Identification and synthesis of (Z,Z)-8,11-heptadecadienyl formate and (Z)-8-heptadecenyl formate: Unsaturated aliphatic formates found in the unidentified astigmatid mite, Sancassania sp. Sasagawa (Acari: Acaridae)

Article abstract of DOI:10.3390/molecules21050619

We identified two aliphatic formates, (Z,Z)-8,11-heptadecadienyl formate and (Z)-8-heptad ecenyl formate in the opisthonotal gland secretions of an unidentified acarid species, namely Sancassania sp. Sasagawa. Both compounds were isolated using silica gel column chromatography and the structures were elucidated by ¹H-NMR and GC/FT-IR. Further information on the double bond positions was obtained by GC-MS analysis of the corresponding dimethyl disulfide derivatives. Based on the estimated structures of the two formates and using linoleic and oleic acids as the respective starting materials, a simple four-step synthesis was achieved via Barton decarboxylation as the key step. The aliphatic formates identified in acarids thus far are neryl formate ((Z)-3,7-dimethylocta-2,6-dienyl formate) and lardolure (1,3,5,7-tetramethyldecyl formate), and both have been reported to have pheromone functions. The biological function of the two formates isolated in this study is currently being investigated. Although we can speculate that the two compounds were biosynthesized from linoleic and oleic acid, there is a possibility that the synthetic processes featured a novel chain shortening and formic acid esterification mechanism.

Full text of DOI:10.3390/molecules21050619

molecules
Article
Identification and Synthesis of
(Z,Z)-8,11-Heptadecadienyl Formate and
(Z)-8-Heptadecenyl Formate: Unsaturated Aliphatic
Formates Found in the Unidentified Astigmatid Mite,
Sancassania sp. Sasagawa (Acari: Acaridae)
Nobuhiro Shimizu 1,*, Daisuke Sakata 1, Honami Miyazaki 1, Yasuhiro Shimura 2 and
Yasumasa Kuwahara 3,4
1
Faculty of Bioenvironmental Science, Kyoto Gakuen University, 1-1 Nanjo, Sogabe,
Kameoka 621-8555, Japan; d.sakata811@gmail.com (D.S.); kygf071220@yahoo.co.jp (H.M.)
Institute of Applied Biochemistry, The University of Tsukuba, 1-1-1 Tennodai, Tsukuba,
2
Ibaraki 305-8577, Japan; shimizu1973@hotmail.co.jp
Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University,
3
5180 Kurokawa, Imizu, Toyama 939-0398, Japan; kuwahara@pu-toyama.ac.jp
Asano Active Enzyme Molecule Project, JST, ERATO, Imizu, Toyama 939-0398, Japan
4
*
Correspondence: shimizu@kyotogakuen.ac.jp; Tel.: +81-771-29-3588; Fax: +81-771-29-3429
Academic Editor: Derek J. McPhee
Received: 12 April 2016; Accepted: 5 May 2016; Published: 11 May 2016
Abstract: We identified two aliphatic formates, (Z,Z)-8,11-heptadecadienyl formate and (Z)-8-heptad
ecenyl formate in the opisthonotal gland secretions of an unidentified acarid species, namely
Sancassania sp. Sasagawa. Both compounds were isolated using silica gel column chromatography
and the structures were elucidated by 1H-NMR and GC/FT-IR. Further information on the
double bond positions was obtained by GC-MS analysis of the corresponding dimethyl disulfide
derivatives. Based on the estimated structures of the two formates and using linoleic and oleic
acids as the respective starting materials, a simple four-step synthesis was achieved via Barton
decarboxylation as the key step. The aliphatic formates identified in acarids thus far are neryl formate
((Z)-3,7-dimethylocta-2,6-dienyl formate) and lardolure (1,3,5,7-tetramethyldecyl formate), and both
have been reported to have pheromone functions. The biological function of the two formates isolated
in this study is currently being investigated. Although we can speculate that the two compounds
were biosynthesized from linoleic and oleic acid, there is a possibility that the synthetic processes
featured a novel chain shortening and formic acid esterification mechanism.
