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. 2026 May 26;17(6):1303–1309. doi: 10.1021/acsmedchemlett.6c00117

Semisynthesis of Mycothiazole Analogs having Distinct Bioactivity

Jacqueline G Clarke †, Naibedya Dutta ‡, Matthew S Nickel †, Zhang Wang §,⊥, Juri Kim ‡, Joseph Media ∥, David A Coppage ⊥, Erin P McCauley #, Joe A Gerke †, Marc O Anderson 7, Ryo Higuchi-Sanabria ‡, Frederick A Valeriote ∥, Phillip Crews 8, Tyler A Johnson †,*
PMCID: PMC13266639  PMID: 42305219

Abstract

Semisynthetic modification of mycothiazole (1) with Meerwein’s salt to generate a more stable and/or potent analog than 8-O-acetylmycothiazole (2) unexpectedly yielded diastereomers devoid of the diene. Analysis of NMR, HR-LCMS, and optical rotation confirmed the structures as (−)-4,4-hydroxy-methyl-(5Z)-(8S)-(14Z)-mycothiazole (5a, 5b: dr 1:1.1). Both compounds demonstrated reduced stability versus 1 or 2. Cytotoxicity evaluation of 5a versus 5b indicated 5-fold differences in potency against pancreatic (IC50 = 7.81, 1.34 μM; PANC-1) and glioblastoma (IC50 = 8.53, 1.63 μM; U251N) cancer cells, respectively. In vivo evaluation of 5a and 5b, using Caenorhabditis elegans in aging studies, indicated 5b not 5a inhibited mitochondrial function, while neither affected lifespan compared to 1. These results demonstrate the diene of 1 may be required for its picomolar cytotoxic potency to cancer cells or effects on lifespan in C. elegans, and minor variations in the stereochemistry of this chemotype merit further investigation to modulate its bioactivity.

Keywords: mycothiazole, diene, diastereomers, cancer cell lines, C. elegans

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graphic file with name ml6c00117_0006.jpg

Structural modification of natural products remains a valuable strategy for optimizing therapeutic leads or generating distinct chemical probes that are selective. , An early example of this process can be traced to the willow tree family Salicaceae, a source of salicin semisynthesis involving hydrolysis and oxidation to generate salicylic acid, then acetylation to form acetylsalicylic acid (aka Aspirin) ca. 1897. The semisynthesis of natural products to create diverse, biologically active small molecules through modifications to one or more reactive groups has undergone a renaissance. Classic 21st century examples include a) epothilone B from Sorangium cellulosum to produce the anticancer therapeutic aza-epothilone B (aka Ixempra) or b) rapamycin analogs (aka rapalogs) from Streptomyces hygroscopicus that function as selective inhibitors of the mechanistic target of rapamycin (mTOR) pathway, a validated target for treating cancer or studying the aging process. , Novel approaches to create next-generation probes for chemical biology have also evolved using biology-oriented synthesis (BIOS) of natural product scaffolds. To date, the majority of natural product chemotypes that have undergone re-engineering are from terrestrial-derived plants or microorganisms.

Marine-derived chemotypes are steadily emerging as semisynthetic platforms to create next-generation therapeutic lead structures or chemical probes from harnessing repository extracts − along with advances in late-stage diversification of selected lead compounds. The mycothiazole chemotype (1, Figure ), isolated from the marine sponge C. mycofijiensis, remains a promising candidate for therapeutic development based on its selectivity and picomolar cytotoxic/cytostatic potency for cancer cell lines versus normal cell lines. − Acetylation of 1 to produce 8-O-acetylmycothiazole (2) resulted in the first semisynthetic analogue of this class, which also serves as a potent and selective chemical probe for studying mitochondria complex I inhibition. Interestingly, the 8R enantiomer of 1 (compound 3) displayed varied cytostatic potency to a wide array of cancer cell lines; however, 1 and 3 have not been evaluated side by side. Alternatively, 2 retains low nanomolar cytotoxic potency to selected cancer cell lines but with a room temperature shelf life stability of >6 months versus <6 weeks for 1 and was recently identified as a novel selective chemical probe to study the aging process. Also noteworthy is that structure–activity relationship (SAR) studies of 1 indicate analogues with modifications to the diene system (e.g., mycothiazole-4,19-diol, 4) have significantly reduced biological activity against cancer cells lines. ,,

1.

1

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Structures of mycothiazoles 1–5.

