Synthesis of pyrimido[1,4]diazepin‐2‐one analogs and their evaluation as anticonvulsant agents

5‐Benzyloxycarbonylaminomethylcarbonyl(N‐methyl)amino‐4‐[2‐chloro(2‐fluoro or 2‐hydrogen)benzoyl]pyrimidines (compound 14 ) in which the chlorophenyl moiety of dipeptidoaminochlorobenzophenones ( 1 ) is replaced by a pyrimido ring, and 1,3‐dihydro‐1‐methyl‐5‐[2‐chloro (2‐fluoro or 2‐hydrogen)phenyl]‐2H‐pyrimido[5,4‐e][1,4]diazepin‐2‐ones ( 16 ) in which the chlorophenyl moiety of 7‐chloro‐5‐aryl‐benzo[1,4]diazepin‐2‐one ( 3 ) is replaced by a pyrimido ring, were synthesized and evaluated as anticonvulsants by using the subcutaneous metrazol‐ (Met) and maximal electroshock– (MES) induced seizure screening tests. Structure‐activity studies showed these two classes of compounds ( 14, 16 ) are generally more potent in the Met screen relative to the MES screen. The effect which the nature of the benzoyl C‐4 ortho‐substituent (Cl, F, H) in compound 14 , or the ortho‐phenyl C‐5 substituent (Cl, F. H) in compounds 16 , has upon anticonvulsant activity was small with the potency profile generally being Cl ≅ F > H. It is proposed that 5‐benzyloxycarbonylaminocarbonyl(N‐methyl)amino‐4‐(2‐fluorobenzoyl)pyrimidine ( 14b ) may act as a prodrug, at least in part, to 1,3‐dihydro‐1‐methyl‐5‐(2‐fluorophenyl)‐2H‐pyrimido[5,4‐e][1,4]diazepin‐2‐one ( 16b ), because 14b does not bind to the benzodiazepine receptor binding site(s), yet it is approximately equipotent to 16b in the Met and MES screens. Compounds 14b and 16b are less active than clonazepam but more active than valproic acid in the Met screen, and less active than phenytoin but more active than clonazepam and valproic acid in the MES screen. Drug Dev. Res. 46:155–162, 1999. © 1999 Wiley‐Liss, Inc.     

Synthesis of C‐14 and C‐13, H‐2‐labeled IKK inhibitor: [14C] and [13C4,D3]‐N‐(6‐chloro‐7‐methoxy‐9H‐pyrido[3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide

[¹⁴C]‐N‐(6‐Chloro‐7‐methoxy‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide (5B ), an IKK inhibitor, was synthesized from [¹⁴C]‐barium carbonate in two steps in an overall radiochemical yield of 41%. The intermediate, [carboxyl‐¹⁴C]‐2‐methylnicotinic acid, was prepared by the lithiation and carbonation of 3‐bromo‐2‐methylpyridine. [¹³C₄,D₃]‐N‐(6‐chloro‐7‐methoxy‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐2‐methyl‐3‐pyridinecarboxamide (5C ) was synthesized from [1,2,3,4‐¹³C₄]‐ethyl acetoacetate and [D₄]‐methanol in six steps in an overall yield of 2%. [¹³C₄]‐2‐methylnicotic acid, was prepared by condensation of [¹³C₄]‐ethyl 3‐aminocrotonate and acrolein, followed by hydrolysis with lithium hydroxide. Copyright © 2006 John Wiley & Sons, Ltd.     

The synthesis of [1‐14C]2‐(1H‐tetrazol‐5‐yl)acetic acid

Tetrazoles are a common heterocyclic functionality in many biologically active molecules. [1‐¹⁴C]2‐(1H‐Tetrazol‐5‐yl)acetic acid was required as an intermediate in the synthesis of a development candidate as part of a discovery phase program to complete metabolic profiling studies. [1‐¹⁴C]2‐(1H‐Tetrazol‐5‐yl)acetic acid was prepared in 4 steps overall and in 3 radiochemical steps from K¹⁴CN in an overall 32% radiochemical yield.     

Synthesis of C‐14‐labeled novel IKK inhibitor: 2‐[14C]‐N‐(6‐chloro‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐3‐pyridinecarboxamide

2‐[¹⁴C]‐N‐(6‐Chloro‐9H‐pyrido [3,4‐b]indol‐8‐yl)‐3‐pyridinecarboxamide (9A , also referred to as [¹⁴C]‐PS‐1145) was synthesized from [¹⁴C]‐paraformaldehyde in five steps in an overall radiochemical yield of 15%. The key intermediate 1‐[¹⁴C]‐6‐chloro‐1,2,3,4‐tetrahydro‐β‐carboline was obtained by Pictet–Spengler cyclization of chlorotryptamine with [¹⁴C]‐paraformaldehyde. Similar reactions were conducted with tryptamine to address the generality of the methodology. Copyright © 2005 John Wiley & Sons, Ltd.     

