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Erich Hecker - One of the best experts on this subject based on the ideXlab platform.
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Dietary cancer risk from conditional cancerogens (tumor promoters) in produce of livestock fed on species of spurge (Euphorbiaceae). V. Skin irriitant and tumor-promoting diterpene ester toxins of the Tigliane and ingenane type in the herbs Euphorbia
Journal of cancer research and clinical oncology, 2001Co-Authors: Salah M. A. D. Zayed, Madiha Farghaly, Soliman M. Soliman, Hubert Gotta, Bernd L. Sorg, Erich HeckerAbstract:Irritant diterpene ester toxins were isolated from Euphorbia nubica and E. helioscopia, which are contaminants of the green fodder of livestock in Egypt. Fractionations of methanol extracts of aerial parts of both plants were monitored by the irritation unit on the mouse ear. Plant extracts were subjected to multiplicative distribution methods, yielding irritant hydrophilic fractions that were further purified by column chromatography. Final purification of the materials was achieved by TLC (silica gel) followed by HPLC, or by TLC alone. In this way, from E. nubica, five Euphorbia factors (Nu1-Nu5) were isolated and characterized as short-chain polyfunctional diterpene esters of Tigliane-type parent alcohols. The two weak irritants Nul and Nu3 were triesters of 4-deoxy(4alpha)phorbol. Nu2 was shown to be a triester of the stereoisomeric Tigliane-type parent alcohol 4-deoxyphorbol. Weak irritant Nu4 probably is a positional isomer of Nu2. Nu5 was characterized as a short-chain triester of 4,20-dideoxy-5xi-hydroxyphorbol. From E. helioscopia, six short- to medium-chain polyfunctional diterpene esters of the ingenane type, generally containing unsaturated acids were obtained, i.e., four irritant esters of ingenol (Euphorbia factors H1, H2, H5, and H6) and two esters of 20-deoxyingenol (non-irritant Euphorbia substance HS4, and irritant Euphorbia factor H8). All irritant Euphorbia factors of the Tigliane and ingenane diterpene ester type described in this investigation are considered to be more or less active tumor promoters, i.e., conditional (non-genotoxic) cancerogens. The Euphorbia factors assayed exhibited moderate (H1) to low (H8) relative tumor-promoting potency in comparison to the ingenane prototype DTE tumor promoter 3-TI.
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Dietary cancer risk from conditional cancerogens (tumor promoters) in produce of livestock fed on species of spurge (Euphorbiaceae)
Journal of Cancer Research and Clinical Oncology, 2001Co-Authors: Salah M. A. D. Zayed, Madiha Farghaly, Soliman M. Soliman, Hubert Gotta, Bernd Sorg, Erich HeckerAbstract:Irritant diterpene ester toxins were isolated from Euphorbia nubica and E. helioscopia , which are contaminants of the green fodder of livestock in Egypt. Fractionations of methanol extracts of aerial parts of both plants were monitored by the irritation unit on the mouse ear. Plant extracts were subjected to multiplicative distribution methods, yielding irritant hydrophilic fractions that were further purified by column chromatography. Final purification of the materials was achieved by TLC (silica gel) followed by HPLC, or by TLC alone. In this way, from E. nubica , five Euphorbia factors (Nu1–Nu5) were isolated and characterized as short-chain polyfunctional diterpene esters of Tigliane-type parent alcohols. The two weak irritants Nu1 and Nu3 were triesters of 4-deoxy(4α)phorbol. Nu2 was shown to be a triester of the stereoisomeric Tigliane-type parent alcohol 4-deoxyphorbol. Weak irritant Nu4 probably is a positional isomer of Nu2. Nu5 was characterized as a short-chain triester of 4,20-dideoxy-5ξ-hydroxyphorbol. From E. helioscopia , six short- to medium-chain polyfunctional diterpene esters of the ingenane type, generally containing unsaturated acids were obtained, i.e., four irritant esters of ingenol ( Euphorbia factors H1, H2, H5, and H6) and two esters of 20-deoxyingenol (non-irritant Euphorbia substance HS4, and irritant Euphorbia factor H8). All irritant Euphorbia factors of the Tigliane and ingenane diterpene ester type described in this investigation are considered to be more or less active tumor promoters, i.e., conditional (non-genotoxic) cancerogens. The Euphorbia factors assayed exhibited moderate (H1) to low (H8) relative tumor-promoting potency in comparison to the ingenane prototype DTE tumor promoter 3-TI.
