A category of highly fused diterpenoid natural products possessing a characteristic perhydropyrene-like or rearranged tetracyclic skeleton structure are distributed in different life forms.Compared to traditional poly...A category of highly fused diterpenoid natural products possessing a characteristic perhydropyrene-like or rearranged tetracyclic skeleton structure are distributed in different life forms.Compared to traditional polycyclic diterpenoids,their biosynthetic pathways are quite unique and diverse.Chemists have pinpointed a range of this type of unusual diterpenoids:cycloamphilectanes and isocycloamphilectanes,kempenes and rippertanes,hydropyrene and hydropyrenol,along with recently disclosed cephalotanes.This review describes developments in this field and discusses the challenges associated with synthesizing this class of highly complex compounds.展开更多
The northern South China Sea,including the Zhujiangkou Basin and the Beibuwan Basin,developed high-quality lacustrine source rocks during the Eocene rifting period.These source rocks are vital for hydrocarbon generati...The northern South China Sea,including the Zhujiangkou Basin and the Beibuwan Basin,developed high-quality lacustrine source rocks during the Eocene rifting period.These source rocks are vital for hydrocarbon generation in the northern South China Sea.The ZhuⅠdepression in the Zhujiangkou Basin and the Beibuwan Basin typically exhibit high abundance of C_(30)4-methyl steranes.However,shales in the Eocene Wenchang Formation in the ZhuⅢdepression of the Zhujiangkou Basin contains lower quantities of high-quality lacustrine source rocks with 4-methyl steranes,which often co-elute with some pentacyclic triterpanes in gas chromatography-mass spectrometry(GC-MS).Therefore,the single 4-methylsterane parameter based on GC-MS cannot accurately distinguish organic source in the deep to semi-deep water lacustrine source rocks of the Wenchang Formation from other source rocks,thus impeding the recognition of their contributions to petroleum reservoirs.In this study,GC-MS of aliphatic hydrocarbons,palynofacies and algal identification,as well as stable carbon isotope data of organic matter were used to identify the algal species and construct the paleoclimate during deposition of the Wenchang Formation source rocks in the ZhuⅢdepression of the Zhujiangkou Basin.It is suggested that during the Wenchang Formation period,freshwater green algae prevailed in the lake,which is likely account for the relatively low content of 4-methyl steranes in the high-quality lacustrine source rocks.Controlled by the algal species,it is proposed that the content of C_(30)tetracyclic polyprenoids(TPP)can better indicate the quality of the Wenchang source rocks than C_(30)4-methyl steranes.Consequently,a relationship between the TPP index and the quality of the lacustrine source rocks in the Wenchang Formation of the ZhuⅢdepression was established.A higher TPP index indicates higher organic matter abundance and hydrogen index of the lacustrine source rocks.When applied to the origin analysis of oils in the ZhuⅢdepression,it is believed that the organic-rich deep lacustrine source rocks in the Wenchang Formation made great contribution to the transitional zone crude oils in the Wenchang A and Wenchang B depressions.展开更多
Salvianolic acid G,a caffeic acid dimer with a novel tetracyclic skeleton was isolated from the roots of Salvia miltiorrhiza.Its structure was elucidated by chemical and spectral analysis,especially by 2D NMR analysis.
Novel tetracyclic terpanes X and Y namely C24-des-A-oleanane and C27 tetracyclic terpane were detected in crude oils and source rock extracts in Zhu 1 depression in Pearl River Mouth Basin by GC-MS analysis technology...Novel tetracyclic terpanes X and Y namely C24-des-A-oleanane and C27 tetracyclic terpane were detected in crude oils and source rock extracts in Zhu 1 depression in Pearl River Mouth Basin by GC-MS analysis technology. These compounds are similar to oleanane in the structure, and their relative abundance in m/z 191 partial mass cbromatogram has a good correlation with oleanane. Here compounds X and Y are considered to be derived from the des-A degradation of oleanoid precursor. The ratio of X/（X-I-C24） and Y/（Y-I-C24） increase with the increasing inputs of terrigenous organic matter in crude oils. Wenchang Formation middle-deep lacustrine source rocks with planktonic algae organic matter inputs and oil generating from it contain low abundance of compounds X and Y, while Enping Formation coal measures source rocks with terrigenous higher plants organic matter inputs and oil generating from it usually have higher compounds X and Y. In general when two terrigenous compounds C19 tricyclic terpane and bicadinane-T are high in crude oils, there are also a corresponding high abundant compounds X and Y. Relative abundance of compounds X and Y is closely related to the source of organic matter and it can indicate the input of terrigenous organic matter.展开更多
C_(24)tetracyclic terpanes are common compounds in source rocks and crude oils,and C_(24)17,21-secohopane is the most common and widely used source-related indicator.In this study,three unusual C_(24)tetracyclic terpa...C_(24)tetracyclic terpanes are common compounds in source rocks and crude oils,and C_(24)17,21-secohopane is the most common and widely used source-related indicator.In this study,three unusual C_(24)tetracyclic terpanes were detected on the m/z 191 chromatogram of saturated hydrocarbons in the Shahejie Formation source rocks in the Bozhong subbasin.Based on the mass spectra characteristics,diagnostic ion fragments,retention time and comparisons with published literature,three unusual C_(24)tetracyclic terpanes were identified as 10β(H)-des-A-oleanane,10β(H)-des-A-lupane and C_(24)des-Ahopane.To the best of our knowledge,this is the first study to detect and publicly report these three compounds in source rock samples from the Shahejie Formation of the Bozhong subbasin,Bohai Bay Basin.The results indicated that 10β(H)-des-A-oleanane and 10β(H)-des-A-lupane likely originated from terre strial angiosperms,while C_(24)des-A-hopane likely originated fro m prokaryotic o rganisms.Te rrestrial angiosperms provide the material basis for the generation of compounds A and B,and the distribution and concentration of these two compounds are affected by thermal maturity.In the low maturity stage(0.5%<R_(0)<0.7%),compounds A and B are relatively enriched in the source rocks.展开更多
