Preparation and (E/Z)-Isomerization of the Diastereoisomers of Violaxanthin

Article abstract of DOI:10.1002/hlca.200490001

Violaxanthin A (=(all-E,3S,5S,6R,3′S,5′S,6′ R)-5,6:5′,6′-diepoxy-5,6,5′,6′-tetrahydro-β, β-carotene-3,3′-diol = syn,syn-violaxanthin; 5) and violaxanthin B (=(all-E,3S,5S,6R,3′S,5′R,6′S)-5,6:5′, 6′-diepoxy-5,6,5′,6′-tetrahydro-β,β-carotene-3, 3′-diol = syn,anti-violaxanthin; 6) were prepared by epoxidation of zeaxanthin diacetate (1) with monoperphthalic acid. Violaxanthins 5 and 6 were submitted to thermal isomerization and I₂-catalyzed photoisomerization. The structure of the main products, i.e., (9Z)-5, (13Z)-5, (9Z)-6, (9′Z)-6, (13Z)-6, and (13′Z)-6, was determined by their UV/VIS, CD, ¹H-NMR, ¹³C-NMR, and mass spectra.

Full text of DOI:10.1002/hlca.200490001

Helvetica Chimica Acta Vol. 87 (2004)
11
Preparation and (E/Z)-Isomerization of the Diastereoisomers of
Violaxanthin
by Pe¬ter Molna¬ra), Jo¬zsef Delia), Ferenc Zsilab), Andrea Steckc), Hanspeter Pfander*c), and Gyula To¬th*a)
a
¬
¬
) Department of Biochemistry and Medical Chemistry, University of Pecs, Medical School, Szigeti ut 12,
¬
P.O. Box 99, H-7601 Pecs
b) Department of Molecular Pharmacology, Institute of Chemistry, Chemical Research Center, P.O. Box 17,
H-1525 Budapest
c) Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern
Violaxanthin A (ˆ(all-E,3S,5S,6R,3'S,5'S,6'R)-5,6 :5',6'-diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol
ˆ syn,syn-violaxanthin; 5) and violaxanthin B (ˆ(all-E,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-diepoxy-5,6,5',6'-tetrahy-
dro-b,b-carotene-3,3'-diol ˆ syn,anti-violaxanthin; 6) were prepared by epoxidation of zeaxanthin diacetate (1)
with monoperphthalic acid. Violaxanthins 5 and 6 were submitted to thermal isomerization and I2-catalyzed
photoisomerization. The structure of the main products, i.e., (9Z)-5, (13Z)-5, (9Z)-6, (9'Z)-6, (13Z)-6, and
(13'Z)-6, was determined by their UV/VIS, CD, 1H-NMR, 13C-NMR, and mass spectra.
Introduction.
According to the classical experiments of Karrer×s school [1],
epoxidation of zeaxanthin diacetate (ˆ(all-E,3R,3'R)-b,b-carotene-3,3'-diol diacetate;
1) with monoperphthalic acid yielded antheraxanthin A (ˆ(all-E,3S,5R,6S,3'R)-5,6-
epoxy-5,6-dihydro-b,b-carotene-3,3'-diol ˆ anti-antheraxanthin ˆ natural antheraxan-
thin; 2), antheraxanthin B (ˆ(all-E,3S,5S,6R,3'R)-5,6-epoxy-5,6-dihydro-b,b-caro-
tene-3,3'-diol ˆ syn-antheraxanthin ˆ semisynthetic antheraxanthin; 3), violaxanthin
(ˆ(all-E,3S,5R,6S,3'S,5'R,6'S)-5,6 :5',6'-diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-
diol ˆ anti,anti-violaxanthin ˆ natural violaxanthin; 4), violaxanthin
A
(ˆ(all-
E,3S,5S,6R,3'S,5'S,6'R)-5,6 :5',6'-diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ˆ
syn,syn-violaxanthin ˆ semisynthetic violaxanthin; 5), and violaxanthin B (ˆ(all-
E,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ˆ
syn,anti-violaxanthin ˆ mesoviolaxanthin ˆ semisynthetic violaxanthin; 6) (Scheme)1).
In our experiment and in agreement with the results of Karrer×s school, the naturally
occurring antheraxanthin (2) and violaxanthin (4) were formed only as minor products.
In other epoxidation experiments with different monoperoxy acids the exclusive
formation of semisynthetic violaxanthins 5 and 6 was observed [2][3]. During our
systematic research concerning the (E/Z)-isomerization of the polyene chain, the
thermal isomerization and the I2-catalyzed photoisomerization [4] of the natural
anti,anti-violaxanthin (4) was investigated earlier. The (9Z)-, (13Z)-, and (15Z)-
isomers of 4 were prepared by stereomutation and were isolated from the blossoms of
Viola tricolor [5 7]. As part of a systematic investigation of the isolation, preparation,
identification, and stereomutation of carotenoids [6 9], we now report the preparation
1
)
syn/anti refers to the position of the OH and epoxy group with respect to the mean ring plane of the b-end
group.

12
Helvetica Chimica Acta Vol. 87 (2004)
Scheme
and structure elucidation of the isomerization products of semisynthetic violaxanthins 5
and 6. Our previous experiments concerning the thermal isomerization and I2-catalyzed
photoisomerization of semisynthetic violaxanthins 5 and 6 on a semimicro scale
confirmed that the end groups with different configuration influenced the composition
of the stereoisomer equilibrium mixtures only slightly [8][9].
Results. Epoxidation. The epoxidation of 800 mg of zeaxanthin diacetate (1) with
monoperphthalic acid (Et2O, room temperature, 40 h) gave, in agreement with the
classical results of Karrer×s school [1], two diastereoisomeric antheraxanthins 2 and 3
and three diastereoisomeric violaxanthins 4 6 (for HPLC separation, see Fig. 1). The

Helvetica Chimica Acta Vol. 87 (2004)
13
Fig. 1. HPLC Separation of semisynthetic diastereoisomeric violaxanthins 4
6
separation of carotenoid esters was carried out by preparative column chromatography
(CC; see Exper. Part). After saponification, the corresponding carotenoids were
crystallized from benzene/hexane 1:5 to give 15 mg of 2, 60 mg of 3, 10 mg of 4, 80 mg
of 5, and 75 mg of 6.
Thermal Isomerization. The thermal isomerization of 5 and 6 (benzene, 808, 2 h)
gave, in agreement with the pioneering studies of Zechmeister [4] and with our recent
results [6 9], (13Z)-5 and (13Z)- and (13'Z)-6, respectively, as main products. In
addition, two (di-Z)-isomers of 6 were observed in small quantities. The composition of
the equilibrium mixtures of 5 and 6 was determined by HPLC (Fig. 2,a and Fig. 3,a)
and CC [6][8][9]. The preparative separation was achieved by CC (see Exper. Part),
and the fractions of the corresponding isomers were crystallized from benzene/hexane
1:5 to give 18 mg of (13Z)-5, 7 mg of (13Z)-6, and 5 mg of (13'Z)-6, respectively.
Fig. 2. HPLC Separation of the equilibrium mixtures obtained a) by thermal isomerization and b) by I2-catalyzed
photoisomerization of syn,syn-violaxanthin (5)
Iodine-Catalyzed Photoisomerization. In agreement with previous results for other
carotenoids [4 12], the I2-catalyzed photoisomerization of 5 (benzene, room temper-
ature, 40 min in diffuse daylight, resulting in a thermodynamic equilibrium [12]) gave

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Helvetica Chimica Acta Vol. 87 (2004)

