Analysis of the labial gland secretion of the cuckoo-bumblebee (Psithyrus vestalis) males and synthesis of abundant geranylcitronellol

Article abstract of DOI:10.1135/cccc19961501

Labial glands of the cuckoo-bumblebee males of the species Psithyrus vestalis were extracted and the components of their secretions were identified. Chemical composition of the males' signal of Psithyrus vestalis has not yet been described in the literatu

Full text of DOI:10.1135/cccc19961501

Labial Gland Secretion of the Cuckoo-Bumblebee
1501
ANALYSIS OF THE LABIAL GLAND SECRETION OF THE CUCKOO-BUMBLEBEE
(Psithyrus vestalis) MALES AND SYNTHESIS OF ABUNDANT
GERANYLCITRONELLOL
1
2
Irena VALTEROVA , Ales SVATOS and Oldrich HOVORKA
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic,
166 10 Prague 6, Czech Republic; e-mail: 1 irena@uochb.cas.cz, 2 svatos@uochb.cas.cz
Received September 18, 1996
Accepted October 2, 1996
Dedicated to the memory of Dr Zdenek Arnold.
Labial glands of the cuckoo-bumblebee males of the species Psithyrus vestalis were extracted and the
components of their secretions were identified. Chemical composition of the males’ signal of Psi-
thyrus vestalis has not yet been described in the literature. We found geranycitronellyl acetate to be
the main component (48%). Geranylcitronellol and (Z)-15-eicosen-1-ol were present in the secretion
in lower amounts. Long-chain aldehydes, acetates, and hydrocarbons formed only minor components
of the mixture. The identification of minor components was based on GC-MS, while the more abundant
compounds were isolated and fully characterized by spectral and chemical methods. For the structure
confirmation, geranylcitronellol was prepared from geranyl bromide via a three-step synthesis.
Key words: Psithyrus vestalis; Cuckoo-bumblebees; Marking pheromone; Geranylcitronellol;
Geranylcitronellyl acetate.
Chemical signals of bumblebees were studied extensively by Swedish authors1,2. Dur-
ing the flight period in summer, the bumblebee and cuckoo-bumblebee males in the
majority of species exhibit a patrolling behaviour. They fly around the nest or away
from it and mark their territories with a pheromone secreted from the labial gland3,4
The pheromone-marked places attract conspecific females for mating5.
.
The labial gland secretion is usually a mixture of acyclic mono-, sesqui- and diter-
penes (alcohols and acetates), various straight-chain fatty acid derivatives (alcohols,
esters, aldehydes, and both saturated and unsaturated hydrocarbons with from 12 to 18
carbon atoms in the chain). The composition of the secretion is species-specific1. Berg-
ström and co-workers studied the temporal and spatial segregation between species and
subspecies6. Except for the geographical isolation, species patrolling in the same area
segregate to some extent in time and space. Species occurring in the same time and
habitat differ substantially in the composition of their marking pheromone to avoid
inter-species mating.
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

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Valterova, Svatos, Hovorka:
Chemistry of several Scandinavian Psithyrus species was published by Cederberg
and co-workers7. The occurrence of Psithyrus vestalis was earlier reported as very rare
in Scandinavia, but its spreading in South-Western Sweden during last few years was
found by Andersson8. The cuckoo-bumblebee species living in the Czech Republic
have not been thoroughly investigated from the chemical point of view. The secretion
of Psithyrus vestalis has not yet been described in the literature. Preliminary results on
the labial gland secretion of Psithyrus vestalis were presented only recently9. However,
the chemoecological aspects of this species will be published independently by Bergman
and coworkers10.
OR
1, R = COCH3
2, R = H
H
H
H
b
a
I
IZn
CO Me
CO Me
HO2C
CO Me
2
2
2
5
4
6
R
c
d
R
I
R-Br
H
7
8
9
e
H
H
f
R
CO CH
2
R
CH OH
2
3
10
(3R)-2
a) 1) BH .Me S, 2) TosCl/pyridine, 3) NaI/acetone
3
2
R =
b) Zn/THF, 35 οC
c) "C H Li "/THF/hexanes, -35 οC
3
2 2
d) 1) Me Al/Cl ZrCp , 2) I /THF
3
2
2
2
e) Pd[Ph P] /6/THF, r.t.
