Ester compounds

Okahara and his coworkers have made a number of contributions to the synthesis of crown ethers using a one-pot method (see Sect. 3.13). These methods have been applied largely to the preparation of simple aliphatic crown ether systems. In addition, this group has prepared macrocyclic ester compounds using a one-pot procedure. Although... 

It should be stressed that there has been considerable interest in macrocycles containing the pyridine subcyclic unit, especially by Newkome and coworkers (see also Chap. 4). Most of his interest appears to have been focussed on polyethers rather than ester compounds. Bradshaw has also reported syntheses of compounds containing the pyridine subcyclic unit. ... 

A mixture of 49 g of this ester compound, 76 g of 9B% formic acid and 6B ml of formalin solution is heated under reflux for B hours. The solvents are then removed in vacuo on the steam bath, the residue dissolved in water, made alkaline with ammonium hydroxide and extracted with chloroform. Removal of the solvent and distillation in vacuo yieids ethyl 4-di-methylaminocyclohexylcarboxylate, boiling point 122°C to 125°C/10 mm. 

TABLE 5 Comparing the Shaping of a Poly(ortho ester) Compound by Flux-Mixing with 5 wt% Stearic Acid... 

The AH unit was assigned to the carboxyl group, as the sweet taste of compounds 2 and 3 in Table XXIVa is lost when the carboxyl group is absent or when it is converted into the methyl ester (compound 4 in Table XXIVa). It was suggested " that this group mainly interacts with its counterpart on the receptor by ionic interaction. The absence of sweet taste... 

D. O., Warrington, B. H., Wong, S. Y. F., The preparation of a series cf nitrostilbene ester compounds using micro-reactor technology. Analyst 126 (2001) 7-10. 

In addition to trialkylboranes, various alkoxyboron compounds have prominent roles in synthesis. Some of these, such as catecholboranes (see. p. 340) can be made by hydroboration. Others are made by organometallic or related substitution reactions. Alkoxyboron compounds are usually named as esters. Compounds with one alkoxy group are esters of borinic acids and are called borinates. Compounds with two alkoxy groups are called boronates. Trialkoxyboron compounds are borates. 

The inhibition of two cholinesterase activities in blood can also be used to confirm exposure to certain organophosphate ester compounds. Red blood cell acetylcholinesterase is the same cholinesterase found in the gray matter of the central nervous system and motor endplates of sympathetic ganglia. Synonyms for this enzyme include specific cholinesterase, true cholinesterase, and E-type cholinesterase. Plasma cholinesterase is a distinct enzyme found in intestinal mucosa, liver, plasma, and white matter of the central nervous system. Synonyms for this enzyme include nonspecific cholinesterase, pseudocholinesterase, butyrylcholinesterase, and S-type cholinesterase (Evans 1986). Nonspecific cholinesterase is thought to be a very poor indicator of neurotoxic effects. 

Organophosphate Ester Hydraulic Fluids. Neurotoxicity is a concern from acute dermal, inhalation, or oral exposure to organophosphate ester hydraulic fluids because of the well-established susceptibility of humans to the cholinergic and delayed neuropathic properties of certain organophosphate ester compounds... 

Products may be either mixtures of phosphate ester compounds resulting directly from the manufacturing process or mixtures resulting from post-blending or compounding with additives. 

The synthesis of organophosphate ester compounds dates to the mid-1800s. From an early date, the most commercially useful compounds for lubricants, plasticizers, and hydraulic fluids were in the chemical family of the tertiary esters. Before 1970, products were introduced based on alkyl aryl phosphates that... 

Ethoxylated multi-ester compounds (so-called oligo-soaps ) have been promoted recently as dispersing/le veiling agents [114]. These contain a multi-branched hydrophobe with... 

Table 12.6 Comparison of characteristic properties of mono-ester and multi-ester compounds [114]...

Sawada, K., et al. Recognition of L-amino acid ester compounds by rat peptide transporters PEPT1 and PEPT2. J. Pharmacol. Exp. Ther. 1999, 291, 705-709. 

Fluorophenyl esters react with amine-containing molecules at slightly alkaline pH values to give the same amide bond linkages as NHS esters (Reaction 15). However, in most cases, the fluorophenyl ester compound will display better stability toward hydrolysis in aqueous solution. It has been reported that a TFP ester has over twice the half-life in basic pH buffers (pH 8) than a corresponding NHS ester on the same compound (Molecular Probes). 

Fluorophenyl ester compounds can be coupled to amines at a pH range of 7-9, with 0.1 M sodium bicarbonate, pH 8, a suggested reaction medium. 

An alternative method of modifying proteins to contain alkynyl groups is to use the propargyl-PEGj-NHS ester compound described in Chapter 18, Section 2. This reagent will react spontaneously with available amine groups in proteins to form an amide bond without the need to use EDC, as in the following protocol. 

Figure 18.3 Homobifunctional NHS ester compounds containing PEG spacers for water solubility.

NHS-ester compounds to study protein interactions. These bis-NHS-PEG compounds may provide a superior crosslinker for studying such interactions due to their water solubility and the fact that the PEG bridge won t get buried in hydrophobic pockets on proteins or within hydrophobic membrane structures. 

The NHS ester compounds are sensitive to hydrolysis in aqueous solution, and they likely will hydrolyze faster than more hydrophobic biotinylation compounds due to their hydrophilic-ity. If a stock solution is made at a higher concentration to facilitate the addition of a small amount to a reaction solution, the initial solution should be made in a water-miscible organic solvent that is dried with a molecular sieve. Suitable solvents include DMAC, DMSO, or DMF. If using DMF, use only highly pure solvent, as it may contain amines that can react with the NHS ester groups (Figure 18.13). 

In addition, the PEG-based heterobifunctional crosslinkers described in Chapter 18, Section 2, provide enhanced water-solubility for antibody conjugation applications. Conjugation of antibody molecules using a maleimide-PEG -NHS ester compound actually increases the solubility of the antibody and may help to maintain stability for certain sensitive monoclonals better than the traditional aliphatic crosslinkers. The methods described below for SMCC may be used with success for PEG-based reagents or other maleimide-NHS ester heterobifunctionals. 

An organic (ester) compound used as a plasticiser in nitrile rubbers and in polyvinyl chloride. A/,AT-Dibutylthiourea DBTU, accelerator. 

The CT behaviour of three alkyl esters or amides of diatrizoic acid (Fig. 1) in rabbits after i.v. injection of 3 mL kg (89 mgl mL ) was reported by Gazelle in 1994 [28]. The particles had sizes of 200-300 nm. The ester compound with the short alkyl chain circulated for a long time in the blood, and the ester with the longer chain was rapidly taken up by the Ever achieving CT densities in this organ of more than 225 HU. The amide showed a blood-pool behaviour similar to that of the short-chain ester. The ethyl ester of diatrizoic acid (EEDA), formulated as a nanoparticulate contrast agent with a diameter of 200 nm, was positively tested in a rabbit model with Ever abscesses [30]. EEDA proved to be superior to iohexol in detecting these abscesses. 

Alkoxyboron compounds are usually named as esters. Compounds with one alkoxy group are esters of borinic acids and are called borinates. Compounds with two alkoxy groups are... 

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