Highly efficient preparation of carbon‐14 labeled,auxin herbicide 4‐amino‐3,5,6‐trichloropicolinic acid

A highly efficient, seven‐step route has been developed for the preparation of 2,6‐[¹⁴C₂]‐4‐amino‐3,5,6‐trichloropicolinic acid ([¹⁴C₂]‐ 1 , 2,6‐[¹⁴C₂]‐picloram) from 2,6‐[¹⁴C₂]‐pentachloropyridine. The method involves the stepwise, highly selective and high yield introduction of amino and carboxylic acid groups to the 4‐ and 2‐positions, respectively, of pentachloropyridine affording [¹⁴C₂]‐ 1 in an overall radiochemical yield of >70% with the use of only one formal purification step. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and biological evaluation of constrained analogues of the opioid peptide H‐Tyr‐d‐Ala‐Phe‐Gly‐NH2 using the 4‐amino‐2‐benzazepin‐3‐one scaffold

Abstract: The synthesis of conformationally restricted dipeptidic moieties 4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one (Aba)‐Gly ([(4S)‐amino‐3‐oxo‐1,2,4,5‐tetrahydro‐1H‐2‐benzazepin‐2‐yl]‐acetic acid) and 8‐hydroxy‐4‐amino‐1,2,4,5‐tetrahydro‐2‐benzazepin‐3‐one (Hba)‐d ‐Ala ([(4S)‐amino‐8‐hydroxy‐3‐oxo‐1,2,4,5‐tetrahydro‐benzo[c]azepin‐2‐yl]‐propionic acid) was based on a synthetic strategy that uses an oxazolidinone as an N‐acyliminium precursor. Introducing these Aba scaffolds into the N‐terminal tetrapeptide of dermorphin (H‐Tyr‐d ‐Ala‐Phe‐Gly‐Tyr‐Pro‐Ser‐NH₂)‐induced remarkable shifts in affinity and selectivity towards the opioid μ‐ and δ‐receptors. This paper provides the synthesis and biological in vitro and in vivo evaluation of constricted analogues of the N‐terminal tetrapeptide H‐Tyr‐d ‐Ala‐Phe‐Gly‐NH₂, which is the minimal subunit of dermorphin needed for dermorphin‐like opiate activity.     

Biological evaluation of new [18F]F‐labeled synthetic amino acid derivatives as oncologic radiotracers

The present study evaluated the tumoral uptake of the novel synthetic amino acid positron emission tomography (PET) tracers (S)‐2‐amino‐3‐(4‐([¹⁸F]fluoromethyl)‐1H‐1,2,3‐triazol‐1‐yl)propanoic acid (AMC‐101), (S)‐2‐amino‐4‐(4‐([¹⁸F]fluoromethyl)‐1H‐1,2,3‐triazol‐1‐yl)butanoic acid (AMC‐102), and (S)‐2‐amino‐5‐(4‐([¹⁸F]fluoromethyl)‐1H‐1,2,3‐triazol‐1‐yl)pentanoic acid (AMC‐103), all of which are (S)‐2‐amino‐(4‐([¹⁸F]fluoromethyl)‐1H‐1,2,3‐triazol‐1‐yl)alkyl acids. In vitro cellular uptake was investigated using the rat glioma cell lines 9L and C6. In vitro competitive inhibition tests were performed to identify the involvement of specific amino acid transporters. In vivo dynamic PET images of 9L xenograft tumor‐bearing model mice were acquired over 2 h after AMC administration. [¹⁸F]FDOPA PET studies were performed with and without S‐carbidopa pretreatment for comparison. All three AMCs exhibited good in vitro cell uptake through the L and alanine‐serine‐cysteine transporters and enabled clear tumor visualization on PET, leaving the brain devoid of the tracer. Thirty minutes after injection, the mean tumor standardized uptake values were 1.59 ± 0.05, 1.89 ± 0.27, and 1.74 ± 0.13 for AMC‐101, AMC‐102, and AMC‐103, respectively. Although the tumor uptake values of AMCs were lower than that of [¹⁸F]FDOPA with S‐carbidopa pretreatment, AMCs enabled higher contrast images with lower background activity compared with [¹⁸F]FDOPA with S‐carbidopa pretreatment. Our results indicate the potential uses of these new synthetic amino acids as oncologic radiotracers.     

