First total synthesis of 1-O-beta-D-glucopyranosyl-5-deoxyadenophorine and its aglycon congener: determination of the absolute configuration

The first total synthesis of the potent glycosidase inhibitors 1-O-beta-D-glucopyranosyl-5-deoxyadenophorine and its aglycon congener is described in respectively 13 steps (9% overall yield) and 9 steps (29% overall yield) from (R)-Garner aldehyde. The synthesis takes advantage of several key reactions including a diastereoselective allylation of a chiral imine, a stereoselective epoxidation, and a glycoside coupling. In addition this study established unambiguously the absolute configuration of the natural products.     

Sustainable Heck–Matsuda Reaction with Catalytic Amounts of Diazonium Salts: An Experimental and Theoretical Study

The palladium‐catalyzed Heck–Matsuda reaction with a catalytic amount of an in‐situ‐generated diazonium salt proceeded under mild and sustainable conditions. The reaction proceeded at room temperature, under base‐free conditions, and only generated tBuOH, H₂O, and N₂ as by‐products. Ortho‐substituted diazonium salts were more‐efficiently coupled to methyl acrylate than their corresponding para isomers, which required the addition of anisole as an additive. In support of these experimental data, we carried out theoretical studies to gain a deeper understanding of these reaction outcomes.     

A highly selective colorimetric and fluorescent chemosensor for Cr2+ in aqueous solutions

A new rhodamine-based chemosensor was synthetized through a modified copper-catalyzed [3+2]-cycloaddition of an azidocoumarin with an alkynyl-rhodamine. Its sensing properties toward various metal cations in aqueous solutions were investigated by colorimetric changes, UV–vis and fluorescence spectroscopies. The sensor exhibited a high selectivity for Cr²⁺ over Cr³⁺ and other divalent cations such as Cu²⁺, Mg²⁺, Zn²⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺ and Ni²⁺. The linear range of detection by fluorescence spectroscopy is 0.07–3.5 mM, with a detection limit of ca. 64 μM. The binding mode of Cr²⁺ with the sensor was rationalized through experimental evidences.     

Unprecedented substoichiometric use of hazardous aryl diazonium salts in the Heck-Matsuda reaction via a double catalytic cycle

The first Heck-Matsuda reaction using a catalytic amount of diazonium salts has been discovered. The reaction proceeds through an unprecedented double catalytic cycle in which the electrophile is in situ generated through the reaction advancement. This concept features mild and safe conditions as hazardous aryl diazonium salts are not isolated anymore. Importantly, this sustainable procedure generates only environmentally friendly byproduct such as t-BuOH, H(2)O, and N(2).     

Suzuki-Miyaura reactions of arenediazonium salts catalyzed by PD(0)/C. One-pot chemoselective double cross-coupling reactions

The Suzuki-Miyaura cross-coupling of arenediazonium tetrafluoroborate salts with boronic acid partners catalyzed by Pd(0)/C is described as a practical and efficient alternative to classical homogeneous conditions. Reactions conducted in alcoholic solvents proved to be extremely fast using mild conditions. Additionally, we developed a chemoselective double Suzuki-Miyaura cross-coupling in a single reaction vessel allowing the synthesis of unsymmetrical terphenyls.     

Synthesis and biological evaluation of hydrophilic embelin derivatives

In continuance of our search for newer anti-cancer agents we were interested on embelin, a XIAP (X-linked inhibitor of apoptosis protein) inhibitor. This natural benzoquinone bear a lipophilic chain and we report here the synthesis of hydrophilic analogues of embelin. To allow a large flexibility in the nature of the hydrophilic group, three amines with different length of carbon chain bearing a protected benzoquinone were prepared. The cytotoxic effects of these derivatives were evaluated on KB cell line.     

Synthesis of indanones by sequential Heck-reduction–cyclization–alkylation (HRCA) reactions

A simple and efficient synthesis of indanones, bearing a quaternary carbon centre, has been developed. The method features, in a one-pot process, the use of a multi-task palladium catalyst for the sequential Heck-reduction reactions, followed by a base-mediated cyclization–alkylation sequence. This methodology, called Heck-reduction–cyclization–alkylation (HRCA), is carried out under mild and simple experimental conditions with the use of inexpensive reagents. The mild conditions have been made possible by the use of diazonium salts that allow Heck couplings at moderate temperature (40 °C) under ligand-free conditions.     

Free-radical-5-exo-trig cyclization of chiral 3-silylhepta-1,6-dienes: concise approach to the A-B-C ring core of hexacyclinic acid

[Chemical reaction: See text] Free-radical-mediated 5-exo-trig cyclization of hepta-1,6-dienes 6a-c incorporating an allylsilane moiety was shown to provide at low temperature exclusively the trans-cis cyclopentanes 7a-c in good yield. In contrast, the same reaction with the alkyl analogue 9a led to the formation of all four possible stereoisomers. Interestingly, extension of this sequence of radical processes to alkoxy analogues 12-14 provided the complementary cis-cis stereoisomers with modest to excellent stereoselectivity. It is noteworthy that under such conditions allylsilanes were found to be much more reactive than their alkyl and alkoxy analogues. Beckwith-Houk-type models were proposed that rationalize the stereochemical course of these 5-exo-trig cyclizations. Finally, an illustration of the value of this methodology was proposed with the synthesis of the A-B-C tricyclic unit of polyketide hexacyclinic acid 3a.     

Practical and efficient Suzuki-Miyaura cross-coupling of 2-iodocycloenones with arylboronic acids catalyzed by recyclable Pd(0)/C

The first Suzuki-Miyaura cross-coupling of 2-iodocycloenones with arylboronic acids catalyzed by 10% Pd(0)/C is described as an interesting alternative to classical homogeneous conditions. Most of the substrate reacted under mild condition at 25 degrees C under air in aqueous DME. The conditions described tolerate a wide range of iodoenones and boronic acids. Notably, the procedure features inexpensive reagents and solvents with low toxicity rendering the method environmentally benign. Additionally 10% Pd(0)/C could be recovered and efficiently reused at least five times without significant alteration of the yields of the cross-coupled product.