To improve the chemical stability and retain picomolar cytotoxic potency of 1 in cancer cell lines or as an optimized chemical probe, semisynthetic analogs were generated on a single reactive group of 1 for SAR studies. The initial goal was to substitute the bulky acetyl group on 2, for a smaller methoxy group. To convert the C-8 alcohol, we mixed 1 with Meerwein’s salt to generate a methoxy analog based on previous reports. − Upon purification of the reaction mixture, two major peaks by analytical HPLC were observed, not one as expected. The structure elucidation of these two new analogs, an explanation of their origin, along with an evaluation of their chemical stability and bioactivity in cancer cells and in aging models, are described herein.

Structure elucidation began by comparing 1H NMR of 1 with the two new semisynthetic analogs (designated 5a and 5b) which did not indicate additional methoxy chemical shifts as shown in Table S1 in the Supporting Information. Instead, methyl groups were present at CH3-19 for 5a and 5b, in place of terminal methylene protons at position H2-19 in 1. It appeared a methoxy analog of 1 was not generated in the reaction mixture, but instead diastereomers 5a and 5b were formed. Further analysis focused on 5a with scrutiny of its 13C NMR data (Table S2) that indicated 22 carbons with a substitution at C-4 in the form of a C–OH quaternary chemical shift (δC, 74.0). High-resolution liquid chromatography mass spectrometry (HR-LCMS) data for 5a (405.2207 presumably [M + H]+) in Figure S1 suggested a molecular formula of C22H34N2O3S identical to 1 (405.2197 [M + H]+). , However, the molecular ion peak did not account for the additional protons from CH3-19 (δH, 1.08; δC, 25.6) or OH substituent on C-4 (δC, 74.0). Attempts to spike samples of 5a with sodium to observe the [M + Na]+ molecular ion peak were unsuccessful. To establish the molecular formula of 5a (C22H36N2O4S), it was concluded that a dehydration event occurred ([M – H2O + H]+) involving the alcohol on C-4 (δC, 74.0). Dehydration of tertiary alcohols has been observed in metabolites derived from Cacospongia mycofijiensis analyzed by mass spectrometry such as the latrunculins. With the molecular formula established, attention turned to comparison of the Δ5,6 and Δ14,15 proton–proton coupling constants for 5a versus 1. These values measured 11.9 Hz at H-5, H6 (δH, 5.29, 5.43) and 11.8 Hz at H-14, H-15 (δH, 5.78, 5.53) respectively, on par with 1 indicating both 5a and 1 shared the same 5Z, 14Z stereochemistry. The working structure of 5a was secured from gCOSY correlations in Figure observed between H-2 to H-3 and H-5 through H-8 along with key HMBC correlations with H-5 to C-4, H-5 to C-6, H-6 to C-8, and H3-19 to C-4 and C-5. Orientation of the C-8 hydroxyl on 5a was assigned the 8S configuration, based on use of 1 as the starting material. Compound 5b exhibited nearly identical HR-LCMS and NMR data to 5a as shown in Figures S1 and S5–S16. All 1H NMR chemical shifts observed for 5a and 5b were within 0.5 ppm. Subtle 13C NMR changes including ∼3.0, ∼1.5 and ∼1.5 ppm chemical shift differences were observed between C-3 (δC, 37.2), C-6 (δC, 122.5), and C-19 (δC, 25.6) for 5a versus C-3 (δC, 40.7), C-6 (δC, 124.1), and C-19 (δC, 23.9) in 5b respectively. Optical rotation (OR) values were also measured for 5a and 5b (−24.6 and −7.71 respectively) and compared to 1–3 shown in Table S3. The observed differences in NMR and OR data between 5a and 5b were attributed to the opposite orientations of their CH3-19 and OH substituents on position C-4. Ultimately, the working structures of the new analogs 5a and 5b were characterized as (−)-4,4-hydroxy-methyl-(5Z)-(8S)-(14Z)-mycothiazole as shown in Figure .

2.

2

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Key gCOSY and HMBC correlations of (−)-4,4-hydroxy-methyl-(5Z)-(8S)-(14Z)-mycothiazole (5a).