Helvetica Chimica Acta Vol. 87 (2004)
15
Fig. 3. HPLC Separation of the equilibrium mixtures obtained by a) thermal isomerization and b) by I2-catalyzed
photoisomerization of syn,anti-violaxantin (6)
(9Z)-5 and (13Z)-5. In addition, the thermodynamic equilibrium mixture contained
two (di-Z)-isomers in minor amounts (Fig. 2,b).
In accordance with the configurational asymmetry of semisynthetic syn,anti-
violaxanthin (6), I2-catalyzed photoisomerization of 6 gave four (mono-Z)-isomers,
namely (9Z)-, (9'Z)-, (13Z)-, and (13'Z)-6. Furthermore, two additional (di-Z)-isomers
were observed in the stereoisomer equilibrium mixture (Fig. 3,b), which were not
identified.
The (Z)-isomers were separated on a preparative scale by CC (see Exper. Part) and
then crystallized from benzene/hexane 1:5 to give 10 mg of (9Z)-5, 3 mg of (13Z)-5,
6 mg of (9Z)-6, 5 mg of (9'Z)-6, 2 mg of (13Z)-6, and 2 mg of (13'Z)-6.
Spectroscopic Characterization. A tentative determination of the position of the
CˆC bond with (Z)-configuration within the polyene chains was performed by the
UV/VIS spectra of the isomerization products and their auroxanthin derivatives. The
UV/VIS spectra of all geometrical isomers of semisynthetic violaxanthins, i.e., of 5,
(9Z)-5, (13Z)-5, 6, (9Z)-6, (9'Z)-6, (13Z)-6, and (13'Z)-6, with the main absorption
maximum between 453 445 nm (in benzene) are in agreement with a nonaene
chromophore. The characteristic UV/VIS data (lmax, %Acis-peak/Amax and lmax after
furanoid oxide reaction) are presented in Table 1. The occurrence of a week cis-peak
and the small hypsochromic shift of lmax (Dlmax ˆ 5 6 nm) is characteristic for (9Z)-5,
Table 1. UV/VIS Spectroscopic Data of (all-E)- and Main (mono-Z)-Isomers of Semisynthetic Diastereoiso-
meric Violaxanthins (5, (9Z)-5, (13Z)-5, 6, (9Z)-6, (9'Z)-6, (13Z)-6 and (13'Z)-6)
lmax in C6H6 [nm]
lmax after acid treatment in C6H6 [nm]
%Acis-peak/Amax
5
(9Z)-5
(13Z)-5
6
483, 452, 427
437, 410, 387
< 5
477, 447, 423, 337, 323
475, 444, 419, 337, 323
483, 453, 427,
435, 408, 385, 301, 289
434, 407, 384, 300, 288
437, 410, 388
8.73
51.55
< 5
(9Z)-6
(9'Z)-6
(13Z)-6
(13'Z)-6
478, 448, 424, 337, 323
477, 447, 423, 337, 323
475, 445, 420, 337, 323
475, 444, 419, 337, 323
435, 408, 386, 302, 290
436, 408, 385, 301, 289
434, 407, 384, 301, 289
433, 406, 383, 300, 288
8.60
8.76
51.02
50.76

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Helvetica Chimica Acta Vol. 87 (2004)
(9Z)-6, and (9'Z)-6 (Table 1, Figs. 4 and 5) and is in agreement with geometrical
isomers containing a (Z)-double bond in a peripheral position. (13Z)-5, (13Z)-6, and
(13'Z)-6 exhibit a strong cis-peak at ca. 337 and 323 nm and considerable Dlmax-values
(Dlmax ˆ 7 8 nm; Table 1, Figs. 4 and 6), characteristic for isomers with a (Z)-double
bond in a more central position of the polyene chain [9][10].
The configuration of the CˆC bonds of the polyene chain in 5, (9Z)-5, (13Z)-5, 6,
(9Z)-6, (9'Z)-6, (13Z)-6, and (13'Z)-6 was determined by NMR spectroscopy, applying
1
1
1H-NMR, H,1H-COSY, H,1H-T-ROESY, 13C-NMR, DEPT-135, and inverse HMQC
techniques [13][14]. The data given in the Exper. Part and especially the characteristic
values of 1H- and 13C-NMR isomerization shifts (Dd ˆ d(Z) À d(all-E) (Tables 2 and 3)
were identical with the corresponding data reported in [14] and confirmed the structure
of the investigated (mono-Z)-isomers.
The CD spectrum of (all-E)-syn,syn-violaxanthin (5) is a mirror image of the CD
spectrum of (all-E)-anti,anti-violaxanthin (4) [15]. The bands in the CD spectra of
(9Z)- and (13Z)-syn,syn-violaxanthin at room temperature and at À1808 are opposite
in sign to the corresponding (all-E)-syn,syn-violaxanthin (5) (Fig. 7). These data are in
agreement with the data reported in [16 19]. The CD spectrum of (all-E)-syn,anti-
violaxanthin (ˆ−mesoviolaxanthin×; 6) is little meaningful and has signs exclusively
with negative De values in the wavelength range of 200 550 nm (Fig. 8). It was
established earlier that −mesoviolaxanthin× (6) has no ORD spectrum [2]. The (9Z)-,
(9'Z)-, (13Z)-, and (13'Z)-isomers of syn,anti-violaxanthin show weak CD bands
(Fig. 8, note that the temperature is À1808!). The spectra of (9Z)-6 and (9'Z)-6 are
opposite in sign in the wavelength range of 200 350 nm (mirror image) but they are
identical in sign in the range of 350 550 nm (Fig. 8).
The mass spectra of all isomers showed the corresponding molecular ion peak at m/z
‡
‡
‡
ˆ 600 and in addition signals at 582 [M À H2O] , 564 [M À 2 H2O] , 520 [M À 80] , 508
‡
[M À toluene] , 352, 287, 274, 247 234, 221, 181, 91, 43, and 18 [2][20].
Discussion. The thermal isomerization of (all-E)-syn,syn-violaxanthin (5) and of
(all-E)-syn,anti-violaxanthin (6) gave mainly the (13Z)-isomer of 5 and the (13Z)- and
(13'Z)-isomers of 6, respectively. Therefore, the thermal isomerization is a suitable
method for the preparation of (13Z)-5, (13Z)-6, and (13'Z)-6. The I2-catalyzed
photoisomerization of 5 and 6 resulted in complex mixtures of (Z)-isomers, which were
demanding to separate. As main products, the (mono-Z)-isomers, namely the (9Z)-5,
(13Z)-5, (9Z)-6, (9'Z)-6, (13Z)-6, and (13'Z)-6 were prepared and characterized.
The isomer composition of the equilibrium mixtures obtained from 5 and 6 were
nearly identical (Figs. 2 and 3), showing that configurational differences have no
appreciable influence on the process of stereomutation. In addition, each individual
(mono-Z)-isomer was reconverted into the respective parent (all-E)-isomer by I2-
catalysis and into the corresponding auroxanthin epimers by acid treatment [2][4 9].
The structure of the main products of (E/Z)-isomerization of 5 and 6 correspond to
those of the products of the (E/Z)-isomerization of other carotenoids containing the
5,6-epoxy-5,6-dihydro-3-hydroxy-b-end group with the same chromophore [5 10].
Also the compositions of the stereoisomer equilibrium mixtures were very similar for
all compounds with the 5,6-epoxy-5,6-dihydro-3-hydroxy-b-end group, independent of
the structure of the second end group (b-, 3-hydroxy-b-, 3,6-epoxy-5,6-dihydro-b-, 5,6-

Helvetica Chimica Acta Vol. 87 (2004)
17
Fig. 4. UV/VIS Spectra of (all-E)-syn,syn-violaxanthin (5; ¥¥¥¥ ), (9Z)-syn,syn-violaxanthin ((9Z)-5; –) and
(13Z)-syn,syn-violaxanthin ((13Z)-5; ) in benzene
Fig. 5. UV/VIS Spectra of (all-E)-syn,anti-violaxanthin (6; ¥¥¥¥ ), (9Z)-syn,anti-violaxanthin ((9Z)-6; –), and
(9'Z)-syn,anti-violaxanthin ((9'Z)-6; ) in benzene

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Helvetica Chimica Acta Vol. 87 (2004)
Fig. 6. UV/VIS Spectra of (all-E)-syn,anti-violaxanthin (6; ¥¥¥¥ ), (13Z)-syn,anti-violaxanthin ((13Z)-6; –), and
(13'Z)-syn,anti-violaxanthin ((13'Z)-6; ) in benzene
Table 2. 1H- and 13C-NMR Isomerization Shifts (Dd ˆ d(Z) À d(all-E)) of syn,syn-Violaxanthin Isomers (9Z)-5
and (13Z)-5
1H-NMR isomerization shifts
13C-NMR isomerization shifts
H-atom
Dd(1H) ˆ d(9Z) À
d(all-E)
H-atom
Dd(1H) ˆ d(13Z) À
d(all-E)
C-atom
Dd(13C) ˆ
d(9Z) À d(all-E)
measured
[14]
measured
[14]
measured
[14]
HÀC(8)
‡ 0.54
‡ 0.54
À 0.09
‡ 0.10
À 0.06
HÀC(10) ‡ 0.04
HÀC(12) ‡ 0.53
HÀC(14) À 0.14
HÀC(15) ‡ 0.20
HÀC(15') À 0.08
‡ 0.05 C(7)
‡ 0.52 C(8)
À 0.13 C(9)
‡ 0.16 C(10)
À 0.08 C(11)
C(12)
‡ 2.11
À 7.90
À 1.48
À 1.47
À 1.02
À 0.74
‡ 8.04
‡ 1.6
À 7.8
À 1.4
À 1.5
À 1.2
À 0.7
‡ 8.0
HÀC(10) À 1.12
HÀC(11) ‡ 0.15
HÀC(12) À 0.08
Me(19)
a) The Dd(13C) ˆ d(13Z) À d(all-E) values could not be measured because the amount of the sample was
insufficient.
dihydro-3,5,6-trihydroxy-b- and e-end group) investigated before [5 10][21 24]. The
rate of the (E/Z)-isomerization of 5 and 6 was in the same order as the rate of (E/Z)-
isomerization of 4 and of other carotenoids containing a 5,6-dihydro-b end group
[6][8][9]. The equilibrium was reached by thermal isomerization within 120 min and
by I2-catalyzed photoisomerization within 40 min [6 10].

