Absolute configuration of some marine metabolites from Cystoseira spp.

Article abstract of DOI:10.1021/np9700432

The absolute configuration of meroditerpenoid metabolites isolated from Mediterranean brown algae of the genus Cystoseira has been determined using a recent modification of Mosher's method. The data obtained suggest that the compounds examined are interconnected through a stereocontrolled enzymatic reaction. This constitutes another confirmatory step in the validation of a previously proposed biosynthetic pathway for Cystoseira metabolites.

Full text of DOI:10.1021/np9700432

1088
J . Nat. Prod. 1997, 60, 1088-1093
Absolu te Con figu r a tion of Som e Ma r in e Meta bolites fr om Cystoseir a sp p .
Vincenzo Amico,*,† Mario Piattelli,† Mario Bizzini,† and Placido Neri*,‡
Dipartimento di Scienze Chimiche, Universita` degli Studi di Catania, Viale A. Doria 6, 95125 Catania, Italy, and
Istituto per lo Studio delle Sostanze Naturali di Interesse Alimentare e Chimico-Farmaceutico, CNR, Via del Santuario 110,
I-95028 Valverde (CT), Italy
Received J anuary 10, 1997X
The absolute configuration of meroditerpenoid metabolites isolated from Mediterranean brown
algae of the genus Cystoseira has been determined using a recent modification of Mosher’s
method. The data obtained suggest that the compounds examined are interconnected through
a stereocontrolled enzymatic reaction. This constitutes another confirmatory step in the
validation of a previously proposed biosynthetic pathway for Cystoseira metabolites.
The algal genus Cystoseira (Order Fucales, Family
Cystoseiraceae) is undoubtedly the most important in
the Mediterranean ecosystem, due to its number of
species (about 30), its abundance, and the conspicuous
size of many of the algae. Chemical examination of
species collected along the Sicilian coasts has led to the
isolation of a vast number of secondary metabolites,
including tens of meroditerpenoids. These have been
interrelated in a meaningful, although admittedly specu-
lative, biogenetic pathway. In brief, from geranylger-
anyltoluquinol, oxidation of the diterpenoid moiety
generates compounds containing hydroxyl or carbonyl
functions, e.g. 1 and 2. Further transformations can
afford compounds in which the distal isoprene unit has
been converted into a tetrahydrofuran ring as in zoster-
diol A (3), while more complex sequences of biosynthetic
steps would lead, through the monocarbocyclic diketone
5, to polycyclic metabolites exemplified by cystalgerone
4 and balearone 6. The irregular diterpenoid neobale-
arone 7 is apparently derived from geranyllavandulyl-
toluquinol, possibly through a biosynthetic pathway
parallel to that leading to balearone and perhaps
catalyzed by the same enzymes.1,2
In general, the gross structures of the Cystoseira
metabolites have been determined largely by spectro-
scopic means, on occasion with the aid of chemical
transformations. The relative stereochemistry of com-
pounds containing more than one chiral center has been
1
assessed, at least in the case of rigid systems, by H-
NMR spectroscopy (and by X-ray diffraction analysis for
balearone). The problem of the absolute configuration
remained unsolved, as well as that of the configuration
of compounds containing more centers in a flexible
structure (e.g. 1). The recent availability of a modifica-
tion of the Mosher method for the elucidation of the
absolute configuration of secondary alcohols,3 more
reliable than that originally proposed,4,5 prompted us
to apply the new methodology to some representatives
of the family of Cystoseira meroditerpenoids. The new
version of the Mosher technique requires coupling of the
chiral secondary alcohol with each of the enantiomeric
Mosher acid [2-methoxy-2-phenyl-2-(trifluoromethyl)-
* To whom correspondence should be addressed. V. Amico: phone
+39-95-330533 ext. 461; fax +39-95-580138; e-mail vamico@dipchi.
unict.it. P. Neri: phone +39-95-7212136; fax +39-95-7212141; e-mail
neri@issn.ct.cnr.it.
† Dipartimento di Scienze Chimiche.
acetic acid, MTPA] chlorides. Next, assignments of as
many resonances as possible are made in the H-NMR
‡Istituto per lo Studio delle Sostanze Naturali.
1
X Abstract published in Advance ACS Abstracts, October 1, 1997.
S0163-3864(97)00043-8 CCC: $14.00
© 1997 American Chemical Society and American Society of Pharmacognosy

Marine Metabolites from Cystoseira spp.
J ournal of Natural Products, 1997, Vol. 60, No. 11 1089
Ta ble 1. Relevant ∆δ Values (∆δ ) δS - δR) Obtained for the
MTPA Esters of Compounds 1a -7a and 4b
MTPA-2a and (R)-MTPA-2a (Table 1) allowed the
determination of the stereochemistry at position 5,
whereas the configuration at C-11 remains to be ascer-
tained.
H position
1a
2a
3
4a
4b
6a
7a
1-Ha
1-Hb
2
4-Ha
4-Hb
5
6
8
9
10
0.05
0.10
0.06
0.07
0.05
0.05
0.09
0.09
0.06
0.03
0.06
0.09
0.09
0.06
The study has been extended to the monocylic zoster-
diol A (3), possessing, in addition to the oxygen-bearing
chiral centers at position 5 and 12 present in 1, an
additional secondary hydroxyl group at position 14.10
Treatment of 3 with MTPA-Cl afforded the diesters (S)-
MTPA-3 and (R)-MTPA-3, whose 1H-NMR spectra
were assigned with the aid of 2D COSY experiments.
From the ∆δ values of the two diesters, the stereochem-
istry of the three chiral centers was determined as R.
It is noteworthy that the configuration of the C-5
carbinol center is the same in the three metabolites 1,
2, and 3, a fact that reinforces the validity of the
method.
0.15
-0.08
0.04
0.03
-0.02 -0.03 -0.02
-0.17 -0.16 -0.14
-0.22 -0.04
0.02
-0.07 -0.03
-0.10
-0.07
0.06
0.04
0.11
0.03
0.07
0.02
12
0.38
0.02
13-Ha
13-Hb
14-Ha
14-Hb
16
17
18
19
20
0.12
0.07
0.13
0.10
0.03 -0.07
0.04
0.03
0.03
0.09
0.07
0.05
-0.10
0.38
0.09 -0.03 -0.08
0.06 -0.15 -0.04
-0.13 -0.02
0.32 -0.39
0.02 -0.15
0.09
0.02
0.11
Cystalgerone (4), possessing a bicyclo[4.3.0]nonane
ring system,11 was reduced with NaBH4 to give two
epimeric alcohols 4a and 4b in 40 and 4% yield,
respectively. The structure of these compounds were
-0.02 -0.02 -0.23
0.08
0.08
0.08 -0.05
0.05
spectrum for each of the (R)- and (S)-MTPA esters,
followed by evaluation of the difference in chemical shift
(∆δ ) δS-ester - δR-ester) of like sets of protons in the
two esters. Finally, confirmation that the assigned
protons with positive ∆δ values are on the right side,
and those with negative values on the left side, of the
so-called MTPA plane in the idealized conformation of
the esters. This empirical methodology has the advan-
tage over others, such as the Horeau,6 Mislow,7 or the
original Mosher method, in that it is dependent on many
point comparisons (the chemical shifts of many like sets
of protons) instead of only one parameter.
1
confirmed by inspection of their H-NMR spectra, which
differ from that of the parent ketone by the presence of
an additional signal (at 3.82 ppm in 4a and 4.20 ppm
in 4b) due to the oxymethine proton at position 12. A
2D NMR analysis (COSY, HETCOR, long-range HET-
COR) of 4a resulted in the unambiguous assignment of
all the resonances, while a NOESY spectrum showed
that OH-12 is cis-oriented with respect to Me-18 and
Me-19 (obviously the opposite trans-orientation has to
be assumed for 4b). Conversion of 4a into the Mosher
esters (S)-MTPA-4a and (R)-MTPA-4a , followed by
analysis of the 1H-NMR data, revealed that the absolute
stereochemistry of the alcohol 4a must be 7R,11R,12R,
and this implies the 7R,11R configuration for cystal-
gerone 4. The results obtained for MTPA-4a (Table
1) include three irregular ∆δ values (+0.15 of 4-H, +0.03
of 14-H, and +0.09 of 16-H), therefore in order to avoid
any uncertainty on the exact assignment of absolute
configuration, we also applied the MTPA method on the
isomer 4b. This second determination confirms the
C-12 configuration, assessing the absolute stereochem-
istry of epimer 4b as 7R,11R,12S.
Resu lts a n d Discu ssion
Compounds with open-chain (1 and 2), monocyclic (3
and 5), bicyclic (4), and tricyclic (6 and 7) diterpene
moieties were selected for the present study, as repre-
sentative of the most characteristic subgroups of the
Cystoseira metabolites.
The first compound examined was 1, isolated from
Cystoseira adriatica,8 which possesses two stereogenic
centers, whose configurations had been unknown, at
position 5 and 12 of its open-chain diterpenoid moiety.
To avoid possible complications, such as cyclization to
the corresponding chromane9 or reaction of the free
phenolic hydroxyl with MTPA-Cl, the 1′-phenolic group
was methylated (MeI/K2CO3) to give 1a . This was then
reacted with MTPA-Cl to afford the diastereoisomeric
esters (R)-MTPA-1a and (S)-MTPA-1a . Analysis of
their 2D COSY spectra resulted in the complete assign-
ment of the 1H-NMR resonances, including those for the
methyl groups on sp2 carbons, which were identified
from their allylic couplings. The diagnostic ∆δ values
for like protons of (S)- and (R)-MTPA-1a are reported
in Table 1. The systematic arrangement of positive and
negative ∆δ values for the protons surrounding the two
chiral centers, with the inversion of sign passing
through them, allows a confident attribution of the R
stereochemistry to both position 5 and 12. Therefore,
the compound in question is (5R,12R)-(2E,6E,10E)-1-
(2′-hydroxy-5′-methoxy-3′-methylphenyl)-3,7,11,15-tet-
ramethylhexadeca-2,6,10,14-tetraene-5,12-diol.
Determination of the absolute configuration of 4
allowed us to assess the stereochemistry of the mono-
cyclic metabolite 5, originally isolated from Cystoseira
algeriensis.12 Treatment of 5 with base resulted in the
facile conversion into a compound spectroscopically
indistinguishable from 4 and with the same specific
optical rotation. Therefore, the 7R,11R absolute con-
figuration can be confidently assigned to 5.
Balearone 6, having a bicyclo[3.2.0]heptane system
spiro-fused with a tetrahydrofuran ring, exemplifies the
structurally most complicated Cystoseira metabolites.13-15
In this case also, methylation of the free phenolic
hydroxyl to afford 6a preceded coupling with each of the
enantiomers of the Mosher acid chloride to yield the
esters (S)-MTPA-6a and (R)-MTPA-6a . Unambiguous
assignment of the proton resonances of these latter
could not be obtained from a COSY spectrum and
required a HETCOR experiment. Consideration of the
chemical shift differences for the relevant protons (Table
1) demonstrates that the larger values are observed for
Me-18 (∆δ ) +0.09) and for Me-17 of MTPA-6a . This
is surprising in terms of the conventional “ideal” con-
Analogously, the methyl ether 2a obtained from 27
by methylation was converted into the (R)- and (S)-
MTPA esters. Comparison of the ∆δ values for (S)-

1090 J ournal of Natural Products, 1997, Vol. 60, No. 11
Amico et al.
formation of the modified Mosher’s method, but can find
an explanation in the observation that, in an energy-
minimized three-dimensional molecular model, Me-17
and Me-18 reside in the right and left sides of the
“MTPA plane”, respectively. Therefore, the absolute
stereochemistry at C-14 can be confidently assigned as
R and, from the relative stereochemistry determined
through X-ray analysis, the absolute configuration of the
remaining centers in 6 must be 6R,7R,11R,12S. It is
to be noted that the junction of the cyclopentane ring
in 6 has the same absolute cis geometry as that in 4
and 5 and that the chiral center at position 14 has the
same R configuration found in 3.
The study of the irregular meroditerpenoid neobale-
arone 716 followed the same route as for 6. Initial
methylation yielded the methyl derivative 7a , which
was reacted with MTPA-Cl to give (S)-MTPA-7a and
(R)-MTPA-7a . The chemical shift differences (Table
1) closely paralleled those of 6a , indicating an absolute
configuration identical to that of balerone, i.e. 6R,7R,-
11R,12S,14R.
In conclusion, the absolute configuration of the ste-
reogenic carbinol centers in seven algal meroditerpe-
noids (1-7) from Cystoseira species has been deter-
mined using the refined Mosher strategy developed by
Kakisawa and Kashman.3 The results, in conjunction
with information on the relative stereochemistry avail-
able from our earlier studies, allowed the complete
assignment of the absolute stereochemistry for all of
these compounds but 2, which embodies a stereogenic
center whose configuration remains to be assessed.
and the solution extracted with ether. The ether extract
was dried over Na2SO4 and evaporated. The residue
was subjected to preparative LC (Merck, Kieselgel 60,
Et2O/n-hexane, 1:1) to give pure 1a (150 mg, 75%): 1H-
NMR δ 6.54 (bs, 2 H), 5.40 (t, J ) 6.9 Hz, 1 H), 5.34 (t,
J ) 6.2 Hz, 1 H), 5.14 (d, J ) 8.0 Hz, 1 H), 5.08 (t, J )
6.3 Hz, 1 H), 4.47 (m, 1 H), 3.96 (bt, J ) 6.5 Hz, 1 H),
3.73 (s, 3 H), 3.67 (s, 3 H), 3.36 (d, J ) 7.1 Hz, 2 H),
2.26 (s, 3 H), 1.78 (s, 3 H), 1.71 (s, 3 H), 1.68 (s, 3 H),
1.62 (s, 3 H), 1.60 (s, 3 H); 13C-NMR δ 155.5 (s), 150.3
(s), 137.5 (s), 137.1 (s), 134.8 (s), 134.3 (s), 132.5 (s),
131.8 (s), 127.7 (d), 126.8 (d), 125.7 (d), 120.2 (d) 113.7
(d), 112.7 (d), 77.3 (d), 66.0 (d), 60.3 (q), 55.3 (q), 48.1
(t), 39.0 (t), 34.0 (t), 28.7 (t), 25.8 (q), 25.6 (t), 17.9 (q),
16.5 (q), 16.3 (q), 11.5 (q).
(R)-MTP A-1a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) followed by Et2O/
n-hexane (8:92) as eluent: 1H-NMR δ 7.49 (m, mtpa-
ArH, 4 H), 7.37 (m, mtpa-ArH, 6 H), 6.54 and 6.46 (AB,
J ) 3.1 Hz, 3′-H and 5′-H, 2 H), 5.89 (m, H-5, 1 H), 5.52
(t, J ) 6.4 Hz, H-10, 1 H), 5.36 (dd, J ) 8.0, 6.1 Hz,
H-12, 1 H), 5.30 (bt, J ) 7.8 Hz, H-2, 1 H), 5.19 (d, J )
9.1 Hz, H-6, 1 H), 4.91 (t, J ) 7.3 Hz, H-14, 1 H), 3.71
(s, 4′-OMe, 3 H), 3.64 (s, 1′-OMe, 3 H), 3.50 (bs, mtpa-
OMe, 6 H), 3.29 (dd, J ) 15.4, 7.8 Hz, Ha-2, 1 H), 3.19
(dd, J ) 15.4, 6.9 Hz, Hb-2, 1 H), 2.43 (Ha-4, 1 H, from
COSY), 2.40 (Ha-13, 1 H, from COSY), 2.26 (s, 6′-Me, 3
H), 2.25 (Hb-13, 1 H, from COSY), 2.24 (Hb-4, 1 H, from
COSY), 2.12 (H-8, 2 H, from COSY), 2.07 (H-9, 2 H, from
COSY), 1.78 (s, H-19, 3 H), 1.70 (s, H-20, 3 H), 1.62 (s,
H-16, 3 H), 1.59 (s, H-18, 3 H), 1.53 (s, H-17, 3 H).
Exp er im en ta l Section
(S)-MTP A-1a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) followed by Et2O/
n-hexane (8:92) as eluent: 1H-NMR δ 7.47 (m, mtpa-
ArH, 4 H), 7.37 (m, mtpa-ArH, 6 H), 6.54 and 6.48 (AB,
J ) 3.1 Hz, 3′-H and 5′-H, 2 H), 5.87 (m, H-5, 1 H), 5.42
(t, J ) 7.0 Hz, H-10, 1 H), 5.36 (bt, J ) 7.2 Hz, H-2, 1
H), 5.29 (dd, J ) 8.3, 5.7 Hz, H-12, 1 H), 5.02 (d, J )
9.1 Hz, H-6, 1 H), 5.02 (H-14, 1 H, from COSY), 3.71 (s,
4′-OMe, 3 H), 3.65 (s, 1′-OMe, 3 H), 3.53 (bs, mtpa-OMe,
3 H), 3.47 (bs, mtpa-OMe, 3 H), 3.34 (dd, J ) 14.5, 6.6
Hz, Ha-2, 1 H), 3.29 (dd, J ) 14.5, 5.9 Hz, Hb-2, 1 H),
2.50 (Ha-4, 1 H, from COSY), 2.46 (Ha-13, 1 H, from
COSY), 2.29 (Hb-13, 1 H, from COSY), 2.29 (Hb-4, 1 H,
from COSY), 2.26 (s, 6′-Me, 3 H), 2.00 (H-9, 2 H, from
COSY), 1.90 (H-8, 2 H, from COSY), 1.78 (s, H-20, 3
H), 1.76 (s, H-19, 3 H), 1.69 (s, H-16, 3 H), 1.58 (s, H-17,
3 H), 1.46 (s, H-18, 3 H).
Gen er a l Exp er im en ta l P r oced u r es. Metabolites
1-7 were available from previous studies or isolated
from the corresponding Cystoseira spp. as previously
described.7-16 NMR spectra were taken on a Bruker
AC-250 spectrometer operating at 250.13 (1H) and 62.9
(13C) MHz using CDCl3 solutions with TMS as internal
standard. 13C-DEPT and 2D NMR (COSY, HETCOR,
long-range HETCOR, and NOESY) experiments were
performed using standard pulse sequences of Bruker
microprograms. Long-range HETCOR spectra were
acquired using a polarization transfer delay optimized
to observe J ) 10 Hz. Mixing time in NOESY experi-
ment was 0.8 s. (R)- and (S)-Mosher acid chloride
[R-methoxy-R-(trifluoromethyl)phenylacetic acid chlo-
ride, MTPA-Cl] were purchased from Aldrich or pre-
pared from the corresponding acids by treatment with
SOCl2, paying attention that (R)-(+)-MTPA acid gives
(S)-(+)-MTPA acid chloride and vice versa.
Gen er al P r ocedu r es for th e P r epar ation of MTP A
Ester s. (R)- or (S)-MTPA chloride (2-fold millimolar
excess over starting alcohol) was added to a solution of
starting meroditerpenoid (usually 15-25 mg) in pyri-
dine (200 µL), and the resulting mixture was allowed
to stand at room temperature for 4 h. Triethylamine
(12.4 µL) was then added, and after 10 min of standing
the solvent was removed under vacuum. The residue
was chromatographed over a sep-pak cartridge to give
the purified Mosher ester.
Meth yla tion of 2 To Give 2a . A suspension con-
taining 2 (100 mg), MeI (1 mL), and Cs2CO3 (150 mg)
in 6 mL of acetone was stirred under reflux for 20 h.
Usual workup followed by PLC (silica gel, Et2O/n-
hexane, 2:3) afforded 2a (30 mg): 1H-NMR δ 6.54 and
6.55 (AB, J ) 2.9 Hz, H-3′, H-5′, 2 H), 5.40 (t, J ) 6.8
Hz, H-2, 1 H), 5.28 (bt, J ) 7.0 Hz, H-14, 1 H), 5.15 (bd,
J ) 7.5 Hz, H-6, 1 H), 4.47 (m, H-5, 1 H), 3.73 (s, 4′-
OMe, 3 H), 3.67 (s, 1′-OMe, 3 H), 3.37 (bd, J ) 6.8, H-1,
2 H), 3.12 (d, J ) 7.0 Hz, H-13, 2 H), 2.56 (m, H-11, 1
H), 2.26 (s, 6′-Me, 3 H), 1.78 (s, H-20, 3 H), 1.74 (s, H-16,
3 H), 1.65 (s, H-19, 3 H), 1.62 (s, H-17, 3 H), 1.05 (d, J
) 6.9 Hz, H-18, 3 H); 13C-NMR δ 212.8 (s), 155.6 (s),
150.4 (s), 148.7 (s), 137.8 (s), 135.4 (s), 134.8 (s), 132.5
(s), 131.8 (s), 127.6 (d), 127.0 (d), 116.1 (d), 113.8 (d),
Meth yla tion of 1 To Give 1a . MeI (2 mL) and K2-
CO3 (1 g) were added to a solution of 1 (200 mg) in
acetone (10 mL), and the resulting suspension was
stirred under reflux for 15 h. Water was then added

Marine Metabolites from Cystoseira spp.
J ournal of Natural Products, 1997, Vol. 60, No. 11 1091
112.8 (d), 66.0 (d), 60.4 (q), 55.3 (q), 48.2 (t), 45.6 (d),
41.0 (t), 39.4 (t), 32.5 (t), 28.9 (t), 25.7 (q), 25.2 (t), 18.1
(q), 16.5 (q), 16.4 (q).
Red u ction of Keton e 4 To Give Alcoh ols 4a a n d
4b. A solution of 4 (560 mg) in EtOH (32 mL) was
added to an excess of NaBH4 (60 mg) and then allowed
to stand for 45 min at room temperature. The solution
was then quenched with H2O and partitioned with Et2O.
The organic phase was dried, evaporated, and subjected
to PLC (silica gel, Et2O/CH2Cl2, 13:87) to give in eluting
order 4b (20 mg, 4%) and 4a (200 mg, 40%).
Cysta lger olo 4a : 1H-NMR δ 6.56 and 6.54 (AB, J )
3.1 Hz, H-5′ and H-3′, 2 H), 5.33 (t, J ) 7.2 Hz, H-2, 1
H), 3.82 (s, H-12, 1 H), 3.74 (s, 4′-OMe, 3 H), 3.68 (s,
3′-OMe, 3 H), 3.36 (d, J ) 7.2 Hz, H-1, 2 H), 3.12 (d, J
) 14.2 Hz, Ha-4, 1 H), 2.95 (d, J ) 14.4 Hz, Ha-14, 1 H),
2.52 (d, J ) 14.2 Hz, Hb-4, 1 H), 2.11 (d, J ) 14.4 Hz,
Hb-14, 1 H), 2.27 (s, 6′-Me, 3 H), 1.96 and 1.85 (AB, J )
17.3 Hz, H-6, 2 H), 1.74 (H-9, 2 H, from HETCOR), 1.60
(s, H-20, 3 H), 1.57 and 1.33 (H-8, 2 H, from HETCOR),
1.30 (s, H-17, 3 H), 1.24 (H-10, 2 H, from HETCOR),
1.20 (s, H-16, 3 H), 0.98 (s, H-19, 3 H), 0.73 (s, H-18, 3
H); 13C-NMR δ 155.5 (s, 4′), 150.3 (s, 1′), 135.8 (s, 5),
135.0 (s, 2′), 134.2 (s, 3), 131.7 (s, 6′), 128.9 (s, 13), 124.6
(d, 2), 113.8 (d, 5′), 112.4 (d, 3′), 77.9 (d, 12), 71.4 (s,
15), 60.4 (q, 1′-OMe), 55.3 (s, 4′-OMe), 47.3 (t, 14), 46.7
(s, 11), 45.0 (t, 4), 41.1 (t, 6), 40.8 (s, 7), 36.7 (t, 8), 31.5
(q, 17), 30.1 (t, 10), 28.4 (q, 16), 28.2 (t, 1), 24.8 (q, 19),
22.4 (q, 18), 19.1 (t, 9), 16.4 (q, 6′-Me), 15.7 (q, 20).
(R)-MTP A-2a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (2:3) as eluent: 1H-
NMR δ 7.49 (m, mtpa-ArH, 2 H), 7.37 (m, mtpa-ArH, 3
H), 6.54 and 6.47 (AB, J ) 2.9 Hz, 3′-H and 5′-H, 2 H),
5.88 (m, H-5, 1 H), 5.28 (bt, J ) 7.1 Hz, H-2 and H-14,
2 H), 5.16 (d, J ) 9.3 Hz, H-6, 1 H), 3.73 (s, 4′-OMe, 3
H), 3.65 (s, 1′-OMe, 3 H), 3.50 (bs, mtpa-OMe, 3 H), 3.27
(dd, J ) 15.5, 7.5 Hz, Ha-2, 1 H), 3.20 (dd, J ) 15.5, 6.8
Hz, Hb-2, 1 H), 3.12 (d, J ) 7.2 Hz, H-13, 2 H), 2.54 (m,
H-11, 1 H), 2.41 (dd, J ) 13.8, 7.7 Hz, Ha-4, 1 H), 2.26
(s, 6′-Me, 3 H), 2.24 (dd, J ) 13.8, 5.1 Hz, Hb-4, 1 H),
1.98 (bt, J ) 7.3 Hz, H-8, 2 H), 1.75 (s, H-19, 3 H), 1.74
(s, H-16, 3 H), 1.69 (s, H-20, 3 H), 1.61 (s, H-17, 3 H),
1.06 (d, J ) 6.9 Hz, H-18, 3 H).
(S)-MTP A-2a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (2:3) as eluent: 1H-
NMR δ 7.44 (m, mtpa-ArH, 2 H), 7.37 (m, mtpa-ArH, 3
H), 6.55 and 6.48 (AB, J ) 3.0 Hz, 3′-H and 5′-H, 2 H),
5.85 (m, H-5, 1 H), 5.37 (t, J ) 7.0 Hz, H-2, 1 H), 5.28
(t, J ) 7.0 Hz, H-14, 1 H), 5.00 (d, J ) 7.9 Hz, H-6, 1
H), 3.72 (s, 4′-OMe, 3 H), 3.65 (s, 1′-OMe, 3 H), 3.47
(bs, mtpa-OMe, 3 H), 3.32 (dd, J ) 15.4, 8.0 Hz, Ha-2, 1
H), 3.29 (dd, J ) 15.4, 7.3 Hz, Hb-2, 1 H), 3.12 (d, J )
7.2 Hz, H-13, 2 H), 2.51 (m, H-11, 1 H), 2.47 (dd, J )
14.2, 8.0 Hz, Ha-4, 1 H), 2.27 (dd, J ) 14.2, 5.1 Hz, Hb-
4, 1 H), 2.27 (s, 6′-Me, 3 H), 1.94 (bt, J ) 7.6 Hz, H-8)
2 H), 1.77 (s, H-20, 3 H), 1.74 (s, H-16, 3 H), 1.73 (s,
H-19, 3 H), 1.61 (s, H-17, 3 H), 1.04 (d, J ) 7.0 Hz, H-18,
3 H).
(R)-MTP A-4a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) as eluent: 1H-NMR
δ 7.54 (m, mtpa-ArH, 2 H), 7.41 (m, mtpa-ArH, 3 H),
6.55 and 6.51 (AB, J ) 2.9 Hz, H-5′ and H-3′, 2 H), 5.27
(t, J ) 6.9 Hz, H-2, 1 H), 3.72 (s, 4′-OMe, 3 H), 3.66 (s,
3′-OMe, 3 H), 3.65 (bs, mtpa-OMe, 3 H), 3.34 (d, J )
7.5 Hz, H-1, 2 H), 3.32 (s, H-12, 1 H), 2.88 (d, J ) 15
Hz, Ha-14, 1 H), 2.85 (d, J ) 15.0 Hz, Ha-4, 1 H), 2.57
(d, J ) 15.0 Hz, Hb-14, 1 H), 2.48 (d, J ) 15.0 Hz, Hb-4,
1 H), 2.26 (s, 6′-Me, 3 H), 1.69 (s, H-20, 3 H), 1.60 (s,
H-17, 3 H), 1.43 (s, H-16, 3 H), 0.77 (s, H-19, 3 H), 0.31
(s, H-18, 3 H).
(R)-MTP A-3. Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) as eluent: 1H-NMR
δ 7.50 (m, mtpa-ArH, 4 H), 7.41 (m, mtpa-ArH, 3 H),
7.37 (m, mtpa-ArH, 3 H), 6.54 and 6.46 (AB, J ) 2.9
Hz, 3′-H and 5′-H, 2 H), 5.88 (m, H-5, 1 H), 5.38 (t, J )
5.8 Hz, H-10, 1 H), 5.29 (t, J ) 7.2 Hz, H-2, 1 H), 5.16
(d, J ) 9.5 Hz, H-6, 1 H), 5.14 (dd, J ) 7.0, 3.7 Hz, H-12,
1 H), 4.30 (t, J ) 7.4 Hz, H-14, 1 H), 3.72 (s, 4′-OMe, 3
H), 3.64 (s, 1′-OMe, 3 H), 3.54 (bs, mtpa-OMe, 3 H), 3.50
(bs, mtpa-OMe, 3 H), 3.28 (dd, J ) 15.4, 7.1 Hz, Ha-2, 1
H), 3.20 (dd, J ) 15.4, 6.7 Hz, Hb-2, 1 H), 2.55 (m, Ha-
13, 1 H), 2.41 (dd, J ) 13.4, 7.4 Hz, Ha-4, 1 H), 2.26 (s,
6′-Me, 3 H), 1.74 (s, H-19, 3 H), 1.69 (s, H-20, 3 H), 1.37
(s, H-18, 3 H), 1.23 (s, H-16 and H-17, 6 H).
(S)-MTP A-4a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) as eluent: 1H-
NMR δ 7.53 (m, mtpa-ArH, 2 H), 7.40 (m, mtpa-ArH, 3
H), 6.55 and 6.52 (AB, J ) 3.3 Hz, H-5′ and H-3′, 2 H),
5.27 (t, J ) 7.1 Hz, H-2, 1 H), 3.72 (s, 4′-OMe, 3 H),
3.70 (bs, H-12, 1 H), 3.67 (s, 1′-OMe, 3 H), 3.53 (bs,
mtpa-OMe, 3 H), 3.34 (d, J ) 7.1 Hz, H-1, 2 H), 3.00 (d,
J ) 14.8 Hz, Ha-4, 1 H), 2.81 (d, J ) 15.2 Hz, Ha-14, 1
H), 2.60 (d, J ) 15.2 Hz, Hb-14, 1 H), 2.40 (d, J ) 14.8
Hz, Hb-4, 1 H), 2.26 (s, 6′-Me, 3 H), 1.64 (s, H-20, 3 H),
1.60 (s, H-17, 3 H), 1.52 (s, H-16, 3 H), 0.79 (s, H-19, 3
H), 0.63 (s, H-18, 3 H).
Ep icysta lger olo 4b: 1H-NMR δ 6.55 and 6.54 (AB,
J ) 3.0 Hz, H-5′ and H-3′, 2 H), 5.32 (t, J ) 6.9 Hz,
H-2, 1 H), 4.20 (s, H-12, 1 H), 3.74 (s, 4′-OMe, 3 H), 3.68
(s, 1′-OMe, 3 H), 3.36 (d, J ) 6.9 Hz, H-1, 2 H), 2.87
and 2.69 (AB, J ) 14.3 Hz, H-4, 2 H), 2.59 and 2.47
(AB, J ) 14.9 Hz, H-14, 2 H), 2.27 (s, 6′-Me, 3 H), 2.04
and 1.80 (AB, J ) 17.4 Hz, H-6, 2 H), 1.63 (s, H-20, 3
H), 1.27 (s, H-17, 3 H), 1.17 (s, H-16, 3 H), 0.82 (s, H-19,
3 H), 0.77 (s, H-18, 3 H).
(S)-MTP A-3. Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) as eluent: 1H-
NMR δ 7.48 (m, mtpa-ArH, 4 H), 7.40 (m, mtpa-ArH, 3
H), 7.36 (m, mtpa-ArH, 3 H), 6.55 and 6.48 (AB, J )
3.0 Hz, 3′-H and 5′-H, 2 H), 5.86 (m, H-5, 1 H), 5.41 (t,
J ) 6.8 Hz, H-10, 1 H), 5.38 (t, J ) 7.1 Hz, H-2, 1 H),
5.21 (dd, J ) 6.9, 3.9 Hz, H-12, 1 H), 5.02 (d, J ) 9.2
Hz, H-6, 1 H), 4.33 (t, J ) 7.6 Hz, H-14, 1 H), 3.71 (s,
4′-OMe, 3 H), 3.65 (s, 1′-OMe, 3 H), 3.53 (bs, mtpa-OMe,
3 H), 3.47 (bs, mtpa-OMe, 3 H), 3.34 (dd, J ) 15.6, 7.3
Hz, Ha-2, 1 H), 3.29 (dd, J ) 15.6, 7.1 Hz, Hb-2, 1 H),
2.57 (m, Ha-13, 1 H), 2.47 (dd, J ) 13.8, 7.9 Hz, Ha-4, 1
H), 2.26 (s, 6′-Me, 3 H), 1.77 (s, H-20, 3 H), 1.75 (s, H-18,
3 H), 1.51 (s, H-19, 3 H), 1.23 (s, H-17, 3 H), 1.13 (s,
H-16, 3 H).
(R)-MTP A-4b. Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) as eluent: 1H-
NMR δ 7.53 (m, mtpa-ArH, 2 H), 7.40 (m, mtpa-ArH, 3

1092 J ournal of Natural Products, 1997, Vol. 60, No. 11
Amico et al.
H), 6.55 and 6.51 (AB, J ) 3.0 Hz, H-5′ and H-3′, 2 H),
5.30 (t, J ) 7.4 Hz, H-2, 1 H), 3.86 (bs, H-12, 1 H), 3.72
(s, 4′-OMe, 3 H), 3.66 (s, 1′-OMe, 3 H), 3.52 (bs, mtpa-
OMe, 3 H), 3.33 (d, J ) 7.4 Hz, H-1, 2 H), 3.04 (d, J )
14.6 Hz, Ha-4, 1 H), 2.81 (d, J ) 15.3 Hz, Ha-14, 1 H),
2.42 (d, J ) 15.3 Hz, Hb-14, 1 H), 2.41 (d, J ) 14.6 Hz,
Hb-4, 1 H), 2.27 (s, 6′-Me, 3 H), 1.67 (s, H-20, 3 H), 1.52
(s, H-17, 3 H), 1.35 (s, H-16, 3 H), 0.77 (s, H-19, 3 H),
0.67 (s, H-18, 3 H).
(S)-MTP A-6a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) followed by Et2O/
n-hexane (8:92) as eluent: 1H-NMR δ 7.52 (m, mtpa-
ArH, 2 H), 7.41 (m, mtpa-ArH, 3 H), 6.57 (bs, H-3′ and
H-5′, 2 H), 5.38 (t, J ) 7.2 Hz, H-2, 1 H), 5.26 (dd, J )
7.3, 6.9 Hz, H-14, 1 H), 3.76 (s, 4′-OMe, 3 H), 3.68 (s,
1′-OMe, 3 H), 3.54 (bs, mtpa-OMe, 3 H), 3.39 (d, J )
7.2 Hz, H-1, 2 H), 3.20 (dd, J ) 13.3, 6.9 Hz, Ha-13, 1
H), 3.10 (s, H-6, 1 H), 2.95 (s, H-4, 2 H), 2.27 (s, 6′-Me,
3 H), 2.02 (dd, J ) 13.3, 7.3 Hz, Hb-13, 1 H), 1.73 (s,
H-20, 3 H), 1.15 (s, H-16, 3 H), 0.92 (s, H-17 and H-19,
6 H), 0.83 (s, H-18, 3 H); 13C-NMR δ 207.5 (s, 5), 165.8
(s, mtpa-CO), 155.6 (s, 4′), 150.4 (s, 1′), 134.4 (s), 132.2
(s), 131.8 (s), 129.6 (s), 129.6 (d, mtpa-Ar), 128.5 (d,
mtpa-Ar), 128.4 (d, 2), 127.4 (d, mtpa-Ar), 123.1 (q,
mtpa-CF3, J C-F ) 288.5 Hz), 114.2 (d, 5′), 112.5 (d, 3′),
84.4 (q, mtpa-C-OMe, J C-F ) 26.8 Hz), 82.1 (s, 12), 82.0
(d, 14), 80.2 (s, 15), 60.5 (d, 6), 60.4 (q, 1′-OMe), 55.8 (t,
4), 55.4 (q, 4′-OMe, mtpa-OMe), 52.6 (s, 11), 46.2 (s, 7),
40.9 (t, 8), 35.7 (t, 10), 33.5 (t, 13), 28.7 (t, 1), 27.7 (q,
16), 24.2 (t, 9), 23.1 (q, 17), 18.8 (q, 18), 17.1 (q, 19),
16.8 (q, 20), 16.5 (q, 6′-Me).
(S)-MTP A-4b. Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (3:2) as eluent: 1H-NMR
δ 7.53 (m, mtpa-ArH, 2 H), 7.40 (m, mtpa-ArH, 3 H),
6.55 and 6.49 (AB, J ) 3.0 Hz, H-5′ and H-3′, 2 H), 5.28
(t, J ) 7.3 Hz, H-2, 1 H), 3.88 (bs, H-12, 1 H), 3.73 (s,
4′-OMe, 3 H), 3.69 (bs, mtpa-OMe, 3 H), 3.66 (s, 1′-OMe,
3 H), 3.32 (d, J ) 7.2 Hz, H-1, 2 H), 3.08 (d, J ) 14.8
Hz, Ha-4, 1 H), 2.85 (d, J ) 15.2 Hz, Ha-14, 1 H), 2.45
(d, J ) 15.2 Hz, Hb-14, 1 H), 2.44 (d, J ) 14.8 Hz, Hb-4,
1 H), 2.26 (s, 6′-Me, 3 H), 1.72 (s, H-20, 3 H), 1.58 (s,
H-17, 3 H), 1.44 (s, H-16, 3 H), 0.62 (s, H-19, 3 H), 0.28
(s, H-18, 3 H).
Tr ea tm en t of 5 w ith Ba se To Give 4. A solution
of 5 (300 mg) in EtOH (3 mL) was mixed with 3 mL of
6 N NaOH and stirred for 5 h at room temperature;
usual workup, followed by PLC (Silica gel, Et2O/n-
hexane, 35:65), gave 4 (10 mg, 3%), identical in all
respect to an authentic sample ([R]D + 74.5 (c ) 1.2,
EtOH), lit.11 [R]D +75).
Meth yla tion of 6 To Give 6a . A sample of 6 (200
mg) was treated as described above for compound 1a .
Usual workup followed by PLC (silica gel, Et2O/n-
hexane, 35:65) afforded 6a (30 mg): 1H-NMR δ 6.56 (bs,
H-3′ and H-5′, 2 H), 5.36 (t, J ) 7.1 Hz, H-2, 1 H), 3.94
(dd, J ) 8.8, 6.5 Hz, H-14, 1 H), 3.75 (s, 4′-OMe, 3 H),
3.68 (s, 1′-OMe, 3 H); 13C-NMR δ 207.9 (s), 155.5 (s),
150.3 (s), 134.5 (s), 131.8 (s), 129.8 (s), 128.2 (d), 114.0
(d), 112.6 (d), 81.3 (s), 79.9 (s), 78.3 (d), 60.6 (d), 60.5
(q), 55.9 (d), 55.4 (q), 52.6 (s), 46.0 (s), 28.6 (t), 27.5 (q),
24.2 (t), 22.3 (q), 19.0 (q), 17.0 (q), 16.7 (q), 16.4 (q).
Meth yla tion of 7 To Give 7a . A sample of 7 (100
mg) was treated as described above for compound 1a .
Usual workup followed by PLC (silica gel, Et2O/n-
hexane, 15:85) afforded 7a (45 mg): 1H-NMR δ 6.71 and
6.56 (AB, J ) 3.1 Hz, H-5′ and H-3′, 2 H), 4.95 (s, Ha-4,
1 H), 4.81 (bs, Hb-4, 1 H), 3.75 (s, 1′-OMe, 3 H), 3.69 (s,
4′-OMe, 3 H), 3.39 (dd, J ) 9.1, 3.2 Hz, H-2, 1 H), 3.05
(dd, J ) 13.0, 9.6 Hz, Ha-1, 1 H), 2.99 (s, H-6, 1 H), 2.65
(dd, J ) 13.0, 3.7 Hz, Hb-1, 1 H), 2.57 (t, J ) 5.0 Hz, 1
H), 2.42 (dd, J ) 12.5, 6.3 Hz, Ha-13, 1 H), 2.23 (s, 6′-
Me, 3 H), 1.72 (s, H-20, 3 H), 0.95 (s, H-16, 3 H), 0.89
(s, H-17, 3 H), 0.86 (s, H-19, 3 H), 0.84 (s, H-18, 3 H);
13C-NMR δ 207.0 (s), 155.0 (s), 151.1 (s), 141.8 (s), 134.6
(s), 132.1 (s), 114.8 (t), 114.6 (d), 81.9 (s), 79.5 (s), 77.3
(d), 64.5 (d), 62.1 (d), 60.3 (q), 55.6 (q), 52.5 (s), 44.6 (s),
40.9 (t), 36.0 (t), 34.6 (t), 30.7 (t), 27.1 (q), 24.3 (t), 21.9
(q), 20.7 (q), 18.9 (q), 17.0 (q), 16.3 (q).
(R)-MTP A-7a . A sample of 7a (15 mg) was treated
according to general procedure, with purification using
a Florisil sep-pak cartridge (CH2Cl2/n-hexane, 2:3) to
give (R)-MTPA-7a (12 mg): 1H-NMR δ 7.49 (m, mtpa-
ArH, 2 H), 7.40 (m, mtpa-ArH, 3 H), 6.55 and 6.51 (AB,
J ) 2.2 Hz, H-5′ and H-3′, 2 H), 4.93 (bs, Ha-4, 1 H),
4.81 (bs, Hb-4, 1 H), 4.67 (t, J ) 6.2 Hz, H-14, 1 H), 3.70
(s, 1′-OMe, 3 H), 3.66 (s, 4′-OMe, 3 H), 3.52 (s, mtpa-
OMe, 3 H), 3.48 (t, J ) 7.0 Hz, H-2, 1 H), 3.11 (s, H-6,
1 H), 3.06 (dd, J ) 13.3, 7.0 Hz, Ha-1, 1 H), 2.75 (dd, J
) 14.1, 6.5 Hz, Ha-13, 1 H), 2.66 (dd, J ) 13.5, 6.5 Hz,
Hb-1, 1 H), 2.22 (s, 6′-Me, 3 H), 1.84 (dd, J ) 14.2, 6.0,
Hb-13, 1 H), 1.65 (s, H-20, 3 H), 1.02 (s, H-16, 3 H), 0.94
(s, H-17, 3 H), 0.87 (s, H-19, 3 H), 0.68 (s, H-18, 3 H).
(R)-MTP A-6a . A sample of 6a (25 mg) was treated
according to the general procedure, with purification
using two Florisil sep-pak cartridges (CH2Cl2/n-hexane,
3:2, followed by Et2O/n-hexane, 8:92) to give (R)-MTPA-
6a (19 mg): 1H-NMR δ 7.52 (m, mtpa-ArH, 2 H), 7.42
(m, mtpa-ArH, 3 H), 6.57 (bs, H-3′ and H-5′, 2 H), 5.38
(t, J ) 7.1 Hz, H-2, 1 H), 5.19 (dd, J ) 6.9, 6.8 Hz, H-14,
1 H), 3.76 (s, 4′-OMe, 3 H), 3.68 (s, 1′-OMe, 3 H), 3.54
(bs, mtpa-OMe, 3 H), 3.39 (d, J ) 7.1 Hz, H-1, 2 H),
3.20 (dd, J ) 13.5, 6.8 Hz, Ha-13, 1 H), 3.10 (s, H-6, 1
H), 2.95 (s, H-4, 2 H), 2.27 (s, 6′-Me, 3 H), 1.90 (dd, J )
13.5, 6.9 Hz, Hb-13, 1 H), 1.73 (s, H-20, 3 H), 1.18 (s,
H-16, 3 H), 1.07 (s, H-17, 3 H), 0.90 (s, H-19, 3 H), 0.74
(s, H-18, 3 H); 13C-NMR δ 207.6 (s, 5), 166.0 (s, mtpa-
CO), 155.6 (s, 4′), 150.4 (s, 1′), 134.5 (s), 132.0 (s), 131.9
(s), 129.7 (s), 129.6 (d, mtpa), 128.4 (d, 2 and mtpa),
127.5 (d, mtpa), 123.2 (q, mtpa-CF3, J C-F ) 288.5 Hz),
(S)-MTP A-7a . Preparation was according to the
general procedure, with purification using a Florisil sep-
pak cartridge, CH2Cl2/n-hexane (2:3) as eluent to afford
11 mg of 7a : 1H-NMR δ 7.49 (m, mtpa-ArH, 2 H), 7.40
(m, mtpa-ArH, 3 H), 6.55 and 6.54 (AB, J ) 2.0 Hz, H-3′
and H-5′, 2 H), 4.93 (s, Ha-4, 1 H), 4.81 (s, Hb-4, 1 H),4.77
(t, J ) 6.5, H-14, 1 H), 3.71 (s, 1′-OMe, 3 H), 3.67 (s,
4′-OMe, 3 H), 3.51 (s, mtpa-OMe, 3 H), 3.48 (t, J ) 7.0
Hz, H-2, 1 H), 3.13 (s, H-6, 1 H), 3.06 (dd, J ) 13.5, 7.0
114.1 (d, 5′), 112.5 (d, 3′), 84.7 (q, mtpa-C-OMe, J C-F
)
26.8 Hz), 82.5 (d, 14), 82.2 (s, 12), 80.0 (s, 15), 60.5 (q,
1′-OMe), 60.45 (d, 6), 55.7 (t, 4), 55.4 (q, 4′-OMe, mtpa-
OMe), 52.6 (s, 11), 46.2 (s, 7), 40.7 (t, 8), 35.7 (t, 10),
33.4 (t, 13), 28.6 (t, 1), 27.5 (q, 16), 24.2 (t, 9), 23.3 (q,
17), 18.6 (q, 18), 17.0 (q, 19), 16.7 (q, 20), 16.4 (q, 6′-
Me).
Hz, Ha
-1, 1 H), 2.75 (dd, J ) 14.0, 6.5 Hz, Ha-13, 1 H),
2.66 (dd, J ) 13.5, 7.0 Hz, Hb-1, 1 H), 2.23 (s, 6′-Me, 3

Marine Metabolites from Cystoseira spp.
J ournal of Natural Products, 1997, Vol. 60, No. 11 1093
(6) Horeau, A. Tetrahedron Lett. 1962, 965-969.
(7) (a) Green, M. M.; Axelrod, M.; Mislow, K. J . Am. Chem. Soc.
1966, 88, 861-862. (b) Fuganti, C.; Ghiringhelli, D. Gazz. Chim.
Ital. 1969, 99, 316-322.
H), 1.97 (dd, J ) 14.0, 6.2, Hb-13, 1 H), 1.65 (s, H-20, 3
H), 0.94 (s, H-16, 3 H), 0.90 (s, H-17, 3 H), 0.87 (s, H-19,
3 H), 0.79 (s, H-18, 3 H).
(8) Amico, V.; Piattelli, M.; Cunsolo, F.; Neri, P.; Ruberto, G. Gazz.
Chim. Ital. 1988, 118, 193-195.
Ack n ow led gm en t. This work was financially sup-
ported by the Consiglio Nazionale delle Ricerche (CNR,
Rome) and Ministero dell’Universita` e delle Ricerca
Scientifica e Tecnologica (MURST, 40%). We thank Mr.
Agatino Renda for skillful technical assistance and Mrs.
Concetta Rocco for spectral measurements.
(9) Amico, V.; Cunsolo, F.; Oriente, G.; Piattelli, M.; Ruberto, G. J .
Nat. Prod. 1984, 47, 947-952.
(10) Amico, V.; Neri, P.; Oriente, G.; Piattelli, M. Phytochemistry
1989, 28, 215-219.
(11) Amico, V.; Oriente, G.; Piattelli, M.; Ruberto, G. Gazz. Chim.
Ital. 1984, 114, 169-172.
(12) Amico, V.; Cunsolo, F.; Piattelli, M.; Ruberto, G. Phytochemistry
1984, 23, 2017-2020.
(13) Amico, V.; Cunsolo, F.; Piattelli, M.; Ruberto, G.; Fronczek, F.
R. Tetrahedron 1984, 40, 1721-1725.
Refer en ces a n d Notes
(1) Piattelli, M. New J . Chem. 1990, 14, 777-782.
(2) Amico, V. Phytochemistry 1995, 39, 1257-1279.
(3) Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J . Am. Chem.
Soc. 1991, 113, 4092-4096 and references cited therein.
(4) Dale, J . A.; Mosher, H. S. J . Am. Chem. Soc. 1968, 90, 3732-
3738.
(14) Amico, V.; Neri, P.; Piattelli, M.; Ruberto, G. J . Nat. Prod. 1988,
51, 191-192.
(15) Amico, V.; Neri, P.; Piattelli, M.; Recupero, M. Gazz. Chim. Ital.
1991, 121, 335-340.
(16) Amico, V.; Cunsolo, F.; Neri, P.; Piattelli, M.; Ruberto, G. J . Nat.
Prod. 1989, 52, 962-969.
(5) Dale, J . A.; Dull, D. L.; Mosher, H. S. J . Org. Chem. 1969, 34,
2543-2549.
NP9700432