Keywords: Sancassania sp. Sasagawa; mite; aliphatic formate; (Z,Z)-8,11-heptadecadienyl formate;
(Z)-8-heptadecenyl formate; Barton decarboxylation
1. Introduction
All hydrocarbons observed in the opisthonotal gland secretions of acarid mites are straight-chain
aliphatic compounds, and the chains are characteristically shorter than those of the hydrocarbons
found in insects [
some of these compounds are known as pheromones, many are secreted as protective materials to
act as solvents that control the evaporation of volatile compounds [ ]. Hydrocarbons form through
1]. Carbon chains between C13 and C17 are particularly prominent, and while
2
the elimination of the carboxyl group from fatty acids. (Z,Z)-6,9-Heptadecadiene, derived from
linoleic acid (LA), and (Z)-8-heptadecene, derived from oleic acid (OA) are detected in a high
proportion of acarid mites, yet there are almost no reports of their detection in insects [1]. As a
Molecules 2016, 21, 619; doi:10.3390/molecules21050619
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result of isotope-labeled compound uptake experiments using Carpoglyphus lactis, the biosynthetic
conversion of LA to (Z,Z)-6,9-heptadecadiene has been demonstrated [3].
Neryl formate ((Z)-3,7-dimethylocta-2,6-dienyl formate) and lardolure are aliphatic chain formates
found in acarids. Neryl formate was the first alarm pheromone discovered in acarids [
4] and was later
found to function as an alarm pheromone in many types of mites [ ]. Lardolure (1,3,5,7-tetrameth
1
yldecyl formate) has been identified as an aggregation pheromone in Lardoglyphus konoi and has been
understood to present aggregation activation in other acarid mites such as C. lactis, Aleuroglyphus
ovatus, and Tyrophagus putrescentiae [
side chain and is formed through the step-wise coupling of propionyl CoA with four molecules of
methylmalonyl CoA [ ]. The mechanism by which the carboxyl group is eliminated after the binding
5–7]. Lardolure is a specific compound having a regular methyl
6
of the methylmalonyl CoA molecules and the subsequent formation of the formate remains unknown.
Two aliphatic formate compounds have now been detected in the secretions of the unidentified
Sancassania sp. Sasagawa. While both compounds are presumed to be biosynthesized from the
straight-chain unsaturated fatty acids LA and OA, as with lardolure, the carbon-chain shortening
mechanism and formation of the formate ester require confirmation. This study reports the structure
determination and efficient synthetic methodologies for preparing these two compounds.
2. Results and Discussion
When analyzing the hexane-extracted components of the opisthonotal gland secretions from
Sancassania sp. Sasagawa by GC-MS, compounds
and 18.953 min, respectively. As presented in Figure 1, observation of the characteristic ion at m/z 280
and base peak ion at m/z 67 in the MS spectrum of compound is possible, and from the S-shaped
decrease in each fragment ion from the base ion to the m/z 280 ion, we speculated that compound is a
straight-chain fatty acid derived compound. The MS spectrum of compound also shows an S-shaped
1 and 2 were detected at retention times of 18.912 min
1
1
2
decline in each fragment ion from the m/z 82 base peak ion to the characteristic m/z 236 ion, which led
us to speculate that like compound 1, compound 2 is a straight-chain fatty acid derived compound.
Figure 1. Mass spectra of compounds 1 and 2 in the secretions of Sancassania sp. Sasagawa.
To determine the structures of compounds
1 and 2, the hexane extracts from the mites were
purified on a silica gel column by step-wise changes of the composition of the elution solvent. The 1H

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NMR spectra of the isolated compounds
1
and
2
were then recorded (Figure 2). The signal at
δ
8.05
(1H, s) for compound
5.31–5.42 (4H, dt, J = 10.8, 7.2 Hz, dt, J = 10.9, 7.1 Hz) was assigned to two Z-olefin protons, suggesting
the existence of two double bonds in the molecule. Furthermore, the signal at 4.16 (2H, t) was
2.77 (2H, t,
1 was assigned to the aldehyde proton on the formate, while the signal at δ
δ
assigned to the methylene protons adjacent to an oxygen atom, whereas the signal at
δ
J = 6.2 Hz) was assigned to methylene protons sandwiched between two olefins.