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Structure/Activity Relationships of Polyfunctional Diterpenes of the Tigliane Type
European journal of biochemistry, 1996Co-Authors: Goetz Krauter, Claus-w. Von Der Lieth, Rainer Schmidt, Erich HeckerAbstract:For protein kinase C (PKC), a family of isoenzymes with serine/threonine-kinase activity identified as the major cellular receptor for certain skin irritants and tumor promoters, a new pharmacophore model is presented. By structure/activity relationship studies of naturally occurring and synthetic diterpene esters of the Tigliane type (PKC activators) it is demonstrated that in addition to the oxygen at C20 it is the O-acyl function in position C13 which is critically essential for skin-irritant and tumor-promoting bioactivities rather than other oxygen atoms. This result is confirmed and extended by computer-assisted molecular modeling of Tigliane-type and ingenane-type tumor promoters. It is contrasted to certain features attributed to the pharmacophore based upon the recently determined crystallographic structure of the effector-binding domain Cys2 of PKCδ complexed with the pseudo-agonist phorbol 13-acetate.
Zhi Liu - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of Prostratin, a Bioactive Tigliane Diterpenoid: Access to Multi-Stereocenter Cyclohexanes from a Phenol
The Journal of organic chemistry, 2020Co-Authors: Guanghu Tong, Zhengwei Ding, Zhi Liu, You-song Ding, Hailong ZhangAbstract:Tiglianes such as prostratin and related diterpenoids are biologically significant natural molecules and long-standing targets for organic synthesis community. Due to the complex polycyclic scaffol...
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Facile synthesis of the daphnane and Tigliane framework by semi-flow tube-based-bubbling photooxidation and diastereoselective conjugate addition
Organic Chemistry Frontiers, 2020Co-Authors: Zhengwei Ding, Guanghu Tong, Zhi Liu, Yueyun Bao, Zhouhang Lei, Hailong ZhangAbstract:The universal [5-7-6] tricyclic framework of Tigliane and daphnane diterpenes containing five contiguous stereocenters has been synthesized in 9 steps from readily available starting materials in a completely stereocontrolled manner. This was enabled by designing a semi-flow tube-based bubbling photoreaction setup for an efficient oxidative dearomatization and by devising an open chain remote group-assisted selective 1,4-addition. The results provide a potentially rapid and divergent approach to synthesize various related diterpene molecules.
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Stereocontrolled construction of the tricyclic framework of Tiglianes and daphnanes by an oxidative dearomatization approach.
Organic letters, 2014Co-Authors: Guanghu Tong, Zhi LiuAbstract:An appropriately functionalized [5–7–6] tricyclic framework of Tigliane and daphnane diterpenes containing seven contiguous stereocenters has been prepared in 10 steps from very simple building blocks in a modular and stereocontrolled fashion. The key features of this approach involve an efficient visible light-induced singlet oxygen oxidative dearomatization and an array of substrate-controlled highly diastereoselective transformations. This work provides a model strategy for rapid and diverted synthesis of natural and unnatural molecules sharing the common skeleton.
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Stereocontrolled Construction of the Tricyclic Framework of Tiglianes and Daphnanes by an Oxidative Dearomatization Approach
2014Co-Authors: Guanghu Tong, Zhi LiuAbstract:An appropriately functionalized [5–7–6] tricyclic framework of Tigliane and daphnane diterpenes containing seven contiguous stereocenters has been prepared in 10 steps from very simple building blocks in a modular and stereocontrolled fashion. The key features of this approach involve an efficient visible light-induced singlet oxygen oxidative dearomatization and an array of substrate-controlled highly diastereoselective transformations. This work provides a model strategy for rapid and diverted synthesis of natural and unnatural molecules sharing the common skeleton
Goetz Krauter - One of the best experts on this subject based on the ideXlab platform.
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Structure/Activity Relationships of Polyfunctional Diterpenes of the Tigliane Type
European journal of biochemistry, 1996Co-Authors: Goetz Krauter, Claus-w. Von Der Lieth, Rainer Schmidt, Erich HeckerAbstract:For protein kinase C (PKC), a family of isoenzymes with serine/threonine-kinase activity identified as the major cellular receptor for certain skin irritants and tumor promoters, a new pharmacophore model is presented. By structure/activity relationship studies of naturally occurring and synthetic diterpene esters of the Tigliane type (PKC activators) it is demonstrated that in addition to the oxygen at C20 it is the O-acyl function in position C13 which is critically essential for skin-irritant and tumor-promoting bioactivities rather than other oxygen atoms. This result is confirmed and extended by computer-assisted molecular modeling of Tigliane-type and ingenane-type tumor promoters. It is contrasted to certain features attributed to the pharmacophore based upon the recently determined crystallographic structure of the effector-binding domain Cys2 of PKCδ complexed with the pseudo-agonist phorbol 13-acetate.
