Stereoselective synthesis of the Paulownia bagworm sex pheromone

Article abstract of DOI:10.1016/j.cclet.2016.11.018

According to our retrosynthesis, the main chain of the target molecule could be constructed using a C5?+?C7?+?C5 strategy. The key induction reaction afforded chiral methyl group moieties using different Evans templates with different configurations. Li₂CuCl₄ was effectively employed in the Csp³[sbnd]Csp³ coupling protocol. The target molecular was obtained in a 12.6% overall yield with nine steps in the longest linear route.

Full text of DOI:10.1016/j.cclet.2016.11.018

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CCLET 3892 No. of Pages 5
Chinese Chemical Letters xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Original article
Stereoselective synthesis of the Paulownia bagworm sex pheromone
a,
Zhi-Feng Suna,b, Lu-Nan Zhoua, Tao Zhanga, , Zhen-Ting Du
*
*
a
Shaanxi Key Laboratory of Natural Products & Chemical Biology, College of Science, Northwest A&F University, Yangling 712100, China
College of Chemical and Environment Science, Shaanxi University of Technology, Hanzhong 723001, China
b
A R T I C L E I N F O
A B S T R A C T
Article history:
According to our retrosynthesis, the main chain of the target molecule could be constructed using a
C5 + C7 + C5 strategy. The key induction reaction afforded chiral methyl group moieties using different
Evans templates with different configurations. Li2CuCl4 was effectively employed in the Csp3ꢀꢀCsp3
coupling protocol. The target molecular was obtained in a 12.6% overall yield with nine steps in the
longest linear route.
Received 17 August 2016
Received in revised form 28 October 2016
Accepted 1 November 2016
Available online xxx
Keywords:
Pheromone
Paulownia bagworm
Evans template
Total synthesis
© 2016 Tao Zhang and Zhen-Ting Du. Chinese Chemical Society and Institute of Materia Medica, Chinese
Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
1. Introduction
that (3R,13R)-(S)-2-methylpentan-3-yl-3,13-dimethylpentadeca-
noate (1,Fig. 1) exhibited the strongest luring activity to the male
Nowadays, there is a sharper and sharper conflict between
intense agricultural production and environmental issues. We all
are facing a challenge caused by the detrimental effects resulting
from traditional agricultural production. In fact, there has been a
trend using some “green pesticide” in management of pest to
suppress and control the pest population through mass trapping,
attacticides and mating disruption [1]. In this context integrated
pest management (IPM), the use of these low-dose substance
would reduce the influence to the environment drastically [2].
Normally, the insect pheromone consists of some long-chained
aliphatic compounds [3]. For example, the Paulownia bagworm,
Cryptothelea variegata, is one of the most destructive forest
defoliators widely distributed in Asia-Pacific countries, such as
Japan, Korea, India, Indonesia, Thailand, New Zealand and in
particular, China. This type of insect is quite difficult to control
using common pesticides because its larvae often envelop
themselves in a self-constructed bag. In 2006, Gries et al. firstly
investigated the composition of the female-produced sex phero-
mone of C. variegata and identified (S)-2-methylpentan-3-yl-3,13-
dimethylpentadecanoate as a major component [4]. Moreover, the
detailed chiral stereochemistry of C3 and C13 was ascertained
Paulownia bagworm [5]. Because of environmental issues, it is
becoming increasingly unsustainable to kill pests using traditional,
high-toxic pesticides. Obviously, using pheromones to control this
kind of pest by luring and trapping would be a promising
alternative. In 2010, Mori et al. reported the synthesis of all four of
the stereoisomers of (S)-2-methylpentan-3-yl-3,13-dimethylpen-
tadecanoate starting from the expensive (R)- or (S)-2-methyl-
butan-1-ol and (R)- or (S)-citronellal using olefin cross metathesis
as the key reaction [6a]. Recently, starting from the expensive (S)-
propylene oxide, Taguri et al. reported syntheses of a set of four
isomers of 1, through a sulfone mediated coupling process as the
key step [6b]. As a continuation of our studies on the synthesis of
insect pheromones [7], we have developed a practical route to
synthesise this most active pheromone molecule. Herein, we
report the efficient, cost-effective asymmetric synthesis of 1.
