(2R,3R,7Z)-2-Aminotetradec-7-ene-1,3-diol, A new amino alcohol from the caribbean sponge Haliclona vansoesti

Article abstract of DOI:10.1021/np000081c

The Caribbean marine sponge Haliclona vansoesti was found to contain a high amount (5% dry wt) of a new analogue of 4-sphingenine, (2R,3R,7Z)-2-aminotetradec-7-ene-1,3-diol (1). Its structure was determined by detailed spectroscopic analysis. The relative configuration was deduced from the NMR data of the corresponding acetonide 5, while the absolute configuration was secured via protection of the primary alcohol and amino groups, and esterification of the secondary alcohol with Mosher's reagent.

Full text of DOI:10.1021/np000081c

978
J . Nat. Prod. 2000, 63, 978-980
(2R,3R,7Z)-2-Am in otetr a d ec-7-en e-1,3-d iol, a New Am in o Alcoh ol fr om th e
Ca r ibbea n Sp on ge Ha liclon a va n soesti
C. Devijver,† M. Salmoun,† D. Daloze,† J . C. Braekman,*,† W. H. De Weerdt,‡ M. J . De Kluijver,‡ and R. Gomez‡
Laboratory of Bio-organic Chemistry, Department of Organic Chemistry, Faculty of Sciences, CP 160/ 07,
University of Brussels, 50 Avenue F.D. Roosevelt, B-1050 Brussels, Belgium, and Institute for Systematics and
Population Biology, Zoologisch Museum, University of Amsterdam, P.O. Box 94766, 1090 GT Amsterdam, The Netherlands
Received February 14, 2000
The Caribbean marine sponge Haliclona vansoesti was found to contain a high amount (5% dry wt) of a
new analogue of 4-sphingenine, (2R,3R,7Z)-2-aminotetradec-7-ene-1,3-diol (1). Its structure was deter-
mined by detailed spectroscopic analysis. The relative configuration was deduced from the NMR data of
the corresponding acetonide 5, while the absolute configuration was secured via protection of the primary
alcohol and amino groups, and esterification of the secondary alcohol with Mosher’s reagent.
Ta ble 1. NMR Data of Compounds 1 and 2 (CDCl3, 600 and
150.87 MHz, J in Hz)
In our screening for biologically active and significant
metabolites from sponges, the CH2Cl2-soluble fraction of
the MeOH extract of the Caribbean sponge Haliclona
vansoesti n. sp. (Haposclerida, Chalinidae) was found to
be toxic against nauplii of the brine shrimp Artemia salina
(LD50 ) 35 mg/L). In this paper we report the structure
determination, including the absolute configuration, of the
major compound [1, (2R,3R,7Z)-2-aminotetradec-7-ene-1,3-
diol] of this toxic fraction. The amino alcohol 1 represents
about 5% of the dry weight of the sponge and was isolated
as a translucent lac after two successive chromatographies
of the CH2Cl2 extract on Si gel.
1
2
position
δC
δH
δC
δH
5.61, br d, 10
(CH3CONH)HC-2
(CH3COO)H2C-1
(CH3COO)HC-3
(CH3CONH)HC-2
HC-8
HC-7
HC-3
H2C-1
HC-2
H2C-12
H2C-4
H2C-10
H2C-11
H2C-9
H2C-6
H2C-5
(CH3CONH)HC-2
H2C-13
171.4
171.1
170.6
131.3 5.34, m
129.6 5.31, m
69.9 3.75, m
60.8 3.88; 3.73, m
58.7 3.25, m
32.5 1.25, m
34.0 1.48; 1.52, m
30.4 1.30, m
29.7 1.25, m
28.0 2.00, m
27.6 2.02, m
26.1 1.53, m
131.5 5.36, m
129.3 5.27, m
72.9 5.07, m
64.0 4.03, m
50.8 4.39, m
32.4 1.25, m
31.5 1.56; 1.60, m
30.3 1.32, m
29.7 1.25, m
27.9 1.97, m
27.4 2.02, m
25.9 1.35, m
23.9 2.00, s
23.3 1.25, m
21.6 2.07, s
21.4 2.04, s
14.8 0.87, t, 7
HREIMS of compound 1 gave a molecular ion at m/z
243.2190, while CIMS showed a (M + H)+ quasimolecular
ion at m/z 244 as the major ion. This indicated the formula
C
14H29NO2 (calcd 243.2198) for 1. The HREIMS showed
also fragment ions at m/z 226.2168 (C14H28NO, calcd
226.2171) and 212.2011 (C13H26NO, calcd 212.2014) cor-
responding to the loss, from the molecular ion, of HO and
CH3O, respectively. Moreover, a large IR band spreading
out from 3300 to 3100 cm-1, together with the formation
23.3 1.25, m
(CH3COO)HC-3
(CH3COO)HC-1
H3C-14
of the triacetyl compound 2 (νCdO at 1742 and 1659 cm-1
;
1H and 13C NMR data in Table 1) indicated, the presence
in 1 of one secondary and one primary hydroxyl group, and
of one CHNH2 group. From the 1H and 13C NMR data it
could also be deduced that the remaining carbon atoms of
1 consisted of one terminal methyl group, one disubstituted
double bond, and eight methylene groups. The two alcohols
and the primary amine could be readily juxtaposed as
represented in 1 based on the COSY data, while a cis
configuration was assigned to the double bond based on
the 13C chemical shifts (28.0 and 27.6 for 1 and 27.9 and
27.4 for 2) of the adjacent methylenes.1 The position of the
double bond was established by an HMBC experiment.
