Synthesis and nuclear magnetic resonance spectroscopic properties of some acetylenic tellura fatty acid esters

Article abstract of DOI:10.1016/S0009-3084(97)00026-1

Five positional isomers of acetylenic tellura stearate (-5) have been synthesized by three different routes.The number of methylene groups located between the acetylenic system and the tellurium metal varies from 0 to 4.The 1H and 3C NMR spectroscopic properties have been studied.The tellurium atom induces strong deshielding effects on the adjacent methylene protons, which in combination with the deshielding effects of the acetylenic system allows most of the methylene groups between the tellurium and the triple bond to be identified by 1H NMR spectroscopic analysis.The tellurium causes a very strong shielding effects (ca. -27.1 ppm) on the carbon shift of the adjacent α-methylene carbon atom, but weak deshielding effect on the β-(ca. +2.6 ppm) and γ-(ca. +2.3 ppm) methylene carbon atoms.Carbon shifts of methylene carbon atoms, especially those which are located between the tellurium atom and the triple bond, are found very much upfield (δ_c 0.65-4.81) and in one case in the negative region (δ_c -17.95) of the 13C NMR spectrum.Most of the signals of the carbon nuclei of these analogue have been identified and from the results of these analyses the number of methylene groups between the acetylenic system and the tellurium atom can be determined. - Keywords: acetylenic, NMR spectroscopy; positional isomers; synthesis; unsaturated tellura; stearate analogues

Full text of DOI:10.1016/S0009-3084(97)00026-1

Chemistry and Physics of Lipids
87 (1997) 55–63
Synthesis and nuclear magnetic resonance spectroscopic
properties of some acetylenic tellura fatty acid esters
Marcel S.F. Lie Ken Jie *, Sherman H. Chau
Department of Chemistry, The Uni6ersity of Hong Kong, Pokfulman road, Hong Kong, Hong Kong
Received 2 December 1996; received in revised form 26 March 1997; accepted 26 March 1997
Abstract
Five positional isomers of acetylenic tellura stearate (1–5) have been synthesized by three different routes. The
number of methylene groups located between the acetylenic system and the tellurium metal varies from 0 to 4. The
1H and 13C NMR spectroscopic properties have been studied. The tellurium atom induces strong deshielding effects
on the adjacent methylene protons, which in combination with the deshielding effects of the acetylenic system allows
1
most of the methylene groups between the tellurium and the triple bond to be identified by H NMR spectroscopic
analysis. The tellurium causes a very strong shielding effect (ca. −27.1 ppm) on the carbon shift of the adjacent
h-methylene carbon atom, but weak deshielding effects on the i-(ca. +2.6 ppm) and k-(ca. +2.3 ppm) methylene
carbon atoms. Carbon shifts of methylene carbon atoms, especially those which are located between the tellurium
atom and the triple bond, are found very much upfield (lC 0.65–4.81) and in one case in the negative region
(lC−17.95) of the 13C NMR spectrum. Most of the signals of the carbon nuclei of these analogue have been
identified and from the results of these analyses the number of methylene groups between the acetylenic system and
the tellurium atom can be determined. © 1997 Elsevier Science Ireland Ltd.
Keywords: Acetylenic; NMR spectroscopy; Positional isomers; Synthesis; Unsaturated tellura; Stearate analogues
1. Introduction
Chau, 1995a) and the dichloride derivatives of
some methyl tellura laurates (Lie Ken Jie and
Chau, 1995b), and have studied the nuclear mag-
netic resonance spectroscopic (NMR) and mass
spectrometric properties of this class of fatty acid
ester analogues (Lie Ken Jie and Chau, 1995c).
Long-chain fatty acids containing a tellurium
atom in the alkyl chain are shown to inhibit the
process of i-oxidation of fatty acids in the my-
We have reported the synthesis of a complete
series of position isomers of methyl tellura laurate
(Lie Ken Jie et al., 1991), long-chain methyl esters
containing a tellurophene system (Lie Ken Jie and
* Corresponding author. Fax: +852 2517 0217; e-mail:
hrsclkj@hkucc.hku.hk
0009-3084/97/$17.00 © 1997 Elsevier Science Ireland Ltd. All rights reserved.
