Organic Synthesis Exploration Tool









Computer-Assisted Organic Synthesis (CAOS)

What is Computer-Assisted Organic Synthesis?

CAOS was born in the late 1960s, when E. J. Corey and T. Wipke created the first CAOS program, OCSS (Organic Chemistry Synthesis Simulator). Since then, a few dozen CAOS programs have been developed. Most of them are academic projects and run in expensive computers such as the VAX or the PD-10. On the other hand, a few commercial programs for the PC have appeared recently, such as Syntree or HOLOWin. As far as we know, OSET is the first open source project in this field.

The aim of an CAOS program is to assist the chemist in the design of the synthetic pathway for a complex target molecule. Most programs work in the retrosynthetic direction, that is, from target molecule to simple precursor, in a process opposite to the one actually done in the laboratory. Some examples of these programs are LHASA, SYNGEN, SYNCHEM, and OSET. A few programs work in the synthetic direction: some attempt to predict reactions given a set of reactants and conditions (like CAMEO); others try to find a synthetic pathway from designated starting materials searching in the synthetic direction. Some programs try to combine both approaches (e.g., WODCA).

In order to do its job, a CAOS program must solve most of the following problems:

  • Structure input and output (usually via a graphic user interface)
  • Internal representation of molecules and transforms
  • Canonicalization
  • Perception of atom types, functional groups, rings, strategic bonds, etc.
  • Transform evaluation
  • Synthetic tree management
  • Strategies

Some day we will describe these topics in detail.

Last update: 8/3/2000