Synthesis and biological studies of unsaturated acyclonucleoside analogues of S-adenosyl-L-homocysteine hydrolase inhibitors.

The design, synthesis, and biological evaluation of several unsaturated acyclonucleosides related to augustmycin A are described. The (propargyloxy)methyl acyclonucleoside analogues of 6-chloropurine, adenine, 6-methoxypurine, hypoxanthine, 6-mercaptopurine, and azathioprine have been prepared. The 9-[(propargyloxy)methyl]adenine (5) and 9-[(propargyloxy)methyl]hypoxanthine (12) analogues were converted to the corresponding 5'-tributylstannyl intermediates (9 and 13), respectively, which gave 9-[[[(Z)-5-iodo-5-propenyl]oxy]methyl]adenine (10) and 9-[[[(Z)-5-iodo-5-propenyl]oxy]methyl]hypoxanthine (14), respectively, after iododestannylation. The [125I]-radiolabeled congeners of 10 and 14 were prepared as potential metabolic markers. Among the unsaturated acyclonucleosides tested, 9-[(propargyloxy)methyl]-6-chloropurine (3), 9-[(propargyloxy)methyl]-6-mercaptopurine (15), 9-[(propargyloxy)methyl]azathioprine (17), and angustmycin A analogue 10 showed inhibition of cancer cell growth, but only at a minimal level, and 17 also showed 14% cancer cell death in vitro. Compound 10 provided approximately 50% protection against HIV at 10(-4) M concentrations. Biodistribution results of [125I]-10 in mice indicate that compound 10 is readily metabolized via deiodination in vivo, possibly by serving as a substrate for the enzyme S-adenosyl-L-homocysteine hydrolase.     

New antihepatotoxic naphtho-pyrone glycosides from the seeds of Cassia tora

Two new naphtho-pyrone glycosides, 9-[(beta-D-glucopyranosyl-(1----6)-O-beta-D-glucopyranosyl)oxy]-10- hydroxy-7-methoxy-3-methyl-1H-naphtho[2,3-c]pyran-1 -one (5) and 6-[(alpha-apiofuranosyl-(1----6)-O-beta-D-glucopyranosyl)oxy]- rubrofusarin (6), together with cassiaside (3) and rubrofusarin-6-beta-gentiobioside (4) were isolated from the seeds of Cassia tora L. Their structures were elucidated on the basis of chemical and spectral data. The naphtho-gamma-pyrone glycosides (3, 4, and 6) were found to have significant hepato-protective effects against galactosamine damage, which were higher than that of silybin from Silybum marianum.     

Mutactimycin PR, a new anthracycline antibiotic from Saccharothrix sp. SA 103. I. Taxonomy, fermentation, isolation and biological activities

In the course of screening for new antibacterial agents, a new isolate collected from a soil sample of an arid area in south Algeria, produced a red pigment which was shown an antagonistic action against a gram-positive bacterium Bacillus subtilis. The isolate was identified as Saccharothrix sp. and named SA 103. The red pigment, eluted by HPLC on reverse phase C18 column, contained two compounds of an anthracycline antibiotics group. The structure of the major product (2) was characterized as mutactimycin C, and PR (1) was a new member of this group, designated as mutactimycin PR. These compounds showed an antibiotic activity against certain gram-positive bacteria in vitro. This is the first report of mutactimycins production by the genus Saccharothrix.     

Long acting dihydropyridine calcium antagonists. 2. 2-[2-Aminoheterocycloethoxy]methyl derivatives

A series of [(2-aminoheterocycloethoxy)methyl]dihydropyridines were prepared as selective coronary vasodilators. Results showed that a wide variety of five- and six-membered heterocycles were acceptable at the 2-position of the dihydropyridine ring and in vitro potency and tissue selectivity was independent of the basicity of these heterocycles. The SAR indicated that activity was optimum when the largest ester group was placed at the 3 rather than 5 position. 2-[[2-[(3-Amino-1H-1,2,4-triazol-5-yl)amino]ethoxy]methyl]-4- (2,3-dichlorophenyl)-3-(ethoxycarbonyl)-5-(methoxycarbonyl)-6-methyl- 1,4-dihydropyridine (3b) (UK-52,831) emerged as a potent (IC50 = 6.3 X 10(-9) M) and tissue-selective calcium channel blocker with a duration of action greater than 7 h in the anaesthetized dog.     