PII S00 9-3084(97)00026-1

56
M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
ocardium. Such long-chain fatty acids have been
used to trap radiolabelled fatty acids in the heart
tissues for myocardial imaging purposes (Knapp
et al., 1979; Srivastava et al., 1987; Goodman and
Knapp, 1982). There are only a few reported cases
of unsaturated tellura fatty acids in the chemical
literature. Knapp et al. have described the synthe-
sis of unsaturated tellura fatty acid analogues
containing an iodo-vinylic system, where the dou-
ble bond is located at the end of the fatty acid
chain (Knapp et al., 1984).
In our continuing effort to study the properties
of long-chain fatty acids containing a hetero atom
in the alkyl chain, we report in this paper the
synthesis of five unsaturated tellura stearate ester
analogues containing an acetylenic bond and a
tellurium atom in defined positions of the alkyl
chain (compounds 1–5).
GSX-270 fourier transformed NMR spectrometer
(JEOL, Tokyo, Japan) at an operating frequency
of 270 MHz for proton and 67.89 MHz for
carbon nuclei from solutions in deuteriochloro-
form (CDCl3) with tetramethylsilane (TMS) as
the internal reference standard. Chemical shifts
are given in lH and lC values in ppm downfield
from TMS (lTMS=0). Solvents used in the syn-
thesis were distilled and dried over sodium in
benzophenone. 5-Hexyn-1-ol, 4-pentyn-1-ol, 3-bu-
tyn-1-ol, 5-bromopentanoic acid, 6-bromohex-
anoic acid and 8-bromooctanoic acid were
purchased from Aldrich (St. Louis, MO).
2.1. General method for the preparation of di-,
tri- and tetra-methylene interrupted acetylenic
tellura fatty acid esters (1–3) as exemplified by
the synthesis of ethyl 12-tellura-6-octadecynoate
(1) (Scheme 1)
CH3(CH2)5−Te−(CH2)4−CꢀC
−(CH2)4COOEt (1)
5-Hexyn-1-ol (13.2 g, 0.135 mol) was added to a
suspension of lithamide [prepared from lithium
(4.0 g, 0.57 mol), Fe(III) nitrate (0.5 g) and liquid
ammonia (1 l)] in liquid ammonia and the reac-
tion mixture was stirred for 1 h. 5-Bromopen-
tanoic acid (23 g, 0.13 mol) in tetrahydrofuran
(THF, 50 cm3) was slowly added and the resulting
mixture was stirred for 12 h. The ammonia was
allowed to evaporate and dilute HCl (2 M, 200
cm3) was added and the reaction mixture was
extracted with diethyl ether (3×100 cm3). The
ethereal extract was washed with water (2×30
cm3) and dried over anhydrous sodium sulfate.
The filtrate was evaporated and the residue was
refluxed with borontrifluoride-methanol complex
(15%, w/w, 10 cm3) and absolute methanol (100
cm3) for 20 min. Water (150 cm3) was added and
the reaction mixture was extracted with petroleum
ether (b.p. 60–80°C, 3×50 cm3). The petroleum
extract was washed with water (30 cm3) and dried.
The filtrate was evaporated under reduced pres-
sure and the residue was chromatographed (100 g
silica) using a mixture of petroleum ether: diethyl
ether (4:1, vol/vol) as eluent to give methyl 11-hy-
droxy-6-undecynoate (17.7 g, 65%) as an oil. In-
frared analysis (cm−1) 3395, 1733, 1434, 1175,
CH3(CH2)5−Te−(CH2)3−CꢀC
−(CH2)5COOEt (2)
CH3(CH2)5−Te−(CH2)2−CꢀC
−(CH2)6COOEt (3)
CH3(CH2)8−CꢀC−CH2−Te
−(CH2)4COOEt (4)
CH3(CH2)6−CꢀC−Te−(CH2)7COOMe (5)
One of the main objectives of this work is to
study the effects of the tellurium atom and the
acetylenic system on the shifts of the adjacent
methylene group by NMR spectroscopy. For this
reason the number of methylene groups between
the acetylenic bond and the hetero atom (tel-
lurium) in these fatty acid analogues is varied
from 0 to 4.
