Hexanoate esters

The nature of the group added to the cyclodextrin and the amount of substitution can affect the solubility of the cyclodextrin. If a nonpolar group is added, solubility of the modified cyclodextrin depends on the size of the group and the degree of substitution (DS). To make an acetate ester of (3-cyclodextrin that is insoluble in water, at least 17 of the 21 hydroxyl groups must be acetylated. If hexanoate ester is made, only three hydroxyl groups need to be esterified to create insolubility. These derivatives are more soluble in organic solvents than are the unmodified cydodextrins. 

Enzymatic hydrolysis rates for different positional and structural esters of lincomycin were determined in dog serum and simulated USP intestinal fluid (75). In general, the hydrolysis rates were faster in simulated intestinal fluid than in dog serum, indicating a higher esterase activity in simulated intestinal fluid. The 2- propionate ester of lincomycin was hydrolyzed slower than the longer chain 2 hexanoate ester, with the greatest difference in rates occuring in simulated intestinal fluid. Sterically hindered esters were hydrolyzed at extremely slow rates. 

Empirical rules have been elaborated to account for competition between these pathways, depending on electrolysis conditions [180], The Coventry group chose to examine a system almost at balance where both pathways operate [183] in order to best identify any sonoelectrochemical effect on mechanism [184], Table 4 shows product ratios (by glc) from the electrooxidation of partially neutralized cyclohex-anecarboxylate in methanol at platinum, at a current density of 200 mAmp cm-2. The first column shows a substantial amount (49%) of the dimer bicyclohexyl from the one-electron pathway, together with cyclohexylmethylether, cyclohexanol, and other products from the two-electron pathway (totaling -30%). The methyl cyclo-hexanoate ester (17%) is considered to arise from acid-catalyzed chemical esterification of the starting material with methanol solvent, due to the quantity of protons produced around the anode since at the high current densities needed, the parasitic... 

The microstructure of sucrose alkanoate single-phase microemulsion, with a short-chain hexanoate ester as the oil, has been studied in some detail by Bolzinger-Thevenin et al. using freeze fracture micrography and SANS [103]. The microstructure of the Winsor IV single-phase region was shown... 

Dave, V. Glasser, W. G. (1993). Cellulose-based fibers from liquid crystalline solutions. III. Processing and morphology of cellulose and cellulose hexanoate esters. 

Scheme 2 Route to ( )-endo-norbomeol via the hexanoate esters.

Hammet and collaborators140, 141 studied in more detail the hydrolysis of aliphatic esters with a cation-exchange resins as catalyst. They found that replacement of 70% of the hydrogen ions in a crosslinked polystyrenesulfonic add by cetyl-trimethylammonium ions had a specifically favorable effect on the effectiveness of the remaining hydrogen ions for the hydrolysis of ethyl-n-hexanoate. From these findings, the important contributions of the hydrophobic forces, in addition to the electrostatic forces, is clearly demonstrated. 

Acetic acid, butyryl-, ethyl ester [Hexanoic acid, 3-oxo-, ethyl ester] 55, 73, 75 Acetic acid, chloro-, tert-butyl ester [Acetic acid, chloro- 1,1-dimethylethyl ester], 55,94... 

Hexadiene, 55,109 Hexanoic acid, 55, 27 28 Hexanoic acid, 2-bromo-, 55,30 Hexanoic acid, 3-oxo ethyl ester [Acetic... 

C7H11NO 3731-38-2) see Clidinium bromide (37J)-6-oxo-3-[(tetrahydro-2H-pyran-2-yl)oxy]hexanoic acid ethyl ester... 

Methyl 6-bromohexanoate Hexanoic acid, 6-bromo-, methyl ester... 

Consider the case of the production of peroxy esters (e.g. tert-buty] peroxy 2-ethyl hexanoate), based on the reaction between the corresponding acid chloride and the hydroperoxide in the presence of NaOH or KOH. These are highly temperature sensitive and violently unstable, and solvent impurities are detrimental in their applications for polymerization. Batch operations to produce even 1000 tpa will be unsafe. A continuous reactor can overcome most of the problems and claims have been made for producing purer chemicals at lower capital and operation cost the use of solvent can be avoided. Continuous reactors can produce seven to ten times more material per unit volume than batch processes. Since the amount of hazardous product present in the unit at any given time is small, protective barrier walls may be unneccessary (Kohn, 1978). 

Armed with the above insight, we can examine the pharmacological ramifications of esterifying hydrocortisone. In Fig. 5 the ability of hydrocortisone esters to suppress inflammation induced by tetra-hydrofurfural alcohol, which acts simultaneously as irritant and vehicle, is shown as a function of the alkyl chain length of the esters [56]. An optimum chain in effect is seen at an alkyl chain length of six (hexanoate),... 

Wolberg, M., Hummel, W. and Muller, M. (2001) Biocatalytic reduction of beta,delta-diketo esters a highly stereoselective approach to all four stereoisomers of a chlorinated beta,delta-dihydroxy hexanoate. Chemistry -A European Journal, 7 (21), 4562-4571. 

