Frédéric Garzino

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.

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).

SnCl4 Mediated Rearrangement of α-Aroyl-γ-butyrolactone: Reinvestigation of the Mechanism

The mechanism of SnCU-mediated rearrangement of a-aroyl-y-butyrolactones into aryl tetralones was reinvestigated and was compared to the rearrangement of 2,5-diaryl-2,3-dihydrofiirans using the same conditions. We have shown that in fact lactone is converted into dihydrofuran which then is rearranged into a tetralone. 4-aryltetralones are highly valuable synthons used as key intermediates for the synthesis of biologically active compounds such as Sertraline (Zoloft®) (1), ABT-431 (2-3) and many other active molecules (4-8). Two efficient syntheses of 4-aryltetralones such as 1, based on a SnCU-induced rearrangement of oxygenated heterocycles like 2,5-diary!-2,3-dihydrofiiran 2 (9) or a-aroyl-^butyrolactone 3 (10) have been reported in literature (Scheme 1). SCHEME 1. synthesis of 4-aryltetralones Results and discussion SnCU-induced rearrangement of the a-aroyl-^-butyrolactone 3 is an efficient method to obtain the 4aryltetralone 1 as the key step for the synthesis of the Bristol-Myers precursor of the well known anticancer agent podophyllotoxin,. After 24h, this reaction cleanly led to 1 in 91% yield According to the authors, the Introduction

(2R,3R)‐2‐(4‐Methoxy­phenyl)‐3‐{1‐[(3aS)‐(3aα,6α,7aα)‐hexa­hydro‐8,8‐di­methyl‐3H‐3a,6‐methano‐2,2‐dioxo‐2,1‐benzoiso­thia­zolyl]­carbonyl}‐4‐isopropoxy­carbonyl‐5‐methyl‐2,2‐di­hydro­furan

The title compound, C27H35NO7S, is selectively formed by the oxidative addition of a β-keto ester to a chiral N-cinnamoyl derivative. The determination from X-ray analysis of the absolute configuration of two newly created stereogenic centres allows us to understand the facial selectivity of the addition.