Search Results (12)

Non-cephem drugs with 1,3-thiazine-derived rings are very rare, although a number of bioactive 1,3-thiazine derivatives are known. Similarly, 1,4-thiazepine-derived drugs are rare, but many 1,4-thiazepine derivatives show interesting biological activities. Therefore, our aim was the synthesis of such N,S-heterocycles using a versatile and short (1–3 steps) literature method. First, a three-component reaction of a cycloalkene, a thioamide, and an aldehyde provided 5,6-dihydro-4H-1,3-thiazines. Afterwards, Staudinger ketene–imine cycloaddition with chloroketene resulted in β-lactam-fused 1,3-thiazinanes. Finally, treatment with sodium methoxide induced ring expansion, yielding 4,5,6,7-tetrahydro-1,4-thiazepines. This synthetic pathway generates 3–5 new chiral centers with the help of pericyclic reactions, and almost every cycloaddition proceeded in a diastereoselective manner. Two-dimensional NOESY as well as single-crystal X-ray diffraction enabled unequivocal determination of the stereochemistry of all synthesized compounds. Full article

β-Lactams are key scaffolds in synthetic and medicinal chemistry, valued for both therapeutic relevance and synthetic utility. Classical ketene-imine [2+2] cycloadditions often employ stabilized aryl ketenes, which display reduced reactivity and modest stereoselective. Disruption of π-conjugation in N-pyrrolylketene has been shown to enhance electrophilicity and direct stereochemical outcomes in reactions with aromatic imines. The ketene, generated in situ from N-pyrrolylpropanoic acid, undergoes cycloaddition under mild conditions to give β-lactams with a strong preference for the trans isomer. Frontier molecular orbital analysis and mechanistic interpretation suggest a polar asynchronous pathway, highlighting ketene destabilization as a practical strategy for stereoselective β-lactam synthesis. Full article

The [3+2] cycloaddition chemistry of (2S)-5-methylene-2-t-butyl-1,3-dioxolan-4-one, derived from lactic acid, has been examined, and spiro adducts have been obtained with benzonitrile oxide, acetonitrile oxide, diazomethane and diphenyldiazomethane. The structure and absolute stereochemistry of the benzonitrile oxide adduct has been confirmed by X-ray diffraction, and all the adducts have been fully characterised by ¹H and ¹³C NMR. Attempted cycloaddition with a nitrile sulfide, a nitrile imine and azides failed. Pyrolysis results in a range of novel gas-phase reactions, with the nitrile oxide adducts giving pivalaldehyde, CO₂, the nitrile and ketene, the diazomethane adduct losing only N₂ to give a cyclopropane-fused dioxolanone, and the diphenylcyclopropane derived from diphenyldiazomethane giving mainly benzophenone in a sequence involving the loss of pivalaldehyde and methyleneketene. Full article

The present review is a comprehensive update of the synthesis of monocyclic β-lactams via cycloaddition reactions. According to the IUPAC definition of cycloaddition, both elementary and stepwise processes (formal cycloadditions) have been considered. The years 2019–2022 are covered by the cited literature. The focus of the review is on synthetic aspects with emphasis on the structural scope, reaction conditions, mechanistic aspects, and selectivity results. Selected significant data related to biological activities and synthetic applications are also highlighted. Full article

In this work, we present the first synthesis of dispirooxindole-β-lactams employing optimized methodology of one-pot Staudinger ketene-imine cycloaddition with N-aryl-2-oxo-pyrrolidine-3-carboxylic acids as the ketene source. Spiroconjugation of indoline-2-one with β-lactams ring is considered to be able to provide stabilization and wide scope of functionalization to resulting scaffolds. The dispipooxindoles obtained demonstrated medium cytotoxicity in the MTT test on A549, MCF7, HEK293, and VA13 cell lines, and one of the compounds demonstrated antibacterial activity against E. coli strain LPTD. Full article

