Isolation and absolute configuration determination of aliphatic sulfates as the Daphnia kairomones inducing morphological defense of a phytoplankton - Part 2

Article abstract of DOI:10.1248/cpb.56.129

4,8-Dimethylnonyl sulfate (1) and 3-methyl-4E-decenyl sulfate (2) were isolated from Daphnia pulex as the Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii var. heterospina (NIES-802). The absolute configuration at C4 of 1 was determined by Ohrui's method applied to alcohol 3. The absolute stereochemistry at C3 of 2 was determined by ¹H-NMR analysis of the (R)-1NMA ester of alcohol 11.

Full text of DOI:10.1248/cpb.56.129

January 2008
Notes
Chem. Pharm. Bull. 56(1) 129—132 (2008)
129
Isolation and Absolute Configuration Determination of Aliphatic Sulfates
as the Daphnia Kairomones Inducing Morphological Defense of a
Phytoplankton—Part 2
Ko YASUMOTO,a Akinori NISHIGAMI,a Hiroaki AOI,a Chise TSUCHIHASHI,a Fumie KASAI,b
Takenori KUSUMI,a and Takashi OOI*,a
a Institute of Health Biosciences, The University of Tokushima Graduate School; Tokushima, Tokushima 770–8505, Japan:
and b National Institute for Environmental Studies; Onogawa, Tsukuba 305–8506, Japan.
Received October 3, 2007; accepted November 7, 2007; published online November 8, 2007
4,8-Dimethylnonyl sulfate (1) and 3-methyl-4E-decenyl sulfate (2) were isolated from Daphnia pulex as the
Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii
var. heterospina (NIES-802). The absolute configuration at C4 of 1 was determined by Ohrui’s method applied to
alcohol 3. The absolute stereochemistry at C3 of 2 was determined by 1H-NMR analysis of the (R)-1NMA ester of
alcohol 11.
Key words Daphnia kairomone; Scenedesmus; aliphatic sulfate; absolute configuration
It has been believed that phytoplankton is docile and never Jꢂ6.6 Hz, H-1) and twelve methine/methylene protons at d
resists its fate. Recently, it became clear that many phyto- 1.70—1.50. Interpretation of the 1H–1H COSY spectrum of 1
plankton resist their predators using various strategies. led to a gross structure as 4,8-dimethylnonyl sulfate. To the
Scenedesmus, a unicellular fresh-water phytoplankton, resists best of our knowledge, 1 is a new compound.
its grazer by changing its morphology. Addition of filtered
The absolute stereochemistry at C-4 of 1 was determined
1
medium of Daphnia, a grazer of the plankton, to unicellular by the H-NMR analysis of a (1R,2R)-2-(2,3-anthracenedi-
Scenedesmus subspicatus achieves morphological change carboximido)cyclohexanecarboxylic acid ((1R,2R)-2ACyclo-
into 2, 4, and 8 colonies within a few days. Such a change of COOH, Ohrui reagent4)) ester. The alcohol derivative 3 ob-
morphology increases resistance of the colonies against tained by hydrolysis of 1 with 3 M HCl, was treated with
grazer.1) This morphological change was supposed to be a (1S,2S)-Ohrui reagent to give the ester 4 (Chart 1). The au-
self-defense mechanism acquired by the phytoplankton and thentic (S)-methyl alcohol was synthesized by the reactions
triggered by a kairomone secreted from Daphnia. In this shown in Chart 2. Synthesis of the authentic samples started
manner, chemical signals play important roles in the interac- from (S)-citronellal 5 which was hydrogenated over Pd–C
tions among living organisms in aquatic environment. To cre- catalyst to give the aldehyde 6. The Wittig olefination of the
ate more accurate prey–predator interaction models and aldehyde 6 with (methoxy methyl)triphenylphosphonium
to advance the research on chemical communication in chloride gave the enolate intermediate, followed by hydroly-
aquatic ecological system, it is essential to identify the com- sis of the intermediate to the aldehyde 7. The aldehyde was
pounds. Recently, we reported identification of the Daphnia treated with NaBH4 to give 4(S),8-dimethylnonan-1-ol 4(S)-
kairomones that cause the morphological change in a unicel- 3. The (S)-alcohol was condensed with (1R,2R)- and (1S,2S)-
lular green alga Scenedesmus gutwinskii var. heterospina Ohrui reagent, to yield the respective esters 8 and 9.