Tricyclic and tetracyclic terpanes are important constituents of crude oil and source rock extracts.However,they have not been reported in the Offshore Niger Delta Basin,Nigeria.Thus,the present study investigated the...Tricyclic and tetracyclic terpanes are important constituents of crude oil and source rock extracts.However,they have not been reported in the Offshore Niger Delta Basin,Nigeria.Thus,the present study investigated the geochemical significance of tricyclic and tetracyclic terpanes in source rock extracts from the Offshore Niger Delta Bain,Nigeria with gas chromatography-mass spectrometry(GC-MS).The total relative abundances of tricyclic terpanes,C_(19)TT-C_(21)TT,and C_(23) TT in the rock samples ranged from 82.50 to 96.37%,50.08 to 74.17%,and 25.83 to 49.92%,respectively.These values showed the source rocks were formed from a mixed origin(terrestrial and marine).Among the tricyclic and tetracyclic terpanes identified in the rock extracts,the conventional(C_(20)TT,C_(23)TT,C_(24)TT,C_(24)TeT)and recent(Y1,X1,Z1)were more prominent than all others,indicating mixed input of terrigenous and marine organic matter.The C_(24)TT/C_(23)TT,C_(24)TeT/(C_(24)TeT+C_(26)TT),C_(19)TT/C_(23)TT,C_(20)TT/C_(23)TT,C_(25)TT/C_(24)TeT,C_(25)TT/C_(26)TT,C_(19)TT/C_(20)TT,C_(24)TeT/C_(26)TT,Z1/(Z1+C_(24)TT),and Y1/(Y1+C_(24)TT)in the rock samples range from 0.33 to 1.30,0.76 to 0.90,0.18 to 0.73,0.34 to 1.05,0.33 to 1.74,0.30 to 1.39,0.31 to0.89,1.66 to 4.33,0.36 to 0.83,and 0.34 to 0.79,respectively.These values further showed that the rock samples were formed from mixed input of terrigenous and marine organic matter and deposited under oxic to suboxic conditions in lacustrine-fluvial/deltaic environments.Also,the C_(24)TeT/C_(20)-26TT,C_(24)TeT/C_(30)HOP,and C_(23)TT/C_(30)HOP ranged from 0.16 to 0.45,0.02 to 0.42,and 0.01 to 0.48,respectively.This range of values suggests that source rocks were within immature to early mature stage.Thus,this study showed that tricyclic and tetracyclic terpanes were effective in determining the origin,depositional environments,and thermal maturity of source rocks in the Niger Delta Basin,Nigeria.展开更多
Four new taxane diterpenoids were isolated from the bark of Taxus yunnanensis.Their structures were elucidated as the new skeleton with 5/7/6/4 membered rings by spectral analysis and 2D NMR shift correlation experime...Four new taxane diterpenoids were isolated from the bark of Taxus yunnanensis.Their structures were elucidated as the new skeleton with 5/7/6/4 membered rings by spectral analysis and 2D NMR shift correlation experiments.展开更多
Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacolog‐ical activities.However,a direct stereoselective method from simple and readily‐made coumarins derivatives remains chall...Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacolog‐ical activities.However,a direct stereoselective method from simple and readily‐made coumarins derivatives remains challenging due to the inertness of coumarins as dienophiles.Herein,we de‐velop a decarboxylative asymmetric[4+2]cycloaddition of 3‐cyanocoumarins with vinyl benzoxa‐zinones,affording the coumarin‐derived condensed rings bearing three continuous stereocenters in high yields with excellent diastereoselectivities(>20/1 d.r.)and enantioselectivities(up to 99%ee).This direct enantioselective reaction was achieved by a Pd(0)/Cu(I)bimetallic catalytic system.The mechanism studies indicated that the synergistic activation effect,in which chiral Cu(I)as an availa‐ble Lewis acid catalyst activates 3‐cyanocoumarin and chiral Pd(0)complex activates benzoxazi‐none by the formation ofπ‐allyl‐palladium intermediate,plays an important role on the stereoselec‐tive control.The current work provides a new activation modes of Cu catalyst in the Pd/Cu bimetal‐lic catalytic system.展开更多
Two new tetracyclic taxane diterpenoids----yunnanxol(1) and yunnanxamine(2)have been isolated from the bark of Taxus yunnanensis Cheng et L.K.Fu.Their structures have been established from the spectral data,mainly fro...Two new tetracyclic taxane diterpenoids----yunnanxol(1) and yunnanxamine(2)have been isolated from the bark of Taxus yunnanensis Cheng et L.K.Fu.Their structures have been established from the spectral data,mainly from MS,highfield ~1H NMR,~1H-~1H COSY, ^(13)C NMR,^(13)C-~1H COSY and ^(13)C-~1H COLOC spectroscopies.展开更多
A new skeleton taxane diterpene,taxayuntin,was isolated from the leaves and stems of Taxus yunnanensis.Its structure was determined by spectroscopic methods(MS,~1H NMR,^(13)C NMR, ~1H-~1H COSY,~1H-^(13)C COSY and ^(13...A new skeleton taxane diterpene,taxayuntin,was isolated from the leaves and stems of Taxus yunnanensis.Its structure was determined by spectroscopic methods(MS,~1H NMR,^(13)C NMR, ~1H-~1H COSY,~1H-^(13)C COSY and ^(13)C-~1H COLOC)and X-ray diffraction.展开更多
The key intermediate 5 for synthesis of the contragestationally active diterpenoid grandiflorenic acid(1)and its analogues 2 and 3 was prepared and an acetyl transposition reaction occurred in the SeO_2 oxida- tion of 8.
