Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting gro...Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.展开更多
Amino group protective strategy has consequently emerged in multistep organic synthesis.Easy and selective deprotection procedures are crucial to facilitate the chemical transformation.Recently,Zhang’s group from Hen...Amino group protective strategy has consequently emerged in multistep organic synthesis.Easy and selective deprotection procedures are crucial to facilitate the chemical transformation.Recently,Zhang’s group from Henan Normal University collaborating with Chen’s group of Nankai University developed a novel strategy for the regiospecific cleavage of inert aryl C-N bonds in N-aryl amides by hypervalent iodine(V)reagents.These procedures allow removal of sort of aryl groups under mild conditions to give primary amides in high efficiency.It bestows these aryl groups with the characteristics of amino protecting groups that might be the supplement of amino protecting group chemistry.展开更多
The confrontation between the disadvantaged and advantaged groups is eternal throughout the competition for survival. But the human spiritual world has its humane aspect in addition to competition. The concern for and...The confrontation between the disadvantaged and advantaged groups is eternal throughout the competition for survival. But the human spiritual world has its humane aspect in addition to competition. The concern for and protection of the disadvantaged group is the moral law characteristic of humanity, just as the Universal Declaration of Human Rights says in its Article 1： ＂All human beings are born free and equal in dignity and rights.展开更多
Aryl ketones as photolabile protecting group(PPG)to modify purine imines is a novel nucleic acid protection strategy.Especially,photoprotection of N7-guanosine is the first reported photoprotected nucleoside that can ...Aryl ketones as photolabile protecting group(PPG)to modify purine imines is a novel nucleic acid protection strategy.Especially,photoprotection of N7-guanosine is the first reported photoprotected nucleoside that can affect the Hoogsteen recognition site of guanosine.However,the mechanism,which is pivotal to high efficiency of photorelease and applications of PPGs in biological and medical systems,is unclear.Here,a detailed deprotection mechanism of benzophenone protected guanosine(BP-Guo)at N7 position is reported.Upon irradiation,BP-Guo populates to singlet state,which generates^(3)[BP]-Guo via intersystem crossing process.Thereafter,triplet energy transfer competes with hydrogen atom transfer forming BP-^(3)[Guo]and ketyl-Guo,respectively.Both species break C–N bond to release guanosine.These results provide deeper insights into exploiting improved strategies for photo-protecting nucleic acids.In particular,the TTET pathway could trigger well-known cyclization reactions that brings about DNA mutagenic adducts.The latter should be avoided in developing improved strategies for photoprotecting nucleic acids.展开更多
Protecting groups often play an essential role in organic synthesis, particularly for multi-step synthesis or natural product total synthesis. Various protecting groups areavailable to mask the vulnerable functionalit...Protecting groups often play an essential role in organic synthesis, particularly for multi-step synthesis or natural product total synthesis. Various protecting groups areavailable to mask the vulnerable functionality;phenolic hydroxy groups are noteworthy examples, but their stability differs when protected. Herein, the compatibility of protective phenolic functionality was investigated with the implementation of indium (III) triflate-catalyzed oxidative esterification using Oxone in methanol. A wide range of protective moieties was selected and subjected to Oxone-mediated oxidative esterification. For example, sulfonates were found to be sufficiently stable and inert whereas acetals were susceptible to reaction conditions. The details of this investigation are provided.展开更多
A new IL-supported diol, 1-（2,3-dihydroxypropyl）-3-methylimidazolium hexafluorophosphate has been synthesized and characterized by Fr-IR, ^1H NMR, ^13C NMR and MS （ESI）. Its physical properties such as freezing po...A new IL-supported diol, 1-（2,3-dihydroxypropyl）-3-methylimidazolium hexafluorophosphate has been synthesized and characterized by Fr-IR, ^1H NMR, ^13C NMR and MS （ESI）. Its physical properties such as freezing point, solubility and specific gravity and thermal stability were determined. Synthetic utilities of the resultant diol as a protecting group for aldehydes were also investigated.展开更多
