Catalytic addition of amines to carbodiimides by bis(β-diketiminate)lanthanide(ii) complexes and mechanistic studies

Bis(β-diketiminate)lanthanide(ii) complexes L₂Ln(THF)_n were found to be excellent pre-catalysts for catalytic addition of amines to carbodiimides and a possible catalytic mechanism was proposed on the basis of the isolation of monoguanidinate Eu(ii) and bis(guanidinate) Yb(iii) species.

Design, synthesis, mechanisms of action, and toxicity of novel 20(s)-sulfonylamidine derivatives of camptothecin as potent antitumor agents

Twelve novel 20-sulfonylamidine derivatives (9a-9l) of camptothecin (1) were synthesized via a Cu-catalyzed three-component reaction. They showed similar or superior cytotoxicity compared with that of irinotecan (3) against A-549, DU-145, KB, and multidrug-resistant (MDR) KBvin tumor cell lines. Compound 9a demonstrated better cytotoxicity against MDR cells compared with that of 1 and 3. Mechanistically, 9a induced significant DNA damage by selectively inhibiting Topoisomerase (Topo) I and activating the ATM/Chk related DNA damage-response pathway. In xenograft models, 9a demonstrated significant activity without overt adverse effects at 5 and 10 mg/kg, comparable to 3 at 100 mg/kg. Notably, 9a at 300 mg/kg (i.p.) showed no overt toxicity in contrast to 1 (LD50 56.2 mg/kg, i.p.) and 3 (LD50 177.5 mg/kg, i.p.). Intact 9a inhibited Topo I activity in a cell-free assay in a manner similar to that of 1, confirming that 9a is a new class of Topo I inhibitor. 20-Sulfonylamidine 1-derivative 9a merits development as an anticancer clinical trial candidate.

A dual site catalyst for mild, selective nitrile reduction

We report a novel ruthenium bis(pyrazolyl)borate scaffold that enables cooperative reduction reactivity in which boron and ruthenium centers work in concert to effect selective nitrile reduction. The pre-catalyst compound [κ(3)-(1-pz)2HB(N = CHCH3)]Ru(cymene)(+) TfO(-) (pz = pyrazolyl) was synthesized using readily-available materials through a straightforward route, thus making it an appealing catalyst for a number of reactions.

Copper-catalyzed sequential N-arylation of C-amino-NH-azoles

Copper(ii)-catalyzed boronic acid promoted C–N bond cross-coupling reactions have been developed for sequential N-arylation of C-amino-NH-azoles.

Direct N9-arylation of purines with aryl halides

The reported protocol is the first to be demonstrated to efficiently couple aryl halides to purines with predictable selectivity.

A general route for synthesis of N-aryl phenoxazines via copper(i)-catalyzed N-, N-, and O-arylations of 2-aminophenols

A novel copper(i)-catalyzed tandem reaction ofN- andO-arylations was developed and a general route for synthesis ofN-aryl phenoxazinesviacopper-catalyzedN-,N-, andO-arylations of 2-aminophenols was established.

Guanidines: from classical approaches to efficient catalytic syntheses

This review focuses on the metal-mediated catalytic addition of amines to carbodiimides as an atom-economical alternative to the classical synthesis of guanidines.

Novel approaches to screening guanidine derivatives

INTRODUCTION

Compounds containing guanidine moiety, originating both from natural and synthetic sources, have found potential applications in both synthetic and medicinal chemistry. Indeed, guanidine functionality can be found in many natural and pharmaceutical products as well as in cosmetic ingredients produced by synthetic methods.

AREAS COVERED

This review covers the latest developments in the research undertaken for the therapeutic application of newly synthesized guanidine derivatives including: small peptides and peptidomimetics. This article encompasses the selected literature published in the last three decades with a focus on the novel approaches for screening of lead drug candidates with their pharmacological action.

EXPERT OPINION

Guanidines, as they are both organically based and also hydrophilic in nature, have undergone a mammoth amount of screening and testing to discover promising lead structures with a CN3 core, appropriate for potential future drug development. The compounds have the potential to be neurodegenerative therapeutic options, as well as: anti-inflammatory, anti-protozoal, anti-HIV, chemotherapeutic, anti-diabetic agents and so on. It is true that guanidine-based compounds of natural sources also, like synthetic and virtually designed drugs, have been of significant interest and have the potential to be useful therapeutic options in the future. As for now, however, there is not sufficient data to support their use in a number of the suggested areas, and further studies are required.

A 1,3-amino group migration route to form acrylamidines

A novel 1,3-amino group migration strategy for the synthesis of acrylamidines is presented. Cu(i) catalyzed reaction of N,N-disubstituted propargylamine with tosylazide generates a highly reactive ketenimine intermediate which is trapped by a tethered amino group leading to the rearrangement reaction.