Let be a graph with n vertices and m edges. The sum of absolute value of all coefficients of matching polynomial is called Hosoya index. In this paper, we determine 2<sup>nd</sup> to 4<sup>th</sup...Let be a graph with n vertices and m edges. The sum of absolute value of all coefficients of matching polynomial is called Hosoya index. In this paper, we determine 2<sup>nd</sup> to 4<sup>th</sup> minimum Hosoya index of a kind of tetracyclic graph, with m = n +3.展开更多
Atisane diterpenes are biologically interesting natural products. We report here a convergent approach to construct the tetracyclic core of the atisane skeleton. The two segments were assembled through a Wittig reacti...Atisane diterpenes are biologically interesting natural products. We report here a convergent approach to construct the tetracyclic core of the atisane skeleton. The two segments were assembled through a Wittig reaction, while an intramolecular Aldol condensation served as the key step to furnish the tetracyclic skeleton.展开更多
Objective: To isolate bioactive compounds from the endophytic fungus Fusarium sporotrichioides isolated from Rauwolfia yunnanensis, and investigate their pharmacological activities.Methods: The chemical constituents w...Objective: To isolate bioactive compounds from the endophytic fungus Fusarium sporotrichioides isolated from Rauwolfia yunnanensis, and investigate their pharmacological activities.Methods: The chemical constituents were isolated and purified by combining with ODS column chromatography, silica gel column chromatography and by performing semipreparative HPLC. Their structures were established on the basis of 1D NMR(1H-NMR and13C-NMR) and 2D NMR(1H–1H COSY,HSQC, HMBC and NOESY), as well as HRESIMS and comparison with literature data. In addition, the absolute configuration of compound 1 was determined by calculated ECD data.Results: One previously undescribed tetracyclic triterpenoid derivative, named as integracide L(1), 12aacetoxy-4,4-dimethyl-24-methylene-5a-cholesta-8,14-diene-2a,3β,11β-triol(2), 12a-acetoxy-4,4-dime thyl-24-methylene-5a-cholesta-8-momoene-2a,3β,11β-triol(3), 12a-acetoxy-4,4-dimethyl-24-methy lene-5a-cholesta-8,14-diene-3β,11β-triol(4), and 12a-acetoxy-4,4-dimethyl-24-methylene-5acholesta-8-momoene-3β,11β-triol(5) were isolated from F. sporotrichioide. Moreover, compound 1 was rare tetracyclic triterpenoid with single methyl replacement at C-4 position.Conclusion: Compound 1 was a new tetracyclic triterpenoid isolated from the endophytic fungus F.sporotrichioides. In addition, compound 2 could inhibit the growth of three different human cancer cells significantly. Compounds 3 and 5 were found to possess better cytotoxic activities on Hep G-2 cells than the other compounds, with IC50values of(2.8 ± 0.1) and(6.3 ± 0.3) μmol/L respectively.展开更多
A series of novel tetracyclic triterpanes based on the lanostane skeleton, ranging in cars-bon number from C_(30) to C_(32), were identified for the first time in Eocene lacustrine depo-its of Biyang Depression, China...A series of novel tetracyclic triterpanes based on the lanostane skeleton, ranging in cars-bon number from C_(30) to C_(32), were identified for the first time in Eocene lacustrine depo-its of Biyang Depression, China. These compounds have been identified by GC, GC- MS, andcoinjection with authentic standard, as 8β(H), 9α(H)- lanostane (C_(30)), 24-methyl- lanostane(C_(31)) and 24- ethyl- lanostane (C_(32)). Mechanisms are proposed for the origin and geologicalfate of these compounds. To the best of our knowledge, this is the first confirmed occur-rence of lanostanes in the sedimentary record.展开更多
Grandiflorenic acid(1),possessing potent contragestational activity,is an ent-kauranediterpenoid.It has been isolated from Mexical medicinal plant zoapatle(Montanoa tomento)In connection with our synthetic work on ent...Grandiflorenic acid(1),possessing potent contragestational activity,is an ent-kauranediterpenoid.It has been isolated from Mexical medicinal plant zoapatle(Montanoa tomento)In connection with our synthetic work on ent-kaurane diterpenoids,we are interested in theconversion of stevioside(2)occurred abundantly in Stevia rebaudiana into grandiflorenic acid展开更多
Due to the high electrophilic nature of azo-dienophiles, azo-Diels–Alder proceeds rapidly even without the need of a catalyst and is therefore regarded as the “click reaction”. This spontaneity causes strong backgr...Due to the high electrophilic nature of azo-dienophiles, azo-Diels–Alder proceeds rapidly even without the need of a catalyst and is therefore regarded as the “click reaction”. This spontaneity causes strong background reaction and poses a daunting challenge to chemists for developing the catalytic asymmetric version. Reported herein is the first catalytic asymmetric dearomative azo-Diels–Alder reaction between2-vinylindoles and triazoledione. This protocol makes use of the high energy barrier of dearomatization to avert the strong background reaction of azo-Diels–Alder reaction, allowing the implementation of the projected reaction at ambient temperature. Density functional theory calculations have been performed to gain insights into the reaction mechanism and the origins of the enantioselectivity. By using this method,a variety of tetracyclic indole derivatives have been readily prepared in good to excellent yields and with excellent diastereo-and enantio–selectivities(33 examples, up to 97% yield and >99% ee, >20:1 dr).展开更多
