미끄러운 바위 대학에서 제공하는 자금. 우리는 그들의 통찰력 T 보론 III (미끄러운 바위 대학)와 C하니 (펜실베니아 대학)에 감사드립니다.

니켈 쉬프-자료 단지 1. 가수 분해 <ol><li> 실온에서 250 mL의 둥근 바닥 플라스크를 교반하면서 N, N- 디메틸 포름 아미드 (DMF) 40 mL를 상기의 Ni-PBP - 쉬프 염기 착체 1 밀리몰 녹인다. </li><li> 수성 0.2 M EDTA 용액의 pH 4.5의 60 mL를 넣고. </li><li> 자기 교반 막대를 이용하여 플레이트를 교반 밤새 합성 용액을 교반한다. 쉬프 염기 복합 가수 분해로, 색상은 흰색에 깊은 적색에서 이동합니다. </li><li> 모든 적색 착색의 부재에 의해 나타낸 바와 같이, 반응 종결 후, 250 mL의 분액 깔때기에 반응 옮긴다. </li><li> 50 mL의 디클로로 메탄을 추가 분액 깔때기 캡 섞는다. 폐기물 비이커에 유기 세정 배수. PBP 및 잔여 니켈 PBP-쉬프 염기 단지를 제거하려면이 과정을 세 번 반복합니다. 250 mL의 둥근 바닥 플라스크에 남아있는 수성 층을 수집. </li></ol> 가수 분해 아미노산의 2 FMOC 보호 <ol><li&gt; 고체 중탄산 나트륨을 사용하여 pH 7로 상술 한 단계 150에서 분리 된 수성층을 조정한다. pH가 정기적으로 산도 테스트 스트립을 사용하여 확인합니다. </li><li> 용액에 168 mg의 탄산 수소 나트륨 (2.00 밀리몰, 2 당량)을 첨가하고 자기 교반 막대를 이용하여 교반하고 플레이트를 교반한다. </li><li> 10 ML 비얼에서 디 옥산 최소량 (약 4-5 ㎖)에 337 mg의 N의 FMOC -hydroxysuccinimide 에스터 (1.00 밀리몰, 1 당량)을 녹인다. 수용액이 용액을 전송하고, 밤새 교반 하였다. </li><li> 반응물을 밤새 교반시킨 후, 1 M 염산으로 pH 2로 생성 된 용액을 산성화. pH가 정기적으로 산도 테스트 스트립을 사용하여 확인합니다. </li><li> 250 ㎖의 분액 깔때기에 옮기고, 반응을 50 ㎖의 에틸 아세테이트를 추가한다. 상기 분별 깔때기 캡 잘 혼합하고, 250 mL의 삼각 플라스크에 유기층을 수집한다. 유기 추출물을 결합,이 과정을 두 번 더 추가를 반복합니다. 마그네슘 sulfat 대략 3g 합한 유기 추출물을 건조이자형. </li><li> 조 FMOC 보호 된 아미노산을 수득하는 회전 증발기를 사용하여 합한 유기 추출물을 농축시킨다. </li></ol>

<ol>
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저자가 공개하는 게 없다.

상기 프로토콜은 두 가지 중요한 단계를 중성 pH 조건이 절연 아미노산 후속 FMOC 보호 하에서 니켈 쉬프 염기 착체의 아미노산 골격의 분리를 촉진하는 능력에 유용하다. 첫 번째 단계는 복잡에서 아미노산의 방출을 용이하게하기 위해 EDTA를 함유하는 DMF / 물 용액을 교반 포함한다. 잔류 착체 또는 유기 부산물 쉽게 추출하여 제거 될 수있다. 이 프로토콜의 두 번째 단계에서는 첫 번째 단계에서 ?...