1
Figure 2. H-NMR and GC/FT-IR analyses of natural compounds 1 and 2.
In the 1H-NMR spectrum of compound
to those seen in compound , representing the aldehyde proton on the formate and methylene protons
2, the signals at δ 8.05 (1H, s) and δ 4.15 (2H, t) are similar
1
adjacent to an oxygen atom, respectively. However, the signal at
that there is only one Z-double bond in the molecule.
δ 5.33 (2H, dt, J = 10.8, 7.0 Hz) suggests
GC/FT-IR analysis of compounds
at 1747 cm´1 and an olefin absorption band at 3017 cm´1 (Figure 2). With regards to the cis-trans
isomerism of compounds and
, as the E-isomer specific absorption band near 980 cm´1 is not
1 and 2 shows that they both exhibit an ester absorption band
1
2
observed, the unsaturated bonds are assumed to be of the Z-form.
To determine the double-bond positions within the molecules, compounds 1 and 2 were reacted
with dimethyl disulfide (DMDS) and subjected to MS analysis [
to three methylene groups between its double bonds, the addition of two molecules of DMDS to the
double bonds affords a cyclic DMDS derivative through the elimination of dimethyl sulfide [2,9–11]
When subjecting the DMDS derivative of compound to mass spectrometric analysis, as shown in
8]. If a diene compound contains one
.
1
Figure 3a, fragment ions are observed at m/z 227 (A1 fragment (C13H23O2S2)+-MeSH) and m/z 131
(B1 fragment (C7H15S)+), and the formation of tetrahydrothiophene (M+ m/z 406) from cyclization
between positions 8 and 11, is detected. Furthermore, fragment ions are observed at m/z 203
(A2 fragment (C10H19O2S)+ or B2 fragment (C10H19S2)+) and m/z 155 (B2 fragment-MeSH), and
we also identified tetrahydrothiophene (M+ m/z 406) from the cyclization between positions 9 and
12. We also observe a signal at m/z 358, which remains after the elimination of MeSH from the
tetrahydrothiopyran (M+ m/z 406) cyclizing between positions 8 and 12, as well as at m/z 311,
which remains after the elimination of MeS from the previous fragment ion. On the basis of these
results, the double-bond position in compound
When analyzing the DMDS derivative of compound
DMDS has added to the double bond, and the product resulting from elimination of MeS from this
1
was determined to be between positions 8 and 11.
2
, the M+ ion at m/z 376, where one molecule of

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molecule, is observed at m/z 329. Furthermore, fragment ions at m/z 203 (A3 fragment (C10H19O2S)+)
and m/z 173 (B3 fragment (C10H21S)+) are observed owing to the type of cleavage shown in Figure 3b.
Thus, we concluded that there is a double bond at position 8. Based on all of the above spectral
data, we conclude the structures of compounds
1 and 2 as (Z,Z)-8,11-heptadecadienyl formate and
(Z)-8-heptadecenyl formate, respectively.
Figure 3. Mass fragmentation of DMDS derivatives derived from (a) compound 1 and (b) compound 2.
Compounds
1 and 2 were each synthesized in a four-step process, as shown in Scheme 1, with
Barton decarboxylation being the key reaction [12,13].
Scheme 1. Synthesis of two formates (
benzene; ( ) 3-hydroxy-4-methyl-2(3H)-thiazolethione, pyridine, Et2O, 74% (2 steps); (
ecanethiol, O2, visible light, triphenylphosphine, 41%; ( ) formic acid, acetic anhydride, pyridine, 69%.
1) and (
2). Reagents and conditions: (a) oxalyl chloride, DMF,
b
c) tert-dod
d

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Oxalyl chloride was used to convert the starting material LA to its acyl chloride form, and ester
3
was formed by reacting the acyl chloride with 3-hydroxy-4-methyl-2(3H)-thiazolethione. Ester
3
was
irradiated with light in the presence of tert-dodecanethiol under oxygen atmosphere and reductively
worked-up to produce the alcohol . By forming the formate from alcohol , the target formate
compound 1 is obtained in a total yield of 21%.