(NIES-802) at 10ꢀ1—103 ng/ml concentrations.2,3)
The methyl proton signals of (1S,2S)-2ACyclo-COOH de-
Here we report isolation and absolute configuration deter-
mination of new aliphatic sulfates 1 and 2 as the Daphnia
kairomones. The absolute stereochemistries at C4 of 1 and
1
C3 of 2 were determined by H-NMR analysis of Ohrui’s
method4) applied to alcohol 3 and the (R)-methoxy-(1-naph-
thyl) acetic acid ((R)-1NMA) ester of alcohol 11, respec-
tively. Frozen Daphnia (10 kg; Aso Tropical Fish Co. Ltd.,
Osaka) was soaked with methanol (20 lꢁ3), and the
methanol solution was evaporated, the residue being treated
with water (9 l). The mixture was successively extracted with
hexane, dichloromethane, and butanol, and the most active
butanol extract was separated by HPLC monitoring the activ-
ity to afford 1 (2.0 mg) and 2 (0.8 mg) (Fig. 1).
Fig. 1. The Structure of Daphnia Kairomones 1 and 2
The countercations were not identified and expressed as M.
The molecular formula of 1 was established as C11H23O4S
on the basis of HR-FAB-MS. The presence of a sulfate group
was suggested by a fragment ion peak at m/z 97 (HSOꢀ4 ) in
1
the negative ion FAB-MS of 1. The H-NMR spectrum of 1
exhibited three doublet methyls at d 0.93 (3H, d, Jꢂ6.1 Hz,
Me-4) and 0.92 (6H, d, Jꢂ6.6 Hz, H-9 and Me-8), two pro-
tons of a methylene bearing a sulfate group at d 4.02 (2H, t, Chart 1. Synthesis of (1S,2S)-2-ACyclo-COOH Ester 4
∗ To whom correspondence should be addressed. e-mail: tooi@ph.tokushima-u.ac.jp
© 2008 Pharmaceutical Society of Japan

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Vol. 56, No. 1
Chart 3. Synthesis of (R)-1NMA Ester 12
Chart 2. Synthesis of (1R,2R)-2-ACyclo-COOH Ester 8 and (1S,2S)-2-
ACyclo-COOH Ester 9
Chart 4. Synthesis of (R)-1NMA Ester 17 and (S)-1NMA Ester 18
Fig. 2. Determination of the Absolute Configuration of 1
rivative of compound 1 (4) appeared at d 0.78 (6H, d, Jꢂ6.6
Hz, Me-8, H-9), 0.57 (3H, d, Jꢂ6.4 Hz, Me-4). These chemi-
cal shifts are the same with those of the methyl protons of the
(1R,2R)-2ACyclo-COOH ester of 4(S),8-dimethylnonan-1-ol
8, leading to the 4(R)-configuration of compound 1 (Fig. 2).
The molecular formula of 2 was established as C11H21O4S
Fig. 3. Determination of the Absolute Configuration of 2
on the basis of HR-FAB-MS. The presence of a sulfate group alcohol 11 was esterified with (R)-1NMA to yield the (R)-
was suggested by a fragment ion peak at m/z 97 (HSOꢀ4 ) in 1NMA ester 12. The pattern of methyl protons was com-
1
the negative ion FAB-MS of 2. The H-NMR spectrum of 2 pared with those of the authentic samples synthesized by the
exhibited two olefinic protons at d 5.48 (1H, dtd, Jꢂ15.3, reactions shown in Chart 4. (S)-Citronellol 13 was converted
6.6, 1.0 Hz, H-5) and 5.30 (1H, ddt, Jꢂ15.3, 7.9, 1.2 Hz, H- by ozonolysis to a 1/1 mixture of aldehyde 147) and its hemi-
4), two protons of a methylene bearing a sulfate group at d acetal form 157) in 76% yield. The Wittig olefination of the
4.04 (2H, m, H-1), two methyl groups at d 1.04 (3H, d, Jꢂ mixture 14ꢃ15 with n-butyltriphenylphosphonium bromide
6.8 Hz, Me-3), 0.93 (3H, t, Jꢂ6.8 Hz, H-10) and eleven me- gave the alcohol 16 (Z/Eꢂ1/1) in 30% yield. Reduction of
1
thine/methylene protons at d 2.31—1.44. The H–1H COSY, the double bond under H2 atmosphere over the Pd–C catalyst
HSQC and HMBC NMR spectra of 2 were consistent with provided 3(S)-methyldecan-1-ol 3(S)-11. The alcohol was
the structure of 3-methyl-4-decenyl sulfate. The geometry of condensed with (R)- and (S)-1NMA, to yield the (R)-1NMA
the double bonds in 2 was deduced to be 4E from the under- ester 17 and (S)-1NMA ester 18.
