A Formal Synthesis of Komaroviquinone: Use of a Pt-Catalyzed Hydrative Cyclization Reaction

Exploring the synthetic potential of epoxide ring opening reactions toward the synthesis of alkaloids and terpenoids: a review

Epoxides are oxygen containing heterocycles which are significantly employed as crucial intermediates in various organic transformations. They are considered highly reactive three-membered heterocycles due to ring strain and they undergo epoxide ring opening reactions with diverse range of nucleophiles. Epoxide ring-opening reactions have gained prominence as flexible and effective means to obtain various functionalized molecules. These reactions have garnered substantial attention in organic synthesis, driven by the need to comprehend the synthesis of biologically and structurally important organic compounds. They have also found applications in the synthesis of complex natural products. In this review article, we have summarized the implementation of epoxide ring opening reactions in the synthesis of alkaloids and terpenoids based natural products reported within the last decade (2014-2023).

Total Syntheses of (±)-Dracocephalone A and (±)-Dracocequinones A and B

Described herein are the first total syntheses of (±)-dracocephalone A (1) and (±)-dracocequinones A (4) and B (5). The synthesis was initially envisioned as proceeding through an intramolecular isobenzofuran Diels-Alder reaction, a strategy that eventually evolved into a Lewis acid-promoted spirocyclization. This highly diastereoselective transformation set the stage for trans-decalin formation and a late-stage Suárez oxidation that produced a [3.2.1] oxabicycle suited for conversion to 1. Brønsted acid-mediated aromatization, followed by a series of carefully choreographed oxidations, allowed for rearrangement to a [2.2.2] oxabicycle poised for conversion to 4 and 5.

Recent Developments with Icetexane Natural Products

Icetexane diterpenoids are a diverse family of natural products sourced from several species of terrestrial plants. Icetexanes exhibit a broad array of biological activities and together with their complex 6-7-6 tricyclic scaffolds, they have piqued the interest of synthetic organic chemists, natural products chemists, and biological investigators over the past four decades and were reviewed 13 years ago. This review summarizes icetexane natural products isolated since 2009, provides an overview of new synthetic approaches to the icetexane problem, and proposes an additional classification of icetexanes based on novel structures that are unlike previously isolated materials.

Ligand-controlled chemoselectivity in gold-catalyzed cascade cyclization of 1,4-diene-tethered 2-alkynylbenzaldehydes

A synthetic method that relies on the gold(i)-catalyzed cascade annulation of skipped 1,4-diene-tethered 2-alkynylbenzaldehydes for the chemo- and stereoselective assembly polycyclic bridged-pyrrolidines and -azepines is described.

THF-Enabled PtBr2-Catalyzed Desymmetric Hydrogenative [3 + 2] Cycloaddition of 2-Alkynylbenzaldehyde-Tethered Cyclohexadienones

A THF-enabled PtBr2-catalyzed desymmetric hydrogenative [3 + 2] cycloaddition of 2-alkynylbenzaldehyde-tethered cyclohexadienones has been developed. The protocol provides a highly functionalized 6-7-6 polycyclic skeleton with four contiguous stereocenters in good...

Efficient Synthesis of Icetexane Diterpenes and Apoptosis Inducing Effect by Upregulating BiP-ATF4-CHOP Axis in Colorectal Cells

We herein present an efficient and robust synthetic strategy toward 12 icetexane diterpenes and their derivatives, which features a PPh₃/DIAD-mediated rearrangement of the reduced carnosic acid derivative (2) to give (-)-barbatusol (3) in a regioselective and scalable way. MTT assay led to the identification of (+)-grandione (11) and (-)-demethylsalvicanol o-quinone derivative (9) as highly cytotoxic agents against HCT-116, COLO-205, and Caco-2 cells. Interestingly, (+)-grandione (11) induced the HCT-116 cell apoptosis in a dose-dependent manner, which might be attributed to the upregulation of the BiP-ATF4-CHOP axis and promotion of the BiP-ATF4 interactions, thereby leading to endoplasmic reticulum (ER) stress. This work not only paves an efficient and scalable pathway to access icetexane diterpenes but also provides new leads for the development of anticolorectal agents with a unique mode of action.

Gold-Catalyzed Synthesis of Icetexane Cores: Short Synthesis of Taxamairin B and Rosmaridiphenol

We report the short synthesis of two natural products, rosmaridiphenol and taxamairin B, from key intermediates 5a and 5b, which were prepared from enynals 8a and 9b, respectively, by using a gold-catalyzed cyclization reaction. This approach can be widely applied in the synthesis of [6,7,6]-fused tricyclic compounds found in many icetexane diterpenoids.