Tert-butyl methyl ester

Likewise, synthetic 2//-azepines isomerize to 3//-azepines in refluxing chloroform (2-3 h) or in tert-butyl methyl ether at room temperature.291 The isomers can be readily separated by chromatography on silica gel, as the more basic 2//-azepines30 have lower Rf values. In contrast, 7-butyl-2//-azepin-2-acetic acid (11), obtained by heating the tert-butyl ester 10 with iodotrimethylsilane, is stabilized by intramolecular hydrogen bonding and shows no tendency to rearrange to the 3//-isomer.291... 

Moreover, when the C-protonated ester mJz 117 is generated independently by El cleavage of tert-butyl methyl carbonate in the presence of CD3OD, mJz 73 and 76 are formed, as expected, from independent decarboxylation and condensation reactions (Scheme V). 

Vitamin D2 3,5-dinitrobenzoate Ergocalciferol, 3,5-dinitrobenzoate (8,9) (4712-11-2) Ethyl p-dimethylaminobenzoate Benzoic acid, p-(dimethylamino)-, ethyl ester (8) Benzoic acid, 4-(dimethylamino)-, ethyl ester (9) (10287-53-3) tert-Butyl methyl ether Ether, tert-butyl methyl (8) Propane, 2-methoxy-2-methyl-(9) (1634-04-4)... 

The properties of solvents has been studied extensively by Snyder (5), who created a dassification of the solvent properties of common solvents. It has been found (7) that (excluding proton donors such as alcohols) the maximum difference in mobile-phase selectivity is obtained if the polar solvents have a large difference in basidty. Thus, for maximum selectivity differences, one solvent should have a low basidty. Solvents of this type are acetonitrile, ethyl acetate or other esters, and acetone or other ketones. The other solvent should have a high basidty examples are ethers such as tert-butyl methyl ether, diethyl ether or tetrahydrofuran, or amines such as triethylamine. Between these groups and alcohols, large differences in chromatographic selectivity can be obtained in normal-phase chromatography (10). 

Due to the instability of the feri-butyl ester, and the resistance of the ethyl ester to transesterification, installation of the methyl ester prior to glycosylation was clearly required. Conversion of tert-butyl enol ester 51b to the methyl ester 51a was achieved in 78% yield over two steps, with hydrolysis of the tert-bvAy ester using trifluoroacetic acid at 0 °C, followed by methylation with trimethylsilyl diazomethane (Scheme 21). Gratrfyingly, when methyl enol ester 51a was... 

The application of lipases in the resolution of racemic p-amino acids and their derivatives has been comprehensively reviewed by Liljeblad and Kanerva [27]. The N-acylation method has been commonly employed in the resolution of p as well as P -amino esters [28-34] (Scheme 14.2). Suitable organic solvents for this reaction have proven to be, among others, diisopropylether, tert-butyl methyl ether, and diethyl ether, whereas the commonly employed acyl donors are butyl butanoate and 2,2,2-trifluoroethyl butanoate. 

Hydrocarbon + aliphatic ether (e.g., tert-butyl-methyl-ether) Hydrocarbon + cyclic ether (e.g., dioxane, tetrahydrofuran) Hydrocarbon + ester (e.g., ethyl acetate)... 

Free fatty acids can be efficiently extracted with acidified mixture of hexane/ tert-butyl methyl ether. Acids, esters, and salts are saponified with sodium hydroxide and esterified (transesterified) with methanol. Methyl esters are conveniently separated and determined by gas chromatography with a flame-ionization detector. Combination of gas chromatography and mass spectrometry, GC-MS, is one of the methods of choice for analysis of methylated fatty acids. Equivalent chain length of fatty acid can be calculated from the retention time. 

Then, 1-(3-acetylthio-2-methylpropanoyl)-L-proline is produced. The 1-(3-acetylthio-3-methyl-propanoyl)-L-proline tert-butyl ester (7.8 g) is dissolved in a mixture of anisole (55 ml) and trifluoroacetic acid (110 ml). After one hour storage at room temperature the solvent Is removed in vacuo and the residue is precipitated several times from ether-hexane. The residue (6.8 g) is dissolved in acetonitrile (40 ml) and dicyclohexylamine (4.5 ml) is added. The crystalline salt is boiled with fresh acetonitrile (100 ml), chilled to room temperature and filtered, yield 3 g, MP 187°C to 188°C. This material is recrystallized from isopropanol [ttlo -67° (C 1.4, EtOH). The crystalline dicyclohexylamine salt is suspended in a mixture of 5% aqueous potassium bisulfate and ethyl acetate. The organic phase is washed with water and concentrated to dryness. The residue is crystallized from ethyl acetate-hexane to yield the 1-(3-acetylthio-2-D-methylpropanoyl-L-proline, MP83°Cto 85°C. 

The anions derived from racemic alkyl and benzyl tert-butyl sulfoxides undergo 1,4-addition to a,/J-unsaturated esters to give adducts with high product diastereoselection (>5 1)10,11. Alkyl 4-methylphenyl sulfoxides were found to be less diastereoselective. In the case of 2-methyl-2-(methylsulfinyl)propanc the highly hindered 2,6-di-rer7-butyl-4-methylphenyl ester was required to prevent a competing acylation reaction. 

Benzoic acid, tert-butyl ester [Benzoic acid, 1,1-dimethylethyl ester], as impunty in ferf-butyUithium, 55, 125 Benzoic acid, 4-methoxy-, methyl ester, 55, 40... 

The diazo transfer reaction between p-toluenesulfonyl azide and active methylene compounds is a useful synthetic method for the preparation of a-diazo carbonyl compounds. However, the reaction of di-tert-butyl malonate and p-toluenesulfonyl azide to form di-tert-butyl diazomalonate proceeded to the extent of only 47% after 4 weeks with the usual procedure." The present procedure, which utilizes a two-phase medium and methyltri-n-octylammonium chloride (Aliquat 336) as phase-transfer catalyst, effects this same diazo transfer in 2 hours and has the additional advantage of avoiding the use of anhydrous solvents. This procedure has been employed for the preparation of diazoacetoacetates, diazoacetates, and diazomalonates (Table I). Ethyl and ten-butyl acetoacetate are converted to the corresponding a-diazoacetoacetates with saturated sodium carbonate as the aqueous phase. When aqueous sodium hydroxide is used with the acetoace-tates, the initially formed a-diazoacetoacetates undergo deacylation to the diazoacetates. Methyl esters are not suitable substrates, since they are too easily saponified under these conditions. 

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