Isosterism concepts

B. The isosterism concept atoms or groups A. Structural parameters... 

Starting in 1932, Erlemneyer published a series of detailed studies about the isosterism concept, and particularly. 

Erlemneyer also proposed three expansions of the isosterism concept ... 

Recognizing the usefulness of the isosterism concept in the design of biologically active molecnles, Friedman proposed to call bioisosteres componnds... 

The apparent failure of the isosterism concept for the inactive thiophene, inversed furan and pyrimidine is thus interpretable on a rational basis. In Table 15.10 are listed some more exotic examples of bioisosteric replacements of cyclic systems. 

The synthesis and local anesthetic properties of at least one acylanilide compound, nir-vanine, was reported even before procaine (1900). However, the amide isostere concept was not seriously pursued for over three decades. 

Starting in 1932, Erlenmeyer published a series of detailed studies on the isosterism concept, and particularly about its first applications to biological problems. Erlenmeyer proposed his own definition of isosteres as elements, molecules or ions in which the peripheral layers of electrons may be considered identical. Erlenmeyer also proposed three expansions of the isosterism concept ... 

In conclusion, it became evident to the physicists that the concept of isosterism, developed before quantum-mechanical theories, could not provide at the molecular level the same results as those that the periodic classification had provided for the elements, namely a correlation between electronic structure and physical and chemical properties. In the field of medicinal chemistry the isosterism concept, taken in its broadest sense, has proved to be a research tool of the utmost importance. The main reason for this is because isosteres are often much more alike in their biological than in their physical and chemical properties. An illustrative example is found in the comparison of oxazolidine-diones and hydantoins which possess different chemical reactivities, but present a similar antiepileptic profile (Fig. 13.2). 

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