Total Synthesis of Aaptamine, Demethyloxyaaptamine, and Their 3-Alkylamino Derivatives

Oxidative Cyclization at ortho-Position of Phenol: Improved Total Synthesis of 3-(Phenethylamino)demethyl(oxy)aaptamine

A shorter synthesis of the demethyl(oxy)aaptamine skeleton was developed via oxidative intramolecular cyclization of 1-(2-azidoethyl)-6-methoxyisoquinolin-7-ol followed by dehydrogenation with a hypervalent iodine reagent. This is the first example of oxidative cyclization at the ortho-position of phenol that does not involve spiro-cyclization, resulting in the improved total synthesis of 3-(phenethylamino)demethyl(oxy)aaptamine, a potent anti-dormant mycobacterial agent.

Direct Nitration of Vinylcycles with Copper Nitrate

A direct nitration of vinylcyclopropanes is disclosed with Cu(NO₃)₂ and KI in a regio- and stereoselective manner to afford nitroalkenes efficiently, where the cyclopropane skeleton was retained. The given method could be extended to other vinylcycles as well as biomolecule derivatives with wide substrate scope, good functionality tolerance, and efficient synthesis modularity. Further transformations illustrated the obtained products as versatile building blocks in organic synthesis. The proposed ionic pathway could account for the untouched small ring and the effect of KI during the reaction.

Antinociceptive Effects of Aaptamine, a Sponge Component, on Peripheral Neuropathy in Rats

Aaptamine, a natural marine compound isolated from the sea sponge, has various biological activities, including delta-opioid agonist properties. However, the effects of aaptamine in neuropathic pain remain unclear. In the present study, we used a chronic constriction injury (CCI)-induced peripheral neuropathic rat model to explore the analgesic effects of intrathecal aaptamine administration. We also investigated cellular angiogenesis and lactate dehydrogenase A (LDHA) expression in the ipsilateral lumbar spinal cord after aaptamine administration in CCI rats by immunohistofluorescence. The results showed that aaptamine alleviates CCI-induced nociceptive sensitization, allodynia, and hyperalgesia. Moreover, aaptamine significantly downregulated CCI-induced vascular endothelial growth factor (VEGF), cluster of differentiation 31 (CD31), and LDHA expression in the spinal cord. Double immunofluorescent staining showed that the spinal VEGF and LDHA majorly expressed on astrocytes and neurons, respectively, in CCI rats and inhibited by aaptamine. Collectively, our results indicate aaptamine's potential as an analgesic agent for neuropathic pain. Furthermore, inhibition of astrocyte-derived angiogenesis and neuronal LDHA expression might be beneficial in neuropathy.

Anti-Mycobacterial N-(2-Arylethyl)quinolin-3-amines Inspired by Marine Sponge-Derived Alkaloid

The synthesis and evaluation of simplified analogs of marine sponge-derived alkaloid 3-(phenethylamino)demethyl(oxy)aaptamine were performed to develop novel anti-mycobacterial substances. Ring truncation of the tricyclic benzo[de][1,6]-naphthyridine skeleton effectively weakened the cytotoxicity of the natural product, and the resulting AC-ring analog exhibited good anti-mycobacterial activity. A structure-activity relationship (SAR) study, synthesizing and evaluating some analogs, demonstrated the specificity and importance of the N-(2-arylethyl)quinolin-3-amine skeleton as a promising scaffold for anti-mycobacterial lead compounds.

Synthesis of Natural Products by C-H Functionalization of Heterocycless

Total synthesis is considered by many as the finest combination of art and science. During the last decades, several concepts were proposed for achieving the perfect vision of total synthesis, such as atom economy, step economy, or redox economy. In this context, C-H functionalization represents the most powerful platform that has emerged in the last years, empowering rapid synthesis of complex natural products and enabling diversification of bioactive scaffolds based on natural product architectures. In this review, we present an overview of the recent strategies towards the total synthesis of heterocyclic natural products enabled by C-H functionalization. Heterocycles represent the most common motifs in drug discovery and marketed drugs. The implementation of C-H functionalization of heterocycles enables novel tactics in the construction of core architectures, but also changes the logic design of retrosynthetic strategies and permits access to natural product scaffolds with novel and enhanced biological activities.

