Ester method

Method (1) is most frequently used for aliphatic acid amides, while Methods (2a), (2b) and (zc) are used most frequently for aromatic acid amides. Of the last three methods, the Acid Chloride Method (zb) is the most rapid and certain. The Ester Method (za) is practicable only when the amide is insoluble in water, and even then is often very slow unless the ester itself is appreciabb soluble in the aqueous ammonia solution. 

Perfluoroalkanesulfonic Esters Methods Stang P J Harmack M, Synthesis 85-126 263... 

Filter-pump, 44 Filtration through cloth, 131 under reduced pressure, 43 with fluted filter, 53 "Fischer s ester method, 133 Fluorescein, 187 Fluted filter, 53 Formic acid, 106 Fractional distillation, 136 Fractionating columns, 137 Freezing-point method, 32 I -riedel-Crafis reaction, 210 furnace, combustion, 4 tube, 23 ... 

Biphenyl-2,2 -diamine and ring-substituted biphenyl-2,2 -diamines are transformed into dibenzo[rf,/][l JJdiazepines 1 in various ways by reaction with ortho esters (Method A),169 with hydrochlorides of imido acid esters (Method B)170 or with the benzenesulfonates of pro-tonated nitriles (Method C).171 Selected examples are given. 

A general step ahead in polycondensation was achieved by the application of the active ester method by DeTar et al.19) and Kovacs et al.291 Very soon, the nitrophenyl ester, the pentachlorophenyl ester, or the hydroxysucdnimido ester were used exclusively. The esters of the protected tripeptides could be purified by crystallization, then the N-protecting group was split off and the free peptide esters were purified again. Addition of base starts the polycondensation, resulting quickly in the formation of a viscous solution at low temperature. 

FIG. 1 Critical micelle concentration as a function of the number of carbon atoms in the hydrophobic rest of sodium a-sulfo fatty acid methyl esters. Methods O, surface tension +, conductivity A, solubilization of a dye x, solubility (all without electrolyte) , surface tension with a constant electrolyte concentration of 5 x 10"2 mol/L. (From Ref. 57.)... 

STAHL w, HEINRICH u, JUNGMANN H, TRONNIER H and SIES H (2000) Carotenoids in hiunan skin non-invasive measurement and identification of dermal carotenoids and carotenoid esters. Methods Enzymol 319 494-502. 

Figure 16 Conjugation of an amine and a carboxylic acid via the (V-hydroxysuccinimide (NHS)-activated ester method. NHS esters may be isolated and characterized and are stable to long term storage as the powder. Alternatively, the NHS esters may be used immediately upon formation without isolation. Details of the reaction are given in Table 4...

The result of this method is consistent with that obtained by using the corresponding Mosher s ester method (Adn = d(/o-ATMA - (s)-atma) (Fig- 1-25). Note that in the method of Mosher s ester, (Ss — Sr) was applied to calculate Ah) i, the difference in the 2ATMA method is only due to the configuration nomenclature difference caused by the CIP rule. 

Polyamides containing thymine photodimer units in the main chain (17a,b) were prepared by polycondensation of thymine photodimer derivatives (15a,b), which were obtained by the photochemical reaction of the monomeric compound, and various diamines by the activated ester method (Figures 4 and 5) (17, 19). 

Carboxyethyl derivatives of the nucleic acid bases were grafted onto poly-L-lysine by using the activated ester method ( ). 

Esters of allylic alcohols can be rearranged to y,<5-unsaturated carboxylic acids via the O-trimcthylsilyl ether of the ester enolate.161 This rearrangement takes place under much milder conditions than the ortho ester method. The reaction occurs at or slightly above room temperature. Entries 14 and 15 of Scheme 6.12 are examples. The example in entry 16 is a rearrangement of the enolate without intervention of the silyl enol ether. 

Only in a few cases has this compound been isolated from the products of hydrolysis of proteins, since its separation is extremely laborious. It can only be effected after all the other amino acids have been removed by crystallisation and by the ester method, and after the diamino acids have been precipitated by phosphotungstic acid. From the last mother-liquors it is obtained by crystallisation, and is best identified in the form of its /8-naphthalene sulpho-derivative. 

The separation and estimation of the two main groups of amino acids can be carried out in one experiment, instead of separately as described. The protein is hydrolysed by sulphuric acid, the tyrosine, cystine and diaminotrioxydodecanic acid are removed by crystallisation, and the diamino acids are precipitated by phosphotungstic acid. From this precipitate they are obtained by decomposition with baryta, and they are then separated by means of their silver compounds by Kossel, Kustcher and Patten s method. The filtrate from the phosphotungstic acid precipitate is freed from the excess of phosphotungstic acid by means of baryta, and the solution is treated by Fischer s ester method for the monoamino acids. 

