Synthesis and characterization of poly-O-methyl-[n]-polyurethane from a d-glucamine-based monomer

Aminoalditol 1-amino-1-deoxy-d-sorbitol (1) was readily converted into 2,3,4,5-tetra-O-methyl derivative 5, a key precursor of a sugar-based [n]-polyurethane. For the polymerization, the free amino or primary hydroxyl groups of 5 were selectively activated and employed as starting monomers in two alternative procedures. Thus, the amino function of 5 was converted into the isocyanate derivative by treatment with di-tert-butyltricarbonate, and polymerized in situ in the presence of Zr(IV) acetylacetonate. The resulting poly(1-amino-1-deoxy-2,3,4,5-tetra-O-methyl-d-sorbitol)urethane (8) had a moderate molecular weight and showed the presence of urea units. The alternative synthesis of 8 involved the activation of the free hydroxyl group of 5 as the corresponding phenylcarbonate. The polymerization of this α-amino-ω-phenylcarbonate alditol monomer does not require a metal catalyst. The resulting material exhibited an improved molecular weight and higher purity than that obtained via the isocyanate. [n]-polyurethane 8 was highly soluble in water as well as in common organic solvents (chloroform, acetone, ethyl acetate, etc) and was obtained as an amorphous material which was characterized thermally and spectroscopically.     

Synthesis of 9-[1-(substituted)-2-(phosphonomethoxy)ethyl]adenine derivatives as possible antiviral agents

Various C-1'-substituted acyclic N9 adenine nucleosides were prepared from 9-[(1-hydroxymethyl)(3-monomethoxytrityloxy)propyl]-N6-monomethoxytrityladenine. The hydroxymethyl was modified to the phosphonomethoxy derivative, and the 3-monomethoxytrityloxy was converted to hydroxyl, methoxy, azido, and amino. Other substituents, such as ethyl and ea-hydroxyethyl were also prepared. The resulting phosphonomethoxy derivatives were converted to prodrugs.     

Radiochemical synthesis of DL-canaline and the colorimetric assay of canaline

A procedure is available for the production of DL-[carboxy-14C]canaline from [14C]cyanide by reaction of ethyl N-hydroxyacetimidate and acrolein to form ethyl N-[3-oxopropoxy]acetimidate. The reaction product is converted to the nitrile and then to the hydantoin derivative of DL-canaline; alkaline hydrolysis produces the free amino acid (2-amino-4-aminooxypropionic acid). This procedure can be extended to the production of DL-[carboxy-14C]canavanine by guanidination of C-1-labeled DL-canaline with O-methylisourea. A markedly improved colorimetric assay for canaline has been achieved by a procedure involving carbamylation of canaline with cyanate to form O-ureidohomoserine (2-amino-4-ureidooxybutyric acid). Colorimetric analysis of the latter amino acid markedly enhances the sensitivity, reproducibility, and accuracy of the analysis of L-canaline from biological materials.     

Chemo- and stereoselective synthesis of benzocycloheptene and 1-benzoxepin derivatives as alpha-sympathomimetic and anorexigenic agents

The synthesis and pharmacological evaluation of cis- and trans-6-amino-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ols 4a-c and 5a-c and cis- and trans-4-amino-2,3,4,5-tetrahydro-1-benzoxepin-5-ols 4d-f and 5d-f were carried out. Chemo- and stereoselective synthesis of 5a-f was achieved by reduction of corresponding alpha-amino ketones 3a-f with LiAl(t-BuO)3H. cis-4-Amino-2,3,4,5-tetrahydro-1-benzoxepin-5-ol 4d and trans-4-amino-2,3,4,5-tetrahydro-1-benzoxepin-5-ol 5d exhibited marked anorexigenic activity in mice at a dose of LD50 800 and 500 mg/kg and ED50 75 and 55 mg/kg, respectively, while the analog cis-2,3-dihydroxy-6-amino-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol 8 showed typical alpha-sympathomimetic activity.     

