Gourmets
appreciate the typical orangey-red color of salmon, shrimp
and lobster. The appetizing appearance of these seafood specialties
is due to the carotenoid astaxanthin which the creatures
take up with their diet. BASF scientists have developed an exciting
and complex new way of synthesizing astaxanthin. Thanks
to this new process, BASF is one of only two companies in
the whole world with the capacity for industrial production
of the carotenoid from scratch by chemical synthesis.
Feed
additive for fish farming
To
ensure that farmed fish look and taste like their wild
counterparts, the fish feed must contain all the essential components
of a natural diet. These needs are taken care of by feed
additives such as astaxanthin. Astaxanthin acts as a provitamin
A for salmon and as such is an important element for health,
growth and reproduction.
Astaxanthin is also one of the most potent natural antioxidants
and has already been approved in the USA as a food supplement.
Expertise
and technology
The
astaxanthin process is one of BASF's most complex.
Its 14 steps make it the longest synthesis sequence
for the production of a single substance. Despite the complex
synthesis route, planning and construction of the production
plants began after only five years of process development.
A bioavailable form of astaxanthin was developed rapidly thanks
to BASF's existing expertise in carotenoid product
development.
Although it is BASF policy wherever possible to replace chemical
synthesis with fermentation for the manufacture of natural
substances (an example is vitamin B2), fermentative processes
are not always effective enough to take the place of a complex
chemical synthesis for full-scale production. BASF therefore
continues to count on the strength of its conventional
chemical synthesis know-how and extensive technology
platform.
Convergent
synthesis strategy
Natural astaxanthin occurs in different stereoisomeric forms.
Therefore, no steric control is required in the synthesis
of the chirality centers. The most efficient method
for constructing symmetrical C40 carotenoids is double
Wittig condensation of a symmetrical C10 dialdehyde as
a central C10-element with two equivalents of a C15 phosphonium
salt. Sensitive substitution patterns like the oxidation-sensitive
-ketol group are the special challenge in the synthesis
process.
-ketol group are the special challenge in the synthesis
process.