3
4
f) LiAlH /ether
4
SCHEME 1
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Labial Gland Secretion of the Cuckoo-Bumblebee
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EXPERIMENTAL
Insects: Males of the species Psithyrus vestalis (9 individuals) were collected in August 1995 in
Czech Central Mountains, locality Oblik, about 60 km North-West of Prague, elevation 509 m above
the sea level. The collected living insects were transported to the laboratory and then kept in the
freezer until dissection of labial glands. The dissected glands were extracted with hexane (50 µl per
gland).
Chromatography: The extracts and synthetic samples were analyzed using a gas chromatograph
HP 5890 (Hewlett–Packard) equipped with a split/splitless injector (220 °C), and with a flame ioni-
zation detector (290 °C) or a mass detector (Fisons MD 800) working in impact ionization mode,
respectively. A DB-5 column (30 m × 0.25 mm, J & W Scientific) and helium gas (flow 0.7 ml/min
at 50 °C) was used for the separations. The temperature program started at 50 °C (1 min delay), than
temperature of the oven was increased to 140 °C (rate 50 °C/min), to 240 °C (2 °C/min), and finally
to 320 °C (5 °C/min). The identification of minor compounds was based mostly on their mass spectra
compared with those in National Institute of Standards and Technology (NIST, U.S.A.) Library and
on the co-chromatography with synthetic or commercially available standards. Column chromatography
separations were made on Merck 60 silica gel (0.040–0.063 mm) using ethyl acetate or ether in light
petroleum or hexane11. Silica gel/silver nitrate chromatography was performed on a TLC plate (Merck
60 GS 254, 35 × 75 mm) impregnated with AgNO3 (10%). A repeated elution with hexane–ether mixture
(7 : 3) was used for the separation.
Spectral methods: NMR spectra were determined in CDCl3 solutions on Varian UNITY-500, operating at
1
499.5 MHz for H and at 128 MHz for 13C NMR spectra, respectively. Chemical shifts are expressed
in δ (ppm) scale relative to tetramethylsilane for 1H and relative to CDCl3 signal (77.23 ppm) for 13C NMR,
respectively. Coupling constants (J) are reported in Hz. Tentative assignments are denoted with an
asterisk. IR spectra, reported in cm–1, were recorded on a Bruker IFS 88 FT-IR and a Perkin–Elmer
621 spectrometers in CCl4 solutions and in potassium bromide micropellets (1.5 mm diameter), re-
spectively. Gas-phase infrared spectra (GC-FTIR) spectra were taken on a HP 5890 gas chromato-
graph coupled with an HP 5695A IRD equipped with a narrow-band (4 000–750 cm–1) infrared
detector (mercury cadmium telluride). Electron impact (70 eV) mass spectra were obtained on ZAB-
EQ (VG, England) instrument. Optical rotation was determined on a Perkin–Elmer 241 polarimeter.
Chemicals: All chemical reactions were run in an oven dried glassware under inert atmosphere of
argon or nitrogen. Allene was prepared from commercially available 2,3-dichloro-1-propene (Fluka)
according literature procedure12 and stored at –70 °C prior use. Tetrahydrofuran and ether were dis-
tilled from Na-benzophenone ketyl in nitrogen atmosphere. Extracts of reaction mixture were washed
with aqueous sodium chloride solution, dried over MgSO4 and solvents were removed at reduced
pressure.
Preparative Chromatography of the Gland Extracts
The hexane extract of one gland (50 µl) was chromatographed on silica gel (290 mg) in a Pasteur
pipette. The elution of sample started with pentane, followed by hexane–ether mixtures (1–40% of
ether). Two fractions contained compounds concentrated enough to enable further separation and
derivatization. The first one, eluted with 5% ether in hexane, contained geranylcitronellyl acetate 1:
Mass spectrum, m/z (%): 334 (0.7; M+), 319 (0.2), 291 (1), 265 (2), 250 (1), 231 (0.2), 223 (1), 205
(1), 191 (2), 177 (1), 163 (4), 149 (5), 136 (17), 121 (21), 109 (8), 107 (8), 95 (28), 81 (78), 69
(100), 55 (12), 41 (35). IR spectrum (KBr): 1 742, 1 237, 1 042 (OAc). The second fraction, eluted
with 40% ether in hexane, contained alcohols, where geranylcitronellol 2 and (Z)-15-eicosen-1-ol 3
prevailed. This mixture was separated on silica gel/silver nitrate preparative TLC. Geranylcitronellol 2
exhibited identical MS and IR spectral data as we are reporting for synthetic sample of (3R)-2. (Z)-15-
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Valterova, Svatos, Hovorka:
eicosen-1-ol: Mass spectrum, m/z (%): 281 (0.05; M+–CH3), 278 (0.1; M+–H2O), 250 (0.04), 152
(0.3), 138 (1), 137 (1), 124 (2), 123 (2), 110 (5), 109 (5), 96 (18), 82 (33), 81 (27), 69 (38), 67 (34),
55 (100), 41 (69), 31 (18). IR spectrum (KBr): 3 376 (OH), 2 957, 2 922, 2 852 (C–H), 1 460, 1 375
(C–H), 1 050 (C–O); (gas phase): 3 668 (OH), 3 012 (C=C), 2 994, 2 865, 1 460, 1 354, 1 045.