4
4
In previously reported work, two rounds of Grignard coupling between a terminal alkyne and an
alkyl halide were employed to extend the carbon chain, after which Lindlar reduction was used to
obtain alcohol 4. The whole procedure featured a total of six steps, and an overall yield of 18% [14].
By using the readily available and cheap unsaturated fatty acid LA as the starting material, the
synthetic route developed in this study did not require carbon-carbon bond formation nor control of
geometric isomerism, thereby achieving the facile synthesis of alcohol
overall yield of 30%.
4 in three steps and with an
Formate
used for compound
compounds and
confirmed as (Z,Z)-8,11-heptadecadienyl formate and (Z)-8-heptadecenyl formate, respectively.
Although the formate compounds and have been reported as preorbital secretions in
mammals such as the Cape grysbok (Raphicerus melanotis), male oribi (Ourebia ourebi) and male suni
(Neotragus moschatus) [15 17], this study presents the first example of their identification in arthropods.
Furthermore, while the above reports concerned only the structure determination of the compounds,
2
was easily prepared using OA as the starting material following the same synthetic route
. As the GC retention times, MS spectra, and 1H-NMR spectra of the synthesized
exactly match those of the natural products, compound and compound are
1
2
1
1
2
1
2
–
our work enables the quantitative examination of the bioactivity of compounds
successful achievement of their synthesis.
1 and 2 owing to the
It can be surmised from the double-bond positions that formate
while compound comes from OA. Isotope-labeled-compound uptake studies using C. lactis have
demonstrated that (Z,Z)-6,9-heptadecadiene, a hydrocarbon that is also a secretion component of
Sancassania sp. Sasagawa, is biosynthesized from LA [ ]. It has been reported that the biosynthesis
of hydrocarbons in insects works through the activity of cytochrome P450 on the aldehydes that
result from the reduction of fatty acyl-CoA [18 21]. Assuming that the same pathway is followed in
1 is biosynthesized from LA,
2
3
–
acarids, it is thought that (Z,Z)-6,9-heptadecadiene is synthesized with the aldehyde derived from LA
(linoleoyl-CoA) being the precursor, and work is currently underway to identify the enzyme involved
in this conversion. As the formate compounds 1 and 2 are secreted together with the hydrocarbons
(Z,Z)-6,9-heptadecadiene and (Z)-8-heptadecene, they are thought to be synthesized through the
activity of different enzymes on a common precursor within the secretory glands. However, the
mechanism of this conversion remains unknown. To resolve this problem, we are currently performing
detailed spectral analysis of formate compounds
1 and 2, following isotope-labeled-compound uptake
by Sancassania sp. Sasagawa.
3. Experimental
3.1. General Procedures
Column chromatography was performed on a Wakosil silica gel C-200 column with the specified
1
solvents. H- and 13C-NMR spectra were recorded on either a Biospin AC400M spectrometer (400 MHz
1
for H and 100 MHz for 13C, Bruker, Yokohama, Japan) or on a Bruker 500 MHz (500 MHz for
1H and 125 MHz for 13C) using tetramethylsilane as the internal standard. Natural compounds,
DMDS derivatives, and synthetic compounds were analyzed using the following two gas liquid
chromatograph systems; a model 263-30 (Hitachi, Tokyo, Japan) in split mode using a Al-clad fused
capillary column (0.25 mm i.d.
a temperature gradient from 135 to 250 C at 4 C/min, and a 6890N (Agilent Technologies Inc.,
Santa Clara, CA, USA) in splitless mode using an HP-5MS capillary column (0.25 mm i.d. 30 m,
0.25
m film thickness, Agilent Technologies Inc.) using a temperature gradient from 60 ˝C (2 min)
ˆ
25 m, 0.1 µm film thickness, Quadrex, Bethany, CT, USA) using
˝
˝
ˆ
µ

Molecules 2016, 21, 619
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˝
˝
to 290 C (5 min hold) at 10 C/min. Mass spectra were measured using either a Hitachi M-80B
high-resolution mass spectrometer operated at 70 eV or an Agilent Technologies 5975 Inert XL mass
selective detector operated at 70 eV. IR spectra were recorded using a FTIR 4300 (Shimadzu, Kyoto,
Japan) with an OV-1 bonded wide-bore column (0.53 mm i.d.
