Cyril Rousseau

Artificial enzymes, "chemzymes": current state and perspectives.

Enzymes have fascinated scientists since their discovery and, over some decades, one aim in organic chemistry has been the creation of molecules that mimic the active sites of enzymes and promote catalysis. Nevertheless, even today, there are relatively few examples of enzyme models that successfully perform Michaelis–Menten catalysis under enzymatic conditions (i.e., aqueous medium, neutral pH, ambient temperature) and for those that do, very high rate accelerations are seldomly seen. This review will provide a brief summary of the recent developments in artificial enzymes, so called “Chemzymes”, based on cyclodextrins and other molecules. Only the chemzymes that have shown enzyme-like activity that has been quantified by different methods will be mentioned. This review will summarize the work done in the field of artificial glycosidases, oxidases, epoxidases, and esterases, as well as chemzymes that catalyze conjugate additions, cycloadditions, and self-replicating processes. The focus will be mainly on cyclodextrin-based chemzymes since they have shown to be good candidate structures to base an enzyme model skeleton on. In addition hereto, other molecules that encompass binding properties will also be presented.

Cyclodextrins containing an acetone bridge. Synthesis and study as epoxidation catalysts

Three cyclodextrine derivatives (6A,6D-di-O-(prop-2-one-1,3-dienyl)-alpha-cyclodextrin (1), 6-O-(prop-2-one-1-yl)-alpha-cyclodextrin (2) and 6A,6D-di-O-(prop-2-one-1,3-dienyl)-beta-cyclodextrin (3)) were synthesised and investigated as epoxidation catalysts. The three compounds were synthesised from the corresponding perbenzylated cyclodextrins which were mono- or didebenzylated in the 6-position using Sinaÿs method. Reaction with NaH and methallyl chloride in the case of 2, or methallyl dichloride in the case of 1 and 3, followed by dihydroxylation, periodate cleavage and protection group removal gave the target compounds. All three compounds catalysed, in the presence of oxone, the epoxidation of a series of alkenes. Epoxidation was compared to the reaction catalysed by simple ketones and inhibition was studied.

1,2-Glycerol Carbonate: A Versatile Renewable Synthon

INTRODUCTION been investigated using lipase-catalysed acetylation and/or alcoholysis [5a]. More recently, self-condensation to oligomers has been explored [6], but little has been developed on chemical transformations of 2 when treated with various nucleophiles. Our interest is focused on the versatility of such an activated form of glycerol as a multielectrophilic synthon in which the primary hydroxyl group can also be activated (Scheme 2). Glycerol carbonate might Valorisation of glycerol 1 is becoming a crucial challenge for industrial companies: this small molecule appears as a major side-product during manufacturing of bio-diesels, fatty acids and surfactants [1]. This abundant and renewable itol is a prochiral C-3 synthon which has been widely investigated and used as raw material [2]. Among the glycerol-based

First polymer “ruthenium-cyclopentadienyl” complex as potential anticancer agent

d-glucose end-capped polylactide ruthenium cyclopentadienyl complex (RuPMC) was newly synthesized by a straightforward method. RuPMC was tested against human MCF7 and MDAMB231 breast and A2780 ovarian adenocarcinoma revealing IC50 values in the micromolar range. A pH dependent hydrolysis is advanced by preliminary UV-visible spectroscopy. Cellular distribution studies showed that RuPMC is predominantly found in the nucleus and in the membrane. Data suggest potential application of RuPMC as a new drug delivery system for Ru(II)Cp compounds.

Selective discrimination of cyclodextrin diols using cyclic sulfates.

A method for selective monofunctionalition of readily available cyclodextrin diols (2(A-F),3(A-F),6(B,C,E,F)-hexadeca-O-benzyl-alpha-cyclodextrin and 2(A-G),3(A-G),6(B,C,E-G)-nonadeca-O-benzyl-beta-cyclodextrin) by regioselective nucleophilic opening of their cyclic sulfates is presented. Although the A and D products are nonequivalent in beta-cyclodextrin, only the A product is formed.

