• The synthesis and pharmacological activity of 3-arylecgonine methyl ester and 3-carbamoyloxyecgonine methyl ester analogues: Probes for the characterization of the dopaminergic cocaine receptor

      Kline, Richard Harry, Jr.; Wright, Jeremy, Ph.D. (1991)
      Several analogues of 3-arylecgonine methyl ester were designed, synthesized and characterized by {dollar}\sp1{dollar}H and {dollar}\sp{lcub}13{rcub}{dollar}C NMR, IR and MS. The compounds were synthesized as racemates from 2,4,6-cycloheptatriene carboxylic acid or as enantiomerically pure compounds from 1 R-cocaine hydrochloride. These analogues were assessed for their ability to inhibit ({dollar}\sp3{dollar}H) cocaine binding to bovine striatal tissue and ({dollar}\sp3{dollar}H) dopamine uptake into striatal synaptosomes. Methyl(1RS-2-exo-3-exo)-8-methyl-3-phenyl-8-azabicyclo (3.2.1) octane-2 carboxylate was the most potent showing IC{dollar}\sb{lcub}50{rcub}{dollar} values for inhibition of ({dollar}\sp3{dollar}H) cocaine binding and ({dollar}\sp3{dollar}H) dopamine uptake of 22 and 133 nM, respectively. The racemates and the 1R-isomers proved to be equally potent inhibitors of binding and uptake. The 1RS-{dollar}\alpha{dollar}-dinitrophenylecgonine methyl ester analogue had the lowest potency. IC{dollar}\sb{lcub}50{rcub}{dollar} values for inhibition of binding and uptake were 11 and 30 {dollar}\mu{dollar}M, respectively. One of these compounds, 1R-{dollar}\beta{dollar}-(p-aminophenyl)ecgonine methyl ester, was designed and synthesized as a potential ligand for affinity chromatography. Several (1{dollar}R{dollar}-2-{dollar}exo{dollar}-3-{dollar}exo{dollar})-3-({dollar}N\sp\prime{dollar}-phenylcarbamoyloxy)ecgonine methyl ester analogues were also designed, synthesized, and spectroscopically characterized. Many of these compounds were synthesized as 1{dollar}R{dollar}-stereoisomers from 1{dollar}R{dollar}-ecgonine methyl ester in good yields. These compounds were tested for their ability to inhibit ({dollar}\sp3{dollar}H) cocaine binding to rat striatal tissue and ({dollar}\sp3{dollar}H) dopamine uptake into synaptosomes prepared from the same tissue. The most potent of these analogues was (1{dollar}R{dollar}-2-{dollar}exo{dollar}-3-{dollar}exo{dollar})-3-({dollar}N\sp\prime{dollar}-3{dollar}\sp\prime {dollar}-nitrophenylcarbamoyloxy)-8-methyl-8-azabicyclo (3.2.1) octane-2-carboxylic acid methyl ester. IC{dollar}\sb{lcub}50{rcub}{dollar} values for inhibition binding and uptake were 37 and 178 nM, respectively. In general, compounds which contained meta substituents on the phenyl ring of the C{dollar}\sb3{dollar} phenylcarbamate side chain were more potent than those with para substituents. Also, analogues which contained electron withdrawing groups on the same phenyl ring had considerably higher potencies than those with electron donating groups. Meta and para substituted amino 3-carbamoyloxyecgonine methyl ester analogues were found to be potential affinity chromatography ligands. Two isothiocyanato derivatives proved to bind irreversibly to the receptor, and two azido compounds were shown to function as photoaffinity ligands. These probes may be instrumental in the eventual isolation and purification of the cocaine receptor/dopamine transporter.