Piperazine chemical structure

Hj histamine receptor blockers can be grouped according to their chemical structures ethanolamine derivatives (diphenhydramine, clemastine) ethylenediamine derivatives (tripe-lennamine, pyrilamine) alkylamines (chloropheniramine, dexchlorpheniramine, brompheniramine) piperazines (cycUzine, meclizine, hydroxizine) phenothiazines (promethazine, trimeprazine) piperidines (cyproheptadine, diphenylpyraline) and others that do not belong to a specific chemical classification (terfenadine, astemizole). 

Fig. 4.8 Chemical structures of commonly used piperazine derivatives.

Chemicals known as piperazines have industrial applications worldwide, and it is legal to purchase bulk quantities of these chemicals on the Internet for this purpose. By changing chemical groups added to the basic piperazine skeletal structure, different chemicals can be formed that vary considerably in their industrial, medical, and mind-altering properties. Piperazine citrate and related compounds destroy intestinal worms, making these chemicals useful in both medical and veterinary preparations. Other medicinal and mind-altering qualities of piperazines are being exploited as possible treatments of depression, psychosis, Alzheimer s disease, and tumors. 

The early antihistamines. Hi histamine receptor antagonists, bore some structural resemblance to histamine and, like histamine, contained an ethylamine group. However, the structures of the many antihistamines that are available are disparate, and the traditional classification according to chemical structure (ethanolamine, ethy-lenediamine, alkylamine, piperazine, and phenothiazine) is outdated, since the second-generation antihistamines, such as terfenadine and astemizole, do not readily fit into the old classification system (2). 

Chemical Structure C17H18FN3O3-HCl H2O. Ciprofloxacin has a fluorine atom at the 6-position, a piperazine moiety at the 7-position, and a cyclopropyl ring at the 1-position... 

HALS hardly absorb UV light but act most likely as radical scavengers and hydroperoxide decomposers. Chemical structures are mainly based on piperidines. Sterically hindered piperazines are known as well (Fig. 11.15). Secondary amines are the most common structures, but alkyl-amines or, more recently, alkoxyamines are commercially... 

Abstract Piperazines and its congeners, (di)keto piperazines are valuable tools in drug discovery, providing a natural path for the process peptide > peptidomimetic > small molecule also called depeptisation. Moreover, they can provide molecular probes to understand molecular pathways for diseases of unmet medical need. However, in order to better understand the design of such value added compounds, the detailed understanding of scope and limitation of their synthesis as well as their 3D structures and associated physicochemical properties is indispensables. Isocyanide multicomponent reaction (MCR) chemistry provides a prime tool for entering the chemical space of (di)(keto)piperazines since not less then 20 different ways exist to access a diversity of related scaffolds. 

Compared with monocyclic piperazine scaffolds, bicyclic piperazines often provide platforms with even more points of diversity compared to monocyclic piperazines. Condensed bicyclic piperazines enlarge the chemical space of piperazine scaffolds, as well as the family of target proteins. For example, bicyclic piperazinones were prepared and evaluated in vitro and in vivo as thrombin inhibitors [49]. The cocrystal structure of a bicyclic piperazinone inhibitor 154 with thrombin was shown in Fig. 9. So far, chemists have developed many MCR methods to synthesize a variety of bicyclic piperazine scaffolds. 

Piperazines and derivatives are archaetypical scaffolds and can be considered as efficient, however, structurally simple peptidomimics. The scaffolds combine conformational rigidity with peptide-like spacial placement of amino acid side chains or isosteres thereof. Moreover, piperazines can be used to confine compounds with beneficial properties such as water solubihty. Piperazines are therefore in the center of synthetic interest and many different synthetic pathways have been designed [16-19]. A preferred way to synthesize different piperazine scaffolds with plenty of variabihty provides MCR chemistry. Several piperazine scaffolds are currently only accessible by isocyanide-based MCR. Likely they could be assembled by sequential synthesis as well however, the synthetic efficiency, the diversity, and the size of the alternative chemical space will be inferior. The application of... 

Cyclols Stable molecules obtained by the addition of a heteroatom nucleophile to the carbonyl group of lactams are not very common. The side-chain moiety of the ergot alkaloids (e.g., 50) is one of the earliest examples of such a cyclolic structure (75FOR51) identified. This has given rise to a number of studies on the synthesis and chemical transformations of such units. The discussion below is confined to cyclols related to or arising from piperazine-2,5-diones. 

Substituting different chemical groups onto the basic piperazine structure creates piperazine derivatives... 

Chemical Name l-(Diphenylmethyl)-4-(3-phenyl-2-propenyl)piperazine Common Name -Structural Formula ... 

The first reaction leads to pol5q)eptides, the second to N, methylglycyl diglycyl glycine. The tetrapeptide will also form amorphous pol3mier when heated to temperatures close to its melting point of 205° C (77). The loss of the methyl alcohol is thus not the reason for the loss of order. A period of mobility before polsmierization is also unlikely, since on reaction in solution only piperazine-2,5-dione is the major product (20). The reactions of the crystalline tri- and tetrapeptide are thus topo-chemical, but no transition from the monomer to the polymer crystal structure seems possible under the chosen reaction condition. 

A comparison of the structures in Table 10-16 illustrates their heterogeneity. From a chemical standpoint they can be divided into four main groups the dihydropyridines (e.g., nifedipine), the arylalkylamines, the piperazines, and the benzothiadiazines. There are others. 

Chemical Name 1 -(4-Amino-6,7-dimethoxy-2-quinazollnyl)-4-(2-furanylcarbonyl)piperazine Common Name Furazosin Structural Formula ... 

There is a close structural affinity between ibotenic acid and its dihydro derivative, tricholomic acid (mp 207°C). Nevertheless the chemical interrelation between these compounds appeared to be difficult to prove because of the reactivity of the N—O bond which undergoes hydrogenolysis on mild catalytic hydrogenation of ibotenic acid (Scheme 13). The a-amino ketone formed in this way undergoes decarboxylation, dimerization, and reduction, becoming a trans derivative of piperazine 48). Tricholomic acid and its threo isomer have been synthesized from erythro- and f/ireo-diethyl D,L-3-hydroxyglutamate, respectively, by Iwasaki et al. 49). 

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