scholarly journals Terpene Tail-to-Head Polycyclization Mediated by Small Molecule Catalysts: A Weakly-Coordinating Anion Approach

Author(s):  
Jessica Burch ◽  
Alex L. Bagdasarian ◽  
Tanin Hooshmand ◽  
Hosea Nelson

<p>Biomimetic total synthesis has played a pivotal role in the development of synthetic organic chemistry. In particular, efforts aimed at mimicking the head-to-tail (HT) cation–π cyclization cascades invoked in terpene biosynthesis, such as those catalyzed by type-II cyclases, have led to a multitude of new synthetic methods, chemical concepts, and total syntheses over the past century. Conversely, synthetic methodology that mimics tail-to-head (TH) cation–π cyclization cascades, mediated by Mg<sup>2+</sup> type-I terpene cyclases, remains elusive in organic synthesis, despite key roles in the biosynthesis of privileged therapeutic molecules such as taxol and artemesinin. Here we report that Li<sup>+</sup>/weakly-coordinating anion (WCA) salts catalyze the TH polycyclization of linaloyl fluoride, leading to high-yielding mixtures of polycyclic terpene natural products including cedrenes, cadinadiene, epizonarene, and 𝛿-selinene. The examples reported herein are the first small molecule-catalyzed TH polycyclization reactions enabling the shortest (formal) total synthesis of (<i>±</i>)-artemisinin. Moreover we apply this strategy to the diterpene geranyllinaloyl fluoride, resulting in a two-step total synthesis of the tricyclic core of the gersemiols (named here as <i>α</i>-gersemiene), a recently discovered class of marine diterpenoid natural products.</p>

2020 ◽  
Author(s):  
Jessica Burch ◽  
Alex L. Bagdasarian ◽  
Tanin Hooshmand ◽  
Hosea Nelson

<p>Biomimetic total synthesis has played a pivotal role in the development of synthetic organic chemistry. In particular, efforts aimed at mimicking the head-to-tail (HT) cation–π cyclization cascades invoked in terpene biosynthesis, such as those catalyzed by type-II cyclases, have led to a multitude of new synthetic methods, chemical concepts, and total syntheses over the past century. Conversely, synthetic methodology that mimics tail-to-head (TH) cation–π cyclization cascades, mediated by Mg<sup>2+</sup> type-I terpene cyclases, remains elusive in organic synthesis, despite key roles in the biosynthesis of privileged therapeutic molecules such as taxol and artemesinin. Here we report that Li<sup>+</sup>/weakly-coordinating anion (WCA) salts catalyze the TH polycyclization of linaloyl fluoride, leading to high-yielding mixtures of polycyclic terpene natural products including cedrenes, cadinadiene, epizonarene, and 𝛿-selinene. The examples reported herein are the first small molecule-catalyzed TH polycyclization reactions enabling the shortest (formal) total synthesis of (<i>±</i>)-artemisinin. Moreover we apply this strategy to the diterpene geranyllinaloyl fluoride, resulting in a two-step total synthesis of the tricyclic core of the gersemiols (named here as <i>α</i>-gersemiene), a recently discovered class of marine diterpenoid natural products.</p>


2020 ◽  
Author(s):  
Jessica Burch ◽  
Alex L. Bagdasarian ◽  
Tanin Hooshmand ◽  
Hosea Nelson

<p>Biomimetic total synthesis has played a pivotal role in the development of synthetic organic chemistry. In particular, efforts aimed at mimicking the head-to-tail (HT) cation–π cyclization cascades invoked in terpene biosynthesis, such as those catalyzed by type-II cyclases, have led to a multitude of new synthetic methods, chemical concepts, and total syntheses over the past century. Conversely, synthetic methodology that mimics tail-to-head (TH) cation–π cyclization cascades, mediated by Mg<sup>2+</sup> type-I terpene cyclases, remains elusive in organic synthesis, despite key roles in the biosynthesis of privileged therapeutic molecules such as taxol and artemesinin. Here we report that Li<sup>+</sup>/weakly-coordinating anion (WCA) salts catalyze the TH polycyclization of linaloyl fluoride, leading to high-yielding mixtures of polycyclic terpene natural products including cedrenes, cadinadiene, epizonarene, and 𝛿-selinene. The examples reported herein are the first small molecule-catalyzed TH polycyclization reactions enabling the shortest (formal) total synthesis of (<i>±</i>)-artemisinin. Moreover we apply this strategy to the diterpene geranyllinaloyl fluoride, resulting in a two-step total synthesis of the tricyclic core of the gersemiols (named here as <i>α</i>-gersemiene), a recently discovered class of marine diterpenoid natural products.</p>


Synlett ◽  
2018 ◽  
Vol 29 (12) ◽  
pp. 1552-1571 ◽  
Author(s):  
Jianxian Gong ◽  
Zhen Yang ◽  
Yueqing Gu ◽  
Ceheng Tan

