Dihydrazides

Heating diethyl 2-phenyl-4,5-thiazoledicarboxylate (16) in alcohol with an excess of hydrazine hydrate gave a mixture of cyclohydrazide (17) and the open-chain 2-phenyl-4,5-thiazoledicarboxylic dihydrazide (18) (Scheme 11) (5). The relative amounts of these two products depended on... 

Thiazolecarboxylic acid hydrazides are prepared by the same general methods used to prepare amides, that is, by treating acids, esters, amides, anhydrides, or acid halides with hydrazine or substitued hydrazines. For example, see Scheme 21 (92). The dihydrazides are obtained in the same way (88). With diethyl 2-chloro-4,5-thiazoledicarboxylate this reaction gives the mono hydr azide monoester of 2-hydrazine-4,5-... 

Stmctural and chemical modification of urethane containing polymer matri-ces with macrocycles - calixarenes having reactive hydrazide groups have been carried out and stmcture, physico chemical and sensor properties of polyure-thanesemicarbazides (PUS) synthesised have been studied. The polymers obtained (on the base of polypropylene glycol MM 1000 and polysiloxane diol MM 860, hexamethylene diisocyanate and calixarene dihydrazide) are identified by IR-spectroscopy, size exclusion chromatography (SEC), DSC, WAXS and SAXS methods. 

Although this material contains a small amount of the symmetrical dihydrazide, which is not easily eliminated on crystallization, it is entirely satisfactory for use as a reagent for the isolation of ketones. A purer product, m. p. 192°, with decomposition, can be obtained by adding the solution prepared from ethyl chloroacetate and trimethylamine to an alcoholic solution containing a considerable excess of the hydrazine hydrate. 

Carbonic acid dihydrazide, carbazide, or N,N-diaminourea C 0(NHNH2)2] has a MW of 90.1. It is available as a 98+% liquid or in various diluted forms, typically a 6.5% formulated product. 

Raju J, Gupta VK. 1989. A new extractive spectrophotometric method using malonyl dihydrazide for the determination of organophosphoms pesticides in surface residues. Microchem J 39 166-171. 

Section A of Scheme 10.15 contains a number of examples of Curtius rearrangements. Entry 1 is an example carried out in a nonnucleophilic solvent, permitting isolation of the isocyanate. Entries 2 and 3 involve isolation of the amine after hydrolysis of the isocyanate. In Entry 2, the dihydrazide intermediate is isolated as a solid and diazotized in aqueous solution, from which the amine is isolated as the dihydrochloride. Entry 3 is an example of the mixed anhydride procedure (see p. 948). The first stage of the reaction is carried out in acetone and the thermolysis of the acyl azide is done in refluxing toluene. The crude isocyanate is then hydrolyzed in acidic water. Entry 4 is a reaction that demonstrates the retention of configuration during rearrangement. 

Treatment of malonic acid dihydrazide 226 with acetyl acetone or diketone 228 in ethanol at room temperature provides good yields of 227 and 229, respectively (Scheme 27) <2005JHC287>. 

The following protocols make use of the compounds adipic acid dihydrazide and carbohy-drazide to derivatize molecules containing aldehydes, carboxylates, and alkylphosphates. The protocols are applicable for the modification of proteins, including enzymes, soluble polymers such as dextrans and poly-amino acids, and insoluble polymers used as micro-carriers or chromatographic supports. 

Aldehyde-containing macromolecules will react spontaneously with hydrazide compounds to form hydrazone linkages. The hydrazone bond is a form of Schiff base that is more stable than the Schiff base formed from the interaction of an aldehyde and an amine. The hydrazone, however, may be reduced and further stabilized by the same reductants utilized for reductive amination purposes (Chapter 3, Section 4.8). The addition of sodium cyanoborohydride to a hydrazide-aldehyde reaction drives the equilibrium toward formation of a stable covalent complex. Mallia (1992) found that adipic acid dihydrazide derivatization of periodate-oxidized dextran (containing multiple formyl functionalities) proceeds with much greater yield when sodium cyanoborohydride is present. 

Add a quantity of adipic acid dihydrazide or carbohydrazide (Aldrich) to the protein solution to obtain at least a 10-fold molar excess over the amount of aldehyde functionality present. High molar ratios are necessary to avoid protein conjugation during the reaction process. If the concentration of aldehydes is unknown, the addition of 32mg adipic acid dihydrazide per ml of the protein solution to be modified should work well. 

Figure 1.108 Glycoproteins that have been treated with sodium periodate to produce aldehyde groups can be further modified with adipic acid dihydrazide to result in a hydrazide derivative.

Figure 1.109 Carboxylate groups on proteins may be modified with adipic acid dihydrazide in the presence of a carbodiimide to produce hydrazide derivatives.

Carboxylic acids may be covalently modified with adipic acid dihydrazide or carbohydrazide to yield stable imide bonds with extending terminal hydrazide groups. Hydrazide functionalities don t spontaneously react with carboxylate groups the way they do with aldehyde groups (Section 4.5, this chapter). In this case, the carboxylic acid first must be activated with another compound that makes it reactive toward nucleophiles. In organic solutions, this may be accomplished by using a water-insoluble carbodiimide (Chapter 3, Section 1.4) or by creating an intermediate active ester, such as an NHS ester (Chapter 2, Section 1.4). 

Most proteins contain an abundance of carboxylic acid groups from C-terminal functionalities and aspartic and glutamic acid side chains. These groups are readily modified with bis-hydrazide compounds to yield useful hydrazide-activated derivatives. Both carbohydrazide and adipic acid dihydrazide have been employed in forming these modifications using the carbodi-imide reaction (Wilchek and Bayer, 1987). 

Dissolve 32mg of adipic acid dihydrazide per ml of 0.1 M sodium phosphate, 0.15 M NaCl, pH 7.2. 

Alkylphosphate Group Adipic Acid Dihydrazide Phosphoramidate Linkage with... 

Add to the tube 7.5 pi of RNA or DNA containing a 5 -phosphate group. The concentration of the oligonucleotide should be 7.5-15 nmol or total of about 57-115.5 pg. Also, immediately add 5 pi of 0.25 M adipic acid dihydrazide or carbohydrazide dissolved in 0.1 M imidazole, pH 6.0. Because EDC is labile in aqueous solutions, the addition of the oligo and fezs-hydrazide/imidazole solutions should occur quickly. 

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