Privileged substructures, structure-activity

In the technique of post hoc design, a set of descriptors are built up by examination of a set of compounds active at a particular receptor family or sub-class. Normally, the set of drugs would be from a commercial database such as MDDR or the Merck Index, etc. and the descriptors would usually be substructural fragment or key based. One example would be the GPCR-PA+ sub-class referred to above, where BCUT descriptors have been used to aid the design of a focused library of aroimd 2000 compoimds based on 8 scaffolds. Libraries have also been constructed based on peptidomimetic principles as well as on the concepts of privileged structures. ... 

The retrospective analysis of the chemical structures of the various drags used in medicine led medicinal chemists to identify some molecular motifs that are associated with high biological activity more frequently than other structures. Such molecular motifs were called privileged structures by Evans et al. [2], to represent substructures that confer activity to two or more different receptors. The implication was that the privileged structure provides the scaffold and that the substitutions on it provide the specificity for a particular receptor. Two monographs deal with the privileged structure concept [3, 4]. 

Privileged structure is a substructure feature found in biologically active molecules. See for exanq>le, Lewell, X.Q. Judd, D.B. Watson, S.P. Hann, M.M. J. Chem. Inf. Comput. Sci. 1998, 511. 

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