자연에서 발견 스물 개 자연적으로 발생하는 아미노산과 다를 자연스러운 아미노산 (UAA의) 베어링 측쇄 응용 프로그램의 넓은 범위에서 유틸리티를 발견했다. 이러한 UAA 년대의 합성 단, 측쇄의 구조 및 아미노산 주쇄의 입체 화학에 따라 어려울 수있다. 니켈 쉬프 염기 착체의 맥락에서 글리신의 크 본드 활성은 α, β 디아 미노 산 1, 2 또는 헤테로 측쇄 플루오르 UAA의 베어링을 포함한 아미노산 유도체의 다양성을 생성하기 위해 사용되었다. 삼 비 천연 측쇄를 첨가 한 후, UAA의 전형적 염산 (4)에 환류하여 쉬프 염기 착체로부터 제거하고,이어서 이온 교환 크로마토 그래피를 사용하여 분리되어 기능화. 일반적으로 효율적이지만,이 프로토콜은 발생고상 펩티드 합성 (SPPS)에서 사용되기에 부적합 할 수있다 미노 산. SPPS의 자연 그대로 이들 보호기의 UAA와의 분리를 방지 산해리 측쇄 보호기의 존재 및 일반적인 니켈 쉬프 염기 분해 조건 강산성 성질을 필요로한다. 우리의 지식으로, 단 하나의 대체 분해 방법이보고되어있다 : 에틸렌 디아민 테트라 아세트산 (EDTA) 및 하이드라진을 사용 승온에서, 그 자체가 몇몇 측쇄는 프탈이 미드로서 보호기에 적합하지 않을 수 5 조건있다. <img alt="그림 1" src="/files/ftp_upload/55677/55677fig1.jpg" /> 도 1 : 니켈 2+, PBP, 글리신 (의 Gly)에서 니켈의 Gly-PBP의 합성. <a href="http://ecsource.jove.com/files/ftp_upload/55677/55677fig1large.jpg" target="_blank">이 그림의 더 큰 버전을 보려면 여기를 클릭하십시오.</a> </A&gt; 여기서 우리는, 니켈의 Gly-PBP (도 1) 니켈 쉬프 염기 착체의 가수 분해하는 방법을보고한다. 니켈 2+, 글리신, 및 피리딘 -2- 카르 복실 산 (2- 벤조일 페닐) - 아마이드 (PBP), 6 유래의이 복합체는 UAA의 다양한 합성에 유용한 플랫폼 증명 용이하다되었습니다 액세스 두 단계의 합성 경로를 사용. 이러한 착체의 합성 문헌 (7) - 이미 기재 고 수율이다. 우리의 결과는 6 이하의 UAA 베어링 산해리 측쇄가 보호기와 사용에 적합한 중성 pH 조건 약산성에서 EDTA를 이용하여 가수 분해 조건의 적용을 보여준다. 가수 분해 후, 생성 된 수성 용액을 분리 할 수 있고 FMOC 보호 된 아미노산을 수득 표준 FMOC 보호 상태 (도 2)에 즉시 실시. 그림 2 : 가수 분해 및 Ni-PBP-의 Gly에서 고립 된 아미노산의 FMOC 보호. 반응 조건 : 전. EDTA (12 당량), 4.5의 pH; II. pH 7로 세척하고 아세트산 에틸 조정; III. FMOC - 오스 (1 당량)의 NaHCO3 (2 당량). <a href="http://ecsource.jove.com/files/ftp_upload/55677/55677fig2large.jpg" target="_blank">이 그림의 더 큰 버전을 보려면 여기를 클릭하십시오.</a>

<table><tbody><tr><td>Ni-PBP-Gly</td><td></td><td></td><td>Synthesized from published protocol</td></tr><tr><td>DMF</td><td>Fisher</td><td>D119-4</td><td></td></tr><tr><td>EDTA</td><td>Fisher</td><td>S311-100</td><td></td></tr><tr><td>Dichloromethane</td><td>Acros</td><td>AC610050040</td><td></td></tr><tr><td>Sodium Bicarbonate</td><td>Fisher</td><td>S233-500</td><td></td></tr><tr><td>Fmoc-OSu</td><td>Chem-Impex</td><td>&quot;00147&quot;</td><td></td></tr><tr><td>Dioxane</td><td>Fisher</td><td>D111-500</td><td></td></tr><tr><td>Hydrochloric Acid</td><td>Fisher</td><td>A144-500</td><td></td></tr><tr><td>Ethyl Acetate</td><td>Acros</td><td>AC610060040</td><td></td></tr><tr><td>Magnesium Sulfate</td><td>Fisher</td><td>M65-500</td><td></td></tr><tr><td>ZEOPrep 60ECO Silica Gel</td><td>ZEOChem</td><td></td><td></td></tr><tr><td>Hexanes</td><td>Fisher</td><td>3200250.650.443</td><td></td></tr><tr><td>Chromatography Column</td><td></td><td></td><td></td></tr><tr><td>pH Test Strips</td><td></td><td></td><td></td></tr><tr><td>Rotary Evaporator</td><td></td><td></td><td></td></tr><tr><td>250 mL Separatory Funnel</td><td></td><td></td><td></td></tr><tr><td>250 mL Round Bottom Flask</td><td></td><td></td><td></td></tr><tr><td>Stir Bar</td><td></td><td></td><td></td></tr><tr><td>Stir Plate</td><td></td><td></td><td></td></tr></tbody></table>

hydrolysis of a ni-schiff-base complex using conditions suitable for retention of acid-labile protecting groups

