Hydrolysis of Dipeptide Heptyl Esters with Newlase F

Peptides conjugates, such as lipo-, glyco-, phospho- and nucleopeptides1, are of great importance in the research of signal transmission2, protein phosphorylation/ dephosphorylation, antibody, and so on. However, the synthesis of these compounds is severely complicated by their pronounced acid and base lability as well as their multifunctionality. Under basic or acidic conditions, (-elimination reactions, anomerization, hydrolysis or rupture of these compounds may occur. The traditional peptid…     

Selective Alkaline Protease Catalyzed Hydrolysis of Peptide Esters

Procedures for preparing C-terminal free peptides from hydrolysis of its corresponding methyl or benzyl esters catalyzed by alkaline protease has been developed. N-protected peptides having side-chain ester protecting groups or successive hydrophobic amino acid residues in its sequence are hydrolyzed selectively at C-terminal only and leave other bonds (β and γ- ester or peptide bonds) intact. Compounds which cause a side reaction in base mediated saponification could be hydrolyzed safely by this procedure. Products of this hydrolysis are useful intermediates for fragments coupling in the solid phase peptide synthesis.     

Facile Hydrolysis of Esters with KOH-Methanol at Ambient Temperature

Summary. A simple, rapid, and efficient method is reported for the hydrolysis of a variety of mono- and diesters of aromatic, aliphatic, fatty, and heterocyclic acids with potassium hydroxide in methanol at ambient temperature (35°C).     

A Convenient Procedure for the Hydrolysis of Hindered Esters

Although several procedures for the hydrolysis of hindered esters have been developed, most of them suffer from one or more disadvantages, either in lack of convenience or in stringent conditions which affect other functional groups. Among the presently available methods for effecting this conversion are lithium in ammonia, a strong reducing agent¹; boron trichloride, a Lewis acid²; and a variety of reagents which bring about alkyl-oxygen cleavage. Among the latter are lithium iodide in a variety of solvents, usually at elevated temperatures, or in the presence of an organic base³; 1,5-diazabicyclo [4, 3, 0] nonene-5, in boiling xylene⁴, a reaction which failed in this laboratory⁵; various mercaptides^6,7, which in addition to being experimentally offensive, also cleave aryl alkyl ethers.     

Hydrolysis of Lipophilic Amino Acid Esters Catalyzed by Metallomicelles

Metallomicelles as the model of hydrolytic metalloenzymes have begun recently¹. Examples are the metal-ion complexes of lipophilic imidazoles² and pyridines³ co-micelled with surfactants. Herein we report the complexes of a novel macrocyclic 12-membered di-oxotetraamine ligand bearing bis-hydroxy groups as functional pendants which can mimic the catalytic function of carboxypeptidase A in micellar media.     

Carbon Origami via an Alumina-Assisted Cyclodehydrofluorination Strategy

The synthesis of pristine non-planar nanographenes (NGs) via a cyclodehydrofluorination strategy is reported and the creation of highly strained systems via alumina-assisted C−F bond activation is shown. Steric hindrance could execute an alternative coupling program leading to rare octagon formation offering access to elusive non-classical NGs. The combination of two alternative ways of folding could lead to the formation of various 3D NG objects, resembling the Japanese art of origami. The power of the presented “origami” approach is proved by the assembly of 12 challenging nanographenes that are π-isoelectronic to planar hexabenzocoronene but forced out of planarity.     