Synthesis of polyhydroxy amino acids based on D- and L-alanine from D-glycero-D-gulo-heptono-1,4-lactone

2-Amino-2,3-dideoxy-D-manno-heptonic acid (7) has been synthesized from 2,5,6,7-tetra-O-acetyl-3-deoxy-D-gluco-heptono-1,4-lactone (1), which was readily prepared from D-glycero-D-gulo-heptono-1,4-lactone. O-Deacetylation of 1 followed by treatment with 13:1 (v/v) 2,2-dimethoxypropane/acetone in the presence of p-toluenesulfonic acid gave methyl 3-deoxy-4,5:6,7-di-O-isopropylidene-D-gluco-heptonate (3) as a crystalline product (80% yield). The free hydroxyl group (OH-2) of 3 was mesylated and substituted by azide to give the corresponding azide derivative 5. Hydrogenolysis and further hydrolysis of the ester function of 5 afforded alpha-amino acid 7 (43% overall yield from 1). Compound 7 is an analog of L-alanine having a polyhydroxy chain attached to C-3. The diastereoisomer of 7 at C-2, 2-amino-2,3-dideoxy-D-gluco-heptonic acid (12) was also prepared from 3, by a route that involved 2,3-dideoxy-2-iodo derivative 8 as a key intermediate.     

Synthesis of 9-[1-(substituted)-3-(phosphonomethoxy)propyl]adenine derivatives as possible antiviral agents

Acyclic N9 adenine nucleosides substituted at C-1' position were prepared by the Mitsunobu reaction of 1-tert-butyldimethylsilyl-4-pivaloylbutan-1,2,4-triol (5) with adenine. Pivaloyl hydroxyl was modified to the phosphonomethoxy derivatives, and the tert-butyldimethylsilyl hydroxyl was converted to methoxy, azido, amino, fluoro, and c-hydroxyethyl and was eliminated to give vinyl. The resulting phosphonic acids were converted to prodrugs also.     

Synthesis of imidazo[4,5-e][1,4]diazepine and 3-substituted 3-deazapurine nucleosides from 1-substituted inosines.

New synthetic methods of imidazo[4,5-e][1,4]diazepine nucleosides 8-11 and 3-substituted 3-deazainosines 14 from inosine have been reported. Treatment of N1-substituted inosines 1-3 with aqueous NaOH gave 5-amino-4-(N-substituted carbamoyl)imidazole ribosides 5-7, followed by appropriate manipulations to afford ring-expanded guanosine, inosine, and xanthosine analogues. Additionally, the 5-amino group of 4-N-allylcarbamoyl derivative 12 was converted into corresponding 5-iodo nucleoside 13. We found that 13 was cyclized to form 3-deaza-3-methylinosine (14) in the presence of Pd catalysts.     

A facile synthesis and anti-avian influenza virus (H5N1) screening of some novel pyrazolopyrimidine nucleoside derivatives

Treatment of 5-amino-1-(9-methyl-5,6-dihydronaphtho[1',2':4,5]thieno[2,3-d]pyrimidin-11-yl)-1H-pyrazole-4-carbonitrile (1) with formic acid afforded pyrazolo[3,4-d]pyrimidin-4-one derivative 2. The sodium salt of the latter compound (generated in situ) was treated with some alkyl halides to afford the corresponding N-substituted compounds 3-7. The siloxy derivative 8 (generated also in situ from 2) was ribosylated and glycosylated to yield compounds 9 and 11, respectively. Deprotection of compounds 9 and 11 in methanolic ammonia produced the free nucleosides 10 and 12, respectively. Moreover, the prepared compounds were tested for antiviral activity against H5N1 virus [A/chicken/Egypt/1/2006] and some of them revealed moderate results compared with the other tested compounds.     

Molecular amplifiers: synthesis and functionalization of a poly(aminopropyl)dextran bearing a uniquely reactive terminus for univalent attachment to biomolecules.

