Monitoring of reversible boronic acid-diol interactions by fluorine NMR spectroscopy in aqueous media.

Recognition and sensing of various biologically relevant species using boronic acid-based chemosensors have become increasingly popular over the last few years. Herein, we describe a new convenient method for monitoring boronic acid-diol interactions in aqueous media based on (19)F NMR spectroscopy with fluorinated boronic acid probes.

Highly functionalized cyclopentanes from meso bicyclic hydrazines. A rapid access to mannosidase inhibitors.

A simple diastereoselective access to amino- and hydrazinocyclopentitols is described. The key step involves a cationic rearrangement of a meso bicyclic hydrazine, followed by two successive stereoselective hydroxylations. Both racemic compounds are micromolar alpha-mannosidase (Jack bean) inhibitors.

Practical asymmetric synthesis of 1,2-diamines in the 3-aminoazepane series.

A simple and versatile method for the enantio- and diastereoselective synthesis of mono- or disubstituted 3-aminoazepanes is described. The key step involves a highly regio- and diastereoselective tandem ring-enlargement/alkylation or reduction process. This novel synthetic route provides enantiomerically pure constrained diamines interesting as scaffolds for medicinal chemistry.

Enantioselective desymmetrization of meso bicyclic hydrazines: a novel approach to the asymmetric synthesis of polysubstituted amino cyclopentanic cores.

Catalytic asymmetric hydroboration can be successfully applied to meso bicyclic hydrazines. The resulting alcohols are of great synthetic interest and can lead in a straightforward manner to cyclopentanic diamino alcohols with good enantiomeric purity.

Synthesis of enantiomerically pure alpha-substituted propargylic amines by reaction of organoaluminum reagents with oxazolidines.

Various oxazolidines prepared in two steps from (R)-phenylglycinol react at 0 degrees C with dialkylalkynylalane-triethylamine complexes in the presence of trimethylaluminum in high yield and diastereoselectivity. Enantiomerically pure primary alpha-substituted propargylamines can be easily obtained in two steps after removal of ferrocenylmethyl protective group under smooth acidic conditions and oxidative cleavage of the chiral appendage.

Stereoselective preparation and reactions of configurationally defined dialkylzinc compounds

The reaction of cyclic and open-chain diastereomerically pure secondary organoboranes with diisopropylzinc allows the preparation of secondary dialkylzinc reagents with good to excellent retention of configuration as shown by deuterolysis and CuI- and Pd0-mediated reactions with electrophiles. The importance of a high boron-zinc exchange rate to obtain high diastereoselectivity has been shown. Improvement of the configurational stability and stereomeric purity of the zinc intermediates has been obtained by using mono-isopinocampheylborane ((-)-IpcBH2) providing optically active dialkylzinc compounds (up to 96% ee) with enhanced diastereoselectivities.

Toxicity of French Polynesian strains of Gambierdiscus toxicus in cultures.

Seven clonal strains of Gambierdiscus toxicus isolated from three ciguateric areas around Tahiti island were mass cultured and extracted for ciguatoxins and maitotoxin. CTX analogs were detected only in one clone (GTP1), suggesting that CTX production may be strain-dependent. However, this in vitro production of CTXs, which remains fairly poor with regards to the toxicity levels encountered in wild G. toxicus, is not a stable temporal characteristic. On the other hand, maitotoxic compounds were detected in all 7 strains in copious amount, especially in clone GTH2.