The origin of the diastereomers (5a and 5b) may result from the chemical instability of 1 when exposed to either oxygen and/or protic species during semisynthesis experiments. Previous experiments have shown exposure of 1 to oxygen can lead to the production of the degradation product mycothiazole-4,19-diol (4); with a plausible mechanism shown in Scheme , a hydroperoxyl radical is formed by the abstraction of a hydrogen atom from the bis-allylic position at C-16. The hydroperoxyl radical then adds to the diene at C-4, forming an allylic radical intermediate. , This allylic radical allows for a cis–trans isomerization and an epoxide formation occurring between C-4 and C-19. , This epoxide subsequently can undergo an epoxide hydrolysis creating the 4,19-diol. Outlined in Scheme is a proposed mechanism showing how 1 combined with Meerwein’s salt ([CH3)3O]+/[BF4]−), could create 5. To explore the proposed mechanism, this reaction was run with 50 μL of deuterated water (D2O) to screen for the deuterated proton at the C-4 hydroxy; however, no reaction occurred as was the case with addition of 50 μL of water (H2O) shown in Figures S19–S20 respectively. The original reaction conditions were rerun (same day) producing diastereomers (5a, 5b) as shown in Figure S21. During semisynthesis experiments with 1 to create 2 or 5, anhydrous conditions were not established on reaction vessels or by flame drying of our glassware, which may allow traces of H2O to participate in the reactions. Although acetylation of 1 to produce 2 proceeds without incident under these conditions, ,− methylation of the C-8 hydroxy on 1 using Meerwein’s salt may require more stringent conditions that are a) anhydrous and b) neutralizing with a base (e.g., proton sponge) to counter the effects of any residual acid (e.g., HBF4) in the system.

1. Plausible Mechanism: Exposure of Mycothiazole (1) to Oxygen (O2) and Hygroscopic (H2O) Conditions Leads to the Production of (−)-(5E)-(8S)-(14Z)-Mycothiazole-4,19-diol (4).

1

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2. Proposed Mechanism: Exposure of 1 to Tetrafluoroboric Acid (HBF4) in Dichloromethane (DCM) at Room Temperature (RT) along with H2O in the Reaction Vessel Leads to the Production of (−)-4,4-Hydroxy-methyl-(5Z)-(8S)-(14Z)-mycothiazole (5a,5b).

2

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Determination of the relative stereochemistry at position C-4 on 5a, 5b was not undertaken at this time. Prioritization was given to determine if compounds 5a and 5b demonstrated: a) improved chemical stability (shelf life), b) retained or enhanced cytotoxic potency compared to 1–2 against cancer cell lines, and/or c) retained or enhanced gerotherapuetic effects in vivo in C. elegans. Chemical stability studies were conducted with freshly prepared and purified 5a and 5b in comparison with 1–2 over several weeks. Each compound was dried down under nitrogen, stored in amber vials at room temperature (20 °C), then brought up in fresh C6D6 for weekly NMR analysis to assess compound degradation. The 1H NMR spectra of both 5a and 5b 4 weeks after purification (Figures S17–S18) indicated each have reduced chemical stability with a shelf life stability of <4 weeks compared to 1 (<6 weeks). Surprisingly, despite the absence of the diene in 5a and 5b, both compounds decomposed at a similar rate to 1. This observation suggests the diene in 1 may not be entirely responsible for its instability; rather, the C-8 alcohol is also suspect and could explain why the C-8 acetylated semisynthetic analog 2 has a shelf life stability >6 months in similar conditions.

During the course of our chemical stability studies, the cytotoxicity of 5a and 5b were evaluated against pancreatic (PANC-1) and glioblastoma (U251N) cancer cell lines that gave IC50 values of 7.81 μM (PANC-1) and 8.53 μM (U251N) for 5a and 1.34 μM (PANC-1) and 1.63 μM (U251N) for 5b as shown in Table . Cytotoxicity assays were performed using freshly purified samples of 5a and 5b under conditions that minimized decomposition. Compound 5a was 5-fold weaker than 5b in terms of its cytotoxic potency to PANC-1 and U251N cancer cell lines. Overall, the IC50 values of 5a and 5b were approximately 380-fold and 70-fold less potent respectively compared to 1 (IC50 = 0.022 μM, PANC-1 and 0.021 μM U251N). These results indicate the diene in 1 or 2 may be required for its picomolar to low nanomolar cytotoxic potency to selected cancer cell lines.