A novel polymer-bound 1,2-diol, 3-polystyrylsulfonyl-1,2-propanediol (6) had been prepared by the reaction of sodium polystyrylsulfinate with allyl bromide, followed by oxidation and. hydrolysis or directly with 3-chl...A novel polymer-bound 1,2-diol, 3-polystyrylsulfonyl-1,2-propanediol (6) had been prepared by the reaction of sodium polystyrylsulfinate with allyl bromide, followed by oxidation and. hydrolysis or directly with 3-chloro-1,2-propanediol in the presence of a phase transfer catalyst, n-tetrabutylammonium iodide. The capacity of resin 6 for terephthaidehyde reached 1.43 mmol/g. The aldehydic groups attached to polymer 6 reacted with hydroxylamine hydrochloride or reduced by sodium borohydride giving p-formylbenzaldoxime (yield: 89%)and p-formyl-benzalcohol (yield: 734%), respectively. The high yields of these polymer-supported reactions showed that the polymer 6 possessed the effective isolation of its reactive sites.展开更多
In the course of organic synthesis, particularly for multi-step synthesis or natural product total synthesis, the selection of appropriate protective groups for the intended functionality is crucial in order to achiev...In the course of organic synthesis, particularly for multi-step synthesis or natural product total synthesis, the selection of appropriate protective groups for the intended functionality is crucial in order to achieve chemoselective synthetic goals. The development of many useful protective groups has been reported based on the functionality of the anilino group. Herein, we discuss our study of various protective groups and the processes we used to establish compatibility with anilino functionality via the implementation of Oxone-mediated oxidative esterification in methanol. The results and the details of our experiments are reported herein.展开更多
On March 19, an academic forum was held in Jinan City, Shandong Province, on protection of vulnerable groups’ rights. Sponsored by the Law School of Shandong University, it gathered some 50 experts from the Central P...On March 19, an academic forum was held in Jinan City, Shandong Province, on protection of vulnerable groups’ rights. Sponsored by the Law School of Shandong University, it gathered some 50 experts from the Central Patty School, Chinese Academy of Social Sciences, China Society for Human Rights Studies, Shandong Higher People’s Court, as well as some research universities in the country. Four subjects were discussed at the forum: definition of vulnerable groups, legal principles for protection of vulnerable groups’展开更多
In recent years,the use of light to selectively and precisely activate drugs has been developed along the fundamental concepts of photopharmacology.One of the key methods in this field relies on transiently silencing ...In recent years,the use of light to selectively and precisely activate drugs has been developed along the fundamental concepts of photopharmacology.One of the key methods in this field relies on transiently silencing the drug activity with photocleavable protecting groups(PPGs).To effectively utilize light-activated drugs in future medical applications,physicians will require a reliable method to assess whether light penetrates deep enough into the tissues to activate the photoresponsive theragnostic agents.Here,we describe the development and evaluation of magnetic resonance(MR)imaging agents that allow for the detection of light penetration and drug activation in the tissues using non-invasive whole-body magnetic resonance imaging(MRI)and chemical exchange saturation transfer(CEST)-MRI modalities.The approach relies on the use of PPG-protected MR contrast agents,which upon irradiation with light change their imaging signal.A Gadolinium(III)-based MRI contrast agent is presented that undergoes a significant change in relaxivity(25%)upon uncaging,providing a reliable indicator of lightinduced cargo release.Additionally,we introduce the first light-responsive CESTMRI imaging agent,enabling positive signal enhancement(off-to-on)upon light activation,offering a novel approach to visualize the activation of photoactive agents in living tissues.This research provides a proof-of-principle for the noninvasive,whole-body imaging of light penetration and drug activation with high temporal resolution characteristic of MR methods.展开更多
Traditional protecting groups are often removed under harsh conditions with potentially hazardous reagents,thereby impeding the convenient synthesis of oligosaccharides and glycosides.Herein,we present to utilize the ...Traditional protecting groups are often removed under harsh conditions with potentially hazardous reagents,thereby impeding the convenient synthesis of oligosaccharides and glycosides.Herein,we present to utilize the photolabile ortho-nitro-benzyl carbonate(oNBC)as a permanent hydroxyl protecting group for stereocontrolled synthesis of glycosides.The Ph3PO-modulated glycosylation with strongly disarmed per-O-oNBC-protected glycosyl ynenoates preferred to afford glycosides with excellentα-selectivities via theβ-phosphonium transition state.Based on the oNBC-mediated galactosylation,synthesis of the glycolipid digalactosyl diacylglycerol(DGDG)containing six double bonds and two esters was achieved in a straightforward manner.展开更多
Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this...Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.展开更多
Aim To synthesize the tripepide Weinreb amide Boc Asp(OBzl) β Ala Asp(OBzl) N(OMe)Me (7) as a useful precursor of aspartyl peptide aldehyde derivatives; Methods DCC, IBCF method was used for preparation of ...Aim To synthesize the tripepide Weinreb amide Boc Asp(OBzl) β Ala Asp(OBzl) N(OMe)Me (7) as a useful precursor of aspartyl peptide aldehyde derivatives; Methods DCC, IBCF method was used for preparation of Weinreb amide; N hydroxysuccinimide activated ester was used in peptide synthesis; and Boc as N protecting group of amino acid. Results Boc Asp(OBzl) N(OMe)Me (3), Boc β Ala Asp(OBzl) N(OMe)Me (5), and Boc Asp(OBzl) β Ala Asp(OBzl) N(OMe)Me (7) were synthesized successfully. Conclusion An useful precursor of tripeptide aspartyl aldehydes was synthesized.展开更多
Precise and spatiotemporal control over the pesticide remains to be a challenge.More efficient controlled release systems(CRSs)have been developed to support the precise delivery of active ingredients.Herein,we incorp...Precise and spatiotemporal control over the pesticide remains to be a challenge.More efficient controlled release systems(CRSs)have been developed to support the precise delivery of active ingredients.Herein,we incorporated the photoremovable protecting groups(PRPGs)into phenamacril(PHE)and obtained two photo-responsive fungicides of NV-PHE and DEACM-PHE.The 4,5-dimethoxy-o-nitrobenzyl(NV)or 7-diethylaminocoumarin(DEACM)-caged PHE could release the active molecule PHE after irradiation of UV light and blue light,respectively.Optical properties and in-vitro/vivo fungicidal activities of NV-PHE and DEACM-PHE demonstrated the feasibility for light controlled release of PHE.DEACM-PHE could release 98%PHE by illumination of blue light.The irradiated DEACM-PHE could preserve the similar bioactivity of PHE,and significantly improve the in-vitro/vivo fungicidal activities compared to the non-irradiated DEACM-PHE.The optical controlled release of PHE from DEACM-PHE enabled the precise and spatiotemporal delivery of PHE,diversifying the development of CRSs for pesticide,and providing environmentfriendly agricultural applications with high pesticide efficiency.展开更多
Various alcohols and phenols were trimethylsilylated in excellent yields using hexamethyldisilazane in the presence of catalytic amounts of environmentally friendly, hydrophobic, highly thermal stable, and completely ...Various alcohols and phenols were trimethylsilylated in excellent yields using hexamethyldisilazane in the presence of catalytic amounts of environmentally friendly, hydrophobic, highly thermal stable, and completely heterogeneous sulfonic acid functionalized mesostructured SBA-15 in dichloromethane at ambient temperature. Primary, bulky secondary, tertiary, and phenolic hydroxyl functional groups were transformed to the corresponding trimethylsilyl ethers in excellent yields. The simple experimental procedure was accompanied by easy recovery and the catalyst was reusable (at least 18 reaction cycles); these are attractive features of this protocol.展开更多
Photocages are a class of substances containing photosensitive groups,also known as“photoremovable protecting groups”,from which target substances are released upon exposure to specific wavelengths of light.The subs...Photocages are a class of substances containing photosensitive groups,also known as“photoremovable protecting groups”,from which target substances are released upon exposure to specific wavelengths of light.The substances released in the light-promoted processes have chemical or biological properties that enable them to carry specifically designed functions.As a result,photocages can be utilized in various fields such as chemistry,biology,and medicine.In this paper,progress made in research carried out in recent years aimed at developing photocage molecules with different photosensitive moieties is reviewed.展开更多
Semi-synthesis of paclitaxel was achieved in four steps from 10-deacetylbaccatin HI （10-DAB HI）. The key steps are the regioselective protection at the hydroxyl group at C-7 of 10-DAB HI, using 1,1′-thiocarbonyldii...Semi-synthesis of paclitaxel was achieved in four steps from 10-deacetylbaccatin HI （10-DAB HI）. The key steps are the regioselective protection at the hydroxyl group at C-7 of 10-DAB HI, using 1,1′-thiocarbonyldiimidazole as a selective reagent, and the deprotection of the protected paclitaxel with a mixture of p-toluenesulfonic acid and 0.1 mol/L aqueous hydrochloride.展开更多