The synthesis and characterization of the versatile dextran-based molecular amplifier 6 is described. Dextran (Mr = 40,200) was selectively monofunctionalized in high yield at its reducing terminus via reductive amination with 2-(4-nitrophenyl)ethylamine to give 1. The nitro group in 1 serves as a masked amino group which is eventually converted into a reactive isothiocyanato group used for monovalent attachment of the completed assembly to a target molecule. Cyanoethylation of 1 gave the terminally nitrophenylated poly(cyanoethyl)dextran 5 which was selectively reduced to the corresponding poly(aminopropyl) derivative 6 with BH3.THF, a reagent which preserved the end nitro group. Conjugation of amplifier 6 with the isothiocyanate-derivatized Gd(III) chelate 7 gave conjugate 9 containing about 22 mol of chelate/mol of amplifier. The T1 relaxivity per Gd(III) ion of 9 in H2O was 15.0 mM-1 s-1, about 3-fold higher than that of free Gd(III)DTPA in H2O. The nitro group of 9 was then selectively reduced to the corresponding amine 10, which was converted into isothiocyanate 11. The reactivity of the single isothiocyanate group in 11 was demonstrated by coupling to 5-aminoeosin, giving conjugate 12. Amplifier 6 was also conjugated with the acid-labile N-cis-aconityl derivative 8 of the potent anticancer agent daunomycin. The nitro group of the resulting conjugate 13 was then reduced and the resulting amine 14 was converted into mono isothiocyanate 15. Compound 15 reacted with a water-insoluble amine-containing solid support to give 16. Free daunomycin was released from 16 by exposure to citrate-phosphate buffer at pH 4.0.     

Binuclear copper(II) complexes of 5-N-(beta-ketoen)amino-5-deoxy-1,2-O-isopropylidene-alpha-D-glucofuranoses: synthesis, structure, and catecholoxidase activity

The synthesis of 5-amino-5-deoxy-1,2-O-isopropylidene-alpha-D-glucofuranose (8) was carried out via 5-azido-5-deoxy-1,2:3,4-O-diisopropylidene-alpha-D-glucofuranose (6), its reduction with Raney-Nickel and deprotection. 5-N-(beta-Ketoen)amino-5-deoxy-1,2-O-isopropylidene-alpha-D-glucofuranoses (8a-f) were synthesized from 5-amino-5-deoxy-1,2-O-isopropylidene-alpha-D-glucofuranose and beta-ketoenolethers leading to ligands with symmetrically substituted double bonds (8a, 8b) and e/z isomeric mixtures with unsymmetrical substitution (8c-f). Reaction of the ligands with Cu(II) ions leads to binuclear complexes of the general formula Cu2L2. In contrast to copper(II) complexes which are not derived from amino carbohydrates the metal centers in the compounds saturate their coordination sphere by complexation of additional solvent molecules, interaction with neighboring complex molecules, or free hydroxyl groups of the own ligand. Residues of the ketoen moiety, R1 and R2, also influence the electronic properties of the metal centers. The combination of factors leads to different catalytic properties of the complexes in catecholoxidase-like reactions.     

A new, but old, nucleoside analog: the first synthesis of 1-deaza-2'-deoxyguanosine and its properties as a nucleoside and as oligodeoxynucleotides

The first synthesis of 5-amino-3-(2'-deoxy-beta-D-ribofuranosyl)imidazo[4,5-b]pyridin-7-one (1-deaza-2'-deoxyguanosine) is described. The compound was converted from the known AICA-deoxyriboside. The tautomeric structure of the base moiety was determined by theoretical calculation to be a hydroxyl form. Although the analog was found to be labile to acidic conditions, 1-deaza-2'-deoxyguanosine was successfully converted into a phosphoramidite derivative, which was incorporated into oligodeoxynucleotides by the standard phosphoramidite method. Thermal stabilities of oligodeoxynucleotides containing 1-deaza-2'-deoxyguanosine were investigated by thermal denaturing experiments. Also, a triphosphate analog of 1-deaza-2'-deoxyguanosine was synthesized for polymerase extension reactions. Single nucleotide insertion reactions using a template containing 1-deaza-2'-deoxyguanosine, as well as 1-deaza-2'-deoxyguanosine triphosphate, were performed using the Klenow fragment (exonuclease minus) polymerase and other polymerases. No hydrogen bonded base pairs, even a 1-deaza-2'-deoxyguanosine:cytidine base pair, were indicated by thermal denaturing studies. However, though less selective and less effective than the natural guanosine counterpart, the polymerase extension reactions suggested the formation of a base pair of 1-deaza-2'-deoxyguanosine with cytidine during the insertion reactions.     