Devonian cutinitic liptobiolith is a special type of coal formed during the early evolutionary stage of land plants.The Baishaping and Damaidi Devonian coals are notable for their distinct papery,sheet-like texture,an...Devonian cutinitic liptobiolith is a special type of coal formed during the early evolutionary stage of land plants.The Baishaping and Damaidi Devonian coals are notable for their distinct papery,sheet-like texture,and unusually high cutinite content(>50%),belonging to typical cutinitic liptobiolith.They are bituminous coals and have a suppressed vitrinite reflectance.Compared with typical typeⅢkerogen,these liptobioliths are characterized by extremely high yields of volatile matter and high hydrogen contents owing to their enhanced cutinite contents.As indicated by pyrolysis and elemental analysis results,the Devonian cutinitic liptobioliths are dominated by typeⅠ-Ⅱkerogens and have an excellent potential to generate liquid hydrocarbons.The Baishaping cutinitic liptobioliths are mainly composed of ribbon-like thick-walled cutinites,with small amounts of thin-walled type.Vitrinite is only present in trace amounts and is dominated by telinite.Meanwhile,the Damaidi Devonian coals are primarily composed of ribbon-like thin-walled cutinites,followed by collotelinites which are usually sandwiched by cutinites.The different petrological characteristics of the Baishaping and Damaidi liptobioliths might indicate a structural variation in the coal-forming plant cuticles and two distinct coal-forming conditions.The molecular bio markers in the Devonian coals are mainly composed of C_(18)-C_(20)tetracyclic diterpenoids,which are assumed to be the dominant soluble constituent of the Devonian land-plant cuticles and might have played an important role in early land plant radiation.Other molecules include aromatic tetracyclic diterpenoids,3-5 ring polycyclic aromatic hydrocarbons and their methylated counterparts,and C_(16)-and C_(18)-monocarboxylic acids.n-Alkanes are present only in small amounts.The molecular composition of the cutinite-rich coals is unexpected,because cuticular waxes are one of the most important sources of n-alkanes.In general,the petrology and geochemistry of the Devonian cutinitic liptobiolith indicate a distinct structure and composition for the early land-plant cuticles,which is significantly different from that of the plant cuticles since Carboniferous.Devonian cutinitic liptobioliths are of great interest because of their unique petrography,geochemistry,coal-forming plants,and oil-prone potential.Studies on this unique coal type provide a better understanding of coal-forming plants,paleoenvironment,paleoclimate,and early land-plant evolution in the Devonian.展开更多
Bottle gourd (Lagenaria siceraria), colloquially known as “lauki” or “doodhi” in India, is an edible plant in the Cucurbitaceae family. Consumption of raw bottle gourd juice is common practice in India. However, l...Bottle gourd (Lagenaria siceraria), colloquially known as “lauki” or “doodhi” in India, is an edible plant in the Cucurbitaceae family. Consumption of raw bottle gourd juice is common practice in India. However, little known is the fact that ingestion of raw bottle gourd juice that is extremely bitter tasting is associated with cucurbitacin toxicity. Cucurbitacin is a pheromone produced by the plant as a defense mechanism against insects and herbivores. It is responsible for imparting the bitter taste, and the associated toxicity. The exact mechanism of cucurbitacin toxicity is not well understood, however it is suspected to result in gastric erosions and increased capillary permeability, resulting in rapid onset of vomiting, diarrhea, gastrointestinal bleeding, hypotension and shock. As serum and urine concentration measurements of cucurbitacin are not readily available, bottle gourd toxicity remains a clinical diagnosis based largely on the temporal association of ingestion of unusually bitter tasting vegetable or its juice with rapid onset of symptoms. Physician awareness is therefore of paramount importance in the diagnosis of this unusual entity. We present the case of a 78-year-old woman, with no comorbid conditions, who presented to the Emergency Department (ED) with three episodes of vomiting and multiple episodes of watery loose stools soon after ingestion of extremely bitter tasting, fresh bottle gourd juice. A prompt diagnosis of cucurbitacin toxicity was made in the ED and fluid resuscitation was commenced expeditiously. However, it was noted that most physicians were unfamiliar with this entity, and therefore skeptical of the diagnosis. Our rationale in presenting this clinical case report is three-fold: 1) To create physician awareness regarding this unique clinical entity, especially among emergency physicians, as they are the first point of contact for a critically ill patient. 2) To highlight the rapid onset and progression of symptoms in cucurbitacin toxicity. 3) To emphasize aggressive fluid resuscitation and symptomatic management as the mainstay of clinical treatment.展开更多