1. Cytotoxic Responses of 1, 5a, and 5b Against Selected Cancer Cell Lines.

  IC50 (μM)
compound PANC-1 U251N
(+)-(5Z)-(8S)-(14Z)-Mycothiazole (1) 0.022 0.021
(−)-4,4-Hydroxy-methyl-(5Z)-(8S)-(14Z)-mycothiazole (5a) 7.81 8.53
(−)-4,4-Hydroxy-methyl-(5Z)-(8S)-(14Z)-mycothiazole (5b) 1.34 1.63
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a

Pancreatic (PANC-1) and

b

Glioblastoma (U251N) cancer cell lines.

c

Sample was evaluated 4–6 weeks after HPLC purification and likely underwent degradation as reported previously.

To determine the physiological impact of 5a and 5b in vivo, we tested the biological effects of these compounds on mitochondrial function in vivo using C. elegans as a model (Figure A) compared to 1–2. As previously described, C. elegans treated with 1 (Figure B) or 2 (not shown) displayed a significant reduction in oxygen consumption rate (OCR). , Interestingly, similar to 1, compound 5b significantly reduced the level of the oxygen consumption rate (OCR); however, 5a did not. To ensure that the change in the level of the OCR was due to a reduction in mitochondrial respiration, we treated animals with sodium azide to inhibit mitochondrial respiration. No differences in nonmitochondrial respiration across all conditions were observed. Importantly, 5a had no measurable effect on the level of the OCR, suggesting that unlike 1 and 5b, compound 5a does not affect mitochondrial function in vivo in C. elegans. As expected, the reduction of mitochondrial OCR upon treatment with 1 and 5b correlated with increased fragmentation, most prominent in day 15 animals shown in Figure C. Mitochondrial morphology was quantified using mitoMAPR, which showed a significant reduction in mitochondrial branch points in day 15 animals treated with 1 and 5b, reflecting a shift from connected mitochondrial networks to a more fragmented structure. Consistent with a lack of an increase in the level of the OCR, 5a had no effect on mitochondrial morphology.

3.

3

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(A) Schematic representation of worms treated with 5 μM of compounds starting from day 1 of adulthood. (B) Seahorse analysis of mitochondrial respiration/OCR (pmol/min) of day 2 adult wild-type worms after growing them on DMSO control or 5 μM of (+)-(5Z)-(8S)-(14Z)-mycothiazole (1, abbreviated myco) or (−)-4,4-hydroxy methyl-(5Z)-(8S)-(14Z)-mycothiazole (5a, 5b) for 24 h starting from day 1 of adulthood. 50 mM sodium azide treatment was used to measure non-mitochondrial respiration. (C) Representative fluorescence micrographs of MLS::GFP expressed in the hypodermis (col-19p), of day 2, day 8, and day 15 worms grown on DMSO or 5 μM of indicated compounds starting from day 1 of adulthood. The quantification of the number of mitochondrial junction point within a defined region of interest was performed using MitoMAPR imageJ macro and is indicated in corresponding bar graph. Statistical analysis was performed by using a Wilcoxon signed-rank test. ns = not significant, P > 0.05, *P < 0.05, **P < 0.01. (D) Representative fluorescent micrograph of UPRmt transcriptional reporter worms (hsp-6p::GFP) of day 2 adult animals grown on DMSO control or 5 μM of indicated compounds for 24 h from day 1 of adulthood. (E) Survival of wild-type N2 animals grown on DMSO control or 5 μM indicated compounds from day 1 of adulthood.

Inhibition of mitochondrial electron transport chain (ETC) function can enhance the health and longevity of C. elegans through activation of the unfolded protein response of mitochondria (UPRmt). Indeed, consistent with previous results, 1 significantly increased the lifespan of animals, although the activation of the hsp-6p::GFP reporter commonly used to measure UPRmt was unchanged (Figure D). Incidentally, this is not entirely surprising as the correlation between hsp-6p::GFP and longevity are not entirely consistent. Although it was expected that 5a would not impact longevity as it did not affect mitochondrial function, we were surprised to see that 5b also did not affect longevity as shown in Figure E. It is important to note that not all conditions that disrupt mitochondrial function have a beneficial effect. Reports by others have shown that inhibition of mitochondrial complex II, mitochondrial fusion, and mitochondrial import do not display increased lifespan despite robustly activating the UPRmt. ,− Altogether, these data suggest that similar to 1, compound 5b does inhibit mitochondrial function, while 5a has no physiological impact on C. elegans. However, unlike 1–2, compound 5b does not induce a beneficial effect on the C. elegans lifespan.