비 천연 아미노산은 일반적으로 자연에서 보지 측쇄 작용기를 함유하는 아미노산 점점 합성 펩티드 서열에서 발견된다. 몇몇 비 천연 아미노산의 합성은 종종 니켈 양이온에 의해 안정화 쉬프 염기로 이루어지는 전구체의 사용을 포함한다. 비정상적인 측쇄이 쉬프 염기 착체에서 발견되는 아미노산 골격 상에 설치 될 수있다. 생성 된 비 천연 아미노산은 전형적 강산성 용액으로 환류를 이용하여, 쉬프 염기의 복잡한 분리하여 가수 분해 될 수있다. 비 천연 아미노산은 마이크로파를 이용한 고상 펩티드 합성에 사용되는 이러한 강산성 조건 산해리 필요한 측쇄 보호기를 제거 할 수있다. 본 연구에서, 우리는 효율적인 가수 분해 및 니켈 쉬프 염기 착체로부터 분리 아미노산 후속 FMOC 보호를 제시한다. 본 연구에 제시된 가수 분해 조건은 산해리의 유지에 적합IDE 쇄 보호기 및 비 천연 아미노산의 다양한 기판에 적용 할 수있다.

우리는 가혹한 pH 조건 없이도 쉬프 염기의 수성 가수 분해 효율을 허용 할 수있는 니켈의 Gly-PBP 복합체에서의 Ni 2+의 제거를 가정. EDTA가 저렴하고 잘 연구 킬레이트 제이기 때문에, 10 우리는 니켈 PBP-의 Gly의 용액에 EDTA를 첨가함으로써 복합체의 분해를 촉진 니켈 2+ 이온의 킬레이트 화를 촉진한다고 가정 하였다. <p class="jove_content" fo:...

Watch this Scientific Journal Video about Hydrolysis of a Ni-Schiff-Base Complex Using Conditions Suitable for Retention of Acid-labile Protecting Groups at JoVE.com

Hydrolysis of a Ni-Schiff-Base Complex Using Conditions Suitable for Retention of Acid-labile Protecting Groups

여기서, 우리는 효율적인 가수 분해 및 니켈 쉬프 염기 착체로부터 분리 아미노산 후속 FMOC 보호를 제시한다. 산해리 측쇄 보호기의 유지가 요구되는 경우 여기 제시된 가수 분해 조건을 사용하기에 적합하다. 이 기술은 천연 아미노산의 다양한 기판에 적용 할 수있다.

보호 그룹 산 - 불안정의 보존에 적합한 니켈 쉬프 - 자료의 가수 분해 복잡한 사용 조건

Unnatural amino acids, amino acids containing side-chain functionalities not commonly seen in nature, are increasingly found in synthetic peptide ...

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JoVE Journal

Biochemistry

9.6K 조회수.  Slippery Rock University.  여기서, 우리는 효율적인 가수 분해 및 니켈 쉬프 염기 착체로부터 분리 아미노산 후속 FMOC 보호를 제시한다. 산해리 측쇄 보호기의 유지가 요구되는 경우 여기 제시된 가수 분해 조건을 사용하기에 적합하다. 이 기술은 천연 아미노산의 다양한 기판에 적용 할 수있다. 

