epi-cubebanes from Solidago canadensis

Article abstract of DOI:10.1016/S0031-9422(02)00006-7

GC-MS of the essential oil prepared by hydrodistillation of the green parts of a specimen of Solidago canadensis collected near Katowice, Poland, revealed two new sesquiterpene hydrocarbons. Their El mass spectra resembled the mass spectrum of β-ylangene (1) but the retention indices of the new compounds differed markedly from this known compound. After isolation of the new compounds by preparative GC their investigation by one- and two-dimensional NMR techniques resulted in the identification of 6-epi-α-cubebene (2) (minor constituent, 1.5%) and 6-epi-β-cubebene (3) (major constituent, 20.5%).

Full text of DOI:10.1016/S0031-9422(02)00006-7

Phytochemistry 59 (2002) 805–810
www.elsevier.com/locate/phytochem
epi-Cubebanes from Solidago canadensis
Adeleke A. Kasalia,b, Olusegun Ekundayob, Claudia Paula, Wilfried A. Koniga,*
aInstitut fur Organische Chemie, Universitat Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
¨
¨
bDepartment of Chemistry, University of Ibadan, Oyo State, Nigeria
Received 10 October 2001; received in revised form 14 December 2001
Abstract
GC–MS of the essential oil prepared by hydrodistillation of the green parts of a specimen of Solidago canadensis collected near
Katowice, Poland, revealed two new sesquiterpene hydrocarbons. Their EI mass spectra resembled the mass spectrum of b-ylangene (1)
but the retention indices of the new compounds differed markedly from this known compound. After isolation of the new compounds by
preparative GC their investigation by one- and two-dimensional NMR techniques resulted in the identification of 6-epi-a-cubebene
(2) (minor constituent, 1.5%) and 6-epi-b-cubebene (3) (major constituent, 20.5%). # 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Solidago canadensis; Essential oil; Structure elucidation; Cubebane; Sesquiterpene
1. Introduction
2. Results and discussion
The essential oils of several Solidago species have been
investigated before (Kalemba et al., 2001; Bulow and
Konig, 2000; Weyerstahl et al., 1993; Niwa et al., 1980).
In most cases germacrene D was found to be the
predominant constituent in Solidago species and the
occurrence of both enantiomers of this sesquiterpene
hydrocarbon has attracted particular interest (Niwa et al.,
1980; Schmidt et al., 1998; Bulow and Konig, 2000). In this
investigation of the green parts of a specimen of Solidago
canadensis collected near Katowice, Poland, (À)-germa-
crene D was also identified as the main constituent, how-
ever, another abundant sesquiterpene hydrocarbon with a
mass spectrum with m/z=120 as base peak very similar
to b-ylangene (1) (Joulain and Konig, 1998), but with a
different retention index, was detected by GC–MS of
the essential oil. In addition, another minor component,
also with a mass spectrum very similar to b-ylangene
but again with a different retention index was found in
this sample. After the isolation of the new compounds by
preparative GC their investigation by one- and two-
dimensional NMR techniques resulted in the identification
of the minor component as 6-epi-a-cubebene (2) and the
major component as 6-epi-b-cubebene (3).
The analysis of the essential oil of Solidago canadensis
by GC and GC–MS allowed the identification of (rela-
tive concentrations given in parentheses) trans-2-hexenol
(0.3%), a-pinene (2.9%), camphene (0.4%), b-pinene
(0.5%), myrcene (5.1%), limonene (2.7%), bornyl acetate
(1.8%), a-copaene (1.2%), b-elemene (1.4%), b-caryo-
phyllene (1.5%), a-humulene (0.3%), germacrene D
(23.8%), b-selinene (0.5%), bicyclogermacrene (5.0%), ꢀ-
amorphene (5) (0.9%) (Melching et al., 1997), g-cadi-
nene (4.1%), ꢀ-cadinene (0.4%), a-cadinene (0.6%),
gemacrene B (6.3%), 6-epi-cubenol (4) (2.9%) by com-
parison with a spectral library established under identical
experimental conditions (Joulain and Konig, 1998).
However, two compounds 2 (1.5%) and 3 (20.5%) could
not be identified by their mass spectra and retention
times and were isolated for NMR investigation.
From the molecular ion signal at m/z 204 of 2 the
elemental composition of C15H24 can be concluded.
This finding was confirmed by the 13C NMR/PEN-
DANT technique, which showed four primary (ꢀ 16.86,
20.19, 21.08, 21.12), three secondary (ꢀ 23.99, 32.98,
40.53), six tertiary (ꢀ 31.88, 33.85, 35.28, 35.86, 41.16,
120.73), and two quaternary carbons (ꢀ 32.73, 145.20).
From these data the presence of one double bond is
derived. As the elemental composition of C15H24 indi-
cates 4 unsaturations a tricyclic ring system in addition
* Corresponding author. Tel.: +49-40-42838-2824; fax: +49-40-
42838-2893.
E-mail address: wkoenig@chemie.uni-hamburg.de (W.A. Konig).
1
to the double bond must be present. The H NMR of 2
0031-9422/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0031-9422(02)00006-7