Saponins,the major bioactive components of Panax ginseng C.A.Mey.,are gradually emerging as research hotspots owing to the possession of various pharmacological activities.This review updates the ginsenosides list fro...Saponins,the major bioactive components of Panax ginseng C.A.Mey.,are gradually emerging as research hotspots owing to the possession of various pharmacological activities.This review updates the ginsenosides list from P.ginseng and the steam-processed ginseng(red ginseng and black ginseng)up to 271 by June of 2024,encompassing 243 saponins from different parts of P.ginseng(roots,stems,leaves,flowers,berries,and seeds),103 from red ginseng,and 65 from black ginseng,respectively.Among 271 saponins,there are a total of 249(1–249)dammarane type(with a–z subtypes)tetracyclic triterpene saponins reported from each part of P.ginseng and steam-processed ginseng,two(250–251)lanostane type tetracyclic triterpene saponins identified from red ginseng,18(252–269)oleanane type pentacyclic triterpenoid saponins discovered from each part of P.ginseng and steam-processed ginseng,and two(270–271)ursane type pentacyclic triterpenoid saponins reported from red ginseng.Overall,this review expounds on the chemical diversity of ginsenosides in various aspects,such as chemical structure,spatial distribution and subtype comparison,processed products,and transformation.This facilitates more indepth research on ginsenosides and contributes to the future development of ginseng.展开更多
基金the National Natural Science Foundation of China(No.22471224)。
文摘A category of highly fused diterpenoid natural products possessing a characteristic perhydropyrene-like or rearranged tetracyclic skeleton structure are distributed in different life forms.Compared to traditional polycyclic diterpenoids,their biosynthetic pathways are quite unique and diverse.Chemists have pinpointed a range of this type of unusual diterpenoids:cycloamphilectanes and isocycloamphilectanes,kempenes and rippertanes,hydropyrene and hydropyrenol,along with recently disclosed cephalotanes.This review describes developments in this field and discusses the challenges associated with synthesizing this class of highly complex compounds.
基金The Basic Prospective Research Project of China National Offshore Oil Corporation under contract No.KJQZ-2024-2003.
文摘The northern South China Sea,including the Zhujiangkou Basin and the Beibuwan Basin,developed high-quality lacustrine source rocks during the Eocene rifting period.These source rocks are vital for hydrocarbon generation in the northern South China Sea.The ZhuⅠdepression in the Zhujiangkou Basin and the Beibuwan Basin typically exhibit high abundance of C_(30)4-methyl steranes.However,shales in the Eocene Wenchang Formation in the ZhuⅢdepression of the Zhujiangkou Basin contains lower quantities of high-quality lacustrine source rocks with 4-methyl steranes,which often co-elute with some pentacyclic triterpanes in gas chromatography-mass spectrometry(GC-MS).Therefore,the single 4-methylsterane parameter based on GC-MS cannot accurately distinguish organic source in the deep to semi-deep water lacustrine source rocks of the Wenchang Formation from other source rocks,thus impeding the recognition of their contributions to petroleum reservoirs.In this study,GC-MS of aliphatic hydrocarbons,palynofacies and algal identification,as well as stable carbon isotope data of organic matter were used to identify the algal species and construct the paleoclimate during deposition of the Wenchang Formation source rocks in the ZhuⅢdepression of the Zhujiangkou Basin.It is suggested that during the Wenchang Formation period,freshwater green algae prevailed in the lake,which is likely account for the relatively low content of 4-methyl steranes in the high-quality lacustrine source rocks.Controlled by the algal species,it is proposed that the content of C_(30)tetracyclic polyprenoids(TPP)can better indicate the quality of the Wenchang source rocks than C_(30)4-methyl steranes.Consequently,a relationship between the TPP index and the quality of the lacustrine source rocks in the Wenchang Formation of the ZhuⅢdepression was established.A higher TPP index indicates higher organic matter abundance and hydrogen index of the lacustrine source rocks.When applied to the origin analysis of oils in the ZhuⅢdepression,it is believed that the organic-rich deep lacustrine source rocks in the Wenchang Formation made great contribution to the transitional zone crude oils in the Wenchang A and Wenchang B depressions.
文摘Salvianolic acid G,a caffeic acid dimer with a novel tetracyclic skeleton was isolated from the roots of Salvia miltiorrhiza.Its structure was elucidated by chemical and spectral analysis,especially by 2D NMR analysis.
文摘Novel tetracyclic terpanes X and Y namely C24-des-A-oleanane and C27 tetracyclic terpane were detected in crude oils and source rock extracts in Zhu 1 depression in Pearl River Mouth Basin by GC-MS analysis technology. These compounds are similar to oleanane in the structure, and their relative abundance in m/z 191 partial mass cbromatogram has a good correlation with oleanane. Here compounds X and Y are considered to be derived from the des-A degradation of oleanoid precursor. The ratio of X/（X-I-C24） and Y/（Y-I-C24） increase with the increasing inputs of terrigenous organic matter in crude oils. Wenchang Formation middle-deep lacustrine source rocks with planktonic algae organic matter inputs and oil generating from it contain low abundance of compounds X and Y, while Enping Formation coal measures source rocks with terrigenous higher plants organic matter inputs and oil generating from it usually have higher compounds X and Y. In general when two terrigenous compounds C19 tricyclic terpane and bicadinane-T are high in crude oils, there are also a corresponding high abundant compounds X and Y. Relative abundance of compounds X and Y is closely related to the source of organic matter and it can indicate the input of terrigenous organic matter.