Several conclusions can be drawn from the results of our semisynthetic experiments with 1 and Meerwein’s salt. First, using Meerwein’s salt to convert the C-8 alcohol on 1 does not produce an expected methoxy analog. Instead, diastereomers containing hydroxy and methyl groups at C-4 (5a and 5b) are generated. Methylation of the C-8 hydroxy on 1 using Meerwein’s salt may require more strict anhydrous conditions along with a proton sponge to counter the effects of the one equivalent acid (e.g., HBF4) generated in the reaction. − Second, compounds 5a and 5b have a reduced shelf life stability of <4 weeks versus 1 (<6 weeks) indicating the diene system of 1 may not be entirely responsible for the lability of 1 and that the C-8 hydroxy group may play a significant role, which may explain why the C-8 acetylated analog 2 has an extended shelf life stability (>six months). Third, SAR evaluation against pancreatic and glioblastoma cancer cell lines displayed a 5-fold difference in cytotoxic potency for compound 5a versus 5b. Interestingly, both compounds were 380- and 70-fold less potent respectively compared to 1 indicating the diene system may be required to retain its picomolar to low nanomolar potency to selected cancer cell lines. Lastly, while neither 5a or 5b extended life-span in C. elegans on par with 1 in aging studies, 5b inhibited mitochondrial function similar to 1, while 5a did not. Ultimately, these results underscore that minor stereochemical variations in 1 distinctly modulate its biological activity and that further SAR studies with isomers of this chemotype merit further investigation. Additional studies to explore these outcomes are currently underway in our laboratories and will be reported in due course.

Safety

No unexpected or unusually high safety hazards were encountered.

Supplementary Material

ml6c00117_si_001.pdf (1.5MB, pdf)

Acknowledgments

We thank Dr. Hasan Celik (UC Berkeley) and Pines Magnetic Resonance Center’s Core NMR Facility (PMRC Core) for spectroscopic assistance. The instruments used in this work were supported in part by the PMRC Core and NIH S10OD024998. Professor Annaliese K. Franz (UC Davis) for support with optical rotation experiments. We also gratefully acknowledge Sofia F. Odron and Joseph D. Morris for their support as laboratory members and for their helpful discussions and assistance in interpreting the mass spectrometry data. Financial support was provided by NIH Instrument Grant S10OD024998 (H.C.), R01AG079806 from the National Institute on Aging (R.H.S.), Larry L. Hillblom Foundation Grant 2022-A-010- SUP (R.H.S.), and the Fletcher Jones Endowment Fund (T.A.J.).

Glossary

Abbreviations

mTOR

mechanistic target of rapamycin

BIOS

biology-oriented synthesis

SAR

structure–activity relationship

NMR

nuclear magnetic resonance

HR-LCMS

high resolution liquid chromatography mass spectrometry

OR

optical rotation

OCR

oxygen consumption rate

ETC

electron transport chain

UPRmt

unfolded protein response of mitochondria

3O2

triplet oxygen

1O2

singlet oxygen

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsmedchemlett.6c00117.

  • Figures S1–18 are provided which include HR-LCMS analysis of 5a and 5b, 1D NMR spectra of 1–2, 5a, and 5b along with DEPT, gCOSY, HSQC, and HMBC data for 5a and 5b. Tables S1–S3 include 1H, 13C NMR and optical rotation data respectively. General experimental procedures explained (PDF)

T.A.J, F.A.V., and R.H.S. conceived the project. J.G.C. designed and performed chemistry experiments to generate analogs of 1, performed structure elucidation of 5a and 5b. J.G.C., N.D., M.S.N., and T.A.J. prepared the manuscript and figures. J.G.C. purified and prepared compounds 1–2, 5a, and 5b. J.A.G. purified compound 1. J.M. conducted cancer cell line experiments. D.A.C. provided optical rotation measurements. E.P.M., M.O.A., and M.S.N. conducted mass spectrometry experiments. N.D. and J.K. performed C. elegans experiments. Z.W., M.S.N., P.C., and T.A.J. proposed mechanisms for 4, 5a, and 5b respectively. P.C. provided repository samples of 1. J.G.C., N.D., M.S.N., R.H.S., and T.A.J. wrote the manuscript. All authors have given approval to the final version of the manuscript.

The authors declare no competing financial interest.