2. Material and methods
Infrared spectra were measured as neat samples
on a Shimadzu model IR-470 spectrophotometer
(Shimadzu, Kyoto, Japan). Nuclear magnetic res-
onance (NMR) spectra were recorded on a JEOL
1
1063; H NMR (lH) 1.4–1.8 (m, 8H, CH2), 2.0–
2.4 (m, 6H, 2–H, 5-H and 8-H), 3.59 (s, 3H,

M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
57
Scheme 1.
COOCH3); 13C NMR (dC) 17.99 (C-8), 18.47 (C-
5), 24.92 (C-3), 27.52, 28.52, 31.85, 33.21 (C-11),
33.64 (C-2), 52.44 (COOCH3), 79.69 (C-6), 80.28
(C-7) and 173.87 (C-1); microanalysis: calc. for
C12H19O2Br, C, 52.37, H, 6.96, found C, 52.59
and H, 7.04.
COOCH3), 3.72 (t, J=6.5 Hz, CH2-OH); 13C
NMR (lC) 18.47 (C-5), 18.58 (C-8), 24.16 (C-3),
25.41 (C-9), 28.52, 29.01, 31.99 (C-10), 33.64 (C-
2), 51.49 (COOCH3), 64.43 (C-11), 79.63 (C-6),
80.42 (C-7) and 174.11 (C-1).
A mixture of methyl 11-hydroxy-6-undecynoate
(2.0 g, 9.4 mmol), methanesulfonyl chloride (2 g,
A mixture of tellurium (powder, 1.0 g), sodium
borohydride (0.2 g, 5.4 mmol) and dimethylfor-
mamide (DMF, 20 cm3) was stirred at 80°C for 2
h under nitrogen. 1-Bromohexane (1.3 g, 7.6
mmol) in DMF (5 cm3) was added and the reac-
tion mixture was stirred for 2 h. Water (80 cm3)
was added and the reaction mixture was extracted
with petroleum ether (3×30 cm3). The petroleum
extract was evaporated under reduced pressure to
give crude dihexylditelluride (1.55 g). Sodium
borohydride (0.15 g, 4 mmol) and absolute
ethanol (30 cm3) were added to the crude di-
hexylditelluride and the mixture was stirred for 30
min at room temperature. The temperature of the
reaction mixture was raised to 80°C and methyl
11-bromo-6-undecynoate (0.5 g, 1.8 mmol) in
ethanol (5 cm3) was added and the reaction mix-
ture was stirred for 3 h. Water (50 cm3) was then
added to the cooled reaction mixture, which was
extracted with diethyl ether (3×30 cm3). The
ethereal extract was washed with water and dried
17.5
mmol),
pyridine
(5
cm3)
and
dichloromethane (50 cm3) was stirred at 0–5°C
for 30 min and for a further 1 h at room temper-
ature. The reaction mixture was successively
washed with dilute HCl (2M, 30 cm3), water (30
cm3) and dried (Na2SO4). The filtrate was evapo-
rated and a solution of lithium bromide (1.5 g, 17
mmol) in acetone (25 cm3) was added to the
residue. The mixture was refluxed for 1 h and ice
water (20 cm3) was added to the cooled reaction
mixture. The reaction mixture was extracted with
petroleum ether (3×30 cm3). The petroleum ex-
tract was washed with water (30 cm3) and dried
(Na2SO4). The filtrate was evaporated under re-
duced pressure and the residue was chro-
matographed on silica gel (40 g) using a mixture
of petroleum ether: diethyl ether (9:1, vol/vol) as
eluent to give methyl 11-bromo-6-undecynoate
(1.5 g, 54%) as an oil. Infrared analysis (cm−1
1734, 1432,1332, 1251, 1174; H NMR (lH) 1.6–
1.8 (m, 8H, CH2), 2.0–2.4 (m, 6H, 2-H, 5-H,
8-H), 3.44 (t, J=6.4 Hz, CH2Br) and 3.62 (s, 3H,
)
1
(Na2SO4 The filtrate was evaporated and the
).
