René Grée

The Small Organic Compound HA14-1 Prevents Bcl-2 Interaction with Bax to Sensitize Malignant Glioma Cells to Induction of Cell Death

A functional imbalance between proapoptotic Bax and antiapoptotic Bcl-2 is likely to participate in the resistance of cancer cells to therapy. We show here that ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate (HA14-1), a small organic compound recently proposed to function as an inhibitor of Bcl-2, increases the sensitivity of human glioblastoma cells to radiotherapy and chemotherapy. This sensitizing effect is lost if Bcl-2 expression, but not Bcl-xL expression, is knocked down or if cells only express a mutant of Bax that does not interact with Bcl-2. This points to a specific Bcl-2 inhibitory function of HA14-1 and implies that it selectively involves hindrance of Bcl-2 binding to Bax, which HA14-1 inhibits in cell-free assays and in cells in receipt of an apoptotic stimulation. Moreover, HA14-1, in combination with a cytotoxic treatment, slows down the growth of glioblastoma in vivo. Thus, the inhibition of Bcl-2 achieved by HA14-1 might improve treatment outcome.

Synthese de cyclopropanes electrophiles chiraux par l'intermediaire de complexes butadiene-fer tricarbonyle optiquement actifs.

Resume Chiral electrophilic cyclopropanes are prepared, in high enantiomeric excess (e.e > 90 %) starting from the optically active complexes 3a and 3b . A simple and efficient method. for the resolution of the key intermediate complex 1 is described.

Syntheses asymetriques a l'aide d'oxazolidines chirales derivees de l'ephedrine. Preparation de formyl cyclopropanes chiraux.

Resume Chiral oxazolidines 2 are very simple and highly efficient inducing groups for asymmetric synthesis during cycloaddition reactions. Chiral Formyl cyclopropanes are easily obtained in high enantiomeric excess (⩾ 90 %).

Tandem Prins/Friedel–Crafts Cyclization for Stereoselective Synthesis of Heterotricyclic Systems

Homoallylic substrates such as (E)-6-arylhex-3-enyl alcohols, N-tosylamides, and thiols undergo smooth cross-coupling with various aldehydes in the presence of 10 mol % Sc(OTf)(3) and 30 mol % TsOH to afford the trans-fused hexahydro-1H-benzo[f]isochromenes, N-tosyloctahydrobenzo[f]isoquinolines, and hexahydro-1H-benzo[f]isothiochromenes, respectively. However, the cross-coupling of (Z)-olefins such as 6-arylhex-3-enyl alcohols, N-tosylamides, and thiols with aldehydes affords the corresponding hexahydro-1H-benzo[f]isochromenes, N-tosyloctahydrobenzo[f]isoquinolines, and hexahydro-1H-benzo[f]isothiochromenes with complete cis selectivity via intramolecular Prins-, aza-Prins-, and thia-Prins/Friedel-Crafts cyclizations, respectively. Though the Prins cyclization proceeds smoothly under the influence of Sc(OTf)(3), high conversions and enhanced reaction rates are achieved using a mixture of Sc(OTf)(3) and TsOH (1:3).

Flexible Synthesis of Pyrimidines with Chiral Monofluorinated and Difluoromethyl Side Chains

Chiral pyrimidines with a fluorine atom in the benzylic position are easily accessible in high enantiomeric excesses from optically active propargylic intermediates by two complementary routes. Both the use of optically active propargylic fluorides and the fluorination of the chiral pyrimidine in the final stage give excellent results in terms of enantiocontrol. On the other hand, original pyrimidines with a difluoromethyl side chain are also obtained in a few steps from new propargylic ketones bearing a CHF(2) substituent on the triple bond.

From allylic alcohols to aldols via a novel, tandem isomerization–condensation catalyzed by Fe(CO)5

Allylic alcohols react with aldehydes, in the presence of catalytic amounts of Fe(CO)5 and under irradiation, to give mainly aldol products. A small amount of ketone resulting from the classical isomerization process is also isolated. This new aldol-type reaction is a complete atom economy process occurring under neutral conditions.

Trimethylsulfonium Methylsulfate, A Simple and Efficient Epoxidizing Agent

Abstract Sulfonium salts 1 and 3 are highly reactive epoxidizing agents under phase transfer catalytic conditions.

Versatile intramolecular aza-Prins and Prins cyclization of aryl epoxides: a facile synthesis of diaza-, oxa-aza-, and dioxa-bicycles.

Aryl epoxides undergo coupling smoothly with (E)-hex-3-ene-1,6-ditosylamide in the presence of 10 mol % p-TSA in 1,2-dichloroethane at 75 degrees C to produce the corresponding 1,5-ditosyl-octahydro-1H-pyrrolidino[3,2-c]pyridines in good yields with high trans-selectivity, whereas the coupling of (Z)-hex-3-ene-1,6-ditosylamide gave cis-fused octahydro-1H-pyrrolidino[3,2-c]pyridines predominantly. The use of readily available p-TSA makes this method simple, convenient, and practical.

From allylic alcohols to saturated carbonyls using Fe(CO)5 as catalyst: scope and limitation studies and preparation of two perfume components

Abstract The direct conversion of allylic alcohols to saturated carbonyls, using Fe(CO) 5 as a catalyst, offers good synthetic potential. Mono-, di- and even trisubstituted alkenes bearing various alkyl, aryl and electronwithdrawing groups on the allylic system give good to excellent yields of rearranged products. Limitations occur mainly with polyunsaturated derivatives. This reaction was applied to a short and efficient synthesis of cyclamen aldehyde and foliaver.

Unprecedented synergistic effects between weak Lewis and Brønsted acids in Prins cyclization

Novel synergistic effects between Lewis and Brønsted acids in Prins cyclization are reported. Non-reactive Lewis acids and non-reactive Brønsted acids, which failed to perform Prins cyclization when used alone, have shown remarkable synergistic effects when used in combination to perform the reaction successfully.