Drug metabolism and disposition: the biological fate of chemicals, 1995
The metabolic fate of SK&F 107461 [Cbz-Ala-Ala-Phe psi [CHOHCH2] Gly-Val-Val-OMe], a potent and s... more The metabolic fate of SK&F 107461 [Cbz-Ala-Ala-Phe psi [CHOHCH2] Gly-Val-Val-OMe], a potent and specific inhibitor of the protease encoded by human immunodeficiency virus type 1, in male Sprague-Dawley rats is described. SK&F 107461 is a hexapeptide analog containing a hydroxyethylene linkage in place of one of the peptide bonds, and in which the amino terminus is blocked with a carbobenzyloxy group and the carboxy terminus is modified to a methyl ester. The major metabolites of SK&F 107461 found in bile and urine after intravenous administration of 3H-labeled compound were characterized by LC/MS using either thermospray or continuous flow/FAB models of ionization. Approximately 80% of the administered radioactivity was recovered in the bile of bile duct-exteriorized rats following an intravenous dose. Radiochromatographic profiling indicated that SK&F 107461 was subject to extensive biotransformation. Structures were determined for three major biliary and five major urinary metabol...
Introduction: The serotonin 1B (5-HT 1B) receptor has been implicated in several psychiatric diso... more Introduction: The serotonin 1B (5-HT 1B) receptor has been implicated in several psychiatric disorders and is a potential pharmacological target in the treatment of depression. The aim of this study was to develop a radioligand for positron emission tomography (PET) imaging of the 5-HT 1B receptor in the primate brain in vivo. Methods: Eight carboxamide radioligands (1-8) from three different core structures were radiolabeled with carbon-11 employing Nmethylation with [ 11 C]methyl triflate on the piperazine structural moiety. In vivo PET evaluation of each radioligand was performed in cynomolgus monkeys and included analysis of radioactive metabolites measured in plasma using high-performance liquid chromatography. Results: In a total of 12 radiosynthesis of the eight radioligands, the mean decay corrected yield was 11%, and the mean specific radioactivity was 299 GBq/μmol (8075 Ci/mmol) at time of administration. Of the eight tested candidates, [ 11 C]6 demonstrated the most promising in vivo characteristics, showing high binding in 5-HT 1B receptor-rich regions and low binding in the cerebellum. When inspecting data from all eight compounds, lipophilicity appeared as a physicochemical property that could be related to favorable in vivo imaging characteristics. Conclusion: Candidate [ 11 C]6, i.e., [ 11 C]AZ10419369, exhibited high binding potentials in regions known to contain 5-HT 1B receptors and was nominated for further preclinical characterization and PET examination in human subjects.
mM la (HI 7c 105 10 855 la (H) 8 136 8 18 827 Id (4-Me) 7 108 12 14 861 Id (4-Me) 8 99 10 13 848 ... more mM la (HI 7c 105 10 855 la (H) 8 136 8 18 827 Id (4-Me) 7 108 12 14 861 Id (4-Me) 8 99 10 13 848 le (4-Me01 7 86 14 900 le (4-Me01 8 78 10 902 The reaction was carried out in acetonitrile under oxygen at 60 "C for 20 h; 1, 1.0 M; vinyl ether, 2.0 M; FeCl,, 3.0 mM. Reaction for 10 h. Taken from the data in ref 4. also isolated by column chromatography on silica gel using hexane-ethyl acetate as eluant. Oxidative Coupling of NJV-Dimethylanilines 1 with Vinyl Ethers 7 and 8. A mixture of 1 (10 mmol) and a vinyl ether 7 or 8 (20 mmol) was