Table 3. 1H- and 13C-NMR Isomerization Shifts (Dd ˆ d(Z) À d(all-E)) of syn,anti-Violaxanthin Isomers (9Z)-6, (9'Z)-6, (13Z)-6, and (13'Z)-6
1H isomerization shifts
H-atom Dd(1H) ˆ d(9Z) À d(all-E) H-atom
Dd(1H) ˆ d(9'Z) À d(all-E) H-atom
Dd(1H) ˆ d(13Z) À d(all-E) H-atom
Dd(1H) ˆ d(13'Z) À d(all-E)
measured
[14]
measured
[14]
measured
[14]
measured
[14]
HÀC(8) ‡ 0.54
‡ 0.54
À 0.09
‡ 0.10
À 0.06
HÀC(8') ‡ 0.54
‡ 0.54
À 0.09
‡ 0.10
À 0.06
HÀC(10) ‡ 0.05
‡ 0.05
‡ 0.52
À 0.13
‡ 0.16
À 0.08
HÀC(10') ‡ 0.05
‡ 0.05
‡ 0.52
À 0.13
‡ 0.16
À 0.08
HÀC(10) À 0.11
HÀC(11) ‡ 0.14
HÀC(12) À 0.09
HÀC(10') À 0.1
HÀC(11') ‡ 0.15
HÀC(12') À 0.07
HÀC(12') ‡ 0.54
HÀC(14) À 0.13
HÀC(15) ‡ 0.13
HÀC(15') À 0.08
HÀC(12') ‡ 0.52
HÀC(14') À 0.16
HÀC(15') ‡ 0.16
HÀC(15) À 0.08
13C-NMR isomerization shifts
C-atom Dd(13C) ˆ d(9Z) À d(all-E)
C-atom Dd(13C) ˆ d(9'Z) À d(all-E)
C-atom Dd(13C) ˆ d(13Z) À d(all-E)
C-atom Dd(13C) ˆ d(13'Z) À d(all-E)
measured
[14]
measured
[14]
measureda)
[14]
measureda)
[14]
C(7)
C(8)
C(9)
C(10) À 1.53
C(11) À 1.10
C(12) À 0.82
C(19) ‡ 8.00
‡ 2.01
À 7.95
À 1.51
‡ 1.6
À 7.8
À 1.4
À 1.5
À 1.2
À 0.7
‡ 8.0
C(7')
C(8')
C(9')
C(10') À 1.50
C(11') À 1.09
C(12') À 0.79
C(19') ‡ 8.00
‡ 2.09
À 8.07
À 1.53
‡ 1.6
À 7.8
À 1.4
À 1.5
À 1.2
À 0.7
‡ 8.0
C(11) ‡ 0.9
‡ 1.3
À 8.0
À 1.2
À 1.6
À 1.3
À 0.9
‡ 8.0
C(12) À 8.3
C(13) not available
C(14) À 1.8
C(15) À 1.9
C(15') À 1.2
C(20) ‡ 8.0
C(20') ‡ 8.0
‡ 8.0
a) These data were gained on the basis of the HMQC experiments.

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Helvetica Chimica Acta Vol. 87 (2004)
It was established earlier that carotenoids with 5,6-epoxy-5,6-dihydro-b-end groups
have strongly conservative CD spectra. Also, it is known that CD spectra of carotenoids
in which the chromophoric portions belong to the C2 point group conform to the so-
called C2-rule: if the overall conjugated system acquires right-handed helicity (i.e.,
dihedral angles around bonds C(6)ÀC(7) and C(6')ÀC(7') are negative), then
transitions of symmetry A lead to negative Cotton effects (CE), and transitions of
symmetry B lead to positive CE [25][26]. Epoxy groups and the polyene backbone of
violaxanthin form a common chromophore with C2 symmetry due to the conjugative
interaction between them. Accordingly, the C(5)ÀC(6) and C(5')ÀC(6') bonds can be
treated as CˆC bonds, whose spatial positions relative to the polyene chain will
determine the overall helicity of the molecule and, consequently, the signs of the
individual CD bands. The structure of (all-E)-syn,syn-violaxanthin (5) shows that its
C(5)ÀC(6) and C(5')ÀC(6') bonds are behind the plane of the paper so the molecules
has right-handed helicity. In agreement with this configuration and the C2 rule, negative
(transition symmetry A) and positive (transition symmetry B) Cotton bands appears in
the CD spectrum centered at 328.5 and 267 nm (Fig. 7). Due to the restricted
Fig. 7. CD Spectra of (all-E)-, (9Z)-, and (13Z)-syn,syn-violaxanthins (5, (9Z)-5, and (13Z)-5, resp.) in Et2O/
isopentane/EtOH 5 :5 :2 at room temperature and at À1808

Helvetica Chimica Acta Vol. 87 (2004)
21
conformational motions, CD spectra obtained at À1808 show more resolved vibrational
fine structure, and the band maxima are shifted toward lower wavelengths. Since in the
geometrical isomers of syn,syn-violaxanthin (5) helicity of the overall conjugated
system is changed from right- to left-handed, the (9Z)- and (13Z)-isomers give mirror-
image CD spectra (Fig. 7).
The CD curve of (all-E)-syn,anti-violaxanthin (ˆ−mesoviolaxanthin×; 6) exhibits
much weaker bands, even at À1808 (Fig. 8), due to the opposite chiral influences of the
epoxy groups. The same holds for the (Z)-isomers of syn,anti-violaxanthin. The
presence of the (3S) and (3'S) stereogenic centers is responsible for the weak −residual×
optical activity.
This study, on the part of Hungarian authors, was supported by a grant from OTKA T 032882 and OTKA T
¬
037441 (Hungarian National Research Foundation). We thank Mrs. M. Steiler, Mrs. A. Bognar, and Mr. N. Gˆtz
for skillful assistance, Dr. F. M¸ller and Mrs. J. Kohler (F. Hoffmann-La Roche Ltd., Basel) for recording the CD
spectra, and Dr. A. Giger and S. Werner for recording the mass spectra. The financial support of the Swiss group
by F. Hoffmann-La Roche Ltd., Basel, and the Swiss National Science Foundation is gratefully acknowledged.
Fig. 8. CD Spectra of (all-E)-, (9Z)-, (9'Z)-, (13Z)- and (13'Z)-syn,anti-violaxanthins (6, (9Z)-6, (9'Z)-6,
(13Z)-6, and (13'Z)-6), resp. in Et2O/isopentane/EtOH 5 :5 :2 at À1808