Synthesis of some guanylhydrazones and imidazolinylhydrazones as thromboxane-synthase and platelet aggregation inhibitors.

The imidazolinylhydrazones of (3-pyridinyloxy)-acetaldehyde and of 6-[3-(2-formyl-pyridinyl)oxy]hexanoic acid were synthesized as cyclic analogues of the corresponding guanylhydrazones which were found to be selective inhibitors of human thromboxane-synthase. The benzene isosters were also prepared in order to define the importance of the ring nitrogen for the activity. Moreover, the guanyl- and imidazolinyl-hydrazones of two 6-[(3-pyridinyl)oxy]hexanoic acids showing in the 2 position an alkyl chain with an alpha, beta-unsaturated ketonic function were prepared. Imidazolinylhydrazones 7 and 18 are selective inhibitors of thromboxane-synthase, while the two guanylhydrazones 14 and 15 which do not affect prostanoid biosynthesis seemed to be antagonists at the thromboxane receptor.     

c-Met小分子抑制剂XL880的合成

目的:合成c-Met小分子抑制剂XL880。方法:以3-甲氧基-4-羟基苯乙酮为起始原料通过7步反应合成了以c-Met为靶的酪氨酸激酶抑制剂XL880(N-{3-氟-4-{6-甲氧基-7-[3-(4-吗啉)丙氧基]喹啉}-4-氧基-苯基}-N-(4-氟苯基)-2,2-二亚甲基丙二酰胺)。结果:目标产物结构经1H-NMR和ESI-MS确证。结论:合成路线短,生产成本低,且合成方法简单温和,方便于小规模制备的实验室研究。     

Puberosides C-E, triterpenoid saponins from Glochidion puberum

Three new triterpenoid glycosides, named puberosides C-E (1-3), were isolated from the water-soluble fraction of Glochidion puberum (Linn.) Hutch. Their structures were determined as 3α-[(O-β-d-glucopyranosyl-(1?→?3)-O-α-l-arabinopyranosyl)oxy]-22α-trans-cinnamoyl-olean-12-ene-16α,28-diol, 3α-[(O-β-d-glucopyranosyl-(1?→?3)-O-α-l-arabinopyranosyl)oxy]-22α-cis-cinnamoyl-olean-12-ene-16α,28-diol, and 3α-[(O-β-d-glucopyranosyl-(1?→?3)-O-β-d-glucopyranosyl)oxy]-22α-benzoyloxy-olean-12-ene-16α,28-diol by the combination of 1D, 2D NMR, and MS spectral analyses.     

苯磷硫胺有关物质的合成

本研究合成了苯磷硫胺2个有关物质,即3-[(4-氨基-2-甲基嘧啶-5-基)甲基]-5-[2-[[羟基(膦酰氧基)膦酰基]氧基]乙基]-4-甲基-1,3-噻唑-3-鎓氯化物(5)和二磷酸单-[4-[(4-氨基-2-甲基嘧啶-5-基甲基)-甲酰基-氨基]-3-苯甲酰基硫基-戊-3-烯基]酯(6)。氯化3-[(4-氨基-2-甲基-5-嘧啶基)-甲基]-5-(2-羟乙基)-4-甲基噻唑鎓盐酸盐(2)与多聚磷酸反应得粗品5,经D301阴离子交换树脂柱纯化,减压浓缩,加异丙醇析出5,纯度96.55%。5在碱性条件下,低温与苯甲酰氯反应,经冷冻干燥得6,纯度97.57%。产物结构经MS、¹H NMR和¹³C NMR确证。     

