Total Synthesis of (+)-Shearilicine

Hydrodealkenylative C(sp3)-C(sp2) Bond Fragmentation Using Isayama-Mukaiyama Peroxidation

Advancements in radical capture strategies have expanded the range of products accessible from alkenes through dealkenylative synthesis. These methods, however, are still limited, as they rely on ozonolysis to generate the key peroxide intermediates from alkenes. Ozonolysis has several limitations. It is not compatible with alkenes containing electron-rich aromatics. It is also inapplicable to certain alkene substitution patterns in the context of dealkenylative synthesis. Additionally, it struggles with sterically hindered alkenes, internal nucleophiles and electrophiles, and allylic alcohols. In this paper, using Isayama-Mukaiyama peroxidation (IMP), we address the limitations of ozonolysis to rescue previously inaccessible alkene substrates and broaden the applicability of dealkenylative functionalization. In particular, we apply IMP in hydrodealkenylation and describe a novel radical hydrogenation condition─employing catalytic [FeIII], catalytic benzenethiol, and γ-terpinene in refluxing methanol─to resolve β-scission issues associated with IMP-generated alkyl silylperoxides.

Synthesis through C(sp3)-C(sp2) Bond Scission in Alkenes and Ketones

ConspectusThe homolytic cleavage of C-C bonds adjacent to functional groups has recently become a popular strategy for restructuring the skeletons of complex organic molecules. In contrast to the traditional reactivity profiles of polar bond disconnections, homolytic scission furnishes carbon-centered free radicals primed for controlled termination with a diverse range of radicophiles. Beyond standard radical capture, transition-metal catalysis facilitates sophisticated C-C and C-heteroatom bond-forming reactions. Intensive efforts have been focused over many years into the cleavage of the neighboring C-C bonds of carboxylic acids and alcohols. Despite the ubiquity of alkenes and ketones in natural products, feedstock chemicals, and common synthetic intermediates, much less attention has been paid to exploiting their potential in diversifying chiral pool materials, such as terpenes and terpenoids. Defunctionalization in this manner is a powerful approach for synthesizing high-value chemicals and advanced synthetic intermediates because of the possibility to reconstruct and further decorate chirality-bearing carbon skeletons. Motivated by synthetic necessity, since 2018 our group has focused on developing ozonolysis-based dealkenylative molecular diversification, and we expanded into deacylation in 2025. In this Account, we chronicle our initial motivation, describe the historical background, and summarize our research into dealkenylative and deacylative synthesis. Our dealkenylative approach capitalizes on the ozonolysis of alkenes in MeOH to generate α-methoxyhydroperoxides primed for a reaction with reducing agents. Their reduction through single electron transfer, mediated by a transition metal, leads to the formation of an alkoxyl radical that undergoes rapid β-scission, furnishing both a carbon-centered free radical and an ester group derived from the acetal carbon atom. The produced free radical can be strategically terminated by radicophiles, thereby delivering remodeled chiral molecules. Using this concept, we have developed hydrodealkenylation (through hydrogen atom transfer from benzenethiol), dealkenylative thiylation (through thiyl group transfer from diaryl disulfides), alkenylation (through addition/elimination with nitrostyrenes), and oxodealkenylation (through treatment with TEMPO followed by oxidation). Furthermore, kinetic analysis has enabled the development of a catalytic FeII/vitamin C system for dealkenylative alkynylation and halodealkenylation. Synergizing ozonolysis and copper catalysis has recently enabled aminodealkenylation through net-redox-neutral C-C cleavage followed by C-N bond formation. Although the high oxidation potential of ozone relative to organic compounds makes alkene-to-peroxide conversion possible, it also limits the applicability of dealkenylative techniques for substrates featuring ozone-sensitive functional groups. We recently overcame this constraint by first applying Isayama-Mukayiama peroxidation to olefins and then using a novel catalytic system─catalytic FeIII and PhSH with stoichiometric γ-terpinene─for ozone-free hydrodealkenylation. Beyond alkenes, we have developed a straightforward methodology for the homolytic deacylative cleavage of ketones as well, including cycloalkanones. This process is applicable in total syntheses and in the late-stage modifications of complex ketone-containing natural products.

