Seven-membered Lactam Research Articles

Design and synthesis of 7-membered lactam fused hydroxypyridinones as potent metal binding pharmacophores (MBPs) for inhibiting influenza virus PAN endonuclease

Since influenza virus RNA polymerase subunit PAN is a dinuclear Mn2+ dependent endonuclease, metal-binding pharmacophores (MBPs) with Mn2+ coordination has been elucidated as a promising strategy to develop PAN inhibitors for influenza treatment. However, few attentions have been paid to the relationship between the optimal arrangement of the donor atoms in MBPs and anti-influenza A virus (IAV) efficacy. Given that, the privileged hydroxypyridinones fusing a seven-membered lactam ring with diverse side chains, chiral centers or cyclic systems were designed and synthesized. A structure-activity relationship study resulted in a hit compound 16l (IC50 = 2.868 ± 0.063 μM against IAV polymerase), the seven-membered lactam ring of which was fused a pyrrolidine ring. Further optimization of the hydrophobic binding groups on 16l afforded a lead compound (R, S)-16s, which exhibited a 64-fold more potent inhibitory activity (IC50 = 0.045 ± 0.002 μM) toward IAV polymerase. Moreover, (R, S)-16s demonstrated a potent anti-IAV efficacy (EC50 = 0.134 ± 0.093 μM) and weak cytotoxicity (CC50 = 15.35 μM), indicating the high selectivity of (R, S)-16s. Although the lead compound (R, S)-16s exhibited a little weaker activity than baloxavir, these findings illustrated the utility of a metal coordination-based strategy in generating novel MBPs with potent anti-influenza activity.

Discovery and Optimization of Seven-Membered Lactam-Based Compounds to Phenocopy the Inhibition of the Aurora Kinase B.

We used mechanism-informed phenotypic screening to identify and optimize compounds that phenocopy the genetic depletion of the mitotic aurora kinase B (AURKB) kinase. After assaying nine aryl fused seven-membered lactam compounds, we identified a hit compound 6a that was subsequently optimized to five lead compounds with low nanomolar activity, represented by the lead compound 6v (19 nM). With excellent drug-like properties, these compounds reproduced the loss of function in phenotypes of AURKB and exhibited potent cytotoxic activities in various cancer cell lines. Collectively, these data support that seven-membered lactam-based analogs might be valuable for further development as a new type of antimitotic agents for the treatment of cancer.

Remote Stereoelectronic Effects in Pyrrolidone- and Caprolactam-Substituted Phenols: Discrepancies in Antioxidant Properties Evaluated by Electrochemical Oxidation and H-Atom Transfer Reactivity.

New antioxidants are commonly evaluated via two main approaches, i.e., the ability to donate an electron and the ability to intercept free radicals. We compared these approaches by evaluating the properties of 11 compounds containing both antioxidant moieties (mono- and polyphenols) and auxiliary pharmacophores (pyrrolidone and caprolactam). Several common antioxidants, such as butylated hydroxytoluene (BHT), 2,3,5-trimethylphenol (TMP), quercetin, and dihydroquercetin, were added for comparison. The antioxidant properties of these compounds were determined by their rates of reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and their oxidation potentials from cyclic voltammetry. Although these methods test different chemical properties, their results correlate reasonably well. However, several exceptions exist where the two methods give opposite predictions! One of them is the different behavior of mono- and polyphenols: polyphenols can react with DPPH more than an order of magnitude faster than monophenols of a similar oxidation potential. The second exception stems from the size of a "bystander" lactam ring at the benzylic position. Although the phenols with a seven-membered lactam ring are harder to oxidize, the sterically nonhindered compounds react with DPPH about 2× faster than the analogous five-membered lactams. The limitations of computational methods, especially those based on a single parameter, are also evaluated and discussed.

A novel rosamine-based fluorescent probe for the rapid and selective detection of cysteine in BSA, water, milk, cabbage, radish, apple, and pear

A novel fluorescent probe (RA), based on the rosamine skeleton bearing acrylate group, has been reasonably designed and prepared, which employed an addition-cyclization-elimination sequence reaction mechanism to detect cysteine. RA displayed rapid response to cysteine within 1.5 min, and exhibited satisfactory selectivity for cysteine over H2S, glutathione (Glu), and homocysteine (Hcy), due to the formation of seven-membered lactam favored kinetically. Fluorescence ratio was utilized to detect cysteine from 6.0 to 20.0 μM with a detection limit of 0.29 μM. More, RA was used to monitor cysteine in BSA, water, milk, milk powder, cabbage, radish, apple, and pear.

Enantioselective Total Synthesis and Absolute Configuration Assignment of (+)-Tronocarpine Enabled by an Asymmetric Michael/Aldol Reaction.

