New opinions on the amidoalkylation of hydrophosphorylic compounds

Improved Synthesis of the Selected Serine Protease uPA Inhibitor UAMC-00050, a Lead Compound for the Treatment of Dry Eye Disease

The α-aminophosphonate UAMC-00050, a newly developed trypsin-like serine protease inhibitor, is a lead compound for the treatment of dry eye syndrome and ocular inflammation. The medicinal chemistry route developed at the University of Antwerp possessed several problems hampering the scale-up such as poor yields for some of the steps, hazardous reagents, and environmental footprint. Herein, we report an optimized route for the UAMC-00050, in which environmental unfriendly solvents were excluded, hazardous reagents were replaced with safer alternatives, and are more efficient in terms of atom economy. Every reaction step was optimized to reach a higher yield, and design of experiment was used to find the optimum conditions in the last step. Furthermore, all the flash chromatography purifications of intermediates were replaced with plug filtration, slurry purifications, or crystallization. The overall yield was increased from 3% in the medicinal chemistry route to 22% in the process development route.

N,N-Diacylaminals as Emerging Tools in Synthesis: From Peptidomimetics to Asymmetric Catalysis

N,N-Diacylaminals are flexible molecular scaffolds that have commonly been utilized as amide surrogates in peptidomimetics. The singularities of this motif as an N-acyl imine equivalent and as hydrogen-bond donor have recently opened new synthetic opportunities, especially in the field of asymmetric catalysis. This concept article highlights this diverse synthetic potential and provides the elements necessary for further developments.

Mechanism of Phosphorus-Carbon Bond Formation in the Amidoalkylation of Phosphonous Carboxylic Acids

An unusual greater reactivity of phosphonous propionic acids was found in comparison with phosphonous propionic esters in carbamate version of Kabachnik-Fields reaction. Compounds of tricoordinated phosphorus generated in situ during the amidoalkylation of hydrophosphorylic compounds in acetyl chloride/acetic anhydride mixture were found by ³¹P NMR analysis. A hypothesis is proposed about the generation of spirophosphoranes in situ to explain the mechanism for the formation of the phosphorus-carbon bond in the reaction under study.

Potential chemical transformation of phosphinic acid derivatives and their applications in the synthesis of drugs

The chemical transformation of phosphinic acid is a well-considered mature area of research on account of the historical significant reactions such as Kabachnik-Fields, Mannich, Arbuzov, Michaelis-Becker, etc. Considerable advances have been made over last years especially in metal-catalyzed, free-radical processes and asymmetric synthesis using catalytic enantioselective. As a result, the aim of this synopsis is to make the reader familiar with advances in the approaches of phosphinic acids toward the synthesis of highly functionalized and valuable buildings blocks. Another purpose of this survey is to provide the current status of the applications of phosphinic acids in the synthesis of drugs.

Recent developments in the synthesis and applications of phosphinic peptide analogs

Synthetic pseudopeptides that fit well with the active site architecture allow the most effective binding to enzymes, similar to native substrates in high-energy transition states. Phosphinic acid peptide analogs that comprise the tetrahedral phosphorus moiety introduced to replace an internal amide bond exert such an isosteric or isoelectronic resemblance, combined with providing other advantageous features, for example, metal complexing properties. Accordingly, they are capable of inhibiting metal-dependent enzymes involved in biological functions in eukaryotic and prokaryotic cells. These enzymes are associated with notorious human diseases, such as cancer, e.g., matrix metalloproteinases, or are etiological factors of protozoal and bacterial infections, e.g., metalloaminopeptidases. The affinity and selectivity of these compounds can be conveniently adjusted, either by structural modification of dedicated side chains or by backbone elongation to enhance specific interactions with the corresponding binding pockets. Recent approaches to the synthesis of these compounds are illustrated by examples of the preparation of rationally designed structures of inhibitors of particular enzymes. Activity against appealing enzymatic targets is presented, along with the molecular mechanisms of action and therapeutic implications. Innovative aspects of phosphinic peptide application, e.g., as activity-based probes, and ligands of complexes of radioisotopes for nuclear medicine are also outlined.

Synthesis and modifications of phosphinic dipeptide analogues

Pseudopeptides containing the phosphinate moiety (-P(O)(OH)CH₂-) have been studied extensively, mainly as transition state analogue inhibitors of metalloproteases. The key synthetic aspect of their chemistry is construction of phosphinic dipeptide derivatives bearing appropriate side-chain substituents. Typically, this synthesis involves a multistep preparation of two individual building blocks, which are combined in the final step. As this methodology does not allow simple variation of the side-chain structure, many efforts have been dedicated to the development of alternative approaches. Recent achievements in this field are summarized in this review. Improved methods for the formation of the phosphinic peptide backbone, including stereoselective and multicomponent reactions, are presented. Parallel modifications leading to the structurally diversified substituents are also described. Finally, selected examples of the biomedical applications of the title compounds are given.