Bonds ester

The search in the Theilhcimer reaetion database [62] provides 161 reactions for this query. If the search is performed without any additional bond spheres (covering only atoms of the inner sphere with a dark gray bac kgroiind in Figure 10.3-42 as well as the added atom groups on the precursor side), 705 reactions arc obtained in the Theilhcimer database. The result of this search is less precise than that of the first search. Additionally, reactions forming any kind of C-0 bonds (c.g., making an ether bond instead of an ester bond) arc found. However, in both searches too many hits arc obtained in order to detect suitable reactions in a reasonable... 

More successful are solid-phase methods in which the linear precursor is attached through a labile ester bond (e.g. o-nitrophenyl) to a polymer. 

This difference m reactivity especially toward hydrolysis has an important result We 11 see m Chapter 27 that the structure and function of proteins are critical to life Itself The bonds mainly responsible for the structure of proteins are amide bonds which are about 100 times more stable to hydrolysis than ester bonds These amide bonds are stable enough to maintain the structural integrity of proteins m an aqueous environment but susceptible enough to hydrolysis to be broken when the occasion demands... 

Polyester (Section 20 17) A polymer in which individual structural units are joined by ester bonds Polyether (Section 16 4) A molecule that contains many ether linkages Polyethers occur naturally in a number of antibi otic substances... 

Synthesis of Silicone Monomers and Intermediates. Another important reaction for the formation of Si—C bonds, in addition to the direct process and the Grignard reaction, is hydrosdylation (eq. 3), which is used for the formation of monomers for producing a wide range of organomodified sihcones and for cross-linking sihcone polymers (8,52—58). Formation of ether and ester bonds at sihcon is important for the manufacture of curable sihcone materials. Alcoholysis of the Si—Cl bond (eq. 4) is a method for forming silyl ethers. HCl removal is typically accomphshed by the addition of tertiary amines or by using NaOR in place of R OH to form NaCl. 

Carboxylate soaps are most commonly formed through either direct or indirect reaction of aqueous caustic soda, ie, alkaH earth metal hydroxides such as NaOH, with fats and oils from natural sources, ie, triglycerides. Fats and oils are typically composed of both saturated and unsaturated fatty acid molecules containing between 8 and 20 carbons randomly linked through ester bonds to a glycerol [56-81-5] backbone. Overall, the reaction of caustic with triglyceride yields glycerol (qv) and soap in a reaction known as saponification. The reaction is shown in equation 1. 

Carboyylic acid ester hydrolysis is frequendy observed as the initial reaction for pesticides with ester bonds, such as 2,4-D esters, pyrethroids, and DCPA (dacthal) (8) (eq. 11) (16). 

The principal pathway for the decomposition of aspartame begins with the cleavage of the ester bond, which may or may not be accompanied by cyclization (Eig. 2). The resultant diketopipera2ine and/or dipeptide can be further hydroly2ed into individual amino acids (qv). 

However, the term cycHc depsipeptide is often used ia the Hterature to refer to heterodetic homomeric peptide lactones ia which ester bonds to amino acid hydroxyls are present ia the ring. 

Polyester (Section 20.17) A polymer in which individual structural units are joined by ester bonds. 

FIGURE 10.39 Structures of several ioiiophore antibiotics. Valinotnycin consists of three repeats of a four-unit sequence. Because it contains both peptide and ester bonds, it is referred to as a depsipeptide. 

FIGURE 12.35 Amino adds are linked to the 3 -OH end of tRNA molecnles by an ester bond formed between the carboxyl group of the amino acid and the 3 -OH of the terminal ribose of the tRNA. 

It is believed that the recombination product is liable (due to the increased mobility of the hydrogen atom following the carbon atom in j3-position relative to the C—O—C bond) to isomerization and decomposition along the ester bond ... 

Poly(L-malic acid) denotes a family of polyesters derived from L-malic acid as the building unit. By chemical synthesis, three kinds of poly(L-malic acid) have been obtained, depending on the molecular position of the ester bond the a-type(I) [1], the j8-type(II) [2], and the a,j8-mixed-type(III) [3). 

The assay for ester bonds is more convenient at this stage [4,10). 

Q A Boc-protected amino acid is covalently linked to the polystyrene polymer by formation of an ester bond (Sn2 reaction). 

After the desired peptide has been made, treatment with anhydrous HF removes the final Boc group and cleaves the ester bond to the polymer, yielding the free peptide. 

Cardiolipins are a group of lipids found in heart muscles. What products would be formed if all ester bonds, including phosphates, were saponified by treatment with aqueous NaOH ... 

Step 5 The final step is removal of all protecting groups and cleavage of the ester bond holding the DNA to the silica. All these reactions are done at the same time by treatment with aqueous NH3. Purification by electrophoresis then yields the synthetic DNA. 

Esterase enzymes - cleavage of various ester bonds to yield an ackf and an alcohol, ie R1COOR2 + H2O <---------------------------> RiCOOH + R2OH... 

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