Formation of Fluorinated Amido Esters through Unexpected C3-C4 Bond Fission in 4-Trifluoromethyl-3-oxo-β-lactams

4-Trifluoromethyl-3-oxo-β-lactams were unexpectedly transformed into 2-[(2,2-difluorovinyl)amino]-2-oxoacetates as major products, accompanied by minor amounts of 2-oxo-2-[(2,2,2-trifluoroethyl)amino]acetates, upon treatment with alkyl halides and triethylamine in DMSO. This peculiar C3-C4 bond fission reactivity was investigated in-depth, from both an experimental and a computational point of view, in order to shed light on the underlying reaction mechanism.

Trypanocidal effect of the benzyl ester of N-propyl oxamate: a bi-potential prodrug for the treatment of experimental Chagas disease

BACKGROUND

Chagas disease, which is caused by Trypanosoma cruzi, is a major health problem in Latin America, and there are currently no drugs for the effective treatment of this disease. The energy metabolism of T. cruzi is an attractive target for drug design, and we previously reported that inhibitors of α-hydroxy acid dehydrogenase (HADH)-isozyme II exhibit trypanocidal activity. N-Propyl oxamate (NPOx) is an inhibitor of HADH-isozyme II, and its non-polar ethyl ester (Et-NPOx) is cytotoxic to T. cruzi. A new derivative of NPOx has been developed in this study with higher trypanocidal activity, which could be used for the treatment of Chagas disease.

METHODS

The benzyl ester of NPOx (B-NPOx) was synthesized and its activity evaluated towards epimastigotes and bloodstream trypomastigotes (in vitro), as well as mice infected with T. cruzi (in vivo). The activity of B-NPOx was also compared with those of Et-NPOx, benznidazole (Bz) and nifurtimox (Nx). NINOA, Miguz, Compostela, Nayarit and INC-5 T. cruzi strains were used in this study.

RESULTS

Polar NPOx did not penetrate the parasites and exhibited no trypanocidal activity. In contrast, the hydrophobic ester B-NPOx exhibited trypanocidal activity in vitro and in vivo. B-NPOx exhibited higher trypanocidal activity than Et-NPOx, Bz and Nx towards all five of the T. cruzi strains. The increased activity of B-NPOx was attributed to its hydrolysis inside the parasites to give NPOx and benzyl alcohol, which is an antimicrobial compound with trypanocidal effects. B-NPOx was also effective against two strains of T. cruzi that are resistant to Bz and Nx.

CONCLUSION

B-NPOx exhibited higher in vitro (2- to 14.8-fold) and in vivo (2.2- to 4.5-fold) trypanocidal activity towards T. cruzi than Et-NPOx. B-NPOx also exhibited higher in vitro (2- to 24-fold) and in vivo (1.9- to 15-fold) trypanocidal activity than Bz and Nx. B-NPOx is more lipophilic than Et-NPOx, allowing for better penetration into T. cruzi parasites, where the enzymatic cleavage of B-NPOx would give NPOx and benzyl alcohol, which are potent trypanocidal agents. Taken together with its low toxicity, these results suggest that B-NPOx could be used as a potent prodrug for the treatment of Chagas disease.

15N-1H and 15N-13C couplings in 15N-enriched dihydroxamic acids

(15)N-enriched dihydroxamic acids (HONHCO(CH(2))(n)CONHOH, n = 0, 1, and 2) were prepared and their spectra NMR ((1)H, (13)C, (15)N) recorded in dimethyl sulfoxide (DMSO) solutions with the aim of determining (15)N coupling constants ((15)N-(1)H and (15)N-(13)C). The results supplement chemical shifts published earlier and yield additional support to the structural conclusions derived from other NMR parameters. Notably, no trace of hydroximic structures could be found in the (15)N NMR spectra of these acids. The values of (15)N-(13)C coupling constants backed by theoretical calculations support the assignments made earlier for all of the major conformers and for the minor conformer of succinohydroxamic acid. The enrichment revealed that the minor component of malonodihydroxamic acid solution previously considered to be the ZE conformer is in fact the monohydroxamic acid (HOOC-CH(2)-CO-NH-OH).