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structure activity relationships of polyfunctional diterpenes of the Tigliane type
FEBS Journal, 1996Co-Authors: Goetz Krauter, Claus-w. Von Der Lieth, Rainer Schmidt, E. HeckerAbstract:For protein kinase C (PKC), a family of isoenzymes with serine/threonine-kinase activity identified as the major cellular receptor for certain skin irritants and tumor promoters, a new pharmacophore model is presented. By structure/activity relationship studies of naturally occurring and synthetic diterpene esters of the Tigliane type (PKC activators) it is demonstrated that in addition to the oxygen at C20 it is the O-acyl function in position C13 which is critically essential for skin-irritant and tumor-promoting bioactivities rather than other oxygen atoms. This result is confirmed and extended by computer-assisted molecular modeling of Tigliane-type and ingenane-type tumor promoters. It is contrasted to certain features attributed to the pharmacophore based upon the recently determined crystallographic structure of the effector-binding domain Cys2 of PKCδ complexed with the pseudo-agonist phorbol 13-acetate.
Guanghu Tong - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of Prostratin, a Bioactive Tigliane Diterpenoid: Access to Multi-Stereocenter Cyclohexanes from a Phenol
The Journal of organic chemistry, 2020Co-Authors: Guanghu Tong, Zhengwei Ding, Zhi Liu, You-song Ding, Hailong ZhangAbstract:Tiglianes such as prostratin and related diterpenoids are biologically significant natural molecules and long-standing targets for organic synthesis community. Due to the complex polycyclic scaffol...
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Facile synthesis of the daphnane and Tigliane framework by semi-flow tube-based-bubbling photooxidation and diastereoselective conjugate addition
Organic Chemistry Frontiers, 2020Co-Authors: Zhengwei Ding, Guanghu Tong, Zhi Liu, Yueyun Bao, Zhouhang Lei, Hailong ZhangAbstract:The universal [5-7-6] tricyclic framework of Tigliane and daphnane diterpenes containing five contiguous stereocenters has been synthesized in 9 steps from readily available starting materials in a completely stereocontrolled manner. This was enabled by designing a semi-flow tube-based bubbling photoreaction setup for an efficient oxidative dearomatization and by devising an open chain remote group-assisted selective 1,4-addition. The results provide a potentially rapid and divergent approach to synthesize various related diterpene molecules.
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Stereocontrolled construction of the tricyclic framework of Tiglianes and daphnanes by an oxidative dearomatization approach.
Organic letters, 2014Co-Authors: Guanghu Tong, Zhi LiuAbstract:An appropriately functionalized [5–7–6] tricyclic framework of Tigliane and daphnane diterpenes containing seven contiguous stereocenters has been prepared in 10 steps from very simple building blocks in a modular and stereocontrolled fashion. The key features of this approach involve an efficient visible light-induced singlet oxygen oxidative dearomatization and an array of substrate-controlled highly diastereoselective transformations. This work provides a model strategy for rapid and diverted synthesis of natural and unnatural molecules sharing the common skeleton.
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Stereocontrolled Construction of the Tricyclic Framework of Tiglianes and Daphnanes by an Oxidative Dearomatization Approach
2014Co-Authors: Guanghu Tong, Zhi LiuAbstract:An appropriately functionalized [5–7–6] tricyclic framework of Tigliane and daphnane diterpenes containing seven contiguous stereocenters has been prepared in 10 steps from very simple building blocks in a modular and stereocontrolled fashion. The key features of this approach involve an efficient visible light-induced singlet oxygen oxidative dearomatization and an array of substrate-controlled highly diastereoselective transformations. This work provides a model strategy for rapid and diverted synthesis of natural and unnatural molecules sharing the common skeleton
David A Evans - One of the best experts on this subject based on the ideXlab platform.
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approach to the tricyclic core of the Tigliane daphnane diterpenes concerning the utility of transannular aldol additions
Organic Letters, 2013Co-Authors: Arthur J Catino, Alexandra Sherlock, Peyton Shieh, Joseph S Wzorek, David A EvansAbstract:Two transannular (TA) aldol reactions were used to assemble the tricyclic carbon skeleton found in the Tigliane and daphnane classes of diterpene natural products.
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Approach to the Tricyclic Core of the Tigliane–Daphnane Diterpenes. Concerning the Utility of Transannular Aldol Additions
2013Co-Authors: Arthur J Catino, Alexandra Sherlock, Peyton Shieh, Joseph S Wzorek, David A EvansAbstract:Two transannular (TA) aldol reactions were used to assemble the tricyclic carbon skeleton found in the Tigliane and daphnane classes of diterpene natural products