residue was chromatographed on a silica gel (50

58
M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
Scheme 2.
g) column using a mixture of petroleum ether:
diethyl ether (9:1, vol/vol) as eluent to give ethyl
12-tellura-6-octadecynoate (1, 0.55 g, 72%) as an
oil.
cm3) was added and the mixture was stirred for 3
h. Water (100 cm3) was added to the cooled
reaction and the mixture was extracted with di-
ethyl ether (3×50 cm3). The ethereal extract was
washed with water (20 cm3) and dried (Na2SO4).
The filtrate was evaporated and the residue was
chromatographed on a silica gel (20 g) column
using a mixture of petroleum ether: diethyl ether
(9:1, vol/vol) as eluent to give ethyl 6-tellura-8-oc-
tadecynoate (4, 0.43 g, 26%) as an oil.
2.2. Synthesis of the methylene-interrupted
acetylenic tellura fatty acid ester (6iz. ethyl
6-tellura-8-octadecynoate, 4)(Scheme 2)
1-Bromo-2-decyne was prepared in 58% yield
from 2-dodecyn-1-ol (obtained from the dilithio
derivative of propargyl alcohol and 1-
bromononane) by similar method as described for
11-bromo-6-undecynoate.
2.3. Synthesis of non-methylene interrupted
acetylenic tellura fatty acid ester (6iz. methyl
9-tellura-10-octadecynoate (5) (Scheme 3)
A mixture of tellurium (powder, 1.0 g), sodium
borohydride (0.2 g, 5.4 mmol) and DMF (20 cm3)
was stirred at 80°C for 2 h under nitrogen. Methyl
5-bromopentanoate (1.5 g, 1.6 mmol) in DMF (5
cm3) was added to the cooled reaction and the
reaction mixture was stirred for 12 h at room
temperature. Water (30 cm3) was added and the
reaction mixture was extracted with diethyl ether
(3×30 cm3). The ethereal extract was washed
with water (20 cm3) and dried (Na2SO4). The
solvent was evaporated and the residue consisting
of CH3OOC(CH2)4-Te-Te-(CH2)4COOCH3 ap-
peared as a red oily residue (1.8 g). A solution of
sodium borohydride (0.15 g, 4 mmol) in ethanol
(25 cm3) was added to the red oily residue and the
reaction mixture was stirred for 30 min. The
reaction mixture was heated to 80°C and 1-
bromo-2-dodecyne (1.0 g, 4.1 mmol) in ethanol (5
n-Butyl lithium (2.5 cm3, 15% solution in n-
hexane) was added to a solution of 1-nonyne (0.45
g, 3.6 mmol) in THF (15 cm3) at 0°C under
nitrogen and stirred for 15 min. Tellurium (pow-
der, 0.3 g) was added and the reaction mixture
was refluxed for 5 h. The reaction mixture was
cooled to 0°C and a solution of methyl 8-bro-
mooctanoate (0.45 g, 1.9 mmol) in THF (5 cm3)
was added. The reaction mixture was maintained
at 0°C for 12 h. Water (40 cm3) was then added
and the reaction mixture was extracted with di-
ethyl ether (3×30 cm3). The ethereal extract was
washed with water (20 cm3) and dried (Na2SO4).
The filtrate was evaporated and silica gel (20 g)
chromatographic purification using a mixture of
petroleum ether: diethyl ether (9:1, vol/vol)
eluent to give methyl 9-tellura-10-octadecynoate
(5, 0.25 g, 31%).

M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
59
Scheme 3.
3. Results and discussion
strated the versatile synthetic approach adopted in
this work, which allowed the tellurium atom to be
located at any pre-determined position of the
alkyl chain of the fatty acid ester molecule. Com-
pound 4 was prepared starting from commercially
available propargyl alcohol, which was condensed
via its dilithio derivative with 1-bromononane to
give 2-dodecyn-1-ol. The latter was transformed
to 1-bromo-2-decyne via the mesyloxy intermedi-
ate. 1-Bromo-2-decyne was subsequently coupled
with the sodium tellurolate derived from methyl
5-bromopentanoate to give ethyl 6-tellura-8-oc-
tadecynoate (4) in 26% yield (Scheme 2). The yield
of this last reaction was persistently low, as the
formation of the ditelluride of the bromo-ester
(methyl bromopentanoate) appeared to be a low-
yielding reaction.