stirred in the presence of FeC13 (0.03 mmol) under oxygen at 60 "C for 20 h. Then the mixture was poured into water, and the products were extracted with ether. After removal of the solvent and excess of 1 and the vinyl ether in vacuo, the coupling product was isolated by column chromatography on silica gel using hexane-ethyl acetate as eluant. Products. The purity of the following products isolated was judged to be 190% by GC and/or 'H and '9c NMR analyses. The dimerized products 4a,lNb 4b,la 5a,12b9c 5b,la and 61a are known and compared with authentic specimens. The dimer 4c was an oil;
Journal of Labelled Compounds and Radiopharmaceuticals, 1991
1‐(4‐Chloro‐[3‐3H]benzyl) ‐3‐(t‐butylthio)‐a, a‐dimethyl‐5‐(i‐propyl) ‐indole‐2‐propanoic acid (1... more 1‐(4‐Chloro‐[3‐3H]benzyl) ‐3‐(t‐butylthio)‐a, a‐dimethyl‐5‐(i‐propyl) ‐indole‐2‐propanoic acid (10, MK‐886) was prepared by catalytic tritium/halogen exchange on 1‐(4‐chloro‐3‐iodobenzyl)‐3‐(t‐butylthio)‐a,a ‐dimethyl‐5‐(i‐propyl)‐indole‐2‐propanoic acid (9). Compound 9 was prepared by a synthesis converging at the indole benzylation step. The required indole 4 was prepared by means of a Fischer indole synthesis employing the highly functionalized unsymmetrical ketone 3. Ketone 3 was efficiently made in three steps using epibromohydrin as a masked electrophilic acetone synthon. The halogenated benzyl bromide moiety 7 was prepared in three steps from 1‐chloro‐2‐iodo‐4‐(trifluoromethyl)‐benzene.
Journal of Labelled Compounds and Radiopharmaceuticals, 1990
Enantiomerically pure (2S,3R)‐3‐[(2‐carboxyethyl)thio]‐3‐[2‐(8‐phenyloctyl)phenyl]‐2‐hydroxy[2‐14... more Enantiomerically pure (2S,3R)‐3‐[(2‐carboxyethyl)thio]‐3‐[2‐(8‐phenyloctyl)phenyl]‐2‐hydroxy[2‐14C]propionic acid ([14C]SK&F 104353) was synthesized from methyl chloro[2‐14C]acetate via a five step sequence. Darzens Condensation with 2‐(8‐phenyloctyl)benzaldehyde gave a trans epoxy ester which underwent epoxide opening with methyl 3‐mercaptopropionate to furnish a pair of regioisomers. The desired isomer was isolated by subjecting the mixture to retroaldol cleavage conditions to remove the unwanted component. Subsequent optical resolution as a derivative of (S)‐proline and hydrolysis of the 2S,3R diastereomer afforded the title compound with a 5% overall radiochemical yield.
Journal of Labelled Compounds and Radiopharmaceuticals, 1990
Tritiated (S)‐10‐bromoacetamidomethylcamptothecin was prepared starting from (S)‐10‐hydroxycampto... more Tritiated (S)‐10‐bromoacetamidomethylcamptothecin was prepared starting from (S)‐10‐hydroxycamptothecin. The key step consisted of palladium catalyzed direct tritium exchange on the intermediate (S)‐10‐aminomethylcamptothecin. 3H NMR spectroscopy indicated the tritium label was located exclusively at the C‐5 position.
Journal of Labelled Compounds and Radiopharmaceuticals, 1988
The compound 6‐chloro‐2,3,4,5‐tetrahydro‐3‐methyl‐1H‐3‐benzazepine (SK&F 86466) was prepared in p... more The compound 6‐chloro‐2,3,4,5‐tetrahydro‐3‐methyl‐1H‐3‐benzazepine (SK&F 86466) was prepared in phenyl‐U‐14C and phenyl‐13C6 labeled forms in a six step sequence beginning with the appropriately labeled benzenes. In addition, the N‐desmethyl analog of the carbon‐14 labeled isotopomer and the N‐methyl‐2H3 derivative of the carbon‐13 isotopomer were prepared via the N‐(2,2,2‐trichloroethyl) carbamates by hydrolysis and lithium aluminum deuteride reduction, respectively.
