1. Probes for narcotic receptor mediated phenomena. 17. Synthesis and evaluation of a series of trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacet amide (U50,488) related isothiocyanate derivatives as opioid receptor affinity ligands
B R de Costa, R B Rothman, V Bykov, L Band, A Pert, A E Jacobson, K C Rice J Med Chem. 1990 Apr;33(4):1171-6.doi: 10.1021/jm00166a014.
A series of U50,488 related isothiocyanates was synthesized from enantiomerically pure (S,S)-(+)-trans-2-pyrrolidinyl-N-methylcyclohexylamine [(+)-7] and (R,R)-(-)-trans-2-pyrrolidinyl-N-methylcyclohexylamine [(-)-7]. DCC coupling of (+)- and (-)-7 with nitrophenylacetic acids followed by catalytic hydrogenation and treatment with thiophosgene afforded a series of six isomeric aryl isothiocyanate analogues of U50,488. Similarly, DCC coupling of (+)- and (-)-7 with (+)- and (-)-N-t-Boc-protected phenylglycines afforded four isomeric alkyl isothiocyanates. Evaluation of the isothiocyanates for their capacity to produce wash-resistant inhibition of mu, delta, and kappa sites in vitro was performed using rat and guinea pig brain membranes. None of the compounds was able to irreversibly inhibit binding of [3H]bremazocine to guinea pig and rat brain membranes (depleted of functional mu and delta receptors by pretreatment with acylating agents BIT and FIT). However, (1S,2S)-trans-2-isothiocyanato-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(-)-1] was able to specifically and irreversibly inhibit kappa receptors labeled by [3H]-U69,593: Incubation of rat brain membranes for 60 min at 25 degrees C with 1 microM of (-)-1 resulted in a wash-resistant reduction of the binding to 11.2 +/- 2.5% of the control. Binding analysis revealed the wash-resistant reduction in [3H]-U69,593 binding by (-)-1 to be through an increase in the Kd without effect on the Bmax. (-)-1 failed to effect mu or delta binding in rat or guinea pig brain under the same conditions. The enantiomer of (-)-1, (1R,2R)-trans-2-isothiocyanato-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(+)-1], failed to affect kappa receptors labeled by [3H]-U69,593 under the same conditions as for (-)-1. (1S,2S)-trans-3-Isothiocyanato-N-methyl-N-[2- (1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(-)-2] inhibited to 49.6 +/- 5.1% of the control, in a wash-resistant manner, kappa receptors labeled by [3H]-U69,593. However, (-)-2 was not as selective as (-)-1 since it also reduced [3H]DADLE (delta) binding to 82.4 +/- 8.0% of the control value. (1S,2S)-trans-4-Isothiocyanato-N-methyl-N-[2-(1-pyrrolidinyl)- cyclohexyl]benzeneacetamide [(-)-3] exhibited selective wash-resistant inhibition of delta receptors labeled by [3H]DADLE resulting in a reduction in binding to 42.9 +/- 4.2% of control.(ABSTRACT TRUNCATED AT 400 WORDS)
2. Alterations in the stereochemistry of the kappa-selective opioid agonist U50,488 result in high-affinity sigma ligands
B R de Costa, W D Bowen, S B Hellewell, C George, R B Rothman, A A Reid, J M Walker, A E Jacobson, K C Rice J Med Chem. 1989 Aug;32(8):1996-2002.doi: 10.1021/jm00128a050.
The synthesis and in vitro sigma receptor activity of the two diastereomers of U50,488 [(+/-)-2], namely, (1R,2S)-(+)- cis-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacet ami de [(+)-1] and (1S,2R)-(-)-cis-3,4-dichloro- N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamide [(-)-1], are described. (+)-1 and (-)-1 were synthesized from (+/-)-trans-N-methyl-2-aminocyclohexanol [(+/-)-3]. Pyridinium chlorochromate (PCC) oxidation of the N-t-Boc-protected derivative of (+/-)-3 afforded (+/-)-2-[N- [(tert-butyloxy)carbonyl]-N-methylamino]cyclohexanone [(+/-)-5]. The sequence of enamine formation with pyrrolidine, catalytic reduction, N-deprotection, and optical resolution afforded (1R,2S)-(-)-cis-2-pyrrolidinyl-N-methylcyclohexylamine [(-)-10] and (1S,2R)-(+)-cis-2-pyrrolidinyl-N-methylcyclohexylamine [(+)-10]. The optical purity (greater than 99.5%) of (-)-10 and (+)-10 was determined by HPLC analysis of the diastereomeric ureas formed by reaction with optically pure (R)-alpha-methylbenzyl isocyanate. The absolute configuration of (-)-10 and (+)-10 was determined by single-crystal X-ray diffractometry of the bis-(R)-mandelate salt. Condensation of optically pure (-)-10 and (+)-10 with 3,4-dichlorophenylacetic acid furnished (+)-1 and (-)-1, respectively. Compounds (+)-1, (-)-1, (-)-2, and (+)-2 were compared for their binding affinities at kappa opioid, sigma, D2-dopamine, and phencyclidine (PCP) receptors in competitive binding assays using [3H]bremazocine ([3H]BREM) or [3H]U69,593, [3H]-(+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine [[3H]-(+)-3-PPP], or [3H]-1,3-di(o-tolyl)guanidine ([3H]DTG), [3H]-(-)-sulpiride [[3H]-(-)SULP], and [3H]-1- [1-(2-thienyl)cyclohexyl]piperidine ([3H]TCP), respectively. In the systems examined, (-)-2 exhibited the highest affinity for kappa receptors, with a Ki of 44 +/- 8 nM. However, (-)-2 also showed moderate affinity for sigma receptors, with a Ki of 594 +/- 3 nM [[3H]-(+)-3-PPP]. The (1R,2R)-(+)-enantiomer, (+)-2, had low affinity for both kappa and sigma receptors, exhibiting Ki values of 1298 +/- 49 nM at kappa ([3H]BREM) and 1270 +/- 168 nM at sigma [[3H]-(+)-3-PPP]. In contrast, the chiral cis compounds (+)-1 and (-)-1 showed high affinity for sigma receptors and negligible affinity for kappa opioid receptors in the [3H]BREM assay. Compound (-)-1 exhibited a Ki of 81 +/- 13 nM at sigma receptors [[3H]-(+)-3-PPP] and 250 +/- 8 nM ([3H]DTG).(ABSTRACT TRUNCATED AT 400 WORDS)