Determination of isocyanate specific albumin-adducts in workers exposed to toluene diisocyanates

Toluene diisocyanates (2,4-TDI and 2,6-TDI) are important intermediates in the chemical industry. Among the main damages after low levels of TDI exposure are lung sensitization and asthma. It is therefore necessary to have sensitive and specific methods to monitor isocyanate exposure of workers. Urinary metabolites or protein adducts have been used as biomarkers in workers exposed to TDI. However, with these methods it was not possible to determine if the biomarkers result from exposure to TDI or to the corresponding toluene diamines (TDA). This work presents a new procedure for the determination of isocyanate-specific albumin adducts. Isotope dilution mass spectrometry was used to measure the adducts in albumin present in workers exposed to TDI. 2,4-TDI and 2,6-TDI formed adducts with lysine: N(?)-[({3-amino-4-methylphenyl}amino)carbonyl]-lysine, N(?)-[({5-amino-2-methylphenyl}amino)carbonyl]-lysine, and N(?)- [({3-amino-2-methylphenyl}amino)carbonyl]-lysine. In future studies, this new method can be applied to measure TDI-exposures in workers.     

Design, synthesis, and antiviral evaluation of some 3'-carboxymethyl-3'-deoxyadenosine derivatives

3'-Carboxymethyl-3'-deoxyadenosine derivatives were prepared from 2'-O-TBDMS-3'-[(ethoxycarbonyl)methyl]-3'-deoxyadenosine (1) via simple and efficient procedures. Conversion of 1 to its 5'-azido-5'-deoxy derivative 5 was accomplished via a novel one-pot method employing 5'-activation (TosCl) followed by efficient nucleophilic displacement with tetramethylguanidinium azide. Compound 5 was converted to 5'-[(N-methylcarbamoyl)amino] derivative 8 via one-pot reduction/acylation employing H(2)/Pd-C followed by treatment with p-nitrophenyl N-methylcarbamate. N(6)-phenylcarbamoyl groups were introduced by treatment with phenylisocyanate, and an efficient new method for lactonization of 2'-O-TBDMS-3'-[(ethoxycarbonyl)methyl]-3'-deoxyadenosines to give corresponding 2',3'-lactones was also developed. Target compounds were evaluated for anti-HIV and anti-HIV integrase activities, but were not active at the concentrations tested.     

Microbial transformation of 2-amino-4-methyl-3-nitropyridine

Biotransformation of the highly substituted pyridine derivative 2-amino-4-methyl-3-nitropyridine by Cunninghamella elegans ATCC 26269 yielded three products each with a molecular weight of 169?Da which were identified as 2-amino-5-hydroxy-4-methyl-3-nitropyridine, 2-amino-4-hydroxymethyl-3-nitropyridine, and 2-amino-4-methyl-3-nitropyridine-1-oxide. Biotransformation by Streptomyces antibioticus ATCC 14890 gave two different products each with a molecular weight of 169?Da; one was acid labile and converted to the other stable product under acidic conditions. The structure of the stable product was established as 2-amino-4-methyl-3-nitro-6(1H)-pyridinone, and that of the less stable product was assigned as its tautomer 2-amino-6-hydroxy-4-methyl-3-nitropyridine. Four of the five biotransformation products are new compounds. Several strains of Aspergillus also converted the same substrate to the lactam 2-amino-4-methyl-3-nitro-6(1H)-pyridinone. Microbial hydroxylation by C. elegans was found to be inhibited by sulfate ion. In order to improve the yield and productivity of the 5-hydroxylation reaction by C. elegans, critical process parameters were determined and Design of Experiments (DOE) analyses were performed. Biotransformation by C. elegans was scaled up to 15-l fermentors providing 2-amino-5-hydroxy-4-methyl-3-nitropyridine at ca. 13?% yield in multi-gram levels. A simple isolation process not requiring chromatography was developed to provide purified 2-amino-5-hydroxy-4-methyl-3-nitropyridine of excellent quality.     

Preparation and properties of porcine relaxin derivatives shortened at the amino terminus of the A chain