Synthesis of new oxamide-based ligand and its coordination behavior towards copper(II) ion: spectral and electrochemical studies

A new ligand N,N'-bis{3-(2-formyl-4-methyl-phenol)-6-iminopropyl}oxamide (L) and its mono- and binuclear copper(II) complexes have been synthesized and characterized. The ligand shows absorption maxima at 249 and 360 with a weak transition at 455 nm. The ligand was found to be fluorescent and shows an emission maximum at 516 nm on excitation at 360 nm. The electronic spectra of the mono- and binuclear Cu(II) complexes exhibited a d-d transition in the region 520-560 nm characteristic of square planar geometry around Cu(II) ion. The ESR spectrum of the mononuclear complex showed four lines with nuclear hyperfine splitting. The binuclear complex showed a broad ESR spectrum with g=2.10 due to antiferromagnetic interaction between the two Cu(II) ions. The room-temperature magnetic moment values (micro(eff)) for the mono- and binuclear Cu(II) complexes are found to be 1.70 micro(B) and 1.45 micro(B), respectively. The electrochemical studies of the mononuclear Cu(II) complex showed a single irreversible one-electron wave at -0.70 V (E(pc)) and the binuclear Cu(II) complex showed two irreversible one-electron reduction waves at -0.75 V (E(pc)(1)) and -1.27 V (E(pc)(2)) in the cathodic region.

Design, Synthesis, and Biological Evaluation of Plasmodium falciparum Lactate Dehydrogenase Inhibitors

Plasmodium falciparum lactate dehydrogenase (pfLDH) is a key enzyme for energy generation of malarial parasites and is a potential antimalarial chemotherapeutic target. It is known that the oxamate moiety, a pyruvate analog, alone shows higher inhibition against pfLDH than human LDHs, suggesting that it can be used for the development of selective inhibitors. Oxamic acid derivatives were designed and synthesized. Derivatives 5 and 7 demonstrated activities against pfLDH with IC50 values of 3.13 and 1.75 muM, respectively, and have 59- and 7-fold selectivity over mammalian LDH, respectively. They also have micromolar range activities against Plasmodium falciparum malate dehydrogenase (pfMDH), which may fill the role of pfLDH when the activity of pfLDH is reduced. Thus, certain members of these oxamic acid derivatives may have dual inhibitory activities against both pfLDH and pfMDH. It is presumed that dual LDH/MDH inhibitors would have enhanced potential as antimalarial drugs.

Solid-Phase Synthesis of Carboxylic and Oxamic Acids via OsO4/NaIO4/HMTA-Mediated Oxidative Cleavage of Acetylenic Peptides

A general method for the solid-phase synthesis of carboxy-functionalized peptides by oxidative cleavage of alkynes is presented. Clean and quantitative conversion is enabled by the addition of bases, such as DABCO and HMTA, to the classical OsO4/NaIO4 mixture. The utility of the reaction is further illustrated by the synthesis of oxamic acids.

Generation of Oxamic Acid Libraries: Antimalarials and Inhibitors of Plasmodium falciparum Lactate Dehydrogenase

Lactate dehydrogenase (LDH) is a key enzyme in the glycolytic pathway of Plasmodium falciparum (pf) and has several unique amino acids, related to other LDHs, at the active site, making it an attractive target for antimalarial agents. Oxamate, a competitive inhibitor, shows high substrate affinity for pfLDH. This class of compounds has been viewed as potential antimalarial agents. Thus, we have developed an effective automated synthetic strategy for the rapid synthesis of oxamic acid and ester libraries to screen for potential lead inhibitors. One hundred sixty-seven oxamic acids were synthesized using a "catch and release" method with overall yields of 20-70%. Most of the compounds synthesized had some inhibitory effects, but compounds 5 and 6 were the most active against both chloroquine- and mefloquine-resistant strains with IC50 values of 15.4 and 9.41 microM and 20.4 and 8.40 microM, respectively. Some oxamic acids showed activities against pfLDH and mammalian LDH (mLDH) at the micromolar range. These oxamic acids selectively inhibited pfLDH 2-5 fold over mLDH. Oxamic acid 21 was the most active against pfLDH at IC50 = 14 and mLDH at IC50 = 25 microM, suggesting that oxamic acid derivatives are potential inhibitors of pfLDH and that further study is required to develop selective inhibitors of pfLDH over mLDH.

