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The diastereoselective MnIII-promoted radical addition of β-oxo ester 1 onto N-cinnamoyloxazolidinone 2 affords, after removal of the chiral auxiliary, the enantiopure 2,5-diaryl-2,3-dihydrofuran (−)-4. Its SnCl4-induced rearrangement leads to a 4-aryltetralone immediate precursor of the aryltetralin lignan (+)-phyltetralin (9). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

A new SnCl 4 -induced rearrangement of 2,5-diaryl-2,3-dihydrofurans allows a direct and efficient formation of the 4-aryl-2-methylenetetralone skeleton. Its scope and limitations are discussed.

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.

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.

The Mn(OAc)3-mediated hydroxylation of a series of α-carbomethoxy-γ-lactones by molecular oxygen is described. The reaction is regio- and stereoselective and gives α-carbomethoxy-α-hydroxy-γ-lactones. Key words: manganese acetate, γ-lactones, hydroxylation, molecular oxygen.

The Mn-salen catalysed epoxidation of geraniol and nerol derivatives or similar non-conjugated olefins, with H2O2 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.

The 1H and 13C NMR chemical shifts of four 2,5-diaryltetrahydrofuran derivatives and their dihydro precursors were assigned completely with certainty using a concerted application of one- and two-dimensional experiments (DEPT, gs-COSY, gs-HMQC and gs-HMBC)

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.

The structures of three γ-lactone derivatives, methyl 11-oxa-10-oxobicyclo[6.3.0]undec-4-ene-9-carboxylate, C 12 H 16 O 4 , methyl 11-oxa-10-oxobicyclo[6.3.0]undec-2-ene-9-carboxylate, C 12 H 16 O 4 , and methyl 9-oxa-10-oxobicyclo[6.3.0]undecane-11-carboxylate, C 12 H 18 O 4 , have been solved in order to determine the relative configuration of their three asymmetric stereocentres.

The identification of (3, 4-dihydro-2H-pyran-5-yl)-oxo-acetic acid methyl ester has been realized by combination of two dimensional HETCOR and HMBC techniques. 13C and 1H chemical shifts asignements are described.

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).

The regio- and stereoselectivity of Mn III -induced addition of acetic acid, potassium methyl malonate and acetylacetone on methyl sorbate are compared. Depending on the reagent, the regioselectivity is reversed but a good degree of diastereoselectivity is observed in all instances.

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.

We have developed a two-step sequence for preparing a series of macrocyclic oxa- and thiacrown ethers affixed to a thiophene/furan oligomer. The sequence involves the intramolecular MnIII-promoted cyclization of linear diester precursors into 2,3-dihydrofurans, whose dehydrogenation furnishes the title compounds. A preliminary NMR study has shown that one of them seems to specifically chelate Pb2+ cations.

Title compounds can be prepared in one step and good yield from (6S)- or (6R)-6,7-dihydroxygeranyl phenylcarbamate.

The four enantiomerically pure title compounds were prepared in three steps and good yield from (6S)- or (6R)-6,7-dihydroxygeranyl N-phenylcarbamate

The structures of three γ-lactone derivatives, methyl 11-oxa-10-oxobicyclo[6.3.0]undec-4-ene-9-carboxylate, C 12 H 16 O 4 , methyl 11-oxa-10-oxobicyclo[6.3.0]undec-2-ene-9-carboxylate, C 12 H 16 O 4 , and methyl 9-oxa-10-oxobicyclo[6.3.0]undecane-11-carboxylate, C 12 H 18 O 4 , have been solved in order to determine the relative configuration of their three asymmetric stereocentres.

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.

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.

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.

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).

The diastereoselective MnIII-promoted radical addition of β-oxoesters 1 onto N-cinnamoyloxazolidinones 2 afforded 2,3-dihydrofurans 3. After catalytic hydrogenation of the C=C bond, followed by reductive removal of the chiral auxiliary, the resulting enantiopure tetrahydrofurans 5 were transformed in two steps into naturally occurring (–)-virgatusin and (+)-urinaligran and two other, nonnatural, tetrasubstituted THF lignans. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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 .