Synthesis of cyclic guanidines via Pd-catalyzed alkene carboamination

A new approach to the synthesis of substituted 5-membered cyclic guanidines is described. Palladium-catalyzed alkene carboamination reactions between acyclic N-allyl guanidines and aryl or alkenyl halides provide these products in good yield. This method allows access to a number of different cyclic guanidine derivatives in only two steps from readily available allylic amines.

Biological activities of guanidine compounds, 2008 - 2012 update

INTRODUCTION

Compounds incorporating guanidine moiety have found many practical applications in diverse areas of chemistry, such as nucleophilic organocatalysis, anion recognition and coordination chemistry. Moreover, guanidine functional group is found in natural products, pharmaceuticals and cosmetic ingredients produced by synthetic methods. Thus, knowledge of their biological activities and therapeutic uses is of utmost importance for researchers involved in drug discovery processes.

AREAS COVERED

In this review the authors highlight the continued development and therapeutic applications of newly synthesized guanidine-containing compounds including small peptides and peptidomimetics incorporating arginine. The review presents patents and patent applications filed in the years 2008 - 2012 with emphasis placed on new mechanisms of pharmacological action of guanidine derivatives.

EXPERT OPINION

While guanidines are often thought of as strong organic bases and compounds hydrophilic in nature, over the last 4 years there has been an enormous increase in discovery of new promising lead structures with guanidine core, suitable for development of potential drugs acting at central nervous system, anti-inflammatory agents, anti-diabetic and chemotherapeutic agents as well as cosmetics.

Anti-influenza active and low toxic N-phenyl-substituted β-amidoamidines structurally related to natural antibiotic amidinomycin

A set of racemic N-phenyl-substituted β-amidoamidines hydrochlorides 4, which are structurally related to natural antiviral agent amidinomycin (1), was synthesized in four steps starting from methacryloyl anilide (5). In the final step of the synthetic route, an uncommon monoacylation of β-aminoamidine 8 at the less reactive β-phenylamino-group took place. To rationalize this result, a mechanism which involves initial acylation at the more active amidine-function followed by intramolecular acyl-group transfer to β-phenylamino-group was suggested. All three β-amidoamidines 4d-f bearing long linear aliphatic chain (from n-C8H17 to n-C12H25) revealed significant in vitro activity against influenza A virus (H3N2) and modest cytotoxicity. The in vitro antiviral potency of 4d,e is 6-20 times greater than that of commercial rimantadine with lower EC50 values and higher therapeutic index. The non-toxic in vivo compounds 4d-f showed a beneficial protective effect in influenza A (H3N2) infected mice.

Sustainable synthesis of diverse privileged heterocycles by palladium-catalyzed aerobic oxidative isocyanide insertion

O(2) in, H(2)O out: Various diamines and related bisnucleophiles readily undergo oxidative isocyanide insertion with Pd(OAc)(2) (1 mol %) as the catalyst and O(2) as the terminal oxidant to give a diverse array of medicinally relevant N heterocycles. The utility of this highly sustainable method is demonstrated by a formal synthesis of the antihistamines astemizole and norastemizole.

Pirfenidone structural isosteres: design, synthesis and spectral study

Series of 5-substituted arylpyridin-2(1H)-ones and arylpyrimidin-4(3H)-ones were designed and synthesized based on pirfenidone, a compound which shows promising therapeutic effects for treatment of fibrosis. The compounds 1a–c, 2a–c and 3a–c were obtained under mild conditions by arylation of the appropriate heterocyclic amines with arylboronic acids under Chan-Lam-Evans conditions. The synthesis of the useful synthon N-(4-methoxyphenyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-(1H)-pyridin-2-one (4) is also reported. All compounds were characterized by spectral and elemental analysis and structural elucidation by 1H and 13C NMR is discussed herein.

The chemistry and biology of organic guanidine derivatives

The chemistry and biology of organic natural guanidines are reviewed, including the isolation, structure determination, synthesis, biosynthesis and biological activities of alkaloids, non-ribosomal peptides, guanidine-bearing terpenes, polyketides and shikimic acid derivatives from natural sources.

Palladium-catalyzed N-monoarylation of amidines and a one-pot synthesis of quinazoline derivatives

A method for the Pd-catalyzed N-arylation of both aryl and alkyl amidines with a wide range of aryl bromides, chlorides, and triflates is described. The reactions proceed in short reaction times and with excellent selectivity for monoarylation. A one-pot synthesis of quinazoline derivatives, via addition of an aldehyde to the crude reaction mixture following Pd-catalyzed N-arylation, is also demonstrated.