lined coupling constants of the olefinic protons. To the best
of our knowledge, 2 is a new compound.
The methyl proton signals of (R)-1NMA ester of 11 de-
rived from natural 2 appeared at d 0.88 (3H, t, Jꢂ6.8 Hz)
The absolute stereochemistry at C-3 of 2 was determined and 0.64 (3H, d, Jꢂ6.6 Hz). These chemical shifts are the
1
by the H-NMR analysis of (R)-1NMA5,6) ester of 11, a hy- same with those of the methyl protons of the (S)-1NMA ester
drolysis product (Chart 3). The olefin of compound 2 of 3(S)-methyldecan-1-ol 18, leading to the 3(S)-configura-
(0.5 mg) was hydrogenated over Pd–C catalyst, followed by tion of compound 2 (Fig. 3).
hydrolysis of the sulfate 10 to an alcohol derivative 11. The

January 2008
131
Experimental
the filtrate was concentrated under reduced pressure. The enol ester obtained
was then dissolved in 2 ml of chloroform and 0.15 ml of 12 M HCl was
High-resolution MS were recorded on a JEOL JMS-SX102A spectrome-
ter and Waters LCT Premier. H- and 13C-NMR spectra were obtained on a added. The solution was stirred for 4 h at room temperature and the chloro-
Bruker Avance-400 (1H and 13C at 400 and 100 MHz, respectively). Assign- form was evaporated. Diethyl ester and water were added and the aqueous
ments of the proton and carbon signals were established by COSY, HSQC phase was extracted with diethyl ester (ꢁ2) and the combined organic layers
1
and HMBC spectra. Optical rotations were determined on a JASCO DIP-370
were dried over anhydrous magnesium sulfate and concentrated under
polarimeter. The structures of the compounds were established by COSY, reduced pressure. The residue was purified by flash chromatography eluting
HSQC, HMBC, and NOESY spectra. The countercation of natural sulfates
was not identified and expressed as Mꢃ.
with ethyl acetate : hexane (5 : 95) to yield 101 mg of the desired aldehyde 7
(0.59 mmol, 42%). H-NMR (CDCl3) d: 9.76 (1H, t, Jꢂ1.8 Hz, H-1), 2.41
(2H, m, H-2), 1.64 (1H, m, H-4), 1.51 (1H, m, H-8), 1.08—1.45 (8H, m, H-
1
Bioassay Each 200 ml of C medium of S. gutwinskii (5.0ꢁ102 cells/ml)
is delivered into the central 30—50 wells of 96-well polystyrene tissue cul- 3, 5, 6, 7), 0.87 (3H, d, Jꢂ5.4 Hz, Me-4), 0.86 (6H, d, Jꢂ6.6 Hz, H-9 and
ture plate (CELLSTAR, Greiner Bio-one Co., Ltd.) containing the test sam-
ples (1000—0.01 ng/ml), and the outer wells are filled with distilled water to
Me-8). [a]D25 ꢀ1.8° (cꢂ2.1, CHCl3).
