Abstract: The difference in the secondary binding site (SBS) between the dopamine 2 receptor (D2R) and dopamine 3 receptor (D3R) has been used in the design of compounds displaying selectivity for the D3R versus D2R. In the current study, a series of bitopic ligands based on Fallypride were prepared with various secondary binding fragments (SBFs) as a means of improving the selectivity of this benzamide analog for D3R versus D2R. We observed that compounds having a small alkyl group with a heteroatom led to an improvement in D3R versus D2R selectivity. Increasing the steric bulk in the SBF increase the distance between the pyrrolidine N and Asp110, thereby reducing D3R affinity. The best-in-series compound was (2S,4R)-trans-27 which had a modest selectivity for D3R versus D2R and a high potency in the β-arrestin competition assay which provides a measure of the ability of the compound to compete with endogenous dopamine for binding to the D3R. The results of this study identified factors one should consider when designing bitopic ligands based on Fallypride displaying an improved affinity for D3R versus D2R.
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With sodium iodide; In N-methyl-acetamide; acetone;
PREPARATION 57 4-(1-(2-Hydroxyethyl)-1H-benzimidazol-2-yl)[1,4]diazepane Hydriodic Acid Salt Combine 2-(t-butyldimethylsilyloxy)ethyl bromide (116.2 g, 486 mmol), and sodium iodide (100 g, 663 mol) in acetone (350 mL) and dimethylformamide (25 mL). Heat to reflux. After 4 hours, cool, filter and evaporate in vacuo to give a residue. Distill the residue to give 2-(t-butyldimethylsilyloxy)ethyl iodide: bp; 60 C. at 0.5 mm Hg.
With sodium iodide; In N-methyl-acetamide; acetone;
PREPARATION 57 4-(1-(2-Hydroxyethyl)-1H-benzimidazol-2-yl)[1,4]diazepane Hydriodic acid salt Combine 2-(t-butyldimethylsilyloxy)ethyl bromide (116.2 g, 486 mmol), and sodium iodide (100 g, 663 mol) in acetone (350 mL) and dimethylformamide (25 mL). Heat to reflux. After 4 hours, cool, filter and evaporate in vacuo to give a residue. Distill the residue to give 2-(t-butyldimethylsilyloxy)ethyl iodide: bp; 60 C. at 0.5 mm Hg.
With sodium iodide; In N-methyl-acetamide; acetone;
Preparation 57 4-(1-(2-Hydroxyethyl)-1H-benzimidazol-2-yl)[1,4]diazepane hydriodic Acid Salt Combine 2-(t-butyldimethylsilyloxy)ethyl bromide (116.2 g, 486 mmol), and sodium iodide (100 g, 663 mol) in acetone (350 mL) and dimethylformamide (25 mL). Heat to reflux. After 4 hours, cool, filter and evaporate in vacuo to give a residue. Distill the residue to give 2-(t-butyldimethylsilyloxy)ethyl iodide: bp; 60 C. at 0.5 mm Hg.
With sodium iodide; In acetone; at 70℃;
Step 3-A-alternative. J'ert-butyl(2-iodoethoxy)dimethylsilane A solution of (2-bromoethoxy)(tert-butyl)dimethylsilane (500 mg, 0.45 mL, 2.09 mmol) and sodium iodide (470 mg, 3.14 mmol) in 5.0 mL acetone was heated at 70 C with stir overnight. After cooling, solids were removed by filtration and the solid was washed with EtOAc. The combine filtrate and wash was evaporated to give pure title compound. 1H NMR (CDC13, 500 MHz)? 3.85 (t, 6.9 Hz, 2H), 3.22 (t, 7.0 Hz, 2H), 0.93 (s, 9H), 0.11 (s, 6H).
With potassium carbonate; In acetonitrile; at 80℃; for 2h;
2-bromoethoxy- xit y Id i met y I si I ane (CAS [86864-60-0]) (2.4 mL; 1 1 .4 mmol ) was added to a solution of 1 H-pyrazo le-4-carbaldehyde (CAS [35344-95-7] ) (910 mg; 9.5 mmol ) and K2CO3 ( 1 .6 g; 1 1 .4 mmol) in ACN (18 mL ). The reaction was heated at 80C for 2h. The reaction mixture was partitioned between a saturated solution of NaHCO; and EtOAc. The organic layer was separated, dried over MgS04, filtered and evaporated till dryness. The residue was purified by chromatography ov er silica gel ( Stationary phase: irregular SiOH 40 iim 120g, mobile phase gradient from: 100% DCM, 0% MeOH to 95% DCM, 5% MeOH). The fractions containing product were collected and ev aporated to dryness yielding 1 .6 g (65%) of intermediate 12 .
65%
With potassium carbonate; In acetonitrile; for 2h;Reflux;
A solution of 2-bromoethoxy-tert-butyldimethylsilane(CAS [86864-60-0]), (2.44mL;11.37mmol), <strong>[35344-95-7]1H-<strong>[35344-95-7]pyrazole-4-carbaldehyde</strong></strong> (CAS [35344-95-7]), (0.91g; 9.5mmol) and K2CO3 (1.57g; 11.37mmol) in ACN (18mL) was refluxed for 2 h. The mixture was cooled, poured into ice water and a saturated NaHCO3 solution, the aqueous layer was extracted with EtOAc. The organic layer was separated, dried over MgSO4, filtered and evaporated to dryness giving a crude compound which was purified by chromatography over silica gel (Stationary phase: irregular SiOH 15-40mum 120g, Mobile phase: Gradient from 100% DCM, 0% MeOH to 95% DCM, 5% MeOH). The fractions containing product were collected and evaporated to dryness yielding 1.56g (yield 65%) of intermediate 18.
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