Porcine relaxins shortened at the N terminus of the A chain were produced after protection of all amino groups with the base-labile [[(methylsulfonyl)ethyl]oxy]carbonyl (Msc) protecting group. The first two amino acids were removed by cyanogen bromide digestion whereby simultaneously a free alpha-amino group was generated in position A3. The resulting des-ArgA1,MetA2-N epsilon A7,N epsilon A16,N epsilon B8-tris [[[(methylsulfonyl)ethyl]oxy]carbonyl]relaxin. was further shortened by preparative Edman degradation. The shortest derivative obtained was des-ArgA1,MetA2,ThrA3,LeuA4,SerA5,GluA6 -N epsilon A7,N epsilon A16,N epsilon B8-tris[[[(methylsulfonyl)ethyl]oxy]carbonyl]relaxin. The deprotection of the derivatives in alkaline media resulted in crude des-A(1-2)- to des-A(1-6)-relaxins, which were subsequently purified by gel filtration on Sephadex G-50 superfine followed by either ion exchange chromatography on CM-cellulose at pH 5.1 or high-performance liquid chromatography on reversed-phase columns. During the CNBr digest, a side product was isolated that was identified as the corresponding homoserine ( [HseA2]relaxin) derivative. Shortened relaxin derivatives and [HseA2]relaxin were characterized by reversed-phase chromatography, electrophoresis, end-group determination, and amino acid composition. Circular dichroism studies revealed a distinct change in the structure of relaxins that were shortened by three and more amino acid residues. In the mouse interpubic ligament assay, des-A(1-2)-relaxin and [HseA2]relaxin were fully biologically active while the bioactivity of des-A(1-3)-relaxin dropped to about 50%. Relaxins shortened by four and more amino acid residues were biologically inactive.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of double headed imidazoline acyclo C-nucleosides: 1,4-bis[1-amino-5-oxo-4-substituted(imidazolin-2-yl)]galacto-tetritols

Condensation of 2,3,4,5-tetra-O-acetyl-galactaroyl dichloride (1) with two equivalents of the alpha-amino esters 2a-c gave the corresponding 2,3,4,5-tetra-O-acetyl-galactaric acid diamides 3a-c. Heterocyclization of 3a-c by heating with hydrazine hydrate took place with concomitant de-O-acetylation of the polyacetoxyalkyl chain to give 1,4-bis[1-amino-5-oxo-4-substituted(imidazolin-2-yl)] galacto-tetritols (5a-c) and not the theoretically possible 1,2,4-triazinones 4 as indicated by spectral data. Compounds 5a-c readily reacted with p-nitrobenzaldehyde to give the corresponding p-nitrobenzylideneamino derivatives 6a-c. Acetylation of 5a-c afforded the 2,3,4,5-tetra-O-acetyl-1,4-bis[1-acetamido-5-oxo-4-substituted(imidazolin-2-yl)]galacto-tetritols (7a,b,d). De-O-acetylation of 7a,b,d gave 1,4-bis[1-acetamido-5-oxo-4-substituted (imidazolin-2-yl)]galacto-tetritols (8a-c).     

Novel carboranyl amino acids and peptides: reagents for antibody modification and subsequent neutron-capture studies.

A new alpha-amino acid derivative incorporating the 1,2-dicarba-closo- dodecarborane(12) cage, namely 5-(2-methyl-1,2-dicarba-closo-dodecarborane(12)-1-yl)- 2-aminopentanoic acid (2), was synthesized by the alkylation of the benzophenone Schiff's base of glycine methyl ester with 3-(2-methyl-1,2-dicarba-closo-dodecaborane(12)-1-yl)pr opyl iodide (8). This amino acid was employed in the synthesis of peptide derivatives such as 19-21 using solid-phase Merrifield methods. Dipeptide 19 was converted to a water-soluble ionic derivative by the pyrrolidine-mediated carborane cage degradation reaction followed by cation exchange to afford sodium salt 22. Dansylation of 22 with dansyl chloride yielded fluorescence-labeled dipeptide 23. Undecapeptide 21 was dansylated while still anchored to the Merrifield resin. Following its cleavage from the resin with hydrogen fluoride, product 25 was acetylated to block the free amino group on the lysine residue and then converted to water-soluble derivative 27. Trial conjugations of dipeptide 23 and undecapeptide 27 to T84.66, an anti-CEA antibody, were carried out by means of carboxyl activation with N-hydroxysulfosuccinimide and N,N-diisopropylcarbodiimide. Studies of the chemical syntheses of these and other peptide derivatives and the conjugation of 23 and 27 to the antibody are described.     

Comparison of inhibitory activity of isomeric triazolopyridine derivatives towards adenosine receptor subtypes or do similar structures reveal similar bioactivities?