4(S),8-Dimethylnonan-1-ol (4(S)-3) To a methanol solution of the
avoid dehydration of the system. The plate is covered with a plastic lid, and aldehyde 7 (65 mg, 0.38 mmol), sodium borohydride (29 mg, 0.77 mmol)
incubated at 20 °C (12 light/12 dark) for 10 d. A drop of the medium is was added. The reaction mixture was stirred for 3 h at room temperature,
placed on a Thoma’s hemacytometer, and the numbers of 1-, 2-, 4-, and 8- poured into water (20 ml), extracted with diethyl ether (20 mlꢁ3). The or-
cell types were counted under a microscope (ꢁ200). ganic layers were combined, dried over anhydrous Na2SO4, and concentrated
Extraction and Isolation Frozen Daphnia (10 kg; Aso Tropical Fish under reduced pressure to provide the desired alcohol 4(S)-3 (65 mg,
Co., Ltd., Osaka) was soaked with methanol (20 lꢁ3), and the methanol
0.38 mmol). 1H-NMR (CDCl3) d: 3.62 (2H, t, Jꢂ6.8 Hz, H-1), 1.60 (2H, m,
solution was evaporated, the residue being treated with water (9 l). The mix- H-2), 1.51 (1H, m, H-6), 1.07—1.42 (9H, m, H-3, 4, 5, 6, 7), 0.86 (3H, d,
ture was successively extracted with hexane (9 l), dichloromethane (9 l), Jꢂ6.3 Hz, Me-4), 0.86 (6H, d, Jꢂ6.6 Hz, H-9 and Me-8). 13C-NMR (CDCl3)
and butanol (9 l), and the most active butanol extract (18 g) was chro-
matographed on a Cosmosil 75C18-OPN (25 g), eluting with MeOH–H2O in
a gradient manner (1 : 1→10 : 0). The active fractions were further purified ꢀ1.3° (cꢂ3.2, CHCl3).
d: 63.5 (C-1), 39.4 (C-7), 37.3 (C-5), 33.0 (C-3), 32.7 (C-4), 30.4 (C-2),
28.0 (C-8), 24.8 (C-6), 22.8 and 22.7 (C-9 and Me-8), 19.7 (Me-4). [a]D25
by HPLC (CAPCELLPAK C18 column, 5 mm, 10ꢁ250 mm, MeCN–H2O
(40 : 60) containing 250 mM NaClO4 as mobile phase with the flow rate 1.0
ml/min using an RI detector) to afford 1 (2.0 mg), 2 (0.8 mg).
4(S),8-Dimethylnonyl (1R,2R)-2-(2,3-Anthracenedicarboximido)cyclo-
hexanecarboxylate (8) To a CH2Cl2 solution of the alcohol 4(S)-3 (1 mg,
5.8 mmol), were added EDC (3.3 mg, 17 mmol), DMAP (2.2 mg, 18 mmol),
4(R),8-Dimethylnonyl Sulfate (1) 1H-NMR (CD3OD) d: 4.02 (2H, t, NEt3 (1.9 ml, 26 mmol) and (1R,2R)-2-(2,3-anthracenedicarboximido)cyclo-
Jꢂ6.6 Hz, H-1), 1.70 (2H, m, H-2), 1.58 (1H, nonet, Jꢂ6.6 Hz H-8), 1.10—
hexanecarboxylic acid (0.4 mg, 1.0 mmol). After the mixture was stirred for
1.50 (9H, m, H-3, 4, 5, 6, 7), 0.93 (3H, d, Jꢂ6.1 Hz, Me-4), 0.92 (6H, d, Jꢂ 12 h at room temperature, the crude ester was purified by SiO2 column chro-
6.6 Hz, H-9 and Me-8). 13C-NMR (CD3OD) d: 69.5 (C-1), 40.5 (C-7), 38.4
matography with hexane/EtOAc solvent system to afford the ester 8 (0.5 mg,
(C-5), 34.2 (C-3), 33.8 (C-4), 29.2 and 28.1 (C-2, 8), 25.9 (C-6), 23.1 and
0.9 mmol). 1H-NMR (CDCl3) d: 8.61 (2H, s, anthracene), 8.47 (2H, s, an-
23.0 (C-9 and Me-8), 19.7 (Me-4). HR-FAB-MS (ꢀ): m/z 251.1331 (Calcd thracene), 8.07 (2H, dd, Jꢂ6.6, 3.4 Hz, anthracene), 7.61 (2H, dd, Jꢂ6.6,
for C11H23O4S: 251.1317).