Tokyo, Japan).
ˆ
25 m, 5 µm film thickness, GL Sciences,
3.2. Mites
Unidentified Sancassania sp. Sasagawa (Acari: Acaridae) is a strain derived as the hypopus attached
to the Japanese rhinoceros beetle Trypoxylus dichotomus (L. 1771). The culture lines were maintained
for generations using the following rearing conditions: dry yeast feeding at 25 ˝C and 90% relative
˝
humidity and on agar medium as reported previously [22] at 20 C.
3.3. Extraction and Isolation
Mites (85.9 g) were separated from the culture medium and extracted with hexane (300 mL) to
obtain the secretions of the opisthonotal glands. After evaporation of the solvent, the extract (73 mg)
was applied to a SiO2 column (500 mg, Wako-gel C-200) and successively eluted with 5.0 mL of hexane,
and mixtures of ether in hexane (3%, 5%, 10%, and 20%). A mixture of formates
3% ether in hexane, was applied to a SiO2 column (500 mg, Wako-gel C-200), and eluted with 1.0 mL
of mixtures of benzene in hexane (25% and 50%). Both and eluted with 25% benzene in hexane
1 and 2 eluted with
1
2
were further purified by column chromatography using a SiO2 column (500 mg, Wako-gel C-200) and
eluted with 10% benzene in hexane to yield 1 (4.2 mg) and 2 (1.1 mg) separately.
3.4. Determination of Double-Bond Positions in Formates 1 and 2
The positions of the double bonds in formates
the DMDS derivatives, following a previously reported method [
DMDS (200
L) with a catalytic amount of I2 and kept overnight at 60 ˝C. The DMDS product was
extracted with hexane and worked up as reported elsewhere [ ]. The DMDS derivative of compound
1
and
2
were determined from the MS spectra of
8
]. Compound was dissolved in
1
µ
2
2
was prepared according to the same procedure as that used for compound 1.
3.5. Synthesis
3.5.1. 4-Methyl-2-thioxothiazol-3(2H)-yl(Z,Z)-9,12-octadecadienoate (3)
To a solution of LA (1.0 g, 3.57 mmol) in benzene (10 mL), oxalyl chloride (1.0 mL, 11.7 mmol) and
DMF (1 drop) was added at room temperature. The mixture was stirred for 2 h and then evaporated
in vacuo. The residue was dissolved in diethyl ether (3 mL) and the mixture was added to a solution
of 3-hydroxy-4-methyl-2(3H)-thiazolethione (535 mg, 3.64 mmol) and pyridine (2 drops) in diethyl
ether (12 mL). The mixture was stirred for 10 min at room temperature, after which it was filtered and
evaporated in vacuo. The residue was purified on a SiO2 column (hexane:EtOAc, 6:1) to yield ester
3 as
1
a bright yellow oil (1.08 g, 74%). H-NMR (400 MHz, CDCl3)
δ
6.23 (1H, d, J = 1.2 Hz), 5.36 (4H, m),
2.76 (2H, t, J = 6.0 Hz), 2.71 (1H, t, J = 8.6 Hz), 2.64 (1H, t, J = 8.0 Hz), 2.16 (3H, d, J = 1.2 Hz), 2.06 (4H,
m), 1.82 (2H, m), 1.46 (2H, m), 1.24–1.39 (12H, m), 0.89 (3H, t, J = 6.8 Hz). 13C-NMR (100 MHz, CDCl3)
δ
180.85 (C=S), 168.96 (C=O), 136.90 (=C–N), 130.25 (C=), 129.96 (C=), 128.14 (C=), 127.89 (C=), 102.37
(=C–S), 31.53 (CH2), 31.36 (CH2), 29.56 (CH2), 29.35 (CH2), 29.02 (CH2), 28.97 (CH2
27.17 (CH2), 25.65 (CH2), 24.59 (CH2), 22.58 (CH2), 14.08 (CH3), 13.35 (CH3).