Synthesis and evaluation of thiazole carboxamides as vanilloid receptor 1 (TRPV1) antagonists

A thiazole derivative, 2-(2,6-dichlorobenzyl)-N-(4-isopropylphenyl) thiazole-4-carboxamide (1), was identified as a TRPV1 antagonist. We synthesized various thiazole analogs and evaluated them for their ability to block capsaicin- or acid-induced calcium influx in TRPV1-expressing CHO cells. The IC(50) values of the most potent antagonists were ca. 0.050microM in these assays.

Synthesis of bis-(methyl 3,4,6-tri-O-acetyl-D-glucopyranosid-2-yl)-oxamides

The synthesis of a new bis-(D-glucopyranosid-2-yl)oxamides via the key intermediate, N-acetyl N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl) oxamic acid chloride (2alpha) is described. Treatment of compound 2alpha with methyl 3,4,6-tri-O-acetyl-2-amino-2-deoxy-beta-D-glucopyranoside afforded N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N'-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl)-oxamide. Reaction of 2alpha with 1,2-diaminoethane afforded 1,2-bis-[N,N'-(methyl 3',4',6'-tri-O-acetyl-alpha-D-glucopyranosid-2'-yl)]ethyloxamide as a main product, while 2-N-[N'-(methyl 3',4',6'-tri-O-acetyl-alpha-D-glucopyranosid-2'-yl)oxamide]-ethyl acetamide was formed as a side product. Reaction of 2alpha with 1,3-diamino-2-hydroxypropane gave only 1,3-bis-N,N-[N'-(methyl 3',4',6'-tri-O-acetyl-2'-deoxy-alpha-D-glucopyranosid-2'-yl)-oxamido]-2-propanol.

Stereoselective Allyl Amine Synthesis through Enantioselective Addition of Diethylzinc and [1,3]-Chirality Transfer: Synthesis of Lentiginosine and Polyoxamic Acid Derivative

A new synthetic method for the preparation of allyl amines has been developed. The key steps of this method are enantioselective addition of diethylzinc and [1,3]-chirality transfer through the [3.3] sigmatropic rearrangement of allyl cyanates. Stereocontrolled syntheses of lentiginosine (1) and polyoxamic acid derivative 2 from a common intermediate 7 derived from D-tartaric acid (8), have been accomplished.

Fragment screening and assembly: a highly efficient approach to a selective and cell active protein tyrosine phosphatase 1B inhibitor

Using an NMR-based fragment screening and X-ray crystal structure-based assembly, starting with millimolar ligands for both the catalytic site and the second phosphotyrosine binding site, we have identified a small-molecule inhibitor of protein tyrosine phosphatase 1B with low micromolar inhibition constant, high selectivity (30-fold) over the highly homologous T-cell protein tyrosine phosphatase, and good cellular activity in COS-7 cells.

Discovery of a potent, selective protein tyrosine phosphatase 1B inhibitor using a linked-fragment strategy

Protein tyrosine phosphatase 1B (PTP1B) is an enzyme that downregulates the insulin receptor. Inhibition of PTP1B is expected to improve insulin action, and the design of small molecule PTP1B inhibitors to treat type II diabetes has received considerable attention. In this work, NMR-based screening identified a nonselective competitive inhibitor of PTP1B. A second site ligand was also identified by NMR-based screening and then linked to the catalytic site ligand by rational design. X-ray data confirmed that the inhibitor bound with the catalytic site in the native, "open" conformation. The final compound displayed excellent potency and good selectivity over many other phosphatases. The modular approach to drug design described in this work should be applicable for the design of potent and selective inhibitors of other therapeutically relevant protein tyrosine phosphatases.

Synthesis and quantitative structure-activity relationships of oxanilates as chemical hybridizing agents for wheat (Triticum aestivum L.)

