The chance of discovering a new drug is 1 in 10,000 and development
costs about 40 million dollars per new drug. This gives the emphasis on
the development of new scientific approaches in the discovery of new
drugs, "Drug design". It involves the study of the effects of
biologically active compounds on the basis of molecular interactions in
terms of molecular structure or its physiochemical properties.The
current trend in drug design is to develop new clinically effective
agents through the structural modification of the lead nucleus which is
a prototype compound that has the desired pharmacological activity but
may have many undesirable characteristics. The identification of such
lead compounds and optimum bioactive position on the basic skeleton is
the area of drug design.