J. Richard Heys

[N-methyl-3H3]AZ10419369 Binding to the 5-HT1B Receptor: In Vitro Characterization and in Vivo Receptor Occupancy

Radiotracers suitable for positron emission tomography studies often serve as preclinical tools for in vivo receptor occupancy. The serotonin 1B receptor (5-HT1B) subtype is a pharmacological target used to discover treatments for various psychiatric and neurological disorders. In psychiatry, 5-HT1B antagonists may provide novel therapeutics for depression and anxiety. We report on the in vitro and in vivo evaluation of tritiated 5-methyl-8-(4-methyl-piperazin-1-yl)-4-oxo-4H-chromene-2-carboxylicacid (4-morpholin-4-yl-phenyl)-amide ([N-methyl-3H3]AZ10419369), a potent 5-HT1B radiotracer. [N-methyl-3H3]-AZ10419369 showed saturable single-site high-affinity in vitro binding (guinea pig, Kd = 0.38 and human, Kd = 0.37) to guinea pig or human 5-HT1B receptors in recombinant membranes and high-affinity (Kd = 1.9 nM) saturable (Bmax = 0.099 pmol/mg protein) binding in membranes from guinea pig striatum. When [N-methyl-3H3]AZ10419369 was administered to guinea pigs by intravenous bolus, the measured radioactivity was up to 5-fold higher in brain areas containing the 5-HT1B receptor (striatum/globus pallidus, midbrain, hypothalamus, and frontal cortex) compared with the cerebellum, the nonspecific binding region. Specific uptake peaked 30 min after injection with slow dissociation from target regions, as suggested by the in vitro binding kinetic profile. Pretreatment with 6-fluoro-8-(4-methyl-piperazin-1-yl)-4-oxo-4H-chromene-2-carboxylic acid [4-(4-propionyl-piperazin-1-yl)-phenyl]-amide (AZD1134) and 2-aminotetralin (AR-A000002), 5-HT1B-selective ligands, inhibited [N-methyl-3H3]AZ10419369-specific binding in a dose-dependent manner. In the guinea pig striatum, AZD1134 (ED50 = 0.017 mg/kg) occupies a greater percentage of the 5-HT1B receptors at a lower administered dose than AR-A000002 (ED50 = 2.5 mg/kg). In vivo receptor occupancy is an essential component to build binding-efficacy-exposure relationships and compare novel compound pharmacology. [N-methyl-3H3]AZ10419369 is a useful preclinical tool for investigating 5-HT1B receptor occupancy for novel compounds targeting this receptor.

Synthesis of I‐125 labeled photoaffinity rapamycin analogs

Two no-carrier-added 125 I-labeled photoaffinity rapamycin analogs were prepared : 7-demethoxy-7-(4-azido-3- 125 I-benzyloxy)rapamycin (2) and its C 28 -C 29 seco analog 3. The key reactions of the synthesis were substitution of the C 7 methoxyl of rapamycin (1) with 4-azido-3-tributylstannylbenzyloxy group, exchange of tributyltin with 125 I using Na 125 I and Chloramine-T, and a ZnCl 2 mediated retro-Aldol cleavage of the C 28 -C 29 bond of rapamycin.

Direct, efficient and selective tritiations of paclitaxel and photoaffinity taxoids

Abstract Radiolabeled paclitaxel and three photophore-bearing derivatives were prepared by organoiridium-mediated direct tritium exchange under both catalytic and stoichiometric conditions. The resulting tritiated taxoids had specific activities ranging from 53 to 195 Ci/mmol.

Facile preparation of a 4-substituted [2,6-14C]pyridine: Synthesis of [14C]SK&F 105809

[ 14 C]Formaldehyde was used in a nucleophile-assisted iminium ion cyclization with N-benzyl-3-butynylamine to provide N-benzyl-4-iodo-1,2,5,6-tetrahydro[2,6- 14 C 2 ]pyridine. Palladium-catalyzed coupling of this vinyl iodide with the organozinc derivative 2 gave the corresponding 4-arylated tetrahydropyridine. Treatment of this compound at elevated temperatures with Pd/Al 2 O 3 in nitrobenzene solution caused hydrogenolysis of the benzyl group and aromatization, generating the 4-substituted [2,6- 14 C 2 ]pyridine 4 in good overall radiochemical yield from [ 14 C]formaldehyde. In high yields, compound 4 was converted via the methylsulfide [ 14 C]SK&F 105561 (1b) to the methylsulfinyl compound [ 14 C]SK&F 105809 (l#). It is proposed that, during the iminium ion cyclization, randomization of label between the 2- and 6-positions of the tetrahydropyridine ring occurs as the result of rapid equilibration between alkynyl and allenyl iminium ions, prior to cyclization.

Syntheses of E- and Z-pseudodiethylstilbestrol and Z-1-hydroxypseudodiethylstilbestrol.

Abstract The synthesis and characterization of E - and Z -3,4-bis(4-hydroxyphenyl)-2-hexene ( E - and Z -pseudo-DES) and of Z -3,4-bis(4-hydroxyphenyl)-2-hexen-1-ol ( Z -1-hydroxypseudo-DES) are described. These compounds are useful as probes in the study of hormone action.