Chemical hybridizing agents (CHAs) can facilitate two-line breeding in heterosis programs of crops. Twenty-seven oxanilates having different aromatic substitutions were synthesized and screened as CHAs on two genotypes of wheat, PBW 343 and HD 2733, during two Rabi (winter) seasons, 2000-01 and 2001-02. The oxanilates prepared by thermal condensation of anilines with diethyl oxalate or by acylation with ethoxycarbonyl methanoyl chloride were sprayed at 1000 and 1500 ppm at the premeiotic stage of wheat, when the length of the emerging spike of the first node was 7-8 mm. Pollen sterility and spikelet sterility were measured in each treatment. Ethyl oxanilates 5, 6, and 25,containing 4-F, 4-Br, and 4-CF(3) aromatic substituents, respectively, induced greater than 98% spikelet sterility, the desired level, at 1500 ppm. Quantitative structure-activity relationship analysis revealed a direct relationship between F(p) and molecular mass but an inverse relationship between MR, E(S), and R in influencing the bioactivity. Several F(1) hybrids were developed using 5, and at least one showed heterosis.

Control of enantioselectivity in the photochemical conversion of alpha-oxoamides into beta-lactam derivatives

[reaction: see text]. Several approaches to asymmetric induction in the alpha-oxoamide (1) to beta-lactam (2) photorearrangement are described. Best results are obtained via irradiation of ionic and covalent chiral auxiliary-containing reactants in the crystalline state and in the interior supercages of zeolites.

Preparation of N'-[2-(5,6-dimethylbenzothiazolyl)]-N-furfuryloxamide with plant growth regulatory activity

The reaction of the N-furfuryloxamic acid sodium salt (12) with 1,1'-oxalyldiimidazole (ODI) yielded the imidazolide (13) as an intermediate, and this directly reacted with 2-aminothiazole derivatives (14) or 2-aminobenzothiazole derivatives (15) under essentially neutral conditions to afford the N'-12-(substituted thiazolyl)]- or N'-[2-(substituted benzothiazolyl)]-N'-furfuryloxamides (6 or 7). The prepared compounds (6 and 7) were examined for plant growth regulatory activity in a seed germination assay. The examination resulted in the discovery of some new revelations that N'-[2-(5,6-dimethylbenzothiazlyl)]-N-furfuryloxamide (7c) at the concentration of 1.0 x 10(-3) M completely inhibited the radicle growth of both rape and leek seedlings.

Synthesis and biological activity of phenoxyphenyl oxamic acid derivatives related to L-thyronine

The synthesis of substituted phenoxyphenyl oxamic acid derivatives related to L-thyronine (L-T3) is described. The in vitro and in vivo cholesterol lowering and cardiovascular effects of these compounds are presented and discussed.

N-(4-Isoxazolylthiazol-2-yl)oxamic acid derivatives as potent orally active antianaphylactic agents

A series of N-(4-isoxazolylthiazol-2-yl)oxamic acid derivatives was synthesized and tested on the passive cutaneous anaphylaxis (PCA) model in rats to verify its potential antianaphylactic activity. These compounds were prepared by reaction of an appropriate bromoacetylisoxazole with thiourea to give the corresponding aminothiazole and subsequent condensation with an oxalic acid monoester chloride to yield, following the usual process, the oxamic acid derivatives. Most of the new compounds exhibited, by intraperitoneal route in rats, a very potent antianaphylactic activity on PCA response, higher than that of the reference compound disodium cromoglycate (DSCG). The new derivatives, in contrast with DSCG, were effective on PCA even by oral route. The most interesting derivative of the new series was N-[4-(3-methyl-5-isoxazolyl)-2-thiazolyl]oxamic acid 2-ethoxyethyl ester (49), which was also active and more potent than DSCG in experimental models involving either IgE- or IgG-mediated anaphylactic responses at bronchopulmonary level.

