7-alkylidenecephalosporin esters as inhibitors of human leukocyte elastase

Insights into the anticancer activity of chiral alkylidene-β-lactams and alkylidene-γ-lactams: Synthesis and biological investigation

Chiral alkylidene-β-lactams and alkylidene-γ-lactams were synthesized and screened for their in vitro activity against four human cancer cell lines (melanoma, esophageal, lung and fibrosarcoma carcinoma). Alkylidene-β-lactams were synthesized via Wittig reaction of diverse phosphorus ylides with benzhydryl 6-oxopenicillanate, derived from 6-aminopenicillanic acid. Moreover, novel chiral alkylidene-γ-lactams were synthesized through a multistep strategy starting from a chiral substrate (d-penicillamine). The in vitro assays allowed the identification of four compounds with IC₅₀ values < 10 μM for A375 cell line, and three compounds with IC₅₀ values < 10 μM for OE19 cell line. The effect of the most promising compounds on cell death mechanism, reactive oxygen species generation as well as the evaluation of their ability to act as MMP-9 inhibitors were studied. The reported results unveil the potential of alkylidene-β-lactams as anticancer agents.

Kinetics and stereochemistry of hydrolysis of an N-(phenylacetyl)-α-hydroxyglycine ester catalyzed by serine β-lactamases and DD-peptidases

The α-hydroxydepsipeptide 3-carboxyphenyl N-(phenylacetyl)-α-hydroxyglycinate (5) is a quite effective substrate of serine β-lactamases and low molecular mass DD-peptidases. The class C P99 and ampC β-lactamases catalyze the hydrolysis of both enantiomers of 5, although they show a strong preference for one of them. The class A TEM-2 and class D OXA-1 β-lactamases and the Streptomyces R61 and Actinomadura R39 DD-peptidases catalyze hydrolysis of only one enantiomer of at any significant rate. Experiments show that all of the above enzymes strongly prefer the same enantiomer, a surprising result since β-lactamases usually prefer L(S) enantiomers and DD-peptidases D(R). Product analysis, employing peptidylglycine α-amidating lyase, showed that the preferred enantiomer is D(R). Thus, it is the β-lactamases that have switched preference rather than the DD-peptidases. Molecular modeling of the P99 β-lactamase active site suggests that the α-hydroxyl 5 of may interact with conserved Asn and Lys residues. Both α-hydroxy and α-amido substituents on a glycine ester substrate can therefore enhance its productive interaction with the β-lactamase active site, although their effects are not additive; this may also be true for inhibitors.

Palladium-Catalyzed Intramolecular Selenocarbamoylation of Alkynes with Carbamoselenoates: Formation of α-Alkylidene-β-lactam Framework

Pd-catalyzed intramolecular selenocarbamoylation of alkynes leading to alpha-alkylidene-beta-lactams was developed. This reaction can be applied to thiocarbamoylation and to the synthesis of delta- and epsilon-lactams and a cyclobutanone.

Stereocontrolled synthesis of anticancer β-lactams via the Staudinger reaction

Stereocontrolled synthesis of novel beta-lactams using polyaromatic imines following the Staudinger reaction has been accomplished. The effects of domestic microwave irradiation on this type of reaction have been investigated. Formation of trans-beta-lactams has been explained through isomerization of the enolates formed during the reaction of acid chloride (equivalent) with imines in the presence of triethylamine. A donor-acceptor complex pathway is believed to be involved in the formation of cis-beta-lactams. The effect of a peri hydrogen has been found to be significant in controlling the stereochemistry of the resulting beta-lactams. SAR has identified beta-lactams with anticancer activity. The presence of an acetoxy group has proven obligatory for their anticancer activity.

Design, synthesis and biological evaluation of novel bicyclic β-lactams as potential antimalarials

A series of bicyclic N-substituted and unsubstituted beta-lactams were synthesized and evaluated as targeted potential antimalarials. The compounds MNR4 and MNR5 were found to have highest potency against Plasmodium falciparum in vitro.

Studies on Stereoselective [2+2] Cycloadditions between N,N-Dialkylhydrazones and Ketenes

Staudinger-like cycloadditions between chiral, non-racemic N,N-dialkylhydrazones 1 and functionalized ketenes constitute an efficient methodology for the stereoselective construction of the beta-lactam ring. The potential for fine tuning of the dialkylamino auxiliary structure, the availability of a high-yielding deprotection method for the release of the free azetidinones, and the high thermal and chemical stability of hydrazones as N-dialkylamino imines are highlighted as the key elements for the success of the strategy. This last aspect is of particular importance concerning generality: even hydrazones from easily enolizable aldehydes or from formaldehyde reacted to afford the corresponding cycloadducts with high chemical and stereochemical yields. The syntheses of the beta-amino-alpha-hydroxyacids (2R,3S)-phenylisoserine (42) and (2R,3S)-norstatin (45) were accomplished as illustrative examples of the synthetic utility of this procedure. A model system for the cycloaddition of g series auxiliaries was studied by ab initio computational methods. The collected results support a two-step mechanism through zwitterionic intermediates, and explain the observed absolute and relative stereochemistry in terms of the preferred outward cycloaddition to the Re face of the hydrazone.

Synthesis of anticancer β-lactams: mechanism of action

Synthesis of the trans 1-N-chrysenyl and 1-N-phenanthrenyl 3-acetoxy-4-phenyl-2-azetidinones has been achieved. Microwave-assisted reaction has proved useful in the synthesis of these compounds. Cell growth inhibition study has indicated selective anticancer activity against two leukemia and colon carcinoma cell lines. A mechanistic correlation of their anticancer activity has been described. Striking G2 blockade that is clearly distinct in cell cycle analysis and demonstrated only in sensitive cell lines has been observed. They do not induce apoptosis in sensitive or resistant lines. They also do not inhibit topoisomerases. Ames test has shown they are nonmutagenic.

