A monoesters

This ortho ester does not form a monoester upon deprotection as do acyclic ortho esters, thus avoiding a hydrolysis step. ... 

Access to diphosphates (pyrophosphates) and triphosphates is provided through the reaction of phosphoric mono- or diimidazolides with a monoester phosphate. 

In a similar way, carbocycles having a quaternary center could be obtained from acyclic unsaturated 1,3-dicarbonyl compounds [206]. Other combinations are the domino hydroformylation/Wittig olefmation/hydrogenation described by Breit and coworkers [207]. The same group also developed the useful domino hydroformyla-tion/Knoevenagel/hydrogenation/decarboxylation process (Scheme 6/2.14) [208] a typical example is the reaction of 6/2-66 in the presence of a monoester of malonic acid to give 6/2-67 in 41 % yield in a syn anti-ratio of 96 4. Compounds 6/2-68 and 6/2-69 can be assumed as intermediates. 

Fig. 8.6. Two-step activation of pilocarpine prodrugs [123]. The prodrugs are diesters of pilocarpic acid (8.86). Enzymatic hydrolysis (Reaction a) cleaves the acyl carrier group. The product is a monoester of pilocarpic acid that undergoes cyclization to pilocarpine (8.87) upon intramolecular nucleophilic attack and loss of the alcohol carrier. 

Fig. 1. A conceivable pathway for converting a monoester of phosphoric acid into a...

The phosphorus is covalently bound to the protein and is removed only by very severe heat treatments, high pH or some phosphatases. The phosphate is esterified mainly to serine (possibly a little to threonine) as a monoester ... 

A phosphate diester of the form R0P020R is prochiral, since one of the non-alkylated oxygen (160) atoms must be replaced to produce chirality. A monoester... 

The whole question of the specificity was reopened with the discovery that E. coli phosphatase, contrary to an earlier statement (114), hydrolyzed a variety of polyphosphates including metaphosphate of average chain length 8 (97). It was subsequently reported that partially purified phosphatases from several mammalian tissues had appreciable PPi-ase activity at pH 8.5 (115). This was confirmed (116) and extended to include ATPase and fluorophosphatase activities (117). Proof that the same enzyme is responsible for the monoesterase and PPi-ase activities was afforded by heat inactivation studies, cross inhibition experiments, and inhibition of PPi-ase activity by L-phenylalanine, a specific inhibitor of intestinal phosphatase. It was also found that calf intestinal phosphatase couid be phosphorylated by 32P-PP and the number of sites so labeled agreed with the number of active sites determined with a monoester substrate using a stopped-flow technique (118). It would seem that the main reason for the confusion with regard to the PPi-ase activity results from the inclusion of Mg2+ in the assay. This stimulates the monoesterase activity but almost completely inhibits PPi-ase activity (117). 

As with Km, the effect of pH on Fmax cannot be described by a simple ionization curve. With calf intestinal phosphatase, the log ym8X curve for a monoester substrate is sigmoid (143, 162) or, in the case of synovial phosphatase, extremely shallow (76). Both curves approach a maximum value at alkaline pH. Barman and Gutfreund, however, found that milk phosphatase had an optimum at pH 10 with only 60% activity at pH 11 (83). This is by no means typical since placental phosphatase has been shown to be fully active with the same substrate, p-nitrophenyl phosphate at pH 11.5 (85). With PP as substrate there is evidence that an optimum in Vmax is reached at considerably lower pH values (8.5-9.2) (116, 117, 164). A pH-activity curve for calf intestinal phosphatase is given in Fig. 3. Features to note are the plateau in activity around pH 7, corresponding to a minimum in the phosphorylation rate constant, and a change in rate determining step at about pH 6 (165). 

In the system epoxide (epoxy resin) — anhydride, we can thus expect the presence of anhydride, epoxy- and proton donor groups. In their study of the reaction mechanism, Fisch and Hofmann 20 22-24) proposed a sequence of reactions leading to the crosslinking of epoxy resins or to the formation of linear polyesters. The first step is the reaction of the anhydride with hydroxyl groups giving a monoester (Eq.(l))... 

