Enantioselective Total Synthesis of (-)-Artatrovirenol A

Bioinspired Stereoselective Total Synthesis of the Caged Sesquiterpenoid Daphnepapytone A

The first total synthesis of the novel caged sesquiterpenoid daphnepapytone A is disclosed. Key reactions include a Pauson-Khand cycloaddition to provide oleodaphone, a bioinspired photoinduced [2 + 2] cycloaddition to forge the cyclobutane-containing caged skeleton, and a C-H oxidation and reduction protocol to generate daphnepapytone A. Finally, the 17-step synthetic sequence is shortened to 4 steps in protecting group-free and exclusively stereoselective fashion.

Cu(I)-Catalyzed Enantioselective Epoxidation of Aldehydes with α-Trifluoromethyl Diazosilanes

Catalytic epoxidation of readily available aldehydes with diazo compounds is an atom economical strategy to synthesize epoxides. However, the asymmetric epoxidation reaction of aldehydes and fluorinated diazo compounds is challenging, because of the severe racemic background reaction. Herein, we report the first Cu(I)-catalyzed enantioselective epoxidation reaction between aldehydes and α-trifluoromethyl diazosilanes for the synthesis of chiral trifluoromethyl epoxides. This reaction features mild conditions, broad substrate scope, excellent diastereoselectivity and enantioselectivity. The observed positive nonlinear effect supports the ligand acceleration and the achievement of high enantioselectivity with a chiral ligand possessing lower enantiopurity. The gram scale reaction and down-stream transformation based on the removable silyl group demonstrated the synthetic potential of the reaction.

Recent advancements in the chemistry of Diels-Alder reaction for total synthesis of natural products: a comprehensive review (2020-2023)

Despite being discovered nearly a century ago, the Diels-Alder (DA) reaction remains a crucial tool in the total synthesis of natural products. It accommodates a broad range of building blocks with varying complexity and levels of derivatization, allowing the formation of six-membered rings with precise stereochemistry. This, in turn, simplifies the synthesis of core structures found in many natural products. In recent years, modifications to the traditional Diels-Alder reaction have expanded its scope. These modifications include the inverse electron demand Diels-Alder reaction, dehydro Diels-Alder reaction, hetero-Diels-Alder reaction, photoenolization Diels-Alder reaction, asymmetric Diels-Alder reaction, and domino Diels-Alder reaction have been employed to extend the scope of this process in the synthesis of natural products. This review discusses the application of the Diels-Alder reaction in the total synthesis of natural products from 2020 to 2023, along with select methodologies that are inspired by or can be used to synthesize natural products.

Regioselective [3 + 2] Annulation of β,γ-Alkynyl-α-ketimino Esters with 1,3-Dicarbonyls: The Synthesis of Highly Functionalized Dihydrofurans

A regioselective [3 + 2] annulation of β,γ-alkynyl-α-ketimino esters with 1,3-dicarbonyls is disclosed. A series of Z-selective dihydrofurans bearing an exocyclic double bond and a quaternary carbon center are accessed without the usage of base. Control and deuterium-labeling experiments have been investigated to probe into the reaction mechanism. The catalyst and base-free nucleophilic addition highlights the transformation.

Bioinspired concise synthesis of caged Sesquiterpenoids Artatrovirenols A and B

Artatrovirenols A and B are two newly isolated sesquiterpenoids with a complex caged framework. We report herein a concise synthesis of artatrovirenols A and B in 9 and 8 steps, respectively. The complex caged tetracycle is rapidly constructed from a known planar guaiane-type precursor through a bioinspired intramolecular [4 + 2] cyclization to firstly access artatrovirenol B, which is further transformed into artatrovirenol A through a biomimetic epoxidation-mediated lactonization reaction. This synthesis establishes a concise asymmetric approach to access artatrovirenols A and B, and also provides insightful evidence to their biogenetic pathway in nature.

A New Insight into the Molecular Mechanism of the Reaction between 2-Methoxyfuran and Ethyl (Z)-3-phenyl-2-nitroprop-2-enoate: An Molecular Electron Density Theory (MEDT) Computational Study

The molecular mechanism of the reaction between 2-methoxyfuran and ethyl (Z)-3-phenyl-2-nitroprop-2-enoate was investigated using wb97xd/6-311+G(d,p)(PCM) quantum chemical calculations. It was found that the most probable reaction mechanism is fundamentally different from what was previously postulated. In particular, six possible zwitterionic intermediates were detected on the reaction pathway. Their formation is determined by the nature of local nucleophile/electrophile interactions. Additionally, the channel involving the formation of the exo-nitro Diels-Alder cycloadduct was completely ruled out. Finally, the electronic nature of the five- and six-membered nitronates as potential TACs was evaluated.

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).

Routes to Advanced Intermediates in the Synthesis of Tetracarbocyclic Sesquiterpenoids Daphnenoid A and Artatrovirenols A and B

A short route from dihydrocarvone is described, which led to the tetracarbocyclic core common to artatrovirenol A and B and daphnenoid A. A variant of this route afforded guaia-4,6-dien-3-one (from Enterospermum madagascarensis) and its epimer. From 2-(2-oxoethyl)furan, a 15-step sequence then delivered the complete carbon skeleton and all functionality necessary for daphnenoid A. Key steps in the route include diastereoselective intramolecular oxidopyrylium cycloaddition, oxa-bridge cleavage under "push-pull" conditions, and intramolecular Diels-Alder cycloaddition.