A series of ten novel derivatives of 4-(benzyloxy)-N-(3-chloro-2-(substituted phenyl)-4-oxoazetidin-1-yl) benzamide 6a–j were synthesized in good yield from the key compound 4-(benzyloxy)-N′-(substituted benzylidene) benzo hydrazide, called Schiff ’s bases 5a–j, by Staudinger reaction ([2 + 2] ketene-imine cycloaddition reaction) with chloro acetyl chloride in the presence of catalyst tri ethylamine and solvent dimethyl formamide (DMF), by using ultra-sonication as one of the green chemistry tools. All the synthesised compounds were evaluated for in vitro anti-tubercular activity against Mycobacterium tuberculosis (MTB) and most of them showed promising activity with an IC₅₀ value of less than 1 µg/mL. To establish the safety, all the synthesized compounds were further tested for cytotoxicity against the human cancer cell line HeLa and all 6a–j compounds were found to be non-cytotoxic in nature. The molecular docking study was carried out with essential enzyme InhA (FabI/ENR) of Mycobacterium responsible for cell wall synthesis which suggests that 6a and 6e are the most active derivatives of the series. The theoretical evaluation of cell permeability based on Lipinski’s rule of five has helped to rationalize the biological results and hence the synthesized azetidinone derivatives 6a–j were also analyzed for physicochemical evaluation that is, absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties and the results showed that all the derivatives could comply with essential features required for a potential lead in the anti-tubercular drug discovery process. Full article

The ortho-nitro effect was discovered in sulfa-Staudinger cycloadditions of ethoxycarbonylsulfene with linear imines. When an ortho-nitro group is present at the C-aryl substituents of linear imines, the sulfa-Staudinger cycloadditions deliver cis-β-sultams in considerable amounts, together with the predominant trans-β-sultams. In other cases, the above sulfa-Staudinger cycloadditions give rise to trans-β-sultams exclusively. Further mechanistic rationalization discloses that the ortho-nitro effect is attributed to its strong electron-withdrawing inductive effect. Similarly, the ortho-nitro effect also exists in Staudinger cycloadditions of ethoxycarbonyl ketene with the imines. The current research provides further insights into the diastereoselective control in sulfa-Staudinger and Staudinger cycloadditions. Full article

Some new mono-and bis-polycyclic aromatic spiro-β-lactams and bis-non spiro-polycyclic aromatic β-lactams have been synthesized from imines derived from anthracene-9-carbaldehyde, 2-naphtaldehyde and a ketene derived from 9H-xanthene-9-carboxylic acid and phenoxyacetic acid by a [2+2] cycloaddition reaction. The cycloadducts were characterized by spectral data, including ¹H-NMR, ¹³C-NMR, IR and elemental analyses. The configurations of some of these mono-spiro-β-lactams were established by X-ray crystal analysis. Full article

It is shown that the N-(p-ethoxyphenyl) group on β-lactams can be oxidatively removed by ceric ammonium nitrate in good yield. Fourteen new N-(p-ethoxyphenyl)-2-azetidinones 8a-n were synthesized through standard [2+2] ketene-imine cycloadditions (Staudinger reaction). Treatment of these compounds with ceric ammonium nitrate yielded the N-dearylated 2-azetidinones 9a-n in good to excellent yields. The effects of solvent, molar equiv of CAN and different temperatures have been investigated and optimum conditions were established. Full article

Synthesis of a new monocyclic β-lactam containing a sugar moiety at its N1 position via [2+2] cycloaddition reaction of ketene and imine is described. Reaction of achiral phenoxy ketene with chiral aldimine derived from chiral 2, 3, 4, 6-tetra-O-acetyl-β-D-galactopyranosylamine and 2-hydroxy-3-methoxy benzaldehyde resulted in the formation of 2 as a single diastereomer. Then its physical characterization has been determined at the AM1 level of theory. Full article

New cis monocyclic β-lactams were synthesized by [2+2] Staudinger cycloaddition reactions of the imine (3,4-dimethoxybenzylidene)-(4-methoxyphenyl)- amine and ketenes derived from different acyl chlorides and Et3N. These monocyclic β-lactams were then cleaved by ceric ammonium nitrate (CAN) to give NH-monocyclic β-lactams, which in turn were converted to N-sulfonyl monocyclic β-lactams by treatment with four different sulfonyl chlorides in the presence of Et3N and 4,4-dimethyl- aminopyridine (DMAP). Full article