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Helvetica Chimica Acta Vol. 87 (2004)
Experimental Part
1. General. See [27]. EPA ˆ Et2O/isopentane/EtOH 5 :2 :2. Asterisks (*,**) mean that assignments may be
interchanged.
2. HPLC. See [27].
3. Diastereoisomeric Semisynthetic Violaxanthins 5 and 6. A soln. of 800 mg of (all-E)-zeaxanthin diacetate
(1; m.p. 1248; purity (HPLC) > 95%) in 1600 ml of Et2O (free of H2O and peroxides) was epoxidized with 0.65n
monoperphthalic acid (24 ml) at r.t. during 40 h under N2 in the dark [1][2] (reaction monitoring by UV/VIS
spectra and paper chromatography (Whatman AH-81, benzene)). After the usual workup [28], the mixture was
separated by CC (30 columns, 6 Â 30 cm; with CaCO3, hexane). Picture after development: 5 mm yellow
(unidentified); 10 mm of intermediate zone; 15 mm yellow (Zone 1; diacetate of 5); 3 mm of intermediate
zone; 20 mm yellow (Zone 2; diacetate of 4 and 6); 3 mm of intermediate zone; 8 mm ochre (Zone 3; diacetate
of 2); 5 mm of intermediate zone; 16 mm of ochre (Zone 4; diacetate of 3); 6 mm of intermediate zone; 10 mm
ochre (Zone 5; 1). The fraction of Zone 2 was submitted to repeated CC (10 columns, 6 Â 30 cm; CaCO3, 0.5%
acetone/hexane). Picture after development: 3 mm pale yellow (unidentified); 10 mm of intermediate zone;
6 mm yellow (Zone 21; diacetate of 4); 3 mm of intermediate zone; 25 mm yellow (Zone 22; diacetate of 6).
After saponification (30% KOH/MeOH in heterogeneous phase) and the usual workup [28], the carotenoids
were crystallized from benzene/hexane 1:5 to give 30 mg of 1 (m.p. 193 1948), 15 mg of 2 (m.p. 170 1718),
60 mg of 3 (m.p. 113 1158), 10 mg of 4 (m.p. 196 1988), 80 mg of 5, and 75 mg of 6.
4. Violaxanthin A (ˆ(all-E,3S,5S,6R,3'S,5'S,6'R)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-
diol ˆ syn,syn-Violaxanthin; 5). M.p. 190 1928. Purity (HPLC): >95%. UV/VIS (benzene): Table 1, Fig. 4.
CD (EPA, r.t.): 206.5 (‡4.6), 219.5 (0.0), 231.0 (À 9.9), 242.0 (0.0), 267.0 (‡23.7), 288.5 (0.0), 328.5 (À 5.6);
Fig. 7. CD (EPA, À1808): 207.0 (‡27.0), 227.5 (‡0.1), 232.0 (À 9.5), 236.0 (À0.3), 269.5 (‡42.9), 284.5 (‡ 9.7),
332.0 (‡0.4), 335.0 (À4.7), 338.0 (‡0.3), 342.5 (‡4.0), 482.0 (‡1.3); Fig. 7. 1H-NMR (400 MHz, CDCl3): 1.01
(s, Me(16)); 1.01 (s, Me(16')); 1.17 (s, Me(17)); 1.17 (s, Me(17')); 1.19 (s, Me(18)); 1.19 (s, Me(18')); 1.35 (dd,
Jgem ˆ 12.4, J(2eq,3) ˆ 2.8, HeqÀC(2)); 1.35 (dd, Jgem ˆ 12.4, J(2'eq,3') ˆ 2.8, HeqÀC(2')); ca. 1.61 (dd, Jgem ˆ 12.4,
J(2ax,3) ꢀ 4, HaxÀC(2)); ca. 1.61 (dd, Jgem ˆ 12.4, J(2'ax,3') ꢀ 4, HaxÀC(2')); 1.89 (dd, Jgem ˆ 14.8, J(4ax,3) ˆ 8.5,
HaxÀC(4)); 1.89 (dd, Jgem ˆ 14.8, J(4'ax,3') ˆ 8.5, HaxÀC(4')); 1.92 (s, Me(19)); 1.92 (s, Me(19')); 1.96 (s, Me(20));
1.96 (s, Me(20')); 2.20 (dd, Jgem ˆ 14.8, J(4eq,3) ˆ 6.3, HeqÀC(4)); 2.20 (dd, Jgem ˆ 14.8, J(4'eq,3') ˆ 6.3,
HeqÀC(4')); 3.87 (m, HÀC(3)); 3.87 (m, HÀC(3')); 5.82 (d, J(7,8) ˆ 15.6, HÀC(7)), 5.82 (d, J(7',8') ˆ 15.6,
HÀC(7')); 6.20 (d, J(10,11) ˆ 11.4, HÀC(10)), 6.20 (d, J(10',11') ˆ 11.4, HÀC(10')); 6.26 (HÀC(14)); 6.26
(HÀC(14')); 6.30 (d, J(8,7) ˆ 15.6, HÀC(8)); 6.30 (d, J(8',7') ˆ 15.6, HÀC(8')); 6.37 (d, J(12,11) ˆ 14.9,
HÀC(12)); 6.37 (d, J(12',11') ˆ 14.9, HÀC(12')); 6.60 (dd, J(11,10) ˆ 11.4, J(11,12) ˆ 14.9, HÀC(11)); 6.60 (dd,
J(11',10') ˆ 11.4, J(11',12') ˆ 14.9, HÀC(11')); 6.64 (HÀC(15)); 6.64 (HÀC(15')). 13C-NMR (100 MHz, CDCl3):
12.74 (C(20,20')); 12.91 (C(19,19')); 21.18 (C(18,18')); 26.03 (C(17,17')), 26.81 (C(16,16')); 35.03 (C(1,1')); 39.17
(C(4,4')); 43.74 (C(2,2')); 64.04 (C(3,3')); 65.23 (C(5,5')); 71.27 (C(6,6')); 122.45 (C(7,7')); 124.01 (C(11,11'));
130.16 (C(15,15')); 132.38 (C(10,10')); 132.87 (C(14,14'); 134.10 (C(9,9')); 136.39 (C(13,13')); 138.07 (C(8,8'));
‡
‡
‡
‡
138.24 (C(12,12')). EI-MS: 600 (58, M ), 582 (3, [M À H2O] ), 520 (12, [M À 80] ), 508 (24, [M À toluene] ),
440 (13), 352 (12), 287 (9), 274 (24), 247 (14), 234 (23), 221 (100), 208 (19), 181 (38), 91 (100), 43 (21, 18 (19).
5. Violaxanthin B (ˆ(all-E,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-
diol ˆ syn,anti-Violaxanthin ˆ −Mesoviolaxanthin×; 6). M.p. 203 2058. Purity (HPLC): 95%. UV/VIS (benzene)
Table 1, Figs. 5 and 6. CD (EPA, r.t.): 222.0 (0.0), 230.5 (‡0.7), 254.0 (0.0), 266.5 (À1.2), 279.5 (0.0), 440.5
(À0.4), 476 (À0.7). CD (EPA, À1808): 335.0 (À1.2), 425.5 (À0.7), 430.0 (À0.8), 455.0 (À1.5), 459.5 (À1.3),
488.0 (À1.9); Fig. 8. 1H-NMR (400 MHz, CDCl3): 0.98 (s, Me(16')); 1.01 (s, Me(17)); 1.154 (s, Me(16)); 1.147 (s,
Me(17')); 1.19 (s, Me(18)); 1.19 (s, Me(18')); 1.25 (dd, Jgem ꢀ 13, J(2'ax,3') ꢀ 11, HaxÀC(2')), 1.25 (br.,
OHÀC(3')); 1.35 (ddd, Jgem ˆ 12.53, J(2eq,3) ˆ 3.81, J(2eq,4eq) ˆ 1.15, HeqÀC(2)); 1.57 (br., OHÀC(3)); 1.60
(m, Jgem ˆ 12.53, HaxÀC(2)); 1.63 (m, Jgem ꢀ 13, J(2'eq,4'eq) ˆ 1.64, HeqÀC(2')); 1.63 (dd, Jgem ˆ 14.08,
J(4'ax,3') ˆ 8.54, HaxÀC(4')); 1.89 (dd, Jgem ˆ 14.80, J(4ax,3) ˆ 8.43, HaxÀC(4)); 1.92 (s, Me(19)); 1.92 (s,
Me(19')); 1.96 (s, Me(20)); 1.96 (s, Me(20')); 2.20 (ddd, Jgem ˆ 14.80, J(4eq,3) ˆ 5.57, J(4eq,2eq) ˆ 1.15,
HeqÀC(4)); 2.39 (ddd, Jgem ˆ 14.08, J(4'eq,3') ˆ 5.19, J(4'eq,2'eq) ˆ 1.64, HeqÀC(4')); 3.89 (m, HÀC(3)); 3.91
(m, HÀC(3')); 5.82 (d, J(7,8) ˆ 15.66, HÀC(7)); 5.88 (d, J(7',8') ˆ 15.67, HÀC(7')); 6.19 (d, J(10,11) ˆ 10.71,
HÀC(10)); 6.19 (d, J(10',11') ˆ 11.71, HÀC(10')); 6.27 (HÀC(14)); 6.27 (HÀC(14')); 6.29 (d, J(8',7') ˆ 15.67,
HÀC(8')); 6.30 (d, J(8,7) ˆ 15.66, HÀC(8)); 6.37 (d, J(12,11) ˆ 14.75, HÀC(12)); 6.37 (d, J(12',11') ˆ 14.75,
HÀC(12')); 6.61 (dd, J(11,10) ˆ 11.71, J(11,12) ˆ 14.75, HÀC(11)); 6.61 (dd, J(11',10') ˆ 11.71, J(11',12') ˆ 14.75,
HÀC(11')); 6.64 (HÀC(15)); 6.64 (HÀC(15')). 13C-NMR (100 MHz, CDCl3): 12.79 (C(20,20')); 12.95 (C(19))*;
12.98 (C(19'))*; 20.04 (C(18')); 21.25 (C(18)); 25.00 (C(16')); 26.09 (C(16)); 26.88 (C(17)); 29.57 (C17')); 35.12