References

  1. Newman D. J., Cragg G. M.. Natural Products as Sources of New Drugs over the Nearly Four Decades from 01/1981 to 09/2019. J. Nat. Prod. 2020;83:770–803. doi: 10.1021/acs.jnatprod.9b01285. [DOI] [PubMed] [Google Scholar]
  2. Hong B., Luo T., Lei X.. Late-Stage Diversification of Natural Products. ACS Central Sci. 2020;6(5):622–635. doi: 10.1021/acscentsci.9b00916. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Nicolaou, K. C. ; Montagnon, T. . Molecules that Changed the World; Wiley-VCH, 2008; pp 22, 286. [Google Scholar]
  4. Morrison K. C., Hergenrother P. J.. Natural Products as Starting Points for the Synthesis of Complex and Diverse Compounds. Nat. Prod. Rep. 2014;31:6–14. doi: 10.1039/C3NP70063A. [DOI] [PubMed] [Google Scholar]
  5. Lee F. Y.F., Borzilleri R., Fairchild C. R., Kim S., Long B. H., Carmen Reventos-Suarez C., Vite G. D., Rose W. C., Kramer R. A.. BMS-247550: A Novel Epothilone Analog with a Mode of Action Similar to Paclitaxel but Possessing Superior Antitumor Efficacy. Clin. Cancer. Res. 2001;7:1429–1437. [PubMed] [Google Scholar]
  6. Lee J. J., Swain S. M.. The Epothilones: Translating from the Laboratory to the Clinic. Clin. Cancer Res. 2008;14(6):1618–1624. doi: 10.1158/1078-0432.CCR-07-2201. [DOI] [PubMed] [Google Scholar]
  7. Johnson S. C., Rabinovitch P. S., Kaeberlein M.. mTOR is a Key Modulator of Ageing and Age-Related Disease. Nature. 2013;493:338–345. doi: 10.1038/nature11861. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Mehta D., Rajput K., Jain D., Bajaj A., Dasgupta U.. Unveiling the Role of Mechanistic Target of Rapamycin Kinase (MTOR) Signaling in Cancer Progression and the Emergence of MTOR Inhibitors as Therapeutic Strategies. ACS Pharmacol. Transl. Sci. 2024;7:3758–3779. doi: 10.1021/acsptsci.4c00530. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Laplante M., Sabatini D. M.. mTOR Signaling in Growth Control and Disease. Cell. 2012;149:274–293. doi: 10.1016/j.cell.2012.03.017. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Van Hattum H., Waldmann H.. Biology-Oriented Synthesis: Harnessing the Power of Evolution. J. Am. Chem. Soc. 2014;136:11853–11859. doi: 10.1021/ja505861d. [DOI] [PubMed] [Google Scholar]
  11. Motika S. E., Hergenrother P. J.. Re-engineering Natural Products to Engage New Biological Targets. Nat. Prod. Rep. 2020;37:1395–1403. doi: 10.1039/D0NP00059K. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Lin S., McCauley E. P., Lorig-Roach N., Tenney K., Naphen C. N., Yang A., Johnson T. A., Hernadez T., Rattan R., Valeriote F. A., Crews P.. Another Look at Pyrroloiminoquinone AlkaloidsPerspectives on Their Therapeutic Potential from Known Structures and Semisynthetic Analogues. Marine Drugs. 2017;15:98. doi: 10.3390/md15040098. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Thornburg C. C., Britt J. R., Evans J. R., Akee R. K., Whitt J. A., Trinh S. K., Harris M. J., Thompson J. R., Ewing T. L., Shipley S. M., Grothaus P. G., Newman D. J., Schneider J. P., Grkovic T., O’Keefe B. R.. NCI Program for Natural Product Discovery: A Publicly-Accessible Library of Natural Product Fractions for High-Throughput Screening. ACS Chem. Biol. 2018;13:2484–2497. doi: 10.1021/acschembio.8b00389. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Senadeera S. P. D., Wang D., Wilson B. A. P., Smith E. A., Wamiru A., Martinez Fiesco J. A., Du L., Zhang P., O’Keefe B. R., Beutler J. A.. Acroamine A, a 2–Amino Adenine Alkaloid from the Marine Soft Coral Acrozoanthus australiae and Its Semisynthetic Derivatives That Inhibit cAMP-Dependent Protein Kinase A Catalytic Subunit Alpha. J. Nat. Prod. 2024;87:2014–2020. doi: 10.1021/acs.jnatprod.4c00477. [DOI] [PubMed] [Google Scholar]