806
A.A. Kasali et al. / Phytochemistry 59 (2002) 805–810
shows three methyl doublets in the region of ꢀ=0.9–1.1
(H-12, H-13, H-14) and one down-field shifted methyl
signal at ꢀ =1.79 (H-15). The absorption of one olefinic
proton is detected ꢀ=at 4.98 (H-3). Two cyclopropane
protons show resonances at ꢀ=0.55–0.59 (H-6) and
1.26–1.30 (H-5). Two unusually high-field shifted proton
signals as parts of methylene groups appear at ꢀ=0.64–
0.72 (H-8a) and at 0.89–1.04 (H-9a). This high-field shift
of signals is attributed to the fact that the protons must be
in the anisotropic range of the cyclopropane ring system.
The two methylene protons are parts of adjacent
methylene groups as revealed by 1H1H-COSY (Table 1).
The other protons of each methylene group appear in
the aliphatic region of the spectrum: H-8b is located in a
multiplet together with two methine protons (ꢀ 1.37–
1.46 H-7/H-8b/H-11), H-9b is absorbing at ꢀ=1.46–
1.53. Two protons (H-2a, H-2b) belonging to one
methylene group appear as multiplets at ꢀ=2.26–2.35
Table 1
Two-dimensional NMR correlations of 6-epi-a-cubebene (2)
Proton and / or carbon
1H1H-COSY-couplings
HMBC-couplings
C-1 / C-9
H-2a / C-2
H-2b
–
H-2b, H-3, H-6, H-9b, H-10, H-14
H-3, H-6
H-2b, H-5, H-15
H-2a, H-3, H-15
H-2a, H-2b, H-15
–
–
H-2b, H-5, H-15
H-3 / C-3
C-4
H-2b, H-6, H-15
H-3, H-15
H-7/H-8b/H-11, H-8a
H-5 / C-5
H-6 / C-6
H-7/H-8b/H-11
C-7
H-2a, H-6
H-5, H-7/H-8b/H-11
H-6, H-12, H-13
–
–
H-5, H-7/H-8b/H-11, H-8a, H-9b, H-12, H-13
H-8a / C-8
H-9a
H-9b
H-9a, H-9b
H-8a, H-9b, H-10, H-14
H-8a, H-9a
H-6, H-7/H-8b/H-11, H-9b
–
–
H-5, H-9b
H-10 / C-10
C-11
H-9a, H-9b, H-14
–
H-7/H-8b/H-11, H-8a, H-12, H-13
H-7/H-8b/H-11, H-12, H-13,
H-12 / C-12/C-13
H-13
H-7/H-8b/H-11
H-7/H-8b/H-11
H-9a, H-10
–
H-14 / C-14
H-15 / C-15
H-9b, H-10
–
H-2a, H-2b, H-3