Journal of Labelled Compounds and Radiopharmaceuticals, 1987
Two amino acids, t‐BOC‐O‐ethyl‐D‐tyrosine and t‐BOC‐phenylalanine, have been synthesized in triti... more Two amino acids, t‐BOC‐O‐ethyl‐D‐tyrosine and t‐BOC‐phenylalanine, have been synthesized in tritium labeled form via exchange with tritium gas over catalyst on an unlabeled precursor and dehydrohalogenation on an iodinated precursor respectively. The tyrosine derivative has been obtained in specific activities of 4 ‐ 7 Ci/mmol; tritium NMR indicates that at least 80% of the tritium resides in the benzylic position of the molecule. The phenylalanine has been synthesized with a specific activity of greater than 35 Ci/mmol. Tritium NMR confirms specific tritium/iodine replacement in the position.
A rapid, high-throughput radiometric assay for HIV-1 protease has been developed using ion-exchan... more A rapid, high-throughput radiometric assay for HIV-1 protease has been developed using ion-exchange chromatography performed in 96-well filtration plates. The assay monitors the activity of the HIV-1 protease on the radiolabeled form of a heptapeptide substrate, [tyrosyl-3,5-3H]Ac-Ser-Gln-Asn-Tyr-Pro-Val-Val-NH2, which is based on the p17-p24 cleavage site found in the viral polyprotein substrate Pr55gag. Specific cleavage of this uncharged heptapeptide substrate by HIV-1 protease releases the anionic product [tyrosyl-3,5-3H]Ac-Ser-Gln-Asn-Tyr, which is retained upon minicolumns of the anion-exchange resin AG1-X8. Protease activity is determined from the recovery of this radiolabeled product following elution with formic acid. This facile and highly sensitive assay may be utilized for steady-state kinetic analysis of the protease, for measurements of enzyme activity during its purification, and as a routine assay for the evaluation of protease inhibitors from natural product or synthetic sources.
Drug metabolism and disposition: the biological fate of chemicals, 1995
The metabolic fate of SK&F 107461 [Cbz-Ala-Ala-Phe psi [CHOHCH2] Gly-Val-Val-OMe], a potent and s... more The metabolic fate of SK&F 107461 [Cbz-Ala-Ala-Phe psi [CHOHCH2] Gly-Val-Val-OMe], a potent and specific inhibitor of the protease encoded by human immunodeficiency virus type 1, in male Sprague-Dawley rats is described. SK&F 107461 is a hexapeptide analog containing a hydroxyethylene linkage in place of one of the peptide bonds, and in which the amino terminus is blocked with a carbobenzyloxy group and the carboxy terminus is modified to a methyl ester. The major metabolites of SK&F 107461 found in bile and urine after intravenous administration of 3H-labeled compound were characterized by LC/MS using either thermospray or continuous flow/FAB models of ionization. Approximately 80% of the administered radioactivity was recovered in the bile of bile duct-exteriorized rats following an intravenous dose. Radiochromatographic profiling indicated that SK&F 107461 was subject to extensive biotransformation. Structures were determined for three major biliary and five major urinary metabol...
Introduction: The serotonin 1B (5-HT 1B) receptor has been implicated in several psychiatric diso... more Introduction: The serotonin 1B (5-HT 1B) receptor has been implicated in several psychiatric disorders and is a potential pharmacological target in the treatment of depression. The aim of this study was to develop a radioligand for positron emission tomography (PET) imaging of the 5-HT 1B receptor in the primate brain in vivo. Methods: Eight carboxamide radioligands (1-8) from three different core structures were radiolabeled with carbon-11 employing Nmethylation with [ 11 C]methyl triflate on the piperazine structural moiety. In vivo PET evaluation of each radioligand was performed in cynomolgus monkeys and included analysis of radioactive metabolites measured in plasma using high-performance liquid chromatography. Results: In a total of 12 radiosynthesis of the eight radioligands, the mean decay corrected yield was 11%, and the mean specific radioactivity was 299 GBq/μmol (8075 Ci/mmol) at time of administration. Of the eight tested candidates, [ 11 C]6 demonstrated the most promising in vivo characteristics, showing high binding in 5-HT 1B receptor-rich regions and low binding in the cerebellum. When inspecting data from all eight compounds, lipophilicity appeared as a physicochemical property that could be related to favorable in vivo imaging characteristics. Conclusion: Candidate [ 11 C]6, i.e., [ 11 C]AZ10419369, exhibited high binding potentials in regions known to contain 5-HT 1B receptors and was nominated for further preclinical characterization and PET examination in human subjects.