Derivatization: Dimethyl disulfide (DMDS) adduct of isolated alcohol 3 was prepared according
published procedure13. Mass spectrum, m/z (%): 390 (12; M+), 117 (100; C6H13S), 273 (99.6;
C16H33OS). The same derivatization method was applied on a chromatographic fraction eluted with
2.5% ether in hexane and containing a mixture of hydrocarbons, aldehydes and acetates. The result-
ing mixture of aducts was then analyzed on GC-MS. The identified compounds are summarized in
Table I.
Methyl (3S)-5-Iodo-3-methylpentanoate 5
Methyl hydrogen (R)-(+)-3-methylglutarate 4 (Aldrich, 1 g, 6.3 mmol) was reduced BH3 . Me2S (Aldrich,
0.8 ml, ca 8 mmol) using Rossi procedure14. Pentane solution of crude product was filtered over
silica gel provided crude hydroxy ester (0.91 g) which was dissolved in dry pyridine (4 ml) and the
solution was treated with 4-toluenesulfonyl chloride (1.20 g, 6.2 mmol) at 0 °C for 1 h and left in
freezer overnight. The reaction mixture was quenched with ice, extracted with ether (3 × 15 ml) and
combined extracts were washed with saturated aqueous CuSO4 solution. Crude tosylate (0.81 g, 2.70 mmol)
was stirred with NaI (0.61 g, 4.08 mmol) in dry acetone (15 ml) at room temperature for 20 h. Sol-
vent was evaporated at reduced pressure, obtained oil was dissolved in pentane (20 ml) and washed
with water (20 ml). Column silica gel chromatography yielded 368 mg (53% yield on starting 4) of
iodide 5, [α]D +1.87° (c 3.0, CHCl3). 13C NMR spectrum: 3.49 (C-5), 18.75 (C-6), 31.29 (C-3), 40.22
(C-4*), 40.61 (C-2*), 51.45 (CH3), 172.88 (C-1). 1H NMR spectrum: 0.97 d, 2 H, J = 6.6 (CH3-3);
1.74 ddt, 1 H, J = 5.8, 8.0, 8.0, 14.0 (H-4); 1.92 dddd, 1 H, J = 5.4, 7.1, 8.6, 14.0 (H-4); 2.10 m, 1 H
(H-3); 2.19 dd, 1 H, J = 7.8, 14.9 (H-2); 2.32 dd, 1 H, J = 6.1, 14.9 (H-2); 3.16 ddd, 1 H, J = 7.3,
8.3, 9.7 (H-5); 3.24 ddd, 1 H, J = 5.8, 8.5, 9.8 (H-5); 3.68 s, 3 H (CO2CH3). For C7H13IO2 (256.1)
calculated: 32.83% C, 5.12% H, 49.55% I; found: 32.77% C, 5.05 % H, 49.24% I.
