Alain Méou

Asymmetric Mn(III)-based radical synthesis of functionalized 2,3-dihydrofurans

Abstract The oxidative radical addition of alkyl acetoacetates to p -methoxycinnamoyl oxazolidinones promoted by Mn(III) has been studied. It only gives trans -disubstituted 2,3-dihydrofurans, with d.r. ranging from 2:1 to 9:1, depending on the substituent of the chiral auxiliary. After chromatographic separation of the two diastereomers, the oxazolidinone can be removed to afford enantiopure dihydrofuranyl esters in good overall yield.

Anaerobic 1-Alkene Metabolism by the Alkane- and Alkene-Degrading Sulfate Reducer Desulfatibacillum aliphaticivorans Strain CV2803T

ABSTRACT The alkane- and alkene-degrading, marine sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803T, known to oxidize n-alkanes anaerobically by fumarate addition at C-2, was investigated for its 1-alkene metabolism. The total cellular fatty acids of this strain were predominantly C-(even number) (C-even) when it was grown on C-even 1-alkenes and predominantly C-(odd number) (C-odd) when it was grown on C-odd 1-alkenes. Detailed analyses of those fatty acids by gas chromatography-mass spectrometry after 6- to 10-week incubations allowed the identification of saturated 2- and 4-ethyl-, 2- and 4-methyl-, and monounsaturated 4-methyl-branched fatty acids with chain lengths that correlated with those of the 1-alkene. The growth of D. aliphaticivorans on (per)deuterated 1-alkenes provided direct evidence of the anaerobic transformation of these alkenes into the corresponding 1-alcohols and into linear as well as 10- and 4-methyl-branched fatty acids. Experiments performed with [13C]bicarbonate indicated that the initial activation of 1-alkene by the addition of inorganic carbon does not occur. These results demonstrate that D. aliphaticivorans metabolizes 1-alkene by the oxidation of the double bond at C-1 and by the subterminal addition of organic carbon at both ends of the molecule [C-2 and C-(ω-1)]. The detection of ethyl-branched fatty acids from unlabeled 1-alkenes further suggests that carbon addition also occurs at C-3. Alkylsuccinates were not observed as potential initial intermediates in alkene metabolism. Based on our observations, the first pathways for anaerobic 1-alkene metabolism in an anaerobic bacterium are proposed. Those pathways indicate that diverse initial reactions of 1-alkene activation can occur simultaneously in the same strain of sulfate-reducing bacterium.

Reactions of isocyanides. II- addition to acetals

In the presence of TiCl4, tert-butyl isocyanide reacts with aldehyde acetals to afford β-alkoxycyanoenamines.

Oxygen transfer mechanism in the Mn-salen catalysed epoxidation of olefins

Abstract The Mn-salen catalysed epoxidation of geraniol and nerol derivatives or similar non-conjugated olefins, with H 2 O 2 as oxidant, was studied. Along with the epoxide, rearranged products were isolated and characterised. The formation of these compounds is a strong argument in favour of the formation of an oxametallacycle as an intermediate in these epoxidation reactions.

Microbiological Transformations. 21. An expedient route to both enantiomers of Marmin and Epoxyauraptens via microbiological dihydroxylation of 7-geranyloxycoumarin

Abstract The expedient synthesis of either enantiomers of Marmin or Epoxyauraptens of high enantiomeric purity is described. This was achieved via a stereospecific dihydroxylation of the remote double bond of a geraniol derivative using the fungus Aspergillus niger .

Efficient MnIII-mediated synthesis of functionalized trans-3,4-disubstituted-γ-butyrolactones

The MnIII-induced addition of malonic acid (instead of acetic acid) to cinnamic esters affords in one step functionalized trans-3,4-disubstituted-γ-butyrolactones in a greatly improved yield which can be further optimized by conducting the reaction in either acetic or formic acid, depending on the substrate.

Synthesis of bicyclic γ-lactones promoted by Mn(OAc)3: Regio- and diastereoselectivities

The regio- and diastereoselectivities of Mn(OAc)3-induced addition of monomethyl malonate on some cycloalkenes and cycloalkadienes are studied. The latter is greatly improved when starting from cycloalkadienes.

A new approach toward the synthesis of heterolignans

Abstract The SnCl4-mediated rearrangement of 2,5-disubstituted-2,3-dihydrofurans in which one of the substituents is a heterocycle was developed as a key step for the synthesis of diverse heterolignans.

Controlled synthesis of functionalized mixed thiophene/furan oligomers

A novel and simple synthetic route for the preparation of a series of functionalized mixed thiophene/furan oligomers is described. This method, involving a Mn(OAc)3-mediated oxidative addition of β-thienyl-β-keto esters (=β-oxothiophenepropanoates) to methyl 3-thienylprop-2-enoates, allows the construction of highly functionalized heteropolyaromatic oligomers possessing various chain lengths (Schemes 2, 4, and 5). Moreover, the straightforward transformation of the carbonyl functions appended to the furan rings leads to polycarboxylic acid precursors of H2O-soluble conducting polymers (Scheme 6).

Preparation of optically active aziridine carboxylates by lipase-catalyzed alcoholysis

Abstract Aziridine carboxylates alcoholysis by lipases depends of the N-substituent. N-alkyl and N-aryl compounds have been resolved with medium to good enantiomeric purity by enzymatic alcoholysis catalyzed by pig pancreatic (PPL) or Candida cylindracea lipase (CCL).