Isobutyl hydrolysis

Trichodesmine, CigHa70gN, m.p. 160-1° (dec.), [ ]d+ 38° (EtOH), gives a methiodide, m.p. 202° (dec.), and on alkaline hydrolysis yields retronecine (p. 607) and dZ-lactic acid with isobutyl methyl ketone, the latter probably arising from a -ketonic acid first formed. ... 

An isobutyl carbonate was prepared by reaction with isobutyl chloroformate (Pyr, 20°, 3 days, 73% yield), to protect the 5 -OH group in thymidine. It was cleaved by acidic hydrolysis (80% AcOH, reflux, 15 min, 88% yield). ... 

To set the stage for the crucial aza-Robinson annulation, a reaction in which the nucleophilic character of the newly introduced thiolactam function is expected to play an important role, it is necessary to manipulate the methyl propionate side chain in 19. To this end, alkaline hydrolysis of the methyl ester in 19, followed by treatment of the resulting carboxylic acid with isobutyl chlorofor-mate, provides a mixed anhydride. The latter substance is a reactive acylating agent that combines smoothly with diazomethane to give diazo ketone 12 (77 % overall yield from 19). 

Similarly to quantitative determination of high surfactant concentrations, many alternative methods have been proposed for the quantitative determination of low surfactant concentrations. Tsuji et al. [270] developed a potentio-metric method for the microdetermination of anionic surfactants that was applied to the analysis of 5-100 ppm of sodium dodecyl sulfate and 1-10 ppm of sodium dodecyl ether (2.9 EO) sulfate. This method is based on the inhibitory effect of anionic surfactants on the enzyme system cholinesterase-butyryl-thiocholine iodide. A constant current is applied across two platinum plate electrodes immersed in a solution containing butyrylthiocholine and surfactant. Since cholinesterase produces enzymatic hydrolysis of the substrate, the decrease in the initial velocity of the hydrolysis caused by the surfactant corresponds to its concentration. Amounts up to 60 pg of alcohol sulfate can be spectrometrically determined with acridine orange by extraction of the ion pair with a mixture 3 1 (v/v) of benzene/methyl isobutyl ketone [271]. 

The hydrolysis of various para-substituted a-methylstyrene oxides was studied using 10 EHs [184]. The hydrolysis of the isobutyl compound with the enzyme from A. niger WHS the key step in the synthesis of (S)-ibuprofen (Figure 6.65). The (R)-diol was recycled via chemical racemization. 

In 1961, Roig and Dodson carried out a further study of the exchange in perchlorate media under identical conditions (25 °C, fi = 3.0 M) to those in the Tl(III) hydrolysis studyThe isotope was used, with a separation procedure based on extracting TI(III) from reaction mixtures with either methyl isobutyl ketone or diethyl ether. The exchange was examined in the absence of light, and a correction procedure to eliminate the catalytic effects of traces of chloride ions was used since Tl(III) concentrations of 10 M were necessary at the very low acidities employed. Using the known values of the first and second hydrolysis constants of Tl(III) (K2 and K3)... 

The physical properties of the acid- and ion-containing polymers are quite interesting. The storage moduli vs. temperature behavior (Figure 8) was determined by dynamic mechanical thermal analysis (DMTA) for the PS-PIBMA diblock precursor, the polystyrene diblock ionomer and the poly(styrene)-b-poly(isobutyl methacrylate-co-methacrylic acid) diblock. The last two samples were obtained by the KC>2 hydrolysis approach. It is important to note that these three curves are offset for clarity, i.e. the modulus of the precursor is not necessarily higher than the ionomer. In particular, one should note the same Tg of the polystyrene block before and after ionomer formation, and the extension of the rubbery plateau past 200°C. In contrast, flow occurred in... 

Formation of chloroquinazolines by amine diazotization can also been performed, but in the case of 4-amino-2-chloro-5-iodo-6,7-dimethoxyquinazoline 122, chlorination with isobutyl nitrite and cupric chloride to give 123 was accompanied by hydrolysis to the analogous quinazolinone 124 <2005TL983>. 

The prototype for this class of compounds is ibufenac (42-3), developed by a group at Boots in the UK. This drug was to be quickly superseded by its a-methylated congener, ibuprofen, from the same laboratory [43]. The mechanistically very complex Wilgerodt reaction constitutes the key to the preparation of ibufenac. Thus, reaction of the acetylation product (42-1) from isobutyl benzene and acetyl chloride with sulfur and morpholine leads to the transposition of the oxidized function to the terminal carbon and formation of thiomorpholide (42-2). Hydrolysis of the thioamide... 

Yet a further increase in potency is observed when the para-isobutyl group is replaced by a benzene ring. One published synthesis for that compound is quite analogous to the malonate route to the parent drug. The acetyl biphenyl (50-1) is thus converted to the corresponding arylacetic acid by reaction with sulfur and morpholine, followed by hydrolysis of the first-obtained thiomorpholide. This is then esterified and converted to malonate anion (50-2) with sodium ethoxide and ethyl formate. The anion is quenched with methyl iodide hydrolysis of the esters followed by decarboxylation yields the NSAID flubiprofen (50-3) [51]. 