비디오: Hydrolysis of a Ni-Schiff-Base Complex Using Conditions Suitable for Retention of Acid-labile Protecting Groups

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the hydroxylmethylene phosphine precursor with ammonia in methanol under a nitrogen atmosphere. The N-triphosPh ligand precipitates from the solution after approximately 1 hr of reflux and can be isolated analytically pure via simple cannula filtration procedure under nitrogen. Reaction of the N-triphosPh ligand with [Ru3(CO)12] under reflux affords a deep red solution that show evolution of CO gas on ligand complexation. Orange crystals of the complex [Ru(CO)2{N(CH2PPh2)3}-&#954;3P] (2) were isolated on cooling to RT. The 31P{1H} NMR spectrum showed a characteristic single peak at lower frequency compared to the free ligand. Reaction of a toluene solution of complex 2 with oxygen resulted in the instantaneous precipitation of the carbonate complex [Ru(CO3)(CO){N(CH2PPh2)3}-&#954;3P] (3) as an air stable orange solid. Subsequent hydrogenation of 3 under 15 bar of hydrogen in a high-pressure reactor gave the dihydride complex [RuH2(CO){N(CH2PPh2)3}-&#954;3P] (4), which was fully characterized by X-ray crystallography and NMR spectroscopy. Complexes 3 and 4 are potentially useful catalyst precursors for a range of hydrogenation reactions, including biomass-derived products such as levulinic acid (LA). Complex 4 was found to cleanly react with LA in the presence of the proton source additive NH4PF6 to give [Ru(CO){N(CH2PPh2)3}-&#954;3P{CH3CO(CH2)2CO2H}-&#954;2O](PF6) (6).

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Ruthenium phosphine complexes are widely used for homogeneous catalytic reactions such as hydrogenations. The synthesis of a series of novel tridentate ruthenium complexes bearing the N-triphos ligand N(CH2PPh2)3 is reported. Additionally, the stoichiometric reaction of a dihydride Ru&#8211;N-triphos complex with levulinic acid is described.

루테늄의 시리즈의 합성, 특성 및 반응성<em&gt; N</em&gt; -triphos<sup&gt; 박사</sup&gt; 단지

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the ...

연구

화학

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, &#60;10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 &#176;C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol&#183;g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(&#8801;Si-O-)Hf(&#951;2&#960;-MeNCH2)(&#951;1-NMe2)(&#951;1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)]. [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is correlated to the catalytic performance.

A new group IV metal catalyst for imine metathesis is prepared by grafting amine metal complex onto dehydroxylated silica. Surface metal fragments are characterized using FT-IR, elemental microanalysis, and solid-state NMR spectroscopy. Further dynamic nuclear polarization surface enhanced NMR spectroscopy experiments complement the determination of the coordination sphere.

표면 유기 금속 화학의 방법론을 사용하여 실리카 지원 촉매에 의해 이민 대사

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared ...

Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase

Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each possessing two sulfur and one nitrogen donor atom functionalities (SNS) and based on bis-imidazole or bis-triazole compounds) are metallated with CoCl2&#183;6H2O to afford tridentate SNS pincer cobalt(II) complexes. Preparation of the cobalt(II) model complexes for liver alcohol dehydrogenase is facile. Based on a quick color change upon adding the CoCl2&#183;6H2O to acetonitrile solution that contains the ligand precursor, the complex forms rapidly. Formation of the metal complex is complete after allowing the solution to reflux overnight. These cobalt(II) complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH). The complexes are characterized using single crystal X-ray diffraction, electrospray mass spectrometry, ultra-violet visible spectroscopy, and elemental analysis. To accurately determine the structure of the complex, its single crystal structure must be determined. Single crystals of the complexes that are suitable for X-ray diffraction are then grown via slow vapor diffusion of diethyl ether into an acetonitrile solution that contains the cobalt(II) complex. For high quality crystals, recrystallization typically takes place over a 1 week period, or longer. The method can be applied to the preparation of other model coordination complexes and can be used in undergraduate teaching laboratories. Finally, it is believed that others may find this recrystallization method to obtain single crystals beneficial to their research.

Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase

The preparation of SNS pincer cobalt(II) model complexes of liver alcohol dehydrogenase is presented here. The complexes can be prepared by reacting the ligand precursor with CoCl2&#183;6H2O and can then be recrystallized by allowing diethyl ether to slowly diffuse into an acetonitrile solution that contains the cobalt complex.

SNS 코발트(II) 간알코올탈수소효소의 집게 모델 복합체 의 제조

Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each ...