Different studies during the past decades have demonstrated the utilization of hydrocarbons under anoxic conditions (32, 36). The initial reactions involved in the degradation of some aliphatic, alicyclic, and aromatic hydrocarbons by anaerobic bacteria have been subsequently elucidated elsewhere (4, 8, 24, 25, 29, 37, 38), but still, many gaps remain in the understanding of the anaerobic oxidation of some of these nonpolar molecules. Unsaturated linear hydrocarbons (n-alkenes) are ubiquitous naturally occurring compounds that can be biosynthesized by different (micro)organisms and plants (3, 14). Phytoplankton appears, however, to be one of the major sources of these compounds in aquatic environments. Linear alkenes with 15 to 39 carbon atoms and with one to seven double bonds are known to be produced more or less specifically by microalgae (14). Short-chain n-C15, n-C17, and n-C19 monoenes as well as the highly unsaturated n-C21:6 are among the most commonly encountered. Specific bacterial n-alkenes have also been identified in microbial mats (33, 34). Alkenes are more reactive than aromatic hydrocarbons and alkanes and, thus, are rarely identified as constituents of diagenetic organic matter. Different laboratory incubation studies as well as field studies have indeed revealed the low potential for preservation of n-alkenes during early diagenesis, although differences in the chemical structure and/or diagenetic conditions (e.g., anoxia) may be responsible for differences in reactivity between isomers (14, 18). Still, alkenes are found in some crude oils and condensates, but their origin seems to be related to an abiogenic alteration of n-alkanes in the trap rather than to a direct preservation of original molecules (12). Although the anaerobic degradation of n-alkenes by enrichment cultures (28) and pure denitrifying (17) and sulfate-reducing bacteria (1, 2, 9, 10, 11, 30, 31) has been reported, the initial reactions of these unsaturated hydrocarbons in anaerobic bacteria are still unknown (32). The degradation of 1-hexadecene by methanogenic enrichment cultures was supposed to occur by initial oxidation to 1-hexadecanol and subsequent β-oxidation of hexadecanoic acid (28), but no intermediate metabolite other than acetate could be detected. On the other hand, in some early studies of alkane-degrading microorganisms, an oxygen-independent initial metabolism of alkanes via dehydrogenation to 1-alkenes and oxidation to primary alcohols was suggested (6, 23, 35). In recent investigations, however, alkane dehydrogenation to 1-alkenes was viewed critically (1, 2, 30), and two alternative pathways for the initial oxidation of alkanes in denitrifying or sulfate-reducing bacteria were subsequently described: the addition of fumarate at C-2 (5, 8, 24, 38) and carboxylation at C-3 (5, 29). In the present report, we investigated the anaerobic degradation of 1-alkenes by the sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803T, recently isolated from a polluted marine sediment. This strain, which was proposed as the type strain of a novel species in a new genus of the family Desulfobacteraceae (class Deltaproteobacteria), is able to oxidize C13-C18 n-alkanes and C7-C23 n-alkenes into carbon dioxide during sulfate reduction (10). It was also recently demonstrated to transform anaerobically n-alkanes into fatty acids by the addition of fumarate at C-2 (8). By carefully examining the total cellular fatty acids of D. aliphaticivorans grown on different unlabeled 1-alkenes (C14:1 to C17:1) and on (per)deuterated 1-pentadecene and 1-hexadecene, we could demonstrate that strain CV2803T oxidizes alkenes into fatty acids by the oxidation of the double bond at C-1 (via a primary alcohol) and by the addition of an undefined carbon unit(s) at C-2 and C-3 and at the subterminal carbon of the saturated end of the molecule [C-(ω-1)]. Besides describing the first metabolic pathway of n-alkenes in an anaerobic bacterial isolate, our work demonstrates that diverse initial reactions of n-alkene activation can occur simultaneously in the same strain of sulfate-reducing bacteria.

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.

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).

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.

The title compound, C20H25NO4S, is the precursor mol­ecule for the synthesis of (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, which is selectively formed by an oxidative addition of a β-keto ester.

The yield of substituted γ-lactones obtained by Mn III -mediated addition of potassium monomethyl malonate on cinnamate esters can be optimized by performing the reaction either in acetic or in formic acid, depending on the substrate.

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).

The four enantiomerically pure title compounds were prepared in three steps and good yield from (6S)- or (6R)-6,7-dihydroxygeranyl N-phenylcarbamate

Title compounds can be prepared in one step and good yield from (6S)- or (6R)-6,7-dihydroxygeranyl phenylcarbamate.

Resume La reaction de Wittig est appliquee a la synthese de derives de cyclopropylidǹe-3 propyle fonctionalises en β de la double liaison. Le cyclopropylidenetriphenylphosphorane est oppose a des composes dicarbonyles-1,3 dont une fonction est prealablement protegee sous forme de cetal ou d'acetal. L'hydrolyse conduit aux aldehydes et cetones β-cyclopropylideniques. Leur reduction par l'hydrure de lithium et d'aluminium donne acces aux alcools primaires et secondaires. Les alcools tertiaires sont obtenus par action du methyllithium sur les cetones.

The solvolysis of 3-cyclopropylidene propyl derivatives can involve a participation of the double bond leading to the formation of a new three membered ring.

The 13C nmr spectra of 14 β-cyclopropylidenic alcohols 1 have been determined:[Formula: see text]All the chemical shifts were assigned and the substituent effects are discussed as a function of molecular conformation. The stereochemistry of two diastereoisomers of alcohols 1e (R1 = R3 = H; R2 = R4 = CH3) and 1k (R3 = H; R1 = R2 = R4 = CH3) was established from ir spectroscopy and 1H nmr results.The 13C nmr spectra of products arising from hydrolysis of 3-cyclopropylidene propanol 1a and 4-cyclopropylidene 2-butanol 1b tosylates have been also recorded. The analysis of these data enables us to establish unambiguously the structure and the stereochemistry of the hydrolysis products.

α-Cyclohexylidene-cyclobutylidene, a new ambiphilic carbene, undergoes addition to 1,1-diethoxyethylene and t. butylfumarate and insertion into activated carbon-hydrogen bonds.

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