Lanthanide complexes in multifunctional asymmetric catalysis.

Molecular recognition of protein-ligand complexes : applications to drug design

An Overview of Stereoselective Synthesis of α-Aminophosphonic Acids and Derivatives

In this review, recent advances in catalytic asymmetric hydrophosphonylation of aldehydes and imines are discussed. We also summarize several proposed mechanisms for the different possibilities of asymmetric induction and the application of this catalytic methodology to the enantioselective synthesis of α-amino and α-hydroxy phosphonates. A variety of metal-based chiral catalysts as well as several organic catalysts have been exploited as suitable systems for the preparation of enantiomerically pure phosphonates. The recent evolution and future trends of those and other catalytic systems are described.

Catalytic enantioselective hydrophosphonylation of aldehydes and imines

The Kabachnik–Fields (phospha-Mannich) reaction involving the condensation of primary or secondary amines, oxo compounds (aldehydes and ketones) and >P(O)H species, especially dialkyl phosphites, represents a good choice for the synthesis of α-aminophosphonates that are of significant importance due to their biological activity. In general, these three-component reactions may take place via an imine or an α-hydroxy-phosphonate intermediate. The monitoring of a few Kabachnik–Fields reactions by in situ Fourier transform IR spectroscopy has indicated the involvement of the imine intermediate that was also justified by theoretical calculations. The Kabachnik–Fields reaction was extended to >P(O)H species, comprising cyclic phosphites, acyclic and cyclic H-phosphinates, as well as secondary phosphine oxides. On the other hand, heterocyclic amines were also used to prepare new α-amino phosphonic, phosphinic and phosphine oxide derivatives. In most cases, the synthesis under solvent-free microwave (MW) conditions is the method of choice. It was proved that, in the cases studied by us, there was no need for the use of any catalyst. Moreover, it can be said that sophisticated and environmentally unfriendly catalysts suggested are completely unnecessary under MW conditions. Finally, the double Kabachnik–Fields reaction has made available bis(phosphonomethyl)amines, bis(phosphinoxidomethyl)amines and related species. The bis(phosphinoxidomethyl)amines serve as precursors for bisphosphines that furnish ring platinum complexes on reaction with dichlorodibenzonitriloplatinum.

https://www.mdpi.com/1420-3049/17/11/12821/pdf

The Kabachnik-Fields reaction: mechanism and synthetic use.

The synthesis of a series of N-phosphonalkyl dipeptides 6 is described. Syntheses were devised that allowed the preparation of single diastereoisomers and the assignment of stereochemistry. The compounds were evaluated in vitro for their ability to inhibit the degradation of radiolabeled collagen by purified human lung fibroblast collagenase. Several of the compounds were potent collagenase inhibitors and were at least 10-fold more potent than their corresponding N-carboxyalkyl analogues. Activity was lost when the phosphonic acid group P(O)(OH)2 was replaced by the phosphinic acid groups P(O)(H)(OH) and P(O)(Me)(OH). At the P1 position, (R)- or (S)-alkyl groups, especially ethyl and methyl (e.g., 12a,b, 52a,b, and 53a,b), or an (R)-phenethyl moiety (55a) conferred high potency (IC50 values in the range 0.23-0.47 microM). (S)-Stereochemistry was preferred for the P1' isobutyl side chain. Structure-activity relationships were also investigated at the P2' site, and interestingly, compounds with basic side chains, such as the guanidine 57a, were equipotent with more lipophilic compounds, such as 52a. As with other series of collagenase inhibitors, potency was enhanced by introducing bicyclic aromatic P2' substituents. The most potent phosphonic acid of the series was the bicyclic aromatic P2' tryptophan analogue 59a (IC50 0.05 microM).

Synthesis of novel N-phosphonoalkyl dipeptide inhibitors of human collagenase

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Production of value-added substances from the electrochemical oxidation of volatile organic compounds in methanol medium

This paper is focused on the electrochemical degradation of several substituted benzenes as models of volatile organic compounds, as a first step in the degradation of these species during electrochemically assisted absorption process. To do this, the influence of the electrode material (using DSA® and BDD), supporting electrolyte and current intensity is evaluated and intermediates are characterized in order to propose a mechanism that explains the degradation of these species. Results demonstrate that the reactivity of these species increases with the number of methyl substitutions on the benzene ring. Removal efficiencies of BTX compound (for a specific applied electric charge of 7.2 A h dm−3) were higher than 95%, showing that the electrochemical process is functional for this kind of organic compound. On the other hand, removal of TOC was from 65% to 90 %, so it confirms that mineralization is the main pathway in BTX degradation by electro-oxidation. No aromatic intermediates were detected in the electrolysis performed with DSA®, while in the ones performed with BDD were found phenol, quinones and aldehydes, normally detected in electro-oxidation of aromatic compounds. These results are an important step in understanding the mechanisms involved in the electrochemical oxidation of BTX in water matrices. 

R. C. De Mello

Papers

Synthesis of novel N-phosphonoalkyl dipeptide inhibitors of human collagenase

Production of value-added substances from the electrochemical oxidation of volatile organic compounds in methanol medium

Electrolytic removal of volatile organic compounds: keys to understand the process

Combination of granular activated carbon adsorption and electrochemical oxidation processes in methanol medium for benzene removal

Synthesis of Novel N‐Phosphonoalkyl Dipeptide Inhibitors of Human Collagenase.