A Modular Rearrangement Approach toward Medicinally Relevant Phosphinic Structures

Diastereoselective Synthesis of Phosphinic Dipeptide Isosteres: Domino Chirality Transfer during a Stereocontrolled P-Michael Reaction

A highly diastereoselective P-Michael addition of chiral aminophosphinic acids to achiral acrylates has been developed, leading to phosphinic dipeptide isosteres in high yields and dr of up to >50:1. The method allows for the diastereoselective preparation of target compounds without the need for chiral auxiliaries or P-chiral substrates. A possible mechanistic explanation involves a domino chirality transfer from the aminophosphinic acid to the P center, amplified by a crucial benzhydryl ester group, and then to the α-carbon.

Copper-Catalyzed Reductive Ireland-Claisen Rearrangements of Propargylic Acrylates and Allylic Allenoates

The copper-catalyzed reductive Ireland-Claisen rearrangement of propargylic acrylates led to 3,4-allenoic acids. The use of silanes or pinacolborane as stoichiometric reducing agents and triethylphosphite as a ligand facilitated the divergent and complementary selectivity for the synthesis of diastereomeric anti- and syn-rearranged products, respectively. Copper-catalyzed reductive Ireland-Claisen rearrangement of allylic 2,3-allenoates proceeded effectively only when pinacolborane was used as a reductant to generate various 1,5-dienes in excellent yields and with good diastereoselectivities in some cases. Mechanistic studies showed that the silyl and boron enolates, rather than the copper enolate, underwent a stereospecific rearrangement via a chairlike transition state to afford the corresponding Claisen rearrangement products.

Covalent Inhibition of Bacterial Urease by Bifunctional Catechol-Based Phosphonates and Phosphinates

In this study, a new class of bifunctional inhibitors of bacterial ureases, important molecular targets for antimicrobial therapies, was developed. The structures of the inhibitors consist of a combination of a phosphonate or (2-carboxyethyl)phosphinate functionality with a catechol-based fragment, which are designed for complexation of the catalytic nickel ions and covalent bonding with the thiol group of Cys322, respectively. Compounds with three types of frameworks, including β-3,4-dihydroxyphenyl-, α-3,4-dihydroxybenzyl-, and α-3,4-dihydroxybenzylidene-substituted derivatives, exhibited complex and varying structure-dependent kinetics of inhibition. Among irreversible binders, methyl β-(3,4-dihydroxyphenyl)-β-(2-carboxyethyl)phosphorylpropionate was observed to be a remarkably reactive inhibitor of Sporosarcina pasteurii urease (k_inact/K_I = 10 420 s^-1 M^-1). The high potential of this group of compounds was also confirmed in Proteus mirabilis whole-cell-based inhibition assays. Some compounds followed slow-binding and reversible kinetics, e.g., methyl β-(3,4-dihydroxyphenyl)-β-phosphonopropionate, with K_i* = 0.13 μM, and an atypical low dissociation rate (residence time τ = 205 min).

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.

Stereoselective Synthesis of α-Amino-C-phosphinic Acids and Derivatives

α-Amino-C-phosphinic acids and derivatives are an important group of compounds of synthetic and medicinal interest and particular attention has been dedicated to their stereoselective synthesis in recent years. Among these, phosphinic pseudopeptides have acquired pharmacological importance in influencing physiologic and pathologic processes, primarily acting as inhibitors for proteolytic enzymes where molecular stereochemistry has proven to be critical. This review summarizes the latest developments in the asymmetric synthesis of acyclic and phosphacyclic α-amino-C-phosphinic acids and derivatives, following in the first case an order according to the strategy used, whereas for cyclic compounds the nitrogen embedding in the heterocyclic core is considered. In addition selected examples of pharmacological implications of title compounds are also disclosed.

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.