2. Results and discussion
The retrosynthetic analysis is shown in Scheme 1. The target
molecular was firstly disconnected from the chiral alcohol. Then,
the main chain was dissembled into three parts, a chiral C5 subunit,
a C7 subunit and another chiral C5 subunit. Thus, the focus became
how to obtain the two chiral methyl subunits and realise the
coupling reaction of Csp3ꢀꢀCsp3.
after
a field bioassay of four possible stereoisomers of 2-
methylpentan-3-yl-3,13-dimethylpentadecanoate as attractants
to the male Paulownia bagworm [5]. Their forest trial revealed
It is well known that chiral oxazolidin-2-one, namely Evans
template, can form different steric space effects after protonation,
which then give rise to an asymmetric alkylation process [8]. As
* Corresponding authors.
E-mail addresses: fuzitong@163.com (T. Zhang), duzt@nwsuaf.edu.cn (Z.-T. Du).
http://dx.doi.org/10.1016/j.cclet.2016.11.018
1001-8417/© 2016 Tao Zhang and Zhen-Ting Du. Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V.
All rights reserved.
Please cite this article in press as: Z.-F. Sun, et al., Stereoselective synthesis of the Paulownia bagworm sex pheromone, Chin. Chem. Lett. (2016),
http://dx.doi.org/10.1016/j.cclet.2016.11.018

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CCLET 3892 No. of Pages 5
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Z.-F. Sun et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
the d.r. more than 99:1. Compound 4 was subjected to reduction in
the presence of lithium borohydride to give chiral alcohol 5 in 93%
25
yield ([
a
]
5.9 (c 1.12, CHCl3), lit. [9] [a] 5.8 (c 1.09, CHCl3)).
D
Compound 5 could be transformed into compound 6 after PCC
oxidation protocol. Thus, the first C5 subunit was obtained. The
middle C7 subunit was prepared from 1,7-heptanediole. It could be
transformedinto7-bromo-heptanolselectivelyinconditionsof40%
hydrobromic acid in the presence of catalytic iodine with a Dean–
Stark trap. In order to couple with compound 6, the residual
hydroxyl group was allowed to be protected by THP (tetrahydro-
pyranyl) ether. Compound 8 was converted to its phosphonium salt
with PPh3 in xylene at reflux. The Wittig reaction was allowed to
connect two parts in THF, and then the coupled compound was
Fig. 1. Structure of the female Paulownia bagworm sex pheromone.
shown in Scheme 2, the synthesis commenced from n-butyryl
chloride, then the (R)-4-benzyloxazolidin-2-one was connected to
give compound 3 in an excellent yield. After protonation by fresh
prepared LDA and methylation with 3 equiv. of methyl iodide, the
chiral induced compound 4 could be afforded in an 85% yield with
Scheme 1. Retrosynthesis of 1.
Scheme 2. Synthesis of C5 + C7 intermediate. Regents and reactants: (a) n-BuLi, (R)-4-benzyloxazolidin-2-one, dry THF, ꢀ78 ꢁC to room temperature, overnight, 91%; (b) LDA,
MeI, THF, ꢀ78 ꢁC to room temperature, overnight, 85%; (c) LiBH4, THF, 0 ꢁC to room temperature, 24 h, 93%; (d) PCC, CH2Cl2, 0 ꢁC to room temperature, overnight, 82%; (e) 40%
HBr, I2, toluene, 120 ꢁC, 24 h, 77%; (f) TsOH, DHP, CH2Cl2, 0 ꢁC to room temperature, overnight, 84%; (g) i) PPh3, xylene, reflux 8 h; ii) BuLi, ꢀ78 ꢁC, dry THF, overnight; iii) Pd/C,
H2, EtOAc, iv) TsOH, CH3OH, H2O, 74% for 4 steps; (h) CBr4, Ph3P, CH2Cl2, 87%.
Scheme 3. Synthesis of 1. Regents and reactants: (a) BnCl, NaOH, reflux, 6 h, 87%; (b) i) EtOCOCl, Et3N, dry Et2O, 0 ꢁC to room temperature; ii) n-BuLi, (S)-4-benzyloxazolidin-2-
one, dry THF, ꢀ78 ꢁC to room temperature, overnight, 87%; (c) NaHMDS, MeI, dry THF, ꢀ78 ꢁC to room temperature, overnight, 66%; (d) LiAlH4, dry THF, 0 ꢁC to room
temperature, 24 h, 83%; (e) TsCl, Et3N, DMAP, CH2Cl2, 0 ꢁC to room temperature, overnight, 76%; (f) i) Compound 10, Mg, I2, dry THF, 80 ꢁC; ii) Li2CuCl4, NMP, THF, 80 ꢁC, 87%; iii)
Pd(OH)2/C, H2, CH3OH, quantitatively; (g) CrO3, CH3COOH, room temperature, 24 h, 63%; (h) (CF3CO)2O, CH2Cl2, room temperature, 75%.
