ChemAxon developed a unique virtual reaction technology that could be applied in various areas of molecule transformations. Reactor is a virtual combichem application providing synthetically feasible products using generic reactions. No reagent selection is required, and built in rules can provide chemo- regio- and stereospecificity during the library enumeration progress. A new application using the same reaction engine is introduced for the first time for the prediction of metabolic stability and xenobiotic metabolites. For latest developments see: http://www.chemaxon.com/product/reactor.html