Synthesis
The first total
syntheses of beta-carotene were reported in 1950 by
Karrer and Eugster, Inhoffen et al and Milas et al .
There are now many methods known, and beta-carotene is produced industrially
on a large scale.
Beta-carotene contains 40 carbon atoms, ie it is a C40
carotenoid. There are numerous methods of joining two or three
smaller molecules to give the required carbon skeleton. These can
be classified as symmetric or unsymmetric. An example of a symmetric
synthesis would be
C16
+ C8 + C16 = C 40
whereas an unsymmetric
synthesis would be
C25
+ C15 = C40
Here are two examples of industrial syntheses. The first was developed
by the Badische Anilin- & Soda-Fabrik (
BASF) and is based on the Wittig reaction. The second is a Grignard
reaction, elaborated by F. Hoffman-La Roche & Co. Ltd (
Roche) from the original synthesis of Inhoffen et al.
They are both symmetrical; the BASF synthesis is C20 + C
20 , and the Roche synthesis is C19 + C2 +
C 19 .
BASF Synthesis
Roche synthesis