Stereoselective synthesis of beta-lactams with polyaromatic imines: entry to new and novel anticancer agents

We present herein stereoselective synthesis of novel beta-lactams using polyaromatic imines following the Staudinger reaction. Consistent mechanisms for these results have been advanced. As a measure of cytotoxicity, some of these compounds have been assayed against nine human cancer cell lines. Structure-activity study has revealed that 1-N-chrysenyl and 1-N-phenanthrenyl 3-acetoxy-4-aryl-2-azetidinones have potent anticancer activity. The presence of the acetoxy group at C(3) of the beta-lactams has proven to be obligatory for their anticancer activity.

Synthesis of ferrocene-substituted 2-azetidinones

The photochemical reaction of alkoxychromium(0)carbene complexes and ferrocene mono- and disubstituted imines formed 2-azetidinones having one or two ferrocene moieties in good yields. Yields decrease when the carbene moiety bears an aminoferrocene moiety attached to the carbene carbon, while complex 9 having the ferrocene directly bonded to the carbene carbon was totally inert in these reactions. Access to beta-lactams with the ferrocene tethered to the C3 position through a methylene group was gained using the lithium enolate derived from ethyl 3-ferrocenylpropanoate. The reaction of this enolate produced two unexpected processes. Thus, 2-azetidinone 15 having an hydroxyl group at the C3 position was obtained together with the expected beta-lactam 14, by reaction of the lithium enolate of ethyl 3-ferrocenylpropenoate and imine 1. Additionally, unsaturated amide 17 was obtained by base-promoted Hoffmann-like breakage of the beta-lactam ring formed in the reaction of the same enolate and imine 2. Oxidation of the anion at the C3 of the 2-azetidinone ring on compound 14, as well as the sterically driven ring-breakage of the C3 anion derived from the nonisolated 2-azetidinone 18, should be responsible for this behavior.

Synthesis and human leukocyte elastase inhibitory evaluation of phosphate triesters and acyl phosphates of penam sulfides and sulfones

The synthesis of 6,6-dibromo-3alpha-(diphenylphosphate)oxymethyl-2,2-dimethyl penam sulfone (3a), 6alpha-chloro-3alpha-(diphenylphosphate)oxymethyl-2,2-dimethyl penam sulfone (3b), benzyl 6alpha-(diphenyl-phosphate)oxypenicillanate sulfone (4) and 6,6-dibromo-3alpha-(methylphosphate)carbonyl-2,2-dimethylpenam sulfone (12) are reported. When tested as inhibitors of human leukocyte elastase, the compound 4 proved to be the most active.

The synthesis and evaluation of 3-substituted-7-(alkylidene)cephalosporin sulfones as beta-lactamase inhibitors

A series of 3-substituted-7-(alkylidene)cephaloporin sulfones were prepared and evaluated as inhibitors of representative class A and class C serine beta-lactamase. Appropriate substituents resulted in a 1000-fold improvement in the inhibition of the class A enzymes and a simultaneous 20-fold improvement in the inhibition of class C. These new compounds have achieved the goal of creating broad scale inhibitors in the cephalosporin series.

2-(diethylamino)thieno1,3ŏxazin-4-ones as stable inhibitors of human leukocyte elastase

A series of 2-(diethylamino)thieno1,3ŏxazin-4-ones was synthesized and evaluated in vitro for inhibitory activity toward human leukocyte elastase (HLE). The Gewald thiophene synthesis was utilized to obtain several ethyl 2-aminothiophene-3-carboxylates. These precursors were subjected to a five-step route to obtain thieno2,3-d1,3ŏxazin-4-ones bearing various substituents at positions 5 and 6. Both thieno2,3-d and thieno3,2-d fused oxazin-4-ones possess extraordinary chemical stability, which was expressed as rate constants of the alkaline hydrolysis. The kinetic parameters of the HLE inhibition were determined. The most potent compound, 2-(diethylamino)-4H-1benzothieno2,3-d1,3ŏxazin-4-one, exhibited a K(i) value of 5.8 nM. 2-(Diethylamino)thieno1, 3ŏxazin-4-ones act as acyl-enzyme inhibitors of HLE, similar to the inhibition of serine proteases by 4H-3,1-benzoxazin-4-ones. The isosteric benzene-thiophene replacement accounts for an enhanced stability of the acyl-enzyme intermediates.

A rapid method to identify exo-protease inhibitors

A new approach to the evaluation of exo-protease inhibitor candidates is presented. The application of new water-soluble substrates that release organic-soluble fluorescent groups upon proteolytic cleavage allows amplification of the assay signal via concentration of the cleavage product. A combinatorial library of disubstituted xanthenes designed to resemble a known inhibitor was screened and a new HLE inhibitor (Ki = 79 microM) was identified.

Synthesis and in vitro and in vivo evaluation of the 2-(6'methoxy-3',4'-dihydro-1'-naphtyl)-4H-3,1-benzoxazin-4- one as a new potent substrate inhibitor of human leukocyte elastase

The title 2-vinyl-4H-3,1-benzoxazin-4-one has been synthesised and tested for inhibitory activity against human leukocyte elastase. The compound has shown activity both in vitro towards human sputum elastase and in vivo in an hemorrhagic assay.