Design, synthesis and biological evaluation of peptidyl-vinylaminophosphonates as novel cysteine protease inhibitors

Phosphorylation of arenes, heteroarenes, alkenes, carbonyls and imines by dehydrogenative cross-coupling of P(O)-H and P(R)-H

Organophosphorous compounds have recently emerged as a powerful class of compounds with widespread applications, such as in bioactive natural products, pharmaceuticals, agrochemicals and organic materials, and as ligands in catalysis. The preparation of these compounds requires synthetic techniques with novel catalytic systems varying from transition metal, photo- and electrochemical catalysis to transformations without metal catalysts. Over the past few decades, the addition of P-H bonds to alkenes, alkynes, arenes, heteroarenes and other unsaturated substrates in hydrophosphination and other related reactions via the above-mentioned catalytic processes has emerged as an atom economical approach to obtain organophosphorus compounds. In most of the catalytic cycles, the P-H bond is cleaved to yield a phosphorus-based radical, which adds onto the unsaturated substrate followed by reduction of the corresponding radical yielding the product.

Copper-Catalyzed Enaminone C(sp2)-N Bond Phosphonation for Stereoselective Synthesis of Alkenylphosphonates

A direct enaminone C-N bond coupling functionalization that generates a new C-P bond using dialkyl phosphonate for the efficient and stereoselective synthesis of (E)-alkenylphosphonates is reported. The reactions toward target products proceed well with a broad scope, disclosing a valuable new synthetic application of enaminones by the interesting C(sp²)-N bond elaboration.

Tunable Trifunctionalization of Tertiary Enaminones for the Regioselective and Metal-Free Synthesis of Discrete and Proximal Phosphoryl Nitriles

This paper reports an unprecedented trifunctionalization of tertiary enaminones for the synthesis phosphoryl nitriles by the reactions of enaminones with diarylphosphine oxides and trimethylsilyl cyanide (TMSCN) without the use of any metal reagent. Employing tetrabutyl ammonium hydroxide (TBAH) as the catalyst (0.2 equiv) enables discrete cyanophosphonation. On the other hand, selective proximal cyanophosphonation has been realized in the presence of acetic acid only (AcOH).

Enantioselective Synthesis of γ-Phenyl-γ-amino Vinyl Phosphonates and Sulfones and Their Application to the Synthesis of Novel Highly Potent Antimalarials

Racemic and enantioselective syntheses of γ-phenyl-γ-amino vinyl phosphonates and sulfones have been achieved using Horner-Wadsworth-Emmons olefination of trityl protected α-phenyl-α-amino aldehydes with tetraethyl methylenediphosphonate and diethyl ((phenylsulfonyl)methyl)phosphonate, respectively, without any racemization. The present strategy has also been successfully applied to the synthesis of peptidyl vinyl phosphonate and peptidyl vinyl sulfone derivatives as potential cysteine protease inhibitors of Chagas disease, K11002, with 100% de. The developed synthetic protocol was further utilized to synthesize hybrid molecules consisting of artemisinin as an inhibitor of major cysteine protease falcipain-2 present in the food vacuole of the malarial parasite. The synthesized artemisinin-dipeptidyl vinyl sulfone hybrid compounds showed effective in vitro inhibition of falcipain-2 and potent parasiticidal efficacies against Plasmodium falciparum in nanomolar ranges. Overall, the developed synthetic protocol could be effectively utilized to design cysteine protease inhibitors not only as novel antimalarial compounds but also to be involved in other life-threatening diseases.

Base-mediated 1,6-conjugate addition of the Seyferth-Gilbert reagent to para-quinone methides

A 1,6-conjugate addition reaction of the Seyferth-Gilbert reagent (SGR) to p-quinone methides is reported. This base-mediated protocol allows rapid access to diarylmethylated diazomethylphosphonates. The reaction proceeds under mild basic conditions, making it a practical approach for the synthesis of diarylmethylated diazomethylphosphonates with a broad substrate scope. Interestingly, the treatment of the conjugate adduct with a catalytic amount of rhodium acetate resulted in the 1,2-aryl migration of the rhodium carbenoid intermediate to generate the corresponding 1,2-diaryl alkenylphosphonates in excellent yields.

Decarboxylative functionalization of cinnamic acids

Decarboxylative functionalization of α,β-unsaturated carboxylic acids is an emerging area that has been developed significantly in recent years.

Substituent controlled reactivity switch: selective synthesis of α-diazoalkylphosphonates or vinylphosphonates via nucleophilic substitution of alkyl bromides with Bestmann–Ohira reagent

We report a substituent controlled nucleophilic displacement of alkyl bromides with Bestmann–Ohira reagent yielding either dimethyl diazoalkylphosphonates or (E)-vinylphosphonates.