The first total synthesis of (+)-curvicollide C has been accomplished. Cross-metathesis and Julia–Kocienski olefination were instrumental in the synthesis of 1,3-diene segments and allowed for a ...ternary-convergent synthetic design. A full structural assignment is proposed for (−)-curvicollide C, a uniquely structured polyketide of fungal origin.
The enantioselective synthesis of (+)-17-norcharaciol is described. An uncatalyzed intramolecular carbonyl-ene reaction and a ring-closing metathesis were used as key C/C-connecting transformations ...to assemble the trans-bicyclo10.3.0pentadecane norditerpenoid core. We also report the evolution of our synthetic strategy toward the fully substituted characiol skeleton and the experiences from this venture.
Daphnicyclidin Alkaloids 2001–2023 Gierok, Jan; Hiersemann, Martin
European journal of organic chemistry,
July 8, 2024, Volume:
27, Issue:
26
Journal Article
Peer reviewed
Open access
The Daphniphyllum alkaloids represent a particularly diverse class of complex diterpene alkaloids, which are characterized by their enormous structural diversity. The daphnicyclidins, a subgroup of ...these alkaloids, stand out due to their unique pentafulvene structural motif. This review article gives an overview of the compounds that have been isolated so far and can be assigned to this subgroup. Furthermore, all synthesis approaches and total syntheses published to date are presented.
This review article provides a chronological overview of the 23 structurally diverse daphnicyclidin alkaloids isolated to date and highlights the various synthesis contributions that have been published to date on this unique group of alkaloids.
A combined computational and experimental study on the Claisen rearrangement of a 2-alkoxycarbonyl-substituted allyl vinyl ether in the presence of thioureas as potential noncovalent organocatalysts ...has been performed. DFT calculations employing different basis sets were utilized to predict a catalytic cycle for the thiourea-catalyzed Claisen rearrangement. The nature of the transition state in the presence and absence of thioureas was studied in detail. Critical geometrical data of the transition state that are indicators for the relative barrier height of the Claisen rearrangement are discussed. Although we did observe a significant transition state stabilization, due to endergonic conformational changes and endergonic complexation the overall effect on the barrier is small, in accordance with experimental results.
The enantioselective synthesis of the C8−C20 fragment of curvicollide C has been accomplished. A catalytic asymmetric Claisen rearrangement (CAC), a diastereoselective methyl cupration of an ...alkynoate, and a Julia−Kocienski olefination served as key C/C-connecting transformations.
The thermal Claisen rearrangement of allyl vinyl ethers is generally regarded as high‐performance method for diastereoselective C−C bond formation. Substrate‐induced diastereoselectivity and ...reagent‐induced enantioselectivity with stoichiometric amounts of external chiral auxiliaries have frequently been exploited to control the stereochemical course of the Claisen rearrangement. This review summarizes the attempts to catalyze the Claisen rearrangement of acyclic aliphatic allyl vinyl ethers with chiral and achiral catalysts. The best suited catalysts for the Claisen rearrangement so far identified are Lewis acids. Finally, bis(oxazoline)copper(II) complexes have found a further useful application as chiral catalysts for the first catalytic, enantioselective Claisen rearrangement − 90 years after Ludwig Claisen originally reported a 3,3‐sigmatropic rearrangement of an allyl vinyl ether.
The catalytic asymmetric Claisen rearrangement (CAC) of a highly substituted and functionalized α-alkoxycarbonyl-substituted allyl vinyl ether has been exploited to gain access to an advanced ...building block for the projected total synthesis of (−)-xeniolide F, the enantiomer of a xenicane diterpene isolated from a coral of the genus Xenia.
An Update on Cyclohepta[b]indoles Gierok, Jan; Benedix, Lars; Hiersemann, Martin
European journal of organic chemistry,
July 15, 2021, 2021-07-15, Volume:
2021, Issue:
26
Journal Article
Peer reviewed
Open access
The cycloheptabindole scaffold constitutes a salient structural motif in natural products as well as in men‐made pharmaceutically active ingredients. Cycloheptabindoles consist of an indole nucleus ...fused to a seven‐membered carbacycle. Interest in cycloheptabindole chemistry originates from natural product chemistry and medicinal chemistry. The chemistry of cycloheptabindole‐based organic functional materials may be a research area with some potential. The state of the art of cycloheptabindoloid chemism has been comprehensively and scholarly summarized by the leading review article of Stempel and Gaich in 2016. Following this lead, our Minireview covers the literature from 2016 to 2021.
Structure, function, and synthesis: The presence of the cycloheptabindole structural motive in alkaloids and in active pharmaceutical ingredients has sparked a significant advancement in synthetic methodology. In this Minireview, a conceptual approach to categorize the plethora of recently developed methods for cycloheptabindole synthesis has been taken and the core carbon structures of newly discovered cycloheptabindole‐derived natural products are delineated.
Almost 90 years after it was first described by Ludwig Claisen, a catalyzed enantioselective Claisen rearrangement has been implemented for the first time. Chiral copper(II) bis(oxazolines) catalyzed ...the Claisen rearrangement of 2‐alkoxycarbonyl‐substituted allyl vinyl ethers with enantiomeric excesses of 80–90 % (see scheme).
The first uncatalyzed and Cu(R-box)L2(SbF6)2-catalyzed {1,6}-transannular Gosteli–Claisen rearrangement of cyclic 2-alkoxycarbonyl-substituted allyl vinyl ethers to afford medium- and large-sized ...carbacycles is disclosed.
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