  15. Li J., Cisar J. S., Zhou C.-Y., Vera B., Williams H., Rodríguez A. D., Cravatt B. F., Romo D.. Simultaneous Structure-Activity Studies and Arming of Natural Products by C-H Amination Reveal Cellular Targets of Eupalmerin Acetate. Nat. Chem. 2013;5:510–517. doi: 10.1038/nchem.1653. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Crews P., Kakou Y., Quinoa E.. Mycothiazole, a Polyketide Heterocycle from a Marine Sponge. J. Am. Chem. Soc. 1988;110:4365–4368. doi: 10.1021/ja00221a042. [DOI] [Google Scholar]
  17. Sonnenschein R. N., Johnson T. A., Tenney K., Valeriote F. A., Crews P.. A Reassignment of (−)-Mycothiazole and the Isolation of a Related Diol. J. Nat. Prod. 2006;69:145–147. doi: 10.1021/np0503597. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Morgan J. B., Mahdi F., Liu Y., Coothankandaswamy V., Jekabsons M. K., Johnson T. A., Sashidhara K. V., Crews P., Nagle D. G., Zhou Y.. The Marine Sponge Metabolite Mycothiazole: a Novel Prototype Mitochondrial Complex I Inhibitor. Bioorg. Med. Chem. 2010;18(16):5988–599. doi: 10.1016/j.bmc.2010.06.072. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Meyer K. J., Singh A. J., Cameron A., Tan A. S., Leahy D. C., O’Sullivan D., Joshi P., La Flamme A. C., Northcote P. T., Berridge M. V., Miller J. H.. Mitochondrial Genome-Knockout Cells Demonstrate a Dual Mechanism of Action for the Electron Transport Complex I Inhibitor Mycothiazole. Mar. Drugs. 2012;10:900. doi: 10.3390/md10040900. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Johnson T. A., Morris J. D., Coppage D. A., Cook C. V., Persi L. N., Ogarrio M. A., Garcia T. C., McIntosh N. L., McCauley E. P., Media J., Maheshwari M., Valeriote F. A., Shaw J., Crews P.. Reinvestigation of Mycothiazole Reveals the Penta-2,4-dien-1-ol Residue Imparts Picomolar Potency and 8S Configuration. ACS Med. Chem. Lett. 2020;11:108–113. doi: 10.1021/acsmedchemlett.9b00302. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Dutta N., Gerke J. A., Odron S. F., Morris J. D., Hruby A., Kim J., Torres T. C., Shemtov S. J., Clarke J. G., Chang M. C., Shaghasi H., Ray M. N., Averbukh M., Hoang S., Oorloff M., Alcala A., Vega M., Mehta H. H., Thorwald M. A., Crews P., Vermulst M., Garcia G., Johnson T. A., Higuchi-Sanabria R.. Investigating Impacts of the Mycothiazole Chemotype as a Chemical Probe for the Study of Mitochondrial Function and Aging. GeroScience. 2024;46(6):6009–6028. doi: 10.1007/s11357-024-01144-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Gerke J. A., Odron S. F., Kim J., Dutta N., Clarke J. G., Media J., Coppage D. A., Oorloff M., Alcala A., Garcia G., Kang M. E. F., Gerke C. L., Peterson J. C., Morris J. D., Higuchi-Sanabria R., Valeriote F. A., Crews P., Johnson T. A.. Further Probing the Properties of a Unique Sponge-derived Alkaloid Through the Isolation of a New (−)-(5E)-(8R)-(14Z)-Mycothiazole Analogue. J. Nat. Prod. 2024;87(10):2523–2529. doi: 10.1021/acs.jnatprod.4c00691. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Meerwein H., Hinz G., Hofmann P., Kroning E., Pfeil E.. Über tertiäre Oxoniumsalze I. J. Prakt. Chem. 1937;147:257. doi: 10.1002/prac.19371471001. [DOI] [Google Scholar]
  24. Valdez C. A., Salazar E. P., Leif R. N.. Trimethyloxonium-Mediated Methylation Strategies for the Rapid and Simultaneous Analysis of Chlorinated Phenols in Various Soils by Electron Impact Gas Chromatography-Mass Spectrometry. Sci. Rep. 2022;12:1401. doi: 10.1038/s41598-022-05463-w. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Hua D. H., Zhao H., Battina S. K., Lou K., Jimenez A. L., Desper J., Perchellet E. M., Perchellet J. P., Chiang P. K.. Total syntheses of (±)-ovalicin, C4­(S *)-isomer, and its C5-analogs and anti-trypanosomal activities. Bioorg. Med. Chem. 2008;16(9):5232–5246. doi: 10.1016/j.bmc.2008.03.009. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Hong S., Wang S., Cai H., Liu S.. Regiospecific Methylation of all the Hydroxyls in (+)-catechin by a Stepwise Differentiation Strategy. J. Sci. Food Agric. 2019;99(8):3785–3791. doi: 10.1002/jsfa.9594. [DOI] [PubMed] [Google Scholar]
