Combinatorial Chemistry Review

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Radiofrequency Encoding
Strategy for identifying library members by physically associating them with a set of electronic devices which emit characteristic radiofrequency signals upon stimulation with a radiofrequency energy source. These signals can be used to track the reaction history of each sample in a synthesis.

Ratio Coding
Encoding strategy in which the relative quantities of tags convey information about compound identity. In comparison to binary coding, more information may be obtained from a given tag set, but tag interpretation is more complex.

A molecule within a cell or on a cell surface to which a substance (such as a hormone or a drug) selectively binds, causing a change in the activity of the cell.

Reagent Efficiency
The ratio of the number of library members prepared compared to the number which would have been prepared in a fully combinatorial library using the same building blocks. Lower reagent efficiency may be desirable in order to reduce the number of compounds to be synthesized or tested, for example by maximizing the number of members expected to have high activity in a library prepared by parallel synthesis.

Reagent Partitioning
Phenomenon whereby the concentration of a compound within, for instance, a particle of solid support is higher or lower than of the bulk solution due to the physicochemical properties of the solid support.

Recursive Partitioning
Process for identifying complex structure-activity relationships in large sets by dividing compounds into a hierarchy of smaller and more homogeneous sub-groups on the basis of the statistically most significant descriptors.

a) Portion of a chemical structure which can be identified as being derived from a particular building block;
b) portion of a building block which is incorporated into the final product but is not part of the scaffold.

Insoluble polymeric material which allows ready separation from liquid phase materials by filtration; can be used to carry library members (i.e. solid support) or reagents, or to trap excess reagents or reaction by-products.

Preparation of individual members or pools of a combinatorial library, normally to follow up on some property of interest identified in initial screening, and often in larger scale and/or greater purity than the original preparation.

Robotic System
Automated device where materials are transferred by the physical movement of a delivery device relative to the ultimate receptacle, or vice versa.

Rules of Five: Lipinski's rules
Set of criteria for predicting the oral bioavailability of a compound on the basis of simple molecular features (molecular weight, c Log P, numbers of hydrogen-bond donors and acceptors). Often used to profile a library or virtual library with respect to the proportion of drug-like members which it contains.