mM la (HI 7c 105 10 855 la (H) 8 136 8 18 827 Id (4-Me) 7 108 12 14 861 Id (4-Me) 8 99 10 13 848 ... more mM la (HI 7c 105 10 855 la (H) 8 136 8 18 827 Id (4-Me) 7 108 12 14 861 Id (4-Me) 8 99 10 13 848 le (4-Me01 7 86 14 900 le (4-Me01 8 78 10 902 The reaction was carried out in acetonitrile under oxygen at 60 "C for 20 h; 1, 1.0 M; vinyl ether, 2.0 M; FeCl,, 3.0 mM. Reaction for 10 h. Taken from the data in ref 4. also isolated by column chromatography on silica gel using hexane-ethyl acetate as eluant. Oxidative Coupling of NJV-Dimethylanilines 1 with Vinyl Ethers 7 and 8. A mixture of 1 (10 mmol) and a vinyl ether 7 or 8 (20 mmol) was stirred in the presence of FeC13 (0.03 mmol) under oxygen at 60 "C for 20 h. Then the mixture was poured into water, and the products were extracted with ether. After removal of the solvent and excess of 1 and the vinyl ether in vacuo, the coupling product was isolated by column chromatography on silica gel using hexane-ethyl acetate as eluant. Products. The purity of the following products isolated was judged to be 190% by GC and/or 'H and '9c NMR analyses. The dimerized products 4a,lNb 4b,la 5a,12b9c 5b,la and 61a are known and compared with authentic specimens. The dimer 4c was an oil;
Journal of Labelled Compounds and Radiopharmaceuticals, 1991
1‐(4‐Chloro‐[3‐3H]benzyl) ‐3‐(t‐butylthio)‐a, a‐dimethyl‐5‐(i‐propyl) ‐indole‐2‐propanoic acid (1... more 1‐(4‐Chloro‐[3‐3H]benzyl) ‐3‐(t‐butylthio)‐a, a‐dimethyl‐5‐(i‐propyl) ‐indole‐2‐propanoic acid (10, MK‐886) was prepared by catalytic tritium/halogen exchange on 1‐(4‐chloro‐3‐iodobenzyl)‐3‐(t‐butylthio)‐a,a ‐dimethyl‐5‐(i‐propyl)‐indole‐2‐propanoic acid (9). Compound 9 was prepared by a synthesis converging at the indole benzylation step. The required indole 4 was prepared by means of a Fischer indole synthesis employing the highly functionalized unsymmetrical ketone 3. Ketone 3 was efficiently made in three steps using epibromohydrin as a masked electrophilic acetone synthon. The halogenated benzyl bromide moiety 7 was prepared in three steps from 1‐chloro‐2‐iodo‐4‐(trifluoromethyl)‐benzene.