Synthesis of isotope‐labeled HSP90 inhibitor: [13CD3] and [14C]‐TAK‐459

[¹³CD₃]‐TAK‐459 (1A), an HSP90 inhibitor, was synthesized from [¹³CD₃]‐sodium methoxide in three steps in an overall yield of 29%. The key intermediate [¹³CD₃]‐2‐methoxy‐6‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)pyridine was synthesized in two steps from 2,6‐dibromopyridine and stable isotope‐labeled sodium methoxide. [¹⁴C]‐TAK‐459 (1B) was synthesized from [¹⁴C(U)]‐guanidine hydrochloride in five steps in an overall radiochemical yield of 5.4%. The key intermediate, [¹⁴C]‐(R)‐2‐amino‐7‐(2‐bromo‐4‐fluorophenyl)‐4‐methyl‐7,8‐dihydropyrido[4,3‐d]pyrimidin‐5(6H)‐one, was prepared by microwave‐assisted condensation.     

Synthesis of three alpha 7 agonists in labeled form

In support of a program to develop an alpha 7 agonist as a treatment for Alzheimer's disease, three drug candidates, 1, 2, and 3, were prepared in labeled forms. Compound 1 was prepared in C‐14 labeled form by lithiation of [2,6‐¹⁴C₂]2‐chloropyridine and subsequent coupling with spirooxirane‐2,3'‐quinuclidine. When this same coupling was attempted using [3,4,5,6‐²H₄]2‐chloropyridine, alcohol [²H₆]‐6 was the major product indicating that the primary isotope effect for the lithiation step was significant enough to shift the reaction pathway. Therefore, an alternate site of labeling was used to prepare [²H₄]‐1. [¹³C₅]‐2 was prepared in five steps from [¹³C₅]2‐furoic acid, but the C‐14 labeled compound used [¹⁴C₂]‐1 as the starting material instead. [¹⁴C₂]‐3 was prepared in two steps from [carbonyl‐¹⁴C]nicotinic acid.     

An improved synthesis of [24‐14C]cholic acid,and its application to the synthesis of [14C]SCH 209702 (Syn3). Synthesis of [2H8]SCH 209702

An efficient synthesis of [24‐¹⁴C]cholic acid from potassium [¹⁴C]cyanide has been developed. The key intermediate, 23‐chloro‐3α, 7α, 12α‐triformyloxynorcholane, was synthesized by degradation of triformyl protected cholic acid. Different degradation conditions were explored. The synthesis of [¹⁴C]SCH 209702 from 23‐chloro‐3α, 7α, 12α‐triformyloxynorcholane and potassium [¹⁴C]cyanide is described. The synthesis of [²H₈]SCH 209702 from [²H₄]cholic acid is also presented. Copyright © 2008 John Wiley & Sons, Ltd.     

Efficient regioselective three-component domino synthesis of 3-(1,2,4-Triazol-5-yl)-1,3-thiazolidin-4-ones as potent antifungal and antituberculosis agents

In research for promising antibacterial and antifungal compounds, a series of 2‐aryl 3‐[1,2,4]triazol‐5‐yl 4‐thiazolidinones 1 were synthesized by a domino reaction of 5‐amino‐1H‐[1,2,4]triazoles 3 , aromatic aldehydes, and α‐mercaptoacids in boiling toluene in the presence of molecular sieves 4 Å. Of the twenty novel 3‐[1,2,4]triazol‐5‐yl 4‐thiazolidinone derivatives, four compounds 2‐benzo[d][1,3]dioxol‐6‐yl‐3‐[(3‐morpholin‐4‐yl)‐1H‐1,2,4‐triazol‐5‐yl)]‐1,3‐thiazolidin‐4‐one ( 1i ), 2‐(4‐chlorophenyl)‐5‐methyl‐3‐[3‐(4‐methylpiperazin‐1‐yl)‐1H‐1,2,4‐triazol‐5‐yl]‐1,3‐thiazolidin‐4‐one ( 1p ), 2‐benzo[d][1,3]dioxol‐6‐yl‐3‐[3‐(4‐methylpiperazin‐1‐yl)‐1H‐1,2,4‐triazol‐5‐yl]‐1,3‐thiazolidin‐4‐one ( 1s ), 2‐benzo[d][1,3]dioxol‐6‐yl‐5‐methyl‐3‐[3‐(4‐methylpiperazin‐1‐yl)‐1H‐1,2,4‐triazol‐5‐yl]‐1,3‐thiazolidin‐4‐one ( 1t ) exhibited MICs of 4 µg/mL or less versus Mycobacterium tuberculosis. Moreover, these compounds were screened against Candida albicans. Compounds 1p , 1s gave MICs of 1 µg/mL or less, and were fungicidal. Finally, compound 1s was evaluated against an expanded fungal panel and showed good activity against Cryptococcus neoformans. In addition, compound 1s also appeared to be fungicidal against Aspergillus arrhizus, with MIC <1 µg/mL.     