3.4 Hz, anthracene), 4.44 (1H, dt, Jꢂ11.7, 3.8 Hz, cyclohexane C2-H), 3.87
3(S)-Methyl-4E-decenyl Sulfate (2) 1H-NMR (CD3OD) d: 5.48 (1H, (2H, t, Jꢂ6.8 Hz, –OCH2–), 3.51 (1H, dt, Jꢂ11.7, 3.6 Hz, cyclohexane C1-
dtd, Jꢂ15.3, 6.6, 1.0 Hz, H-5), 5.30 (1H, ddt, Jꢂ15.3, 7.9, 1.2 Hz, H-4), H), 2.32—0.80 (12H, m, –CH–, –CH2–), 0.78 (6H, d, Jꢂ6.6 Hz, Me-8, H-9),
4.04 (2H, m, H-1), 2.31 (1H, sept. Jꢂ7.1 Hz, H-3), 2.03 (2H, q. Jꢂ6.6 Hz,
H-6), 1.67 (2H, m, H-2), 1.28—1.44 (6H, m, H-7, 8, 9), 1.04 (3H, d, Jꢂ
0.57 (3H, d, Jꢂ6.4 Hz, Me-4).
4(S),8-Dimethylnonyl (1S,2S)-2-(2,3-Anthracenedicarboximido)cyclo-
6.8 Hz, Me-3), 0.93 (3H, t, Jꢂ6.8 Hz, H-10). HR-FAB-MS (ꢀ): m/z hexanecarboxylate (9) To a CH2Cl2 solution of the alcohol 4(S)-3 (1 mg,
249.1182 (Calcd for C11H21O4S: 249.1161). 5.8 mmol), were added EDC (6.7 mg, 35 mmol), DMAP (4.2 mg, 34 mmol),
4(R),8-Dimethylnonyl (1S,2S)-2-(2,3-Anthracenedicarboximido)cyclo- NEt3 (3.8 ml, 52 mmol) and (1S,2S)-2-(2,3-anthracenedicarboximido)cyclo-
hexanecarboxylate (4) Sulfate 1 (2.2 mg, 7.5 mmol) was dissolved in 3 M
HCl (0.5 ml) and the solution was heated at 120 °C for 5 h. Dichloromethane
hexanecarboxylic acid (1.2 mg, 3.2 mmol). After the mixture was stirred for
24 h at room temperature, the crude ester was purified by SiO2 column chro-
and water were added to the solution. The organic phase was dried over matography with hexane/EtOAc solvent system to afford the ester 9 (0.9 mg,
Na2SO4, and concentrated to give the alcohol 3. To a CH2Cl2 solution of
1.7 mmol). 1H-NMR (CDCl3) d: 8.61 (2H, s, anthracene), 8.47 (2H, s, an-
the alcohol, were added 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hy- thracene), 8.07 (2H, dd, Jꢂ6.6, 3.2 Hz, anthracene), 7.61 (2H, dd, Jꢂ6.6,
drochloride (EDC) (4.5 mg, 32 mmol), 4-dimethylaminopyridine (DMAP) 3.2 Hz, anthracene), 4.44 (1H, dt, Jꢂ11.7, 3.9 Hz, cyclohexane C2-H), 3.88
(2.8 mg, 23 mmol), NEt3 (2.6 ml, 48 mmol) and (1S,2S)-2-(2,3-anthracenedi- (2H, m, –OCH2–), 3.51 (1H, dt, Jꢂ11.7, 3.4 Hz, cyclohexane C1-H), 2.31—
carboximido)cyclohexanecarboxylic acid (0.4 mg, 1.0 mmol). After the mix- 0.80 (12H, m, –CH–, –CH2–), 0.77 (6H, dd, Jꢂ6.6, 1.5 Hz, Me-8, H-9), 0.61
ture was stirred for 12 h at room temperature, the crude ester was purified by
SiO2 column chromatography with hexane/EtOAc solvent system to afford
the ester 4 (1.4 mg). 1H-NMR (CDCl3) d: 8.61 (2H, s, anthracene), 8.47 (2H,
(3H, d, Jꢂ6.6 Hz, Me-4).