Selective protection of one of the hydroxyl group in 1, n-symmetrical diols is achieved by P2O5/SiO2-catalyzed reaction of the diol with dihydropyran under solvent-free conditions at room temperature. This selective p...Selective protection of one of the hydroxyl group in 1, n-symmetrical diols is achieved by P2O5/SiO2-catalyzed reaction of the diol with dihydropyran under solvent-free conditions at room temperature. This selective protection is simple and it occurred under economically cheap conditions in high yield. The deprotected diol is simply obtained by refluxing of this compound in methanol using the same catalyst without any byproduct formation or additional purifications.展开更多
A simple and efficient protocol for the deprotection of dithioacetal,1,3-dithianes and 1,3-dithiolanes has been developed using H_2O_2-SOC1_2 reagent system.In addition to the absence of overoxidation products for oxi...A simple and efficient protocol for the deprotection of dithioacetal,1,3-dithianes and 1,3-dithiolanes has been developed using H_2O_2-SOC1_2 reagent system.In addition to the absence of overoxidation products for oxidation-prone substrates,high chemoselectivity, the low cost and availability of the reagents,simplicity of the method,short reaction times,and excellent yields can also be considered as strong points for this method.展开更多
Personality rights are basic rights related to human dignity in the concept of human rights protection,and respect for personality rights is the basic prerequisite for safeguarding other human rights.Human rights prot...Personality rights are basic rights related to human dignity in the concept of human rights protection,and respect for personality rights is the basic prerequisite for safeguarding other human rights.Human rights protection exerts a profound impact on the value of legislation and enforcement practices of private international laws in the field of cross-border personality rights infringement in various countries,which is mainly manifested in the integration of substantive justice and the humanistic care concept of protecting the rights of vulnerable groups into formal justice,and expands the development space of human rights protection ideas in cross-border personality rights and tort conflict laws.the diversity of human rights protection values determines that cross-border personality rights infringement may lead to conflicts between personality rights and other basic rights,such as freedom of speech.to reconcile such conflicts,a workable method is to prioritize personality rights protection in accordance with the hierarchy of rights theory in the value judgment of public order reservation or to clarify the limits of the right holder’s tolerance obligation through the limited application of the principle of proportionality.China’s current cross-border personality rights and tort conflict law can optimize the protection of the rights of vulnerable groups by diversifying the options of available legal methods,and establish a balancing mechanism between personality rights and freedom of speech,so as to improve China’s legal protection system for human rights in the field of foreign-related civil and commercial affairs.展开更多
基金the National Natural Science Foundation of China(NSFC,Nos.22071247,92156010,22101283,and 22101284)the Key Research Program of Frontier Sciences(No.QYZDBSSW-SLH030)of the CAS+1 种基金Natural Science Foundation of Fujian Province(Nos.2020J06035 and 2022J05085)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZR112)for support.
文摘Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.
文摘Amino group protective strategy has consequently emerged in multistep organic synthesis.Easy and selective deprotection procedures are crucial to facilitate the chemical transformation.Recently,Zhang’s group from Henan Normal University collaborating with Chen’s group of Nankai University developed a novel strategy for the regiospecific cleavage of inert aryl C-N bonds in N-aryl amides by hypervalent iodine(V)reagents.These procedures allow removal of sort of aryl groups under mild conditions to give primary amides in high efficiency.It bestows these aryl groups with the characteristics of amino protecting groups that might be the supplement of amino protecting group chemistry.
文摘The confrontation between the disadvantaged and advantaged groups is eternal throughout the competition for survival. But the human spiritual world has its humane aspect in addition to competition. The concern for and protection of the disadvantaged group is the moral law characteristic of humanity, just as the Universal Declaration of Human Rights says in its Article 1： ＂All human beings are born free and equal in dignity and rights.