基金supported by open fund of Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education,No.K2021-13China Postdoctoral Science Foundation(2021M692751)Tianjin branch of CNOOC(CCL2020TJT0NST1956)。
文摘C_(24)tetracyclic terpanes are common compounds in source rocks and crude oils,and C_(24)17,21-secohopane is the most common and widely used source-related indicator.In this study,three unusual C_(24)tetracyclic terpanes were detected on the m/z 191 chromatogram of saturated hydrocarbons in the Shahejie Formation source rocks in the Bozhong subbasin.Based on the mass spectra characteristics,diagnostic ion fragments,retention time and comparisons with published literature,three unusual C_(24)tetracyclic terpanes were identified as 10β(H)-des-A-oleanane,10β(H)-des-A-lupane and C_(24)des-Ahopane.To the best of our knowledge,this is the first study to detect and publicly report these three compounds in source rock samples from the Shahejie Formation of the Bozhong subbasin,Bohai Bay Basin.The results indicated that 10β(H)-des-A-oleanane and 10β(H)-des-A-lupane likely originated from terre strial angiosperms,while C_(24)des-A-hopane likely originated fro m prokaryotic o rganisms.Te rrestrial angiosperms provide the material basis for the generation of compounds A and B,and the distribution and concentration of these two compounds are affected by thermal maturity.In the low maturity stage(0.5%<R_(0)<0.7%),compounds A and B are relatively enriched in the source rocks.
文摘Tricyclic and tetracyclic terpanes are important constituents of crude oil and source rock extracts.However,they have not been reported in the Offshore Niger Delta Basin,Nigeria.Thus,the present study investigated the geochemical significance of tricyclic and tetracyclic terpanes in source rock extracts from the Offshore Niger Delta Bain,Nigeria with gas chromatography-mass spectrometry(GC-MS).The total relative abundances of tricyclic terpanes,C_(19)TT-C_(21)TT,and C_(23) TT in the rock samples ranged from 82.50 to 96.37%,50.08 to 74.17%,and 25.83 to 49.92%,respectively.These values showed the source rocks were formed from a mixed origin(terrestrial and marine).Among the tricyclic and tetracyclic terpanes identified in the rock extracts,the conventional(C_(20)TT,C_(23)TT,C_(24)TT,C_(24)TeT)and recent(Y1,X1,Z1)were more prominent than all others,indicating mixed input of terrigenous and marine organic matter.The C_(24)TT/C_(23)TT,C_(24)TeT/(C_(24)TeT+C_(26)TT),C_(19)TT/C_(23)TT,C_(20)TT/C_(23)TT,C_(25)TT/C_(24)TeT,C_(25)TT/C_(26)TT,C_(19)TT/C_(20)TT,C_(24)TeT/C_(26)TT,Z1/(Z1+C_(24)TT),and Y1/(Y1+C_(24)TT)in the rock samples range from 0.33 to 1.30,0.76 to 0.90,0.18 to 0.73,0.34 to 1.05,0.33 to 1.74,0.30 to 1.39,0.31 to0.89,1.66 to 4.33,0.36 to 0.83,and 0.34 to 0.79,respectively.These values further showed that the rock samples were formed from mixed input of terrigenous and marine organic matter and deposited under oxic to suboxic conditions in lacustrine-fluvial/deltaic environments.Also,the C_(24)TeT/C_(20)-26TT,C_(24)TeT/C_(30)HOP,and C_(23)TT/C_(30)HOP ranged from 0.16 to 0.45,0.02 to 0.42,and 0.01 to 0.48,respectively.This range of values suggests that source rocks were within immature to early mature stage.Thus,this study showed that tricyclic and tetracyclic terpanes were effective in determining the origin,depositional environments,and thermal maturity of source rocks in the Niger Delta Basin,Nigeria.
文摘Four new taxane diterpenoids were isolated from the bark of Taxus yunnanensis.Their structures were elucidated as the new skeleton with 5/7/6/4 membered rings by spectral analysis and 2D NMR shift correlation experiments.
文摘Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacolog‐ical activities.However,a direct stereoselective method from simple and readily‐made coumarins derivatives remains challenging due to the inertness of coumarins as dienophiles.Herein,we de‐velop a decarboxylative asymmetric[4+2]cycloaddition of 3‐cyanocoumarins with vinyl benzoxa‐zinones,affording the coumarin‐derived condensed rings bearing three continuous stereocenters in high yields with excellent diastereoselectivities(>20/1 d.r.)and enantioselectivities(up to 99%ee).This direct enantioselective reaction was achieved by a Pd(0)/Cu(I)bimetallic catalytic system.The mechanism studies indicated that the synergistic activation effect,in which chiral Cu(I)as an availa‐ble Lewis acid catalyst activates 3‐cyanocoumarin and chiral Pd(0)complex activates benzoxazi‐none by the formation ofπ‐allyl‐palladium intermediate,plays an important role on the stereoselec‐tive control.The current work provides a new activation modes of Cu catalyst in the Pd/Cu bimetal‐lic catalytic system.
文摘Two new tetracyclic taxane diterpenoids----yunnanxol(1) and yunnanxamine(2)have been isolated from the bark of Taxus yunnanensis Cheng et L.K.Fu.Their structures have been established from the spectral data,mainly from MS,highfield ~1H NMR,~1H-~1H COSY, ^(13)C NMR,^(13)C-~1H COSY and ^(13)C-~1H COLOC spectroscopies.
