Haliclorensin, a novel diamino alkaloid from the marine sponge Haliclona tulearensis

Article abstract of DOI:10.1021/np970442x

Haliclorensin (1), a novel diamino alkaloid possessing an azacyclodecane ring, has been isolated from the sponge Haliclona tulearensis. Its structure was elucidated on the basis of spectroscopic data, as well as by comparison with γ-amino azacycloalkanes.

Full text of DOI:10.1021/np970442x

282
J . Nat. Prod. 1998, 61, 282-284
Ha liclor en sin , a Novel Dia m in o Alk a loid fr om th e Ma r in e Sp on ge Ha liclon a
tu lea r en sis
Ganit Koren-Goldshlager,† Yoel Kashman,*,† and Michael Schleyer‡
School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel, and Oceanographic Institute,
Durban, Republic of South Africa
Received September 24, 1997
Haliclorensin (1), a novel diamino alkaloid possessing an azacyclodecane ring, has been isolated
from the sponge Haliclona tulearensis. Its structure was elucidated on the basis of spectroscopic
data, as well as by comparison with γ-amino azacycloalkanes.
A number of interesting biologically active compounds
have been reported from the marine sponge genus
Haliclona. The examples reported from this genus
include the cytotoxic haliclonacyclamines;1 the antifun-
gal pentacyclic alkaloid, papuamine;2 haliclonadiamine;3
the antimicrobial cytotoxic alkaloids, haliclamines;4 and
the manzamines.5,6
In our search for biologically active substances from
marine organisms,7 an extract from the orange marine
sponge Haliclona tulearensis exhibited strong cytotox-
icity against P-388 mouse leukemia cells (IC50 ) 0.1 mg/
mL). The sponge was collected by scuba at Sodwana
Bay, Durban, South Africa, at a depth of 15 m; MeOH-
EtOAc (1:1) extraction of the freeze-dried sponge yielded
an extract that was partitioned between different
solvents.8 The n-BuOH- and CHCl3-soluble materials
were separately subjected to RP-18 chromatography,
eluting with a MeOH-H2O gradient. Further purifica-
tion of fractions containing 1 on a Sephadex LH-20
column, eluting with MeOH, afforded pure haliclorensin
(1, 0.55% dry wt).
these assignments and suggested the connectivity be-
tween the two spin systems through the tertiary nitro-
gen as shown in the structure. The positive FABMS of
1 showed a pseudomolecular ion peak at m/z 213, and
HREIMS established its molecular formula as C13H28N2,
in full agreement with structure 1. Also, in full agree-
ment were the carbon-carbon bond cleavages, R,â to
the N-atoms, in the mass spectrum, yielding the ions
at m/z 44 (C2H6N+, 100%), 183 (M+ - CH2dNH, 19%),
and 170 (M+ - C2H4N, 13%).
Interesting to note is the strong dependence of the
NMR spectra of 1 on the acidity of the measured sample
and, therefore, also on the presence of other accompany-
ing polar compounds. This behavior created difficulties
during the purification process. Although protonation
of a nitrogen atom, in acidic media, causes a pH-
dependent downfield shift of the R-proton signals,9 the
carbon resonances of 1 were shifted upfield at an
unpredictable rate. The complexity of the situation is
demonstrated by the comparisons of the δc values of 1
and several model compounds (2-5),10 summarized in
Table 2.
The comparison of the δc values of compounds 1-4
with the resonances of 5 (the only mono amino com-
pound) point clearly to the influence of the primary
γ-amino group, an influence that might suggest a strong
hydrogen bond between the two nitrogen atoms, in the
neutral state, which affects the carbon resonances.
Keramaphidin C, 6Z-azacycloundecene, was the first
reported marine azamacrocycle,11 and it is suggested to
be a precursor of manzamine C, which incorporates this
ring in its structure.11 The azamacrocycle in man-
zamine C is attached to a second nitrogen atom through
a three-methylene unit, which is suggested to be derived
from acrolein or its bio-precursor. A similar biogenetic
route to the one suggested for manzamine C11 may also
be suggested for haliclorensin (1), with the tryptophan
being replaced by ammonia or its bio-precursor.
Noteworthy is the sodium channel-blocker activity as
well as inhibition of leishmania parasites of a whole
series of compounds incorporating the N-(γ-aminopro-
pyl) azacycloalkane moiety in their structure.12,13 The
primary amino group of 1 is expected to form a Schiff
base readily and thus to result in analogous bioactive
compounds. Work is ongoing in tracing the more polar
compounds responsible for the cytotoxicity of the sponge
extract.
Haliclorensin (1), [R]D ) -2.2°, was obtained as a
colorless oil. The 13C-NMR and DEPT experiments
(Table 1) disclosed one methine, 11 methylenes, and one
methyl. The 13C chemical shifts of C-2 (δc 48.5), C-10
(δc 42.4), C-1′ (δc 41.3), and C-3′ (δc 41.2) indicated that
each one of these four carbons was proximate to a
nitrogen atom. Evident from the proton NMR spectrum
was a >NCH2CH(CH3) group (δ 2.67 dd, 2.88 m, H-2a,-
2b; 1.91 m, H-3 and 0.92 d, CH3-11). COSY and TOCSY
1
analysis of the H-NMR spectra (Table 1) revealed two
spin systems: >N(CH2)3NH2 and >NCH2CH(CH3)-
(CH2)7N<. HMBC cross peaks (Table 1) confirmed
* To whom correspondence should be addressed. Phone: +972-3-
6408419. Fax: +972-36409293. E-mail: kashman@post.tau.ac.il.
† Tel Aviv University.
‡ Oceanographic Institute, Durban.
S0163-3864(97)00442-4 CCC: $15.00
© 1998 American Chemical Society and American Society of Pharmacognosy
Published on Web 01/30/1998

Notes
J ournal of Natural Products, 1998, Vol. 61, No. 2 283
Ta ble 1. NMR Data of Haliclorensin (1) (500 MHz, in DMSO-d6)
C#
2
δc (mult)
δH (mult, J in Hz)
COSY & TOCSY
HMBC (HfC)
48.5 (t)
2a: 2.67 (dd, J ) 12.8,6.9)
2b:2.88 (m)
1.91 (m)
4a: 1.11 (m)
4b: 1.52 (m)
1.30-1.42
6a: 1.24 (m)
6b: 1.42 (m)
7a: 1.24 (m)
7b: 1.42 (m)
1.30-1.42 (m)
9a: 1.50 (m)
9b: 1.70 (m)
10a: 2.84 (m)
10b: 2.96 (m)
0.92 (d, J ) 6.5)
1′a: 2.94 (m)
1′b: 3.09 (m)
2′a: 1.94 (m)
2′b: 2.12 (quin, J ) 7.0)
3.03 (m)
2b, 3, 11
2a, 3, 11
2a, 2b, 11
4b
3, 4, 11, 1′
3, 4, 11, 1′
2, 4, 5, 11
2, 3, 6, 11
2, 3, 6, 11
6, 7
8
8
8, 9
8, 9
6, 7
7, 10
7, 8, 10
8, 1′
9, 1′
2, 3, 4
2′, 3′, 2
2′, 3′, 2
1′, 3′
1′, 3′
1′, 2′
3
4
26.5 (d)
30.3 (t)
4a
5
6
22.6 (t)
24.3 (t)
7
24.1 (t)
8
9
22.3 (t)
21.5 (t)
9b, 10a, 10b
9a, 10a, 10b
9a, 9b, 10b
9a, 9b, 10a
3, 5, 4a, 4b
1′b, 2′a, 2′b
1′a, 2′a, 2′b
2′b, 1′a, 1′b
2′a, 1′a, 1′b
2′a, 2′b, 1′a, 1′b
10
42.4 (t)
11
1′
17.7 (q)
41.3 (t)
2′
3′
19.2 (t)
41.2 (t)
Ta ble 2. 13C-NMR Data of Haliclorensin (1) and Model
Compounds 2-5a,b
ent, and then on a Sephadex LH-20 column, eluted with
MeOH-CHCl3 (1:1), to afford 1 (20 mg, 0.55% dry wt).
no.
1
2
3
4
5c
Ha liclor en sin (1): an oil; Rf ) 0.62 (MeOH-CHCl3;
3:2), visualized with I2; [R]D -2.2° (c 1.3, MeOH); NMR
data in Table 1; EIMS m/z (%) [M]+ 212 (35), 183 (22),
170 (13), 168 (10), 154 (30), 112 (33), 99 (84), 85 (39),
70 (69), 56 (41), 44 (100); HREIMS m/z 212.2250 (calcd
for C13H28N2, 212.2252).
1′ 48.1
2′ 22.1
3′ 46.7
49.7
24.1
47.1
58.2
57.0
24.3
47.7
54.3
56.8
30.2
39.6
44.7
55.7
19.5e
21.4e
52.1
2
53.1
10 50.7
1′ 41.9 (6.2)d 49.7 (0)
54.0 (3.0)
55.1 (1.7) 56.1 (-0.4)
22.9 (7.3) 19.8e (-0.3)
2′ 20.6 (1.5) 22.9 (1.2) 22.3 (2.0)
Syn th esis of N-(3-Am in op r op yl)a za cyclotr id e-
ca n e (2). Azacyclotridecane (92 mg, 0.5 mmol) and an
equimolar amount of acrylonitrile (33 µL) were dissolved
in dry MeOH (6 mL), and the mixture was stirred at
room temperature for 4 h.13 The solvent was removed
under reduced pressure, and the residue was chromato-
graphed on Sephadex LH-20. The purified product
[N-(3-propionitrile)azacyclotridecane] (75 mg, 0.31 mmol)
was dissolved in MeOH (20 mL) (saturated with NH3)
and was hydrogenated over Raney Ni at room temper-
ature at 3 atm, for 1 h. The catalyst was removed by
filtration, and the residue was purified by Sephadex LH-
20 column to give 2 (65 mg, 0.27 mmol, 85% yield).
3′ 41.3 (5.4) 37.3 (9.8) 37.3 (10.4) 37.1 (2.5) 21.6e (-0.2)
2
49.6 (3.5) 52.7 (5.5) 54.0 (0.3)
43.4 (1.3) 52.4 (-0.3)
10 44.1 (6.6)
a
2: N-(3-Aminopropyl)azacyclotridecane; 3: N-(3-aminopropy-
l)piperidine; 4: 3-dimethyaminopropylamine; 5: N-butylpiperi-
b
dine. Taken in D2O with dioxane as an internal standard for
calibration. c Measured in neutral and acidic DMSO-d6. TFA
d
added, values in parentheses are ∆δc values between neutral and
acidic measurements. e Exchangeable.
Exp er im en ta l Section
Gen er a l Exp er im en ta l P r oced u r es. Mass spectra
(low resolution and high resolution) were recorded on a