4-Heterocyclyloxy-2H-1-benzopyran potassium channel activators

The reaction of 2,4-dihydroxypyridine (2) with 3,4-epoxy-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-6-carbonitrile (1) yielded the 4-[(1,2-dihydro-2-oxo-4-pyridyl)oxy] compound 3a, accompanied by small amounts of the isomeric 4-(1,2-dihydro-4-hydroxy-2-oxo-1-pyridyl) compound 4. This could also be prepared by hydrogenation of the benzyloxy derivative 5. Reaction of 3,6-pyridazinediol (10) with 1 (R = CN) gave the 4-[(1,6-dihydro-6-oxo-3-pyridazinyl)oxy] compound 11a, which in turn rearranged on heating with NaH in DMSO into the 4-(1,6-dihydro-3-hydroxy-6-oxo-1-pyridazinyl) compound 12. A series of 6-substituted analogues (R = CO2Me, CSNH2, NO2, Br) of 3a and 11a were synthesized. N-Alkylation led to compounds 14a-c (R = Me, Et, CHMe2). The 4-heterocyclyloxychromenes 9 and 16a were obtained by alkaline hydrolysis of their 3-camphorsulfonates. The racemic pyridazinyloxy compounds 11a and 14a could be resolved via their diastereomeric camphorsulfonates or camphanates. The differences between the 4-heterocyclyloxychromanols and the isomeric N-substituted compounds 4 and 12 were elucidated in the course of extensive NMR investigations. While in DMSO the former appeared to be conformationally flexible molecules the latter were rigid. All compounds were tested for oral antihypertensive activity in spontaneously hypertensive rats, using doses of 1 mg/kg. High and long lasting activities were found for the pyridyloxy compounds 3a and 3d, the pyridazinyloxy compound 11a, and its N-alkylation products, as well as for the 3S,4R-enantiomers 20a and 22a. (-)-(3S,4R)-3,4-Dihydro-4-[(1,6-dihydro-1-methyl-6-oxo-3- pyridazinyl)oxy]-3-hydroxy-2,2-dimethyl-2H-1-benzopyran-6-carbonitrile (22a) was selected for further development.     

N-ω-Carbethoxypentyl-4-quinolones: A New Class of Leukotriene Biosynthesis Inhibitors

6-[(4-Quinolinyl)oxy]hexanoic acids and the corresponding esters were designed and synthesized as inhibitors of the production of arachidonic acid metabolites. The inhibitory activities were assayed in vitro by evaluation of serum leukotriene B₄ and thromboxane B₂ production. While all 6-[(4-quinolinyl)oxy]hexanoic acids and their esters proved to be inactive, the N-alkyl-4-quinolones, obtained as by-products in their synthesis, were found to be a new class of leukotriene biosynthesis inhibitors.     

A new acylated flavone glycoside from the fruits of Stocksia brauhica

Phytochemical investigations of the fruits of Stocksia brauhica (Sapindaceae) resulted in the isolation of a new acylated flavone glycoside. Its structure of the new compound brauhenefloroside D (1) was established as 3-O-[(alpha-L-rhamnopyranosyl)oxy]-7-O-[(acetyl)-beta-D-glucopyranosyl (1 --> 4)]-[6-O-(4-hydroxy-E-cinnamoyl)-beta-D-glucopyranosyl-(1 --> 2)-alpha-L-rhamnopyranosyl)-oxy]-kaempferol. The structure elucidation of the new compound was based primarily on 1D and 2D NMR analysis, including COSY, HMBC and HMQC correlations.     

Glycyrrhizin and related compounds down-regulate production of inflammatory chemokines IL-8 and eotaxin 1 in a human lung fibroblast cell line

Glycyrrhizin (GL) is known to have various immunomodulating activities and has long been used clinically as an anti-allergic and anti-hepatitis agent. While the potency of GL against lung inflammatory diseases has been expected, the effect of GL on the lung has been poorly understood. Lung fibroblasts are known as a potent producer of inflammatory chemokines, IL-8 and eotaxin 1, by which neutrophils and eosinophils are strongly attracted during inflammation. Therefore, we studied the effects of GL on the production of these chemokines using a human fetal lung fibroblast cell line, HFL-1, stimulated with TNF-alpha and IL-4. Moreover, we examined the structure-activity relationships of GL to explore more beneficial compounds. 18alpha,beta-GL inhibited IL-8 dose-dependently and inhibited eotaxin 1 slightly. 18alpha,beta-Glycyrrhetic acid (GA) did not inhibit IL-8 but inhibited eotaxin 1. The effect of 18alpha,beta-glycyrrhetic acid monoglucuronide (MGA) resembled that of 18alpha,beta-GL but was weaker. Both 3beta-[(2-O-beta-D-glucopyranuronosyl-beta-D-glucopyranuronosyl)oxy]-18beta-11-deoxo-olean-12-en-30-oic acid (11-deoxo-GL) and 3beta-[(2-O-beta-D-glucopyranuronosyl-beta-D-glucopyranuronosyl)oxy]-olean-11,13,(18)-dien-30-oic acid (hetero-GL) exhibited inhibitory activity with significant cytotoxicity. 3beta-[(2-O-beta-D-Glucopyranuronosyl-beta-D-glucopyranuronosyl)oxy]-18beta-olean-9,12-dien-30-oic acid (homo-GL) did not have cytotoxicity but its activity was mild like that of 18alpha,beta-GL. 3beta-[(2-O-beta-d-Glucopyranuronosyl-beta-D-glucopyranuronosyl)oxy]-olean-11,13(18)-dien-30-ol (hetero-30-OH-GL) and 3beta-[(2-O-beta-D-glucopyranuronosyl-beta-D-glucopyranuronosyl)oxy]-18beta-olean-9,12-dien-30-ol (homo-30-OH-GL) showed potent inhibitory effects, at concentrations lower than 18alpha,beta-GL with no significant cytotoxicity. These results suggest that GL-related compounds are effective in reducing chemokine production and that GL-modified compounds including hetero-30-OH-GL and homo-30-OH-GL appear most beneficial in view of their inhibitory capacity with less cytotoxicity.     