Indeed, clear long-range correlations were observed for 1
and 2 between H-3 and C-4 and C-5, as well as between
H-7 and C-5 and C-6. The location of the double bond was
further confirmed by treating triacetate 2 with dimethyl
disulfide and a catalytic amount of iodine.2 The EIMS of
the resulting derivative 3 showed two characteristic frag-
ment ions at m/z 318 and 145 Da, compatible with the
cleavage of the C8-C7 bond. In addition, the detailed
analysis of the 1D and 2D NMR spectra (1H-1H COSY,
14.8 0.87, t, 7
HMQC, HMBC) of compounds 1 and 2 led to the assign-
ments reported in Table 1 and to the conclusion that the
structure of the natural compound is (7Z)-2-aminotetradec-
7-ene-1,3-diol.
1
The relative configuration of 1 was deduced from the H
NMR spectrum of acetonide 5 prepared from diol 4 as
1
described in Scheme 1. Indeed, the H-1H COSY spectrum
of 5 permitted the signals of H2-1, H-2, H-3, and NH (Table
2) to be readily assigned. Moreover, the measured coupling
constants were only compatible with the preferred confor-
mation 9 for acetonide 5, corresponding to a threo config-
uration for 1. On the contrary, the equivalent coupling
constants reported by Mancini et al.3 for the preferred
conformation 10, corresponding to the erythro configuration
of an analogue of compound 1, are very different. The threo
configuration for 1 was further confirmed by NOE differ-
ence experiments on 5. Irradiation of Heq-1 (δ 3.71)
produced an enhancement to Hax-1 and H-2, while irradia-
tion of Hax-1 (δ 4.05) produced an enhancement to Heq-1,
H-2, and H-3.
* To whom correspondence should be addressed. Tel.: 32.02.6502961.
Fax: 32.02.6502798. E mail: braekman@ulb.ac.be.
† University of Brussels.
The absolute configuration of compound 1 was deter-
mined by preparing both Mosher’s esters4,5 7 and 8 of the
silyl ether 6 derived from diol 4 (Scheme 1). Positive ∆δ
‡ University of Amsterdam.
10.1021/np000081c CCC: $19.00
© 2000 American Chemical Society and American Society of Pharmacognosy
Published on Web 06/28/2000

Notes
J ournal of Natural Products, 2000, Vol. 63, No. 7 979
Sch em e 1a
a
(a) MeOH, Na2CO3, 1 h, room temperature; (b) acetone, CuSO4, 8 h,
reflux; (c) tert-butylchlorodiphenylsilane, pyridine, 24 h, room temperature;
(d) (R)-MTPACl, pyridine, CCl4, 24 h, room temperature; (e) (S)-MTPACl,
pyridine, CCl4, 24 h, room temperature.
Ta ble 2. Partial 1H NMR Data of 5 (CDCl3, 600 MHz)
position
δH
multiplicity
J
H
H
H-2
H-3
NH
eq-1
ax-1
3.71
4.05
3.86
3.93
6.15
dd
dd
dddd
m
br d
12.0, 1.8
12.0, 2.0
9.5, 1.8, 2.0, 2.0
MHz, respectively, using a Varian Unity 600 instrument. Some
1H NMR spectra were recorded at 250 MHz on a Bruker WM
250 spectrometer using TMS as internal standard. The IR
spectra were obtained on a Bruker IFS 25 instrument as a
film on a NaCl disk. The optical rotations were measured on
a Perkin-Elmer 141 polarimeter (Na-vapor lamp) in a 10-cm
cell at room temperature. Thin-layer chromatography (TLC)
analyses were performed on 0.25-mm Polygram Si gel SILG/
UV254 precoated plates (Macherey Nagel) and column chro-
matographies over Si gel (MN Kieselgel 0.04-0.063 mm), using
the flash technique.