Synthesis of bergenin-related natural products by way of an intramolecular C-glycosylation reaction

Abstract The peracetate of tri-O-methylnorbergenin 16 as well as the cis-fused epimer of 16, which constitutes the core C-aryl glycosidic fragment of castacrenin B, were prepared by way of the IDCP-mediated intramolecular C-arylation of a pentenyl β- d -glucopyranoside carrying, at O-2, a 3,4,5-trimethoxybenzyl substituent.

Synthesis of benzo[5,6]cyclohepta[b]indol-6-one derivatives

Abstract An effective synthesis of 5,6,11,12-tetrahydrobenzo[5,6]cyclohepta[b]indole-6-ones 2 was reported. Reactivity studies of the compound 2a led us to the preparation of 11-substituted derivatives 9–13 via the palladium-mediated cross-coupling reactions or an elimination-addition reaction.

Direct Experimental Evidence for the High Chemical Reactivity of α‐ and β‐Xylopyranosides Adopting a 2,5B Conformation in Glycosyl Transfer

The effect of a (2,5)B boat conformation on xyloside reactivity has been investigated by studying the hydrolysis and glycosylation of a series of synthetic xyloside analogues based on a 2-oxabicyclo[2.2.2]octane framework, which forces the xylose analogue to adopt a (2,5)B conformation. The locked β-xylosides were found to hydrolyze 100-1200 times faster than methyl β-D-xylopyranoside, whereas the locked α-xylosides hydrolyzed up to 2×10(4) times faster than methyl α-D-xylopyranoside. A significant rate enhancement was also observed for the glycosylation reaction. The high reactivity of these conformers can be related to the imposition of a (2,5)B conformation, which approximates a transition state (TS) boat conformation. In this way, the energy penalty required to go from the chair to the TS conformation is already paid. These results parallel and support the observation that the GH-11 xylanase family force their substrate to adopt a (2,5)B conformation to achieve highly efficient enzymatic glycosidic bond hydrolysis.

Ring opening polymerization of ε-caprolactone in the presence of wet β-cyclodextrin: effect of the operative pressure and of water molecules in the β-cyclodextrin cavity

The ring opening polymerization (ROP) of e-caprolactone (CL) in the presence of β-cyclodextrin (β-CD) was performed in batch reactors both at room pressure and with the reaction system pressurized with CO2, N2 or Ar. Significant enhancements of the polymerization rate was observed when the ROP was carried out with wet β-CD under pressure. For example, after 24 hours at 120 °C with a β-CD/CL molar ratio of about 1/100, the monomer conversion increased from 4 to 98–99% when the pressure was changed from 0.1 to 12.5–13.0 MPa independent of the nature of the compressing gas. MALDI-TOF analyses indicated that a major fraction of polymer chains obtained in pressurized systems was initiated by water molecules. The collected results suggest that at 12–13 MPa wet β-CD can catalyse both the ring opening of e-caprolactone and the polymerization of the obtained linear species and that high energy water molecules located inside the cavity of the cyclic oligosaccharide must play a role in initiating the polymerization. The trend of number average molecular weight and the results of MALDI-TOF analyses obtained in polymerizations performed for long reaction times and in a hydrolysis test of commercial poly(e-caprolactone) indicate that wet β-CD can work as an artificial lipase enzyme under the adopted conditions.

Unconventional media and technologies for starch etherification and esterification

Among the most widespread starch derivatives, etherified and esterified starches play an important role. These derivatives are generally prepared by using thermal energy and conventional solvents. This review summarizes the recent advancements in the etherification and esterification of starch in unconventional media, i.e. ionic liquids or supercritical CO2, and by employing unconventional technologies, i.e. microwaves, ultrasounds or ball-milling. The present contribution aims to provide an overview to help researchers seeking an alternative medium or technology to functionalize starch. The green aspects of unconventional approaches are presented and the physical-chemical properties of modified starches obtained by these approaches are also described. Whenever possible, the advantages and disadvantages of each system are discussed. Finally, even if it is not always mentioned in the publications, the use of these experimental conditions probably leads to a partial degradation of the starch molecular structure.