A highly efficient method for the synthesis of guanidinium derivatives

Micelle-Enabled One-Pot Guanidine Synthesis in Water Directly from Isothiocyanate using Hypervalent Iodine(III) Reagents under Mild Conditions

In this work, we developed a one-pot synthesis of guanidine directly from isothiocyanate using DIB (diacetoxyiodobenzene) as a desulfurizing agent under micellar conditions in water. Our optimization study revealed that the use of 1 % TPGS-750-M as a surfactant with NaOH as an additive base at room temperature can convert a variety of isothiocyanates and amines into corresponding guanidines in excellent yields (69-95 %). This synthetic process in water can be applied to prepare guanidine at gram-scale quantity. Our aqueous micellar medium also demonstrated high reusability as the reaction can be performed for several cycles without losing its efficiency. The reaction is metal-free, utilizes water as solvent and practical (room temperature and open flask).

Antiprotozoal activity and DNA binding of N-substituted N-phenylbenzamide and 1,3-diphenylurea bisguanidines

Two series of N-alkyl, N-alkoxy, and N-hydroxy bisguanidines derived from the N-phenylbenzamide and 1,3-diphenylurea scaffolds were synthesised in three steps from the corresponding 4-amino-N-(4-aminophenyl)benzamide and 1,3-bis(4-aminophenyl)urea, respectively. All of the new compounds were evaluated in vitro against T. b. rhodesiense (STIB900) trypomastigotes and Plasmodium falciparum NF54 parasites (erythrocytic stage). N-alkoxy and N-hydroxy derivatives showed weak micromolar range IC50 values against T. b. rhodesiense and P. falciparum whereas the N-alkyl analogues displayed submicromolar and low nanomolar IC50 values against P. falciparum and Trypanosoma brucei, respectively. Two compounds, 4-(2-ethylguanidino)-N-(4-(2-ethylguanidino)phenyl)benzamide dihydrochloride (7b) and 4-(2-isopropylguanidino)-N-(4-(2-isopropylguanidino)phenyl)benzamide dihydrochloride (7c), which showed favourable drug-like properties and in vivo efficacy (100% cures) in the STIB900 mouse model of acute human African trypanosomiasis represent interesting leads for further in vivo studies. The binding of these compounds to AT-rich DNA was confirmed by surface plasmon resonance (SPR) biosensor experiments.

Amino-[(1H-benzimidazol-2-yl)amino]-methaniminium 4-methyl-benzene-sulfonate

The asymmetric unit of the title salt, C₈H₁₀N₅⁺·C₇H₇O₃S⁻, consists of two amino­[(1H-benzimidazol-2-yl)amino]­meth­an­im­inium cations and two 4-methyl­benzene­sulfonate anions. The cations are each stabilized by intra­molecular N—H⋯N hydrogen bonds between the free amino groups and the imine N atoms of the benzimidazole units, forming S(6) ring motifs. In the crystal, cations and anions are linked by N—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular framework. Two strong π–π stacking inter­actions [centroid–centroid distances = 3.4112 (14) and 3.4104 (14) Å] also occur between the centroids of the imidazole rings of like cations.

Design, synthesis and biological evaluation of B-region modified diarylalkyl amide analogues as novel TRPV1 antagonists

Design, synthesis and biological evaluation of B-region, known to be a dipolar interacting pharmacophore, modified diarylalkyl amide analogues for novel TRPV1 (transient receptor potential channel, vanilloid subfamily member 1) antagonists was described. A variety of moieties including guanidines, heterocyclic rings, cinnamides, and α-substituted acetamides were introduced at the B-region. TRPV1 antagonistic activities of these analogues were evaluated by (45)Ca(2+) uptake assay in rat DRG neuron. In particular, α,α-difluoroamide 53 exhibited 3-fold more potent TRPV1 antagonistic activity (IC50 = 0.058 μM) than the parent amide analogue 6.

Chlorotrimethylsilane activation of acylcyanamides for the synthesis of mono-N-acylguanidines

A simple and efficient one-pot method for the synthesis of monoprotected guanidines is presented. Treatment of an acylcyanamide with chlorotrimethylsilane generates a reactive N-silylcarbodiimide capable of guanylating a variety of amines. Typically the reaction is complete in 15 min for primary and secondary aliphatic amines at rt. Hindered amines and anilines are also competent nucleophiles but require extended reaction times.

