The synthesis of vitamin B12

Vitamin B12 synthesis process, not only the existence of a new synthetic technology created the problem, also encountered a traditional organic chemical theory can not explain the theoretical issues. To this end, reference to the Japanese chemist Woodward Kenichi Fukuis "border electronic theory", and his student and assistant with Hoffman proposed the principle of conservation of orbital symmetry, the symmetry of the theory is simple and intuitive to use explained a number of organic processes, such as electricity cyclization reactions, cycloaddition reactions, σ bond migration processes.

 The theory that the outer layer of the reactant molecules the same orbital symmetry, the reaction is easy to, is called "symmetry allowed" outer orbital symmetry of the reactant molecules is inconsistent, difficult to carry out reaction, called "symmetry-forbidden" . The creation of molecular orbital theory, the Hoffman and Kenichi Fukui shared the 1981 Nobel Prize in Chemistry. Because at that time, Woodward had died 2 years, and the Nobel Prize not awarded to scientists who have passed away, so academic that if Woodward was still alive, he will be one winner, as he will become the a small number of scientists the Nobel Prize twice one.

When Woodward synthesis of vitamin B12, a total of nearly a thousand complex organic synthesis experiment, which lasted 11 years, and finally die in a few years ago he realized, completed the synthesis of vitamin B12 complex work. Participate in vitamin B12 synthesis chemists, in addition to Hoffman, there are famous Swiss chemist Eschen Møse (A.Escheni11oser) and so on.