Helvetica Chimica Acta Vol. 87 (2004)
23
(C(1)); 35.36 (C(1')); 39.34 (C(4)); 41.08 (C(4')); 43.92 (C(2)); 47.22 (C(2')); 64.12 (C(3')); 64.34 (C(3)); 65.24
(C(5')); 66.86 (C(5)); 70.34 (C(6')); 71.31 (C(6)); 122.54 (C(7)); 123.87 (C(7')); 124.67 (C(11)); 124.74 (C(11'));
130.19 (C(15')); 130.27 (C(15)); 132.26 (C(10')); 132.45 (C(10)); 132.84 (C(14')); 132.94 (C(14)); 134.15 (C(9));
134.33 (C(9')); 136.40 (C(13))**; 136.48 (C(13'))**; 137.44 (C(8')); 138.21 (C(8)); 138.21 (C(12')); 138.33
‡
‡
‡
‡
(C(12')). EI-MS: 600 (37, M ), 582 (10, [M À H2O] ), 520 (14, [M À 80] ), 508 (8, [M À toluene] ), 440 (12),
352 (16), 299 (20), 287 (27), 274 (26), 247 (25), 234 (32), 221 (100), 181 (51), 165 (35), 145 (31), 119 (34), 91
(26), 43 (23), 18 (11).
6. Thermal Isomerization. A soln. of 80 mg of violaxanthin A (ˆ(all-E)-syn,syn-violaxanthin; 5) in 800 ml
of benzene and a soln. of 75 mg of violaxanthin B (ˆ(all-E)-syn,anti-violaxanthin; 6) in 750 ml of benzene were
refluxed during 2 h under N2 in the dark [4][6][9][23], and after the usual workup [28], the equilibrium
mixtures were submitted to CC.
7. I2-Catalyzed Photoisomerization. A soln of 50 mg of violaxanthin A (ˆ(all-E)-syn,syn-violaxanthin; 5) in
500 ml of benzene or a soln. of 45 mg of violaxanthin B (ˆ(all-E)-syn,anti-violaxanthin; 6) in 450 ml of benzene
was isomerized under N2 in scattered daylight in the presence of 1 mg of I2 (ca. 2% rel. to the carotenoid)
[4][6][8][23] (monitoring by UV/VIS [6][8]). When the thermodynamic equilibrium was reached after ca.
40 min, the mixture was washed free of I2 with 5% Na2S2O3 soln. and, after the usual workup [28], submitted to
CC.
8. Separation of (E/Z)-Isomers. The reaction mixtures were separated by CC (6 Â 30 cm columns, CaCO3).
The separation of the thermal isomerization mixture from 5 (4 columns, benzene, 1 2% acetone/benzene)
resulted in the following picture after development: 4 mm pale yellow (unidentified), 3 mm of intermediate
zone, 20 mm yellow (Zone 1; (13Z)-5), 4 mm of intermediate zone, 3 mm pale yellow (Zone 2; (9Z)-5), 50 mm
of intermediate zone, 8 mm pale yellow (unidentified; probably (di-Z)-isomer of 5), 20 mm of intermediate
zone, 40 mm yellow (Zone 3; 5). Picture after development for I2-catalyzed photoisomerization of 5 (3
columns; benzene, 1 3% acetone/benzene): 3 mm pale yellow (unidentified), 4 mm of intermediate zone,
10 mm yellow (Zone 1; (13Z)-5), 4 mm of intermediate zone, 20 mm yellow (Zone 2; (9Z)-5), 4 mm of
intermediate zone, 4 mm pale yellow (Zone 3; (di-Z)-5), 20 mm of intermediate zone, 12 mm pale yellow
(Zone 4; (di-Z)-5), 15 mm of intermediate zone, 15 mm pale yellow (Zone 5; (di-Z)-5), 20 mm of intermediate
zone, 10 mm pale yellow (Zone 6; (di-Z)-5), 20 mm of intermediate zone, 12 mm pale yellow (Zone 7; (di-Z)-
5), 25 mm of intermediate zone, 40 mm yellow (Zone 8; 5).
The separation of the thermal isomerization mixture of 6 (4 columns, benzene and 0.2 4% acetone/
benzene) resulted in the following picture after development: 2 mm pale yellow (unidentified), 20 mm yellow
(Zone 1; (13Z)- and (13'Z)-6), 25 mm of intermediate zone, 8 mm pale yellow (unidentified), 30 mm of
intermediate zone, 40 mm yellow (Zone 2; 6). Picture after development for the mixture obtained by I2-
catalyzed photoisomerization of 6 (3 columns, benzene and 3 6% acetone/benzene): 2 mm pale yellow
(unidentified), 10 mm of intermediate zone, 10 mm yellow (Zone 1; (13Z)- and (13'Z)-6), 10 mm of
intermediate zone, 3 mm pale yellow (unidentified), 15 mm of intermediate zone, 30 mm yellow (Zone 2;
(9'Z)-6), 4 mm of intermediate zone, 25 mm yellow (Zone 3; (9Z)-6), 10 mm of intermediate zone, four pale
yellow zones (10 12 mm one after the other) with intermediate zones (Zone 4; mixture of (di-Z)-isomers of 6),
10 mm of intermediate zone, 50 mm yellow (Zone 5; 6). Zone 1 ((13Z)- and (13'Z)-6; obtained by CC of
thermal- and I2-catalyzed photoisomerization equilibrium mixtures of 6) was submitted to repeated CC (4
columns, 4%, 8%, and 12% acetone in benzene/hexane 1:1). Picture after development: 80 mm of intermediate
zone, 25 mm yellow (Zone 11; (13'Z)-6), 2 mm of intermediate zone, 20 mm yellow (Zone 12; (13Z)-6), 10 mm
of intermediate zone, 10 mm pale yellow (unidentified).
After the usual workup [28], the corresponding fractions were combined, and the carotenoid isomers were
crystallized from benzene/hexane 1:5 to give 10 mg of (9Z)-5, 21 mg of (13Z)-5, 6 mg of (9Z)-6, 5 mg of (9'Z)-6,
9 mg of (13Z)-6, and 7 mg of (13'Z)-6.
9. (9Z,3S,5S,6R,3'S,5'S6'R)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol, ( ˆ (9Z)-syn,syn-
Violaxanthin; (9Z)-5). M.p. 111 1138. Purity (HPLC): 97%. UV/VIS (benzene) see Table 1, Fig. 4. CD
(EPA, r.t.): 201.5 (‡0.4), 209.0 (À11.3), 215.5 (‡0.4), 232.0 (‡ 38.5), 250.0 (0.0), 268.0 (À16.2), 281.0 (0.0),
315.0 (‡ 9.4), 320.0 (‡ 7.2), 327.0 (‡12.1), 376.0 (0.0), 414.4 (À4.2), 422.5 (À 3.1), 437.5 (À6.6), 453.5 (À 3.7),
465.5 (À 7.6 ) ; Fig. 7. CD (EPA, À1808): 209.5 (À 37.7), 218.5 (0.0), 233.5 (‡68.7), 247.5 (0.0), 270.0 (À 37.4),
289.0 (0.0), 307.0 (‡ 5.6), 311.5 (‡ 3.7), 318.5 (‡12.9), 327.5 (‡4.0), 333.5 (‡29.0), 421.0 (À6.8), 434.5 (À2.4),
445.0 (À11.1), 463.5 (À1.6), 475.0 (À10.0); Fig. 7. 1H-NMR (400 MHz, CDCl3): 1.01 (s, Me(16')), 1.03 (s,
Me(16)); 1.15 (s, Me(17')); 1.17 (s, Me(17)); 1.19 (s, Me(18')); 1.21 (s, Me(18)); 1.37 (m, Jgem ꢀ 12.5, HeqÀC(2'));
ca. 1.37 (m, Jgem ꢀ 12.5, HeqÀC(2)); 1.61 (dd, Jgem ꢀ 12.5, J(2×ax,3') ˆ 4.2, HaxÀC(2')); 1.62 (dd, Jgem ꢀ 12.5,
J(2ax,3) ˆ 4.2, HaxÀC(2)); 1.88 (dd, Jgem ˆ 14.8, J(4ax,3) ˆ 8.7, HaxÀC(4)); 1.89 (dd, Jgem ꢀ 14.8, J(4'ax,3') ˆ 8.5,