We present the first asymmetric total synthesis and absolute configuration determination of (+)-tronocarpine. The [6.5.7.6.6] pentacyclic core was constructed at an early stage by using a sequential cyclization strategy through a newly developed catalytic asymmetric Michael/aldol cascade to build the aza[3.3.1]-bridged cycle and a tandem reduction/hemiamidation procedure to assemble the seven-membered lactam. The side-chain functionalities were incorporated at a late stage by several appropriately orchestrated manipulations under mild conditions. The synthesis of enantiomerically pure (+)-tronocarpine was achieved through a 20-step longest linear sequence from tryptamine.

Seco-Dendrobine-Type Alkaloids and Bioactive Phenolics from Dendrobium findlayanum.

Investigation of the 95% EtOH extract of stems of Dendrobium findlayanum afforded four new seco-dendrobines, findlayines A-D (1-4); two known dendrobines, dendrobine (5) and 2-hydroxydendrobine (6); and four new phenolic compounds, dendrofindlaphenols A-C (7, 9, and 10) and 6″-de-O-methyldendrofindlaphenol A (8). Compounds 1 and 2 are the first seco-dendrobines possessing a seven-membered lactam moiety, with 3 and 4 derived from the oxidative cleavage of the C-2-C-3 bond of dendrobine. The structures were established using spectroscopic methods and by comparison with literature data. The absolute configurations of 1-4 were confirmed via single-crystal X-ray diffraction data. Cytotoxic activity assays against HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines revealed IC50 values ranging from 2.3 to 5.3 μM for compound 7, from 19.4 to 34.4 μM for 8, and from 49.4 to 96.8 μg/mL for the EtOAc extract. An assay of the inhibition of NO production with RAW 264.7 cells indicated that 8 had an IC50 value of 21.4 μM, and the EtOAc extract, 10.5 μg/mL. The EtOAc extract possessed DPPH radical scavenging activity of 69.93% at 100 μg/mL.

Seven-Membered Lactam Derivatives of Podophyllotoxins as New Pesticidal Agents

As a continuation of our efforts to discover and develop natural-product-based insecticidal agents, three novel and unusual 7-membered lactam derivatives of podophyllotoxin were prepared by thionyl chloride-mediated ring-expanded Beckmann rearrangement. The steric configurations of 3a–c were unambiguously identified by X-ray crystallography. It demonstrated that the configuration of the picropodophyllotoxin C4-oximes could also be confirmed by the corresponding C-ring expansion products via Beckmann rearrangement. Moreover, it was obviously further testified that when picropodophyllones reacted with hydroxylamine hydrochloride, only E configuration of picropodophyllotoxin C4-oximes was selectively produced. Compounds 3b and 3c showed more potent pesticidal activity than toosendanin against oriental armyworm, Mythimna separata (Walker).

Semi-synthetic preparation, structural elucidation and pharmacological study of nitrogen-containing ecdysteroid analogs

Ecdysteroids are specific hydroxysteroids that exert a wide a range of biological functions in the flora and the fauna. Our group has recently described that less polar ecdysteroid derivatives can strongly sensitize various cancer cell lines to certain chemotherapeutics, which can be observed both in multi-drug resistant (MDR) and drug susceptible cancer cells [1 – 2]. Recent studies also revealed that oxime groups can increase the antitumor activity of certain steroid derivatives [3], but ecdysteroid oximes have previously not been studied from this point of view. In our current work, we aimed to synthesize C6 ecdysteroid oximes of 20-hydroxyecdysone 2,3;20,22-diacetonide, optimizing the previously available methods [4]. Rotational planar chromatographic, analytical and preparative RP-HPLC and centrifugal partition chromatographic methods were developed for the purification. The diacetonides of two 14,15-anhydro ecdysteroid oxime isomers (E/Z-oximes) were obtained, and Beckmann rearrangement of the new 14,15-anhydro E-oxime yielded another new derivative containing a seven-membered lactam B-ring [5]. The ecdysteroid oximes were tested for their activity against L5178 mouse T-cell lymphoma cells (non-MDR) and their sub-cell line transfected with pHa MDR1/A retrovirus overexpressing the human ABCB1 efflux pump (MDR cell line). Each oxime was found to be a promising modulator of resistance on the MDR cell line, and the E-oxime could also sensitize the non-MDR cells to doxorubicin. Our preliminary SAR study also revealed, that the antitumor activity of ecdysteroid diacetonides follow the ecdysteroid < Z-oxime < E-oxime order. Acknowledgement: Szeged Foundation for Cancer Research.

Regioselective alkylation of 1,3,4,5-tetrahydrobenzo[d]azepin-2-one and biological evaluation of the resulting alkylated products as potentially selective 5-HT₂c agonists.

The benzazepine ring system has offered interesting CNS-active medicinal agents. Taking this privileged structure as the basic scaffold, [Formula: see text] and/or [Formula: see text]-alkylated benzazepin-2-one derivatives and their reduced analogs have been prepared as potential [Formula: see text] receptor agonists. The selective alkylation at the [Formula: see text] and/or [Formula: see text] positions of this seven-membered lactam ring is here reported for the first time under different reaction conditions. The synthesized compounds were evaluated for their biological profile as potential [Formula: see text] agonists using a classic pharmacological approach. Three derivatives (15, 17, and 20) have shown promising [Formula: see text] agonistic activity which can be further optimized as anti-obesity agents for the treatment of male sexual dysfunction. Further, a homology model for [Formula: see text] receptor was generated using MODELLER, and ligand-receptor interactions for these potential molecules were studied.

マンニッヒ型反応による2,2-二置換インドリン-3-オン構築法の開発と天然物合成への展開

2,2-Disubstituted 1,2-dihydro-3H-indol-3-ones are useful synthetic intermediates for natural products. Therefore, its preparation in a concise manner is highly desirable. Recently, we reported a methodology for the preparation of 2,2-disubstituted 1,2-dihydro-3H-indol-3-ones through the successive oxidation of indoles and Mannich-type reaction of 2-hydroxy-1,2-dihydro-3H-indol-3-ones with various carbon nucleophiles. Using this method, we accomplished the total synthesis of (±)-hinckdentine A. The synthesis featured seven-membered lactam formation by Murahashi’s Ru catalyst and the selective tri-bromination of aromatic ring. Also, we performed the synthesis of isatisine A framework. In this research, we found an intriguing reaction in which nucleophiles are introduced at the C-2 position of 3H-indol-3-one via activation with TFAA. Towards the total synthesis of leuconoxine, ring construction steps featuring the N-acyliminium mediated intramolecular piperidine cyclization and the one-step pyrrolidone formation using Bestmann’s ylide are achieved successfully. Utilization of a chiral phosphoric acid catalyst (VAPOL PA), the asymmetric desymmetrization of prochiral diester produced highly-enantioenriched lactam in excellent yield. Using this strategy, we accomplished the asymmetric total synthesis of (−)-leuconoxine.

Lipase Catalyzed Regioselective Lactamization as a Key Step in the Synthesis of N-Boc (2R)-1,4-Oxazepane-2-Carboxylic Acid

A synthesis of N-Boc (2R)-1,4-oxazepane-2-carboxylic acid 1 has been developed in 39% yield over seven steps starting from methyl (2R)-glycidate 2. The key step was a lipase-catalyzed regioselective lactamization of amino diester 5 into seven-membered lactam 6. The transformation was performed using SpinChem rotating flow cell technology which simplified the work up and the recycling of the enzyme. Subsequent N-Boc protection followed by chemoselective borane reduction of the lactam moiety afforded 4-tert-butyl 2-methyl (2R)-1,4-oxazepane-2,4-dicarboxylate 8. Finally, hydrolysis mediated by LiBr/Et3N in wet acetonitrile yielded the title compound (2R)-4-(tert-butoxycarbonyl)-1,4-oxazepane-2-carboxylic acid 1.

N-(2-Oxo-2,3,4,5,6,7-hexahydro-1H-azepin-3-yl)cyclohexanecarboxamide

In the title compound, C13H22N2O2, both the six-membered ring and the seven-membered lactam ring adopt chair conformations. In the crystal, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds between inversion-related lactam rings into centrosymmetric dimers with an R 2 2(8) graph-set motif. Further N—H⋯O hydrogen bonds link the molecules into [100] chains.

The First Total Synthesis of Fuscain

The first total synthesis of the furanolactam fuscain is reported. The key step in the synthesis was the formation of seven-membered lactam by acylation of a furan ring using the mild Lewis acid CuSO4·5H2O.

3-Cyano-11-oxo-3,4-seco-12a-aza-C-homoolean-4(23)-en-28-oic acid methyl ester

The title compound, C31H48N2O3, is a Beckmann rearrangement product. The isopropenyl and meth­oxy­carbonyl groups have β-orientations, whereas the 2-cyano­ethyl group has an α-orientation. In the triterpenoid skeleton, the seven-membered lactam ring, as well as the three six-membered carbocyclic rings, have chair conformations. In the crystal, mol­ecules are linked via nonclassical C—H⋯O hydrogen bonds into layers parallel to the ab plane.

Quaternary α,α-2-Oxoazepane α-Amino Acids: Synthesis from Ornithine-Derived β-Lactams and Incorporation into Model Dipeptides

To explore further the chemistry of amino acid-derived β-lactams, their conversion to α,α-heterocyclic quaternary amino acid derivatives is investigated. The latter derivatives, containing 2-oxoazepane as the α,α-substituent, are synthesized by a simple Pd-C-catalyzed hydrogenolysis of Orn(Z)-derived 2-azetidinones. The rearrangement from four- to seven-membered lactam ring is driven by the key intramolecular opening of the 1-Boc-β-lactam, initiated by 7-exotrig ring closure from the NH(2) of the Orn side chain. The synthetic route is applied to the stereoselective preparation of enantiomerically pure 4-amino-3-methyl-2-oxoazepane-4-carboxylate derivatives, for which the structure and configuration is confirmed by X-ray diffraction. Molecular modeling and NMR experiments indicate that these quaternary amino acids are able to drive the adoption of β-turn secondary structures when incorporated in model dipeptide derivatives.

ChemInform Abstract: Tronocarpine, a Novel Pentacyclic Indole Incorporating a Seven-Membered Lactam Moiety.

Abstract A novel pentacyclic indole alkaloid, tronocarpine, incorporating a seven-membered lactam unit, was obtained from the stem-bark extract of Tabernaemontana corymbosa and its structure elucidated by spectral analysis.

Base-Sensitivity of Arginine Alpha-Ketoamide Inhibitors of Serine Proteases

Serine protease enzymes use a serine hydroxyl group to catalyze hydrolysis of polypeptides. They are important in immunity, blood clotting, digestion, and as therapeutic or diagnostic targets for cancer, diabetes, stroke, inflammatory diseases, and viral infections. Their inhibitors typically possess an electrophile that reacts with the nucleophilic hydroxyl group of the catalytic serine. The α-ketoamide is a valuable electrophile in inhibitor discovery as it permits synthetic elaboration to both sides, unlike other electrophiles. Here we show that an α-ketoamide is unstable above pH 7 when adjacent to the C-terminus of arginine – the guanidine side chain condenses with the α-ketoamide at the keto group rather than the amide carbonyl to form a six-membered hemiaminal rather than a seven-membered lactam.

2-(2-Chloropyrimidin-4-yl)-3,5,6,7,8,9-hexahydro-2H-1,2,4-triazolo[4,3-a]azepin-3-one

In the title compound, C11H12ClN5O, the triazolone and pyrimidine rings are almost coplanar [dihedral angle = 2.98 (14)°]. The total puckering amplitude QT of the seven-membered lactam ring is 0.706 (3) Å.

Base‐Induced Sequential Cyclization–Rearrangement of Enantioenriched 3‐Aminoalkanoates to Five‐ and Seven‐Membered Lactams

By treatment with tBuLi, linear 3-aminoalkanoates (4) were converted stereoselectively into five- and seven-membered lactams (trans-5 and cis-6). Initial cyclization to azetidin-2-one with subsequent aza-[1,2] and [2,3] rearrangement is the probable mechanistic pathway from 4 to 5 and 6. Although enantioenriched 4 was converted into nearly racemic 5 and 6, a linear 3-amino-2-methylalkanoate (17) with 90 % ee bearing chirality at the ester alpha-position afforded an all-cis seven-membered lactam (18) bearing three asymmetric centers with 85 % ee.

Molecular Building Kit of Fused-Proline-Derived Peptide Mimetics Allowing Specific Adjustment of the Dihedral Ψ Angle

Proline-derived peptide mimetics have become an area of paramount importance in peptide and protein chemistry. Since protein crystal structures frequently display Psi angles of 140-170 degrees for prolyl moieties, our intention was to design a completely novel series of 2,3-fused-proline-derived lactams covering this particular conformational space. Extending our recently described toolset of spirocyclic reverse-turn mimetics, we synthesized pyrrolidinyl-fused seven-, eight-, and nine-membered unsaturated lactam model peptides taking advantage of Grubbs' ring-closing metathesis. Investigating the seven-membered lactam 3a by means of IR and NMR spectroscopy and semiempirical molecular dynamics simulations, we could not observe a U-turn conformation; however, increasing the ring size to give eight- and nine-membered congeners revealed moderate and high type IotaIota beta-turn inducing properties. Interestingly, the conformational properties of our model systems depend on both the ring size of the fused dehydro-Freidinger lactam and the position of the endocyclic double bond. Superior reverse-turn inducing properties could be observed for the fused azacyclononenone 3e. According to diagnostic transanular NOEs, a discrete folding principle of the lactam ring strongly deviating from the regioisomeric lactams 3c,f explains the conformational behavior. Hence, we were able to establish a molecular building kit that allows adjustments of a wide range of naturally occurring proline Psi angles and thus can be exploited to probe molecular recognition and functional properties of biological systems.