阳离子Gemini表面活性剂3,5-双(亚甲基十八烷基二甲基溴化铵)-1,2,4-三氮唑胶束对酯碱性水解的影响

在25℃条件下,研究了乙酸乙酯和乙酸戊酯在阳离子Gemini表面活性剂3,5—双(亚甲基十八烷基二甲基溴化铵)—1,2,4—三氮唑(简称18—triazole—18)胶束中的碱性水解反应。实验结果表明．在一定的表面活性剂浓度范围内,乙酸乙酯和乙酸戊酯在Gemini表面活性剂18—triazole—18胶束溶液中的碱性水解反应速率随表面活性剂浓度的增加呈上升趋势,达到一最大值后,随着浓度的增加呈下降趋势。实验结果还表明,18—triazole—18对乙酸乙酯碱性水解的影响较对乙酸戊酯碱性水解的影响大。随着底物疏水性的增加,乙酸乙酯和乙酸戊酯的碱性水解速率在18—triazole—18胶束中表观反应速率常数最大值分别为无表面活性剂时的5．5倍和1．1倍。     

羧酸酯水解与氨解反应的胶团催化研究

较系统地研究了在有氨和无氨缓冲体系中ｐＨ变化对羧酸酯脱酰反应速度和胶团催化作用的影响，提供在两种缓冲体系中反应速度随溶液ｐＨ变化的规律，结果表明ＣＴＡＢ胶团对对硝基苯酚丙酸酯和乙酸酯水解反应的催化效率随溶液ｐＨ上升而削弱，参硝基苯酚丙酸酯和乙酸酸在含氨的缓冲体系中有水解和氨解反应同时进行，ＣＴＡＢ胶团对水解反应正催化作用，而对氨解反应则显示负催化作用，这使得ＮＨ３－ＮＨ４Ｂｒ缓冲体系中ＣＴＡＢ胶团     

Enzymatic Reactions in Organic Synthesis 3-Separations of Esters by Enzymatic Hydrolysis

Enzymatic hydrolyses were used to separate mixtures of esters.     

表面活性剂复配混合胶束对酯碱性水解反应的影响

应用紫外分光光度法和热动力学法研究了芳香酸酯和正脂肪酸乙酯在表面活性剂复配事胶束（ＳＤＳ－Ｂ３５，ＤＴＡＢ－Ｂｒｉｊ－３５，ＴＴａｂ－Ｂｒｉｊ３５，ＣＴＡＢ－Ｂｒｉｊ３５，ＣＢＡＢ－Ｔｒｉｔｏｎ Ｘ－１００，ＳＤＳ－Ｔｒｉｔｏｎ Ｘ－１００）中的碱性水解反应，复配胶束对酯的碱性水解反应起禁阻作用，其禁阻作用比单一胶束的禁阻作用强，并讨论了复配胶束对酯碱解起禁阻作用的原因。     

Catalytic Hydrolysis of Lipophilic Amino Acid Esters by Metallomicelles as Carboxypeptidase A Models

Metallondcellesasthemodelofhydrolyticmetalloenzymes.havebegunrecently'.Exam-plesarethemetal-ioncomplexesoflipophilicinddazoles2andpyridines'co-ndcelledwithsurfactantS.Hereinwereportthecomplexesofanovelmacrocyclicl2-membereddioxotetradrineligandbearingbis-hydroxygroupsasfunctionalpendantSwhichcanmindcthecatalyticfunctionofcarboxypeptidaseAinndcellarmedia.2,6-Dioxo-l,4,7,lo-tetraazacyclo1(O.2Og,1.onuno1)'anddodecylglycidylether(O.54g,2.2nunol)'wererefluxedinEtOH(3OoInL)for24h.Thesolventwase…     

The Resolution of Amino Acids by Enzymes Part 1: Proteolytic Enzyme Bromelain for Hydrolysis of L-Amino Acid Methyl Esters

Preparation of optically pure L -amino acids from the corresponding methyl esters of racemic mixtures by treatment with proteolytic enzyme, bromelain, was investigated. The reaction was carried out at pH 6.0-6.5, 25°C in a mixture containing 0.1M substrate, 5mM β-mercaptoethanol, 0.05M potassium phosphate and 3mg/ml of crude enzyme. The product was isolated by ion exchange chromatography and the purity of product was established by m.p., tlc, ir spectrum, elemental analysis and optical rotation measurement.     