4-Substituted 1-phenyl-1H-indazoles with analgesic, antiinflammatory, antipyretic and local anesthetic activities

The synthesis of amides 3 and 4 starting from (1-phenyl-1H-indazol-4-yl)acetic and [(1-phenyl-1H-indazol-4-yl)oxy]acetic acids, respectively, as well as of 2-(1-phenyl-1H-indazol-4-yl)ethanamines 5 starting from 3, is described. Moreover, a number of 2-[(1-phenyl-1H-indazol-4-yl)oxy]ethanamines 7 and 3-[(1-phenyl-1H-indazol-4-yl)oxy]propanamines 8 were prepared starting from 1-phenyl-1H-indazol-4-ol. Some compounds 3, 4 and 7 showed an appreciable analgesic activity in mice, whereas compounds 4 were moderately active as antiinflammatory agents in rats. Some compounds 3, 4, 5, 7 and 8 showed also local anesthetic and a weak antipyretic activity in mice and rats, respectively.     

Cardioselectivity of beta-adrenoceptor blocking agents 1. 1-[(4-Hydroxyphenethyl)amino]-3-(aryloxy)propan-2-ols.

A series of 1-[(4-hydroxyphenethyl)amino]-3-(aryloxy)propan-2-ols was synthesized together with several 1-[(3,4-dimethoxyphenethyl)amino]-3-(aryloxy)propan-2-ols. Their affinity to beta 1- and beta-2-adrenoceptors was determined and compared with the affinity of known beta-blockers. We were able to confirm the substantial cardioselectivity of 1-(3,4-dimethoxyphenethyl)-3-[(4-substituted aryl)oxy]propan-2-ols when compared to those with a 1-(4-hydroxyphenethyl) group. An increase in the size of the 4 substitutent of the 3-(aryloxy) moiety to caproamido leads to a substantially higher affinity for the beta 1--adrenoceptor of rat ventricular muscle in the presence of the 3,4-dimethoxyphenethyl than in the presence of the 4-hydroxyphenethyl or isopropyl group; this combination also gave the highest cardioselectivity.     

新型6,7-二甲氧基-4-(2-氟苯氧基)喹啉类c-Met抑制剂的设计、合成及生物活性研究

基于卡博替尼(cabozantinib)和foretinib的化学结构,通过改变中间链,设计合成了一系列含有哌嗪酰胺的6,7-二甲氧基-4-(2-氟苯氧基)喹啉类c-Met抑制剂。这些化合物未见文献报道,其结构通过MS和NMR确证。采用酶联免疫吸附测定(ELISA)法和MTT法测定了目标化合物对c-Met的抑制活性和对人结肠癌细胞(HT-29)、人肺癌细胞(H460)、人非小细胞肺癌细胞(A549)和人胃癌细胞(MKN-45)的细胞毒性。结果表明,4-(4-氯苯基)-N-[4-[(6,7-二甲氧基-4-喹啉)氧基]-3-氟苯基]哌嗪-1-甲酰胺(1b)、4-(3-氯苯基)-N-[4-[(6,7-二甲氧基-4-喹啉)氧基]-3-氟苯基]哌嗪-1-甲酰胺(1h)和4-(2-氯苯基)-N-[4-[(6,7-二甲氧基-4-喹啉)氧基]-3-氟苯基]哌嗪-1-甲酰胺(1j)对HT-29、H460、A549和MKN-45细胞的抑制活性明显优于对照药卡博替尼。其中,化合物1h和1j对c-Met具有较强的抑制活性,其IC50值分别为0.007 2和0.009 8 μmol/L。     

Evidence against the presence of A2 adenosine receptors on guinea pig ventricular myocytes.