3(R)-Methyldecyl (R)-Methoxy-(1-naphthyl)acetate (12) The metha-
nol solution of 2 (0.5 mg, 1.8 mmol) was stirred with palladium carbon
s, anthracene), 8.07 (2H, dd, Jꢂ6.6, 3.4 Hz, anthracene), 7.61 (2H, dd, Jꢂ (10%) under H2 atmosphere. After 2 h stirring, the palladium carbon was re-
6.6, 3.4 Hz, anthracene), 4.44 (1H, dt, Jꢂ11.7, 3.8 Hz, cyclohexane C2-H), moved by filtration, and the filtrate was concentrated in vacuo to give satu-
3.87 (2H, t, Jꢂ6.8 Hz, 6.8, –OCH2–), 3.51 (1H, dt, Jꢂ11.7, 3.6 Hz, cyclo-
hexane C1-H), 2.32—0.80 (12H, m, –CH–, –CH2–), 0.78 (6H, d, Jꢂ6.6 Hz,
Me-8, H-9), 0.57 (3H, d, Jꢂ6.4 Hz, Me-4).
rated sulfate 10 (0.5 mg, quant.). The sulfate was dissolved in 3 M HCl
(0.5 ml) and the solution was heated at 120 °C for 3 h. Dichloromethane
(CH2Cl2) was added to the solution. The organic phase was dried over
3(S),7-Dimethyloctanal (6) The methanol solution of (S)-citronellal 5 Na2SO4 and concentrated to give the alcohol 11. To a CH2Cl2 solution
(216 mg, 1.4 mmol) was stirred with palladium carbon (20 mg, 10%) under (50 ml) of the alcohol 11 were added EDC (1.7 mg, 9 mmol), DMAP (1.1 mg,
H2 atmosphere. After 4 h stirring, the palladium carbon was removed by fil- 9 mmol), NEt3 (1.8 ml, 12 mmol) and (R)-methoxy-(1-naphthyl)acetic acid
tration, and the filtrate was concentrated in vacuo to give 6 (217 mg, 99%). (1NMA) (1.0 mg, 5 mmol). The mixture was allowed to stand at room tem-
1H-NMR (CDCl3) d: 9.74 (1H, dd, Jꢂ2.0, 2.4 Hz, H-1), 2.38 (1H, ddd, Jꢂ perature for 48 h, and the crude ester was purified by SiO2 column chro-
16.0, 5.8, 2.0 Hz, H-2), 2.21 (1H, ddd, Jꢂ16.0, 7.8, 2.4 Hz, H-2), 2.03 (1H, matography with hexane : EtOAc (9 : 1) solvent system to afford the (R)-
1
m, H-3), 1.52 (1H, nonet, Jꢂ6.6 Hz, H-7), 1.10—1.38 (6H, m, H-4, 5, 6), 1NMA ester 12 (0.3 mg, 1.3 mmol, 70%). H-NMR (CDCl3) d: 8.27 (1H, d,
0.95 (3H, d, Jꢂ6.8 Hz, Me-3), 0.86 (6H, d, Jꢂ6.6 Hz, H-8 and Me-7). 13C-
NMR (CDCl3) d: 202.4, 50.9, 38.9, 37.0, 28.0, 27.8, 24.6, 22.5, 22.4, 19.8.
Jꢂ8.0 Hz), 7.84 (1H, t, Jꢂ9 Hz), 7.60 (1H, d, Jꢂ7.1 Hz), 7.49 (3H, m), 5.36
(1H, s), 4.12 (2H, m), 3.45 (3H, s), 1.12—1.60 (15H, m), 0.88 (3H, t, Jꢂ
4(S),8-Dimethylnonanal (7) To a suspension of (methoxymethyl)triph- 6.8 Hz), 0.64 (3H, d, Jꢂ6.6 Hz). HR-EI-MS: m/z 370.2491 (Calcd for
enylphosphonium chloride (960 mg, 2.8 mmol) in THF (4 ml), cooled at
0 °C, was added 1.6 M solution of n-BuLi in hexane (1.75 ml, 2.8 mmol). The
red solution was stirred 30 min at 0 °C and 6 (217 mg, 1.4 mmol) was added.
The reaction mixture was stirred for 12 h at room temperature and then
quenched with 1 M HCl, extracted with diethyl ether (ꢁ3), dried over anhy-
drous magnesium sulfate and concentrated partially under reduced pressure.