Studies of arylthiazole oxamates in relation to oral antiallergic activity

25 arylthiazole oxamate derivatives were synthesized and examined for antiallergic activity in the rat passive cutaneous anaphylaxis assay. These compounds were prepared by treatment of the appropriate bromoacetophenone with thioureas to give arylaminothiazoles. Further condensation with alkyloxalyl chloride gave the arylthiazolyl oxamates. Several derivatives showed a 70% inhibition at 5 mg/kg p.o. p-Alkoxy substitution on the phenyl ring resulted in enhanced activity while N-alkyl substitution on the nitrogen amide function inhibited the activity. Ethyl-N-(4-p-methoxyphenyl)-2-thiazolyl oxamate (tioxamast, F-1865) was selected for clinical studies.

Troponoids. 3. Synthesis and antiallergy activity of N-troponyloxamic acid esters

A number of oxamic acid derivatives of tropones and tropolones were synthesized and their antianaphylactic activity was determined in passive paw anaphylaxis (PPA). Several of these esters possessed oral activity. A comparison of the effect on the biological activity of the esters and the corresponding acid and its salt is reported. The experiments suggesting a relationship between the activity and the bioavailability of the ester 19 are also described. A study of the fate of ester 19 in serum on oral or intravenous administration to rats and dogs is reported. In vitro results of the effect of the compounds 19, 45, and 45a on the activity of the guinea pig lung and beef heart phosphodiesterase are presented. The various factors that may contribute to the antiallergy activity of compounds of this series are discussed.

N,N'-(Phenylene)dioxamic acids and their esters as antiallergy agents

A series of dialkyl N,N'-(m-phenylene)dioxamates was synthesized by treatment of the requisite m-phenylenediamines with an alkyloxalyl chloride in the presence of triethylamine. Hydrolysis with sodium hydroxide solution gave the corresponding N,N'-(m-phenylene)dioxamic acids. Several N,N'-(p-phenylene)dioxamic acids were synthesized also in the same manner starting with the requisite p-phenylenediamines. These compounds were tested in the rat passive cutaneous anaphylaxis (PCA) assay. When tested iv, activity was found in the N,N'-(m-phenylene) dioxamic acids up to 2500 times that shown by disodium cromoglycate [50% inhibition at 0.001 mg/kg for N,N'-(2-chloro-5-cyano-m-phenylene)dioxamic acid (compound 61)]. Oral activity was seen in this series of compounds with duration of activity up to 120 min. Oral activity was detected in diethyl N,N'-(2-chloro-5-cyano-m-phenylene)dioxamate (compound 38) at levels of drug as low as 0.1 mg/kg.

Pyrrole, furan, and thiophene oxamates as potential antiallergy agents

Nine heterocyclic oxamic acid derivatives were synthesized and tested in the rat passive cutaneous anaphylactic assay as potential antiallergy agents. Some compounds also were tested for their effects on cholesterol-lipoprotein levels and for diuretic, antidiabetic, and antifertility activities in rats.

(2-Carboxy-1,4-dihydro-4-oxoquinolyl)oxamic acids and (2-carboxy-1,4-dihydro-4-oxobenzo[h]quinolyl)oxamic acids as antiallergy agents

A group of (2-carboxy-1,4-dihydro-4-oxoquinolyl)oxamic acids (5) containing the oxamic acid group in the 5,6, or 7 positions were synthesized and investigated for antiasthma activity as indicated by the passive cutaneous anaphylaxis (PCA) reaction in rats. Also synthesized and investigated were two (2-carbosy-1,4-dihydro-4-oxobenzo[h]-quinolyl)oxamic acids (9 and 10). Several of the compounds synthesized (viz. 5e, 5f, and 10) showed activity in the PCA test approximately 25 times that shown by disodium cromoglycate (1), as measured by the ID50 doses.

Oxanilic acids, a new series of orally active antiallergic agents

A large number of oxanilic acid esters and N-heteroaryl oxamic acid esters were prepared and found to have antiallergic activity using the rat passive cutaneous anaphylaxis (PCA) test. Many of the oxanilic acid esters are active orally, with the most active species having an aryl 2'-carbamoyl group and a 3'-methoxy group. Hydrolysis of the ester from the oxanilic ester moiety causes a loss of oral activity.