An im a l Ma ter ia l. The sponge consists of thick cushions,
with a loose, cavernous structure with large, circular to
elliptical oscula on slightly raised elevations, with raised,
transparent rims. The surface is smooth, and the consistency
crisp and fragile. Characteristically, the choanosome is white,
and the ectosome light purple and semitransparent. The
ectosomal skeleton is a delicate, tangential, subisotropic
reticulation, loosely lying on the choanosomal skeleton, which
is also a subisotropic reticulation of a denser structure than
the ectosome, but with many subectosomal and choanosomal
spaces. The spicula are slightly curved, hastate oxeas, 120-
220 × 3.5-10.5 µm. The specimens were collected in May 1998,
off Curac¸ao, on reef-slope localities, growing on dead corals at
37-52 m depth. This material was assigned to a new species,
Haliclona vansoesti, recently described by De Weerdt et al.10
The species belongs to the subgenus Halichoclona of the genus
Haliclona (class Demospongiae, order Haploscleridae, family
Chalinidae). It occurs in the Caribbean, where it was found
in coral-reef environments in Curac¸ao, St. Vincent, Martinique,
and J amaica at 2-52 m depth. The material is housed in the
Zoological Museum of the University of Amsterdam (ZMA),
catalogued as ZMA POR. 13391-95, voucher numbers 98/CU/
J UN04/MK/124, 125, 144, 181, and 191.
9.5
(δS - δR) were observed for some methylenes of the
hydrocarbon chain, while significant negative values were
observed for H2C-1 and NH, indicating the (R)-configura-
tion at C-3. Because the threo configuration was established
between C-2 and C-3, the absolute configuration of 1 is thus
2R,3R. Compound 1 was found to be toxic against nauplii
of the brine shrimp A. salina (LD50 ) 9 mg/L) and can thus
be considered as responsible, at least in part, of the toxicity
of the sponge.
Structurally, compound 1 is related to the sphingosine
derivatives, such as 4-sphingenine (11), sphinganine, and
phytosphingosine, long known as central structural ele-
ments of the sphingolipids, which are important constitu-
ents of the lipid portion of the cell membranes in all groups
of organisms. More recently, several sphingosine deriva-
tives have been isolated from marine organisms as second-
ary metabolites. Examples of these metabolites are the
crucigasterins from the tunicate Pseudodistoma cru-
cigaster,6 the coriacenins from the sponge Clathrina coria-
cea,7 and the epimeric aliphatic amino alcohols, (2S,3S)-
and (2S,3R)-2-aminotetradeca-5,7-dien-3-ol, from the sponge
Xestospongia sp.8 By analogy with the biosynthesis of
4-sphingenin (11),9 we may postulate that the formation
of (2R,3R,7Z)-2-aminotetradec-7-ene-1,3-diol (1) requires a
C12 fatty acid and L-serine. But, as compounds 1 and 11
differ by their configuration at C-3, we must postulate that
the reduction of the intermediary ketones proceeds along
diastereomeric pathways.
