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New xenicane diterpenes from the brown algae of dictyotaceae
TcwdedrmVoL46. No. 17, pp. 6125-6132 1990 PrinldinOrutBriuin
NEW XHNICANE
cmom2om $3.00+.00 63 1990 PsgmwmResr plc
DITHRPHNEI
THE BROWN ALGAEl OF WCTYOTACHE
PROM
Manuel Nor&, A.G. Gonz#ez, Patrkia Amyo,
Miguel Z&rage, Cirilo P&m,
Matias L. Ro-
driguez, Catalina Ruiz-Perez and Luis Dorta Centro de Productos Naturales Or@nicos Antonio Gonzalez. Institute Universitario Bio-orgtlnica. Universidad de La Laguna. 38206 La Iaguna. Spain.
de Qulmica
(Received in UK 2 April 1990) Summary: Two new xenicane diterpenes have been isolated from the brown algae of the Dictyotaceae family, and their structures and absolute configurations have been elucidated on the basis of their spectral and X-ray diffraction analyses.
Brown algae of the Dictyotaceae different carbon
frameworks’.
most intriguing
family are characterized
Among the diterpenes
groups are the xenicanes,
by the production
of diterpenoids
found in this family of seaweeds, one of the
some of them with a significant
cytotoxic activity2, which
have been isolated not only from alga but also from soft corals and gorgonians’“. compounds
are characterized
in other natural
with
as being composed of a cyclononane
skeleton,
Structurally
these
which is rarely found
products.
In this paper, we wish to describe the structures of two new xenicane derivatives isolated during the comparative
study of the brown algae communities
have collected
at Valparaiso
from the Atlantic
(Chile) the brown alga Glossophora kuntii from which we have iso-
lated the xenicane derivative 2 Gn the other hand, the diterpene Dictyota sp collected Compound
1, (a,)=
Its molecular Absorptions
at Tenerife
was established
in the I.R. spectrum
hydroxyl, acetate the UV spectrum
1 was isolated from the brown alga
in the Canary Islands.
-80.P (c, 0.29, CHClJ,
formula
and Pacific shores. Thus, we
was isolated as a crystalline
as C,I-I,,O,
compound
on the basis of its HRMS
(m.p. 53-54 Qc). (m/z
378.2397).
at 3435, 1730 and 1760 cm” were due to the presence
and a,Runsaturated
carbonyl groups, this last one being confirmed
at 225 run. Moreover,
the NMR spectra established
ymethyl group (*)C: d, 63.8; ‘H: d, 4.63 and 4.73); a trisubstituted
the presence
by a band in of an acetox-
epoxy ring (UC: d, 60.09 and 63.32;
‘H: d, 2.88 and 1.5). a secondary hydroxyl group (UC: d, 68.21; ‘H: d, 4.16) and a disubstituted unsaturated together
of an
a&
aldehyde group (UC: b, 189.8, 152.41, 100.67, ‘H: d, 6.82 and 9.32). The NMR spectra,
with the presence
of the fragmentations
revealed that the 6 methyl-5-hepten-Zyl
at m/z
109 and 69 in the MS spectrum,
group, the typical side chain in the Dictyotaceae
was present. 6125
also
diterpenes.
6126
M. NORTE er al.
The assignments bidimensional, published
of the chemical shifts of home- and heteronuclear
for fukurinolal’
works as a metaholite compound
of compound
from Gloasophora manner.
hmti
Its spectral
xenicane skeleton, “C:
of Dilophus
okamurai
2 (c.Q=
collected
properties
1 (Table I) were made by using mono- and
NMR experiments.
or hydroxyacetyldictyolal‘
1 was the 6.7-epoxy derivative
The structure
compound
Comparison
d; * _
and Didyota
at Wparaiso
(Chile),
I) confirmed
in which the presence
of a hemiacetal
isolated
C,%O,
that compound
those of isodictyohemicetal
4, metabolite
difference
of the C(6) and C(7) olefinic
presence of signals from a trisubstituted
respectively,
indicated
that
(m/z 320.3241), isolated
was deduced
in essentially
2 also possesses
moiety was evident:
d, 100.3 and 71.1; ‘H: d, 4.39, 5.67. In fact the comparison
was the absence
in two independent
of 3.
t6.81* (c, 0.088. CHClJ,
(Table
of these data with those
3, which was published
a 6,7-epoxy
IR: 35OOcrrP; NMR:
of the WNMR
from D. dUotm&,
the same
signals of 2 with
showed that the obvious
signals at b 134.6 and
124.7, and the
epoxy ring at b 60.4 and 63.9. Thus we can conclude
that
2 is the 6,7-epoxy isodictyohemicetal. The structures
of these
compounds
crystallized in the orthorhombic the asymmetric
AED four-circle
by X-ray diffraction
space group P2,2,2, with one molecule
unit. Cell constants
unique diffraction
were confirmed
Compound
1
C,H,O,
in
of composition
were a = 9.423( 1). b = 10.236(l) and c = 22.675(l)
maxima with 3 s 28 s 1289 were collected diffractometer
analysis.
using graphite
monochromated
on a computer-controlled CuKa
(154178
A> radiation
A All Siemens and a
New
Tabla
c
I:
6Ml SpctFa1
2
1
6127
xenicane diterpenes
of CqJounds I a?& 2
data
H
1
2
-
-
1
120.67
146.6
2
38.78
44.9
2
3.25
dd.
3
49.12
53.8
3
1.80
bn
4
68.21
27.9
4
4.16
da,
?.1;3.5
5
47.66
39.8
5 5
1.06 9.42
&i, ad,
14.137.1 14.113.5
6
60.01
60.4
6
10;8.5
2.58
ba
-_.
7
62.32
63.9
7
2.90
d,
3-03
&i,
8
26.65
26.1
8 8
2.91 2.45
dd, 9.1;18 &id, 3.5;10;16
2.65 2.33
&id, d&i,
9
152.41
116.8
9
6.82
dd,
5.64
c&i, 1.6;8.4
10
32.12
31.9
10
2.41
m
1.88
m
11
38.38
38.1
11
1.15
m
1.16
m
12
26.13
26.6
12
1.79
m
1.92
m
13
124.56
124.4
13
5.07
bt,
5.03
bt,
14
131.58
131.4
14
15
17.85
17.6
15
1.61
16
25.77
25.5
16
1.51
17
17.74
17.3
18
63.80
100.2
19
189.80
71.1
17 18 18 19
1.00 4.61 4.71 9.42
20
20.3
17.0
20
1.81
10
9.1;3.5
7
1.9~8.4;10.8 1.9;10.8;16.2
7
1.65 1.58 d. 7 t. 10 dd, 8.5;lO d, 1.9
0.98 5.67
be
4.39
ba
1.40
170.84
Ic=o) Ile(OAc)
1.93
21.05
a) AsaQmnmta
made bg hetinmuctoar
w:8 scan. After correction 1912 reflections A phasing
COSY. b) assigrsrrnts and kzmJ?ru&?ar CosY
for Lorentz, polarization
surveyed were considered
observed
made
and background
by hmomclear
(I 2 3o(I)).
model was arrived at using a multisolution
was anisotropically
refined
from International
Tables
by block-diagonal
weighted
least squares
for X-Ray Crystallography9.
density map. Art appropriate
decoupti~
effects, only 1897 (99%) of the
tangent
formula
magic integers’. The best model from this approach showed all non-hydrogen
electron
1.9;10.8
was carried out”. A final weighted anisotropic
contribution
for H atoms) gave for the correct enantiomer
factors were taken
were located on a difference
weighting scheme to normalize
using
atoms. The structure
(on F)a. Scattering
All H-atoms
approach
full-matrix
refinement
the discrepancy
vs.
and
(fixed isotropic
indices R= 0.055 (Rw=
0.060). The absolute configuration
of 1 was determined
by comparison of 30 Bijvoet pairs with Fo
which are in the range 5.c Fc < 50. and 0.2 < (sin6/1)
>Sa(Fo),
< 0.4 A-t. The averaged Bijvoet differences
6128
M. Nome et al.
0.0323( 0.2973( -0.1367( 0.0452( 0.4182( 0.0239( 0.0541( -0.0818( -0.0900( -0.1406( -0.0585( -0.1021( -0.0035( 0.0045( -0.1105( -0.2712( -0.3140( -0.4707( -0.5280( -0.6836( -0.4440( -0.0343( 0.1818( 0.0208( 0.0893( 0.4061( 0.5069(
01 02 03 04 05 Cl c2 C3 c4 C5
C6 Cl CB c9
Cl0 Cl1 Cl2 Cl3 Cl4 Cl5 Cl6 Cl7 Cl8 Cl9 c20 c21 c22
lbbh
cooniimtiw
Atic
II.-
01 02 02 03 03 04 OS Cl Cl Cl c2 c2 c3 c3 Cl8 C6 c9 c2 c2 Cl Cl c3 c2 c2 c4 04 c3 04 c4 03 c5 c5 03 03
1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 11 1) 1) 1) 2) 2) 1) 1) 1) 1) 1) 1)
for tzoqmnd - Cl9 -
Cl8 c21 C6 c7 c4 c21 c2 c9 Cl9 c3 Cl8 c4 Cl0
-
02 03 Cl Cl Cl c2 c2 c2 c3 c3 c3 c4 c4 c4 c5 C6 C6 C6 C6 C6
1
-
-
ebl.% III.- Intemtoric
(Al
5) 4) 4) 4) 5) 4) 6) 4) 5)
:*:9: 1:529 1.548 1.549
; ( ( (
:; 4) 4) 4)
Cl9 c9 Cl8 c3 Cl8 Cl0 c4 Cl0 c3 c5 c5 C6 c5 c20 c7 c20 c7
0.7595(
0.8599( 1.0218( 0.9929( 0.9383( 0.8482( 0.8921( 0.9075( 0.9739( 1.0148( 1.0094( 0.9615( 0.9247( 0.8634( 0.8672( 0.8629( 0.8154( 0.8161( 0.8015( 0.8060( 0.7792( 0.8854( 0.8735( 0.7836( l.O35J( 0.8963( 0.8779(
1) 1) 1) 1) 1) 1) 1) 1) 1) 1) I) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1)
and squiaulmt iclotn@o ‘8. in I 1.
( ( ( ( ( ( ( ( (
Cl9
1) lb li 1) 3) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 2) 1) 1) 1) 1) 1) 1) 1)
635(10) 662( 7) 772( 9) 580( 7) 1273(17) 562( 9) 476( 8) 452( 7) 499( 8) 589( 9) 567( 9) 632(10) 750(13) 688(12) 481( 8) 552( 9) 674(11) 656(11) 779(13) 1348(29) 1081(20) 615(10) 561( 9) 705(12) 657(11) 586(10) 816(14)
factore (A2 I 103)
t.aqmm-
vith e.e.d.
1.205 1.460 1.319 1.468 1.444 1.438 1.172 1.528 1.344
- c21 - c7
-
0.0621( 0.03421 -0.199oi 0.2087( 0.0914( -0.0678( 0.0419( 0.1245( 0.1587( 0.0484( -0.0780( -0.1663( -0.2486( -0.1934( 0.2438( 0.2685( 0.3659( 0.3961( 0.5094( 0.5337( 0.6218( 0.3703( 0.1244( -0.0423( -0.0806( 0.0257( -0.0787(
119.2 60.7 114.6 121.1 124.1 111.9 112.8 113.9 115.7 112.2 112.7 109.1 115.8 110.8
c4 c5 C6 C6 c7 C8 Cl0 Cl0 Cl1 Cl2 Cl3 Cl4 Cl4 c21 ( I i ( ( ( ( ( ( ( ( ( ( f
3) 21 3j 3) 3) 2) 2) 2) 2) 2) 2) 2) 5) 2)
114.9
i
3j
116.7 117.0 116.3 111.9 58.8
( ( ( ( (
3) 3) 3) 3) 2)
dibmoee
-
c5 C6 c7 c20 C8 c9 Cl1 Cl7 Cl2 Cl3 Cl4 Cl5 Cl6 c22
c7 03 C6 03 c7 Cl c3 c3 Cl1 Cl0 Cl1 Cl2 Cl3 Cl3 Cl5 02 01 ::
-
02
- c21
(A) and angEe
1.538 1.512 1.472 1.513 1.506 1.502 1.539 1.537 1.522 1.509 1.320 1.491 1.484 1.490 C6 c7 c7 c7 C8 c9 Cl0 Cl0 Cl0 Cl1 Cl2 Cl3 Cl4 Cl4 Cl4 Cl8 Cl9 c21
-
( ( ( ( ( ( ( ( ( ( ( ( ( (
4) 5) 5) 5) 5) 6) 4) 4) 5) 5) 6) 8) 7) 5)
c20 C6 C8 C8 c9 C8 Cl7 Cl1 Cl7 Cl2 Cl3 Cl4 Cl6 Cl5 Cl6 c2 Cl OS c22
122.2 60.4 125.5 122.3 109.4 127.2 115.1 109.8 109.8 114.4 112.7 125.2 123.2 122.1 114.7 107.2 126.8 125.3 123.1
- c22
111.6
( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (
(Q) of t_xqwmd 1 vith o.6.d.
3) 2) 3) 3) 3) 3) 2) 2) 2) 3) 3) 4) 5) 4) 5) 2) 4) 3) 4) 3)
‘8.
in I ).
6129
New xenicane diterpenes
are 0.274 for the correct enantiomer isotropic thermal parameters
vs 0.348 for the wrong one. The final positional
and equivalent
are given in Table II. A drawing of the final X-ray mode1 less hydro-
gens is given in Fig.1. Bond lengths and bond angles are listed in Table III.
Molecules interact
in the crystal through a hydrogen bond, with hydroxyl group O(4) as donor and
the O(5) of a molecule
related by x-1/2, -y+1/2,
-z+2 as acceptor. Geometrical
parameters
of this
hydrogen bond are OmmmO: 2.838(S), H nmm0: 1.91 (1) and G-HmmmO: angle 155.5 (2)*. The chains formed by these interactions 3.3SP between Compound
are depicted in Fig.1. No other intermolecular
non-hydrogen
2 (C,H,O,)
16.687(l), b= 6.260(l),
crystallized in the monoclinic c= 21.230(l)
The structure
Blocked full-matrix
least-squares
positions
= 1.084
with C-H
thermal parameter. mal parameters
shorter than
atoms exist.
2h \ 1289 were collected in the manner judged observed.
interactions
space group C(2). The cell constants were a=
P, 8= 120.4(2)Q. All unique diffraction
maxima with also 3 \
described for 1 and 1298 (83%) of the 1554 reflections were
was solved using direct methodsU and subsequent refinement and refined
Fourier
on F. Some H atoms were introduced riding on their carrier
In the final cycles of the refinement
for the non-H atoms, positional
parameters
positional
at calculated
atoms with a general and individual
analysis.
isotropic
anisotropic
ther-
for H-atoms, their isotropic thermal pa-
rameter and an overall scale factor were varied. For 2 the final R value was 0.043, Rw= 0.050, w = l/[c~*(Fo) t O.OOll(Fo)2] The refinement lute configuration
was fured by comparison
calculation
were performed
with SHELX76”.
of 65 Bijvoet pairs with Fo s Sa(Fo), which are in the
ranges 5. 5 Fo I 50. and .2 5 sine/A zs .4A-LI*. The averaged Bijvoet differences correct enantiomer
The abso-
vs 0.491 for the wrong one. Fig, 2 shows the molecular
are 0.427 for the
configuration
and the
. 6130
M. NORTE etal.
01
0.1792( 0.4997( 0.5240( 0.4159( 0.3776( 0.2821( 0.2100( 0.1540( 0.2149( 0.2530( 0.3463( 0.4077( 0.2898( 0.2126( 0.2211( 0.1489( 0.0768( 0.0100( 0.0549( 0.2658( 0.4610( 0.4789( 0.2600(
02 03 Cl c2 C3 CI CS C6 C7 C8 c9 Cl0 Cl1 Cl2 Cl3 Cl4 Cl5 Cl6 Cl7 Cl8 Cl9 c20
!lkzbts V.-
Atamk
oooldinotes
0.2796(
2) 2) 2) 2) 2) 2) 3) 3) 2) 3) 3) 2) 3) 3) 4) 4) 4) 4) 5) 4) 3) 3) 4)
(A)
l)
' 0.4002( 0.3110( 0.3964( 0.3656( 0.3314( 0.2569( 0.2530( 0.2695( 0.3688( 0.3861( 0.4462( 0.4156( 0.1868( 0.1269( 0.0591( 0.0047( -0.0569( -0.1091( -0.0662( 0.1562( 0.3271( 0.3372( 0.4190(
0.3183( 8) 0.5645( 8) 0.1963( 9) 0.4127( 9) 0.3968( 9) 0.5610(10) 0.4845(10) 0.4344( 9) 0.2165( 9) 0.1559(10) 0.0914( 9) 0.4079(10) 0.2682(11) 0.2345(15) 0.0644(13) 0.1370(12) -0.0293(14) 0.3572(15) 0.6330(11) 0.4980(10) 0.1285(10) 0.6207(10)
and
sqvimtent
isotropic
2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 3) 3) 3) 4) 5) 3) 2) 3) 3)
59( 1) 64( 63( 47( 45(
2) 1) 2) 2)
::I 55( 46( 47( 53( 51( 54( 59( 85( 78( 76( 104( 121(
:; 2) 2) 2) 2) 2) 2) 2) 3) 3) 3) 3) 4)
::I :1 60( 2) 61( 2)
tkmqxtm-
faotom
(A=2 10’)
for c?mpomd 2 uith 8.8.d.'8. in ( 1. -
01 01 02 02 03 Cl Cl Cl c2 c2 c3 c3 c4 C6 Cl8 c9 c2 c2 Cl Cl c3 c2 c2 c4 C3 c4 01 CS c5 01 01 c7 lhble
N.-
-
C6 c7 Cl8 Cl9 Cl8 c2 c9 Cl9 c3 Cl8 c4 Cl0 c5
01 02 Cl Cl Cl c2 c2 c2 c3 c3 c3 c4 c5 C6 C6 C6 C6 C6 C6
-
1.476 1.452 1.413 1.439 1.430 1.525 1.318 1.499 1.575 1.530 1.536 1.563 1.550 c7 Cl9 Cl9 Cl9 c9 Cl8 c3 Cl6 Cl0 c4 Cl0 c5 C6 c5 c20 c7 c20 c7 c20
( 9) ( 9) (10) (11) ( 8) ( 9) (10) (12) ( 6) (10) (11) (10) (11)
c5 C6 C6 c7 C8 Cl0 Cl0 Cl1 Cl2 C13‘ Cl4 Cl4
60.0( 4) 109.2( 7) 124.0( 6) 106.1( 5) 129.6( 6) 98.9( 5) 113.1( 6) :::.:I :; 112:2( 5) 112.1( 5) 115.7( 6) 111.9( 6) 116.5( 6) 116.7( 6) 116.4( 5) lll.O( 5) 59.2( 4) 123.2( 5)
IntinZtani4 di8tztnc88IA) and an&88
-
01
C6 01 c7 Cl c3 c3 Cl1 Cl0 Cl1 Cl2 Cl3 Cl3 Cl5 03 02 02 02
C6 c7 c20 ca c9 Cl1 Cl7 Cl2 Cl3 Cl4 Cl5 Cl6
-
c7 c7 c7 C8 c9 Cl0 Cl0 Cl0 Cl1 Cl2 Cl3 Cl4 Cl4 Cl4 ClE Cl8 Cl8 Cl9
1.504 1.465 1.510 1.511 1.498 1.542 1.540 1.532 1.512 1.319 1.510 1.473
-
( 7) (10) (10) ( 7) (11) ( 9) (11) (13) (13) ( 9) (12) (14)
C6 C8 C8 c9 C8 Cl7 Cl1 Cl7 Cl2 Cl3 Cl4 Cl6 Cl5 Cl6 c2 C2 03 Cl
(9) of oaparod 2 vith
60.6( 125.1( 121.8( 109.1( 126.3( 113.4( 109.2( llO.l( 114.5( 112.6( 125.8( 124.3( 120.7( 115.0( 106.8( 106.8( 110.9( 106.0(
4) 6) 5) 5) 6) 5) 5) 5) 7) 7) 9) 9) 9) 8) 6) 6) 6) 6)
8.8.d.'8. in ( )
6131
New xenicane dimpenes atomic numbering,
together
with the crystal packing along the a axis. In Tables IV and V bond
lengths and angles, and final positional
and equivalent
isotropic thermal parameters
respectively are
reported. They compare well with 1 and those observed in other related marine diterpenes”.
Bond
distances
Four
and angles are normal.
The five-membered
ring shows an envelope
of the five ring atoms are almost coplanar ( as defined by the C( 18)-0(2)X(
conformation.
19)X( 1) dihedral angle
of 4.6(8)O), while the fifth atom C(2) lies 0.431A above this plane.
Fig. %.- Perspsctiw oiau of the structum of d, ek.n&g diagmm. The crystalline
lar distances
ldmtling and packing
cohesion is ensured by a hydrogen bond between the hydroxyl group O(3) as donor
and the O(1) of the epoxide of a molecule H0(3)m~O(l)
akmic
related
by x + 12, y + l/2,
a, as acceptor.
The
bond length is 2.819(7)A and the angle of this bond is 159.1(l)Q. Other intermolecuare in the normally
expected range for nonbonded
contacts.
The interest of different marine chemistry research groups in this type of compounds not only to their pharmacological
activity but also to their structural
1 and 2, we can infer that, in solution, the preferred conformation
has been due
features. Thus, for compounds
of the nine-membered
ring is that
in which the dihedral angles between the carbon protons C(2) and C(3); C(3) and C(10) for 1 and 2, together with those between this conformation
C(3) and C(4) for 1 and between C(2) and C(18) for 2 are 909. In
can be explained,
as advanced by Matsumoto6, the deshielding
the NMR chemical shifts in compound
1 for the methyl group C(20).
On the other hand, the absolute configuration ing a xenicane advanced
skeleton,
conclusion
effect observed in
of some marine diterpenes
from brown algae possess-
has recently been published U. In our case, the results also confirmed
that the absolute
con@ration
algae are opposite to that of xenicin, isolated
of the xenicane
from soft cotalP.
diterpenes
the
from Dictyotaceae
6132
M. NORTEet al.
EXPERIMENIXL
PART
Infrared spectra were reuxded on a Perkin-EImer Mod. 257. OpticaI rota&ns wore determined for solution in chloroform with a Perkin-EImcr Mod. 241 po&rimcter. ‘H-NMR and rsCNMR spectra were recorded on a Brukcr Mod. WP-200 SY (200 MHz), chemical shifts ue reported rclatiw to Me,Si(d 0) and coupling constants are given in hertz The 2DNMR spectra were obtahmd using Bruker’s microprograms. Low and high resolution mass spectra were obtained from VG micromass 24E2F spectrophotometer. Silica gel chromatography was performed on silica gel 60 G, TLC and PLC obtained from Merck products. The tk plates were developed by spraying with 6N suIphuric acid and heating. Sephadon I&f-20 obt&ed from Pharmacia was used for gel fihration chromatography. AII solvents were puritied by standard techniques. Anhidrous sodium suIfate was used for driying solution. Collectton, atnetton and ehrematqaphk aepantfon. Dktyotn sp was coUected at -10 m deep at GtIimar (Tenerife, Canary IsIamB) in November 1987. The air-dried alga (8 kg) was extracted with acetone and diet.hyI ether and the solvents were evaporated in vacua to yield 220 gr of extract. GIosaophcua kuntii was cohectod in shallow water at Iow tide near Valparaiso (Chile) in January 1986 and treated as above to yield LX7 gr of crude extract. The chromatographic treatment of both extracts were idcntical. Fust, Bash chromatography on silica gel column &ted with mixtures of n-hexane/ethyI acetate of increasing polarity. The fractions ehrted with n-Hu/EtOAc 70% were wahincd to yield, after sohnnt evaporation, compound 1 in the crude extract of Dictyota sp and compound 2 in thcxc of G. kunti. These extracts were submitted to repeatcd chromatographius on sihca and finaUy purified by chromatography on a Scphadex LH-20 column with CHCI+MeOH:n-Hux (1:1:2) as eluent to give pure compounds 1 and 2. Compound 1: solid (m.p. 53-W C), (a,= -80.70 (c, 0.29, CHCIs). UV,: 225 run (e- 5333 ). IR: 3435, 2900, 1720, 1670, 1440, 136Oand 1020 cm”. HRMS: M* at m/z 3782397 (CaIc 378.2406). MS: m/z 378 (M*), 360, 332, 318, 109, 69. NMR spectra: see Table I. Compound 2: solid (m.p. 90-92 PC), (at,)- +6.819 (c, OSS, CHCI& UV,: 208 nm (e= 2831). IR: 3550, 2950, 1750, 1350, 1050 cm”. HRMS: M* at m/z 3202341 (CaIc. 320.2331). MS: m/z 320 (M*), 302, 284, 259, 231. 109, 69. NMR spectraz see Table 1. Acknuwtedgmmta: We acknowIedga SnanciaI support from PIan NacionaI de lnvestigacion FAR 88-0500. PA. and M.Z. acknowIedge Institute de &opera&n Iberoamericana (ICI) and Banco Central de Espatia respectively for a fellowship. The authors acknowledge to Dr. Patricia Rivera (University of Chile) for collection of C. kuodi.
REFERENCES l.- DJ. Faulkner Nat Prod. Rep. 1987, 539 2- M.O. Ishitsuka, T. Kusnmi. H. Kakisawa. J. 09. Cbam., 1988, 53, 5010 3.- H. Belong. A. Ahoad, A. Chiaroni, C. Poupat, C. Richc, P. Potitr, J. Puss& M. Pus&, Laboute, J.L Menou. J.Nat.
Prod.
P.
1987, SO, 203
4.- M. D’Ambrosio, A. Gurricro, F. Pi&a. 2. Natnrfuacb. Sect. C, 1984, 53, 5010 5.- M. Ochi, N, Massui, H. Kotmki, I. Miura, T, Tokoroyama. Cbem. Ixtt. 1982, 1927 6.- N. Eaokii R. Ishida, T. Matsumc4o. Cbcm. L&t. 1982 1749 7.-C. J. GiImor. MITHRIL data. Univ. of Giasgow.
A computer Scotiand
program
for the automatic
solution
of aystal
structures
from X-Ray
8.- J.M. Stewart, PA. Dickinson, H.L. Amman, H. Heck, H. Flack. The XRAY 76 System. Techn. 446. Computer Science Center. Univ. Of MaryIand. CoIIege Park. MaryIand 1976. 9.- International Khmer
Tables
Academic
for X-Ray Pubhshers.
Crystallography
(1974). Vol. IV. Birmingham
Kynoch
Pren.
Rep. TR -
(Present
Distributor
Dordrecht)
lo.- M. Martinez-Ripoh, J. Fayos (1930). PESOS. Institute RocasoIano CSIC. Serrano 119. 28006 Madrid Spain 11.- M. Martiuez-RipoR J. Fayos (1979). CONFAB. Institute RocawIano CSIC. Serrano 119. 28006 Madrid. Spain 12.- G.M. Sheldrick (1986). SHELXS - 76. Program for crystal structure solution. Univ. of Gatingen. FRG. 13.- G.M. She&k (1976). SHELXS - 76. Program for crystaI structure determination. England. 14._ J. Finer, J. Cldy, W. Fenid, L. MinttIe, R. Riccio, J. Battaik, M. Kirkup, RE.
Univ. of Cambridge. Moore.
1979, 44.2044 15,s I. Ohtani, T. Kusumi, M.O. Ishitsuka, H. Kakisawa. Tet. Lett. 1989, 30, 3147 16.- DJ. Vaderah, PA. Wendkr, L.S. Ciereszko, FJ. Wunits, P.D. Rkstrand, D. Van der
sot. 1977.99.5780.
1. Chg. Chm
Helm. J. Am Chcm-
NEW XHNICANE
cmom2om $3.00+.00 63 1990 PsgmwmResr plc
DITHRPHNEI
THE BROWN ALGAEl OF WCTYOTACHE
PROM
Manuel Nor&, A.G. Gonz#ez, Patrkia Amyo,
Miguel Z&rage, Cirilo P&m,
Matias L. Ro-
driguez, Catalina Ruiz-Perez and Luis Dorta Centro de Productos Naturales Or@nicos Antonio Gonzalez. Institute Universitario Bio-orgtlnica. Universidad de La Laguna. 38206 La Iaguna. Spain.
de Qulmica
(Received in UK 2 April 1990) Summary: Two new xenicane diterpenes have been isolated from the brown algae of the Dictyotaceae family, and their structures and absolute configurations have been elucidated on the basis of their spectral and X-ray diffraction analyses.
Brown algae of the Dictyotaceae different carbon
frameworks’.
most intriguing
family are characterized
Among the diterpenes
groups are the xenicanes,
by the production
of diterpenoids
found in this family of seaweeds, one of the
some of them with a significant
cytotoxic activity2, which
have been isolated not only from alga but also from soft corals and gorgonians’“. compounds
are characterized
in other natural
with
as being composed of a cyclononane
skeleton,
Structurally
these
which is rarely found
products.
In this paper, we wish to describe the structures of two new xenicane derivatives isolated during the comparative
study of the brown algae communities
have collected
at Valparaiso
from the Atlantic
(Chile) the brown alga Glossophora kuntii from which we have iso-
lated the xenicane derivative 2 Gn the other hand, the diterpene Dictyota sp collected Compound
1, (a,)=
Its molecular Absorptions
at Tenerife
was established
in the I.R. spectrum
hydroxyl, acetate the UV spectrum
1 was isolated from the brown alga
in the Canary Islands.
-80.P (c, 0.29, CHClJ,
formula
and Pacific shores. Thus, we
was isolated as a crystalline
as C,I-I,,O,
compound
on the basis of its HRMS
(m.p. 53-54 Qc). (m/z
378.2397).
at 3435, 1730 and 1760 cm” were due to the presence
and a,Runsaturated
carbonyl groups, this last one being confirmed
at 225 run. Moreover,
the NMR spectra established
ymethyl group (*)C: d, 63.8; ‘H: d, 4.63 and 4.73); a trisubstituted
the presence
by a band in of an acetox-
epoxy ring (UC: d, 60.09 and 63.32;
‘H: d, 2.88 and 1.5). a secondary hydroxyl group (UC: d, 68.21; ‘H: d, 4.16) and a disubstituted unsaturated together
of an
a&
aldehyde group (UC: b, 189.8, 152.41, 100.67, ‘H: d, 6.82 and 9.32). The NMR spectra,
with the presence
of the fragmentations
revealed that the 6 methyl-5-hepten-Zyl
at m/z
109 and 69 in the MS spectrum,
group, the typical side chain in the Dictyotaceae
was present. 6125
also
diterpenes.
6126
M. NORTE er al.
The assignments bidimensional, published
of the chemical shifts of home- and heteronuclear
for fukurinolal’
works as a metaholite compound
of compound
from Gloasophora manner.
hmti
Its spectral
xenicane skeleton, “C:
of Dilophus
okamurai
2 (c.Q=
collected
properties
1 (Table I) were made by using mono- and
NMR experiments.
or hydroxyacetyldictyolal‘
1 was the 6.7-epoxy derivative
The structure
compound
Comparison
d; * _
and Didyota
at Wparaiso
(Chile),
I) confirmed
in which the presence
of a hemiacetal
isolated
C,%O,
that compound
those of isodictyohemicetal
4, metabolite
difference
of the C(6) and C(7) olefinic
presence of signals from a trisubstituted
respectively,
indicated
that
(m/z 320.3241), isolated
was deduced
in essentially
2 also possesses
moiety was evident:
d, 100.3 and 71.1; ‘H: d, 4.39, 5.67. In fact the comparison
was the absence
in two independent
of 3.
t6.81* (c, 0.088. CHClJ,
(Table
of these data with those
3, which was published
a 6,7-epoxy
IR: 35OOcrrP; NMR:
of the WNMR
from D. dUotm&,
the same
signals of 2 with
showed that the obvious
signals at b 134.6 and
124.7, and the
epoxy ring at b 60.4 and 63.9. Thus we can conclude
that
2 is the 6,7-epoxy isodictyohemicetal. The structures
of these
compounds
crystallized in the orthorhombic the asymmetric
AED four-circle
by X-ray diffraction
space group P2,2,2, with one molecule
unit. Cell constants
unique diffraction
were confirmed
Compound
1
C,H,O,
in
of composition
were a = 9.423( 1). b = 10.236(l) and c = 22.675(l)
maxima with 3 s 28 s 1289 were collected diffractometer
analysis.
using graphite
monochromated
on a computer-controlled CuKa
(154178
A> radiation
A All Siemens and a
New
Tabla
c
I:
6Ml SpctFa1
2
1
6127
xenicane diterpenes
of CqJounds I a?& 2
data
H
1
2
-
-
1
120.67
146.6
2
38.78
44.9
2
3.25
dd.
3
49.12
53.8
3
1.80
bn
4
68.21
27.9
4
4.16
da,
?.1;3.5
5
47.66
39.8
5 5
1.06 9.42
&i, ad,
14.137.1 14.113.5
6
60.01
60.4
6
10;8.5
2.58
ba
-_.
7
62.32
63.9
7
2.90
d,
3-03
&i,
8
26.65
26.1
8 8
2.91 2.45
dd, 9.1;18 &id, 3.5;10;16
2.65 2.33
&id, d&i,
9
152.41
116.8
9
6.82
dd,
5.64
c&i, 1.6;8.4
10
32.12
31.9
10
2.41
m
1.88
m
11
38.38
38.1
11
1.15
m
1.16
m
12
26.13
26.6
12
1.79
m
1.92
m
13
124.56
124.4
13
5.07
bt,
5.03
bt,
14
131.58
131.4
14
15
17.85
17.6
15
1.61
16
25.77
25.5
16
1.51
17
17.74
17.3
18
63.80
100.2
19
189.80
71.1
17 18 18 19
1.00 4.61 4.71 9.42
20
20.3
17.0
20
1.81
10
9.1;3.5
7
1.9~8.4;10.8 1.9;10.8;16.2
7
1.65 1.58 d. 7 t. 10 dd, 8.5;lO d, 1.9
0.98 5.67
be
4.39
ba
1.40
170.84
Ic=o) Ile(OAc)
1.93
21.05
a) AsaQmnmta
made bg hetinmuctoar
w:8 scan. After correction 1912 reflections A phasing
COSY. b) assigrsrrnts and kzmJ?ru&?ar CosY
for Lorentz, polarization
surveyed were considered
observed
made
and background
by hmomclear
(I 2 3o(I)).
model was arrived at using a multisolution
was anisotropically
refined
from International
Tables
by block-diagonal
weighted
least squares
for X-Ray Crystallography9.
density map. Art appropriate
decoupti~
effects, only 1897 (99%) of the
tangent
formula
magic integers’. The best model from this approach showed all non-hydrogen
electron
1.9;10.8
was carried out”. A final weighted anisotropic
contribution
for H atoms) gave for the correct enantiomer
factors were taken
were located on a difference
weighting scheme to normalize
using
atoms. The structure
(on F)a. Scattering
All H-atoms
approach
full-matrix
the discrepancy
vs.
and
(fixed isotropic
indices R= 0.055 (Rw=
0.060). The absolute configuration
of 1 was determined
by comparison of 30 Bijvoet pairs with Fo
which are in the range 5.c Fc < 50. and 0.2 < (sin6/1)
>Sa(Fo),
< 0.4 A-t. The averaged Bijvoet differences
6128
M. Nome et al.
0.0323( 0.2973( -0.1367( 0.0452( 0.4182( 0.0239( 0.0541( -0.0818( -0.0900( -0.1406( -0.0585( -0.1021( -0.0035( 0.0045( -0.1105( -0.2712( -0.3140( -0.4707( -0.5280( -0.6836( -0.4440( -0.0343( 0.1818( 0.0208( 0.0893( 0.4061( 0.5069(
01 02 03 04 05 Cl c2 C3 c4 C5
C6 Cl CB c9
Cl0 Cl1 Cl2 Cl3 Cl4 Cl5 Cl6 Cl7 Cl8 Cl9 c20 c21 c22
lbbh
cooniimtiw
Atic
II.-
01 02 02 03 03 04 OS Cl Cl Cl c2 c2 c3 c3 Cl8 C6 c9 c2 c2 Cl Cl c3 c2 c2 c4 04 c3 04 c4 03 c5 c5 03 03
1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 11 1) 1) 1) 2) 2) 1) 1) 1) 1) 1) 1)
for tzoqmnd - Cl9 -
Cl8 c21 C6 c7 c4 c21 c2 c9 Cl9 c3 Cl8 c4 Cl0
-
02 03 Cl Cl Cl c2 c2 c2 c3 c3 c3 c4 c4 c4 c5 C6 C6 C6 C6 C6
1
-
-
ebl.% III.- Intemtoric
(Al
5) 4) 4) 4) 5) 4) 6) 4) 5)
:*:9: 1:529 1.548 1.549
; ( ( (
:; 4) 4) 4)
Cl9 c9 Cl8 c3 Cl8 Cl0 c4 Cl0 c3 c5 c5 C6 c5 c20 c7 c20 c7
0.7595(
0.8599( 1.0218( 0.9929( 0.9383( 0.8482( 0.8921( 0.9075( 0.9739( 1.0148( 1.0094( 0.9615( 0.9247( 0.8634( 0.8672( 0.8629( 0.8154( 0.8161( 0.8015( 0.8060( 0.7792( 0.8854( 0.8735( 0.7836( l.O35J( 0.8963( 0.8779(
1) 1) 1) 1) 1) 1) 1) 1) 1) 1) I) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1)
and squiaulmt iclotn@o ‘8. in I 1.
( ( ( ( ( ( ( ( (
Cl9
1) lb li 1) 3) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 1) 2) 1) 1) 1) 1) 1) 1) 1)
635(10) 662( 7) 772( 9) 580( 7) 1273(17) 562( 9) 476( 8) 452( 7) 499( 8) 589( 9) 567( 9) 632(10) 750(13) 688(12) 481( 8) 552( 9) 674(11) 656(11) 779(13) 1348(29) 1081(20) 615(10) 561( 9) 705(12) 657(11) 586(10) 816(14)
factore (A2 I 103)
t.aqmm-
vith e.e.d.
1.205 1.460 1.319 1.468 1.444 1.438 1.172 1.528 1.344
- c21 - c7
-
0.0621( 0.03421 -0.199oi 0.2087( 0.0914( -0.0678( 0.0419( 0.1245( 0.1587( 0.0484( -0.0780( -0.1663( -0.2486( -0.1934( 0.2438( 0.2685( 0.3659( 0.3961( 0.5094( 0.5337( 0.6218( 0.3703( 0.1244( -0.0423( -0.0806( 0.0257( -0.0787(
119.2 60.7 114.6 121.1 124.1 111.9 112.8 113.9 115.7 112.2 112.7 109.1 115.8 110.8
c4 c5 C6 C6 c7 C8 Cl0 Cl0 Cl1 Cl2 Cl3 Cl4 Cl4 c21 ( I i ( ( ( ( ( ( ( ( ( ( f
3) 21 3j 3) 3) 2) 2) 2) 2) 2) 2) 2) 5) 2)
114.9
i
3j
116.7 117.0 116.3 111.9 58.8
( ( ( ( (
3) 3) 3) 3) 2)
dibmoee
-
c5 C6 c7 c20 C8 c9 Cl1 Cl7 Cl2 Cl3 Cl4 Cl5 Cl6 c22
c7 03 C6 03 c7 Cl c3 c3 Cl1 Cl0 Cl1 Cl2 Cl3 Cl3 Cl5 02 01 ::
-
02
- c21
(A) and angEe
1.538 1.512 1.472 1.513 1.506 1.502 1.539 1.537 1.522 1.509 1.320 1.491 1.484 1.490 C6 c7 c7 c7 C8 c9 Cl0 Cl0 Cl0 Cl1 Cl2 Cl3 Cl4 Cl4 Cl4 Cl8 Cl9 c21
-
( ( ( ( ( ( ( ( ( ( ( ( ( (
4) 5) 5) 5) 5) 6) 4) 4) 5) 5) 6) 8) 7) 5)
c20 C6 C8 C8 c9 C8 Cl7 Cl1 Cl7 Cl2 Cl3 Cl4 Cl6 Cl5 Cl6 c2 Cl OS c22
122.2 60.4 125.5 122.3 109.4 127.2 115.1 109.8 109.8 114.4 112.7 125.2 123.2 122.1 114.7 107.2 126.8 125.3 123.1
- c22
111.6
( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (
(Q) of t_xqwmd 1 vith o.6.d.
3) 2) 3) 3) 3) 3) 2) 2) 2) 3) 3) 4) 5) 4) 5) 2) 4) 3) 4) 3)
‘8.
in I ).
6129
New xenicane diterpenes
are 0.274 for the correct enantiomer isotropic thermal parameters
vs 0.348 for the wrong one. The final positional
and equivalent
are given in Table II. A drawing of the final X-ray mode1 less hydro-
gens is given in Fig.1. Bond lengths and bond angles are listed in Table III.
Molecules interact
in the crystal through a hydrogen bond, with hydroxyl group O(4) as donor and
the O(5) of a molecule
related by x-1/2, -y+1/2,
-z+2 as acceptor. Geometrical
parameters
of this
hydrogen bond are OmmmO: 2.838(S), H nmm0: 1.91 (1) and G-HmmmO: angle 155.5 (2)*. The chains formed by these interactions 3.3SP between Compound
are depicted in Fig.1. No other intermolecular
non-hydrogen
2 (C,H,O,)
16.687(l), b= 6.260(l),
crystallized in the monoclinic c= 21.230(l)
The structure
Blocked full-matrix
least-squares
positions
= 1.084
with C-H
thermal parameter. mal parameters
shorter than
atoms exist.
2h \ 1289 were collected in the manner judged observed.
interactions
space group C(2). The cell constants were a=
P, 8= 120.4(2)Q. All unique diffraction
maxima with also 3 \
described for 1 and 1298 (83%) of the 1554 reflections were
was solved using direct methodsU and subsequent refinement and refined
Fourier
on F. Some H atoms were introduced riding on their carrier
In the final cycles of the refinement
for the non-H atoms, positional
parameters
positional
at calculated
atoms with a general and individual
analysis.
isotropic
anisotropic
ther-
for H-atoms, their isotropic thermal pa-
rameter and an overall scale factor were varied. For 2 the final R value was 0.043, Rw= 0.050, w = l/[c~*(Fo) t O.OOll(Fo)2] The refinement lute configuration
was fured by comparison
calculation
were performed
with SHELX76”.
of 65 Bijvoet pairs with Fo s Sa(Fo), which are in the
ranges 5. 5 Fo I 50. and .2 5 sine/A zs .4A-LI*. The averaged Bijvoet differences correct enantiomer
The abso-
vs 0.491 for the wrong one. Fig, 2 shows the molecular
are 0.427 for the
configuration
and the
. 6130
M. NORTE etal.
01
0.1792( 0.4997( 0.5240( 0.4159( 0.3776( 0.2821( 0.2100( 0.1540( 0.2149( 0.2530( 0.3463( 0.4077( 0.2898( 0.2126( 0.2211( 0.1489( 0.0768( 0.0100( 0.0549( 0.2658( 0.4610( 0.4789( 0.2600(
02 03 Cl c2 C3 CI CS C6 C7 C8 c9 Cl0 Cl1 Cl2 Cl3 Cl4 Cl5 Cl6 Cl7 Cl8 Cl9 c20
!lkzbts V.-
Atamk
oooldinotes
0.2796(
2) 2) 2) 2) 2) 2) 3) 3) 2) 3) 3) 2) 3) 3) 4) 4) 4) 4) 5) 4) 3) 3) 4)
(A)
l)
' 0.4002( 0.3110( 0.3964( 0.3656( 0.3314( 0.2569( 0.2530( 0.2695( 0.3688( 0.3861( 0.4462( 0.4156( 0.1868( 0.1269( 0.0591( 0.0047( -0.0569( -0.1091( -0.0662( 0.1562( 0.3271( 0.3372( 0.4190(
0.3183( 8) 0.5645( 8) 0.1963( 9) 0.4127( 9) 0.3968( 9) 0.5610(10) 0.4845(10) 0.4344( 9) 0.2165( 9) 0.1559(10) 0.0914( 9) 0.4079(10) 0.2682(11) 0.2345(15) 0.0644(13) 0.1370(12) -0.0293(14) 0.3572(15) 0.6330(11) 0.4980(10) 0.1285(10) 0.6207(10)
and
sqvimtent
isotropic
2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 2) 3) 3) 3) 4) 5) 3) 2) 3) 3)
59( 1) 64( 63( 47( 45(
2) 1) 2) 2)
::I 55( 46( 47( 53( 51( 54( 59( 85( 78( 76( 104( 121(
:; 2) 2) 2) 2) 2) 2) 2) 3) 3) 3) 3) 4)
::I :1 60( 2) 61( 2)
tkmqxtm-
faotom
(A=2 10’)
for c?mpomd 2 uith 8.8.d.'8. in ( 1. -
01 01 02 02 03 Cl Cl Cl c2 c2 c3 c3 c4 C6 Cl8 c9 c2 c2 Cl Cl c3 c2 c2 c4 C3 c4 01 CS c5 01 01 c7 lhble
N.-
-
C6 c7 Cl8 Cl9 Cl8 c2 c9 Cl9 c3 Cl8 c4 Cl0 c5
01 02 Cl Cl Cl c2 c2 c2 c3 c3 c3 c4 c5 C6 C6 C6 C6 C6 C6
-
1.476 1.452 1.413 1.439 1.430 1.525 1.318 1.499 1.575 1.530 1.536 1.563 1.550 c7 Cl9 Cl9 Cl9 c9 Cl8 c3 Cl6 Cl0 c4 Cl0 c5 C6 c5 c20 c7 c20 c7 c20
( 9) ( 9) (10) (11) ( 8) ( 9) (10) (12) ( 6) (10) (11) (10) (11)
c5 C6 C6 c7 C8 Cl0 Cl0 Cl1 Cl2 C13‘ Cl4 Cl4
60.0( 4) 109.2( 7) 124.0( 6) 106.1( 5) 129.6( 6) 98.9( 5) 113.1( 6) :::.:I :; 112:2( 5) 112.1( 5) 115.7( 6) 111.9( 6) 116.5( 6) 116.7( 6) 116.4( 5) lll.O( 5) 59.2( 4) 123.2( 5)
IntinZtani4 di8tztnc88IA) and an&88
-
01
C6 01 c7 Cl c3 c3 Cl1 Cl0 Cl1 Cl2 Cl3 Cl3 Cl5 03 02 02 02
C6 c7 c20 ca c9 Cl1 Cl7 Cl2 Cl3 Cl4 Cl5 Cl6
-
c7 c7 c7 C8 c9 Cl0 Cl0 Cl0 Cl1 Cl2 Cl3 Cl4 Cl4 Cl4 ClE Cl8 Cl8 Cl9
1.504 1.465 1.510 1.511 1.498 1.542 1.540 1.532 1.512 1.319 1.510 1.473
-
( 7) (10) (10) ( 7) (11) ( 9) (11) (13) (13) ( 9) (12) (14)
C6 C8 C8 c9 C8 Cl7 Cl1 Cl7 Cl2 Cl3 Cl4 Cl6 Cl5 Cl6 c2 C2 03 Cl
(9) of oaparod 2 vith
60.6( 125.1( 121.8( 109.1( 126.3( 113.4( 109.2( llO.l( 114.5( 112.6( 125.8( 124.3( 120.7( 115.0( 106.8( 106.8( 110.9( 106.0(
4) 6) 5) 5) 6) 5) 5) 5) 7) 7) 9) 9) 9) 8) 6) 6) 6) 6)
8.8.d.'8. in ( )
6131
New xenicane dimpenes atomic numbering,
together
with the crystal packing along the a axis. In Tables IV and V bond
lengths and angles, and final positional
and equivalent
isotropic thermal parameters
respectively are
reported. They compare well with 1 and those observed in other related marine diterpenes”.
Bond
distances
Four
and angles are normal.
The five-membered
ring shows an envelope
of the five ring atoms are almost coplanar ( as defined by the C( 18)-0(2)X(
conformation.
19)X( 1) dihedral angle
of 4.6(8)O), while the fifth atom C(2) lies 0.431A above this plane.
Fig. %.- Perspsctiw oiau of the structum of d, ek.n&g diagmm. The crystalline
lar distances
ldmtling and packing
cohesion is ensured by a hydrogen bond between the hydroxyl group O(3) as donor
and the O(1) of the epoxide of a molecule H0(3)m~O(l)
akmic
related
by x + 12, y + l/2,
a, as acceptor.
The
bond length is 2.819(7)A and the angle of this bond is 159.1(l)Q. Other intermolecuare in the normally
expected range for nonbonded
contacts.
The interest of different marine chemistry research groups in this type of compounds not only to their pharmacological
activity but also to their structural
1 and 2, we can infer that, in solution, the preferred conformation
has been due
features. Thus, for compounds
of the nine-membered
ring is that
in which the dihedral angles between the carbon protons C(2) and C(3); C(3) and C(10) for 1 and 2, together with those between this conformation
C(3) and C(4) for 1 and between C(2) and C(18) for 2 are 909. In
can be explained,
as advanced by Matsumoto6, the deshielding
the NMR chemical shifts in compound
1 for the methyl group C(20).
On the other hand, the absolute configuration ing a xenicane advanced
skeleton,
conclusion
effect observed in
of some marine diterpenes
from brown algae possess-
has recently been published U. In our case, the results also confirmed
that the absolute
con@ration
algae are opposite to that of xenicin, isolated
of the xenicane
from soft cotalP.
diterpenes
the
from Dictyotaceae
6132
M. NORTEet al.
EXPERIMENIXL
PART
Infrared spectra were reuxded on a Perkin-EImer Mod. 257. OpticaI rota&ns wore determined for solution in chloroform with a Perkin-EImcr Mod. 241 po&rimcter. ‘H-NMR and rsCNMR spectra were recorded on a Brukcr Mod. WP-200 SY (200 MHz), chemical shifts ue reported rclatiw to Me,Si(d 0) and coupling constants are given in hertz The 2DNMR spectra were obtahmd using Bruker’s microprograms. Low and high resolution mass spectra were obtained from VG micromass 24E2F spectrophotometer. Silica gel chromatography was performed on silica gel 60 G, TLC and PLC obtained from Merck products. The tk plates were developed by spraying with 6N suIphuric acid and heating. Sephadon I&f-20 obt&ed from Pharmacia was used for gel fihration chromatography. AII solvents were puritied by standard techniques. Anhidrous sodium suIfate was used for driying solution. Collectton, atnetton and ehrematqaphk aepantfon. Dktyotn sp was coUected at -10 m deep at GtIimar (Tenerife, Canary IsIamB) in November 1987. The air-dried alga (8 kg) was extracted with acetone and diet.hyI ether and the solvents were evaporated in vacua to yield 220 gr of extract. GIosaophcua kuntii was cohectod in shallow water at Iow tide near Valparaiso (Chile) in January 1986 and treated as above to yield LX7 gr of crude extract. The chromatographic treatment of both extracts were idcntical. Fust, Bash chromatography on silica gel column &ted with mixtures of n-hexane/ethyI acetate of increasing polarity. The fractions ehrted with n-Hu/EtOAc 70% were wahincd to yield, after sohnnt evaporation, compound 1 in the crude extract of Dictyota sp and compound 2 in thcxc of G. kunti. These extracts were submitted to repeatcd chromatographius on sihca and finaUy purified by chromatography on a Scphadex LH-20 column with CHCI+MeOH:n-Hux (1:1:2) as eluent to give pure compounds 1 and 2. Compound 1: solid (m.p. 53-W C), (a,= -80.70 (c, 0.29, CHCIs). UV,: 225 run (e- 5333 ). IR: 3435, 2900, 1720, 1670, 1440, 136Oand 1020 cm”. HRMS: M* at m/z 3782397 (CaIc 378.2406). MS: m/z 378 (M*), 360, 332, 318, 109, 69. NMR spectra: see Table I. Compound 2: solid (m.p. 90-92 PC), (at,)- +6.819 (c, OSS, CHCI& UV,: 208 nm (e= 2831). IR: 3550, 2950, 1750, 1350, 1050 cm”. HRMS: M* at m/z 3202341 (CaIc. 320.2331). MS: m/z 320 (M*), 302, 284, 259, 231. 109, 69. NMR spectraz see Table 1. Acknuwtedgmmta: We acknowIedga SnanciaI support from PIan NacionaI de lnvestigacion FAR 88-0500. PA. and M.Z. acknowIedge Institute de &opera&n Iberoamericana (ICI) and Banco Central de Espatia respectively for a fellowship. The authors acknowledge to Dr. Patricia Rivera (University of Chile) for collection of C. kuodi.
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