Synthesis of a delta opioid agonist in [2H6], [2H4], [11C], and [14C] labeled forms

In support of a program to develop a treatment for depression, four labeled forms of a delta opioid agonist were prepared. The [²H₄] labeled form was prepared using a relatively straightforward conversion of [²H₄]bromoethanol to [²H₄]N‐methyl‐2‐hydroxyethylamine. The key step in the synthesis of the [²H₆] labeled form involved the Pd‐catalyzed exchange in D₂O of 8‐quinolin‐8‐ol to give [²H₆] 8‐quinolin‐8‐ol. The C‐14 labeled form was synthesized in one step using [¹⁴C]carbonylation, and the C‐11 labeled form was prepared in two steps from ¹¹CH₃I. Copyright © 2011 John Wiley & Sons, Ltd.     

Multiple labeling of a potent CX3CR1 antagonist for the treatment of multiple sclerosis

Several methods for the preparation of five isotopologues of the CX₃CR1 antagonist 1 were developed. Volatile and radioactive 1‐chloro‐ and 1‐bromo‐ethyl‐benzene was handled in [2′‐¹⁴C] and [3′, 5′‐³H] labeling of 1. d ‐Leucinol ((R)‐2‐amino‐4‐methylpentan‐1‐ol) was labeled as [1‐¹⁴C] and [4‐¹⁴C] via a Wittig reaction using Garner's aldehyde and a Strecker amino acid synthesis with d ‐acylase resolvation, respectively. A [²H₁₀]d ‐leucinol was used for the stable labeled [M + 10] isotopologue. The products were isolated with 97.6–100% stereo chemical and radiochemical purity as for specific activity 768 GBq/mmol and 1.6–2.0 GBq/mmol, respectively.     

Synthesis of 14C‐labelled myosmine, [2′‐14C] ‐3‐(1‐pyrrolin‐2‐yl)pyridine

¹⁴C‐Labelled myosmine ([2′‐¹⁴C]‐3‐(1‐pyrrolin‐2‐yl)pyridine) was synthesized for autoradiography studies starting from [carboxyl‐¹⁴C]‐nicotinic acid by initial esterification of the latter in the presence of 1,1,1‐triethoxyethane. Without any purification the ethyl nicotinate formed was directly reacted with N‐vinyl‐2‐pyrrolidinone in the presence of sodium hydride, yielding ¹⁴C‐labelled myosmine. The product was purified by silica gel column chromatography. The radiochemical yield was 15% and the specific activity 55.2 mCi/mmol. Copyright © 2003 John Wiley & Sons, Ltd.     

Syntheses of [14C] and [2H4]PD0205520, an inhibitor of the tyrosine kinase activity of the epidermal growth factor receptor

5‐(4‐Methyl‐piperazin‐1‐yl)‐pent‐2‐ynoic acid [4‐(3‐chloro‐4‐fluoro‐phenylamino)‐pyrido[3,4‐d]pyrimidin‐6‐yl]‐amide, PD0205520, was under investigation as a potential inhibitor of the tyrosine kinase (TK) activity of the epidermal growth factor receptor (EGFR) for cancer treatment. Both radio‐ and stable‐isotope‐labeled compounds were required for drug absorption, distribution, metabolism and excretion (ADME) and quantitative mass spectrometry bio‐analytical studies. PD0205520 ^I4C‐labeled in the pyrimidine ring system was prepared in seven steps in an overall radiochemical yield of 26% from [¹⁴C]thiourea. PD0205520 ²H‐Iabeled in the piperazine ring was synthesized in four steps in a 32% overall yield. Copyright © 2005 John Wiley & Sons, Ltd.     