ˆ
2), 27.21 (CH2),
3.5.2. 4-Methyl-2-thioxothiazol-3(2H)-yl(Z)-9-octadecenoate (5)
Ester
6.24 (1H, d, J = 1.2 Hz), 5.35 (2H, m), 2.71 (2H, m), 2.16 (3H, d, J = 1.2 Hz), 2.02 (4H, m), 1.82 (2H, m),
1.24–1.45 (20H, m), 0.88 (3H, t, J = 6.8 Hz). 13C-NMR (100 MHz, CDCl3)
180.82 (C=S), 168.97 (C=O),
136.90 (=C–N), 130.09 (C=), 129.66 (C=), 102.39 (=C–S), 31.91 (CH2), 31.35 (CH2), 29.77 (CH2), 29.65
5 was prepared from OA in the same manner as ester 3. δ
1H-NMR (400 MHz, CDCl3)
δ

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(CH2), 29.53 (CH2), 29.33 (CH2
(CH2), 22.69 (CH2), 14.13 (CH3), 13.36 (CH3).
ˆ
2), 29.02 (CH2
ˆ
2), 28.97 (CH2), 27.23 (CH2), 27.14 (CH2), 24.59
3.5.3. (Z,Z)-8,11-Octadecadienol (4)
A solution of ester
3 (100 mg, 0.244 mmol) in toluene (12 mL) containing tert-dodecanethiol
(198 mg, 0.980 mmol) was stirred vigorously and irradiated under oxygen atmosphere using an
incandescent lamp (60 W). After stirring at room temperature overnight, triphenylphosphine (96 mg,
0.366 mmol) was added and the mixture was stirred for several minutes. Evaporation of the solvent
yielded a residual oil that upon purification by SiO2 column chromatography (hexane:EtOAc, 4:1)
1
afforded alcohol
4
(25 mg, 41%). H-NMR (400 MHz, CDCl3)
δ
5.39 (4H, m), 3.64 (2H, t, J = 6.4 Hz),
2.77 (2H, t, J = 6.8 Hz), 2.05 (4H, m), 1.57 (2H, m), 1.24–1.39 (14H, m), 0.89 (3H, t, J = 6.8 Hz). 13C-NMR
(100 MHz, CDCl3) 130.23 (C=), 130.07 (C=), 128.05 (C=), 127.92 (C=), 63.09 (CH2O), 32.79 (CH2), 31.54
δ
(CH2), 29.60 (CH2), 29.35 (CH2), 29.32 (CH2), 29.25 (CH2), 27.21 (CH2
ˆ
2), 25.71 (CH2), 25.64 (CH2),
22.58 (CH2), 14.07 (CH3). MS (EI) m/z (rel. %): 252 (M+, 4), 234 (1), 149 (5), 135 (11), 121 (13), 109 (24),
95 (59), 81 (84), 67 (100), 55 (50), 41 (40).
3.5.4. (Z)-8-Octadecenol (6)
1
Alcohol
6
was prepared from ester
5
in the same manner as alcohol
4
. H-NMR (400 MHz, CDCl3)
δ
5.35 (2H, m), 3.65 (2H, t, J = 6.8 Hz), 2.02 (4H, m), 1.57 (2H, quint, J = 7.2 Hz), 1.27 (20H, m), 0.88
(3H, t, J = 7.2 Hz). 13C-NMR (100 MHz, CDCl3)
δ
130.02 (C=), 129.78 (C=), 63.10 (CH2O), 32.78 (CH2),
31.92 (CH2), 29.78 (CH2), 29.70 (CH2), 29.54 (CH2), 29.34 (CH2
ˆ
2), 29.26 (CH2), 29.09 (CH2), 27.23
(CH2), 27.19 (CH2), 25.72 (CH2), 22.71 (CH2), 14.15 (CH3). MS (EI) m/z (rel. %): 254 (M+, <1), 236 (11),
208 (3), 152 (4), 137 (9), 123 (17), 109 (34), 96 (76), 82 (100), 67 (73), 55 (77), 41 (44).