The effects of different adenosine agonists on cAMP levels in isolated adult guinea pig ventricular myocytes were investigated. 2-Chloro-N6-cyclopentyladenosine (CCPA), R-N6-phenylisopropyl-adenosine (R-PIA), S-N6-phenylisopropyladenosine (S-PIA) and 5'-N-ethylcarboxamidoadenosine (NECA) reduced isoprenaline-stimulated cAMP Both the nonselective adenosine antagonist 8-[4-[( [[(2-aminoethyl)amino]carbonyl]methyl)oxy]-phenyl]-1, 3-dipropylxanthine ('xanthine amine congener'; XAC) and the A1-selective adenosine antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) blocked the inhibitory effect of NECA. Basal cAMP levels were not altered by NECA or the highly A2-selective 2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosin e (CGS 21680), either alone or in the presence of DPCPX or XAC. These results provide evidence against the existence of A2 receptors on the ventricular myocyte but support the presence of A1 receptors.     

3-Quaternary ammonium 1-carba-1-dethiacephems

A series of structurally unique 1-carba-1-dethiacephems is described. The structural stability of the 1-carba-1-dethiacephem nucleus was essential for the preparation of this series of 3-quaternary ammonium carbacephems. The known p-nitrobenzyl 7 beta-(phenoxyacetamido)- 3-[(trifluoromethyl)sulfonyl]oxy]-1-carba-1-dethia-3-cephem- 4-carboxylate served as both a quaternization substrate as well as a precursor to derivatives such as allyl 7 beta-[[2-[allyloxy)carbonyl]amino-4- thiazoly] (methoxyimino)acetyl]amino]-3-[(trifluoromethyl) sulfonyl] oxy]-1-carba-1-dethia-3-cephem-4-carboxylate. Quaternization of these enol triflates was accomplished either by dissolution in acetonitrile containing the base or by dissolution in the base, with or without warning to 50 degrees C. Bases nucleophilic enough to displace the triflate include a variety of substituted pyridines and N-methylimidazole. Deprotection then produced a very active series of 1-[7 beta-[(2-amino- 4-thiazolyl)(methoxyimino)acetyl]amino]-2-carboxy-8-oxo- 1-azabicyclo[4.2.0]oct-2-en-3-yl] quaternary ammonium hydroxide inner salts. These compounds were extremely potent antibacterials against a broad range of Gram-positive and -negative bacteria including constitutive cephalosporinase producers, such as Enterobacter cloacae. The compounds exhibit similar hydrolysis kinetics and pharmacokinetics to the analogous cephalosporin-3'-quaternary ammonium salts.     

(6,7-Dichlorobenzo[b]thien-5-yl)oxy]acetic acids and 1,1-dioxides. 1. A structurally novel class of diuretics with hypotensive activity

A series of [(6,7-dichlorobenzo[b]thien-5-yl)oxy]acetic acids and their corresponding 1,1-dioxides were synthesized and evaluated for diuretic activity in the acute saline loaded mice (ASLM) and hypotensive activity in the spontaneously hypertensive rat (SHR). A significant number of compounds were found to display potent activity in one or both assays, and preliminary structure-activity relationships with respect to each assay were delineated. Compound 94, the 1,1-dioxide of [(6,7-dichloro-2-n-propylbenzo[b]thien-5-yl)oxy]acetic acid was markedly active in both the ASLM and SHR by oral administration. The combined diuretic/hypotensive profile of this compound was further substantiated by its good saluretic response in water loaded conscious dogs and a moderate to good activity in renal hypertensive rats and sinoaortic-deafferented hypertensive dogs.     

Characterization of muscarinic receptors mediating vasodilation in guinea-pig ileum submucosal arterioles by the use of computer-assisted videomicroscopy.