A facile synthesis of [14C]pyrithiobac‐sodium

Condensation of thiourea 1 with diethyl malonate 2 in the presence of sodium methoxide furnished 4,6‐dihydroxy‐2‐mercaptopyrimidine 3 . Compound 3 on methylation with diazomethane followed by oxidation with H₅IO₆/CrO₃ in ethyl acetate gave 4,6‐dimethoxy‐2‐methylsulphonylpyrimidine 5 . Compound 5 on condensation with 2‐mercapto‐6‐chlorobenzoic acid in the presence of a phase transfer catalyst, tetrabutylammonium bromide and sodium carbonate gave the title compound – pyrithiobac‐sodium 6 with an overall yield of > 35% starting from thiourea. Following the above standardized procedure, using [¹⁴C]‐thiourea in lieu of thiourea, ¹⁴C labelled product 6 , was synthesized with an overall radiochemical yield > 30% (with respect to [¹⁴C]‐thiourea) for further evaluations of environmental fate of 6 , in soils and plants. Copyright © 2006 John Wiley & Sons, Ltd.     

The synthesis of [14C]4‐acetylphenylalanine,effect on cell viability,and assessment of protein incorporation in male rat hepatocytes

PEGylation is a proven approach to prolonging the duration of action and enhancing biophysical solubility and stability of peptides. 4‐Acetylphenylalanine is a novel amino acid with a ketone side chain that is uniquely reactive in proteins. The ketone functionality can react with an aminooxy functionalized polyethyleneglycol polymer to form a stable oxime adduct of the protein. One concern with using unnatural amino acids, such as 4‐acetylphenylalanine, is the possibility of it being cleaved from the peptide and becoming incorporated into endogenous proteins. To determine whether this occurs, an in vitro experiment to assess the cell viability and amino acid incorporation into endogenous proteins using primary male rat hepatocytes in the presence of [¹⁴C]4‐acetylphenylalanine, 4 or [¹⁴C(U)]L‐phenylalanine was conducted. [¹⁴C]4‐acetylphenylalanine, 4 was prepared in 2 radiochemical steps from [1‐¹⁴C]acetyl chloride in an overall 8% radiochemical yield and in 99.9% radiochemical purity. The results showed that there was no evidence of carbon‐14 incorporation into hepatocyte endogenous proteins with [¹⁴C]pAcF and there was no difference between it and L‐phenylalanine in cell viability assessments at any of the concentrations studied between 0.1 and 1000 μM.     

Synthesis of N‐(2‐chloro‐3,4‐dimethoxybenzylideneamino)guanidinium acetate [α‐14C]

¹⁴C‐Labelled N‐(2‐chloro‐3,4‐dimethoxybenzylideneamino)guanidinium acetate has been synthesized as a part of a four‐step procedure which involved decarboxylation of 2‐chloro‐3,4‐dimethoxybenzoic acid by Pb(OAc)₄ to give 2‐chloro‐3,4‐dimethoxy‐1‐iodobenzene, followed by a selective lithiation at the iodine position and electrophilic substitution with N,N‐dimethylformamide [α‐¹⁴C] and final reaction with aminoguanidine bicarbonate. The specific activity was 59 mCi/mmol and the overall yield 49%. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and Biological Activity of Some 1,3‐Dihydro‐2H‐3‐benzazepin‐2‐ones with a Piperazine Moiety as Bradycardic Agents

A series of 1,3‐dihydro‐2H‐3‐benzazepin‐2‐ones with a piperazine moiety were designed and synthesized by treating the common intermediate of 1,3‐dihydro‐7,8‐dimethoxy‐3‐[3‐(1‐piperazinyl)propyl]‐2H‐3‐benzazepin‐2‐ones with a variety of N‐aryl‐2‐chloroacetamides and acyl chlorides. Their structures have been characterized by ¹H‐NMR, MS, and elemental analysis. The title compounds were evaluated for their bradycardic activity in vitro. Most of the synthesized compounds exhibited some vasorelaxant activity and heart‐rate‐reducing activity with bradycardic potency.     

Synthesis of [3H]ABT‐518, a matrix metalloproteinase inhibitor (MMPI) labeled in the phenyl rings

A novel matrix metalloproteinase inhibitor, ABT‐518, [S‐(R^*, R^*)]‐N‐[1‐(2, 2‐dimethyl‐1,3‐dioxol‐4‐yl)‐2‐[[4‐[4‐(trifluoromethoxy)‐phenoxy]phenyl]sulfonyl]ethyl]‐N‐hydroxyformamide, was labeled with tritium in two phenyl rings in a seven‐step synthesis. The overall radiochemical yield of [³H]ABT‐518 in seven steps starting from 1‐(methylsulfonyl)‐4‐[4‐(trifluoromethoxy)phenoxy]benzene was 6.2% with the radiochemical purity of 99.4%. Copyright © 2009 John Wiley & Sons, Ltd.