  27. Amagata T., Johnson T. A., Cichewicz R. H., Tenney K., Mooberry S. L., Media J., Edelstein M., Valeriote F. A., Crews P.. Interrogating the Bioactive Pharmacophore of the Latrunculin Chemotype by Investigating the Metabolites of Two Taxonomically Unrelated Sponges. J. Med. Chem. 2008;51(22):7234–42. doi: 10.1021/jm8008585. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Korth H.-G., Trill H., Sustmann R.. [1–2H] Allyl Radical: Barrier to Rotation and Allyl Delocalization Energy. J. Am. Chem. Soc. 1981;103:4483–4489. doi: 10.1021/ja00405a032. [DOI] [Google Scholar]
  29. Li Z., Bally T., Houk K. N., Borden W. T.. Variations in Rotational Barriers of Allyl and Benzyl Cations, Anions, and Radicals. J. Org. Chem. 2016;81:9576–9584. doi: 10.1021/acs.joc.6b01530. [DOI] [PubMed] [Google Scholar]
  30. Dibble T. S., Sha Y., Thornton W. F., Zhang F.. Cis-Trans Isomerization of Chemically Activated 1-Methylallyl Radical and Fate of the Resulting 2-Buten-1-peroxy Radical. J. Phys. Chem. A. 2012;116:7603–7614. doi: 10.1021/jp303652x. [DOI] [PubMed] [Google Scholar]
  31. Watabe T., Tsubaki A., Isobe M., Ozawa N., Hiratsuka A.. A Mechanism for Epoxidation of Cholesterol by Hepatic Microsomal Lipid Hydroperoxides. Biochim. Biophys. Acta. 1984;795(1):60–66. [PubMed] [Google Scholar]
  32. Zhang Y., Lanjuin A., Chowdhury S. R., Mistry M., Silva-García C. G., Weir H. J., Lee C. L., Escoubas C. C., Tabakovic E., Mair W. B.. Neuronal TORC1Modulates Longevity via AMPK and Cell Nonautonomous Regulation of Mitochondrial Dynamics in C. elegans . eLife. 2019;8:e49158. doi: 10.7554/eLife.49158. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Kim, J. ; Dutta, N. ; Garcia, G. ; Higuchi-Sanabria, R. . Transcriptomic Analysis of Mitohormesis Associated with Lifespan Extension in Caenorhabditis elegans . GeroScience 2025. 10.1007/s11357-025-01912-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Bennett C. F., Vander Wende H., Simko M., Klum S., Barfield S., Choi H., Pineda V. V., Kaeberlein M.. Activation of the Mitochondrial Unfolded Protein Response does not Predict Longevity in Caenorhabditis elegans . Nature Comm. 2014;5:3483. doi: 10.1038/ncomms4483. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Xin N., Durieux J., Yang C., Wolff S., Kim H. E., Dillin A.. The UPRmt preserves mitochondrial import to extend lifespan. J. Cell Biol. 2022;221:e202201071. doi: 10.1083/jcb.202201071. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Byrne J. J., Soh M. S., Chandhok G., Vijayaraghavan T., Teoh J. S., Crawford S., Cobham A. E., Yapa N. M. B., Mirth C. K., Neumann B.. Disruption of Mitochondrial Dynamics Affects Behaviour and Lifespan in Caenorhabditis elegans. Cell. Mol. Life Sci. 2019;76:1967–1985. doi: 10.1007/s00018-019-03024-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Baruah A., Chang H., Hall M., Yuan J., Gordon S., Johnson E., Shtessel L. L., Yee C., Hekimi S., Derry W. B., Lee S. S.. CEP-1, the Caenorhabditis elegans p53 Homolog, Mediates Opposing Longevity Outcomes in Mitochondrial Electron Transport Chain Mutants. PLOS Genetics. 2014;10(2):e1004097. doi: 10.1371/journal.pgen.1004097. [DOI] [PMC free article] [PubMed] [Google Scholar]

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