Synthesis and resolution of (+-)-7-chloro-8-hydroxy-1-(3'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro- 1H-3- benzazepine (TISCH): a high affinity and selective iodinated ligand for CNS D1 dopamine receptor.
The synthesis and resolution of (+-)-7-chloro-8-hydroxy-1-(3'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro-1 H-3- benzazepine, (+/-)-TISCH (8) has been achieved by resolution of intermediate 4, the O-methoxyl, 3'-bromo derivative, as the diastereomeric camphor sulfonate salt. The final products, R-(+)-8 and S-(-)-8, were prepared by treatment of R-(+)- or S-(-)-7, the 3'-tributyltin intermediates, with iodine in chloroform, followed by O-demethylation. By using HPLC with a chiral column, the optical purity (greater than 99%) of the intermediates and the final compounds was determined. Radioiodination was achieved by an iodo-destannylation reaction with sodium [125I]iodide and hydrogen peroxide. As expected, the R-(+)-[125I]-8 (the active isomer) displayed high affinity and selectivity to the CNS D-1 receptor in rat striatum tissue preparation (Kd = 0.205 nM). The rank order of potency was as follows: SCH-23390 (1a) greater than (+/-)-8 greater than (+)-butaclamol greater than spiperone, WB4101 greater than dopamine, 5-HT. After an iv injection, the R-(+)-[125I]-8 penetrated the blood-brain barrier with ease and displayed specific regional distribution corresponding to the D-1 receptor density, while the S-(-)-[125I]-8 showed no specific uptake. The data suggest that the ligand may be useful as a pharmacological tool for characterizing the D-1 dopamine receptor. When labeled with I-123, this ligand is a potential agent for in vivo imaging of CNS D-1 dopamine receptor.
Chumpradit
S
S
Department of Radiology, University of Pennsylvania, Philadelphia 19104.
Kung
M P
MP
Billings
J J
JJ
Kung
H F
HF
D000818:Animals; D001552:Benzazepines / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D003342:Corpus Striatum / Q000378:metabolism; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D008297:Male; D015394:Molecular Structure; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000378:metabolism*; D017447:Receptors, Dopamine D1; D014018:Tissue Distribution
D001552:Benzazepines; D007457:Iodine Radioisotopes; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; C067811:7-chloro-8-hydroxy-1-(3'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine