578

J. Nat. Prod. 2001, 64, 578-581

Structures of Five New Carotenoids from the Oyster Crassostrea gigas
Takashi Maoka,†,§ Keiji Hashimoto,† Naoshige Akimoto,‡ and Yasuhiro Fujiwara*,†Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan, and Graduate School of Pharmaceutical Sciences,
Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
Received October 5, 2000

Five new minor carotenoids, 1-5, were isolated from the oyster Crassostrea gigas. The structure of 1
was determined to be (3S,5R,6R,6′S)-3,5,6′-trihydroxy-3′-oxo-6,7-didehydro-5,6-dihydro-10,11,20-trinorβ,-caroten-19′,11′-olide 3-acetate by detailed analyses of NMR and CD data. The structures of the othercarotenoids, 2-5, were also determined in a similar manner. In the FAB-MS/MS of 2-4, having the5-hydroxy-3,6-epoxy-5,6-dihydro-β-carotene moiety, the characteristic product ions resulting from thesequential cleavage of C-C bonds in the polyene chain were observed.
In the course of the studies on new carotenoids in natural
products, we reported the isolation and structure elucidation of the retro-carotenoid anhydroeschscholtzxanthin,1athe di-Z-carotenoid cucumariaxanthins,1b the purple carotenoid rhodobacterioxanthin,1c the C69 carotenoids pittosporumxanthins,1d and carotenoids possessing the uniqueend group of the crassostreaxanthins.2 In the previous
paper, we reported the isolation and structure elucidationof crassostreaxanthins A and B from the oyster Crassostrea
gigas Thunberg (Ostreidae).2
Recently, we have isolated five new minor carotenoids,
1-5, from the same species.
This paper deals with the isolation and structural
elucidation of these five carotenoids and with the observed
characteristic ions in FAB-MS/MS of 2, 3, and 4.
Results and Discussion
Acetone extraction of the oyster C. gigas (10 kg), followed
by treatment with Et2O-n-hexane (1:1), gave a crude
mixture of carotenoids. Repeated separations of the crude
mixture of carotenoids by silica gel column chromatography
and by HPLC on silica gel and on ODS furnished the new
carotenoids 1 (0.5 mg), 2 (1 mg), 3 (0.5 mg), 4 (1 mg), and
5 (0.5 mg).
Carotenoid 1 was obtained as a red, amorphous solid
exhibiting a molecular ion peak (HREIMS) at m/z 628.3395
corresponding to C39H48O7. The UV-vis spectrum of 1 in
Et2O showed an absorption maximum at 457 nm. The 13C
NMR and HSQC spectra of 1 in CDCl3 confirmed thepresence of 39 carbons and 46 carbon-bonded protons. In
the 1H and 13C NMR spectra of 1 the noticeable signals
due to three carbonyl carbons and allene groups wereobserved at δC 170.4, 168.7, and 197.7 and at δC 202.7 andδH 6.06. The NMR and the UV-vis data suggested that 1
was an analogue of peridinin.3,4 Thus, the NMR data of 1
were compared with those of peridinin.4
The 1H and 13C NMR signal assignments of 1 in CDCl3
were made by 1H-1H COSY, HSQC, HMBC, and NOESY
experiments. The 1H assigned data of 1 are given in Table
1, together with those of the other carotenoids (2-5). The
13C data of 1 and 4 are presented in the Experimental
Section. The 1H and 13C data of 1 were almost identicalwith those of peridinin4 except for the signals of the end* To whom correspondence should be addressed. Tel: +81-75-595-4637.
Fax: +81-75-595-4766. E-mail: fujiwara@mb.kyoto-phu.ac.jp.
† Kyoto Pharmaceutical University.
‡ Kyoto University.
§ Present address: Sun Biorex Co., LTD., Shimogamo-Morimoto-cho 15,
Sakyo-ku, Kyoto 606-0805, Japan.

10.1021/np000476w CCC: $20.00

group (C1′ to C6′). The connections of the unassigned end
group in 1 were determined by the HMBC experiment. The
HMBC data are summarized in Figure 1. The 1H and 13C
signals for the unassigned end group of 1 showed crosspeaks in the HMBC spectrum between the following
proton-carbon pairs: H16′, H17′-C1′, C2′, C6′, H2′-C3′,
H18′-C5′, C6′, H4′-C18′, and H7′-C6′. On the basis of
the HMBC connectivities, the partial structure of the end
group (C1′ to C6′) was deduced (Figure 1). Thus, the wholechemical structure of 1 was determined. The structure of
1 was also supported by the data of 1H-1H COSY.
The stereochemistry of 1 was confirmed by NOESY and
CD data. The NOESY spectrum showed NOE cross-peaks
between H17′ and H7′ and between H16′ and hydroxy© 2001 American Chemical Society and American Society of Pharmacognosy
Published on Web 04/19/2001

New Carotenoids from the Oyster Crassostrea

Journal of Natural Products, 2001, Vol. 64, No. 5 579

Table 1. 1H NMR (500 MHz) Data of Carotenoids 1-5 in CDCl3a,b1H no.

H-2R
H-2β
H-3
H-4R
H-4β
H-7
H-8
H-10
H-11
H-12
H-13
H-14
H-15
H-16
H-17
H-18
H-19
H-20
CH3CO
H-2′R
H-2′β
H-3′
H-4′R
H-4′β
H-5′
H-7′
H-8′
H-10′
H-11′
H-12′
H-14′
H-15′
H-16′
H-17′
H-18′
H-19′
H-20′
OH-8′

1
δ mult. (J, Hz)2δ mult. (J, Hz)3δ mult. (J, Hz)4δ mult. (J, Hz)5δ mult. (J, Hz)

2.00 ddd (12, 4, 2)
1.41 dd (12, 12)5.37 m2.29 ddd (13, 4, 2)
1.51 dd (13, 13)

1.61 d (11.5)
1.84 ddd (11.5, 6, 2)
4.39 t (6)1.67 d (12)2.06 ddd (12, 6, 2)
5.75 d (16)6.38 d (16)
6.21 d (11.5)
6.66 dd (15. 11.5)
6.37 d (15)1.61 d (11.5)
1.84 dm(11.5)
4.39 t (6)1.67 d (12)2.06 ddd (12, 6, 2)
5.75 d (16)6.38 d (16)
6.20 d (11.5)
6.63 dd (15, 11.5)
6.36 d (15)1.61 d (11.5)
1.84 ddd(11.5, 6, 2)
4.39 t (6)1.67 d (12)2.06 ddd (12, 6, 2)
5.75 d (16)6.38 d (16)
6.21 d (11.5)
6.64 dd (15, 11.5)
6.37 d (15)1.95 ddd (12, 4, 2)
1.34 dd (12, 12)4.32 m2.26 ddd (13, 4, 2)
1.41 dd (13, 13)
6.04 s6.12 d (11.5)
6.59 dd (15, 11.5)
6.35 d (15)

6.27 d (11.5)
6.74 dd (14.5, 11.5)
1.44 s
0.89 s1.22 s
1.96 s1.99 s6.26 d (10)6.63 m1.44 s
0.89 s1.22 s
1.96 s
1.97 s6.28 d (11)6.72dd (14.5, 11.5)
1.44 s
0.89 s1.22 s
1.96 s1.98 s6.26 d (11.5)
6.72dd(14.5,11.5)
1.34 s1.07 s1.35 s1.81 s1.98 s2.52 dd (15, 5)
2.69 dd (15, 7)
4.21 m1.31 ddd (12, 11, 10)
2.17 ddd (12, 7, 5)
2.32 ddq (11, 7, 7)
2.86 d (13.5)
2.93 d (13.5)

1.84 ddd(12.5,4,2)
1.46 dd (12.5, 12.5)
4.00 m2.43 ddd (18, 5.5, 2)
2.09 dd (18, 9)

2.19 dd (13.5, 8)
1.72 dd (13.5, 4.5)
4.53 m
2.88 dd (14.5, 8.5)
1.55 dd (14.5, 2.5)

2.19 dd (13.5, 8)
1.72 dd (13.5, 4.5)
4.53 m
2.88 dd (14.5, 8.5)
1.55 dd (14.5, 2.5)

5.86 s

5.86 s7.26 d (11)6.59 dd (15, 11)6.68 d (15)
6.42 d (11.5)
6.66 dd (14.5, 11.5)
2.14 s1.10 s0.99 d (7)1.93 s1.99 s6.46 d (11)6.51 dd (14.5, 11.5)
6.36 d (14.5)
6.27 d (10)6.63 m1.15 s1.20 s1.92 s
1.95 s2.01 s7.24 d (11)6.60 dd (15, 11)
6.66 d (15)6.38 d (11.5)
6.63 dd (14.5, 11.5)
0.85 s1.19 s1.35 s1.99 s1.99s
16.30 s7.24 d (11)6.59 dd (15, 11)6.65 d (15)
6.37 d (11.5)
6.63 dd (14.5, 11.5)
0.85 s1.19 s1.35 s1.98 s1.99 s
16.30 s6.06 s6.12 d (11.5)
6.62 dd (14.5, 11.5)
6.36 dd (14.5, 11.5)
6.53 dd (14.5, 11.5)
1.39 s1.07 s1.35 s1.80 s2.04 s2.55 d (18)2.30 d (18)
5.95 br s
6.97 d (15)
6.55 d (15)7.10 s5.72 s6.48 d (11.5)
6.61 dd (14.5, 11.5)
1.11 s1.04 s1.91 d (1.2)
2.23 sa 1H chemical shifts are reported downfield from internal TMS ()0.00). b 1H NMR signals were assigned by gmq-COSY and NOESY
experiments and by comparison with those of related compounds (ref 4).

Figure 1. Structure and HMBC correlations for carotenoid 1.

proton(s). The other observed NOE cross-peaks between
the remaining protons in 1 were almost identical with thosein peridinin.4 Thus, the relative stereochemistry of 1 was
assigned as shown in Figure 1. The CD spectrum of 1
showed characteristic Cotton effects similar to those of
amarouciaxanthin A,5 which possesses 3S,5R,6R,6′S chiralities. Consequently, the absolute structure of 1 was determined to be (3S,5R,6R,6′S)-3,5,6′-trihydroxy-3′-oxo-6,7didehydro-5,6-dihydro-10,11,20-trinor-β,-caroten-19′,11′olide 3-acetate.
Carotenoids 2 and 3 were obtained as orange amorphoussolids. The UV-vis spectra of 2 and 3 in Et2O showedabsorption maxima at 443 and 468 and at 446 and 476 nm,
respectively. The molecular formulas of 2 and 3 were
determined as C40H56O5 and C40H54O3 by HREIMS, respectively.
As can be seen from Table 1, the 1H chemical shifts andthe spin-couplings of H2 to H20 in 2 and 3 were almost

identical with those in cycloviolaxanthin.6 That is, the data
indicated the presence of a cycloviolaxanthin partial structure in 2 and 3. The NMR signals of the remaining unassigned protons (H2′ to H20′) of 2 and 3 were similar to thoseof a partial structure in crassostreaxanthin A2 and alloxanthin,4 respectively. Consequently, the structures of 2 and3, each of which was made up of the corresponding partial
structures in cycloviolaxanthin and crassostreaxanthin A
and in cycloviolaxanthin and alloxanthin, respectively,
were determined to be that shown. The relative stereochemistries of 2 and 3 were also supported by the resultsof NOESY and 1H-1H COSY experiments. The NOESY
data summary is given in Figure S1 of the Supporting
Information.
Carotenoid 4 was obtained as a red, amorphous solid,
with the molecular formula C40H56O5, as established by
HREIMS. The UV-vis spectrum of 4 in Et2O showed anabsorption maximum at 464 nm. As shown in Table 1, the
1H chemical shifts and the spin-couplings of H2 to H20 in
4 were almost identical with those in cycloviolaxanthin.6
The 1H NMR signals of the remaining protons in 4 weresimilar to those in mytiloxanthin.7 Thus, the structure of
4 was determined to be made up of the corresponding
partial structures in cycloviolaxanthin and mytiloxanthin.
The relative stereochemisty of 4 was also supported by the
results of the NOESY (Figure S1) and 1H-1H COSY
experiments and the 13C chemical shifts listed in theExperimental Section.

580

Journal of Natural Products, 2001, Vol. 64, No. 5

Maoka et al.

Figure 2. Structure and FAB MS/MS spectrum of carotenoid 4.

The absolute structures of 2, 3, and 4 were tentatively
postulated on the basis of the NOESY and the CD data.
The CD spectrum of 3 showed characteristic Cotton effects
similar to the combined CD spectra of cycloviolaxanthin(3S,5R,6R)6b and alloxanthin (3R),8 by the use of theadditivity rules of CD spectra of dichiral carotenoids.8 In
carotenoid 2, the 3S,5R,6R chiralities were postulated on
the basis of the fact that the CD spectrum of 2 exhibits
the same Cotton effects as that of cycloviolaxanthin.
The CD spectrum of 4 showed characteristic Cotton
effects similar to those of capsanthin 3,6-epoxide(3S,5R,6R,3′S,5′R), which possesses the same asymmetriccarbons and the same chromophore.6b
Taking the results of their CD and relative stereochemistries into account, the structures of 2, 3, and 4 were
determined to be (3S,5R,6R)-5-hydroxy-3,6:3′,6′-diepoxy5,6,1′,2′,5′,6′,7′,8′-octahydro-6′-methyl-16′-nor-β,φ-carotene1′,8′-dione, (3S,5R,6R,3′R)-3,6-epoxy-7′,8′-didehydro-5,6dihydro-β,β-carotene-5,3′-diol, and (3S,5R,6R,3′S,5′R)5,3′,8′-trihydroxy-3,6-epoxy-5,6-dihydro-β,κ-caroten-6′one, respectively.
Carotenoid 5 was obtained as a red, amorphoussolid exhibiting a molecular ion peak (HREIMS) at m/z
616.4119 corresponding to C40H56O5. The UV-vis spectrumof 5 in Et2O showed an absorption maximum at 457 nm.
The chemical structure of 5 was deduced to be that shownby comparing the 1H NMR data of 5 with those of thecorresponding partial structures in fucoxanthinol4 andmytiloxanthin.7 The relative stereochemistries in the end
groups of 5 were supported by the NOESY correlations andthe magnitudes of 1H-1H spin-couplings in Table 1. The
CD spectrum of 5 was similar to that of fucoxanthinol,8and the absolute stereochemistry of the other end group(C1′ to C6′) was deduced to be the same as in 4. Thus,

the absolute structure of 5 was determined to be(3S,5R,6R,3′S,5′R)-3,5,3′,8′-tertahydroxy-6,7-didehydro-5,6dihydro-β,κ-caroten-6′-one.
Finally, the FAB-MS/MS spectrum of 4 is shown in
Figure 2. As can be seen from Figure 2, the CID (collisioninduced dissociation) MS spectra of the M•+ (616) showed
the characteristic product ions resulting from the sequential cleavage of C-C bonds in the polyene chain in addition
to the [M - 18]•+ and [M - 80]•+.9 The characteristic
product ions were also observed for the CID MS spectra of
the M•+ of 2 and 3.
In addition to the new carotenois 1-5, 17 known carotenoids (see Experimental Section) were isolated andidentified by UV-vis, EIMS, CD, and 1H NMR. Theirstructures are presented in the Supporting Information
data, Figure S2.
Experimental Section
General Experimental Procedures. The UV-visible (vis)spectra were recorded on a Shimadzu UV-240 spectrophotometer in Et2O. The EIMS, FABMS, and FAB-MS/MS spectra
were recorded using a JEOL JMS-HX/HX 110A mass spectrometer. The EIMS spectra were recorded with a direct inlet
system with ionization energy of 70 eV. The positive ion FAB
MS/MS measurement conditions were as follows: matrix,
3-nitrobenzyl alcohol; accelerating voltage, 10 kV; emittercurrent, 5 mV; collision gas, argon; collision cell voltage, 3 kV.
The 13C (125 MHz) and 1H NMR (500 MHz) spectra wererecorded on a Varian UNITY INOVA 500 spectrometer in
CDCl3 with TMS as an internal standard. The 13C NMR
spectra of 1 (0.5 mg) and 4 (1 mg) were measured in 40 µL of
CDCl3 solution using a Nanoprobe (Varian). All two-dimensional experiments were carried out without sample spinning.
The gmq (pulsed field gradient multi-quantum) COSY, NOESY(mixing time 1.3 s), gHSQC (1JCH optimized for 142 Hz), andgHMBC (nJCH optimized for 8 Hz) spectra were acquired using

New Carotenoids from the Oyster Crassostrea

the standard Varian pulse programs. and the software used
to obtain 2D spectra was from Varian, version 6.1A. CD spectra
were recorded in Et2O at room temperature with a JASCO
J-500 spectropolarimeter. HPLC was performed on a Shimadzu LC-6AD instrument with a Shimadzu SPD-6AV spectrophotometer set at 450 nm. The columns used were a ShimPack PREP-SIL (Shimadzu, 20 mm × 250 mm, 5 µm) and a
Lichrospher 100 RP-18 (Cica Merck, 20 × 250 mm, 10 µm).
Animal Material. C. gigas was purchased at the fish
market in Kyoto City in February. Voucher specimens2 havebeen deposited at Kyoto Pharmaceutical University.
Extraction and Isolation of Carotenoids. The Me2CO
extract of the edible parts of C. gigas (10 kg) was partitioned
between n-hexanes-Et2O (1:1) and aqueous NaCl. The organic
layer was dried over Na2SO4 and then concentrated to dryness.
The residue was subjected to column chromatography (CC) on
Si gel using an increasing percentage of Me2CO in n-hexane.
The fraction eluted with n-hexane-Me2CO (1:1) from a Si gel
column was purified by HPLC on silica with n-hexane-Me2CO (7:3) and further purified by HPLC on ODS with CHCl3MeCN (1:9) to yield 1 (0.5 mg), 2 (1 mg), 3 (0.5 mg), and 4 (1mg). The fraction eluted with Me2CO from a Si gel column
was further purified by HPLC on silica with n-hexane-Me2CO (6:4) and on ODS with CHCl3-MeCN (1:9) to yield 5 (0.5mg).
In the present isolation, the following additional known
carotenoids3,4,8,9 were isolated and identified by UV-vis, EIMS,
1H NMR, and CD spectral data: alloxanthin (5 mg) and its
3-acetate (3 mg), 8′-apo-alloxanthinal (5 mg), crassostreaxanthin A (10 mg) and its 3-acetate (4 mg), crassostreaxanthin B(6 mg) and its 3-acetate (4 mg), diatoxanthin (4 mg), fucoxanthin (4 mg), fucoxanthinol (2 mg), halocynthiaxanthin (20mg)and its 3′-acetate (5 mg), mytiloxanthin (12 mg), pectenol
A (2 mg), peridinin (5 mg), peridininol (1 mg), pyrrhoxanthinol(2 mg).
Carotenoid 1: red, amorphous solid; UV-vis (Et2O) λmax
457 nm; CD (Et2O) λext(∆) 225 (-6.8), 255 (+10.2), 352 (-6.1);
1H NMR (CDCl ), Table 1; 13C NMR (CDCl ) δ 14.0 (q, C-19),3
3
15.4 (q, C-20′), 18.9 (q, C-18′), 21.4 (q, CH3CO), 23.0 (q, C-16′),24.3 (q, C-17′), 29.1 (q, C-16), 31.2 (q, C-18), 32.0 (q, C-17),35.8 (s, C-1), 41.6 (s, C-1′), 45.2 (t, C-4), 45.4 (t, C-2), 49.7 (t,C-2′), 67.9 (d, C-3), 72.6 (s, C-5), 79.7 (s, C-6′), 103.3 (d, C-8),
117.6 (s, C-6), 119.9 (d, C-12′), 122.6(d, C-8′),124.4(s, C-9′),
127.3 (d, C-4′), 128.1 (d, C-12), 128.8 (d, C-15′), 131.7 (d, C-13),
132.9 (s, C-9), 133.8 (d, C-14), 134.1 (s, C-13′), 136.2 (d, C-7′),
136.9 (d, C-10′), 137.6 (d, C-15), 138.6 (d, C-14′), 146.6(s, C-11′),161.4 (s, C-5′), 168.7 (s, C-19′), 170.4 (s, CH3CO), 197.7 (s, C-3′),
202.7 (s, C-7); EIMS m/z 628 [M]+ (18), 610 (100), 550 (74),536 (12), 416 (20), 397 (20), 297 (20), 223 (42), 197 (34), 152(34), 43 (34); HREIMS m/z 628.3395 (calcd for C39H48O7,
628.3394).
Carotenoid 2: orange, amorphous solid; UV-vis (Et2O)
λmax 443, 468 nm (%III/II ) 65); CD (Et2O) λext(∆) 235 (-1),
285 (+1), 325 (-1); 1H NMR (CDCl3), Table 1; EIMS m/z 616[M]+ (30), 598 (2), 558 (4), 524 (4), 462 (15), 221 (13), 155 (100),
113(20), 43(16); HREIMS m/z, 616.4137 (calcd for C40H56O5,
616.4125).
Carotenoid 3: orange, amorphous solid; UV-vis (Et2O)
λmax 446, 476 nm (%III/II ) 65); CD (Et2O) λext(∆) 240 (-2),

Journal of Natural Products, 2001, Vol. 64, No. 5 581

275 (0), 320 (-1.7); 1H NMR (CDCl3), Table 1; EIMS m/z 582[M]+ (100), 564 (5), 502 (5), 490(10), 299 (12), 286 (21), 221(37), 181(13), 160 (15), 43 (12); HREIMS m/z, 582.4080 (calcd
for C40H54O3, 582.4072).
Carotenoid 4: red, amorphous solid; UV-vis (Et2O) λmax
464 nm; CD (Et2O) λext(∆) 240 (-0.5), 280 (+1), 360 (-2); 1H
NMR (CDCl3), Table 1; 13C NMR (CDCl3) δ 12.5 (q, C-20′),12.8 (q, C-20), 12.9 (q, C-19), 12.9 (q, C-19′), 22.2 (q, C-18′),25.0 (q, C-17′), 25.7 (q, C-16), 25.9 (q, C-16′), 31.6 (q, C-18),
32.2 (q, C-17), 44.0 (s, C-1), 44.7 (s, C-1′), 45.2 (t, C-4′), 47.7 (t,C-4), 48.5 (t, C-2), 50.8 (t, C-2′), 56.1 (s, C-5′), 70.5 (d, C-3′),
75.4 (d, C-3), 82.5 (s, C-5), 91.7 (s, C-6), 94.5 (d, C-7′), 123.2(d, C-7), 123.3 (d, C-14), 123.6 (d, C-11′), 125.5 (d, C-11), 129.6(d, C-15), 131.5 (d, C-10), 132.6 (d, C-15′), 134.8 (d, C-8), 135.3(s, C-9), 135.7 (s, C-13), 135.8 (d, C-10′), 135.8 (d, C-14′), 136.4(s, C-9′), 137.6 (d, C-12), 137.8 (s, C-13′), 144.0 (d, C-12′), 182.0(s, C-8′), 202.3 (s, C-6′); EIMS m/z 616 [M]+ (100), 598 (15),580 (5), 536 (7), 524 (20), 506 (10), 419 (5), 313 (17), 287 (23),221 (63), 179(35), 109 (43), 83 (25), 43 (22); HREIMS m/z
616.4133 (calcd for C40H56O5, 616.4125).
Carotenoid 5: red, amorphous solid; UV-vis (Et2O) λmax
468 nm; CD (Et2O) λext(∆): 227 (-1.5), 290 (-3), 370 (-1); 1H
NMR (CDCl3), Table 1; EIMS m/z 616 [M]+ (32), 598 (33), 580(10), 524 (5), 386 (10), 237 (23), 197 (42), 179 (25), 127 (35),109 (100), 83 (40), 43 (32); HREIMS m/z 616.4119 (calcd for
C40H56O5, 616.4125).
Supporting Information Available: Figure S1 indicating NOESY data summary of 1-5. Figure S2 indicating structures of 17 known
carotenoids. This material is available free of charge via the Internet
at http://pubs.acs.org.