Fisons, Autospec Q instrument.1H- and 13C-NMR spec-
tra were recorded on Bruker AMX-360 and ARX-500
spectrometers. Optical rotation was measured on a
Perkin-Elmer model 141 polarimeter using a 1-cm
microcell.
Com p ou n d 2: an oil; Rf ) 0.59 (MeOH-CHCl3; 3:2),
visualized with I2; 1H NMR (D2O + dioxane + TFA; 100:
0.1:0.1; 360 MHz) (pH ) 2.5) δ 3.22 (4H, m), 3.12 (4H,
m), 1.78 (4H, m), 1.39-1.48 (18H, m); 13C NMR (D2O +
dioxane + TFA; 100:0.1:0.1; 90 MHz) (pH ) 2.5) δ 52.7
(t, C-2/13), 49.7 (t, C-1′), 37.3 (t, C-3′), 26.0, 25.2, 25.0,
24.5, 21.6 (10 methylenes, C-3÷C-12), 22.9 (t, C-2′);
FABMS; m/z (%) [MH]+ 241 (100), 196 (M+ - C2H6N,
10), 184 (14).
Collection a n d Isola tion P r oced u r es. The sponge
Haliclona tulearensis (class Demospongiae, order Hap-
losclerida, family Chalinidae, genus Haliclona) was
collected in Sodwana Bay, South Africa, by scuba at a
depth of 15 m during September 1995. The sponge was
described as a fine, “muddy” orange laminate sponge
with large oscula on its ridges. A voucher sample is
deposited in the Zoological Department at Tel Aviv
University (TASA 121).
Syn th esis of N-(3-Am in op r op yl)p ip er id in e (3).
Synthesis of 3 was done following the same procedure
as for 2, starting from piperidine.
Com p ou n d 3: an oil, Rf ) 0.45 (MeOH-CHCl3; 3:2),
visualized with I2; 1H NMR (DMSO-d6, 500 MHz) δ 2.80
(2H, d, J ) 11.6 Hz, H-2a/6a), 3.33 (2H, d, J ) 11.6 Hz,
H-2b/6b), 1.74 (2H, m, H-3a/5a), 1.78 (2H, m, H-3b/5b),
1.33 (1H, m, H-4a), 1.64 (1H, m, H-4b), 3.08 (2H, m,
H-1′), 2.02 (2H, br q, J ) 7.1 Hz, H-2′), 2.84 (2H, br t,
H-3′); 13C NMR (DMSO-d6 + traces of TFA, 90 MHz) δ
51.5 (t, C-2/6), 21.7 (t, C-3/5), 20.9 (t, C-4), 52.4 (t, C-1′),
After collection, the sponge was immediately frozen
at -25 °C. The freeze-dried sponge (3.63 g) was then
extracted with EtOAc-MeOH (1:1) to give a brown gum
(0.38 g). The crude gum was divided among different
solvents.8 The CHCl3 fraction and the n-BuOH fraction
(each separately) were chromatographed on RP-18
column several times, eluted with a MeOH-H2O gradi-

284 J ournal of Natural Products, 1998, Vol. 61, No. 2
Notes
20.9 (t, C-2′), 35.9 (t, C-3′); EIMS; m/z (%) [M]+ 142 (60),
100 (M+ - C2H4N, 15), 44 (C2H6N+, 100).
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1997, 60, 700-703.
(8) Kupchan, S. M. J . Org. Chem. 1977, 42, 2349-2357.
(9) Verpoorte, R. J . Nat. Prod. 1986, 49, 1-25.
Refer en ces a n d Notes
(10) Compounds
2 and 3 were synthesized as described in the
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Hopper, J . N. A. Tetrahedron 1996, 52, 9111-9120.
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1988, 110, 965-966.
(3) Fahy, E.; Molinski, T. F.; Harper, M. K.; Sullivan, B. W.;
Faulkner, D. J . Tetrahedron 1988, 29, 3427-3428.
(4) Fusetani, N.; Yasumuro, K.; Matsunaga, S. Tetrahedron Lett.
1989, 30, 6891-6894.
(5) Sakai, R.; Kohmoto, S.; Higa, T. Tetrahedron Lett. 1987, 28,
5493-5496.
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NP970442X