Please cite this article in press as: Z.-F. Sun, et al., Stereoselective synthesis of the Paulownia bagworm sex pheromone, Chin. Chem. Lett. (2016),
http://dx.doi.org/10.1016/j.cclet.2016.11.018

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3
hydrogenated to give 9 in 67% yield in three steps. After a
4.1. (R)-4-Benzyl-3-butyryloxazolidin-2-one 3
conventional acidic procedure to remove THP ether, the obtained
alcohol 9 was transformed into bromide 10 by the combination of
In argon, to a cooled (ꢀ78 ꢁC) solution of (R)-4-benzyloxazo-
lidin-2-one (21.6 g, 0.121 mol) in anhydrous THF (300 mL) was
added n-BuLi (55 mL, 2.5 M in hexane), and then the reaction
mixture was stirred for 30 min. Butyryl chloride (14 mL) was slowly
added at this temperature and the reaction mixture was stirred for
1 h. The reaction mixture was warmed to room temperature and
maintained for another 8 h. Then, the mixture was quenched by
saturated ammonia chloride and extracted by ethyl acetate. The
organic phase was combined and washed with saturated brine,
dried over Na2SO4, and concentrated under reduced pressure. The
25
CBr4 andtriphenylphosphine in87%yield, [a D
]
ꢀ2.9(c2.6, CHCl3).
With the C5 + C7 intermediate 10 successfully synthesised, we
next turned our attention to another C5 subunit, which was
prepared from g-lactone. As shown in Scheme 3, the ring-opening
and benzylation in one-pot led to the efficient production of
compound 11 on a large scale. The connection of compound 11
with (S)-4-benzyloxazolidin-2-one through activated mixed-an-
hydride with ethyl chloroformate at ꢀ78 ꢁC for 6 h was accom-
plished in an 87% yield. The subsequent asymmetric methylation
delivered compound 13 using sodium bis(trimethylsilyl)amide as a
base with only one desirable diastereomer 14 in a 70% yield and a
ratio of d.r. > 90:1. In the methylation step, the optimal conditions
involved the slow addition of three equivalents of methyl iodide in
diluted THF (tetrahydrofuran) solution over 2 h to avoid the
dimethylated by-product. Removal of the auxiliary moiety by
lithium aluminium hydride in dry THF and subsequent tosylation
produced compound 15 in an excellent yield. As to the reduction
and removal of the Evans auxiliary, the yield of the expensive
lithium borohydride was higher than of lithium aluminium
hydride. After the same coupling condition in the presence of
Li2CuCl4 in the mixture of THF and NMP, compound 16 was
produced. Removal of the benzyl group was accomplished through
Pd(OH)2/C catalytic hydrogenation and the obtained alcohol was
oxidised by Jones’ reagent to afford acid 2 in a two-step 63% yield,
The chiral alcohol 17 could be prepared through a reported kinetic
crude product was purified by column chromatography to produce
27
3 (27.4 g, 91%) as a colourless oil. [
NMR (400 MHz, CDCl3):
a
]
ꢀ54.5 (c 3.00, CHCl3). 1H
D
d
1.01 (t, 3H, J = 7.4 Hz), 1.68–1.77 (m, 2H),
2.76 (dd, 1H, J = 13.4, 9.3 Hz), 2.83–3.00 (m, 2H), 3.30 (dd, 1H,
J = 13.3, 3.1 Hz), 4.15–4.22 (m, 2H), 4.64–4.70 (m, 1H), 7.20–7.35 (m,
5H). 13C NMR (100 MHz, CDCl3):
d 173.2, 153.4, 135.3, 129.4, 128.9,
127.3, 66.1, 55.1, 37.9, 37.3, 17.6, 13.6.
4.2. (R)-4-Benzyl-3-((R)-2-methylbutanoyl)oxazolidin-2-one 4
To a stirred solution of 3 (3.5 g, 14.15 mmol) in anhydrous THF
(20 mL) at ꢀ78 ꢁC, LDA (2.0 mol/L in THF, 8.88 mL, 17.75 mmol) was
added dropwise under an argon atmosphere. After stirring for 1 h
at ꢀ78 ꢁC, MeI (2.65 mL, 42.55 mmol) was added and the reaction
mixture was stirred for an additional 1 h at ꢀ78 ꢁC and then
warmed to room temperature. Upon completion of the reaction
(monitored by TLC), the reaction mixture was quenched with
saturated NH4Cl (10 mL) and extracted with EtOAc (70 mL ꢂ 3). The
combined organic extracts were washed with brine (50 mL), dried
with anhydrous Na2SO4 and concentrated under reduced pressure.
The crude product was purified by column chromatography to
afford 4 (3.2 g, 85%) as a colourless liquid. 1H NMR (400 MHz,
resolution process [4]. After activation with trifluoroacetic
25
anhydride, the total synthesis of target molecule 1, [a D
(c 0.23, CHCl3) was finally achieved in a 75% yield.
]
ꢀ3.8
3. Conclusions
We have successfully synthesised the most active stereo-
isomers of (3R,13R)-(S)-2-methylpentan-3-yl-3,13-dimethylpenta-
decanoate, the major and most active component of the sex
pheromone of C. variegata. Evans template induction was adopted
to produce the chiral methyl group moieties. Li2CuCl4 was used to
catalyse the Csp3ꢀꢀCsp3 coupling, which was a key method in
construction of the skeleton. Based on our synthetic route, a set of
four diastereoisomers could be prepared with ease using only
different Evans auxiliaries. Our results are highly beneficial for
preventing and controlling Paulownia bagworm, C. variegata, in an
economical and environmentally benign way.
CDCl3): d 0.93 (t, 3H, J = 7.4 Hz), 1.22 (d, 3H, J = 7 Hz), 1.43–1.50 (m,
1H), 1.74–1.81 (m, 1H), 2.76 (dd, 1H, J = 14.3, 9.8 Hz), 3.27 (dd, 1H,
J = 12.3, 3.1 Hz), 3.61–3.66 (m,1H), 4.15–4.22 (m, 2H), 4.65–4.71 (m,
1H), 7.20–7.35 (m, 5H). 13C NMR (100 MHz, CDCl3):
d 177.1, 153.0,
135.3, 129.4, 128.8, 127.3, 65.9, 55.3, 39.1, 37.8, 26.3, 16.8, 11.6.
4.3. (R)-2-Methylbutanal 6
To a solution of compound 4 (4.9 g, 18.8 mmol) in THF (120 mL)
at 0 ꢁC, was added an aqueous solution of LiBH4 (0.18 g, 7.55 mmol)
portion-wise. The solution then was allowed to warm to room
temperature naturally. After completion, the reaction mixture was
neutralised by diluted HCl and extracted with EtOAc (50 mL ꢂ 3).
The combined organic extract was washed with brine (50 mL),
dried with Na2SO4 and concentrated under atmospheric pressure.
The crude product was purified by column chromatography to
afford 5 (1.34 g, 83%) as a colourless liquid. 1H NMR (300 MHz,
4. Experimental
All anhydrous solvents and reagents were prepared from
reagent grade materials using conventional methods. The reac-
tions of air and moisture sensitive materials were carried out in
flame dried glassware under a nitrogen atmosphere. The transfer of
air and water sensitive solutions was completed using hypodermic
syringes. The NMR data were recorded in CDCl3 solution with
Bruker AC-500 or AM-400 MHz spectrometers, if not stated
otherwise. The chemical shifts are reported in ppm relative to
TMS. Column chromatography was generally performed on a silica
gel (200–300 mesh) gradient elution with petroleum ether and
ethyl acetate, and TLC inspections on silica gel GF-254 plates with
petroleum ether:ethyl acetate (8:1, v/v), if not stated otherwise.
The purities of the synthesised compounds were estimated by GC–
MS using a Trace GC–MS 2000.
CDCl3): d 0.91 (t, 3H, J = 7.4 Hz), 1.22 (d, 3H, J = 7.1 Hz), 1.20–1.35 (m,
1H), 1.39–1.56 (m, 1H), 1.67–1.77 (m, 1H), 3.29-3.45 (m, 2H). To a
solution of compound 5 (1.2 g,13.6 mmol) in CH2Cl2 (60 mL) at 0 ꢁC,
was added PCC (pyridinium chlorochromate, 3.5 g, 16.3 mmol)
portion-wise. The mixture was stirred at room temperature until
completion. Then, ether was added to the system and filtered
through a pad of silica gel. The filtrate was washed with diethyl
ether, then was dried with Na2SO4 and concentrated in vacuo. The
resultant compound 6 was used as obtained without further
purification.
Please cite this article in press as: Z.-F. Sun, et al., Stereoselective synthesis of the Paulownia bagworm sex pheromone, Chin. Chem. Lett. (2016),
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4.4. (R)-9-Methylundecan-1-ol 9
4.7. (3R,13R)-3,13-Dimethylpentadecanoic acid 2
Compound 8 was prepared according to the literature [10] and
the corresponding triphenyl phosphonium salt was also prepared.
To a cooled solution of the salt (6.4 g,11.7 mmol) in THF (80 mL) was
added BuLi (12 mmol), and then maintained for 1 h. The resultant
mixture was cooled to ꢀ78 ꢁC again and the crude compound 6
(0.85 g, 10 mmol) in THF (15 mL) was added slowly. Through
conventional workup and purification via column chromatogra-
phy, the olefin product of the Wittig reaction was obtained. The
crude produce was dissolved into methanol (50 mL) and 4-
methylbenzenesulfonic acid (200 mg) was added. The reaction
mixture was stirred overnight and then 20%Pd(OH)2/C (500 mg)
was added to catalyse the hydrogenation process. After evapora-
tion, the residue was purified through column chromatography to
afford chiral alcohol 9 (1.4 g, 74%) as colourless oil. IR (neat, cmꢀ1):
To a solution of CrO3 (1 g, 10 mmol) in 80% acetic acid (10 mL)
was added dropwise
a solution of compound 16 (720 mg,
2.8 mmol) in acetic acid (7 mL). The reaction mixture was allowed
to stir at room temperature for 24 h. Upon completion, it was
diluted with water (30 mL) and extracted with ether (30 mL ꢂ 5).
The combined extracts were treated with a conventional workup
and purified through column chromatography to give 2 (600 mg,
24
80%). [
a
]
ꢀ1.5 (c 1.25, CHCl3). IR (neat, cmꢀ1): 3500–3200, 2959,
D
2925, 2854, 1709, 1363. 1H NMR (400 MHz, CDCl3):
d 0.83–0.89 (m,
6H), 0.96 (d, 3H, J = 6.7 Hz), 1.06–1.16 (m, 2H), 1.16–1.38 (m, 20H),
2.14 (dd, 1H, J = 14.9, 8.2 Hz), 2.35 (dd, 1H, J = 14.9, 5.9 Hz). 13C NMR
(100 MHz, CDCl3): d 178.2 41.6, 36.6, 34.3, 30.1, 30.0, 29.7, 29.6, 29.5,
27.1, 26.8, 19.6, 19.2, 11.4.
2956, 2928, 2855,1454,1100, 734, 697.1H NMR (400 MHz, CDCl3):
d
4.8. (3R,13R)-(S)-2-Methylpentan-3-yl-3,13-dimethylpentadecanoate
0.84 (t, 3H, J = 7.4 Hz), 0.95 (d, 3H, J = 6.7 Hz),1.16–1.23 (m,1H),1.28–
1.39 (m, 7H), 1.59–1.66 (m, 2H), 2.00–2.05 (m, 2H), 2.31–2.34 (m,
1H), 3.45–3.49 (m, 2H), 5.08–5.13 (m, 1H), 5.28–5.34 (m, 1H), 7.26–
7.35 (m, 5H). 13C NMR (100 MHz, CDCl3): 138.6, 136.1, 128.4, 128.3,
127.6, 127.4, 72.8, 70.4, 33.3, 30.2, 29.8, 29.7, 29.1, 27.4, 26.0, 21.0,
11.9. HRESIMS (C19H30O): 274.2710.
1
To a solution of compound 2 (50 mg, 0.2 mmol) in dichloro-
methane (20 mL) was added two drops of trifluoroacetic anhydride.
