Reactions in Medicinal Chemistry

The creation of a peptide bond is a very important reaction in medicinal chemistry and there are many ways to synthesize DKPs. It is very important to prevent the formation of the wrong peptide bond. When two different amino acids are reacted with each other, it can give rise to four different products. It is therefore vital to protect the amino terminal of one and the carboxyl group of the other amino acid. 

What is the importance of diazotization reaction in medicinal chemistry ... 

Tron GC, PiraU T, BiUington RA, Canonico PL, Sorba G, Genazzani AA (2008) Click chemistry reactions in medicinal chemistry applications of the 1,3-dipolar cycloaddition between azides and alkynes. Med Res Rev 28(2) 278-308. doi 10.1002/med.20107... 

Bayer in Berlin, Germany, developed a continuous process for the fiuorination of a steroid derivative tvith bis(methoxyethyl)aminosulfur trifiuoride to produce geminal difiuoride [78]. The goal tvas maximization of conversion and the selection of optimal residence time, temperature, and reagent amount. The continuous reaction vas performed on a laboratory scale, in a 3 mm inner diameter stainless steel tube. As an important reaction in medicinal chemistry, further investigations about a larger scale process are on the vay. 

The three scales devised by Kamlet, Abboud and Taft have been used many times to formulate relationships between reaction rate constants and solvent polarity. These are known as linear solvation energy relationships (LSERs). The rate of amide formation for example, the most common single reaction in medicinal chemistry, is inversely proportional to jS for entropic reasons (Figure 3.4). Limonene and its derivative p-cymene were thus justified as excellent options for a renewable amidation solvent, not only in terms of performance but also because they are produced from a renewable feedstock. Other solvents are less suitable according to their solvatochromic polarity parameters (Table 3.3). As hydrocarbons, some aquatic toxicity concerns surround the use of limonene and p-cymene, but ideally these would be minimised with recycling. 

Slobbe, R, Ruijter, E., Orru, R. V. A. (2012). Recent applications of multicomponent reactions in medicinal chemistry. MedChemComm, 3, 1189-1218. 

Jacobsen has also developed an organocatalysed asymmetric addition of nucleophiles with iV-acyl-iminium ions (Pictet-Spengler) and oxocarbe-nium ions, potentially useful reactions in medicinal chemistry (Scheme 14.97). The mechanism involves the formation of an anionic catalyst-chloride complex which acts as a chiral counter ion directing the approach of nucleophiles to one face of the cationic species. 

Urea derivadves are of general interest in medicinal chemistry. They may be obtained cither from urea itself (barbiturates, sec p. 306) or from amines and isocyanates. The latter are usually prepared from amines and phosgene under evolution of hydrogen chloride. Alkyl isocyanates are highly reactive in nucleophilic addidon reactions. Even amides, e.g. sulfonamides, are nucleophilic enough to produce urea derivatives. 

The Corey-Chaykovsky reaction incited some applications in medicinal chemistry. During the synthesis of analogs of fluconazole, an azole antifungal agent, treatment of 49 with 1 led to the corresponding epoxide, which was subsequently... 

On the other hand, heterocycles are of paramount importance to medicinal and agricultural chemists. This comprehensive and authoritative treatise provides a one-stop repository for name reactions in heterocyclic chemistry. Each name reaction is summarized in seven sections ... 

Esters of tropine have a venerable place in medicinal chemistry. One such compound, cocaine, the object of some current interest, was the natural product lead which led eventually to most of today s local anesthetics. A distantly related analogue is prepared by reaction of tropine (132) with 3,5-dimethylbenzoyl chloride. This leads to an ester structurally related to another ]ii ominent natural product, atropine (133). The product, tropanaerin (134), is described as an iinti.serotonergic agent intended for antimigraine use [34]. 