Muscarinic receptors of resistance vessels (submucosal arterioles, outside diameter 50-75 microns) from the guinea-pig small intestine were investigated in vitro using a computer-assisted videomicroscopy system (Diamtrak). The muscarinic receptor which mediates vasodilation of precontracted [U-46619 (300 nM) or (-)-noradrenaline (10 microM)] arterioles was characterized with several muscarinic agonists and subtype-selective antagonists. The following agonists all produced equivalent maximum vasodilation (given in rank order of potency): acetylcholine = arecaidine propargyl ester (APE) greater than oxotremorine = (+/-)-muscarine = (+/-)-methacholine greater than carbachol greater than 4-[[N-(4-chlorophenyl)carbamoyl]oxy]-2-butynyltrimethylammonium iodide (4-Cl-McN-A-343). 4-[[N-(3-Chlorophenyl)-carbamoyl]oxy]-2-butynyltrimethylammonium chloride (McN-A-343) and N-ethyl-guvacine propargyl ester (NEN-APE) produced minimal or no arteriolar vasodilation. The muscarinic antagonists pirenzepine, (+-)-5,11-dihydro-11-[[[2-[2-((dipropylamino)methyl)-1-piperidinyl] ethyl]amino]-carbonyl]-6H-pyrido(2,3-b)(1,4)-benzodiazepin-6-one (AF-DX 384), 11-[[4-[4-(diethylamino)butyl]-1-piperidinyl]acetyl]-5,11-dihydro- 6H-pyrido(2,3-b)(1,4)-benzodiazepin-6-one (AQ-RA 741), p-fluorohexahydro-sila-difenidol (p-F-HHSiD), 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) and (R)- and (S)-hexahydro-difenidol [(R)-HHD, (S)-HHD] shifted the muscarine, methacholine or carbachol dose-response curve to the right in a competitive manner. Schild analysis of the data yielded pA2 values for pirenzepine (6.74/6.9), AF-DX 384 (6.72), AQ-RA 741 (6.58), p-F-HHSiD (7.53/7.57), 4-DAMP (9.06), (R)-HHD (7.88/8.32) and (S)-HHD (5.52/5.88). Thus, it can be concluded that submucosal arterioles possess only the M3 functional muscarinic receptor, the activation of which causes blood vessel dilation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of carbon-11 labeled iodinated cocaine derivatives and their distribution in baboon brain measured using positron emission tomography.

Three iodine-substituted derivatives of cocaine, methyl esters of 3-[(2'-, 3'-, and 4'-iodobenzoyl)oxy]-8-methyl-[1R-(exo,exo)]-8- azabicyclo[3.2.1]octane-2 carboxylic acid (2a-c), were synthesized and subjected to N-demethylation to give the corresponding noriodococaines 3-[(2'-,3'-, and 4'-iodobenzoyl)oxy]-[1R-(exo,exo)]-8- azabicyclo[3.2.1]-octane-2-carboxylic acid (3a-c). These were remethylated with [11C]CH3I to give the [N-11C-methyl]iodococaines 4a-c which were examined in baboon brain in vivo using positron emission tomography (PET). Compared to [N-11C]cocaine itself the regional distributions were changed from a highly specific localization in the corpus striatum to more diffuse patterns which included the cerebellum and cortex. Peak brain uptakes and clearance kinetics were also changed. [N-11C]-o-Iodococaine (4a) had a peak uptake in the striatum at 4-5 min after injection of only 17% that of cocaine in the same animal. The peak uptake of [N-11C]-p-iodococaine (4c) was 60% of that of [N-11C]cocaine and a clearance half-time of approximately 55 min, twice that of [N-11C]cocaine. [N-11C]-m-Iodococaine (4b) displayed half the uptake of [N-11C]cocaine, buts its clearance was similar to that of the parent molecule. The fractions of unmetabolized tracer in blood plasma at 1-30 min were higher for 4a-c than for [N-11C]cocaine. Plasma protein binding experiments showed 10%, 0.3%, 1.6%, and 6% as the free fraction for cocaine and o-, m-, and p-iodococaines respectively, consistent with the low brain uptake observed for the ortho isomer, and implicated alpha 1-acid glycoprotein as responsible for the low free fraction of o-iodococaine. The potencies of 2a-c to displace tritiated cocaine from striatal membranes were p-iodo approximately cocaine greater than m-iodo approximately o-iodo.