This account describes our group’s latest research in the field of diversity-oriented synthesis of natural products via gold-catalyzed cascade reactions. We present two general strategies based on gold-catalyzed cycloisomerization: a gold-catalyzed cascade reaction of 1,7-diynes and a pinacol-terminated gold-catalyzed cascade reaction. We highlight our development of synthetic methods for the construction of biologically active natural products by using these two strategies.1 Introduction2 Gold-Catalyzed Cascade Reactions of 1,7-Diynes2.1 Collective Synthesis of C15 Oxygenated Drimane-Type Sesquiterpenoids2.2 Synthesis of Left-Wing Fragment of Azadirachtin I2.3 Collective Synthesis of Cladiellins3 Pinacol-Terminated Gold-Catalyzed Cascade Reaction3.1 Asymmetric Formal Total Synthesis of (+)-Cortistatins3.2 Total Synthesis of Orientalol F3.3 Asymmetric Total Synthesis of (–)-Farnesiferol C4 Summary and Outlook


2021 ◽  
Vol 22 (5) ◽  
pp. 2769
Author(s):  
Joonseong Hur ◽  
Jaebong Jang ◽  
Jaehoon Sim

γ-Butyrolactone, a five-membered lactone moiety, is one of the privileged structures of diverse natural products and biologically active small molecules. Because of their broad spectrum of biological and pharmacological activities, synthetic methods for γ-butyrolactones have received significant attention from synthetic and medicinal chemists for decades. Recently, new developments and improvements in traditional methods have been reported by considering synthetic efficiency, feasibility, and green chemistry. In this review, the pharmacological activities of natural and synthetic γ-butyrolactones are described, including their structures and bioassay methods. Mainly, we summarize recent advances, occurring during the past decade, in the construction of γ-butyrolactone classified based on the bond formation in γ-butyrolactone between (i) C5-O1 bond, (ii) C4-C5 and C2-O1 bonds, (iii) C3-C4 and C2-O1 bonds, (iv) C3-C4 and C5-O1 bonds, (v) C2-C3 and C2-O1 bonds, (vi) C3-C4 bond, and (vii) C2-O1 bond. In addition, the application to the total synthesis of natural products bearing γ-butyrolactone scaffolds is described.


2005 ◽  
Vol 77 (7) ◽  
pp. iv
Author(s):  
Tamejiro Hiyama

Organic synthesis has long played a pivotal role in the chemical sciences. It is therefore unsurprising and appropriate that the International Conferences on Organic Synthesis (ICOS) continue to thrive. This series was initiated by IUPAC in 1976 and has since featured biennially as one of the core events of the Union. What is surprising is that 22 years have elapsed since an ICOS event was last hosted by Japan. On that occasion, ICOS-4 was held in 1982 at Shinjuku, Tokyo, and was acclaimed as a great success. The latest event (ICOS-15), in Nagoya, Japan on 1ñ6 August 2004, offered an opportunity to match or surpass the impact of its predecessoróa challenge that was taken up enthusiastically under the leadership of Profs. Minoru Isobe (Nagoya University) and Hisashi Yamamoto (now at the University of Chicago) as Conference co-Chairs. Almost 1000 participants converged on Nagoya from all parts of the world. A noticeably high level of participation by delegates from East Asia in relation to those from North America and Europe attested to the growing capacity of this region to contribute to research at the forefront of this area of the chemical sciences. The scientific program of the Conference embraced all aspects of modern synthetic organic chemistry, inter alia, the invention of selective synthetic methods, asymmetric synthesis, total synthesis of natural products, design and synthesis of artificial agents for pharmaceutical and agricultural uses, and molecular assembly and materials based on molecular function. This topical breadth was also captured in a poster program, which was handsomely supported by no less than 466 displays on every conceivable facet of the subject. Overall, it is evident that organic synthesis has expanded its boundaries increasingly toward biological and material sciences, in response to the new challenges arising from rapid progress in molecular biology and applied physics during recent years.A lecture program comprising 10 plenary and 20 invited presentations, in addition to the Thieme/IUPAC award lecture and two Nagoya medal lectures, contributed to a truly exciting Conference experience, and the 21 speakers who kindly agreed to contribute papers based upon their presentations have made it possible to capture some of the excitement in this issue of Pure and Applied Chemistry. The Nagoya Gold Medallist, J. F. Stoddart, used the occasion to share an absorbing and very personal perspective on molecular assembly and materials, a theme on which M. Fujita also disclosed new insights and developments. The perennial theme of total synthesis of natural products, provided scope for presentation of highly creative accomplishments by S. Ley, J. Cossy, Y. Langlois, R. Pilli, and S. Kozmin on a variety of challenging targets. Such advances in the total synthesis of biologically active natural products having extremely complex structures, often necessitate development of novel synthetic methods, and H. Overkleeft, P. Chiu, V. Nair, T.-P. Loh, S. Martin, T.-Y. Luh, E. Juaristi, and M. Catellani did justice to this theme with presentations on a variety of extremely elegant and sophisticated new developments in methodology, based upon organometallic catalysts and/or reagents. Finally, the broad theme of asymmetric synthesis using organometallic complexes with chiral ligands or chiral organocatalysts was developed in conjunction with combinatorial methodology, which is shown to be highly effective in optimizing catalytic systems. Those who contributed to the topic of asymmetric synthesis are K. Ding, A. Charette, S. H. Kang, A. Berkessel, and K. Maruoka, the recipient of the Nagoya Silver Medal.What is the future of organic synthesis? The invention of unprecedented drugs and materials has enriched and expanded the horizons of the human experience in formerly unimagined ways, and owes much to the ever increasing ingenuity of organic synthesis, and recognition and attainment of new synthetic targets. The impact of organic synthesis on cognate disciplines and on general advancement of science and technology is definitely enormous and will be further strengthened by future challenges and opportunities. Thus, it is hoped that younger generations will be inspired to participate in tapping this rich potential, in the cause of advancing science and contributing to the enrichment of future life. These aspirations may yield incalculable rewards. Such progress will certainly be reflected in the scientific program of the next Conference in the ICOS series, which will take place in Merida, Yucatan, Mexico on 11ñ15 June 2006, under the chairmanship of Dr. Eusebio Juaristi, Instituto Politecnico Nacional, Mexico.Tamejiro HiyamaConference EditorDepartment of Material ChemistryKyoto University, Kyoto, Japan *An issue of reviews and research papers based on lectures presented at the 15th International Conference on Organic Synthesis (ICOS-15), held in Nagoya, Japan, 1-6 August 2004, on the theme of organic synthesis. Other presentations are published in this issue, pp. 1087-1296.


Synthesis ◽  
2017 ◽  
Vol 49 (22) ◽  
pp. 4899-4916 ◽  
Author(s):  
Rongbiao Tong ◽  
Zhihong Zhang

Being different from 2,6-cis-tetrahydropyrans (2,6-cis-THPs), the corresponding 2,6-trans-THPs are thermodynamically less stable and more challenging to construct. The fact that there are many natural products and/or bioactive molecules containing this 2,6-trans-THP subunit has led to the development of many efficient synthetic approaches to access 2,6-trans-THPs. This review summarizes various synthetic methods reported for this structural motif and/or related applications in the total synthesis of natural products.1 Introduction2 Nucleophilic Addition to an Oxocarbenium Ion (Strategy A)3 Intramolecular Oxa-Michael Addition (Strategy B)4 Intermolecular Michael Addition to Dihydropyranones (Strategy A)5 The Heck–Matsuda (Strategy A) Reaction and Oxa-Heck Cyclization (Strategy B)6 Intramolecular SN2 Substitution and Epoxide Opening (Strategy B)7 Miscellaneous Methods8 Conclusion and Outlook


Synthesis ◽  
2020 ◽  
Vol 52 (21) ◽  
pp. 3111-3128
Author(s):  
Alejandro Cordero-Vargas ◽  
Jeferson B. Mateus-Ruiz

In the last two decades, the field of photoredox catalysis (PRC) has grown impressively with reports of new synthetic methodologies and more efficient versions of known free-radical reactions. The impressive success of visible-light-mediated photoredox catalysis is, in great part, due to its low environmental impact, mild reaction conditions, clean reactions, and inexpensive methodologies. These features have allowed photoredox catalysis to emerge as a powerful tool in the synthesis of natural products; much excellent work was reported between 2011 and 2015. Since 2016, a number of more efficient and impressive total syntheses of natural products featuring photoredox catalysis have been reported. In this review, we summarize the recent synthetic applications of photoredox catalysis in the total synthesis of natural products between 2016 and 2020.1 Introduction2 Intermolecular Additions from Functionalized Substrates2.1 Intermolecular Additions from Alkyl Halides2.2 Intermolecular Additions from Alcohols and Carboxylic Acids3 Cyclizations from Functionalized Substrates3.1 Cyclizations of Carbon-Centered Radicals3.2 Cyclizations of Nitrogen-Centered Radicals4 Intramolecular Cyclization from Non-functionalized N–H Bonds4.1 Type I Radical Cascade4.2 Type II Radical Cascade4.3 Type III Radical Cascade5 Functionalization of Imines and Enamines6 Cycloadditions7 Miscellaneous7.1 Dehalogenation and Reductive Decarboxylation7.2 Thiyl Radical Promoted Cascade8 Conclusions and Perspectives


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