Targeted Antibody Blocking by a Dual-Functional Conjugate of Antigenic Peptide and Fc-III Mimetics (DCAF)

Elimination of harmful antibodies from organisms is a valuable approach for the intervention of antibody-associated diseases, such as Dengue hemorrhagic fever and autoimmune diseases. Since thousands of antibodies with different epitopes are circulating in blood, no universal method, except for the dual-functional conjugate of antigenic peptide and Fc-III mimetics (DCAF), was reported to target specific harmful antibodies. The development of DCAF molecules makes significant contribution to the progress of targeted therapy, which were demonstrated to eliminate the antibody dependent enhancement (ADE) effect in a Dengue virus (DENV) infection model and to boost the acetylcholine receptor activity in a myasthenia gravis model. Here, we describe a protocol for the synthesis of a DCAF molecule (DCAF1), which can selectively block 4G2 antibody to attenuate ADE effect during Dengue virus infection, and illustrate the binding of DCAF1 to 4G2 antibody by an ELISA assay. In our method, DCAF1 is synthesized by the conjugation of a hydrazine derivative of a Fc-III peptide and a recombinant expressed long &#945;-helix with antigenic sequence through native chemical ligation (NCL). This protocol has been successfully applied to DCAF1 as well as other DCAF molecules for targeting their cognate antibodies.

Targeted Antibody Blocking by a Dual-Functional Conjugate of Antigenic Peptide and Fc-III Mimetics DCAF

Development of a dual-functional conjugate of antigenic peptide and Fc-III mimetics (DCAF) is novel for the elimination of harmful antibodies. Here, we describe a detailed protocol for the synthesis of DCAF1 molecule, which can selectively block 4G2 antibody to eliminate antibody dependent enhancement effect during Dengue virus infection.

항원 펩타이드 및 Fc-III 모방제(DCAF)의 이중 기능 성 컨쥬게이트에 의한 표적 항체 차단

Elimination of harmful antibodies from organisms is a valuable approach for the intervention of antibody-associated diseases, such as Dengue hemorrhagic ...

면역학 및 감염병학

Molecular Orbital (MO) Theory

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
This protocol serves as a guide in the synthesis of two metal complexes featuring the ligand 1,1&#39;-bis(diphenylphosphino)ferrocene (dppf): M(dppf)Cl2, where M = Ni or Pd. While both of these transition metal complexes are 4-coordinate, they exhibit different geometries at the metal center. Using molecular orbital (MO) theory in conjunction with 1H NMR and Evans method, we will determine the geometry of these two compounds.

Molecular Orbital MO Theory: Predicting Geometry of Transition Metal Complexes

분자 궤도 (MO) 이론

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University
This protocol serves as a guide in the synthesis of two metal complexes ...

교육

JoVE Science Education

무기 화학

Preparation of Carboxylic Acids: Hydrolysis of Nitriles

Nitriles (R&#8211;CN) can be converted into carboxylic acids (R&#8211;COOH) upon treatment with aqueous acids, i.e., upon hydrolysis of nitriles. Under base-catalyzed conditions, carboxylate anions (R&#8211;COO&#8722;) are formed.
<img alt="Figure1" src="/files/ftp_upload/13085/13085_PT_Figure_1.svg" style="text-align: center; height: 56px;" />
The reaction facilitates a two-step conversion of haloalkanes to carboxylic acids. Here, haloalkanes are first converted to nitriles using sodium cyanide via an SN2 reaction. The resultant nitrile is then hydrolyzed to yield carboxylic acids bearing one more carbon than the haloalkane used. The reaction uses dimethyl sulfoxide, alcohols, or water as solvents. As the process involves the SN2 mechanism, tertiary alkyl halides are seldom used.
<img alt="Figure2" src="/files/ftp_upload/13085/13085_PT_Figure_2.svg" style="text-align: center; height: 46px;" />

카르복실산의 제조: 니트릴의 가수분해

Nitriles (R&#8211;CN) can be converted into carboxylic acids (R&#8211;COOH) upon treatment with aqueous acids, i.e., upon hydrolysis of nitriles. Under ...