To prepare the non-methylene interrupted
acetylenic tellura fatty acid ester (5), 1-lithium
nonyne was reacted with tellurium metal in te-
trahydrofuran (Dabdoub and Comasseto, 1988).
The tellurium intermediate was subsequently re-
acted with methyl 8-bromooctanoate to yield the
requisite product (methyl 9-tellura-10-octade-
cynoate, (5) in 31% yield. As no sodium borohy-
dride and ethanol were involved in this reaction,
the product obtained was the methyl ester deriva-
tive (Scheme 3).
3.1. Synthesis of acetylenic tellura fatty acid
esters (1–5)
To incorporate 2–4 methylene groups between
the tellurium atom and the acetylenic bond for the
proposed acetylenic tellura analogues (1–3), ꢀ-
alkyn-1-ols [HO(CH2)nCꢀCH, n=2,3 or 4] were
considered as the most suitable starting blocks
(Scheme 1). Chain extension from the acetylenic
end with esters of ꢀ-bromoalkanoic acids pro-
vided hydroxy-acetylenic acid intermediates (aver-
age yield of 65%). The hydroxy group of these
intermediates was readily transformed to the bro-
mide via the mesyloxy function using lithium bro-
mide in acetone with an average yield of 53%.
Subsequent reaction of the bromo-acetylenic ester
intermediates with the corresponding sodium
alkyltellurolate (RTeNa) (from dialkylditelluride
with sodium borohydride in ethanol) furnished
the requisite ethyl acetylenic tellura fatty acid
esters (1–3) (average 70% yield) (Scheme 1). Ethyl
esters were obtained as the final products, due to
the presence of a slight excess of sodium borohy-
dride in ethanol employed during the final step of
the synthesis sequence which caused the methyl
ester group to be inter-esterified to the ethyl ester.
In compounds 1–3 the tellurium atom occupied a
position between the acetylenic bond and the
terminal methyl group.
1
3.2. H NMR properties of acetylenic tellura
fatty acid esters (1–5)
In the synthesis of the mono-methylene and the
non-methylene interrupted acetylenic tellura fatty
acid esters (compounds 4 and 5, repectively), the
tellurium atom occupied a position between the
acetylenic bond and the carboxylic ester group.
This change in the synthesis strategy demon-
The shift effects of an acetylenic system on the
chemical shifts of the adjacent methylene protons
are reported, the results of which showed that the
acetylenic bond imparts a slight deshielding effect
(given as a positive
on the adjacent h-, i-

60
M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
Table 1
Results of the 1H-NMR analysis of acetylenic tellura fatty acid esters (1–5)
Nucleus (protons)
Compound (lH)
(1)
(2)
(3)
(4)
(5)
2-H
2.34(t) (J=7.2)
2.32(t) (J=7.2)
2.30(t) (J=7.2)
2.34(t) (J=7.2)
2.31(t) (J=7.2)
3-H
a
a
a
a
a
4-H
a
a
a
a
a
5-H
2.10(m)
a
b
2.87(t) (J=6.8)
b
6-H
—
2.10(m)
a
Te
a
7-H
—
—
2.10(m)
3.27(s)
a
8-H
2.10(m)
—
—
—
2.77(t) (J=6.8)
9-H
a
2.10(m)
—
—
Te
10-H
11-H
12-H
13-H
14-H
15-H
16-H
17-H
18-H
Ethyl ester
Methyl ester
a
2.10(m)
2.71(t) (J=6.8)
Te
2.63(t) (J=6.8)
a
b
b
2.70(s)
2.70(s)
Te
2.61(t) (J=6.8)
a
b
b
2.10(m)
2.10(m)
a
b
b
b
b
b
—
—
2.64 (t, J=6.8)
Te
2.64 (t, J=6.8)
a
b*
b
b
0.89(t) (J=7.0)
1.25(t) 4.12(q)
—
2.48(t) (J=7.0)
a
a
b
b
b
0.89(t) (J=7.0)
—
3.67(s)
b
b
0.89(t) (J=7.0)
1.25(t) 4.12(q)
—
0.90(t) (J=7.0)
1.25(t) 4.12(q)
—
0.90(t) (J=7.0)
1.25(t) 4.12(q)
—
a=1.50–1.80; b=1.20–1.40.
