CAVEAT base atom

Because rigid pharmacophoric searching is based on the positions of explicit atoms or points, it is often difficult to pose queries based on directed vectors in space. A specialized search system, CAVEAT, has been developed that permits the specification of queries based on the relative orientation and position of bond vectors in space. If the query bond vectors have been derived from a docked flexible ligand, then when a database of rigid ring-systems (CAST-3D or CSD) is searched, CAVEAT will identify potential substructural skeletons which could act as a rigid mimic of the core substructure of the ligand. 

The aldol reaction is another class of reactions used to highlight AE, as all the atoms in the reactants end up in the product. One should note though that this transformation comes with a number of caveats. Typically, a stoichiometric base is required to form the reactive enolate, and for many asymmetric aldols, a chiral auxiliary is utilized. Although this auxiliary is present in the product after the reaction, it is usually cleaved in a subsequent step and discarded to waste. An example of innovation to address both of these issues is the asymmetric aldol reaction using a zinc-Pro-Phenol... 

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