Extr a ction , Isola tion , a n d Sp ectr a l P r op er ties. Speci-
mens of H. vansoesti (38 g dry wt) stored in MeOH were
exhaustively extracted with MeOH. The MeOH extract was
evaporated in vacuo and the residue (23 g) partitioned between
H2O and CH2Cl2. The organic phase was evaporated to dryness
Exp er im en ta l Section
Gen er a l Exp er im en ta l P r oced u r es. HREIMS were per-
1
formed on a Micromass Autospec 3F instrument. The H and
13C NMR spectra were recorded in CDCl3 at 600 and 150.87

980 J ournal of Natural Products, 2000, Vol. 63, No. 7
Notes
in vacuo to obtain a gum (5.5 g). Part of this gum (0.44 g) was
flash chromatographed over a Si gel column using as eluent
the mixture CH2Cl2/MeOH (98:2 to 70:30). The fraction
containing the major compound (visualized by TLC by spraying
with Dragendorff’s reagent) was further flash chromato-
graphed over a Si gel column using as eluent the mixture
hexane/acetone/NH4OH (80:20:0.5). This led to (2R,3R,7Z)-2-
aminotetradec-7-ene-1,3-diol (1; 160 mg; 5.26% dry wt) as a
syringed dropwise tert-butylchlorodiphenylsilane (50 µL, 1.3
equiv), and the mixture was stirred for 24 h at room temper-
ature under a nitrogen atmosphere. The solution was evapo-
rated to dryness and then diluted with ether (15 mL). The
ether solution was washed successively with saturated KHSO4,
water, and brine and dried over Na2SO4. After filtration and
evaporation of the solvent, the solid residue was chromato-
graphed over Si gel (eluent, CH2Cl2 with increasing amount
of MeOH) to give compound 6 (33 mg, yield 44%): amorphous
translucent lac homogeneous in TLC: [R]20
19.7° (c 0.46,
589
CHCl3); IR (film) broad band between 3300 and 3100 cm-1
;
solid; IR (film) 3340, 1649 cm-1; H NMR (CDCl3, 250 MHz)
1
1H and 13C NMR, see Table 1; HMBC correlations [δH (δC)]
5.34 (30.4, 28.0, 27.6), 5.31 (28.0, 27.6, 26.1), 3.88/3.73 (69.9,
58.7), 3.75 (58.7, 34.0, 26.1), 3.25 (69.9, 60.8), 2.02 (131.3,
129.6, 34.0, 26.1), 2.00 (131.3, 129.6, 30.4), 0.87 (32.5, 23.3);
HREIMS m/z 244.2275 (4, [M+H]+, calcd for C14H30NO2,
244.2276), 243.2190 (1, M+, calcd for C14H29NO2, 243.2198),
226.2168 (2, calcd for C14H28NO, 226.2171), 212.2011 (17, calcd
for C13H26NO, 212.2014), 60 (100); CIMS m/z 244 [M+H]+.
Acetyla tion of 1. Compound 1 (20 mg) was treated at room
temperature during 24 h with a 1:1 mixture of Ac2O and
pyridine (1 mL). After addition of water (2 mL) and evapora-
tion to dryness in vacuo, the solid residue was purified by flash
chromatography over a Si gel column using the mixture
hexane/acetone (8:2), affording triacetate 2 (15 mg): amorphous
solid homogeneous in TLC and GC (OV1 capillary column, T
7.7-7.3 (10H, m), 6.03 (1H, d, J ) 8 Hz), 5.33 (2H, m), 4.00
(1H, m), 3.86 (3H, m), 2.03 (4H, m), 1.94 (3H, s), 1.07 (9H, s),
0.88 (3H, t, J ) 7 Hz); EIMS m/z 523 (1, M+), 480 (8), 466
(79), 454 (12), 448 (14), 388 (27), 284 (27), 240 (19), 199 (100),
180 (19), 135 (31).
P r ep a r a tion of th e Mosh er ’s Ester s of 6. Batches of (R)-
MTPACl and (S)-MTPACl were prepared starting from the
corresponding commercial acids (S)-MTPA (50 mg) and (R)-
MTPA (50 mg), respectively, using the procedure described
previously.5 To a solution of (R)-MTPACl in freshly distilled
pyridine (300 µL) and dry CCl4 (300 µL) was added a solution
of 6 (16 mg) in the same mixture of solvent (300 µL). The
resulting solution was stirred at room temperature under a
nitrogen atmosphere for 24 h. After addition of water (5 mL),
the aqueous solution was extracted with CH2Cl2 (3 × 5 mL),
the organic phase was evaporated to dryness, and the solid
residue was chromatographed over Si gel (eluent, hexane with
increasing amount of EtOAc) to give the (S)-MTPA ester 7 (8
mg, yield 53%). The corresponding (R)-MTPA ester 8 was
prepared following the same procedure but starting from (S)-
MTPACl.
1
) 220°); IR (film) 3295, 1742, 1659, 1369 and 1235 cm-1; H
and 13C NMR, see Table 1; HMBC correlations [δH (δC)] 5.61
(170.6, 50.8), 5.36 (30.3, 27.9), 5.27 (25.9, 27.4), 5.07 (171.1,
64.0, 31.5, 25.9), 4.39 (170.6, 72.9, 64.0, 31.5), 4.03 (171.4, 72.9,
50.8), 2.07 (171.1, 72.9), 2.04 (171.4, 64.0), 2.02 (131.5, 129.3,
31.5, 25.9), 2.00 (170.6, 50.8), 1.97 (131.5, 129.3, 30.3), 1.56
(72.9, 50.8, 27.4, 25.9), 1.35 (72.9, 31.5, 27.4), 1.32 (29.7), 0.87
(32.4, 23.3); EIMS m/z 369 (21, M+), 309 (17), 224 (30), 144
(40), 112 (46), 102 (100).