基金sponsored by grants from the National Natural Science Foundation of China(Nos.22322301,22303046)the Shaanxi Science Fund for Distinguished Young Scholars(No.2021JC-38)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.GK202207001,GK202304008)the Shaanxi Province Postdoctoral Science Foundation(No.2023BSHEDZZ187).
文摘Aryl ketones as photolabile protecting group(PPG)to modify purine imines is a novel nucleic acid protection strategy.Especially,photoprotection of N7-guanosine is the first reported photoprotected nucleoside that can affect the Hoogsteen recognition site of guanosine.However,the mechanism,which is pivotal to high efficiency of photorelease and applications of PPGs in biological and medical systems,is unclear.Here,a detailed deprotection mechanism of benzophenone protected guanosine(BP-Guo)at N7 position is reported.Upon irradiation,BP-Guo populates to singlet state,which generates^(3)[BP]-Guo via intersystem crossing process.Thereafter,triplet energy transfer competes with hydrogen atom transfer forming BP-^(3)[Guo]and ketyl-Guo,respectively.Both species break C–N bond to release guanosine.These results provide deeper insights into exploiting improved strategies for photo-protecting nucleic acids.In particular,the TTET pathway could trigger well-known cyclization reactions that brings about DNA mutagenic adducts.The latter should be avoided in developing improved strategies for photoprotecting nucleic acids.
文摘Protecting groups often play an essential role in organic synthesis, particularly for multi-step synthesis or natural product total synthesis. Various protecting groups areavailable to mask the vulnerable functionality;phenolic hydroxy groups are noteworthy examples, but their stability differs when protected. Herein, the compatibility of protective phenolic functionality was investigated with the implementation of indium (III) triflate-catalyzed oxidative esterification using Oxone in methanol. A wide range of protective moieties was selected and subjected to Oxone-mediated oxidative esterification. For example, sulfonates were found to be sufficiently stable and inert whereas acetals were susceptible to reaction conditions. The details of this investigation are provided.
基金the National Natural Science Foundation of China(No.20533010,20673039)the Science&Technology Commission of Shanghai Municipality(No.06JC14023)for financial support.
文摘A new IL-supported diol, 1-（2,3-dihydroxypropyl）-3-methylimidazolium hexafluorophosphate has been synthesized and characterized by Fr-IR, ^1H NMR, ^13C NMR and MS （ESI）. Its physical properties such as freezing point, solubility and specific gravity and thermal stability were determined. Synthetic utilities of the resultant diol as a protecting group for aldehydes were also investigated.
基金The project is supported by the National Natural Science Foundation of China.
文摘A novel polymer-bound 1,2-diol, 3-polystyrylsulfonyl-1,2-propanediol (6) had been prepared by the reaction of sodium polystyrylsulfinate with allyl bromide, followed by oxidation and. hydrolysis or directly with 3-chloro-1,2-propanediol in the presence of a phase transfer catalyst, n-tetrabutylammonium iodide. The capacity of resin 6 for terephthaidehyde reached 1.43 mmol/g. The aldehydic groups attached to polymer 6 reacted with hydroxylamine hydrochloride or reduced by sodium borohydride giving p-formylbenzaldoxime (yield: 89%)and p-formyl-benzalcohol (yield: 734%), respectively. The high yields of these polymer-supported reactions showed that the polymer 6 possessed the effective isolation of its reactive sites.
文摘In the course of organic synthesis, particularly for multi-step synthesis or natural product total synthesis, the selection of appropriate protective groups for the intended functionality is crucial in order to achieve chemoselective synthetic goals. The development of many useful protective groups has been reported based on the functionality of the anilino group. Herein, we discuss our study of various protective groups and the processes we used to establish compatibility with anilino functionality via the implementation of Oxone-mediated oxidative esterification in methanol. The results and the details of our experiments are reported herein.