CH3(CH2)5-Te-(CH2)4-CꢀC-(CH2)4COOEt (1)
CH3(CH2)5-Te-(CH2)3-CꢀC-(CH2)5COOEt (2)
CH3(CH2)5-Te-(CH2)2-CꢀC-(CH2)6COOEt (3)
CH3(CH2)8-CꢀC-CH2-Te-(CH2)4COOEt (4)
CH3(CH2)6-CꢀC-Te-(CH2)7COOMe (5)
1
accomplished. The results of the H NMR chemi-
cal shifts of compounds 1–5 are summarized in
Table 1.
and k-methylene protons of +0.82, +0.16 and
+0.13 ppm, respectively (Frost and Gunstone,
1975). Such values (shift parameters) when added
to a basic value (1.255) for the shift of unper-
turbed methylene protons would give a fairly
accurate estimation of the proton shifts of a par-
ticular proton(s) under those effects. From our
The presence of four methylene groups between
the acetylenic bond and the tellurium atom in the
alkyl chain of compound
1 prevented the
acetylenic system to exercising any additional shift
effect on the methylene group adjacent to the
tellurium atom and vice versa. As a result the
shifts of the protons of the methylene groups
(5-H, 8-H) adjacent to the acetylenic bond ap-
peared at the anticipated region of the spectrum
lH 2.10 (multiplet), while the shifts of the
methylene protons adjacent to the tellurium atom
(11-H, 13-H) appeared as a triplet at lH 2.64 (t,
J=6.8 Hz). In the trimethylene-interrupted iso-
mer (compound 2) the shifts of the methylene
protons adjacent the tellurium atom were
1
study of the H NMR properties of methyl tellu-
ralaurates, the tellurium nucleus shows strong
deshielding effects (positive values for the shift
parameters) on the shifts of the adjacent
methylene protons: +1.395, +0.495 and +
0.145 ppm for the h-, i- and k-methylene pro-
tons, respectively (Lie Ken Jie et al., 1991). By
taking the combined shift effect of the acetylenic
system and that of the tellurium nucleus into
consideration, the assignments of the various
shifts of the adjacent methylene protons in the
acetylenic tellura fatty acid esters could be readily
resolved into two overlapping triplets at lH 2.63

M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
61
(13-H) and 2.71 (11-H) due to the k-effect of the
acetylenic system on the 11-H protons. However,
the k-effect from the tellurium on the methylene
adjacent to the acetylenic bond was not obvious,
as the signals for these protons were not further
differentiated as they appeared unresolved in the
region lH 2.10 (m) of the spectrum.
acetylenic fatty esters, the shielding shift effects
(given as negative values) of an acetylenic system
on the carbon shifts of methylene groups have
been determined as: −11.00, −0.65 and −0.80
for the adjacent h-, i- and k-methylene carbon
nuclei, respectively (Bus et al., 1976). We have
also determined the effects of a tellurium atom on
the shifts of the adjacent methylene carbon atoms
as: −27.10 (shielding), +2.62 (deshielding) and
+2.34 (deshielding) for the h-, i- and k-
methylene carbon nuclei, respectively (Lie Ken Jie
et al., 1991). The shift value of an unperturbed
methylene carbon atom was assumed at 29.75
ppm. Taking the combined effects of the
acetylenic system and the tellurium nucleus into
consideration, the assignments of the shifts of the
various methylene carbon atoms were accom-
plished. The results of the 13C NMR chemical
shifts of compound 1–5 are summarized in Table
2.