C24H34O3: 370.2508).
6-Hydroxy-4-methylhexanal
1.7 mmol) in CH2Cl2 (15 ml) was treated with ozone at ꢀ78 °C. Then
913 mg (3.5 mmol) of triphenylphosphine was added to the solution. After
stirring for 4 h at room temperature, H2O was added, and the mixture was
extracted with ether. The organic layer was dried over Na2SO4, concentrated
(14) (S)-Citronellol
13
(272 mg,
The residue was filtered to remove the solid triphenylphosphine oxide and in vacuo and purified by flash chromatography on silica gel, which gave a

132
Vol. 56, No. 1
mixture (2/1) of 14 and its hemiacetal form 15 (191 mg, 76%). 14: 1H-NMR
(CDCl3) d: 9.76 (1H, t, Jꢂ1.7 Hz), 3.62—3.73 (2H, m), 2.47 (1H, dddd, Jꢂ
1.7, 6.3, 8.5, 17.3 Hz), 2.43 (1H, dddd, Jꢂ1.7, 6.7, 8.4, 17.3 Hz), 1.35—1.74
(5H, m), 0.89 (3H, d, Jꢂ6.2 Hz). 13C-NMR (100 MHz, CDCl3) d: 202.6,
60.7, 41.6, 39.4, 29.1, 28.8, 19.4; hemiacetal 15: 1H-NMR (400 MHz,
CDCl3) d: 5.14 (1H, dd, Jꢂ5.3, 9.2 Hz), 3.90 (1H, bt, Jꢂ12.8 Hz), 3.53 (1H,
dt, Jꢂ12.8, 3.4 Hz), 1.30—1.74 (7H, m), 0.91 (3H, d, Jꢂ6.2 Hz). 13C-NMR
(CDCl3) d: 96.5, 60.2, 39.2, 36.3, 34.0, 30.9, 23.2.
3(S)-Methyl-6-hexcen-1-ol (16) 1.6 M solution of n-BuLi in hexane
(4.9 ml, 7.8 mmol) was added dropwise to a suspension of n-butyltriph-
enylphosphonium bromide (2.5 g, 7.8 mmol) in THF (10 ml). The mixture
was stirred at ꢀ30 °C for 20 min, cooled at ꢀ78 °C and a solution of 14 and
15 (224 mg, 1.6 mmol) in THF (3 ml) was added. The mixture was stirred at
the same temperature for 2 h, poured into water, and extracted with diethyl
ether. The organic layer was dried over Na2SO4. After concentration, the
crude product was purified by flash chromatography to give the alcohol 16
(Z/Eꢂ1/1) (80 mg, 30% yield). 1H-NMR (CDCl3) d: 5.28—5.38 (4H, m, H-
6, 7), 3.63 (4H, m, H-1), 1.98 (8H, m, H-5, 8), 1.56 (2H, m, H-3), 1.10—
1.40 (12H, m, H-2, 4, 9), 0.87 (6H, t, Jꢂ6.6 Hz, H-10), 0.86 (6H, d,
Jꢂ6.8 Hz, Me-3). 13C-NMR (CDCl3) d: 130.2, 130.0, 129.8 and 129.5 (C-6,
7), 60.9 (C-1), 39.8 (C-2), 37.1, 37.0 (C-4), 34.7 (trans C-8), 30.0, 29.3,
29.2 and 29.0 (trans C-5 and 3, cis C-8 and 3), 24.7 (cis C-5), 22.9 and 22.7
(C-9), 19.5 (Me-3), 13.8 and 13.6 (C-10).
purified by SiO2 column chromatography with CH2Cl2 solvent system to af-
ford the (S)-1NMA ester 17 (1.5 mg, 4.1 mmol, 70%). H-NMR (CDCl3) d:
8.28 (1H, d, Jꢂ8.2 Hz), 7.84 (1H, t, Jꢂ8.3 Hz), 7.60 (1H, d, Jꢂ7.1 Hz), 7.49
(3H, m), 5.36 (1H, s), 4.12 (2H, t, Jꢂ6.6 Hz), 3.45 (3H, s), 1.12—1.60
(15H, m), 0.88 (3H, t, Jꢂ6.8 Hz), 0.70 (3H, d, Jꢂ6.6 Hz). HR-EI-MS: m/z
370.2491 (Calcd for C24H34O3: 370.2508).