文摘On March 19, an academic forum was held in Jinan City, Shandong Province, on protection of vulnerable groups’ rights. Sponsored by the Law School of Shandong University, it gathered some 50 experts from the Central Patty School, Chinese Academy of Social Sciences, China Society for Human Rights Studies, Shandong Higher People’s Court, as well as some research universities in the country. Four subjects were discussed at the forum: definition of vulnerable groups, legal principles for protection of vulnerable groups’
文摘In recent years,the use of light to selectively and precisely activate drugs has been developed along the fundamental concepts of photopharmacology.One of the key methods in this field relies on transiently silencing the drug activity with photocleavable protecting groups(PPGs).To effectively utilize light-activated drugs in future medical applications,physicians will require a reliable method to assess whether light penetrates deep enough into the tissues to activate the photoresponsive theragnostic agents.Here,we describe the development and evaluation of magnetic resonance(MR)imaging agents that allow for the detection of light penetration and drug activation in the tissues using non-invasive whole-body magnetic resonance imaging(MRI)and chemical exchange saturation transfer(CEST)-MRI modalities.The approach relies on the use of PPG-protected MR contrast agents,which upon irradiation with light change their imaging signal.A Gadolinium(III)-based MRI contrast agent is presented that undergoes a significant change in relaxivity(25%)upon uncaging,providing a reliable indicator of lightinduced cargo release.Additionally,we introduce the first light-responsive CESTMRI imaging agent,enabling positive signal enhancement(off-to-on)upon light activation,offering a novel approach to visualize the activation of photoactive agents in living tissues.This research provides a proof-of-principle for the noninvasive,whole-body imaging of light penetration and drug activation with high temporal resolution characteristic of MR methods.
基金support from the National Natural Science Foundation of China(22071054,21871081)the Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism(Shanghai Municipal Education Commission)the Taishan IndustrialExperts Program(tscx202312168))is ggratefully acknowledged.
文摘Traditional protecting groups are often removed under harsh conditions with potentially hazardous reagents,thereby impeding the convenient synthesis of oligosaccharides and glycosides.Herein,we present to utilize the photolabile ortho-nitro-benzyl carbonate(oNBC)as a permanent hydroxyl protecting group for stereocontrolled synthesis of glycosides.The Ph3PO-modulated glycosylation with strongly disarmed per-O-oNBC-protected glycosyl ynenoates preferred to afford glycosides with excellentα-selectivities via theβ-phosphonium transition state.Based on the oNBC-mediated galactosylation,synthesis of the glycolipid digalactosyl diacylglycerol(DGDG)containing six double bonds and two esters was achieved in a straightforward manner.
文摘Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.
文摘Aim To synthesize the tripepide Weinreb amide Boc Asp(OBzl) β Ala Asp(OBzl) N(OMe)Me (7) as a useful precursor of aspartyl peptide aldehyde derivatives; Methods DCC, IBCF method was used for preparation of Weinreb amide; N hydroxysuccinimide activated ester was used in peptide synthesis; and Boc as N protecting group of amino acid. Results Boc Asp(OBzl) N(OMe)Me (3), Boc β Ala Asp(OBzl) N(OMe)Me (5), and Boc Asp(OBzl) β Ala Asp(OBzl) N(OMe)Me (7) were synthesized successfully. Conclusion An useful precursor of tripeptide aspartyl aldehydes was synthesized.
基金This work was financially supported by the Natural Science Foundation of China(Nos.21877039,32072441)National Key Research and Development Program of China(No.2018YFD0200100)Innovation Program of Shanghai Municipal Education Commission(No.2017-01-07-00-02-E00037).
文摘Precise and spatiotemporal control over the pesticide remains to be a challenge.More efficient controlled release systems(CRSs)have been developed to support the precise delivery of active ingredients.Herein,we incorporated the photoremovable protecting groups(PRPGs)into phenamacril(PHE)and obtained two photo-responsive fungicides of NV-PHE and DEACM-PHE.The 4,5-dimethoxy-o-nitrobenzyl(NV)or 7-diethylaminocoumarin(DEACM)-caged PHE could release the active molecule PHE after irradiation of UV light and blue light,respectively.Optical properties and in-vitro/vivo fungicidal activities of NV-PHE and DEACM-PHE demonstrated the feasibility for light controlled release of PHE.DEACM-PHE could release 98%PHE by illumination of blue light.The irradiated DEACM-PHE could preserve the similar bioactivity of PHE,and significantly improve the in-vitro/vivo fungicidal activities compared to the non-irradiated DEACM-PHE.The optical controlled release of PHE from DEACM-PHE enabled the precise and spatiotemporal delivery of PHE,diversifying the development of CRSs for pesticide,and providing environmentfriendly agricultural applications with high pesticide efficiency.
