Hydrolysis HAMS

Thompson and coworkers investigated the acid hydrolysis of aryl glycosides of /3-n-glucopyranose and d-n-glucopyranuronic acid. They found that the rates of hydrolysis of substituted-phenyl d-u-glucopyranosid-uronic acids show little sensitivity to effects of a polar aglycon group (Ham-... 

Ribozymes are RNA molecules that catalyze biochemical reactions (54). Ribozymes cleave single-stranded regions in RNA through transesterification or hydrolysis reactions that result in cleavage of phosphodiester bends (55). To date, several RNA catalytic mo-tife, group I introns, RNase P, and both ham-... 

Hydrolysis of Hydroxylamine Disulfonate (HAPS). HADS hydrolyzes to give hydroxylamine monosulfonate (HAMS) and sulfates ... 

Hydrolysis of Hydroxylamlne Monosulfonate (HAMS). HAMS hydrolyzes in acidic solution, but at a much slower rate than that of HADS (13). The hydrolysis of HAMS produced hydroxylamine (HA) and sulfates ... 

Figures 1-4, 5, and 6 show the time-resolved concentration of species in a batch reactor at various pH s, temperatures, and initial partial pressures of SO2 and N0X for the first 2 and 24 hours respectively. The gas-to-liquid ratio (G/L) is 75. Figure 1 (at Ps02 = 1000, Pjjo = 450, and PNO2 = 50 ppm, pH = 5, and T = 328K) demonstrated that the removal efficiency of NO is only about 10%, although NO2 can be removed nearly completely. This is because NO alone cannot be converted into nitrous acid. The major product is HADS within the initial 1-1/2 hr the concentrations of HAMS and sulfate increase while that of HADS decreases as the reaction time continues. If the reaction is allowed to continue, the final products will be NH4+, N2, and sulfate. Because we disregard the reaction of HAMS and HA with HNO2 and the hydrolysis of nitrosulfonic acid, no N2O is formed.

The effect of the pH of the solution on the reaction is shown in Figure 3 (Ps02 = 1000, PN0 = PnC>2 = 250 PPm> pH = 3, and T = 328K). The reactions speed up at a lower pH (between pH = 5 and 3), and N0X is reduced at a larger rate. The concentration of HAMS is larger than HADS after about 20 min. Similarly, larger concentrations of HA, SAM, N2, and NH4+ are observed at a given time. These are due to the fact that the hydrolysis reaction is acid catalyzed, and therefore low pH conditions would favor the formation of hydrolysis products. 

A new alkaloid, crotalarine (17) has been isolated from Crotalaria burhia Buch.-Ham. The structure (17) proposed for crotalarine is based on alkaline hydrolysis to retronecine, 3-methyl-2-pentanone, lactic acid, and a lactone, crotalaric acid (18) the i.r. spectrum of which was similar to those of monocrotalic (19) and trichodesmic... 

Initial studies carried out in our laboratories served to confirm that the Eu(III) texaphyrin 8b is in fact capable of catalyzing the hydrolysis of phosphate diesters. For instance, using the ammonium salt of uridylyl-3, 5 -uridine (UpU) as a substrate, it was found that this particular texaphyrin is able to effect catalytic hydrolysis (as judged by a controlled HPLC product analysis) with a pseudo-zero order rate of (9.1 1.6) x lO mMh By comparison, under identical conditions, Eu(N03)3, was found to effect UpU hydrolysis with a pseudo-zero order rate of (2.7 0.2) X lO mMhwhile Morrow s Eu(III) hexaamine Schiff base complex ("EuHAM"),27e one of the better alternative systems known, induced hydrolysis with a corresponding rate of (4.1 0.4) x lO mMh- Additionally, these same studies served to confirm that the Eu(III) texaphyrin complex 8b is far more stable in solution than the corresponding HAM-derived product. Thus, from both a kinetic efficacy and intrinsic stability perspective, the Eu(III) texaphyrins appear to be the best metal-based systems for use in antisense applications. 

In this HAM protocol, ammonia was generated by the hydrolysis of urea in an acidic medium. Final cleavage of the oxazolidinone units produces the desired polyamino alcohols, which can be utilized as ligands in metal-catalyzed asymmetric transfer hydrogenations. 

The rate of hydrolysis of / -substituted styrene oxides in acidic medium is strongly affected by the nature of die substituent in the para position, varying from = 1-10x10 M" s for die MeO substituent to = 3.41x10" M" s in the case of the NO2 group. A plot of log An versus a " for all />ara-substituents gives an excellent Hammed correlation widi a slope p " = -A.l. 

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