24
Helvetica Chimica Acta Vol. 87 (2004)
HaxÀC(4')); 1.92 (s, Me(19')); 1.93 (s, Me(19)); 1.956 (s, Me(20')); 1.964 (s, Me(20)); 2.20 (dd, Jgem ꢀ 14.8,
J(4'eq,3') ꢀ 6, HeqÀC(4')); 2.22 (dd, Jgem ˆ 14.8, J(4eq,3) ꢀ 6, HeqÀC(4)); 3.87 (m, HÀC(3')); 3.88 (m, HÀC(3));
5.81 (d, J(7',8') ˆ 15.6, HÀC(7')); 5.87 (d, J(7,8) ˆ 15.5, HÀC(7)); 6.08 (d, J(10,11) ˆ 11.5, HÀC(10)); 6.20 (d,
J(10',11')); 6.23 (HÀC(14)); 6.26 (HÀC(14')); 6.29 (d, J(12,11) ˆ 14.9, HÀC(12)); 6.29 (d, J(8',7') ˆ 15.6,
HÀC(8')); 6.37 (d, J(12',11') ˆ 14.9, HÀC(12')); 6.59 (dd, J(11',10') ˆ 11.6, J(11',12') ˆ 14.9, HÀC(11')); 6.61
(HÀC(15)); 6.64 (HÀC(15')); 6.75 (dd, J(11,10) ˆ 11.5, J(11,12) ˆ 14.9, HÀC(11)); 6.84 (d, J(8,7) ˆ 15.5)).
13C-NMR (100 MHz, CDCl3): 12.78 (C(20')); 12.95 (C(19')); 12.99 (C(20)); 20.95 (C(19)); 21.22 (C(18)); 21.24
(C(18')); 26.02 (C(17)); 26.07 (C(17')); 26.85 (C(16')); 26.94 (C(16)); 35.01 (C(1)); 35.08 (C(1')); 39.23 (C(4,4'));
43.79 (C(2,2')); 64.01 (C(3)); 64.08 (C(3')); 65.27 (C(5')); 65.29 (C(5)); 71.31 (C(6')); 71.44 (C(6)); 122.45
(C(7')); 123.59 (C(11)); 124.56 (C(7), C(11')); 129.97 (C(15)); 130.32 (C(15')); 130.91 (C(10)); 132.44 (C(10'));
132.62 (C(9),C(14)); 132.95 (C(14')); 134.08 (C(9')); 136.26 (C(13')); 136.59 (C(13)); 137.50 (C(12)); 138.13
‡
‡
‡
(C(8')); 138.32 (C(12')). EI-MS: 600 (65, M ), 582 (4, [M À H2O] ), 564 (2, [M À 2 H2O] ), 520 (33, [M À
‡
‡
80] ), 508 (19 [M À toluene] ), 440 (33), 352 (28), 299 (28), 287 (39), 274 (53), 247 (23), 234 (34), 221 (100),
208 (23), 181 (41), 165 (30), 119 (24), 105 (17), 91 (30), 43 (17), 18 (10).
10. (13Z,3S,5S,6R,3'S,5'S,6'R)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ( ˆ (13Z)-
syn,syn-Violaxanthin; (13Z)-5). M.p. 121 1238. Purity (HPLC): 94%. UV/VIS (benzene) Table 1, Fig. 4. CD
(EPA, r.t): 209.5 (‡ 5.6), 233 (‡42.1), 257.5 (‡0.3), 269.0 (À14.3), 277.5 (‡0.2), 316.0 (‡ 32.3), 321.5 (‡25.7),
329.0 (‡43.9), 382.5 (0.0), 409.5 (À6.2), 419.5 (À 5.2), 434.5 (À11.5), 449.5 (À 5.4), 462.5 (À11.2); Fig. 7. CD
(EPA, À1808): 204.5 (À0.1), 210.0 (À15.2), 214.0 (‡0.2), 234.5 (‡ 53.6), 258.0 (‡0.3), 271.5 (À15.5), 274.5
(À0.6), 276.5 (‡ 5.3), 279.5 (‡2.37), 284.0 (‡10.5), 301.0 (‡ 5.6), 308.0 (‡ 9.7), 314.5 (‡ 3.0), 321.0 (‡19.1),
327.5 (‡11.4), 336.5 (‡ 55.1), 380.5 (‡0.1), 397.5 (À 5.8), 407.0 (À4.7), 420.0 (À16.7), 432.5 (À2.3), 445.0
(À23.6), 453.5 (‡0.9), 460.5 (‡13.2), 469.5 (‡0.3), 476.5 (À18.7), 483.0 (À0.5), 489.5 (‡24.4); Fig. 7. 1H-NMR
(400 MHz, CDCl3): 1.013 (s, Me(17')); 1.018 (s, Me(17)); 1.155 (s, Me(16')); 1.161 (s, Me(16)); 1.190 (s, Me(18'));
1.196 (s, Me(18)); ca. 1.36 (ddd, Jgem ˆ 12.5, J(2eq,3) ˆ 3.6, J(2eq,4eq) ˆ 1.8, HeqÀC(2), HeqÀC(2')); 1.611 (dd,
Jgem ˆ 12.5, J(2'ax,3') ˆ 11.3, HaxÀC(2')); 1.614 (dd, Jgem ˆ 12.5, J(2ax,3) ˆ 11.3, HaxÀC(2)); 1.891 (dd, Jgem ˆ14.9,
J(4'ax,3') ˆ 8.6, HaxÀC(4')); 1.896 (dd, Jgem ˆ 15.0 J(4ax,3) ˆ 8.7, HaxÀC(4)); 1.92 (s, Me(19')); 1.93 (s, Me(19));
1.95 (s, Me(20')); 1.98 (s, Me(20)); 2.20 (m, HeqÀC(4), HeqÀC(4')), 3.88 (m, HÀC(3), HÀC(3')); 5.82 (d,
J(7',8') ˆ 15.5, HÀC(7')); 5.84 (d, J(7,8) ˆ 15.6, HÀC(7)); 6.12 (d, J(12,11) ˆ 12.1, HÀC(14)); 6.20 (d,
J(10',11') ˆ 11.5, HÀC(10')); 6.24 (d, J(10,11) ˆ 11.3, HÀC(10)); 6.26 (d, J(14',15') ˆ 12.9, HÀC(14')); 6.30 (d,
J(8',7') ˆ 15.5, HÀC(8')); 6.32 (d, J(8,7) ˆ 15.6, HÀC(8)); 6.38 (d, J(12',11') ˆ 15.3, HÀC(12')); 6.56 (dd,
J(15',14') ˆ 12.9, J(15',15) ˆ 14.0, HÀC(15')); 6.60 (dd, J(11',10') ˆ 11.5, J(11',12') ˆ 15.3, HÀC(11')); 6.61 (dd,
J(11,10) ˆ 11.3, J(11,12) ˆ 15.1, HÀC(11)); 6.80 (dd, J(15,14) ˆ 12.1, J(15,15') ˆ 14.0, HÀC(15)); 6.90 (d,
J(12,11) ˆ 15.1). 13C-NMR: no data due to the small sample amount and instability of (13Z)-5 in CDCl3. EI-MS:
‡
‡
‡
‡
600 (44, M ), 582 (2, [M À H2O] ), 520 (20, [M À 80] ), 508 (11, [M À toluene] ), 440 (27), 352 (17), 299 (20),
287 (24), 274 (48), 247 (18), 234 (25), 221 (100), 203 (23), 181 (34), 165 (25), 119 (22), 105 (15), 91 (45), 43
(15), 18 (25).
11. (9Z,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ( ˆ (9Z)-syn,anti-
Violaxanthin; (9Z)-6). M.p. 94 968. Purity (HPLC): 96%. UV/VIS (benzene): Table 1, Fig. 5. CD (EPA, r.t.):
208.0 (‡6.4), 224.0 (0.0), 232.0 (À2.3), 241.0 (0.0), 274.0 (À0.3), 279.0 (À0.1), 284.0 (‡0.7), 312.0 (0.0), 328.0
(À0.7), 335.0 (0.0), 436.0 (‡1.5), 452.0 (‡1.2), 465.0 (‡1.7). CD (EPA, À1808): 209.0 (‡12.3), 225.0 (0.0),
233.0 (À4.3), 243.0 (0.0), 262.0 (0.00), 269.0 (‡0.4), 275.0 (À0.7), 290.0 (‡1.1), 311.0 (‡0.9), 319.0 (À0.3),
327.0 (‡0.5), 333.0 (À1.4), 341.0 (‡0.6), 401.0 (‡0.8), 421.0 (‡1.5), 436.0 (‡1.1), 447.0 (‡2.4), 464.0 (‡0.5),
477.0 (‡ 3.0); Fig. 8. 1H-NMR (400 MHz, CDCl3): 0.976 (s, Me(16')); 1.030 (s, Me(17)); 1.147 (s, Me(17')); 1.170
(s, Me(16)); 1.186 (s, Me(18')); 1.211 (s, Me(18)); 1.23 (dd, HaxÀC(2')); 1.33 (ddd, HeqÀC(2)); 1.62 (dd,
HaxÀC(2)); 1.63 (ddd, HeqÀC(2')); 1.89 (dd, J(4ax,4eq) ˆ 14.8, J(4ax,3) ˆ 8.8, HaxÀC(4)); 1.925 (s, Me(19'));
1.929 (s, Me(19)); 1.958 (s, Me(20')); 1.967 (s, Me(20)); 2.22 (m, J(4eq,4ax) ˆ 14.8, J(4eq,3) ˆ 7.1, HeqÀC(4));
2.38 (m, J(4'eq,4'ax) ˆ 13.4, J(4'eq,3') ˆ 4.2, HeqÀC(4)); 3.89 (m, HÀC(3)); 3.90 (m, HÀC(3')); 5.87 (d, J(7,8) ˆ
15.6, HÀC(7)); 5.88 (d, J(7',8') ˆ 15,6, HÀC(7')); 6.08 (d, J(10,11) ˆ 11.3, HÀC(10)); 6.18 (d, J(10',11') ꢀ 11,
HÀC(10')); 6.24 (m, HÀC(14)); 6.26 (m, HÀC(14')); 6.28 (d, J(12,11) ˆ 15.0, HÀC(12)); 6.29 (d, J(8',7') ˆ 15.6,
HÀC(8')); 6.37 (d, J(12',11') ˆ 14.7, HÀC(12')); 6.60 (dd, J(11',10') ꢀ 11, J(11',12') ˆ 14.7, HÀC(11')); 6.62 (m,
HÀC(15), HÀC(15')); 6.75 (dd, J(11,10) ˆ 11.3, J(11,12) ˆ 15.0, HÀC(11)); 6.84 (d, J(8,7) ˆ 15.6, HÀC(8)).
13C-NMR (100 MHz, CDCl3): 12.79 (C(20)); 12.99 (C(18'), C(19'), C(20')); 20.96 (C(19)); 21.22 (C(18)); 24.89
(C(16')); 26.03 (C(16)); 26.95 (C(17)); 29.58 (C(17')); 35.01 (C(1)); 35.35 (C(1')); 39.23 (C(4)); 41.00 (C(4'));
43.79 (C2)); 47.19 (C(2')); 64.03 (C(3)); 64.30 (C(3')), 65.29 (C(5')); 66.96 (C(5)); 70.30 (C(6')); 71.45 (C(6));
123.57 (C(11)); 123.81 (C(7')); 124.55 (C(7)); 124.61 (C(11')); 129.99 (C(15)); 130.19 (C(15')); 130.26 (C(8));
130.92 (C(10)); 132.26 (C(10')); 132.62 (C(14)); 132.64 (C(9)); 132.88 (C(14')); 134.24 (C(9')); 136.29 (C(13));

