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Nitric Acid Synthesis - YouTube
One of the most rapidly expanding areas is the development of peptide-based agents for targeted imaging. Metal and halogen radionuclides such as 64Cu, 89Zr, 99mTc, 111In, 18F, and 124I are most commonly used for the design of the agents. Typically, the metal ion coordination chemistry is straightforward and mild. However, it requires attachment of a rather bulky chelator to the vector molecule what may deteriorate the biological activity. Simple direct iodination has been used for decades introducing minor modification at tyrosine amino acid residue though demonstrating poor residualizing of the radioactive iodine catabolites in the cell. On the contrary hydrophilic complexes of radiometals stay trapped in the cell after the degradation of the internalized imaging agent. The incorporation of 18F can be accomplished by the conventional nucleophilic or electrophilic addition, or via prosthetic groups . However, the synthesis might be rather complex with harsh conditions and high macromolecule concentration. A novel method utilizing similarity of Al18F2+ with metal cations and thus possibility of coordination labelling chemistry has potential for kit type production like radiometals . The relatively long half-life (110 min) of 18F enables centralized production and distribution of either the radionuclide or prepared imaging agents to the satellite clinical centres. Most of the PET agents used in clinical studies are 18F-based. Nevertheless, the simpler labelling chemistry of 68Ga and its availability from the generator system which can be used even at distant and isolated medical centres make 68Ga more preferable.
Sulfa drugs arrest cell growth by inhibiting the synthesis of folic acid, a component required for growth by bacteria. Folic acid is a large molecule and is unable to enter bacterial cells, so the bacteria must synthesize the compound intracellularly.
Animal cells are unable to synthesize folic acid and it must be provided in the diet. For this reason sulfa drugs are not toxic to animal cells.
The synthesis of para‐aminosalicylic acid
Alcohol oxidation is an important organic reaction because more than 90% of the ethyl alcohol that enters the body is metabolized by oxidation to acetic acid (Peters and Preedy, 1998). In terms of oxygen and hydrogen transfer, oxidation is a process of gaining oxygen or losing hydrogen atoms while reduction is a process of losing oxygen or gaining hydrogen atoms. We find this easy to remember using the acronym “OIL RIG:” Oxidation Is a Loss (of hydrogen atoms), Reduction Is a Gain (of hydrogen atoms). Although these are old definitions that are not used very much in current texts, we often will come across them in organic chemistry. As Scheme 1 shows of primary alcohols, removal of two hydrogen atoms (one from the hydroxyl group and another from the hydroxyl-bearing carbon atom) results in an aldehyde. In the presence of water, the aldehyde will transform into aldehyde hydrate, from which two hydrogen atoms are removed (one from the hydroxyl group and another from the hydroxyl-bearing carbon atom) to result in a carboxylic acid. The net effect for the second oxidation from the aldehyde to the carboxylic acid is the insertion of an oxygen atom. In the human body, this process happens in the liver and is mainly catalyzed by alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH), respectively (Xiao, 1996).
Amides are formed by the condensation reaction between a carboxylic acid and an amine (primary or secondary amines, or ammonia). Water is formed as a byproduct from the carboxylic acid –OH and the amine –H (Scheme 5). It could be very easy to understand amide formation if you recall the ester formation reaction (Scheme 3). However, unlike ester formation, the amide reaction equilibrium is highly unfavorable for the synthesis of products because a competing acid-base reaction occurs between a carboxylic acid and amine. Many methods are thus used to drive the reaction to the right. For example, either acid chloride or acid anhydride is used as a more reactive carboxylic acid derivative to prepare amides. In a similar way, the amide bond is formed between the carbonyl carbon and the amine nitrogen while the –Cl joins –H to form HCl (when using acid chloride) or the RCOO– joins –H to form a carboxylic acid (when using acid anhydride) (Scheme 5). In addition to learning these concepts in lecture, students engage in laboratory experiments such as the synthesis of nylon from adipoyl chloride and hexamethylemediamine that serve as good strategies to reinforce the concept of amide formation and solidify student understanding of this reaction.
PDF Downloads : Oriental Journal of Chemistry
294. Shetty D, Jeong JM, Ju CH, Lee YS, Jeong SY, Choi JY. . Synthesis of novel 68Ga-labeled amino acid derivatives for positron emission tomography of cancer cells. 2010;37:893-902
134. Knor S, Modlinger A, Poethko T, Schottelius M, Wester HJ, Kessler H. Synthesis of novel 1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) derivatives for chemoselective attachment to unprotected polyfunctionalized compounds. 2007;13:6082-90
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Prospective of 68Ga-Radiopharmaceutical Development
The other approach is to introduce backbone protecting groups which will prevent the formation of hydrogen bonds. Such protection is made by the introduction of the Hmb group on the αnitrogen . It has been shown that the presence of a Hmb unit every 6-7 residues is sufficient to disrupt the peptide aggregation . The Hmb protected amino acid is introduced under the form of N,O-bis-Fmoc-N-(2hydroxy-4-methoxybenzyl) derivative, the O-Fmoc protection being cleaved during the following piperidine treatment. At the end of the synthesis the Hmb group is cleaved in the final TFA cleavage.
Aquarium Medications Part 2 | Antibiotic & …
295. Shetty D, Jeong JM, Ju CH, Kim YJ, Lee JY, Lee YS. . Synthesis and evaluation of macrocyclic amino acid derivatives for tumor imaging by gallium-68 positron emission tomography. 2010;18:7338-47
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