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Ethers tetraacetate

Fig. 1. Approximate pH values and ranges for a selection of biochemical and geochemical environments, with their relation to successive pK values for the aminocarboxylate ligand ethylene glycol bis-(2-aminoethyl ether)-tetraacetate, egta. Fig. 1. Approximate pH values and ranges for a selection of biochemical and geochemical environments, with their relation to successive pK values for the aminocarboxylate ligand ethylene glycol bis-(2-aminoethyl ether)-tetraacetate, egta.
EGTA ethylene glycol bis(-aminoethyl ether) tetraacetate... [Pg.630]

The benzyl group has been widely used for the protection of hydroxyl functions in carbohydrate and nucleotide chemistry (C.M. McCloskey, 1957 C.B. Reese, 1965 B.E. Griffin, 1966). A common benzylation procedure involves heating with neat benzyl chloride and strong bases. A milder procedure is the reaction in DMF solution at room temperatiue with the aid of silver oxide (E. Reinefeld, 1971). Benzyl ethers are not affected by hydroxides and are stable towards oxidants (e.g. periodate, lead tetraacetate), LiAIH, amd weak acids. They are, however, readily cleaved in neutral solution at room temperature by palladium-catalyzed bydrogenolysis (S. Tejima, 1963) or by sodium in liquid ammonia or alcohols (E.J. Rcist, 1964). [Pg.158]

EGTA ethyleneglycol-bis(P-ami noethyl ether) -N,N -tetraacetic acid 5.4 10.9... [Pg.364]

The most suitable oxidizing agent is potassium ferricyanide, but ferric chloride, hydrogen peroxide ia the presence of ferrous salts, ammonium persulfate, lead dioxide, lead tetraacetate or chromate, or silver and cupric salts may be useful. Water mixed, eg, with methanol, dimethylformamide, or glycol ethers, is employed as reaction medium. [Pg.430]

Phenylpftenanttirldlne (3).3 Amine hydrochloride 1 (2.72 g, 9 28 mmol) in EtOH (75 mL) was treated with 0 926 N cold solution of KCXI. Colorless crystals appear The mixture was shaken lor 30 mtn in ice, water was added and the product was filtered and dryed (PaOs) to afford 2.7 g of 2 (100%), rnp 102°C (hexane) 2 (2 0 g, 6 6 mmol) in anh pyndine (20 mL) was treated with an excess of NaOCHa (exothermc) Alter 20 h the solvent was removed In vacuum, the residua triturated with EtaO and the extract treated with dry HCI to obtain the hydrochlonda of 3, mp 107-108°C (from petroleum ether), mp 95-100° (Irom water) Olphenylmethyieneanlllna (5). To a suspension of lead tetraacetate (4.9 g, fO mmol) in PhH (100 mL) under Na was added a solution of tnphenyhnethylamine 4 (2 6 g, 10 mmol) in PhH (100 mL) dropwise under stirring The mixture was refluxed for 1 h, cooled, filtered, washed and the solvent evaporated The residue was crystallized from EtOH to give 2 2 g of 5 (85%), mp 111-112°C. [Pg.365]

A direct method for introduction of a C-21 acetoxyl group into a 20-keto-pregnane is by reaction with lead tetraacetate at room temperature. Although originally the reaction carried out in hot acetic acid gave low yields, a careful study by Henbest has defined conditions so that yields as high as 86 % can be obtained at room temperature. The preferred solvent is 5 % methanol in benzene, with boron trifluoride etherate as catalyst. With either methanol or benzene, the yield is less than 4%. [Pg.203]

Note 1. If unpurified, but vacuum dried lead tetraacetate is used in the above procedure erratic results are obtained. If, however, commercial lead tetraacetate containing about 10% acetic acid is employed and 0.5% (v/v) of acetic acid is added to the reaction solution consistently high yields of ether are obtained. An excess of lead tetraacetate (up to 5 eq) is required for complete conversion. In the presence of acetic acid the reaction time must be extended to about 40 hr. [Pg.245]

No systematic study of the minimal required amount of lead tetraacetate has been made. In cases where the product of the hypoiodite reaction is an iodo ether (20-hydroxy steroids) the reaction can be interrupted at the iodohydrin stage by reducing the amount of iodine to about 0.5 mole. For the oxidation of iodo ethers to lactones, chromium trioxide-sulfuric acid in acetone has been used. Silver chromate is often added to the reaction mixture but comparable yields are obtained without the addition of silver salt. [Pg.250]

Bocchi et al. [5] pointed out that while the tetraacetate of p-/ T/-butyl calix[4]arene fails to form complexes with guanidium ions or Cs, the octa-(3,6-dioxaheptyl)-ether of p-/cr/-butyl calix[8]arene forms strong complexes with these cations. The Parma group [6] later showed that the hexa-(3-oxabutyl)ether of p-tert-hu y calix[6]arene also forms complexes with these ions. [Pg.339]

Compounds which produce a complex with Li+ ions have been investigated. The compounds examined were N,N,N, N tetramethylethylenediamine (TMEDA), eth-ylenediamine, crown ethers, cryptand [211], diglyme, triglyme, tetraglyme, eth-ylenediamine tetraacetic acid (EDTA) and EDTA-Li+ (n=l, 2, 3) complexes [59]. The cycling efficiency was improved by adding TMEDA, but the other additives did not show distinct effects. [Pg.348]

Microtubules can be reconstituted in vitro at 37 °C from a solution that contains a physiological mixture of brain tubulin, MAPs, small amounts of guanosine 5 -triphosphate (GTP), magnesium ions, and the calcium-chelating agent EGTA [ethylene glycol-bis(2-aminoethyl ether) N, N -tetraacetic acid]. Tubulin assembly is inhibited by low temperature and by the presence of calcium ions. [Pg.5]


See other pages where Ethers tetraacetate is mentioned: [Pg.259]    [Pg.274]    [Pg.338]    [Pg.621]    [Pg.1680]    [Pg.385]    [Pg.652]    [Pg.654]    [Pg.84]    [Pg.259]    [Pg.274]    [Pg.338]    [Pg.621]    [Pg.1680]    [Pg.385]    [Pg.652]    [Pg.654]    [Pg.84]    [Pg.210]    [Pg.517]    [Pg.429]    [Pg.431]    [Pg.136]    [Pg.25]    [Pg.462]    [Pg.661]    [Pg.243]    [Pg.454]    [Pg.207]    [Pg.242]    [Pg.243]    [Pg.244]    [Pg.245]    [Pg.251]    [Pg.264]    [Pg.427]    [Pg.458]    [Pg.458]    [Pg.66]    [Pg.15]    [Pg.146]    [Pg.612]    [Pg.919]    [Pg.923]   
See also in sourсe #XX -- [ Pg.272 ]




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