文摘A new skeleton taxane diterpene,taxayuntin,was isolated from the leaves and stems of Taxus yunnanensis.Its structure was determined by spectroscopic methods(MS,~1H NMR,^(13)C NMR, ~1H-~1H COSY,~1H-^(13)C COSY and ^(13)C-~1H COLOC)and X-ray diffraction.
文摘The key intermediate 5 for synthesis of the contragestationally active diterpenoid grandiflorenic acid(1)and its analogues 2 and 3 was prepared and an acetyl transposition reaction occurred in the SeO_2 oxida- tion of 8.
文摘Let be a graph with n vertices and m edges. The sum of absolute value of all coefficients of matching polynomial is called Hosoya index. In this paper, we determine 2<sup>nd</sup> to 4<sup>th</sup> minimum Hosoya index of a kind of tetracyclic graph, with m = n +3.
基金supported by the National Natural Science Foundation of China (No. 81273387)
文摘Atisane diterpenes are biologically interesting natural products. We report here a convergent approach to construct the tetracyclic core of the atisane skeleton. The two segments were assembled through a Wittig reaction, while an intramolecular Aldol condensation served as the key step to furnish the tetracyclic skeleton.
基金funded by Outstanding Youth Foundation of Heilongjiang province(NO.YQ2021H009).
文摘Objective: To isolate bioactive compounds from the endophytic fungus Fusarium sporotrichioides isolated from Rauwolfia yunnanensis, and investigate their pharmacological activities.Methods: The chemical constituents were isolated and purified by combining with ODS column chromatography, silica gel column chromatography and by performing semipreparative HPLC. Their structures were established on the basis of 1D NMR(1H-NMR and13C-NMR) and 2D NMR(1H–1H COSY,HSQC, HMBC and NOESY), as well as HRESIMS and comparison with literature data. In addition, the absolute configuration of compound 1 was determined by calculated ECD data.Results: One previously undescribed tetracyclic triterpenoid derivative, named as integracide L(1), 12aacetoxy-4,4-dimethyl-24-methylene-5a-cholesta-8,14-diene-2a,3β,11β-triol(2), 12a-acetoxy-4,4-dime thyl-24-methylene-5a-cholesta-8-momoene-2a,3β,11β-triol(3), 12a-acetoxy-4,4-dimethyl-24-methy lene-5a-cholesta-8,14-diene-3β,11β-triol(4), and 12a-acetoxy-4,4-dimethyl-24-methylene-5acholesta-8-momoene-3β,11β-triol(5) were isolated from F. sporotrichioide. Moreover, compound 1 was rare tetracyclic triterpenoid with single methyl replacement at C-4 position.Conclusion: Compound 1 was a new tetracyclic triterpenoid isolated from the endophytic fungus F.sporotrichioides. In addition, compound 2 could inhibit the growth of three different human cancer cells significantly. Compounds 3 and 5 were found to possess better cytotoxic activities on Hep G-2 cells than the other compounds, with IC50values of(2.8 ± 0.1) and(6.3 ± 0.3) μmol/L respectively.
文摘A series of novel tetracyclic triterpanes based on the lanostane skeleton, ranging in cars-bon number from C_(30) to C_(32), were identified for the first time in Eocene lacustrine depo-its of Biyang Depression, China. These compounds have been identified by GC, GC- MS, andcoinjection with authentic standard, as 8β(H), 9α(H)- lanostane (C_(30)), 24-methyl- lanostane(C_(31)) and 24- ethyl- lanostane (C_(32)). Mechanisms are proposed for the origin and geologicalfate of these compounds. To the best of our knowledge, this is the first confirmed occur-rence of lanostanes in the sedimentary record.
文摘Grandiflorenic acid(1),possessing potent contragestational activity,is an ent-kauranediterpenoid.It has been isolated from Mexical medicinal plant zoapatle(Montanoa tomento)In connection with our synthetic work on ent-kaurane diterpenoids,we are interested in theconversion of stevioside(2)occurred abundantly in Stevia rebaudiana into grandiflorenic acid
基金the generous financial support from Natural Science Foundation of Henan Province (No.222300420084)application research plan of Key Scientific Research Projects in Colleges and Universities of Henan Province (No.22A150056)+1 种基金the Youth Innovation Team Program in Colleges and Universities of Shandong Province (No.2022KJ228)National Natural Science Foundation of China (No.22208302)。
文摘Due to the high electrophilic nature of azo-dienophiles, azo-Diels–Alder proceeds rapidly even without the need of a catalyst and is therefore regarded as the “click reaction”. This spontaneity causes strong background reaction and poses a daunting challenge to chemists for developing the catalytic asymmetric version. Reported herein is the first catalytic asymmetric dearomative azo-Diels–Alder reaction between2-vinylindoles and triazoledione. This protocol makes use of the high energy barrier of dearomatization to avert the strong background reaction of azo-Diels–Alder reaction, allowing the implementation of the projected reaction at ambient temperature. Density functional theory calculations have been performed to gain insights into the reaction mechanism and the origins of the enantioselectivity. By using this method,a variety of tetracyclic indole derivatives have been readily prepared in good to excellent yields and with excellent diastereo-and enantio–selectivities(33 examples, up to 97% yield and >99% ee, >20:1 dr).