A nitrogen-doped asymmetric phenalenyl with a zwitterionic ground state

Herein, an asymmetric N-doped phenalenyl (BTAP) compound has been synthesized and carefully studied for the first time. The synthesis of BTAP reveals a planar configuration and an unexpected zwitterionic ground state with the negative charge delocalized around the circumjacent part and the positive charge mainly localized on the center.

Marine Natural Products: A Potential Source of Anti-hepatocellular Carcinoma Drugs

Hepatocellular carcinoma (HCC) has high associated morbidity and mortality rates. Although chemical medication represents a primary HCC treatment strategy, low response rates and therapeutic resistance serve to reduce its efficacy. Hence, identifying novel effective drugs is urgently needed, and many researchers have sought to identify new anti-cancer drugs from marine organisms. The marine population is considered a "blue drug bank" of unique anti-cancer compounds with diverse groups of chemical structures. Here, we discuss marine-derived compounds, including PM060184 and bryostatin-1, with demonstrated anti-cancer activity in vitro or in vivo. Based on the marine source (sponges, algae, coral, bacteria, and fungi), we introduce pharmacological parameters, compound-induced cytotoxicity, effects on apoptosis and metastasis, and potential molecular mechanisms. Cumulatively, this review provides insights into anti-HCC research conducted to date in the field of marine natural products and marine-derived compounds, as well as the potential pharmacological mechanisms of these compounds and their status in drug development.

Aromatic Ring Substituted Aaptamine Analogues as Potential Cytotoxic Agents against Extranodal Natural Killer/T-Cell Lymphoma

A chemical modification study was conducted on the marine natural product aaptamine (1), isolated from the marine sponge Aaptos aaptos. Thirty new derivatives substituted by various aromatic rings at the 3- and 7-positions of aaptamine were prepared by bromination, followed by the Suzuki coupling reaction. Sixteen compounds displayed cytotoxicities to four cancer cell lines (IC₅₀ < 10 μM). In particular, compound 5i demonstrated a significant antiproliferative effect on the extranodal natural killer/T-cell lymphoma (ENKT) cell line SNK-6 with an IC₅₀ value of 0.6 μM. Additionally, compound 5i showed cytotoxicities to multiple lymphoma cell lines, including Ramos, Raji, WSU-DLCL2, and SU-DHL-4 cells.

3-(Phenethylamino)demethyl(oxy)aaptamine as an anti-dormant mycobacterial substance: Isolation, evaluation and total synthesis

3-(Phenethylamino)demethyl(oxy)aaptamine (1) was re-discovered from the marine sponge of Aaptos sp. as an anti-dormant mycobacterial substance through the bioassay-guided separation. Compound 1 showed potent anti-microbial activity against Mycobacterium bovis BCG with a minimum inhibitory concentration of 0.75 µg/mL under both aerobic conditions and hypoxic conditions inducing dormant state. Compound 1 was also effective against pathogenic M. tuberculosis strains including clinical multidrug-resistant strains. Furthermore, the successful total syntheses of 1 and its analog 3-aminodemethyl(oxy)aaptamine (2) afford sufficient quantities for further biological studies.

Rhodium(III)-Catalyzed Oxidative Annulation of 4-Aminoquinolines and Acrylate through Two Consecutive C(sp2)-H Activations

The C-H annulation of the five-position of quinolines and acrylates to afford heterocycles is an active field of research in organic synthesis. Herein the annulation of 4-aminoquinolines with acrylates through two consecutive C-H activations catalyzed by Rh(III) is described. The reaction proceeds with high atom efficiency under mild reaction conditions, and this protocol will provide appealing strategies for the synthesis of fused quinoline heterocycles.