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OH
O
H
HO
O
O
H
O
OH
O
OH
O
HO
O
O
OH
O
OH
O
HO
Crocin
3.7
O
HO
O
OH
HO
OH
COOH
Norbixin
3.8
COOH
O
CH
2
OH
O
Bastaxanthin sulfate
3.9
Na
+-
O
3
HSO
SCHEME 3.2
(Liaaen-Jensen 1971), syntheses with carotenoids were often troubled by unexpected difi culties
leading to disappointing low product yields (Widmer et al. 1982). Nevertheless, the carotenoid
chemist's code of conduct has been increasingly violated in recent years. Still, those neophytes who
look at the synthetic schemes and think of straightforward and trouble-free organic reactions may
keep in mind that even ester hydrolysis of carotenoids can become unexpectedly difi cult (Larsen
et al. 1998, Reddy et al. 2002). The initial topic of a PhD thesis was abandoned for the simple
enough reason that it was not possible to i nd an appropriate method for hydrolyzing ethyl esters of
long chain carotenoid diacids (Meister 2004). At times, well-established reactions do not succeed
when employed with carotenoids and, occasionally, customary work-up procedures fall short of
expectations; compare Sliwka and Liaaen-Jensen (1993a,b) with Kildahl-Andersen et al. (2004) and
Liaaen-Jensen (1996) with Oliveros et al. (1994).
There are two approaches to synthesizing hydrophilic carotenoids: (1) appending a hydrophilic
group to the carotenoid scaffold (Foss et al. 2006a) or (2) joining a carotenoid to a hydrophilic
compound, Scheme 3.3 (Foss et al. 2003). Whereas the Scheme 3.3 intuitively explains the dif-
ference, these techniques cannot be clearly separated in praxis; the distinction may appear more
emotional than conceptual. Both methods are habitually hampered by low yields, i nd their limits in
the availability of functionalized carotenoids, and cause problems in the work-up procedure due to
the amphiphilic character of the products.
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