(E)-6,10-Dimethyl-5,9-undecadien-1-yne 8
Following the published procedure15 a solution of allene (5 ml, 83 mmol) in dry ether (30 ml) was
metallated with butyllithium solution in hexanes (2.4 M, 23 ml) at –70 °C for 1 h, warmed to –20 °C
and stirred at this temperature for 0.5 h. The formed white precipitate of allene dianion was treated
with geranyl bromide (7, 3.58 g, 16.5 mmol) at –35 to –20 °C for 18 min and the reaction mixture
was allowed to warm to a room temperature and stirred for 30 min. The reaction mixture was poured
over ice and extracted with pentane. Column chromatography on silica gel in pentane provided
1.421 g (49% yield on 7) of 8. 13C NMR spectrum: 16.33 (CH3-6), 17.91 (CH3-10), 19.13 (C-3),
25.91 (C-11), 26.83 (C-8), 27.39 (C-4), 39.85 (C-7), 68.29 (C-1), 84.78 (C-2), 122.65 (C-5), 124.42
(C-9), 131.62 (C-10), 136.95 (C-6). 1H NMR spectrum: 1.60 s, 3 H (CH3-6); 1.62 s, 3 H (CH3-10);
1.68 d, 3 H, J = 0.6 (3 × H-11); 1.94 t, 1 H, J = 2.4 (H-1); 2.00 t, 2 H, J = 7.3 (H-7); 2.09 dt, 2 H,
J = 7.3, 7.3 (2 × H-8); 2.20–2.24 m, 4 H (2 × H-4, 2 × H-3); 5.10 tt, 1 H, J = 6.8, 1.2 (H-5); 5.18 bt,
1 H, J = 6.6 (H-9). For C13H20 (176.3) calculated: 88.58% C, 11.42% H; found: 87.82% C, 11.64% H.
(1E,5E)-1-Iodo-2,6,10-trimethyl-1,5,9-undecatriene16
9
A solution of dicyclopentadienylzirconium dichloride (422 mg, 1.44 mmol) in dry dichloromethane
(4 ml) was carefully treated with trimethylallane toluene solution (1 M, 1.44 ml) at room temperature
followed by acetylene 8 (470 mg, 1.44 mmol) solution in dichloromethane (1 ml). The formed yellow
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

Labial Gland Secretion of the Cuckoo-Bumblebee
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Collect. Czech. Chem. Commun. (Vol. 61) (1996)

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Valterova, Svatos, Hovorka:
solution was stirred for 20 h at room temperature, cooled to 0 °C and a solution of iodine (440 mg,
1.73 mmol) in dry tetrahydrofuran (2 ml) was added. After 30 min the reaction was stopped by a
careful adding of cold water and extracted with pentane–ether mixture (1 : 1). Purification on a silica
gel afforded 125 mg of 9 (27%). 13C NMR spectrum: 16.23 (CH3-6*), 17.93 (CH3-10*), 24.16 (CH3-2),
25.94 (C-11), 26.48 (C-8*), 26.91 (C-4*), 39.72 (C-7*), 39.89 (C-3*), 74.94 (C-1), 123.17 (C-5),
124.25 (C-9), 131.63 (C-10), 136.26 (C-6), 148.04 (C-2). 1H NMR spectrum: 1.59 s, 3 H (CH3-10);
1.60 s, 3 H (3 × H-11); 1.69 s, 3 H (CH3-6); 1.84 s, 3 H (CH3-2); 1.99 dt, 2 H, J = 7.9, 6.7 (2 × H-8);
2.05 t, 2 H, J = 7.6 (2 × H-7); 2.12 dt, 2 H, J = 7.4, 6.7 (2 × H-4); 2.22 t, 2 H, J = 7.5 (2 × H-3);
5.13–5.03 m, 2 H (H-5, H-9); 5.87 s, 1 H (H-1). Mass spectrum, m/z (%): 249 (M+ – 69, 1), 191
(M+ – 127, 9), 182 (6), 149 (2), 135 (7), 121 (11), 109 (6), 107 (12), 81 (29), 69 (100), 67 (10), 55
(10), 54 (19), 41 (47). For C14H23I (318.2) calculated: 52.83% C, 7.29% H, 39.87% I; found: 52.94% C,
7.80% H, and 39.95% I.
(3R)-Geranylcitronellol (3R)-2
a) Formation of zinciodide 6 (ref.17): Zinc dust (85 mg, 1.3 mmol) was suspended in dry tetrahy-
drofuran (0.2 ml) and subsequently activated with 1,2-dibromoethane (10 µl) and chlorotrimethylsi-
lane (10 µl). A solution of iodide 5 (256 mg, 1 mmol) in tetrahydrofuran (0.7 ml) was added to the
gray suspension of activated Zn at 25 °C during 20 min and the mixture was heated at 35–40 °C for
25 h. A clear solution of Zn organometallic compound 6 was obtained.