文摘Various alcohols and phenols were trimethylsilylated in excellent yields using hexamethyldisilazane in the presence of catalytic amounts of environmentally friendly, hydrophobic, highly thermal stable, and completely heterogeneous sulfonic acid functionalized mesostructured SBA-15 in dichloromethane at ambient temperature. Primary, bulky secondary, tertiary, and phenolic hydroxyl functional groups were transformed to the corresponding trimethylsilyl ethers in excellent yields. The simple experimental procedure was accompanied by easy recovery and the catalyst was reusable (at least 18 reaction cycles); these are attractive features of this protocol.
基金supported by the National Key R&D Program of China(2018YFA0902200)the National Natural Science Foundation of China(22278224,21978131 and 21878156)+1 种基金the Natural Science Foundation of Jiangsu Province(BK20200691)the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Photocages are a class of substances containing photosensitive groups,also known as“photoremovable protecting groups”,from which target substances are released upon exposure to specific wavelengths of light.The substances released in the light-promoted processes have chemical or biological properties that enable them to carry specifically designed functions.As a result,photocages can be utilized in various fields such as chemistry,biology,and medicine.In this paper,progress made in research carried out in recent years aimed at developing photocage molecules with different photosensitive moieties is reviewed.
文摘Semi-synthesis of paclitaxel was achieved in four steps from 10-deacetylbaccatin HI （10-DAB HI）. The key steps are the regioselective protection at the hydroxyl group at C-7 of 10-DAB HI, using 1,1′-thiocarbonyldiimidazole as a selective reagent, and the deprotection of the protected paclitaxel with a mixture of p-toluenesulfonic acid and 0.1 mol/L aqueous hydrochloride.
文摘Selective protection of one of the hydroxyl group in 1, n-symmetrical diols is achieved by P2O5/SiO2-catalyzed reaction of the diol with dihydropyran under solvent-free conditions at room temperature. This selective protection is simple and it occurred under economically cheap conditions in high yield. The deprotected diol is simply obtained by refluxing of this compound in methanol using the same catalyst without any byproduct formation or additional purifications.
基金the Razi University Research Council for partial support of this work
文摘A simple and efficient protocol for the deprotection of dithioacetal,1,3-dithianes and 1,3-dithiolanes has been developed using H_2O_2-SOC1_2 reagent system.In addition to the absence of overoxidation products for oxidation-prone substrates,high chemoselectivity, the low cost and availability of the reagents,simplicity of the method,short reaction times,and excellent yields can also be considered as strong points for this method.
基金the National Social Science Fund Major Project“Research on the Construction of Systems Applicable Outside the Chinese Jurisdiction in the Perspec-tive of Private International Law”(Project Approval Number 20&ZD202)the National Social Science Fund Key Project“Empirical Research on Judges’Discretion in Foreign-related Civil Trials in China”(Project Approval Number 19AFX026).
文摘Personality rights are basic rights related to human dignity in the concept of human rights protection,and respect for personality rights is the basic prerequisite for safeguarding other human rights.Human rights protection exerts a profound impact on the value of legislation and enforcement practices of private international laws in the field of cross-border personality rights infringement in various countries,which is mainly manifested in the integration of substantive justice and the humanistic care concept of protecting the rights of vulnerable groups into formal justice,and expands the development space of human rights protection ideas in cross-border personality rights and tort conflict laws.the diversity of human rights protection values determines that cross-border personality rights infringement may lead to conflicts between personality rights and other basic rights,such as freedom of speech.to reconcile such conflicts,a workable method is to prioritize personality rights protection in accordance with the hierarchy of rights theory in the value judgment of public order reservation or to clarify the limits of the right holder’s tolerance obligation through the limited application of the principle of proportionality.China’s current cross-border personality rights and tort conflict law can optimize the protection of the rights of vulnerable groups by diversifying the options of available legal methods,and establish a balancing mechanism between personality rights and freedom of speech,so as to improve China’s legal protection system for human rights in the field of foreign-related civil and commercial affairs.