1
3(S)-Methyldecyl (S)-Methoxy-(1-naphthyl)acetate (18) To a CH2Cl2
solution (50 ml) of 3(S)-11 (1 mg, 5.8 mmol) were added EDC (6.7 mg,
35 mmol), DMAP (4.3 mg, 35 mmol), NEt3 (7.3 ml, 52 mmol) and (S)-
methoxy-(1-naphthyl)acetic acid (1NMA) (3.8 mg, 17 mmol). After the mix-
ture was allowed to stand for 12 h at room temperature, the crude ester was
purified by SiO2 column chromatography with CH2Cl2 solvent system to af-
1
ford the (S)-1NMA ester 18 (0.6 mg, 2.8 mmol, 48%). H-NMR (CDCl3) d:
8.27 (1H, d, Jꢂ8.0 Hz), 7.84 (1H, t, Jꢂ8.9 Hz), 7.60 (1H, d, Jꢂ7.1 Hz), 7.49
(3H, m), 5.36 (1H, s), 4.12 (2H, m), 3.45 (3H, s), 1.12—1.60 (15H, m), 0.88
(3H, t, Jꢂ6.8 Hz), 0.64 (3H, d, Jꢂ6.6 Hz). HR-EI-MS: m/z 370.2491 (Calcd
for C24H34O3: 370.2508).
Acknowledgments We are grateful to Dr. K. Akasaka and Prof. H.
Ohrui of the Graduate School of Life Sciences, Tohoku University for pro-
viding us Ohrui reagents.
References
1) Hessen D. O., van Donk E., Hydrobiologia, 127, 129—140 (1993).
2) Yasumoto K., Nishigami A., Yasumoto M., Kasai F., Okada Y.,
Kusumi T., Ooi T., Tetrahedron Lett., 46, 4765—4767 (2005).
3) Yasumoto K., Nishigami A., Kasai F., Kusumi T., Ooi T., Chem.
Pharm. Bull., 54, 271—274 (2006).
4) Imaizumi K., Terasima H., Akasaka K., Ohrui H., Anal. Sci., 19,
1243—1249 (2003).
5) Kusumi T., Takahashi H., Ping X., Fukushima T., Asakawa Y.,
Hashimoto T., Kan Y., Tetrahedron Lett., 35, 4397—4400 (1994).
6) Kusumi T., Takahashi H., Hashimoto T., Kan Y., Asakawa Y., Chem.
Lett., 6, 1093—1094 (1994).
3(S)-Methyldecan-1-ol (3(S)-11) The methanol solution of 16 (58 mg,
0.34 mmol) was stirred with palladium carbon (6 mg, 10%) under H2 atmo-
sphere. After 3 h stirring, the palladium carbon was removed by filtration,
and the filtrate was concentrated in vacuo to give 3(S)-11 (60 mg, quant.).
1H-NMR (CDCl3) d: 3.59 (2H, m, H-1), 1.50 (1H, m, H-3), 1.05—1.35
(14H, overlap, H-2, 4, 5, 6, 7, 8, 9), 0.79—0.84 (6H, overlap, C-9 and Me-
3). 13C-NMR (CDCl3) d: 60.8, 39.7, 37.1, 31.8, 29.8, 29.5, 29.3, 26.9, 22.6,
19.5, 14.0. [a]D25 ꢀ2.7° (cꢂ2.2, CHCl3).
3(S)-Methyldecyl (R)-Methoxy-(1-naphthyl)acetate (17) To a CH2Cl2
solution (50 ml) of 3(S)-11 (1 mg, 5.8 mmol) were added EDC (6.7 mg,
35 mmol), DMAP (4.3 mg, 35 mmol), NEt3 (7.3 ml, 52 mmol) and (S)-
methoxy-(1-naphthyl)acetic acid (1NMA) (3.8 mg, 17 mmol). After the mix-
ture was allowed to stand for 12 h at room temperature, the crude ester was
7) Pempo D., Cintrat J. C., Parrain J. L., Santelli M., Tetrahedron, 56,
5493—5497 (2000).