JoVE Core

유기화학

Unit 1

Carboxylic Acids

주요 용어 및 개념

Protection of Alcohols

This lesson delves into the concept of protection and deprotection of a functional group fundamental to synthetic organic chemistry. These phenomena are explained in the context of aliphatic and aromatic alcohols.
<h4>Protection</h4>
It defines a protecting group as the masking agent to make the more reactive species inert to a given set of conditions. This concept is depicted via the illustration of liquid flow through different outlets in an assembly of pipes. The analogy helps to understand the role of a protecting group in reaction selectivity, as in the case of the organolithium alkylation of a halide in the presence of a competing acidic alcohol group. The example shows how protection of the alcohol group helps to achieve the alkylation of the halide. Popular protecting groups for alcohols include the trialkylsilyl family for nucleophiles or carbon and nitrogen bases and the tetrahydropyranyl (THP) group for strong bases. In the former example, the halide of the trialkylsilyl derivative reacts with the alcohol in the presence of a nucleophilic catalyst to generate a trialkylsilyl ether.
<h4>Deprotection</h4>
Every protection is followed by deprotection after the intended reaction. The deprotection restores the system to its native state. In protection with trialkylsilyl groups, deprotection is achieved using fluoride salts like tetra-n-butylammonium fluoride (TBAF) that are soluble in organic solvents. Here, the re-protonation of the oxygen regenerates the native alcohol. In the case of protection with THP, deprotection is achieved using acid hydrolysis.
<h4>Principle of design</h4>
The lesson also elucidates the principles behind the design of a protecting group using an illustration of a house under varying external weather conditions. It demonstrates the selectivity offered by a protecting group in a specific environment. For instance, THP protects alcohol from strong bases. The acetal formed in this case is stable towards bases but susceptible to acid hydrolysis.
Apart from the reaction conditions, the reactivity of the molecule to be protected also plays a key role in designing a suitable protecting group. For example, methyl ethers&#8217; ability to protect phenols is found inappropriate for aliphatic alcohols. Here, the stability of the corresponding leaving groups during deprotection plays a key role. For example, the alkoxides, unlike phenoxides, are poor leaving groups for deprotection with hydrogen bromide.
The following table summarizes the various protection/deprotection groups for different types of alcohols and related conditions:
<table style="margin-left: auto; margin-right: auto;">
	<tbody style="border: 1px solid black;">
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Protecting group</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Structure</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Protects</td>
			<td style="color: black; border: 1px solid black; text-align: center;">From</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Protection</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Deprotection</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Trialkylsilyl (R3Si&#8211;), 
			e.g., TBDMS</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Me3Si&#8211;OR 
			(Me3C)Me2Si&#8211;OR</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Alcohols 
			(OH in general)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Nucleophiles, 
			C or N bases</td>
			<td style="color: black; border: 1px solid black; text-align: center;">R3SiCl, 
			base</td>
			<td style="color: black; border: 1px solid black; text-align: center;">H+, H2O, 
			or F&#8722;</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Tetrahydropyranyl 
			(THP)</td>
			<td style="color: black; border: 1px solid black; text-align: center;"><img alt="Figure1" src="/files/ftp_upload/11927/Figure_1-11927.svg" style="text-align: center; height: 50px;" /></td>
			<td style="color: black; border: 1px solid black; text-align: center;">Alcohols 
			(OH in general)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Strong bases</td>
			<td style="color: black; border: 1px solid black; text-align: center;">3,4-Dihydropyran, 
			H+</td>
			<td style="color: black; border: 1px solid black; text-align: center;">H+, H2O</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Benzyl ether 
			(OBn)</td>
			<td style="color: black; border: 1px solid black; text-align: center;"><img alt="Figure2" src="/files/ftp_upload/11927/Figure_2-11927.svg" style="text-align: center; height: 50px;" /></td>
			<td style="color: black; border: 1px solid black; text-align: center;">Alcohols 
			(OH in general)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Almost everything</td>
			<td style="color: black; border: 1px solid black; text-align: center;">NaH, BnBr</td>
			<td style="color: black; border: 1px solid black; text-align: center;">H2, Pd/C, 
			or HBr</td>
		</tr>
		<tr>
			<td style="color: black; border: 1px solid black; text-align: center;">Methyl ether 
			(ArOMe)</td>
			<td style="color: black; border: 1px solid black; text-align: center;"><img alt="Figure3" src="/files/ftp_upload/11927/Figure_3-11927.svg" style="text-align: center; height: 50px;" /></td>
			<td style="color: black; border: 1px solid black; text-align: center;">Phenols 
			(ArOH)</td>
			<td style="color: black; border: 1px solid black; text-align: center;">Bases</td>
			<td style="color: black; border: 1px solid black; text-align: center;">NaH, MeI, or 
			(MeO)2SO2</td>
			<td style="color: black; border: 1px solid black; text-align: center;">BBr3, HBr, HI, 
			Me3SiI</td>
		</tr>
	</tbody>
</table>

Protection and Deprotection of Alcohols and Phenols

알코올 보호

This lesson delves into the concept of protection and deprotection of a functional group fundamental to synthetic organic chemistry. These phenomena are ...