b) Pd catalyzed cross-coupling: Tetrakistriphenylphosphine palladium complex (44 mg, 0.04 mmol)
was dissolved in a solution of iodide 9 (124 mg, 0.39 mmol) in dry tetrahydrofuran (0.5 ml) on
yellow-brown solution. The solution of 6 (0.5 ml) prepared ad a) was added during 5 min, and the
mixture was stirred for 48 h. Solvents were removed at reduced pressure, the obtained residue dis-
solved in hexane (2 ml) and poured on silica gel column. Elution with hexane–ether mixture (1 : 1)
afforded methyl ester 10 (16 mg, 13% yield) which was reduced with LiAlH4 (10 mg, 0.25 mmol) in ether
(0.3 ml) forming (3R)-2 (14 mg, 98% yield). [α]D +5.2° (c 0.2, CHCl3). 13C NMR spectrum: 15.95,
19.54, 25.35, 25.65, 26.61, 26.76, 29.23, 29.40, 37.20, 39.71, 39.92, 62.24, 124.25, 124.43, 124.62,
1
131.27, 134.92, 134.94. H NMR spectrum: 0.91 d, 3 H, J = 6.6 (CH3-3); 1.04–1.72 m, 5 H (2 × H-2,
H-3, 2 × H-4); 1.60 m, 3 H (CH3-15*); 1.60 m, 6 H, (CH3-11, CH3-7); 1.68 q, J = 1.2 (3 × H-16); 1.95–2.09 m,
10 H, (2 × H-5, 2 × H-8, 2 × H-9, 2 × H-12, 2 × H-13); 3.68 m 2 H (2 × H-1); 5.08–5.13 m, 3 H
(H-6, H-10, H-14). Mass spectrum, m/z (%): 292 (2; M+), 277 (0.3), 249 (2), 223 (4), 208 (2), 191
(3), 179 (2), 163 (4), 149 (5), 136 (23), 121 (19), 109 (16), 95 (33), 81 (66), 69 (100), 55 (21), 41
(53). IR spectrum (KBr): 3 348 (OH), 2 963, 2 923, 2 872, 2 855 (C–H), 1 446, 1 375 (C–H), 1 060
(C–O). For C20H33O (292.5) calculated: 82.12% C, 12.40% H; found: 82.60% C, 12.03% H.
RESULTS AND DISCUSSION
Nineteen compounds were found in the labial gland secretions of the Psithyrus vestalis
males (Table I). The chemical structures of the compounds were determined based on
spectral methods (MS and IR) and NIST spectral library. Some of the abundant compo-
nents were isolated by micro-preparative column chromatography and TLC on silver
nitrate impregnated silica gel and the chemical identity confirmed by derivatizations
and spectral measurements. The alkalic hydrolysis of the isolated diterpenic acetate
gave a product of the same retention time and the mass spectrum as those of synthetic
sample of geranylcitronellol (3R-2). We concluded that this acetate is geranylcitronellyl
acetate 1. The position of the double bond in eicosen-1-ol was determined based on
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

Labial Gland Secretion of the Cuckoo-Bumblebee
1507
mass spectra of the prepared DMDS adduct. The fragments 117 and 273 (m/z) showed
that the double bond is located in the position 15. The configuration of the double bond
is based on infrared spectra in gas phase18. The presence of the 3 012 cm–1 band (=C–H
strech), and the absence of a 890 cm–1 band (E-wagg) in the measured gas phase IR
spectrum of 15-eicosenol established the Z-configuration of the double bond.
The derivatization with DMDS is a very good method for the determination of the
double bond position expecially in monounsaturated compounds. We were able to
determine the double bond positions in all our monounsaturated components of the
mixture, even the low abundant ones (Table I). However, the determination of the po-
sitions of double bonds in dienic compounds was not straightforward. Thus, the more
abundant isomer of heneicosadiene (14.5%) gave two adducts, each showing the addi-
tion of one DMDS molecule. One product showed the substitution of the 5,6-double
bond (m/z 117 and 269), while the second product had the two S–CH3 substituents in
the position 9,10 (m/z 171 and 215). Other DMDS adducts could not be found in the
derivatized mixture (Table I). The configurations of double bonds of minor components
of the extract could not be determined, however they have most likely Z-configuration.
The positions of the double bonds in all our identified unsaturated products were in
agreement with biosynthetic considerations published in the literature19.
Synthetic sample of (3R)-2 was prepared according to Scheme 1. Our synthetic pro-
cedure represents an efficient [3 + 1 + 6] extension procedure on geranyl bromide 7
which could be easily adopted to form both enantiomers of 2 and also other chiral
acyclic terpenoids. Geranylcitronellol 2 was prepared previously by Ahlquist20 using
Kolbe coupling of acids and later by Janicke21 starting from geranyl tosylate.