References and Notes(1) (a) Ida, K.; Masamoto, K.; Maoka, T.; Fujiwara, Y.; Takeda, S.;
Hasegawa, E. J. Plant Res. 1995, 108, 369-376. (b) Tsushima, M.;
Fujiwara, Y.; Matsuno, T. J. Nat. Prod. 1996, 59, 30-34. (c) Maoka,
T.; Mochida, K.; Okuda, Y.; Ito, Y.; Fujiwara, Y. Chem. Pharm. Bull.
1997, 45, 1225-1227. (d) Fujiwara, Y.; Maoka, T. Tetrahedron Lett.
2001, 42, 2693-2696.
(2) Fujiwara, Y.; Maoka, T.; Ookubo, M.; Matsuno, T. Tetrahedron Lett.
1992, 33, 4941-4944.
(3) Britton, G. In UV/Visible Spectroscopy in Carotenoids; Britton, G.,
Liaaen-Jensen, S., Pfander, H., Eds.; Birkhäuser Verlag: Basel, 1995;
Vol. 1B, pp 13-62.
(4) (a) Englert, G. In NMR Spectroscopy in Carotenoids; Britton, G.;
Liaaen-Jensen, S., Pfander, H., Eds.; Birkhäuser Verlag: Basel, 1995;
Vol. 1B, pp 147-260. (b) Haugan, J. A.; Englert, G.; Aakermann, T.;
Glinz, E.; Liaaen-Jensen, S. Acta Chem. Scand. 1994, 48, 769-778.
(5) Matsuno, T.; Ookubo, M.; Komori, T. J. Nat. Prod. 1985, 48, 606613.
(6) (a) Deli, L.; Molanar, P.; Toth, G., Baumeler, A.; Eugster, C. H. Helv.
Chim. Acta 1991, 74, 819-824. (b) Deli, L.; Molnar, P.; Matus, Z.;
Toth, G.; Steck, A. Helv. Chim. Acta 1996, 79, 1435-1443.
(7) (a) Khare, A.; Moss, G. P.; Weedon, B. C. L. Tetrahedron Lett. 1973,
3921-3922. (b) Maoka, T.; Fujiwara, Y. J. Jpn. Oil Chem. Soc. 1996,
45, 667-670.
(8) Buchecker, R.; Noack, K. Circular Dichroism in Carotenoids; Britton,
G., Liaaen-Jensen, S., Pfander, H., Eds.; Birkhäuser Verlag: Basel,
1995; Vol. 1B, Chapter 3, pp 63-116.
(9) (a) Johannes, B.; Brzezinka, H.; Budzikiwiez, H. Org. Mass Spectrom.
1974, 9, 1095-1113. (b) Budzikiwiez, H. In Mass Spectra of Carotenoids-Labeling Studies in Carotenoid Chemistry and Biochemistry;
Britton, G., Goodwin, T. W., Eds.; Pergamon Press: Oxford, 1983;
pp 155-165.

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