Synthesis and cytotoxicity of a novel series of saframycin-ecteinascidin analogs containing tetrahydro-β-carboline moieties

Recent advances in the synthesis and activity of analogues of bistetrahydroisoquinoline alkaloids as antitumor agents

Ecteinascidin 743 (Et-743), also known by the trade name Yondelis®, is the pioneering marine natural product to be successfully developed as an antitumor drug. Moreover, it is the first tetrahydroisoquinoline natural product used clinically for antitumor therapy since Kluepfel, a Canadian scientist, discovered the tetrahydroisoquinoline alkaloid (THIQ) naphthyridinomycin in 1974. Currently, almost a hundred natural products of bistetrahydroisoquinoline type have been reported. Majority of these bistetrahydroisoquinoline alkaloids exhibit diverse pharmacological activities, with some family members portraying potent antitumor activities such as Ecteinascidins, Renieramycins, Saframycins, Jorumycins, among others. Due to the unique chemical structure and exceptional biological activity of these natural alkaloids, coupled with their scarcity in nature, research seeking to provide material basis for further bioactivity research through total synthesis and obtaining compound leads with medicinal value through structural modification, remains a hot topic in the field of antitumor drug R&D. Despite the numerous reviews on the total synthesis of bistetrahydroisoquinoline natural products, comprehensive reviews on their structural modification are apparently scarce. Moreover, structural modification of bioactive natural products to acquire lead compounds with improved pharmaceutical characteristics, is a crucial approach for innovative drug discovery. This paper presents an up-to-date review of both structural modification and activity of bistetrahydroisoquinoline natural products. It highlights how such alkaloids can be used as antitumor lead compounds through careful chemical modifications. This review offers valuable scientific references for pharmaceutical chemists engaged in developing novel antitumor agents based on such alkaloid modifications, as well as those with such a goal in future.

Synthesis, structure-activity relationship, and biological evaluation of quinolines for development of anticancer agents

Tetrahydro-β-carbolines (THβCs) are a kind of natural alkaloids with multiple pharmaceutical activities. Herein, a focused compound library derived from THβCs was synthesized and their anticancer activities were studied in several cancer cell lines. Among them, three compounds showed considerable anticancer activities with low micromolar to submicromolar IC₅₀ values. The abilities to induce apoptosis and alter mitochondrial membrane potential levels, which are comparable to those of the commercial anticancer drug adriamycin, were confirmed by one representative compound (21) on the B16/F10 cell line. Our preliminary structure-activity relationship studies indicated that alkylamines with suitable lengths are very important for potency improvement.

Simplified hybrids of two anticancer bistetrahydroisoquinoline alkaloids ecteinascidin 743 and cribrostatin 4 and inhibitory activity against proliferation of cancer cells

A series of simplified hybrids/analogues of natural alkaloids ecteinascidin 743 and cribrostatin 4 have been synthesized and evaluated.

β-Carbolines as potential anticancer agents

β-Carbolines are indole alkaloids having a tricyclic pyrido[3,4-b]indole ring in their structure. Since the isolation of first β-carboline from Peganum harmala in 1841, the isolation and synthesis of various β-carboline derivatives surged in the following centuries. β-Carboline derivatives due to their widespread availability from natural sources, structural flexibility, quick reactivity and interaction with varied anticancer targets such as DNA (intercalation, groove binding, etc.), enzymes (GPX4, topoisomerases, kinases, etc.) and proteins (tubulin, ABCG2/BRCP1, etc.) have established themselves as promising lead compounds for the synthesis of various anticancer active agents. The current review covers the synthesis and isolation, anticancer activity, mechanism of action and SAR of various β-carboline containing molecules, its derivatives and congeners.

Synthesis and cytotoxicity of (-)-homo-renieramycin G and its derivatives

(-)-Homo-renieramycin G and its twenty derivatives were prepared from l-tyrosine methyl ester via a multi-step route. Their cytotoxicities were tested against four human cancer cell lines (A549, HeLa, KB and BGC-823). (-)-Renieramycin G and (-)-homo-renieramycin G showed comparable cytotoxicity against these four cancer cell lines, which indicated that the expansion of ring C from the six-membered 1,4-piperazinone to the seven-membered 1,4-diazepanone had no obvious impact on the cytotoxicity. Compound 42 with methyl side chain and compounds 38-41 with heterocyclic aromatic side chains at C-23 exhibited the most potent cytotoxicity with the IC₅₀ values at the level of 10^-6 M.

Design, synthesis and cytotoxicity of novel hexacyclic saframycin-ecteinascidin analogs

Two series of novel hexacyclic skeletons and their thirty-four derivatives were prepared from l-tryptophan and l-DOPA. The cytotoxicities of these compounds were tested against four human cancer cell lines HCT-116, HepG2, BGC-823 and A2780. Compounds with the tetrahydro-β-carboline moiety in the left-half of the hexacyclic skeleton showed more potent cytotoxicity with IC50 values in the range of 10-7-10-9 M. Compound 20 with the 4-methoxybenzamide side chain showed potent cytotoxicity towards HepG2 with an IC50 value of 1.32 nM. Compounds 29 and 30 with 2-pyridine amide and (2E)-3-(3-thifluoromethyl-phenyl)acrylic amide side chains showed selective cytotoxicity towards A2780 with IC50 values of 1.73 nM and 7 nM, respectively.

A Novel Sc(OTf)3 -Catalyzed (2+2+1)-Cycloannulation/Aza-Friedel-Crafts Alkylation Sequence toward Multicyclic 2-Pyrrolines

The rapid assembly of molecular complexity continues to be at the forefront of novel reaction development. In the pursuit of that goal, we herein report a novel Sc(OTf)₃ -catalyzed, one-pot multicomponent reaction that furnishes complex multicyclic 2-pyrrolines with excellent overall yields and perfect diastereocontrol. This process is based on our previously established (2+2+1)-cycloannulation of in situ generated 1-azaallyl cations, 1,3-dicarbonyls and primary amines. The newly formed and highly reactive aminal moiety is readily substituted with indoles and pyrroles both as external and internal π-nucleophiles to provide densely functionalized N-heterocycles with four new σ-bonds and two vicinal quaternary stereogenic centers. In addition, DFT calculations have been conducted to further characterize the intermediate 1-azaallyl cations.