conclusions the high prevalence of oxa β-lactamase and high genetic diversity of p. aeruginosa indicated that the resistance of p. aeruginosa might be expanding in our studied hospitals. background pseudomonas aeruginosa is main bacterial pathogen accountable for nosocomial infections. furthermore, it could potentially become resistant to β-lactams, aminoglycosides and fluoroquinolones antibiot...

The title compound, C(18)H(22)O(6), was obtained by the domino oxa-Michael-aldol (DOMA) reaction and has the cyclo-hexa-none ring in a chair conformation with intra-annular torsion angles in the range 49.9 (2)-58.9 (2)°. The two eth-oxy-carbonyl substituents on the cyclo-hexa-none ring adopt a syn configurations. In the crystal, the mol-ecules self-assemble through duplex inter-molecular hy-dro...

An unprecedented enantioselective synthesis of 3-substituted benzoxaboroles has been developed. An in situ generated ortho-boronic acid containing chalcone provides the chiral benzoxaboroles via an asymmetric oxa-Michael addition of hydroxyl group attached to the boronic acid triggered by the cinchona alkaloid based chiral amino-squaramide catalysts. In general, good yields with good to excelle...

An unprecedented domino synthesis of tetrahydrobenzofuran-4-ones is described implicating chemoselective alkylation of various 1,3-cyclohexanediones with bromocrotonate or crotonitrile followed by oxa-Michael cyclization. Further transformations of this core to reach molecular diversity are also presented.

Katsumadain A, a naturally occurring influenza virus neuraminidase (NA) inhibitor, was synthesized by using a bioinspired, organocatalytic enantioselective 1,4-conjugate addition of styryl-2-pyranone with cinnamaldehyde, followed by a tandem Horner-Wadsworth-Emmons/oxa Michael addition.

A concise 8-step synthetic route toward ent-heliespirones A & C is described. This synthetic strategy features a highly diastereoselective palladium-catalyzed Michael addition to form 3,5-trans lactone and a final biomimetic intramolecular oxa-spirocyclization.

An efficient cyclization of 2’-hydroxychalcone to flavanone using calcium chloride as a catalyst was developed. The scope of the reaction was studied with substituted 2’-hydroxychalcone and these chalcones was converted into corresponding flavanone in good yield. The merits of this method are inexpensive and easily available catalyst, easy workup procedure, avoid use of toxic solvent