Bisannulation of 2,3-Dichloro-1,4-naphthoquinone witho-Nitrophenylacetic Acid Derivatives: A Succinct Synthesis of the ABCD Ring System of Alpkinidine

Heck Reaction of 2-Oxyacrylates with Aryl Bromides: A Common Route to Monoaryl Pyruvates and Ortho Ester-Protected Monoaryl Pyruvates

A palladium-catalyzed Heck reaction between 2-oxyacrylates and aryl bromides was developed, where DavePhos was a unique ligand that efficiently promoted the reaction. The products, 2-oxycinnamates, served as excellent precursors, providing synthetically useful monoaryl pyruvates or ortho ester-protected monoaryl pyruvates depending on the nature of the 2-oxy group. The formation of such ortho esters via alkoxide addition is novel, and computational studies identified a plausible mechanism with an oxyallyl zwitterion as the key intermediate.

Toward the Total Synthesis of Alpkinidine: Synthesis of Haloquinone CE Ring System Synthons and Attempted Nucleophilic Bisannulation

Model chemistry involving the bisannulation of 2,3-dichloro-1,4-naphthoquinone with the ester enolate derived from ethyl o-nitrophenylacetic acid, which rapid assembled the ABCD ring system of a pentacyclic pyrroloacridine, has been applied to the attempted synthesis of the marine natural product alpkinidine. The reaction of ethyl o-nitrophenylacetic acid with 6,7-dichloro-2-methylisoquinoline-1,5,8(2H)-trione, required to extend the model strategy to alpkinidine, was unfruitful, giving only complex mixtures. Efforts to direct the regiochemistry of the key Michael substitution step using 6-bromo-2-methylisoquinoline-1,5,8(2H)-trione afforded an adduct sharing the complete carbon skeleton of alpkinidine, but this could not be elaborated to the natural product.

Toward the Total Synthesis of Alpkinidine: Michael Addition to Isoquinolinetrione CE Ring-System Synthons

Strategies toward the total synthesis of the marine pyrroloacridine alkaloid alpkinidine have been explored, focusing on linking quinonoid CE ring-system synthons with the A ring, followed by condensation to form the B and D rings. The key Michael addition of the ester enolate derived from ethyl o-nitrophenylacetate to 2-methylisoquinoline-1,5,8(2H)-trione proceeded with the wrong regiochemistry. This issue was addressed by incorporating the D-ring nitrogen at an earlier stage, affording advanced intermediates possessing the complete carbon skeleton of alpkinidine. However, attempts to close the D and B rings were unsuccessful. The novel isoquinolinetriones reported here, and the general strategy of connecting CE- and A-ring synthons through Michael additions, may be useful in the synthesis of other pyrrolo- and pyridoacridines, in particular the anticancer lead neoamphimedine and analogues.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Ethynylbenzenoid metabolites of Antrodia camphorata: synthesis and inhibition of TNF expression

An improved synthesis of the anti-inflammatory natural product antrocamphin A (2), involving a key Castro-Stephens reaction, is presented, along with the first total synthesis of its congener antrocamphin B (3). Approaches towards the more complex co-metabolite antrodioxolanone (4) were unsuccessful, but a samarium diiodide-mediated pinacol coupling of antrocamphin B did provide the chiral epimers (51). Antrocamphin A (2) inhibits Tumour Necrosis Factor (TNF) reporter gene expression, but its development as an anti-inflammatory agent may be limited by cytotoxicity.