In compounds 1–4 the presence of less per-
turbed triple bond was readily confirmed by the
signals in the region of lC 79–82 for the shifts of
the acetylenic carbon atoms, but not in the case of
compound 5 where the tellurium atom is bonded
to the triple bond. The strong shielding effect of
the acetylenic system on the adjacent methylene
carbon atoms caused these carbon atoms to ap-
pear at lC 18–22, unless the nuclei were being
further affected by the tellurium atom. The very
strong shielding h-effects exhibited by the tel-
lurium atom caused many of the shifts of the
adjacent methylene carbons to appear close to the
zero value of the spectrum (lC =0, tetramethylsi-
lane) and in one instance (compound 4) the shift
of one of the adjacent methylene carbons ap-
peared in the negative range of the 13C NMR
spectrum.
For compound
3 the shifts of the two
methylene groups between the acetylenic bond
and the tellurium atom were clearly being affected
by the these groups. The shifts of these protons
appeared as a singlet at lH 2.70 (4H, 10-H, 11-H),
which reflected the chemical equivalence of these
protons. The shifts of the 13-H (methylene pro-
tons adjacent to the tellurium atom) and that of
7-H were found at lH 2.61 (triplet) and 2.10
(multiplet), respectively. Compound 4 could be
readily differentiated from the other isomers from
the singlet at lH 3.27, which was due to the shift
of the protons of the methylene group between
the acetylenic bond and the tellurium atom. A
significant downfield effect from the acetylenic
system on the other methylene group adjacent to
the tellurium atom was also observed as the shifts
of these protons (5-H) appeared at lH 2.87 (t).
However, the tellurium atom appeared not to
cause any significant deshielding effect on the
protons of the remaining methylene group adja-
cent (10-H, lH 2.10) to the acetylenic bond.
In the analysis of compound 5, where the
acetylenic group and the tellurium atom are
bonded together, the interaction of the metal and
the acetylenic system caused the methylene pro-
tons adjacent to the acetylenic bond and that
adjacent to the tellurium atom to be clearly re-
solved. The shifts of the 8-H and 12-H protons
appeared as distinct triplets at lH 2.77 and 2.48,
respectively. From this study of the 1H NMR
properties of acetylenic tellura fatty acid esters, it
was possible to characterise the non-methylene,
mono- and di-methylene from the tri- and tetra-
methylene interrupted isomers from their 1H
NMR spectral properties.
In compound 1 (a tetramethylene interrupted
acetylenic tellura isomer) the combined effects of
the tellurium and acetylenic system made it
difficult to differentiate the shifts of the i-
methylene carbon atoms (C-9 and C-10) as the
shifts appeared at lC 31.35 and 31.45 for these
two nuclei. However, in this narrow region of the
spectrum, the signals at lC 31.27 and 31.75 could
be assigned to the C-15 and C-16 carbon nuclei,
13
3.3. C NMR properties of acetylenic tellura
fatty acid esters (1–5)
In the study of 13C NMR properties of

62
M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
Table 2
Results of the 13C NMR analysis of acetylenic tellura fatty acid esters (1–5)
Nucleus (carbon)
Compound (lC)
(1)
(2)
(3)
(4)
173.60
33.72
27.34
31.57
4.81
(5)
C-1
C-2
C-3
C-4
C-5
C-6
C-7
C-8
173.87
33.67
24.20
28.20
18.53
79.91
80.18
18.15
31.45a
31.35a
1.79
173.30
34.02
24.54
28.41a
28.76a
18.66
80.80
79.20
21.07
31.61
1.44
173.63
34.35
24.89
28.77a
28.50a
28.68a
18.77
80.93
81.04
22.56
0.65
174.06
34.08
24.92
29.12
28.58
31.42
31.50
8.90
Te
−17.95
82.99
78.23
19.05
29.09a
28.97a
29.27a
29.56a
29.23a
31.93
22.70
14.00
C-9
Te
C-10
C-11
C-12
C-13
C-14
C-15
C-16
C-17
C-18
Ethyl ester
Methyl ester
34.34
112.73
21.02
28.82a
28.82a
29.12a
31.77
22.64
14.06
—
Te
2.79
Te
2.95
Te
3.11
32.29
31.27
31.75
22.59
14.03
14.30 60.25
—
32.26
31.26
31.75
22.56
14.00
14.28 60.28
—
32.34
31.23
31.75
22.69
14.00
14.27 60.11
—
14.30 60.20
—
51.38
a Interchangeable.