3.5.5. (Z,Z)-8,11-Heptadecadienyl Formate (1)
To alcohol
prepared by mixing acetic anhydride (60
at 0 ˝C. The mixture was maintained at this temperature for 4 h. Iced water was then added to the
solution, which was extracted with EtOAc. The organic layer was successively washed with 2N HCl,
saturated NaHCO3, and brine and dried over Na2SO4. After evaporation of the solvent in vacuo, the
4
(25 mg, 0.099 mmol) in pyridine (0.5 mL), a mixed anhydride (210
µL), which was
µL) and formic acid (150
µ
L) at 0 ˝C, was added dropwise
resulting oil was purified by SiO2 column chromatography (hexane:EtOAc, 4:1) to give formate
1
1
(19 mg, 69%). H-NMR (400 MHz, CDCl3)
δ 8.06 (1H, s), 5.37 (4H, dt, J = 10.8, 7.2 Hz, dt, J = 10.9,
7.1 Hz), 4.16 (2H, t, J = 7.2 Hz), 2.77 (2H, t, J = 6.2 Hz), 2.05 (4H, m), 1.65 (2H, m), 1.26–1.40 (14H, m),
0.89 (3H, t, J = 6.8 Hz). 13C-NMR (100 MHz, CDCl3)
δ
161.21 (OCHO), 130.25 (C=), 129.99 (C=), 128.12
(C=), 127.89 (C=), 64.11 (CH2O), 31.54 (CH2), 29.54 (CH2), 29.35 (CH2), 29.13 (CH2), 29.09 (CH2), 28.50
(CH2), 27.21 (CH2), 27.17 (CH2), 25.80 (CH2), 25.64 (CH2), 22.58 (CH2), 14.07 (CH3). HRMS m/z (M+).
Calculated for C18H32O2: 280.2400; Found 280.2379.
3.5.6. (Z)-8-Heptadecenyl formate (2)
1
Formate
CDCl3)
J = 6.8 Hz), 1.22–1.40 (20H, m), 0.88 (3H, t, J = 7.2 Hz). 13C-NMR (100 MHz, CDCl3)
130.06 (C=), 129.68 (C=), 64.11 (CH2O), 31.91 (CH2), 29.76 (CH2), 29.63 (CH2), 29.53 (CH2), 29.33
2
was prepared from alcohol
6
in the same manner as formate
1. H-NMR (400 MHz,
δ
8.06 (1H, s), 5.35 (2H, dt, J = 10.8, 7.0 Hz), 4.16 (2H, t, J = 6.8 Hz), 2.02 (4H, m), 1.66 (2H, quint,
161.23 (OCHO),
δ
(
CH2 ˆ 2), 29.12 (CH2), 29.09 (CH2), 28.49 (CH2), 27.22 (CH2), 27.14 (CH2), 25.79 (CH2), 22.69 (CH2),
14.13 (CH3). HRMS m/z (M+–HCOOH). Calculated for C17H32: 236.2502; Found 236.2481.
4. Conclusions
We have achieved a facile synthesis of the two formates, (Z,Z)-8,11-heptadecadienyl formate and
(Z)-8-heptadecenyl formate, which are the main secretions from the acarid Sancassania sp. Sasagawa,

Molecules 2016, 21, 619
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with the Barton decarboxylation being a key reaction in the synthesis. While the position of their
double bonds suggests that their biosynthesis proceeds from linoleic or oleic acid, respectively, their
biosynthetic pathways may feature a novel chain-shortening mechanism and formate formation.
Acknowledgments: This study was supported in part by a Grant-in-Aid for Scientific Research (C) (No. 24580167
for NS) from the Japan society for the promotion of Science (JSPS).
Author Contributions: N.S. and Y.K. conceived and designed the experiments; D.S., H.M. and Y.S. performed the
experiments; N.S. and Y.K. analyzed the data; N.S. wrote the paper.
Conflicts of Interest: The authors declare no conflict of interest.
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