Effect of Chain Length on Enzymatic Hydrolysis of p-Nitrophenyl Esters in Supercritical Carbon Dioxide

The effect of chain length on the enzymatic hydrolysis of various p-nitrophenyl esters was investigated. Specifically, the hydrolysis of various esters p-nitrophenyl butyrate (PNPB), p-nitrophenyl caprylate (PNPC), p-nitrophenyl laurate (PNPL), p-nitrophenyl myristate (PNPM) and p-nitrophenyl palmitate (PNPP) was studied in supercritical carbon dioxide (ScCO₂) with lipase (Novozym 435). This indicates that the conversion of nitrophenyl esters decreases with increasing chain length. The effect of various parameters such as amount of water added, temperature, and enzyme loading was studied. The optimum temperature for the hydrolysis of PNPB and PNPC was 50°C but was 55°C for PNPL, PNPM, and PNPP in ScCO₂. The reactions were also conducted in acetonitrile as the solvent, and it was found that the reactions reach equilibrium much faster in ScCO₂ than in acetonitrile. The kinetics of the hydrolysis reactions were modeled using a Ping Pong Bi Bi model.     

Symmetrical and Asymmetrical Bisphosphonate Esters. Synthesis, Selective Hydrolysis, and Isomerization

Two simple and efficient one-pot procedures for the synthesis of a series of α-branched N-heterocycle-substituted methane-1,1-bisphosphonates are outlined. In the first method, the parent halosubstrates were reacted with cyanomethylphosphonate followed by reaction with dialkyl phosphonates to give asymmetrical or symmetrical bisphosphonates (BPs). In the second approach, the same halocompounds were reacted with tetraethyl methyl-1,1-bisphosphonate to give the requisite BPs. Partial and complete hydrolysis of the prepared BPs were also investigated. The products contain functional groups advantageous for further synthetic modification as structural units for coupling with the drug.     

Symmetrical and Asymmetrical Bisphosphonate Esters. Synthesis, Selective Hydrolysis, and Isomerization

Summary. Two simple and efficient one-pot procedures for the synthesis of a series of α-branched N-heterocycle-substituted methane-1,1-bisphosphonates are outlined. In the first method, the parent halosubstrates were reacted with cyanomethylphosphonate followed by reaction with dialkyl phosphonates to give asymmetrical or symmetrical bisphosphonates (BPs). In the second approach, the same halocompounds were reacted with tetraethyl methyl-1,1-bisphosphonate to give the requisite BPs. Partial and complete hydrolysis of the prepared BPs were also investigated. The products contain functional groups advantageous for further synthetic modification as structural units for coupling with the drug.     

Substituent and Isotope Effects on the Hydrolysis Rates of 2-Aryl-2-diazocarboxylic Esters

The overall kinetic solvent isotope effects on the acid catalyzed hydrolysis of a series of 2-aryl-2-diazocarboxylic esters ArCN₂COOCH₃, and one 2-aryl-2-diazocarboxamide C₆H₅CH₂CON (CH₃)₂ vary inversely with the reactivity of the substrate, between limits of 3.14 and 1.46. A linear Hammett plot for the hydrolysis rates of the a-diazocarboxylic esters indicates that there is no mechanistic change for the hydronium-ion-catalyzed reaction. The relation between hydrolysis rate and buffer acid concentration deviates from linearity for high values of the latter. It is shown on the basis of the solvent isotope effects for the non-linear region that this deviation does not stem from a mechanistic change caused by the buffer base component. The specific salt effects on the general acid-catalyzed reaction are discussed.     

Symmetrical and Unsymmetrical Bishophonate Esters Chemistry: Synthesis,Selective Hydrolysis,Isomerization

Abstract

Over thc past few years, bisphosphonatcs have bcen receiving increased auention as a new class of pharmacologically active compound. As a continuation of our research program (1,2,3) in connection with the synthesis of bisphosphonate esw I. we present here some results about thc synthesis of symmetrical and unsymmcuical bisphosphonate esms. These compounds were selectively hydrolizcd to give the following mono, di, d and tcua acids II.