CH3(CH2)5-Te-(CH2)4-CꢀC-(CH2)4COOEt (1)
CH3(CH2)5-Te-(CH2)3-CꢀC-(CH2)5COOEt (2)
CH3(CH2)5-Te-(CH2)2-CꢀC-(CH2)6COOEt (3)
CH3(CH2)8-CꢀC-CH2-Te-(CH2)4COOEt (4)
CH3(CH2)6-CꢀC-Te-(CH2)7COOMe (5)
shift value (lC −17.95) observed for the shift of
the methylene carbon atom (C-7) of compound 4,
which is located between the acetylenic system
and the tellurium atom.
respectively. The h-methylene carbons to the
acetylenic system and those adjacent to the tel-
lurium atom were readily identified. In this iso-
mer, where the acetylenic bond is located between
the C-6/C-7 position of the fatty acid ester chain,
the long range effect from the ethyl ester function
on the shift of the acetylenic carbon atoms per-
mitted the acetylenic carbon atoms to be resolved
with the result that the shifts of the C-6 and C-7
carbon nuclei appeared at lC 79.91 and 80.18,
respectively.
The carbon shifts of the methylene carbon
atom(s) of the mono-, di- and tri-methylene inter-
rupted acetylenic tellura isomers (compounds 2–
4) were readily assigned. The effect of the
tellurium atom on the shifts of the acetylenic
system also allowed the acetylenic carbon atoms
to be identified. Of interest was the large negative
In compound 5, where the tellurium atom is
bonded to the acetylenic system, the shifts of the
acetylenic carbon atoms were unique and ap-
peared at lC 34.34 and 112.73 for C-10 and C-11,
respectively. However, the shift of the methylene
carbon atom adjacent to the tellurium nucleus
(C-8) appeared much more downfield (at lC 8.90)
than expected (at about lC 2.00–3.00 region) of
this nucleus. Similarly the methylene carbon adja-
cent to the acetylene system (C-12) appeared at lC
21.02 instead of about lC 18.00 had there been no
tellurium atom bonded to the triple bond
From the study of the NMR properties of these
acetylenic tellura fatty acid esters, it was possible

M.S.F. Lie Ken Jie, S.H. Chau / Chemistry and Physics of Lipids 87 (1997) 55–63
63
Dabdoub, M.J., Comasseto, J.V., 1988. Organometallics 7,
84–87.
Frost, D.J., Gunstone, F.D., 1975. Chem. Phys. Lipids 15,
53–85.
Goodman, M.M., Knapp, F.F., 1982. J. Org. Chem. 47,
3004–3006.
to use this technique to identify each isomers as
either the non-, mono-, di-, tri- or tetra-methylene
interrupted isomer acetylenic tellura fatty ester
analogue.
Knapp, F.F., Ambrose, K.R., Callahan, A.P., Grigsby, R.A.,
Irgolic, K.J. 1979. Radiopharm 2, Proc Int Symp 101-108.
Knapp, F.F., Srivastava, P.C., Callahan, A.P., Cunningham,
E.B., Kabalka, G.W., Sastry, K.A.R., 1984. J. Med. Chem.
27, 57–63.
Lie Ken Jie, M.S.F., Cheung, Y.K., Chau, S.H., Yan, B.F.Y.,
1991. J. Chem. Soc. Perkin Trans. 2, 501–508.
Lie Ken Jie, M.S.F., Chau, S.H., 1995. J. Chem. Res. (S)428,
(M)2642–2657.
Acknowledgements
The Lipid Research Fund, the Research Grants
Committee of the University of Hong Kong and
the Research Grant Council of Hong Kong pro-
vided financial assistance.
Lie Ken Jie, M.S.F., Chau, S.H., 1995b. Chem. Phys. Lipids
78, 189–192.
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