Asymmetric Total Synthesis of Eremophilanolide Sesquiterpene Xylareremophil and Its Congeners

The first asymmetric, protecting group free total synthesis of eremophilanolide sesquiterpenes, xylareremophil (1), 2α,3α-epoxymairetolide A (2), and 2,3-seco-2,3-olide-1-deoxygenmairetolide F (3), is concisely achieved with a longest linear route of five to eight steps, starting from the known (5S)-5,6-dimethyl-2-cyclohexenone as the chiral starting material. This synthetic approach mainly features an oxa-Pauson-Khand reaction of the highly functionalized chiral aldehyde precursor, forging a γ-butenolide-fused tricyclic core framework of eremophilanolides in a one-step manner. This study provides a novel strategic perspective for the divergent synthesis of the eremophilanolide sesquiterpenes.

Pochobulbins A-F, Immunosuppressive Secopenitrem-Type Indole Diterpenoids from an Endophytic Pochonia bulbillosa

Three monoclavatol-secopenitrems (1-3), one bis-clavatol-secopenitrem (4), and two bis-5-methylpyrogallol-secopenitrems (5 and 6) were obtained from the endophytic fungus Pochonia bulbillosa KNI755. Pochobulbins A-F (1-6) are the initial instances of secopenitrem-type indole diterpenoids with a 4/6/6/5/5/6/6/6/6/6 fused decacyclic ring system. Compounds 1-4 feature a secopenitrem skeleton fused to a clavatol unit via a tetrahydro-2H-pyran bridge. Compounds 5 and 6 are the first secopenitrem-type indole diterpenoids that connect a 5-methylpyrogallol unit to a secopenitrem unit via a 1,4-dioxane bridge. The complete structures, including their absolute stereochemical assignments, were determined through comprehensive spectroscopic analyses and ECD simulations. Compounds 1, 3, and 5 inhibited T cell proliferation, and compounds 1 and 3 also inhibited B cell proliferation, exhibiting EC50 values between 4.6 and 13 μM.

Anti-diabetic and anti-inflammatory indole diterpenes from the marine-derived fungus Penicillium sp. ZYX-Z-143

Seven new indole-diterpenoids, penpaxilloids A-E (1-5), 7-methoxypaxilline-13-ene (6), and 10-hydroxy-paspaline (7), along with 20 known ones (8-27), were isolated from the marine-derived fungus Penicillium sp. ZYX-Z-143. Among them, compound 1 was a spiro indole-diterpenoid bearing a 2,3,3a,5-tetrahydro-1H-benzo[d]pyrrolo[2,1-b][1,3]oxazin-1-one motif. Compound 2 was characterized by a unique heptacyclic system featuring a rare 3,6,8-trioxabicyclo[3.2.1]octane unit. The structures of the new compounds were established by extensive spectroscopic analyses, NMR calculations coupled with the DP4 + analysis, and ECD calculations. The plausible biogenetic pathway of two unprecedented indole diterpenoids, penpaxilloids A and B (1 and 2), was postulated. Compound 1 acted as a noncompetitive inhibitor against protein tyrosine phosphatase 1B (PTP1B) with IC50 value of 8.60 ± 0.53 μM. Compound 17 showed significant α-glucosidase inhibitory activity with IC50 value of 19.96 ± 0.32 μM. Moreover, compounds 4, 8, and 22 potently suppressed nitric oxide production on lipopolysaccharide-stimulated RAW264.7 macrophages.

Dealkenylative Functionalizations: Conversion of Alkene C(sp3)-C(sp2) Bonds into C(sp3)-X Bonds via Redox-Based Radical Processes

This review highlights the history and recent advances in dealkenylative functionalization. Through this deconstructive strategy, radical functionalizations occur under mild, robust conditions. The reactions described proceed with high efficiency, good stereoselectivity, tolerate many functional groups, and are completed within a matter of minutes. By cleaving the C(sp3)-C(sp2) bond of terpenes and terpenoid-derived precursors, rapid diversification of natural products is possible.

Heck Macrocyclization in Forging Non-Natural Large Rings including Macrocyclic Drugs

The intramolecular Heck reaction is a well-established strategy for natural product total synthesis. When constructing large rings, this reaction is also referred to as Heck macrocyclization, which has proved a viable avenue to access diverse naturally occurring macrocycles. Less noticed but likewise valuable, it has created novel macrocycles of non-natural origin that neither serve as nor derive from natural products. This review presents a systematic account of the title reaction in forging this non-natural subset of large rings, thereby addressing a topic rarely covered in the literature. Walking through two complementary sections, namely (1) drug discovery research and (2) synthetic methodology development, it demonstrates that beyond the well-known domain of natural product synthesis, Heck macrocyclization also plays a remarkable role in forming synthetic macrocycles, in particular macrocyclic drugs.