Thierry Le Gall

The Chemistry of Vicinal Diamines

Especially in the field of enantioselective synthesis, vicinal diamines (1,2-diamines) 1 and compounds easily prepared from them-such as 1,2-bisimines, 1,2-diamides, or imidazolidin-2-ones-are widely used by organic chemists. Various strategies have been developed to produce these compounds selectively. Many natural products and medicinal agents also contain a 1,2-diamino unit.

Enantioselective Synthesis of α‐Amino Acids and Monosubstituted 1,2‐Diamines by Conjugate Addition of 4‐Phenyl‐2‐oxazolidinone to Nitroalkenes

The addition of the potassium salt of (R)- or (S)-4-phenyl-2-oxazolidinone to monosubstituted nitroalkenes proceeded with very good diastereoselectivity. Several of the addition products were converted into α-amino acids and monosubstituted 1,2-diamines of high enantiomeric purity.

Face selectivity during the cycloaddition reaction of nitrile oxides with iron complexed trienes

Abstract Various nitrile oxides were reacted with iron complexed trienes of type 1. The reaction proceeded with good yield and diastereoselectivity (c.a. 90 10 ) to give Δ2-isoxazolines which structures were determined by X-Ray and 1H-NMR spectroscopy.

High-throughput evaluation of antioxidant and pro-oxidant activities of polyphenols with thymidine protection assays

A recently reported high‐throughput screening strategy has been applied to the rapid selection of new water‐soluble antioxidants that display strong protective activities. Based on a competitive immunoassay, a triple‐screening procedure was used to evaluate the ability of different compounds to protect thymidine under different oxidative stresses. The pro‐oxidant effect of norbadione A in the presence of iron was observed, while some pulvinic acid derivatives proved strongly protective during γ radiolysis, UV irradiation, and Fenton‐like oxidation.

An organo-iron mediated chiral synthesis of (+)-(S)-[6]-gingerol

Abstract A short and efficient synthesis of (+)-(S)-[6]-Gingerol is described. The key step is a highly stereoselective cycloaddition of a nitrile oxide with a chiral iron complexed triene.

Evaluation of antioxidant properties of monoaromatic derivatives of pulvinic acids.

The natural mushroom pigment Norbadione A and three other pulvinic acids were shown by our group to display very efficient antioxidant properties by comparison with a collection of potent molecules including catechols, flavonoids, stilbenes, or coumarins. Despite numerous publications on robust and straightforward synthetic access to pulvinic acids by us and others, no report has been made to unravel the structure-activity relationships that govern the striking antioxidant activity. Herein is presented the synthesis of 18 diverse pulvinic acid derivatives and the study of their radical scavenging capacities by four different assays. The influence of each of the two phenyl rings, of their substituents and of the lateral chain on the antioxidant properties, was explored to reveal a simplified structure of excellent activity. These results, along with the absence of cytotoxicity, make the synthesized compounds interesting to evaluate for several biological activities and especially for anti-inflammatory effects and skin protection against UV induced oxidative stress.

First synthesis of both enantiomers of the biotin vitamer 8-amino-7-oxopelargonic acid

Abstract A short and efficient synthesis of both 8-amino-7-oxopelargonic acid enantiomers from d or l -alanine is presented. The key step of this first chemical synthesis is the non-racemizing Horner-Wadsworth-Emmons reaction of a β-ketophosphonate 3 and benzyl 4-formylbutanoate. The growth-promoting effect of the enantiomers was tested on Saccharomyces cerevisiae .

Synthesis of unsaturated trihydroxy C18 fatty acids

Abstract Two trihydroxy unsaturated C 18 fatty acids [(9R, 12S, 13R)-trihydroxy-10E-octadecenoic acid 3 and its 9-epimer 4 ] were synthesized, starting from tri-O-acetyl- d -glucal.

Enantioselective synthesis of α-amino acids from nitroalkenes

The products of the conjugate addition of (R)-4-phenyl-2-oxazolidinone on monosubstituted nitroalkenes were converted into d-α-amino acids of high enantiomeric purity.

A Powerful Antiradiation Compound Revealed by a New High-Throughput Screening Method

We present a new high‐throughput screening method for the selection of powerful water‐soluble antiradiation compounds. This method, which uses conventional immunoassay techniques, allowed the capacity of a given compound to protect thymidine from irradiation to be evaluated. By applying this assay to an antioxidant library, we showed for the first time that norbadione A, a well‐known mushroom pigment, has pronounced atypical antiradiation properties.