The synthesis of an array of 8-amino-2-aryl-[1,2,4]triazolo[1,5-a]pyridine-6-carboxyl amide derivatives is described for the first time. A subset of 20 derivatives were compared to their isomeric 5-amino-2-aryl-[1,2,4]triazolo[1,5-a]pyridine-7-carboxyl amide counterparts with regard to their potential to inhibit the human adenosine 2a (hA2a) receptor and their selectivity against the human adenosine 1 (hA1) receptor. Based on the analysis of H-bond donor/acceptor capabilities of the isomeric triazolopyridine pairs it can be concluded that the H-bond donor strength of the free amino functionality is the main determinant for hA2a inhibitory activity and hA1 selectivity.     

An Improved Synthesis of 2′-Deoxy-9-deazaadenosine and an N-7 Blocked Derivative Useful for the Synthesis of Modified Oligonucleotides Containing 2′-Deoxy-9-deazaadenosine

Abstract

As an epimerization resistant synthon in the synthesis of oligo-nucleotides consisting of C-nucleoside analogues, hitherto unknown 5-benzyloxy-methyl-3-(2-deoxy-β-D-erythro-pentofuranosyl)pyrrolo[3,2-d]pyrimpyrimidine (7-benzyloxymethyl-2′-deoxy-9-deazaadenosine) was prepared in seven steps from the known 3-amino-2-cyano-4-(2,3-O-isopropylidene-5-O-trityl-β-D-ribofuranosyl)-pyrrolpyrrole (1). Treatment of 1 with benzyl chloromethyl ether in the presence of potassium t-butoxide and 18-crown-6 afforded the N-protected pyrrole 2, which was converted into the 9-deazapurine derivative 3 in high yield by heating in EtOH. 7-Benzyloxymethyl-9-deazaadenosine 4 was obtained from 3 by acid hydrolysis in 2.5% methanolic hydrogen chloride. After protection of the hydroxyl groups of 4 with Markievicz's reagent, the product 5 was converted into the 2′-O-phenoxythiocarbonyl derivative 6. Reduction of 6 with butyltin hydride in the presence of 2,2′-azobis(2-methylpropionitrile), followed by desilylation with triethylammonium fluoride, afforded the desired 7-benzyloxymethyl-2′-deoxy-9-deazaadenosine (8) in high overall yield. The benzyloxymethyl group of 8 was removed by hydrogenolysis over palladium hydroxide (Degussa type) to give 2′-deoxy-9-deazaadenosine (9) in quantitative yield. The structure of 9 is discussed.     

Purification of human S-adenosylmethionine decarboxylase expressed in Escherichia coli and use of this protein to investigate the mechanism of inhibition by the irreversible inhibitors, 5'-deoxy-5'-[(3-hydrazinopropyl)methylamino]adenosine and 5'-([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxyadenosine.

Human S-adenosylmethionine decarboxylase (AdoMetDC) was expressed in high yield in Escherichia coli using the pIN-III(lppP-5) expression vector and purified to apparent homogeneity using affinity chromatography on methylglyoxal bis(guanylhydrazone)-Sepharose. The inactivation of the purified enzyme by 5'-deoxy-5'-[(3-hydrazinopropyl)methylamino]adenosine (MHZPA) was accompanied by an increase in absorbance at 260 nm of the large subunit. This increase was equivalent to the addition of 1 molecule of MHZPA. After digestion with the protease Lys-C, a peptide that contained the bound MHZPA was isolated and found to have the amino acid composition consistent with that expected from the amino terminus of the large subunit. These results indicate that MHZPA inactivates AdoMetDC by forming a hydrazone derivative at the pyruvate prosthetic group. Inactivation of AdoMetDC by 5'-([(Z)-4-amino-2-butenyl]methylamino]-5'-deoxyadenosine (AbeAdo) led to the appearance of a new peptide peak in the Lys-C protease digest. This peptide had the sequence ASMFVSK. This agrees with the expected sequence from the amino terminus, which is pyruvoyl-SMFVSK, with the exception that the pyruvate has been converted to alanine. Direct gas-phase sequencing of the large subunit of the enzyme also indicated the presence of alanine at the amino terminus after inactivation with AbeAdo. These results indicate that this inhibitor leads to transamination of the pyruvate prosthetic group. Since the pyruvate is covalently linked to the protein, its replacement by alanine leads to an irreversible inactivation of AdoMetDC.