In vitro evaluation of the antielastase activity of polycyclic β-lactams

Enantioselective Synthesis of Aza-Flavanones with an All-Carbon Quaternary Stereocenter via NHC-Catalyzed Intramolecular Annulation

An enantioselective synthesis of functionalized aza-flavanone derivatives using the N-heterocyclic carbene-catalyzed intramolecular Stetter reaction of sulphoamido benzaldehydes has been reported. This procedure presents the first original approach for synthesizing chiral functionalized flavonoids at the 3-position, containing an all-carbon quaternary stereogenic center. This advancement significantly enriches the chemical toolbox for the preparation of complex nitrogen-containing compounds and opens up new avenues for further research and development in synthetic organic chemistry.

A concise and versatile route to tetrahydro-1-benzazepines carrying [a]-fused heterocyclic units: synthetic sequence and spectroscopic characterization, and the molecular and supramolecular structures of one intermediate and two products

A concise, efficient and versatile route from simple starting materials to tricyclic tetrahydro-1-benzazepines carrying [a]-fused heterocyclic units is reported. Thus, the easily accessible methyl 2-[(2-allyl-4-chlorophenyl)amino]acetate, (I), was converted, via (2RS,4SR)-7-chloro-2,3,4,5-tetrahydro-1,4-epoxy-1-benzo[b]azepine-2-carboxylate, (II), to the key intermediate methyl (2RS,4SR)-7-chloro-4-hydroxy-2,3,4,5-tetrahydro-1H-benzo[b]azepine-2-carboxylate, (III). Chloroacetylation of (III) provided the two regioisomers methyl (2RS,4SR)-7-chloro-1-(2-chloroacetyl)-4-hydroxy-2,3,4,5-tetrahydro-1H-benzo[b]azepine-2-carboxylate, (IVa), and methyl (2RS,4SR)-7-chloro-4-(2-chloroacetoxy)-2,3,4,5-tetrahydro-1H-benzo[b]azepine-2-carboxylate, C₁₄H₁₅Cl₂NO₄, (IVb), as the major and minor products, respectively, and further reaction of (IVa) with aminoethanol gave the tricyclic target compound (4aRS,6SR)-9-chloro-6-hydroxy-3-(2-hydroxyethyl)-2,3,4a,5,6,7-hexahydrobenzo[f]pyrazino[1,2-a]azepine-1,4-dione, C₁₅H₁₇ClN₂O₄, (V). Reaction of ester (III) with hydrazine hydrate gave the corresponding carbohydrazide (VI), which, with trimethoxymethane, gave a second tricyclic target product, (4aRS,6SR)-9-chloro-6-hydroxy-4a,5,6,7-tetrahydrobenzo[f][1,2,4]triazino[4,5-a]azepin-4(3H)-one, C₁₂H₁₂ClN₃O₂, (VII). Full spectroscopic characterization (IR, ¹H and ¹³C NMR, and mass spectrometry) is reported for each of compounds (I)-(III), (IVa), (IVb) and (V)-(VII), along with the molecular and supramolecular structures of (IVb), (V) and (VII). In each of (IVb), (V) and (VII), the azepine ring adopts a chair conformation and the six-membered heterocyclic rings in (V) and (VII) adopt approximate boat forms. The molecules in (IVb), (V) and (VII) are linked, in each case, into complex hydrogen-bonded sheets, but these sheets all contain a different range of hydrogen-bond types: N-H...O, C-H...O, C-H...N and C-H...π(arene) in (IVb), multiple C-H...O hydrogen bonds in (V), and N-H...N, O-H...O, C-H...N, C-H...O and C-H...π(arene) in (VII).

Diastereoselective synthesis of 3-acetoxy-4-(3-aryloxiran-2-yl)azetidin-2-ones and their transformation into 3,4-oxolane-fused bicyclic β-lactams

cis-3-Acetoxy-4-(3-aryloxiran-2-yl)azetidin-2-ones were prepared through a Staudinger [2+2]-cyclocondensation between acetoxyketene and the appropriate epoxyimines in a highly diastereoselective way. Subsequent potassium carbonate-mediated acetate hydrolysis, followed by intramolecular ring closure through epoxide ring opening, afforded stereodefined 3-aryl-4-hydroxy-2-oxa-6-azabicyclo[3.2.0]heptan-7-ones as a novel class of C-fused bicyclic β-lactams. Selective benzylic oxidation of bicyclic N-(4-methoxybenzyl)-β-lactams with potassium persulfate and potassium dihydrogen phosphate provided the corresponding N-aroyl derivatives as interesting leads for further β-lactamase inhibitor development.