Concise synthesis of 2-amino-4(3H)-quinazolinones from simple (Hetero)aromatic amines

A novel and simple method of preparation of 2-alkylaminoquinazolin-4-ones with fused heteroaromatic rings from easily accessible (hetero)aromatic amines is described. The method is very efficient, and the 2-alkylaminoquinazolinone derivatives are obtained in three steps without chromatographic purification. The key step is the ring closure of the N-protected guanidine intermediates by intramolecular Friedel-Craft's type substitution.

On the structure of palau'amine: evidence for the revised relative configuration from chemical synthesis

Hexacyclic congeners 3 and 4 of palau'amine, which incorporate both guanidine functional groups and have the cis configuration of the azabicyclo[3.3.0]octane core, are prepared in 14 steps from cycloadduct 6. Synthetic access to these analogues allows the first direct comparison of NMR data for hexacyclic diguanidine structures having the originally proposed cis-azabicyclo[3.3.0]octane fragment with data for natural alkaloids of the palau'amine family. This comparison provides convincing evidence in favor of the recently proposed structural revision of these marine alkaloids, fully supporting the trans configuration of the central azabicyclo[3.3.0]octane ring system of palau'amine and congeners.

Synthesis of Functionalized Guanidino Amino Acids

We report the synthesis of guanidino amino acids (GuAA), which are structurally related to Arg and resemble a dipeptide consisting of alpha- and gamma-amino acid with a guanidinium group in the main chain. The compounds are available with different protecting groups in gram amounts and are intended as synthetic building blocks for the construction of synthetic oxoanion or peptide receptors. Tyr, Trp or dansyl-functionalized Lys can be introduced as the alpha-amino acid part, which leads to luminescent GuAAs. The compounds signal carboxylate binding in MeOH, DMSO and buffered water by change of the emission intensity. The property may find use in the construction of chemosensors.

Novel Potent Antagonists of Transient Receptor Potential Channel, Vanilloid Subfamily Member 1: Structure−Activity Relationship of 1,3-Diarylalkyl Thioureas Possessing New Vanilloid Equivalents

Recently, 1,3-diarylalkyl thioureas have merged as one of the promising nonvanilloid TRPV1 antagonists possessing excellent therapeutic potential in pain regulation. In this paper, the full structure-activity relationship for TRPV1 antagonism of a novel series of 1,3-diarylalky thioureas is reported. Exploration of the structure-activity relationship, by systemically modulating three essential pharmacophoric regions, led to six examples of 1,3-dibenzyl thioureas, which exhibit Ca(2+) uptake inhibition in rat DRG neuron with IC(50) between 10 and 100 nM.

Solid-Phase Synthesis of Arginine-Containing Peptides and Fluorogenic Substrates Using a Side-Chain Anchoring Approach

Attachment of an amino acid to a solid support by its side chain is sometimes necessary to take advantage of an alpha-carboxylic group available for diverse modifications, including the incorporation of a fluorophore for the preparation of fluorogenic substrates. In contrast to most other amino acids, anchoring the guanidinium group of an arginine to a resin requires the use of a supplementary linker. To avoid the usually multistep synthesis of such a linker as well as its difficult attachment to the guanidine group, we developed a simple method where the guanidine group is built on a Rink amide resin. Our strategy followed the steps of guanidine formation: (i) addition of an isothiocyanate derivative of ornithine to the amino group of a solid support, yielding Nomega-linked thiocitrulline; (ii) S-methylation of thiourea; (iii) guanidinylation using ammonium acetate. Cleavage of the resin generated the arginine-containing compound, the amine group of the resin becoming part of the guanidine. We have demonstrated the usefulness of this method by the synthesis of a series of fluorogenic substrates for trypsin-like serine proteases, which were obtained in high yield and purity. Then, our strategy also allowed generation from the same precursor differentially substituted arginine derivatives, including Nomega-methyl- and Nomega-ethylarginines. The ability to prepare such analogues together with the intermediates thiocitrulline and S-methylisothiocitrulline from a unique precursor while the alpha-amine and carboxylic groups remain available for modification also makes this method a powerful tool for combinatorial solid-phase synthesis of NO synthase inhibitors.

TFA-sensitive arylsulfonylthiourea-assisted synthesis of N,N'-substituted guanidines

An efficient synthesis of N,N'-substituted guanidine derivatives was developed via an aromatic sulfonyl-activated thiourea intermediate. The use of certain aromatic sulfonamides, such as PbfNH(2), as the key reagent to incorporate a TFA-labile guanidine protection group greatly facilitates solid-phase synthesis of N,N'-substituted guanidine compounds.