Masanori Arita (firstname.lastname@example.org)
Kiyoshi Asai (email@example.com)
Takaaki Nishioka (firstname.lastname@example.org)
 Electrotechnical Lab.
Tsukuba-shi Umezono 1-1-4, Ibaraki 305-8568, Japan
 Department of Agriculture, Kyoto University
Kyoto-shi Sakyo-ku Kitashirakawa, Kyoto 606-8562, Japan
A precursor is a compound which is transformed to a class of functional molecules within short steps. It is an important process in the production of natural drugs to decide whether a given compound is a precursor or not. We present two strategies to select precursor compounds in the secondary metabolism of terpenoids: one is to find the packing of basic molecules in the given cyclic structure, and the other is to find the synthetic map of the given set of compounds. Both strategies play important roles in reproducing tracer experiments on a computer.