A convergent and rapid synthesis of original C2,C3-unsaturated, C11,C13-keto-enol macrocycles with a peloruside A skeleton has been developed. These original unsaturated macrocycles constitute valuable platforms to access peloruside A analogues with high diversity. The four-fragment strategy implemented features two aldol-type couplings with the central C12-C14 building block TES-diazoacetone and a late-stage ring-closing metathesis. Enantiopure analogue 18ab showed antiproliferative activity in the low micromolar range on NCI and MCF7 tumor cell lines.

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alpha-Triisopropylsilyl-alpha-diazoacetone (TIPS-diazoacetone) underwent high-yielding "diazo-side" Mukaiyama aldol-type addition with a range of aryl and alkyl aldehydes when subjected to stoichiometric amount of tetrabutylammonium fluoride at 16 degrees C, in Et(2)0. Robustness of the TIPS group makes TIPS-diazoacetone a stable surrogate for alpha-triethylsilyl-alpha-diazoacetone, on which generation of the corresponding carbanion can still be efficiently achieved under nucleophilic, weakly basic and practical conditions. These results highlight the synthetic potential that can be expected from TIPS-diazoacetone, promising building block for the convergent elaboration of highly functionalised versatile diazocarbonyl compounds. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Aldol-type addition of α-triethylsilyl-α-diazoacetone was achieved under nucleophilic activation by tetrabutylammonium fluoride (TBAF). The use of a semistoichiometric amount of TBAF (protocol P1) provided the corresponding β-hydroxy-α-diazoacetone as the sole product. Alternatively, the use of a catalytic amount of TBAF led to a mixture of β-hydroxy- and β-silyloxy-α-diazoacetone products, which was cleanly desilylated with Et3N·3HF (protocol P2). The weakly basic conditions employed tolerate a wide range of substrates and constitute a high-yielding, convenient complementary procedure to the low-temperature LDA-promoted aldol-type addition of diazoacetone.

A rapid convergent strategy to access unsaturated analogues of peloruside A has been demonstrated. This is depicted as an original C11C12 aldol connection between a C12C20 ketone fragment and a C2C11 pyran fragment bearing an aldehyde function, with high yield and a good level of diastereoselectivity. The desired unsaturated macrocycle was obtained by a late-stage ring closing metathesis reaction.

AbstractAn original and convergent approach to the versatile 5‐hydroxy‐1,3‐diketone scaffold (VI) is described using α‐silyl‐α‐diazoketone (I) as synthetic equivalent of acetone.

α-Triethylsilyl-α-diazoacetone underwent a sequential aldolisation–deprotection–aldolisation process to access the 2-diazo-3-oxo-1,5-dihydroxy skeleton with significant diversity. The diazo group could be efficiently removed by treatment with rhodium acetate to afford the corresponding 5-hydroxy-1,3-diketones.

Under Lewis acid activation, the new α-hydroxy-spiro epoxide scaffold 1a underwent an original tandem Payne/Meinwald rearrangement affording the cyclopentyl hydroxymethylketone 6 in a stereospecific manner, while a Meinwald-type epoxide rearrangement occurred when the derived α-trimethylsilyloxy-spiro epoxide 2a was treated with MABR, yielding stereoselectively the cyclohexane carbaldehyde 9.

The ability of 2-vinyl-4,4-dimethyl-5-oxazolone (VDM), a highly reactive functional monomer, to produce block copolymers by reversible addition fragmentation chain transfer (RAFT) sequential polymerization with methyl acrylate (MA), styrene (S), and methyl methacrylate (MMA) was investigated using cumyl dithiobenzoate (CDB) and 2-cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents. The results show that PS-b-PVDM and PMA-b-PVDM well-defined block copolymers can be prepared either by polymerization of VDM from PS-and PMA-macroCTAs, respectively, or polymerization of S and MA from a PVDM-macroCTA. In contrast, PMMA-b-PVDM block copolymers with controlled molecular weight and low polydispersity can only be obtained by using PMMA as the macroCTA. Ab initio calculations confirm the experimental studies. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5053-5062, 2010

Electrochemical behaviour of a functionalized fluorenylidene 1 is studied in comparison with a cyclopentadithiophene analogue 2. The influence of the main aromatic group on the electropolymerization ability is reported. We demonstrated that the lack of sulfur atoms in the monomer structure leads to an absence of polymerization due to the spin density located on the methylidene bridge in the radical cation. From modelling considerations, we have evaluated the participation of the methylidene bridge in the p-doping process. The good correlation between the p-doping level and the partial atomic charge carried by the methylidene bridge for poly(2) and poly(3) indicates that an extension of the conjugated area improves the p-doping level when the side chain is electronically connected to the main chain of polymer.

Formation of a furan derivative was observed in the course of a synthetic approach towards a new carotenoid metabolite, starting from a propargylic ketone, in the presence of mercuric triflate-tetramethylurea complex.

A simple and efficient methodology to introduce an 1,3-diketone motif from various aldehyde precursors in three steps with good overall yields is described using β-ketosulphone 7 as masked equivalent of acetone.

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The treatment of (+)- or (−)-fenchones epoxides with 1:2 85% H3PO4:DMSO for 30 min at 20°C induced an enantiospecific Wagner–Meerwein rearrangement affording new C(10)-O-substituted camphor derivatives which could prove useful as chiral auxiliaries.

Both (-)-geosmin and (+)-2-methyl-isoborneol are the main compounds responsible for the unpleasand smells found in the vicinity of water-processing plant. Attempts to eliminate them using oxidation, filtration and/or biologic degradation processes are only partly efficient. The use of cage molecules could provide an alternative solution. In this respect, cyclodextrins and derivatives have demonstrated their role as candidates as hosts for these highly hydrophobic compounds. In this paper, we evidence the complexation of above mentionned pollutants by cyclodextrins using high-resolution proton Nuclear Magnetic Resonance spectroscopy. The latter method is also used to afford a three-dimensional structure of inclusion complexes in solution and to show that cyclodextrins can as well discriminate between the optical isomers of synthetic geosmin and methyl-isoborneol. Finally, a solution to the problem of waste waters is proposed.

A new synthetic route to T-Damasoone 1 starting with methyl-T-dithiocyclogeranate 2 is described. Addition of RMPT was found necessary to perfon the carbophilic addition of allylmagnesium bromide on ditkioester 2. A dienysulfide, 6,6-dimethyl-2-methylene-(l-methylthio-l,3-butadiene)-l-yl cyclohexane 3, resulted from this addition, and not the expected dithioketal. Following a number of described condition, hydrolysis of 3 to T-damascone 1 proved to be unsatisfactory. These initial attempts but showed the necessity for an acidic medium, This finding allowed the development of a new, very mild method of hydrolysis of dienylsulfides to unsaturated ketones.

Methyl γ-dithiocyclogeranate, a new terpenic dithioester. was easily synthesized by the [2,3]-sigmatropic rearrangement of tosylhydrazone derivative 6a. Treatment with acid gives methyl α-dithiocyclogeranate. Three methoxylated analogues are obtained in the same way.

A new synthetic route to γ-damasoone 1 starting from methyl-γ-dithiocyclogeranate 2 is described. Addition of HMPT is found necessary to perform the reaction of allyllmagnesium bromide with dithioester 2. A new, very mild hydrolysis method is developped in order to transform the resulting vinylsulfide 4 into 1.