Nonclassical bioisosteres

Importantly, the nonclassical bioisosteres are preeisely the replaeements of functional groups not falling within the regimen by classical definitions. Although, several of these functional moieties practically just behave as one of the following characteristic specific features, such as  

The r /is-diethylstilbesterol, the presenee of two phenolie hydroxy functions veiy closely mimic the correct orientation of the phenolic and alcoholic functions present in the natural oestradiol. However, it is not accomplished by the corresponding cis-diethylstilbesterol, besides some other more flexible analogues that practically show no activity at all.  

From the above typical example it is quite evident that — 

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Bioisosteric Replacement and Nonisosteric Bioanalogs (Nonclassical Bioisosteres), 689... 

BIOISOSTERIC REPLACEMENT AND NONISOSTERIC BIOANALOCS (NONCLASSICAL BIOISOSTERES)... 

Replacement of the methyl ester moiety of the muscarinic partial agonist arecoline (16) by the putative nonclassical bioisosteric 1,2,4-oxadiazole ring system (18), where R = un-... 

Compounds (21-23) illustrate further examples of nonclassical bioisosteres. Compound (21) was reported to display antitrypanosomal activity (18). The analogs (22) and (23) also displayed antitrypanosomal activity (19). Compound (22) demonstrated the most impressive activity (IC50 values of 40 and... 

Heterocycles as nonclassical bioisosteres of a-amino acids 13CMC205. 

Figure 9.3 Structural analogs of nonclassical bioisosteric replacement.

Analogously, the triazole derivatives 5 and 6 have been shown to act as a nonclassical bioisosteres of the ester group as in arecoline 4, a muscarinic agonist [20, 21]. 

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