Compound 17 (25 mg, 0.25 mmol) in dichloromethane (1 mL) was
added after 30 min. The reaction mixture was evaporated and
purified through column chromatography to give 1 (35 mg, 75%).1H
4.5. (R)-1-Bromo-9-methylundecane 10
NMR (400 MHz, CDCl3): d 0.83–0.94 (m, 18H), 1.04–1.38 (m, 21H),
1.48–1.58 (m, 2H), 1.80–1.85 (m, 1H), 2.11 (dd, 1H, J = 14.5, 8.2 Hz),
At 0 ꢁC, to a solution of compound 9 (5.0 g, 27.2 mmol) in
dichloromethane (150 mL) was added CBr4 (11.3 g, 34 mmol) and
triphenylphosphine (11.4 g, 44 mmol). Then, the ice bath was
removed and the reaction mixture was stirred for another 5 h. The
reaction mixture was evaporated and the residue was purified
2.31 (dd,1H, J = 14.5, 5.9 Hz), 4.66–4.70 (m, 1H). 13C NMR (100 MHz,
CDCl3): d173.3, 79.4, 42.2, 36.7, 36.6, 34.3, 30.8, 30.3, 30.0, 29.7, 29.6,
29.4, 27.1, 26.9, 23.9, 19.7, 19.2, 18.5, 17.6, 11.4, 9.8.
Acknowledgements
through column chromatography to afford chiral bromide 10 as
23
colourless oil (5.88 g, 87%). [a D
]
3.2 (c 0.61, CHCl3). IR (neat,
0.83–
Financial support from the National Natural Science Foundation
of China (No. 31301712) is greatly appreciated. Zhenting Du would
like to thank the Opening Funds of the Key Laboratory of Synthetic
Chemistry of Natural Substances, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences for partial financial
support. Zhenting Du is deeply indebted to Hong-Li Zhang for his
assistance in acquiring NMR spectra.
cmꢀ1): 2959, 2925, 2854, 1462. 1H NMR (400 MHz, CDCl3):
0.87 (m, 6H), 1.06–1.31 (m, 2H), 1.27–1.34 (m, 11H), 1.40–1.44 (m,
2H), 1.82–1.89 (m, 2H), 3.41 (t, 2H, J = 7.0 Hz). 13C NMR (100 MHz,
CDCl3): 36.5, 34.3, 34.0, 32.8, 29.8, 29.4, 28.7, 28.1, 27.0, 19.2, 11.4.
d
4.6. (3R,13R)-3,13-Dimethylpentadecan-1-ol 16
Compound 15 was prepared through a similar literature
procedure to 6 and the yield is shown in Scheme 3. At 0 ꢁC, to a
flask charged with 14 (2.88 g, 20 mmol) in redistilled pyridine
(30 mL) was added 4-methylbenzene-1-sulfonyl chloride (4.2 g,
22 mmol) potion-wise. The reaction mixture was stirred for 2 h and
poured into diluted HCl, and then extracted with ethyl acetate. All
the organic phases were combined and washed with water, brine
and 5% CuSO4, successively. The obtained compound 15 was used
directly without further purification. Under argon, to another
three-necked flask was charged Mg (200 mg, 8.7 mmol) and the
chiral compound 10 (1.8 g, 7.25 mmol) was introduced slowly, thus,
a Grignard reagent of compound 10 can be obtained successfully.
Dilithium tetrachlorocuprate(II) solution (7 mL, 0.1 mol/L in THF,
from Sigma-Aldrich) and anhydrous NMP (3 mL) were added into
the above solution. Compound 15 was then introduced into the
reaction mixture through a double-tipped needle. Thereafter, the
reaction mixture was refluxed for 10 h and evaporated to dryness,
purified through a column to give (3R,13R)-3,13-dimethylpenta-
decyl benzyl ether. This ether was dissolved in methanol (40 mL)
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23
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2958, 2924, 2853, 1463, 1377, 1057, 735. 1H NMR (400 MHz, CDCl3):
d
0.82–0.89 (m, 9H), 1.07–1.16 (m, 2H), 1.16–1.41 (m, 20H), 1.50–
1.64 (m, 2H), 3.62–3.72 (m, 2H). 13C NMR (100 MHz, CDCl3):
61.2,
39.9, 37.1, 36.6, 34.4, 30.0, 29.9, 29.7, 29.4, 27.1, 26.9, 19.6, 19.2, 11.4.
d
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