Sorensen and Andersen in 1908 synthesised proline by the sodium phthalimidomalonic ester method, a yield of about 80 per cent, being obtained. Sodium phthalimidomalonic ester is condensed with trimethylene bromide,... 

Cyanogen bromide method A,A -Carbonyl diimidazole method Divinylsulfone method Epoxy (bisoxirane) method Ethyldimethylaminopropyl carbodiimide method Eluoromethylpyridinium toluenesulfonate method A-hydroxysuccinimide ester method Schiff base (reductive amination) method Tresyl chloride/tosyl chloride method Sulfhydryls Azalactone method (for azalactone supports)... 

Hudson, B. E., and Ch. R. Hauser Condensations. XVI. Various Acylations and Alkylations of the Sodium Enolates of Aliphatic Esters. Methods for the Synthesis of a,a-Disubstituted j -Keto Esters and of Certain Other Compounds. J. Amer. chem. Soc. 63, 3156 (1941). 

Several synthetic methods are available for the preparation of Fc peptide conjugates, of which the active ester method is most compatible with biological environments.41 This method works under mild conditions with an isolable FcCO-active ester, in which reactive heterocyclic isolable esters are formed. These can be isolated or reacted in situ with suitable peptides to give the desired Fc-peptide conjugate. These active esters can be used as stoichiometric Fc delivery reagents, which make them suitable for automated solid-phase synthesis of Fc-peptide conjugates. 

Phthalate Esters (Method 606). These compounds are extracted with methylene chloride, concentrated, and solvent exchanged to hexane for Florisil or aluminum oxide column cleanup and EC-GC determination by using a mixed phase columnn of 1.5 SP-2250 and 1.95 SP-2401. This method is essentially the same as that for or-ganochlorine pesticides. 

P. J. Stang, M. Hanack, and L. R. Subramanian, Perfluoroalkanesulfonic esters methods of preparation and applications in organic chemistry, Synthesis 83 (1982). 

The Z-protected derivative, again prepared by standard methods using benzyl chloroformate,t208 may serve in the case of racemic pipecolic acid for resolution into the pure enantiomers by fractional crystallization with L-tyrosine hydrazide/208 Acylation with N-protected pipecolic acid or of pipecolyl peptides is performed by standard procedures via the active ester methods, e.g. A-hydroxysuccinimide ester/121 by the mixed anhydride method, e.g. with isobutyl chloro-formate 95-114 or pivalic acid chloride/121 as well as by DCC/HOBt/118 In the synthesis on solid support, longer coupling times are required when compared to N-protected proline.1[235 ... 

Cycloamidation has been used extensively to prepare 17-membered cycloisodityrosines. The acyclic biaryl ether precursors were prepared by methods including the Ullmann reaction 2-5 and nucleophilic aromatic substitution (SNAr)J6 7 Since these methods have all been used intramolecularly in cyclization reactions, they will be discussed in Sections 9.5.3 and 9.5.4. Evans and co-workers employed the pentafluorophenyl ester method of macrolactamization 8] to prepare 11, an intermediate in their total synthesis of OF4949-III (7) (Scheme 2)J3 In this case, the acidic removal of a Boc group was employed to release the cyclization substrate, although hydrogenolysis of a Z group is also effective 3 ... 

Solid-phase techniques can be applied to the N-activated esters.16 In the activated ester method, 4-nitrophenyl, 12 21-27 2,4-dinitrophenyl, 614 28 2,4,5-trichlorophenyl, 29 and penta-fluorophenyl 8 esters can be used, the amide bonds being formed with aminolytic release of the corresponding phenol (Scheme 4). For example, the use of pentafluorophenyl esters in the synthesis of pure azapeptides (named azatides for the first time) proved to be advantageous. 8 ... 

This coupling method seems to be equally suited to the synthesis of normal azaamino acid compared to the activated ester method. 

Perfluoroalkanesulfonic Esters Methods of Preparation and Applications in Organic Chemistry ... 

Perfluoroalkanesulfomc Esters Methods of Preparation and Applications in Organic Stang P J Hannack M, Subramanian L R Synthesis 85- 126... 

Figure 25-10 Stepwise synthesis of oxytocin by the reactive ester method, In the abbreviations used here—Gly—NH2 = —NHCH2CONH2...

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