基金founded by the National Natural Science Foundation of China(Grant No.42073069)。
文摘Devonian cutinitic liptobiolith is a special type of coal formed during the early evolutionary stage of land plants.The Baishaping and Damaidi Devonian coals are notable for their distinct papery,sheet-like texture,and unusually high cutinite content(>50%),belonging to typical cutinitic liptobiolith.They are bituminous coals and have a suppressed vitrinite reflectance.Compared with typical typeⅢkerogen,these liptobioliths are characterized by extremely high yields of volatile matter and high hydrogen contents owing to their enhanced cutinite contents.As indicated by pyrolysis and elemental analysis results,the Devonian cutinitic liptobioliths are dominated by typeⅠ-Ⅱkerogens and have an excellent potential to generate liquid hydrocarbons.The Baishaping cutinitic liptobioliths are mainly composed of ribbon-like thick-walled cutinites,with small amounts of thin-walled type.Vitrinite is only present in trace amounts and is dominated by telinite.Meanwhile,the Damaidi Devonian coals are primarily composed of ribbon-like thin-walled cutinites,followed by collotelinites which are usually sandwiched by cutinites.The different petrological characteristics of the Baishaping and Damaidi liptobioliths might indicate a structural variation in the coal-forming plant cuticles and two distinct coal-forming conditions.The molecular bio markers in the Devonian coals are mainly composed of C_(18)-C_(20)tetracyclic diterpenoids,which are assumed to be the dominant soluble constituent of the Devonian land-plant cuticles and might have played an important role in early land plant radiation.Other molecules include aromatic tetracyclic diterpenoids,3-5 ring polycyclic aromatic hydrocarbons and their methylated counterparts,and C_(16)-and C_(18)-monocarboxylic acids.n-Alkanes are present only in small amounts.The molecular composition of the cutinite-rich coals is unexpected,because cuticular waxes are one of the most important sources of n-alkanes.In general,the petrology and geochemistry of the Devonian cutinitic liptobiolith indicate a distinct structure and composition for the early land-plant cuticles,which is significantly different from that of the plant cuticles since Carboniferous.Devonian cutinitic liptobioliths are of great interest because of their unique petrography,geochemistry,coal-forming plants,and oil-prone potential.Studies on this unique coal type provide a better understanding of coal-forming plants,paleoenvironment,paleoclimate,and early land-plant evolution in the Devonian.
文摘Bottle gourd (Lagenaria siceraria), colloquially known as “lauki” or “doodhi” in India, is an edible plant in the Cucurbitaceae family. Consumption of raw bottle gourd juice is common practice in India. However, little known is the fact that ingestion of raw bottle gourd juice that is extremely bitter tasting is associated with cucurbitacin toxicity. Cucurbitacin is a pheromone produced by the plant as a defense mechanism against insects and herbivores. It is responsible for imparting the bitter taste, and the associated toxicity. The exact mechanism of cucurbitacin toxicity is not well understood, however it is suspected to result in gastric erosions and increased capillary permeability, resulting in rapid onset of vomiting, diarrhea, gastrointestinal bleeding, hypotension and shock. As serum and urine concentration measurements of cucurbitacin are not readily available, bottle gourd toxicity remains a clinical diagnosis based largely on the temporal association of ingestion of unusually bitter tasting vegetable or its juice with rapid onset of symptoms. Physician awareness is therefore of paramount importance in the diagnosis of this unusual entity. We present the case of a 78-year-old woman, with no comorbid conditions, who presented to the Emergency Department (ED) with three episodes of vomiting and multiple episodes of watery loose stools soon after ingestion of extremely bitter tasting, fresh bottle gourd juice. A prompt diagnosis of cucurbitacin toxicity was made in the ED and fluid resuscitation was commenced expeditiously. However, it was noted that most physicians were unfamiliar with this entity, and therefore skeptical of the diagnosis. Our rationale in presenting this clinical case report is three-fold: 1) To create physician awareness regarding this unique clinical entity, especially among emergency physicians, as they are the first point of contact for a critically ill patient. 2) To highlight the rapid onset and progression of symptoms in cucurbitacin toxicity. 3) To emphasize aggressive fluid resuscitation and symptomatic management as the mainstay of clinical treatment.
基金funded by the Innovation Platform(base)and Talent Special Project(No.20210502005ZP)Key Research and Development Program of Jilin Province(No.20230204038YY,20240305052YY,20210204149YY)。
文摘Saponins,the major bioactive components of Panax ginseng C.A.Mey.,are gradually emerging as research hotspots owing to the possession of various pharmacological activities.This review updates the ginsenosides list from P.ginseng and the steam-processed ginseng(red ginseng and black ginseng)up to 271 by June of 2024,encompassing 243 saponins from different parts of P.ginseng(roots,stems,leaves,flowers,berries,and seeds),103 from red ginseng,and 65 from black ginseng,respectively.Among 271 saponins,there are a total of 249(1–249)dammarane type(with a–z subtypes)tetracyclic triterpene saponins reported from each part of P.ginseng and steam-processed ginseng,two(250–251)lanostane type tetracyclic triterpene saponins identified from red ginseng,18(252–269)oleanane type pentacyclic triterpenoid saponins discovered from each part of P.ginseng and steam-processed ginseng,and two(270–271)ursane type pentacyclic triterpenoid saponins reported from red ginseng.Overall,this review expounds on the chemical diversity of ginsenosides in various aspects,such as chemical structure,spatial distribution and subtype comparison,processed products,and transformation.This facilitates more indepth research on ginsenosides and contributes to the future development of ginseng.
