Application of methyl in drug design

The methyl group plays an important role in the rational drug design.  Introducing methyl into small molecules has become an important strategy of lead compound optimization.  The application of methyl in drug design is reviewed in this paper.  Methyl can modulate the physicochemical, pharmacodynamic, and pharmacokinetic properties by ortho effect, inductive effect, and conformational effect.  It also improves the metabolic stability as a soft metabolic point.  In addition, introducing methyl into drug molecules can also be applied as a strategy in new uses of old drugs and generate me-too drugs.