Helvetica Chimica Acta Vol. 87 (2004)
25
‡
‡
136.55 (C(13')); 137.34 (C(8')); 137.51 (C(12)); 138.21 (C(12')). EI-MS: 600 (11, M ), 520 (23, [M À 80] ), 440
(0.12), 287 (25), 274 (17), 247 (5), 234 (12), 221 (100), 181 (28), 165 (21), 119 (30), 105 (29), 91 (64), 56 (28), 43
(42), 18 (17).
12. (9'Z,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ( ˆ (9'Z)-syn,an-
ti-Violaxanthin; (9'Z)-6). M.p. 93 958. Purity (HPLC): 94%. UV/VIS (benzene): Table 1, Fig. 5. CD (EPA,
r.t.): 210.0 (À 7.1), 223.0 (‡0.1), 232.0 (‡2.1), 239.0 (‡0.6), 271.0 (‡2.4), 282.0 (‡1.9), 313.0 (‡1.6), 321.0
(‡1.0), 327.0 (‡1.4), 343.0 (‡0.1), 441.0 (‡1.8), 454.0 (‡1.5), 463.0 (‡2.0). CD (EPA, À1808): 210.0 (À11.4),
221.0 (‡0.2), 233.0 (‡6.7), 275.0 (‡1.8), 284.0 (‡2.2), 298.0 (‡1.53), 307.0 (‡2.0), 312.0 (‡1.6), 318.0 (‡2.8),
328.0 (‡1.2), 334.0 (‡ 3.85), 429.0 (‡1.0), 453.0 (‡1.7), 465.0 (‡0.6), 477.0 (‡2.9); Fig. 8. 1H-NMR (400 MHz,
CDCl3): 1.005 (s, Me(16')); 1.009 (s, Me(17)); 1.152 (s, Me(16)), 1.161 (s, Me(17')); 1.186 (s, Me(18)); 1.242 (s,
Me(18')), 1.25 (dd, J(2'ax,2'eq) ꢀ 13, J(2'ax,3') ꢀ 11, HaxÀC(2')); 1.35 (ddd, J(2eq,2ax) ˆ 12.4, J(2eq,3) ˆ 4.1,
J(2eq,4eq) ˆ 1.0, HeqÀC(2')); 1.60 (m, J(2ax,2eq) ˆ 12.4, HaxÀC(2)); 1.63 (ddd, HeqÀC(2')); 1.64 (dd,
J(4'ax,4'eq) ˆ 14.3, J(4'ax,3') ˆ 8.8, HaxÀC(4')); 1.89 (dd, J(4ax,4eq) ˆ 14.9, J(4ax,3) ˆ 8.5, HaxÀC(4)); 1.921
(s, Me(19)); 1.929 (s, Me(19')); 1.954 (s, Me(20)); 1.960 (s, Me(20')); 2.20 (ddd, J(4eq,4ax) ˆ 14.9, J(4eq,3) ˆ 6.6,
J(4eq,2eq) ˆ 1.0, HeqÀC(4)); 2.40 (ddd, J(4'eq,4ax) ˆ 14.3, J(4'eq,3') ˆ 5.1, J(4'eq,2'eq) ˆ 1.7, HeqÀC(4')); 3.87
(m, HÀC(3)); 3.92 (m, HÀC(3')); 5.81 (d, J(7,8) ˆ 15.6, HÀC(7)); 5.93 (d, J(7',8') ˆ 15.3, HÀC(7')); 6.07 (d,
J(10',11') ˆ 11.7, HÀC(10')); 6.20 (d, J(10,11) ˆ 11.8, HÀC(10)); 6.23 (m, HÀC(14')); 6.27 (m, HÀC(14)); 6.28
(d, J(8,7) ˆ 15.6, HÀC(8)); 6.30 (d, J(12',11') ˆ 14.8, HÀC(12')); 6.37 (d, J(12,11) ˆ 15.0, HÀC(12)); 6.59 (dd,
J(11,10) ˆ 11.8, J(11,12) ˆ 15.0, HÀC(11)); 6.61 (m, HÀC(15')); 6.64 (m, HÀC(15)); 6.76 (dd, J(11',10') ˆ 11.7,
J(11',12') ˆ 14.8, HÀC(11')); 8.83 (d, J(8',7') ˆ 15.3, HÀC(8')). 13C-NMR (100 MHz, CDCl3): 12.78 (C(20'));
12.95 (C(20)); 13.00 (C(19)); 19.97 (C(18')); 21.00 (C(19')); 21.24 (C(18)); 24.93 (C(16')); 26.07 (C(16)); 26.85
(C(17)); 29.56 (C(17')); 35.08 (C(1)); 35.29 (C(1')); 39.22 (C(4)); 40.98 (C(4')); 43.78 (C(2)); 47.20 (C(2')); 64.09
(C(3)); 64.29 (C(3')); 65.27 (C(5')); 67.06 (C(5)); 70.48 (C(6')); 71.31 (C(6)); 122.44 (C(7)); 123.65 (C(11'));
124.54 (C(11)); 125.96 (C(7')); 129.37 (C(8')); 129.93 (C(15')); 130.33 (C(15)); 130.76 (C(10')); 132.44 (C(10));
132.56 (C(14')); 132..80 (C(9')); 132.96 (C(14)); 134.06 (C(9)); 136.23 (C(13')); 136.63 (C(13)); 137.42 (C(12'));
‡
138.13 (C(8)); 138.33 (C(12)). EI-MS: 600 (35, M ), 274 (11), 247 (1), 234 (5), 221 (54), 181 (17), 157 (18), 123
(31), 109 (14), 91 (52), 83 (19), 69 (28), 56 (45), 43 (100), 18 (55).
13. (13Z,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ( ˆ (13Z)-syn,an-
ti-Violaxanthin; (13Z)-6). M.p. 104 1058. Purity (CC): 94%. UV/VIS (benzene) Table 1, Fig. 6. CD (EPA,
r.t.): 207.5 (‡2.5), 238.5 (‡0.2), 284.5 (‡1.25), 294.0 (‡1.5), 306.0 (‡0.9), 312.5 (‡1.1). CD (EPA, À1808):
207.0 (‡2.8), 240.0 (À0.1), 257.5 (‡0.2), 279.0 (‡1.3), 281.0 (‡1.2), 287.5 (‡1.7), 292.0 (‡1.5), 297.5 (‡2.2),
311.0 (‡1.1), 317.0 (‡2.05), 340.0 (0.0), 362.0 (À1.0), 370.0 (À0.7), 381.5 (À1.9), 392.0 (À0.8), 404.5 (À2.5),
416.0 (À0.6), 430.5 (À1.9), 443.0 (À0.4), 455.0 (À1.1), 491.0 (À0.6); Fig. 8. 1H-NMR (400 MHz, CDCl3): 0.99
(s, Me(16')); 1.03 (s, Me(17)); 1.158 (s, Me(17')); 1.170 (s, Me(16)); 1.20 (s, Me(18), Me(18')); 1.24 (dd,
HaxÀC(2')); 1.35 (ddd, HeqÀC(2)); 1.60 (dd, HaxÀC(2)); 1.63 (ddd, HeqÀC(2')); 1.63 (dd, HaxÀC(4')); 1.89 (dd,
HaxÀC(4)); 1.932 (s, Me(19')); 1.940 (s, Me(19)); 1.961 (s, Me(20')); 1.989 (s, Me(20)); 2.21 (m, J(4eq,4ax) ꢀ 15,
J(4eq,3) ꢀ 6, 2.39 (ddd, HeqÀC(4)); 3.88 (m, HÀC(3)); 3.91 (m, HÀC(3')); 5.85 (d, J(7,8) ꢀ 15, 5, HÀC(7));
5.89 (d, J(7',8') ˆ 15.6, HÀC(7')); 6.14 (d, J(14,15) ˆ 11.2, HÀC(14)); 6.20 (d, J(10',11') ꢀ 11, HÀC(10')); 6.24
(d, overlapped, HÀC(10)); 6.25 (d, J(14',15') ˆ 11.0, HÀC(14')), 6.30 (d, J(8,7) ꢀ 15, HÀC(8)); 6.33 (d,
J(8',7') ˆ 15.6, HÀC(8')); 6.37 (d, J(12',11') ˆ 15.2, HÀC(12')); 6.56 (m, J(15',14') ˆ 11.0, HÀC(15')); 6.60 (dd,
overlapped, J(11,12) ˆ 15.0, HÀC(11)); 6.60 (dd, J(11',10') ꢀ 11, J(11',12') ˆ 15.2, HÀC(11')); 6.77 (m,
J(15,14) ˆ 11.2, HÀC(15)); 6.91 (d, J(12,11) ˆ 15.0, HÀC(12)). 13C-NMR via HSQC/HMBC (100 MHz,
CDCl3): 12.3 (C(20')); 12.6 (C(19), C(19')); 19.8 (C(18')); 20.2 (C(20)); 21.0 (C(18)); 24.7 (C(16')); 25.8 (C(16));
26.6 (C(17)); 29.3 (C(17')); 38.8 (C(4)); 43.5 (C(2)); 46.8 (C2')); 63.9 (C(3), C(3')); 122.7 (C(7)); 123.7 (C(7'));
124.3 (C(11')); 125.6 (C(11)); 128.4 (C(15)); 129.0 (C(15')); 129.2 (C(12)); 131.1 (C(14)); 132.0 (10')); 132.4
(C(14')); 132.5 (C(10)); 137.2 (C(8)); 138.0 (C(8')); 138.2 (C(12')); some signals could not be extracted due to
‡
‡
‡
the small sample amount. EI-MS: 600 (35, M ), 582 (6, [M À H2O] ), 520 (18, [M À 80] ), 508 (8, [M À
‡
toluene] ), 440 (13), 352 (20), 299 (22), 287 (25), 274 (18), 247 (11), 234 (12), 221 (42), 181 (42), 135 (12), 125
(15), 119 (16), 109 (14), 95 (26), 91 (31), 83 (17), 69 (23), 56 (35), 43 (100), 18 (26).
14. (13'Z,3S,5S,6R,3'S,5'R,6'S)-5,6 :5',6'-Diepoxy-5,6,5',6'-tetrahydro-b,b-carotene-3,3'-diol ( ˆ (13'Z)-syn,an-
ti-Violaxanthin; (13'Z)-6). M.p. 110 1118. Purity: 95% (CC). UV/VIS (benzene): Table 1, Fig. 6. CD (EPA,
r.t.): 202 (‡2.0), 208 (‡ 3.4), 230.0 (0.0), 233.0 (À0.2), 236 (À0.1), 260.0 (À1.4), 268.0 (À1.9), 279.0 (0.0), 290.0
(‡1.0), 295.0 (‡0.8), 300.0 (‡1.0), 308 (‡0.7), 314.0 (‡1.05), 322.0 (‡0.3), 328.0 (‡0.6), 338.0 (0.0), 343.0
(À0.2), 350.0 (0.0), 437.0 (‡1.8), 456 (‡1.4), 465.0 (‡1.7). CD (EPA, À1808): 202.0 (‡ 5.8), 207.0 (‡ 7.5), 231.0
(‡2.05), 234.0 (‡2.35), 244.0 (‡0.1), 260.0 (À2.3), 265.0 (À2.2), 271.0 (À 3.8), 280.0 (‡0.1), 291.0 (‡2.1),
298.0 (‡1.8), 305.0 (‡2.6), 312.0 (‡1.8), 318.0 (‡ 3.5), 327.0 (‡1.7), 336.0 (‡ 3.5), 351.0 (0.0), 378.0 (‡0.2),