Deter m in a tion of Dou ble-Bon d P osition . A hexane
solution (350 µL) of triacetate 2 (0.3 mg) was treated with 500
µL of DMDS and ethereal iodine (3 mg iodine in 200 µL Et2O)
in a sealed microreactor vial. The reaction mixture was kept
at room temperature for 20 h and then diluted with hexane
(500 µL). Iodine was removed by shaking with 10-1 M Na2S2O3.
The organic phase was evaporated to dryness, yielding the
DMDS adduct 3 that was dissolved in hexane (250 µL) and
analyzed by GC-MS: EIMS m/z 463 (2, M+), 416 (4), 391 (3),
368 (3), 318 (7), 258 (18), 165 (17), 145 (27), 102 (54), 84 (57),
81 (54), 69 (93), 55 (100).
1
Com p ou n d 7: H NMR (CDCl3, 250 MHz) 7.7-7.3 (10H,
m), 5.52 (H-3, m), 5.36/5.29 (H-7 and H-8, m), 5.27 (NH, d, J
) 8 Hz), 4.27 (H-2, m), 3.54 (H-1a, dd, J ) 10, 5 Hz), 3.40 (H-
1b, dd, J ) 10, 7 Hz), 3.47 (OCH3, s), 1.80 (COCH3, s), 1.06
(9H, s), 0.87 (3H, t, J ) 7 Hz); EIMS m/z 729 (1,M+), 696 (7),
682 (67), 670 (6), 448 (100), 240 (26), 199 (60), 189 (39), 135
(26).
1
Com p ou n d 8: H NMR (CDCl3, 250 MHz) 7.7-7.3 (10H,
m), 5.47 (H-3, m), 5.46 (NH, d, J ) 8 Hz), 5.34/5.23 (H-7 and
H-8, m), 4.27 (H-2, m), 3.66 (H-1a, dd, J ) 10, 5 Hz), 3.53 (H-
1b, dd, J ) 10, 7 Hz), 3.46 (OCH3, s), 1.79 (COCH3, s), 1.08
(9H, s), 0.88 (3H, t, J ) 7 Hz); EIMS identical to that of 7.
Ack n ow led gm en t. This research was supported by the
European Community (Project MAS3-CT97-0144) and the
National Fund for Scientific Research of the French Com-
munity of Belgium. We thank Dr. M. Luhmer for the NMR
spectra and Mr. C. Moulard for the mass spectra.
Selective Hyd r olysis of 2. To a solution of triacetate 2
(60 mg) in absolute MeOH (1 mL) was added anhydrous Na2-
CO3 (20 mg). The mixture was stirred at room temperature
during 1 h. Then, the solution was filtered, the solvent
evaporated, and the solid residue chromatographed over Si gel
(eluent, CH2Cl2 with increasing amount of MeOH) to give diol
4 (38 mg; yield 82%): amorphous solid; IR (film) 1652 cm-1
;
Refer en ces a n d Notes
1H NMR (CDCl3, 250 MHz) 6.35 (1H, d, J ) 8 Hz), 5.34 (2H,
m), 3.90 (2H, m), 3.78 (2H, m), 2.04 (3H, s), 2.00 (4H, m), 1.60-
1.20 (12H, m), 0.88 (3H, t, J ) 7 Hz); EIMS m/z 285 (6, M+),
254 (12), 236 (13), 212 (10), 194 (13), 102 (27), 85 (100).
Aceton id e 5. To the monoacetate 4 (13 mg) dissolved in
anhydrous acetone was added anhydrous CuSO4 (25 mg). The
solution was refluxed for 8 h, filtered, and evaporated to
dryness. The resulting solid residue was chromatographed over
florisil (eluent, hexane with increasing amount of acetone) to
give acetonide 5 (7 mg, yield 47%): amorphous solid; 1H NMR
(CDCl3, 600 MHz) 6.15 (1H, br d, J ) 9.5 Hz), 5.32 (2H, m),
4.05 (1H, dd, J ) 12, 2 Hz), 3.93 (1H, m), 3.86 (1H, dddd, J )
9.5, 1.8, 2, 2 Hz), 3.71 (1H, dd, J ) 12, 1.8 Hz), 2.03 (3H, s),
2.00 (4H, m), 1.46 (3H, s), 1.41 (3H, s), 0.87 (3H, t, J ) 7 Hz);
EIMS m/z 325 (1, M+), 310 (14), 267 (21), 143 (6), 130 (10), 85
(100).
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Selective P r otection of th e P r im a r y Alcoh ol of 4. To a
cold (0 °C) solution of 4 (41 mg) in dry pyridine (1 mL) was
NP000081C