It of interest to note that the isobutyl group may also be replaced by a heterocyclic ring. The route to this compound, pirprofen (51-6), starts with the direct methylation of unesterihed 4-nitrophenylacetic acid (51-1). The observed selectivity for monoalkylation in this case may reside in the structure of the dianion, whose most stable form is presumably that depicted in (51-2). Catalytic reduction of the product (51-3) gives the corresponding aniline this is then converted to its acetanilide (51-4) with acetic anhydride. Treatment with chlorine followed by hydrolysis gives the chloroaniline (51-5). Double alkylation of this last intermediate with 1,4-dichloro-but-2-ene (depicted as the cis isomer for aesthetic reasons) forms the dihydropyrrole ring. There is thus obtained the NSAID pirprofen (51-6) [52]. 

Figure 25-9 Bulky isobutyl groups protect siloxane bonds from hydrolysis at low pH. [From J. J. Kirkland, Am. Lab. June 1994, p. 28K.]...

A poly[ 3-Asp(a-OiBu)]n (50) was prepared by Yuki et al.[32] by the polycondensation of the [3-4-nitrophenyl ester of a-isobutyl-L-aspartate [HCl H-Asp((3-ONp)-u-OiBu] (49) (Scheme 15). Some of the data recorded for the optical rotations of these polymers (and the monomer after hydrolysis of samples of the polymer) suggests that some racemization may have taken place during polymerization although the authors believe this not to be the case. For example, the addition of HOBt to the polymerization reaction appeared to result in an increased yield of 80% but the [a]D value dropped from approximately -15 in most cases to —7 under these conditions. Co-polymerization of HBr H-Asp((3-ONp)-a-OiBu and (3-Ala ((3-HGIy) under the same conditions yielded a co-polymer with a composition of 53 mol% 13-Ala and 47 mol% Asp(a-OiBu). 

The use of NBD-Cl for the fluorescence analysis of alkylamine-generating pesticides has been investigated [173]. A two-phase reaction system is employed for the hydrolysis and labeling of N-methyl- and N,N-dimethyl-carbamate pesticides. The residue is hydrolyzed in 0.1 M sodium carbonate and the liberated amine is treated with NBD-Cl in an organic phase (IBMK, isobutyl methyl ketone) above the aqueous layer. An aliquot portion of the organic layer is used for chromatography. The reactions involved are shown in Fig. 4.65. 

Since alcohols and aldehydes are both formed in the Oxo reaction, acetals are formed (158). A recent paper by Macho (87) studied their further reactions under Oxo conditions, hydrolysis, hydrogenolysis, and thermal decomposition. Decomposition to saturated and unsaturated ethers increased with temperature from 12% at 120° to 41% at 170° C. Thus isobutyl ether, isobutenyl isobutyl ether, isobutanol, and isobutyraldehyde were identified by gas-phase chromatography among the reaction products of the decomposition of isobutyraldehyde diisobutyl acetal. 

P. L. Barili, G. Berti, G. Catelani, F. Colonna, and E. Mastrorilli, Alkaline and enzymatic hydrolysis of isobutyl 3,4-anhydro-2,6-dideoxy-DL-hexopyranosides. Preparation of enantiomeric boivinopyranosides through a highly efficient kinetic resolution, J. Org. Chem., 52 (1987) 2886-2892. 

Various organic solvents were tested for the PLE-catalyzed asymmetric hydrolysis of diester (12) in a biphasic system. The results (Table 5) indicate that the reaction yields and e.e. of monoester (13) were dependent on the solvent used in the asymmetric hydrolysis. Tetrahydrofuran (THF), methyl isobutyl ketone (MIBK), hexane, and dichloromethane inhibited PLE. Lower reaction yields (28-56 M%) and lower e.e. (59-72%) were obtained using f-butyl methyl ether, dimethylformamide (DMF), and dimethylsulfoxide (DMSO) as cosolvent. Higher e.e. (>91%) was obtained using methanol, ethanol, and toluene as cosolvent. Ethanol gave highest reaction yield (96.7%) and e.e. (96%) for monoester (13). 

The extremely large number of lanolin derivatives has been reviewed by Barnett8 and Steel.16 Lanolin derivatives can be formed by acetylation, ethoxylation, propoxylation, alkoxylation, and isobutylation of hydroxy groups, as well as hydroxylation of the double bond in the sterol ester component. Hydrolysis of lanolin can also produce lanolin alcohols and lanolin acids, which like lanolin can be ethoxylated, acetylated, and hydoxylated. 

Structures of the same type have also been prepared by cationic polymerization techniques, as can be seen in Scheme 16. Vinyl ethers having isobutyl-, ac-etoxy ethyl-, and malonate ethyl- pendant groups have been used. Hydrolysis of... 

Acetoxy-6-acetoxymethyl-3-isobutyl-5-methoxypyrazine (130) gave 6-hydrox-ymcthyl-3-isobutyl-5-methoxy-2(l//)-pyrazinone (131) (K2C03, MeOH—H20, 20°C, 30 min 97% note hydrolysis of both nuclear and extranuclear acetoxy groupings).329... 

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