In the first step (Eq. (8)), a binary complex of the proton donor and epoxy oxygen is formed. On addition of the anhydride, a ternary transition complex is formed which decomposes to a diester bearing a secondary hydroxy group (Eq. (9)). If the proton donor is a carboxy group, a monoester is formed and the carboxy group is... 

During the dissolution, an intermediate compound between cellulose and TFA is formed, which is described in the literature as an addition compound (II) and as a monoester (12). These compounds should give different theoretical yields—170% for the addition compound and 159% for the monoester (based on cellulose charge)—and different fluorine contents—20.6% and 22.1%, respectively. To check this, a-cellulose and glucose were treated with concentrated TFA at 120°C. After removing the TFA by evaporation, the reaction products were dried carefully at 40°C in vacuo over KOH pellets for 44 hr. The products were weighed and their fluorine contents determined. Another part of the reaction product was treated with water, dried, weighed, and analyzed for fluorine. 

The data obtained for yield and fluorine content (Table III) are more in accordance with an addition compound than with a monoester. Therefore, formation of such a compound containing one molecule of TFA per sugar unit during the treatment of polysaccharides with TFA is very probable. On the other hand, this result means for the hydrolysis method that after evaporating the TFA, the hydrolysate should be treated with water to decompose the addition compound. 

A racemic alcohol is resolved in the form of a monoester derived from phthalic anhydride of succinic anhydride. Thus, the diastereomeric salt of the monoester with a resolving amine is purified by crystallization. Also, optically active monoesters are recovered from the salts, and hydrolysed to give optically active alcohols (Fig. 10).23... 

In certain situations, the diffusion process occurs concurrently with a particular reaction in the membrane. For instance, when a prodrug (i.e., estradiol acetate) diffuses through the skin, an enzyme in the viable epidermis converts the prodrug to estradiol and acetate. A diester prodrug (i.e., PNU-82, 899) diffuses across a Caco-2 cell monolayer, which extensively metabolizes the diester to a monoester. 

A monoester functionalised NHC was successfully employed by Fiirstner et al. [218] in a second generation Grubbs catalyst [116,219] for olefin metathesis reactions. As usual for such catalysts, the NHC sits trans to the phosphane in the base of a square pyramidal geometry around the ruthenium centre with the phenylylidene located in the apex [131]. 

A related reaction that yields the same types of products as does the Michaelis-Arbuzov reaction begins with either a phosphinous acid or a monoester of a phosphonous acid. (The corresponding reaction may also be performed with a diester of phosphorous acid.) By treatment with an appropriate base, the conjugate base of the phosphorus-containing acid is generated that serves as the nucleophihc reagent for direct formation of the phosphonate or phosphine oxide product (or phosphonate product from a phosphorous acid diester). This procedure is commonly referred to as the Michaehs Becker reaction. ... 

Has a monoester content of 50-60%, free glycerol 1%, and moisture 1%, maximum. It is used as a component in mold release agents, a vehicle for agricultural insecticides, an anti-icing fuel additive, and a rust preventive additive for compounded oils. It is used in the textile industry as a lubricant component in synthetic fiber spin finishes. 

Values of the rate coefficients and k have been determined for ethane-l,2-diol andmethyl-substituted ethane-l,2-diols (Buisteta/. ). The general effect of methyl substitution is to decrease k . For meso- and ( )-butane-2,3-diols the values of kf are practically identical, although the equilibrium constant for forming the diester is much larger for the latter. This result suggests that formation of a monoester as an intermediate is rate determining, viz. 

If, on the other hand, aqueous acetic acid is added to the reaction mixture containing the positively charged intermediate, the product is a monoester of the diol, which, on hydrolysis, gives a diol. Such a reaction mimics a syn addition (Woodward reaction) [781, 783]. 

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