Alcohols and Phenols

Acid Halides to Carboxylic Acids: Hydrolysis

Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon&#8211;oxygen &#960; bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid as the substitution product.&#160;
<img alt="Figure1" src="/files/ftp_upload/12361/12361_PT_Figure_1_.svg" style="text-align: center; height: 200px;" />
The reaction produces a very strong acid, HCl, as a by-product. Therefore, a base such as pyridine is used in the reaction, which reacts with HCl to form pyridinium chloride. This process neutralizes the acid and prevents undesired side reactions.

산 할로겐화물에서 카르복실산으로: 가수분해

Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction ...

Carboxylic Acid Derivatives

Acetals and Thioacetals as Protecting Groups for Aldehydes and Ketones

Acetals are formed by reacting two equivalents of alcohol with carbonyl compounds like aldehydes or ketones. Acetals are unaffected by bases, nucleophiles, oxidizing agents, and reducing agents. They serve as protecting groups for aldehydes and ketones. Acetals can be easily formed and also easily removed via mild acid hydrolysis.
In the presence of multiple functional groups, when selective reduction of one group over the other is desired, groups like aldehydes and ketones that form acetals readily can be protected from undergoing undesirable reactions. For instance, if a compound contains a ketone and an ester group, the ketone can be protected by converting it into acetal. On the other hand, the ester does not form acetal; hence it can be subjected to the desired reaction, and in&#160;the end, the ketone can be deprotected.
<img alt="Figure1" src="/files/ftp_upload/12333/12333_Figure_1.svg" style="opacity: 0.9; text-align: center; height: 200px;" />
The sulfur-containing analogs of acetals are called thioacetals that&#160;can act as an efficient protecting group for aldehydes and ketones. The thioacetals are stable in acidic conditions. Due to this, they cannot be deprotected by acid hydrolysis. Instead, mercuric chloride in aqueous acetonitrile is used for its deprotection.
<img alt="Figure2" src="/files/ftp_upload/12333/12333_Figure_2.svg" style="text-align: center; height: 55px;" />
Apart from acting as protecting groups, thioacetals also play a major role in organic synthesis, especially in reduction reactions. Thioacetals can undergo desulfurization in the presence of Raney nickel and hydrogen to form hydrocarbons.
<img alt="Figure3" src="/files/ftp_upload/12333/12333_Figure_3.svg" style="text-align: center; height: 55px;" />

아세탈과 티오아세탈은 알데히드와 케톤을 위한 보호기로서

Acetals are formed by reacting two equivalents of alcohol with carbonyl compounds like aldehydes or ketones. Acetals are unaffected by bases, ...

Aldehydes and Ketones

Amides to Carboxylic Acids: Hydrolysis

Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more electrophilic. Next, water acts as a nucleophile and attacks the carbonyl carbon to form a tetrahedral intermediate. Further, deprotonation of the tetrahedral intermediate gives a neutral tetrahedral addition intermediate. Subsequent protonation of the amino nitrogen converts the amino group into a better leaving group. In the next step, the carbonyl group is re-formed with the departure of ammonia as a leaving group. A final deprotonation step yields a carboxylic acid.
<img alt="Figure1" src="/files/ftp_upload/12372/12372_PT_Figure_1_.svg" style="text-align: center; height: 225px;" />
The formation of ammonium ion drives the equilibrium favoring the product formation.
Base-promoted hydrolysis: 
Base-promoted hydrolysis is another nucleophilic acyl substitution reaction, where hydroxide acts as a nucleophile. Amides undergo hydrolysis when heated under basic aqueous solutions to produce carboxylic acid.
The base-promoted mechanism involves a nucleophilic attack by the hydroxide ion at the amide carbonyl carbon to form a tetrahedral intermediate. In the second step, the carbonyl group is reconstructed with the departure of an amide ion as a leaving group. Next, deprotonation yields a carboxylate ion and ammonia. This step drives the reaction to completion, which pushes the equilibrium towards the product. A final step involves acidification of the carboxylate ion to give free acid.
<img alt="Figure2" src="/files/ftp_upload/12372/12372_PT_Figure_2.svg" style="text-align: center; height: 200px;" />

아미드에서 카르복실산으로: 가수분해

Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires ...