Novel polycyclic 'cage'-1,2-diamines as potential anti-tuberculosis agents

Molecular Acrobatics in Polycyclic Frames: Synthesis of "Kurmanediol" via Post-synthetic Modification of Cage Molecules by Olefinic Metathesis

We report late-stage ring-opening metathesis (ROM), ring-rearrangement metathesis (RRM), and ring-closing metathesis (RCM) approaches to generate expanded pentacycloundecane (PCUD) cage derivatives. These higher-order intricate polycyclic cage systems are aesthetically pleasing and structurally intriguing. Their assembly maintains molecular symmetry during the entire synthetic sequence. To this end, metathesis-based catalysts are used to execute the ROM, RRM, and RCM strategies. The synthetic approach to these cage polycycles involves the Diels-Alder reaction, [2 + 2] photocycloaddition, RRM, ROM, and RCM as key steps.

Synthesis of Pentacycloundecane (PCUD) Based Spiro-Pyrano-Cage Framework via Ring-Closing Metathesis

Here, we demonstrate a short synthetic route to pyrano cage systems containing pentacycloundecane units by employing ring-closing metathesis (RCM) as a key step. These cage systems were constructed starting with readily available starting materials by adopting atomic economic processes such as cycloadditions (Diels-Alder reaction and [2+2] cycloaddition), Grignard addition, and olefin metathesis. The key building block, such as hexacyclic cage dione, was prepared from 1,4-naphthoquinone derivative and freshly cracked 1,3-cyclopentadiene. Some of these heterocyclic motifs are useful in biological chemistry and valuable as key synthons for high-energy-density materials.

Late-stage Modification of Cage Diones by Tandem Metathesis

Herein, we report the application of tandem ring-opening cross-metathesis (ROCM) and tandem ring-opening cross-metathesis followed by cross-metathesis (ROCM/CM) in highly strained diastereomeric heptacyclic cage diones (HCCD's) catalyzed by ruthenium catalysts. These caged diastereomeric compounds have a high degree of ring strain as well as steric congestion. Therefore, the present work related to ROCM is unique and intricate as compared to simple norbornene derivatives. It is useful to prepare new hexacyclic cage derivatives suitable for high-energy density materials. The synthetic strategy of starting cage compounds features the Diels-Alder reaction, and [2+2] photocycloaddition as key steps.

2-Oxaadamant-1-yl Ureas as Soluble Epoxide Hydrolase Inhibitors: In Vivo Evaluation in a Murine Model of Acute Pancreatitis

In vivo pharmacological inhibition of soluble epoxide hydrolase (sEH) reduces inflammatory diseases, including acute pancreatitis (AP). Adamantyl ureas are very potent sEH inhibitors, but the lipophilicity and metabolism of the adamantane group compromise their overall usefulness. Herein, we report that the replacement of a methylene unit of the adamantane group by an oxygen atom increases the solubility, permeability, and stability of three series of urea-based sEH inhibitors. Most of these oxa-analogues are nanomolar inhibitors of both the human and murine sEH. Molecular dynamics simulations rationalize the molecular basis for their activity and suggest that the presence of the oxygen atom on the adamantane scaffold results in active site rearrangements to establish a weak hydrogen bond. The 2-oxaadamantane 22, which has a good solubility, microsomal stability, and selectivity for sEH, was selected for further in vitro and in vivo studies in models of cerulein-induced AP. Both in prophylactic and treatment studies, 22 diminished the overexpression of inflammatory and endoplasmic reticulum stress markers induced by cerulein and reduced the pancreatic damage.

Design and synthesis of two new steroid derivatives with biological activity on heart failure via the M2-muscarinic receptor activation

Several drugs have been prepared to treat of heart failure using some protocols which require dangerous reagents and specific conditions. The aim of this study was to synthesize a series of steroid derivatives (compounds 2 to 18) using some chemical strategies. The biological activity of steroid derivatives against heart failure was evaluated using an ischemia/reperfusion model. In addition, the effect exerted by compounds 4 or 5 on left ventricular pressure was evaluated in the absence or presence of yohimbine, butaxamine and methoctramine. The results showed that 1) both compounds 4 or 5 significantly decrease the heart failure (translated as infarct area) compared with the compounds 2, 3 and 6-18. In addition, the compound 4 and 5 decreased the left ventricular pressure in a dose-dependent manner and this effect was significantly inhibited in the presence of methoctramine (p = 005). In conclusion, the compounds 4 or 5 decrease both the infarct area and left ventricular pressure via M₂-muscarinic receptor activation.

Synthetic Entry to the 2-Azatricyclo[4.3.2.04,9]undecane Ring System via Tropone

A synthesis of the 2-azatricyclo[4.3.2.0^4,9]undecane ring system-a hitherto unreported bridged azatricyclic ring system-beginning from tricarbonyl(tropone)iron and allylamine was accomplished in three steps: (1) aza-Michael addition of allylamine to tricarbonyl(tropone)iron; (2) Boc-protection of the resulting secondary amine; and (3) oxidative demetallation leading to a spontaneous intramolecular Diels-Alder reaction. The effect of a variety of parameters on the intramolecular Diels-Alder reaction was investigated, including diene and dienophile substitution patterns and dienophile tether length.

A new skeletal rearrangement of 1,7-dimethyl Cookson's cage dione catalyzed by a Lewis acid

A methyl-substituted polycyclic cage dione containing the PCUD framework has undergone an unprecedented ring rearrangement approach. Here, the PCUD framework with the aid of a Lewis acid such as BF3·MeOH gave unusual fragmentation products. Two new products were isolated via the skeletal rearrangement process involving carbocation mediated intermediates. The substituents in the succinyl bond present in the strained PCUD skeleton produce a driving force for the rearrangement in an unprecedented manner. Interestingly, the cyclobutane ring was transformed to cyclopentane through the cleavage of the C1-C7 bond during the ring-expansion process of PCUD via the carbocation intermediates. Unexpectedly, solvent (benzene) was captured during the ring-homologation process due to the presence of methyl substituents placed at the cyclobutane ring of the cage framework. It appears that this is the first report where an unexpected ring-rearrangement, ring-homologation, and ring-fragmentation occur with the aid of the BF3·MeOH complex.

Strategies towards the synthesis of anti-tuberculosis drugs

In this report, we reviewed the strategies towards the synthesis of anti-tuberculosis drugs. They include semisynthetic approaches, resolution based strategies, microbial transformations, solid phase synthesis, and asymmetric synthesis.

Molecular Acrobatics in Polycyclic Frames: Synthesis of Functionalized D3-Trishomocubanes via the Rearrangement Approach

A new synthetic route to D₃-trishomocubanone and oxa- D₃-trishomocubane derivatives has been established by the rearrangement approach. A remotely located methyl substituent in the six-membered ring contributed to the acid-catalyzed rearrangement of the cage dione in an unusual fashion. This rearrangement approach provided an attractive route to extended D₃-trishomocubanes, which are not accessible by the conventional multistep synthetic sequence. For the first time, two phenyl groups were incorporated from the solvent into the strained trishomocubane skeleton in an unprecedented manner via carbocation-mediated rearrangement with the aid of BF₃·OEt₂. Interestingly, an oxa-bridged trishomocubane skeleton was also formed during acid-promoted rearrangement.

Synthesis and Biological Evaluations of NO-Donating Oxa- and Aza-Pentacycloundecane Derivatives as Potential Neuroprotective Candidates

In order to utilize the neuroprotective properties of polycyclic cage compounds, and explore the NO-donating ability of nitrophenyl groups, an array of compounds was synthesized where the different nitrophenyl groups were appended on oxa and aza-bridged cage derivatives. Biological evaluations of the compounds were done for cytotoxicity, neuroprotective abilities, the inhibition of N-methyl-d-aspartate (NMDA)-mediated Ca²⁺ influx, the inhibition of voltage-mediated Ca²⁺ influx, and S-nitrosylation abilities. All of the compounds showed low toxicity. With a few exceptions, most of the compounds displayed good neuroprotection and showed inhibitory activity for NMDA-mediated and voltage-gated calcium influx, ranging from high (>70%) to low (20–39%) inhibition. In the S-nitrosylation assay, the compounds with the nitro moiety as the NO-donating group exhibited low to good nitrosylation potency compared to the positive controls. From the biological evaluation of the tested compounds, it was not possible to obtain a simple correlation that could explain the results across all of the biological study domains. This can be ascribed to the independent processes evaluated in the different assays, which reiterate that neuroprotection is a result of multifactorial biochemical mechanisms and interactions. However, these results signify the important aspects of the pentacylcoundecylamine neuroprotectants across different biological study realms.