes of rhenium and technetium with such heterodimeric bis-bidentate structure have not been systematically studied. In this investigation, we have shown that complexes of this nature form readily when appropriate metal precursors are combined with a mixture of amino thiols. In the systems we have studied, heterodimeric complex formation is preferred over homodimeric complex formation, and in one system where we were able to obtain an X-ray crystal structure, this oxorhenium heterodimer had the desired trans geometry. These rhenium and technetium-99m complexes are reasonably stable toward ligand exchange; they can be readily purified by chromatography under appropriate conditions, and the one technetium-99m complex studied in vivo shows some persistence in blood and gives good initial uptake in several tissues. The convenient and selective formation of such bis-bidentate heterodimeric complexes suggests that the development of metal-integrated complexes that resemble ligands for receptors may be possible.

N-(3-[18F]fluoropropyl)-spiperone: the preferred 18F labeled spiperone analog for positron emission tomographic studies of the dopamine receptor.

The ligands currently used for PET studies of the dopamine receptor are fluorine-18-labeled spiperone (FSp) and carbon-11 or fluorine-18-labeled N-methyl-spiperone. All three of these ligands have drawbacks in either their chemical preparation or their biological behavior. We have previously prepared a series of N-fluoroalkyl-spiperone derivatives which are simple to prepare in high radiochemical yield. N-[18F]fluoropropyl-spiperone (3-F-Pr-Sp) and N-[18F]fluoroethyl-spiperone (2-F-Et-Sp) were the most promising ligands. In vitro competitive binding studies showed affinities for the dopamine receptor of 3-F-Pr-Sp greater than FSp greater than 2-F-Et-Sp. Brain extraction studies in a primate model showed that FSp, 2-F-Et-Sp, and 3-F-Pr-Sp were not completely extracted by the brain. High bone uptake and kidney clearance was observed with 3-F-Pr-Sp, while 2-F-Et-Sp cleared through the intestine in rats. This is in contrast to FSp where clearance is through the kidney. Studies to evaluate the extraction of metabolites in the brain were carried out by administering large doses (10 mCi) of FSp, 2-F-Et-Sp and 3-F-Pr-Sp to rats and reinjecting the metabolites in blood into other rats. These experiments showed that less than 0.02% of the metabolites from FSp and 3-F-Pr-Sp entered the brain, while 0.5% of the metabolites from 2-F-Et-Sp entered the brain. The majority of the activity present in the cerebellum after the administration of 2-F-Et-Sp is metabolites; therefore 2-F-Et-Sp is unsuitable for PET imaging studies. PET imaging studies in baboons and in one normal human volunteer with 3-F-Pr-Sp showed a high striatum-to-cerebellum ratio, showing that 3-F-Pr-Sp can replace ligands currently in use to study dopamine receptors.

Biodistribution of N-alkyl and N-fluoroalkyl derivatives of spiroperidol; radiopharmaceuticals for PET studies of dopamine receptors.

There is great interest in the application of positron labeled ligands to map the dopamine receptor in vivo. A series of fluorine-18-labeled N-alkyl and N-fluoroalkyl spiroperidol (SP) derivatives N-methyl[18F]SP; N-ethyl[18F]SP; N-(2-[18F]fluoroethyl)SP; N-propyl[18F]fluoropropyl) SP; N-(3-fluoropropyl) [18F]SP; N-(2-[18F]fluoropropyl)SP; N-(2-[18F]fluorobutyl)SP; N-(2-[18F]fluoropentyl)SP; and N-(2-[18F]fluorohexyl)SP were synthesized. The lipophilicity of these ligands (log octanol/water partition coefficient) varies from 2.67 to 5.56 and the initial brain uptake in rats, measured at 2 min, was greatest with the methyl, ethyl, propyl, fluoroethyl, and fluoropropyl derivatives. The highest striatum/cerebellum values 1 h after administration were obtained with the N-methyl, N-propyl, and N-3-fluoropropyl derivatives, while that of N-2-fluoroethyl showed the greatest uptake of total activity in the brain at this time. The uptake of all these ligands in the striatum could be blocked by cold SP showing the striatal uptake to be by the dopamine receptors.

Synthesis of no-carrier-added N-([18F]fluoroalkyl)spiperone derivatives.

3-N-([18F]fluoroalkyl)spiperone derivatives (2,3) can be prepared by N-alkylation of spiperone (1) with fluoroalkyl halides. The fluoroalkylating species 2-[18F]fluoroethyl bromide (7), 3-[18F]fluoropropyl bromide (8) and 4-[18F]fluorobutyl bromide (9) were prepared by [18F]fluoride ion displacement of the corresponding trifluoromethanesulfonates (triflates 4,5,6). By this method, the 2-[18F]fluoroethyl-, 3-[18F]fluoropropyl-, and 4-[18F]fluorobutyl spiperone derivatives (2a-c) can be prepared and purified rapidly and conveniently, within 40 min, in yields of 30-40% (end of synthesis, EOS). An alternative approach, suitable for the preparation of 2-[18F]fluoroalkyl (ethyl, propyl, butyl, pentyl and hexyl) spiperone derivatives (3a-d), involves iodo[18F]fluorination of terminal olefins, followed by N-alkylation of spiperone. This sequence is less convenient and proceeds in lower overall yields (less than 5%).

Visual function in the ventral lateral geniculate nucleus of the cat.

The visual receptive fields of 293 single units in the ventral lateral geniculate nucleus of the cat were studied. In addition to the wide variety of types described by others, a group of units responding differentially to color was identified that included units responding particularly to blue and others with opponent color properties. Some units with spontaneous firing and without definite visual receptive fields were inhibited by stimulation of the optic chiasm (OX). A study of latency of firing to OX stimulation suggested that these cells were driven by retinal ganglion cells of the W type. One-third of all units studied were binocularly driven.

Afferent projections to the ventral lateral geniculate nucleus in the cat.

Horseradish peroxidase (HRP) injections were made into the dorsal lateral geniculate nucleus (LGNd) and ventral lateral geniculate nucleus (LGNv) of the cat in order to define afferent projections to LGNv. These were found from the superior colliculus, contralateral LGNv, dorsal median raphe nucleus, locus coeruleus, ipsilateral pretectum, and various portions of visual cortex. While many cortical areas project to LGNv (17, 18, 19, 21 and lateral suprasylvian), the heaviest input arises from areas 17 and 20. The cell bodies of origin are in layer 5 in contrast to layer 6 which projects to LGNd.

Effects of denervation and tenotomy on the gastrocnemius muscle in the frog: a histologic and histochemical study.

The effects of denervation on the gastrocnemius muscle of the frog were studied by histologic and histochemical methods. Thirteen Rana pipiens underwent unilateral sciatic neurotomy and were sacrificed weekly as long as 46 days. Of the three normal populations of muscle fibers, the small fibers underwent atrophy, the intermediate sized fibers remained unchanged in size, and the large fibers either did not change or underwent hypertrophy between 21 and 46 days. Necrosis of muscle fibers did not occur. Histochemical stains showed persistence of the normal pattern after denervation. The small fibers continued to have a high concentration of both oxidative and glycolytic enzyme activity (NADH-TR, SDH, phosphorylase), and the large fibers continued to have a low concentration of these enzymes. Depletion of glycogen stores was seen with PAS. Hypertrophic muscle fibers had mostly subsarcolemmal nuclei and few internal nuclei, suggesting that they may be physiologically tonic rather than twitch fibers. Achilles tenotomy at the time of denervation prevented the hypertrophy of large fibers. Abnormal inclusions have been demonstrated in mammalian muscle following tenotomy alone, but were not seen in the frog.