title: Synthesis and dopamine transporter binding of 2beta-isopropyl ester analogs of cocaine.
abstract: A series of 2beta-isopropyl ester analogs of cocaine (7-11) was synthesised and evaluated in an in vitro dopamine transporter (DAT) binding assays. Ecgonine HCl (5) was obtained from (-)-cocaine (1) by hydrolysis using 1 N HCl. Acid catalysed esterification of 5 using 2-propanol and HCl gas afforded 2beta-isopropyl ecgonine (6). Compounds 7-9 were obtained via esterification of the 3beta-hydroxyl group of 6 using the appropriate acid chloride. Compound 10 was obtained via selective hydrolysis and re-esterification of 7 using 2-propanol and HCl gas. Compound 11 was obtained by reduction of 9 using H(2)/Pd-C. Compounds 7, 10 and 11 showed high binding affinity to the DAT (as indicated from the inhibition of the binding of [(3)H]WIN 35,428 (3)) with IC(50) values (mean +/- S.E.M.) 208.5 +/- 9.5, 47.43 +/- 1.79 and 11.25 +/- 3.37 nM, respectively). Compound 7 is comparatively as active as cocaine, 10 is ca. fivefold more active than cocaine and 11 is ca. 20-fold more active than cocaine and even twice more active than the radioligand 3. Compound 11, like its methyl ester analog (2' aminococaine), exhibited the highest affinity to the DAT. These results, along with previous results, emphasise the importance of a hydrogen-bond donor group at the 2'-position of cocaine and its isopropyl ester analogs to enhance binding affinity to the DAT.
authors.affiliation: Department of Medicinal Chemistry and Pharmaceutics, College of Pharmacy, University of Oklahoma Health Sciences Centre, Oklahoma City, OK 73190, USA. mona63@hotmail.com
authors.forename: Tarek F
authors.initials: TF
authors.lastname: El-Moselhy
authors.forename: Kwasi S
authors.initials: KS
authors.lastname: Avor
authors.forename: Garo P
authors.initials: GP
authors.lastname: Basmadjian
mesh_terms: D000818:Animals; D001692:Biological Transport; D001921:Brain / Q000378:metabolism; D003042:Cocaine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism* / Q000493:pharmacokinetics; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics*; D004353:Drug Evaluation, Preclinical; D020128:Inhibitory Concentration 50; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000378:metabolism*; D015394:Molecular Structure; D009419:Nerve Tissue Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D013816:Thermodynamics
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493216:Slc6a3 protein, rat; D003042:Cocaine