26
Helvetica Chimica Acta Vol. 87 (2004)
388.0 (0.0), 402 (‡0.6), 410.0 (‡0.5), 427.0 (‡1.3), 436.0 (‡0.9), 452.0 (‡2.1), 464.0 (‡0.4), 475.0 (‡2.6);
Fig. 8. 1H-NMR (400 MHz, CDCl3): 0.98 (s, Me(16')); 1.01 (s, Me(17)); 1.15 (s, Me(16), Me(17)); 1.189 (s,
Me(18)); 1.193 (s, Me(18')); 1.25 (dd, HaxÀC(2')), 1.36 (ddd, J(2eq,2ax) ꢀ 12, J(2eq,3) ꢀ 4, J(2eq,4eq) ꢀ 1,
HeqÀC(2)); 1.61 (m, J(2ax,2eq) ꢀ 12, HaxÀC(2)); 1.63 (ddd, HeqÀC(2')), 1.63 (dd, HaxÀC(4')); 1.89 (dd,
J(4ax,4eq) ˆ 14.9, J(4ax,3) ˆ 6.4, J(4ax,2eq) ꢀ 1, HaxÀC(4)); 1.92 (s, Me(19)); 1.93 (s, Me(19')); 1.95 (s, Me(20));
1.98 (s, Me(20')); 2.20 (ddd, J(4eq,4ax) ˆ 14.9, J(4eq,3) ˆ 6.4, J(4eq,2eq) ꢀ 1, HeqÀC(4)); 2.39 (ddd,
J(4'eq,4'ax) ˆ 14.2, J(4'eq,3') ˆ 4.8, J(4'eq,2'eq) ˆ 1.4, HeqÀC(4')); 3.88 (m, HÀC(3)); 3.92 (m, HÀC(3'));
5.81 (d, J(7,8) ˆ 15.6, HÀC(7)); 5.90 (d, J(7',8') ˆ 15.5, HÀC(7')); 6.11 (d, J(14',15') ˆ 11.6, HÀC(14')); 6.20 (d,
J(10,11) ˆ 11.4, HÀC(10)); 6.24 (d, J(10',11') ˆ 11.7, HÀC(10')), 6.27 (d, overlapped, HÀC(14)); 6.30 (d,
J(8,7) ˆ 15.6, HÀC(8)); 6.31 (d, J(8',7') ˆ 15.5, HÀC(8')); 6.38 (d, J(12,11) ˆ 15.0, HÀC(12)); 6.56 (m,
J(15,15') ˆ 14.4, HÀC(15)); 6.60 (dd, J(11,10) ˆ 11.4, J(11,12) ˆ 15.0, HÀC(11)); 6.61 (dd, J(11',10') ˆ 11.7,
J(11',12') ˆ 14.9, HÀC(11')); 6.80 (dd, J(15',14') ˆ 11.6, J(15',15) ˆ 14.4, HÀC(15')); 6.89 (d, J(12',11') ˆ 14.9,
HÀC(12')). 13C-NMR via HSQC/HMBC (100 MHz, CDCl3): 12.6 (C(19')); 12.9 (C(19)); 12.9 (C(20)); 19.7
(C(18)); 20.3 (C(20')); 20.9 (C(18')); 25.8 (C(16), C(16')); 26.6 (C(17)); 29.4 (C(17')); 38.9 (C(4)); 41.3 (C(4'));
43.5 (C(2)); 47.9 (C(2')); 64.3 (C(3), C(3')); 122.3 (C(7)); 124.1 (C(7')); 124.2 (C(11)); 130.4 (C(14)); 132.2
(C(10)); 132.8 (C(10')); ca. 137.2 (C(8')); ca. 137,4 (C(8)); some signals could not be extracted due to the small
‡
‡
‡
‡
sample amount. EI-MS: 600 (30, M ), 582 (6, [M À H2O] ), 520 (10, [M À 80] ), 508 (5, [M À toluene] ), 287
(17), 274 (49), 247 (8), 234 (12), 221 (100), 208 (16), 181 (42), 125 (18), 119 (19), 91 (91), 56 (26), 43 (44), 18
(31).
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Received July 15, 2003