Replacement of a benzene ring by its isostere, thiophene, is one of the more venerable practices in medicinal chemistry. Application of this stratagem to the NSAID piroxicam, gives tenoxicam, 136, a drug with substantially the same activity, nie synthesis of this compound starts by a multi-step conversion of hydroxy thiophene carboxylic ester 130, to the sulfonyl chloride 133. Reaction of that with N-methylglycinc ethyl ester, gives the sulfonamide 134. Base-catalyzed Claisen type condensation serves to cyclize that intermediate to the p-keto ester 135 (shown as the enol tautomer). The final product tenoxicam (136) is obtained by heating the ester with 2-aminopyridine [22]. 

The amination of aromatic hydroxy-N-heterocycles is a standard reaction in medicinal and agricultural chemistry and has heen reviewed [36]. The hitherto commonly used two-step procedure for amination of hydroxy-N-heterocycles, starts with conversion into the chloro-N-heterocycles, e.g. by treatment of the hydroxy-N-heterocycle with POCI3, PCI5, or SOCI2, followed by reaction with the amine moiety. This methodology has several drawbacks however, for example ... 

This review chapter focuses on the syntheses and reactions of these 5-membered heterocyclic ring systems containing nitrogen and sulfur (or selenium) (reported during 2006). The importance of these 71-rich heterocycles in medicinal chemistry and natural products is also covered. 

Both natural and non-natural compounds with a 2ff,5ff-pyrano[4,3-fc]pyran-5-one skeleton are of interest in medicinal chemistry. Several natural products, such as the pyripyropenes, incorporate this bicyclic ring system. The group of Beifuss has described an efficient microwave-promoted domino synthesis of the 2ff,5H-pyr-ano[4,3-fo]pyran-5-one skeleton by condensation of a,/3-unsaturated aldehydes with 4-hydroxy-6-methyl-2]-f-pyran-2-one (Scheme 6.244) [428]. It is assumed that in the presence of an amino acid catalyst a Knoevenagel condensation occurs first, which is then followed by a 6jr-electron electrocyclization to the pyran ring. While the conventional thermal protocol required a reaction time of up to 25 h (refluxing ethyl... 

Biaryl ethers are a well-known motif in medicinal chemistry. The reaction of p-nitrophenol with 2,4-dichloropyrimidine was performed in a mixture of acetone and water from which the product precipitated after completion. Work-up and isolation of the product was therefore very simple. We also observed the formation of a by-product (depend-... 

Solid-supported technologies are already well established methods in medicinal chemistry and automated synthesis. Over the last couple of years new trends have evolved in this field which are of utmost importance as they have the potential to revolutionize the way chemical synthesis especially for library production is performed. Microchip-based synthesis technologies and multistep sequences with solid-supported catalysts or reagents in flow-through systems are only two spectacular examples. A new approach is the use of solid-supported systems for the scale-up of chemical reactions thereby enabling the rapid and smooth transition from discovery to development units. 

Ab Initio Methods in the Study of Reaction Mechanisms - Their Role and Perspectives in Medicinal Chemistry... 

Due to the importance of this heterocycle in medicinal chemistry, solid-phase synthesis of derivatives based on this condensation reaction have been investigated. The first report in this area uses a sodium benzenesulfinate resin 247 and gives access in five steps and good overall yields to a library of imidazo[l,2- ]pyridines 248 functionalized at C-2 with an enone moiety <2002OL3935>. Later on, the preparation of libraries of compounds related to 250 or 251 from Rink amide resin 249 have been published (Scheme 68) <2003TL6265>. 

Some 40 research articles resulted from Tipson s 18 years at the Mellon Institute, and they demonstrate that he was able to sustain some of his interest in carbohydrate chemistry, and he continued to study the reactions of sulfonic esters with sodium iodide. In 1945 he compiled his published work into a senior thesis for the D.Sc. degree that was awarded by the University of Birmingham. However, a considerable proportion of the research at the Mellon Institute was never published because of patent restrictions. This was particularly true for his work on carbohydrates and other organic compounds conducted after July 1952, when he was assigned to the Parke, Davis and Company Fellowship in Medicinal Chemistry to synthesize potential antiviral and anticancer agents. 

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