Geranylcitronellyl acetate 1 is the main component (47.8%) of the labial gland. This
compound has not been found in bumblebees before, however, the corresponding alco-
hol 2 is rather common. Geranylcitronellol 2 is a medium-abundant component (8.2%)
in our extract and has previously been found in other bumblebees and cuckoo-bumble-
bees, namely in Bombus terrestris1, Bombus hypnorum22, Bombus lapponicus23, Psi-
thyrus rupestris7, and it also formed a minor component in other bumblebee species.
(Z)-15-Eicosen-1-ol, one of the lower-abundant components (4.1%), was earlier found
in Psithyrus bohemicus19, a species the most closely related to P. vestalis in taxonomy
(the two mentioned Psithyrus species form the subgenus Ashtonipsithyrus24).
This work was financially supported by the Grant Agency of the Czech Republic (grant No.
203/95/0269) which is gratefully acknowledged. The author also thank Dr S. Vasickova for measure-
ments of IR spectra and to Dr A. B. Attygalle (Cornell University, Ithaca, U.S.A.) for GC-FTIR instru-
ment time. We are indebted to Dr D. Saman for the measurement and interpretation of some NMR
spectra.
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REFERENCES
1. Bergstrom G., Svensson B. G., Appelgren M., Groth I. in: Biosystematics of Social Insects (P. E.
Howse and J.-L. Clement, Eds), Vol. 19, p. 175. Academic Press, London and New York 1981.
2. Kullenberg B., Bergstrom G., Stallberg-Stenhagen S.: Acta Chem. Scand. 24, 1481 (1970).
3. Morse D. H. in: Social Insects (H. R. Hermann, Ed.), Vol. III, p. 245. Academic Press, New
York 1982.
4. Kullenberg B., Bergstrom G., Bringer B., Carlberg B., Cederberg B.: Zoon Suppl. 1, 25 (1973).
5. Kullenberg B.: Zoon Suppl. 1, 31 (1973).
6. Bergstrom G., Kullenberg B., Stallberg-Stenhagen S.: Chem. Scr. 4, 174 (1973).
7. Cedergerg B., Svensson B. G., Bergstrom G., Appelgren M., Groth I.: Nova Acta Regiae Soc.
Ups., Ser. V.C. 3, 161 (1984).
8. Andersson H.: Entomol. Tidskr. 113, 42 (1992).
9. Valterova I., Svatos A., Hovorka O.: 13th Annual Meeting of the International Society of
Chemical Ecology, Prague, August 19, 1996, (P. Drasar and I. Valterova, Eds), p. 73.
10. Bergman P.: Private communication.
11. Taber D. F.: J. Org. Chem. 47, 1351 (1982).
12. Brandsma L., Verkruijsse H. D.: Preparation of Acetylenes, Allenes and Cummulens, p. 143.
Elsevier, Amsterdam 1981.
13. Attygalle A. B., Jham G. N., Meinwald J.: Anal. Chem. 65, 2528 (1993).
14. Rossi R., Carpita A., Chini M.: Tetrahedron 41, 627 (1985).
15. Hooz J., Calzada J. G., McMaster D.: Tetrahedron Lett. 26, 271 (1985).
16. Negishi E., Van Horn D. E., Yoshida T.: J. Am. Chem. Soc. 107, 6639 (1985).
17. Knochel P., Chang M., Yeh P., Berk S. C., Talbert J.: J. Org. Chem. 53, 2392 (1988).
18. Attygalle A. B., Svatos A., Wilcox C., Voerman S.: Anal. Chem. 66, 1696 (1994).
19. Lanne B. S., Bergstrom G., Wassgren A.-B., Tornback B.: Comp. Biochem. Physiol. B 88, 631
(1987).
20. Ahlquist L., Olsson B., Stahl A.-B., Stallberg-Stenhagen S.: Chem. Scr. 1, 237 (1971).
21. Janicke L., Ulrich S. H.: Chem. Phys. Lipids 51, 159 (1989).
22. Svensson B. G., Bergstrom G.: Insectes Sociaux 24, 213 (1977).
23. Bergstrom G., Svensson B. G.: Chem. Scr. 4, 231 (1973).
24. May J.: Cmelaci v CSR, p. 147. Statni zemedelske nakladatelstvi, Praha 1959.
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