Journal of Labelled Compounds and Radiopharmaceuticals, 1990
Enantiomerically pure (2S,3R)‐3‐[(2‐carboxyethyl)thio]‐3‐[2‐(8‐phenyloctyl)phenyl]‐2‐hydroxy[2‐14... more Enantiomerically pure (2S,3R)‐3‐[(2‐carboxyethyl)thio]‐3‐[2‐(8‐phenyloctyl)phenyl]‐2‐hydroxy[2‐14C]propionic acid ([14C]SK&F 104353) was synthesized from methyl chloro[2‐14C]acetate via a five step sequence. Darzens Condensation with 2‐(8‐phenyloctyl)benzaldehyde gave a trans epoxy ester which underwent epoxide opening with methyl 3‐mercaptopropionate to furnish a pair of regioisomers. The desired isomer was isolated by subjecting the mixture to retroaldol cleavage conditions to remove the unwanted component. Subsequent optical resolution as a derivative of (S)‐proline and hydrolysis of the 2S,3R diastereomer afforded the title compound with a 5% overall radiochemical yield.
Journal of Labelled Compounds and Radiopharmaceuticals, 1990
Tritiated (S)‐10‐bromoacetamidomethylcamptothecin was prepared starting from (S)‐10‐hydroxycampto... more Tritiated (S)‐10‐bromoacetamidomethylcamptothecin was prepared starting from (S)‐10‐hydroxycamptothecin. The key step consisted of palladium catalyzed direct tritium exchange on the intermediate (S)‐10‐aminomethylcamptothecin. 3H NMR spectroscopy indicated the tritium label was located exclusively at the C‐5 position.
Journal of Labelled Compounds and Radiopharmaceuticals, 1988
The compound 6‐chloro‐2,3,4,5‐tetrahydro‐3‐methyl‐1H‐3‐benzazepine (SK&F 86466) was prepared in p... more The compound 6‐chloro‐2,3,4,5‐tetrahydro‐3‐methyl‐1H‐3‐benzazepine (SK&F 86466) was prepared in phenyl‐U‐14C and phenyl‐13C6 labeled forms in a six step sequence beginning with the appropriately labeled benzenes. In addition, the N‐desmethyl analog of the carbon‐14 labeled isotopomer and the N‐methyl‐2H3 derivative of the carbon‐13 isotopomer were prepared via the N‐(2,2,2‐trichloroethyl) carbamates by hydrolysis and lithium aluminum deuteride reduction, respectively.
Journal of Labelled Compounds and Radiopharmaceuticals, 1987
Two amino acids, t‐BOC‐O‐ethyl‐D‐tyrosine and t‐BOC‐phenylalanine, have been synthesized in triti... more Two amino acids, t‐BOC‐O‐ethyl‐D‐tyrosine and t‐BOC‐phenylalanine, have been synthesized in tritium labeled form via exchange with tritium gas over catalyst on an unlabeled precursor and dehydrohalogenation on an iodinated precursor respectively. The tyrosine derivative has been obtained in specific activities of 4 ‐ 7 Ci/mmol; tritium NMR indicates that at least 80% of the tritium resides in the benzylic position of the molecule. The phenylalanine has been synthesized with a specific activity of greater than 35 Ci/mmol. Tritium NMR confirms specific tritium/iodine replacement in the position.
A rapid, high-throughput radiometric assay for HIV-1 protease has been developed using ion-exchan... more A rapid, high-throughput radiometric assay for HIV-1 protease has been developed using ion-exchange chromatography performed in 96-well filtration plates. The assay monitors the activity of the HIV-1 protease on the radiolabeled form of a heptapeptide substrate, [tyrosyl-3,5-3H]Ac-Ser-Gln-Asn-Tyr-Pro-Val-Val-NH2, which is based on the p17-p24 cleavage site found in the viral polyprotein substrate Pr55gag. Specific cleavage of this uncharged heptapeptide substrate by HIV-1 protease releases the anionic product [tyrosyl-3,5-3H]Ac-Ser-Gln-Asn-Tyr, which is retained upon minicolumns of the anion-exchange resin AG1-X8. Protease activity is determined from the recovery of this radiolabeled product following elution with formic acid. This facile and highly sensitive assay may be utilized for steady-state kinetic analysis of the protease, for measurements of enzyme activity during its purification, and as a routine assay for the evaluation of protease inhibitors from natural product or synthetic sources.
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Papers by Richard Heys