Figure 11.2 Py/silylation GC/MS chromatograms of aged linseed oil pyrolysed in the pre sence of HMDS, (a) Pyrogram obtained with a microfurnace pyrolyser pyrolysis temperature 600 °C furnace pressure 14 psi purge flow 0.5 ml min (b) Pyrogram obtained with a resistively heated filament pyrolyser pyrolyser interface I80°C transfer line 300°C valve oven 290°C. 1, Hexenoic acid, trimethylsilyl ester 2, hexanoic acid, trimethylsilyl ester 3, heptenoic acid, trimethylsilyl ester 4, heptanoic acid, trimethylsilyl ester 5, octenoic acid, trimethylsilyl ester 6, octanoic acid, trimethylsilyl ester 7, nonenoic acid, trimethylsilyl ester 8, nonanoic acid, trimethylsilyl ester 9, decanoic acid, trimethylsilyl ester 10, lauric acid, trimethylsilyl ester 11, suberic acid, trimethylsilyl diester 12, azelaic acid, trimethylsilyl diester 13, myristic acid, trimethylsilyl ester 14, sebacic acid, trimethylsilyl diester 15, palmitic acid, trimethylsilyl ester 16, stearic acid, trimethylsilyl ester...

SIAX, succinimidyl-6-((iodoacetyl)amino)hexanoate, is a heterobifunctional reagent containing an NHS ester on one end and an iodoacetyl group on the other end (Brinkley, 1992)... 

SIACX, or succinimidyl-6-((((4-(iodoacetyl)amino)methyl)cyclohexane-l-carbonyl)amino) hexanoate, is an analog of SIAC that contains an additional aminohexanoate spacer group next to its NHS ester end (Invitrogen). The result is the creation of an approximately 16-atom spacer arm between conjugated molecules. All other properties of SIACX are similar to SIAC. 

SANPAH (N-succinimidyl-6-(4 -azido-2 -nitrophenylamino)hexanoate) is a heterobifunctional crosslinking agent containing an NHS ester and a photoreactive phenyl azide group (Thermo Fisher). The NHS ester end can react with amine groups in proteins and other molecules, forming... 

The ketene in (2.2) can be trapped by Water or alcohol to give carboxylic acids or esters. Such reactions have already been applied more than seventy years ago in the formation of substituted hexanoic acids (2.4)207). 

Active ester stock solution A dissolvelO mg of sulfosuccinimidyl-6-(biotini-mide)hexanoate (BIO-NHS, Pierce) in 1 ml of DMF. 

Representatives of the subfamilies Omaliinae and Proteininae (omaliine group) possess an abdominal defensive gland reservoir that opens out between sternite 7 and 8 [ 120]. The multi-component mixtures contained in these glands are used for defence. In Omaliinae and Proteininae the secretion is characterized by mixtures of acids (e.g. 2-methylpropanoic acid, hexanoic acid, 2-octenoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, butyric acid, and tiglic acid), aldehydes (( )-2-hexenal, heptanal, octanal, nonanal), ketoaldehydes such as 4-oxo-2-hexenal 41 (Scheme 5), 6-methyl-5-hepten-2-one, alcohols (octanol, ( )-2-hexen-l-ol, 2-methylbutan-l-ol), alkanes (nonadecane), esters (2-methylbutyl tiglate 42, various propanoates, 2-hexenyl 3-methylbutanoate, 2-methylbutyl 2-methylbutanoate, octanoates,butanoates), and aromatic compounds (e.g. 2-phenethyl 3-methylbutanoate 43). Unusual compounds are 2-... 

In addition to peptide-based studies, degradation and absorption kinetics of a homologous series of acyclovir ester prodrugs have been studied using the in situ perfusion model [25, 26], The studies showed that due to high esterase activity of the rat nasal mucosa (96% disappearance of hexanoate prodrug of acyclovir in 960 min), the rat in situ model is an acceptable model to screen the nasal absorption of prodrugs. 

Other 4-nitrophenyl esters have also been reported to be substrates of various hydrolases. For example, 4-nitrophenyl hexanoate (7.19) was hydrolyzed by bovine serum albumin [39], The affinity of the substrate for the macromolecule was found to be high (Km/n = 0.040 mM, where n is the number of sites), but the reaction itself was slow ( = 5 10-3 s-1, where k2 is the first-order rate constant of the formation of the phenol product from the enzyme-substrate complex). Another ester, 4-nitrophenyl pivalate (7.20), was hydrolyzed by cytoplasmic aldehyde dehydrogenase at a maximum velocity ca. 1/3 and an affinity ca. 1/20 those of the acetate [40], However, the rate-limiting steps were different for the two substrates, namely acylation of the enzyme for the pivalate, and acyl-enzyme hydrolysis for the acetate (see Chapt. 3). 

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