Enantioselective direct Michael additions of ketones using (S)-1-(2-pyrrolidinylmethyl)-pyrrolidine as a catalyst are described. Michael adducts with up to 91% e.e. were obtained by the reaction of alkylidene malonates with simple unactivated ketones under mild reaction conditions. © 2001 Elsevier Science Ltd. All rights reserved. An increasing demand for optically active compounds has stimulat...

The gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation reaction offers a simple and efficient method for the synthesis of pyrrolidine derivatives in moderate to excellent product yields and with moderate to good diastereoselectivities. The reaction conditions and the substrate scope of this reaction are examined, and a possible mechanism invol...

A new and efficient method has been developed for the synthesis of 4-aryl-7-benzylidene-1,3,4,5,6,7-hexahydro-2H-cyclopenta[d]pyrimidin-2-ones through Biginelli-like reaction of cyclopentanone, with urea/thiourea and aromatic aldehyde employing p-dodecylbenzenesulfonic acid (DBSA) as a recyclable catalyst under solvent-free condition. The recovered catalyst was recycled for further runs. The pr...

A chromosomally encoded class D beta-lactamase, OXA-114, was characterized from Achromobacter xylosoxidans strain CIP69598. beta-Lactamase OXA-114 shared 56% amino acid identity with the naturally occurring class D beta-lactamase of Burkholderia cenocepacia and 42% identity with the acquired oxacillinases OXA-9 and OXA-18. OXA-114 has a narrow-spectrum hydrolysis profile, although it includes i...

A chromosomally encoded oxacillinase, OXA-69, was characterized from Acinetobacter baumannii AYE. beta-Lactamase OXA-69 shared 97% amino acid identity with the recently described OXA-51 enzyme of A. baumannii and 62 and 56% amino acid identity with the carbapenem-hydrolyzing oxacillinases OXA-24 and OXA-23, respectively. Biochemical characterization of the purified OXA-69 revealed a narrow-spec...

An approach to the intramolecular Diels-Alder reaction has led to a cascade synthesis of complex carbocycles composed of three fused rings and up to five stereocenters with complete stereocontrol. Computational analysis reveals that the reaction proceeds by a Michael/Michael/cyclopropanation/epimerization cascade in which size and coordination of the counterion is key.

The asymmetric and catalytic Michael reaction between α-nitroesters and nitroalkenes has been studied in the presence of two bifunctional catalysts both containing the same absolute chirality at the carbon backbone. The reaction performed in similar conditions allows us to control the syn or anti selectivity of the Michael adduct obtaining good yields and high enantiocontrol in all cases.

A useful Michael addition reaction using nitroalkanes as the nucleophile and 4-oxo-enoates as the Michael acceptor has been disclosed, and the reaction allows expedient access to functionalized chiral gamma-keto esters in high yields and excellent enantioselectivities (up to 98% ee), with a low catalyst loading.

Abstract The selective α‐deuteration of α,β‐unsaturated nitriles using the strong base t BuOK or a metal‐ligand cooperative Ru pincer catalyst is described. With D 2 O as deuterium source and glyme solvent at 70 °C, an efficient for deuteration α‐C( sp ) position cinnamonitriles, providing access to broad range deuterated derivatives in good excellent yields with very high levels incorporation....

Eighty-two carbapenem-resistant isolates of Acinetobacter baumannii from a single hospital in Bilbao were typed into two major clusters and several subclusters. Disk synergy tests and PCR indicated the production of a zinc-independent OXA-class carbapenemase. Sequencing identified this enzyme, OXA-40, as a variant of the OXA-24-OXA-25-OXA-26 cluster.