A.A. Kasali et al. / Phytochemistry 59 (2002) 805–810
807
and 2.62–2.70, respectively. The down-field shifted
methyl signal, which is split into a dd with J1=2 Hz and
H-10 in axial position. One of the protons in 2-position,
H-2a, shows a correlation to H-6, which itself couples to
H-13. As the trans-oriented cyclopropane protons H-5
and H-6 both couple to the methyl group H-13 the iso-
propyl group must be equatorial.
4
J2=4 Hz can be rationalised as one J coupling to the
5
olefinic proton (2 Hz) and the other as J homoallylic
scalar coupling in this rigid system with one of the pro-
tons H-2a or 2b. The corresponding crosspeaks appear
The elemental composition of C15H24 for 3 was cal-
culated from the molecular ion signal at m/z 204. Fif-
teen carbon atoms showed resonances in the 13C/HMQC
and were assigned as three primary (ꢀ 19.94, 20.86, 20.89),
five secondary (ꢀ 23.52, 29.16, 31.17, 32.94, 101.46,), five
tertiary (ꢀ 27.49, 31.34, 33.44, 33.93, 40.72) and two qua-
1
in the H1H-COSY (Table 1). The connectivity of the
different groups was established through two-dimen-
sional NMR experiments. The 1H1H-COSY revealed
the presence of an isopropyl group due to identical cross
peaks to the multiplet of H-7/H-8b/H-11. This finding
was further confirmed by the HMBC in which carbon
C-11 couples to both methyl doublets H-12 and H-13.
The same applies to carbon C-7, which also couples to
both methyl doublets (H-12, H-13) and additionally to
H-5, H-8a and H-9b. As H-9a couples to the methine
proton H-10 and the methyl doublet H-14, the con-
nectivities in the six-membered ring are established. The
adjacent quaternary carbon C-1reveals correlations to H-
2b, H-3, H-6, H-9b, H-10 and H-14, which is consistent
with the cubebane sesquiterpene skeleton.
The relative configuration of 2 was established through
NOE experiments. Proton H-5 shows dipolar couplings to
H-10, H-9a, H-8a and H-13 (Fig. 1). Consequently, all
these protons have to be in one plane. The lack of dipolar
correlation between H-5 and H-6 indicates a trans con-
figuration of these two protons. Additionally, H-6
doesn’t show cross peaks with the methylene or the
methine proton correlating with H-5. Methyl group H-
14, which is attached to C-10, shows close spatial rela-
tionship to both protons at carbon C-2. This can only
be rationalised if this methyl group is in equatorial and
1
ternary carbons (ꢀ 36.00, 154.47). In the H NMR two
olefinic protons (H-15a: ꢀ=4.80; H-15b: ꢀ=4.99) are
visible, which belong to one methylene group. Con-
sidering this fact together with the 13C data only one
double bond is accounted for in this tricyclic system as
indicated by the elementary composition C15H24.
The 1H NMR shows three methyl signals that are
represented by two doublets: one of which integrates to
six protons (ꢀ 0.91, H-13, ꢀ=1.01, H-12, H-14). Again
the presence of two up-field shifted methylene protons
H-8a (ꢀ 0.63–0.72) and H-9a (ꢀ 0.80–0.90) is noticed.
The cyclopropane protons H-6 (ꢀ 1.08–1.12) and H-5 (in
a multiplet with H-9b at ꢀ 1.44–1.49) do not appear as
much up-field shifted as expected for ordinary cyclopro-
pane protons. This may be caused by the neighbouring
double bond. The close proximity of the double bond to
the cyclopropane ring is revealed through scalar coupling
of H-15a to H-5/H-9b and even to H-6 (5J homoallylic).
H-15b in turn couples to H-5/H-9b (Table 2). These ole-
finic methylene protons H-15a and H-15b reveal addi-
tional scalar couplings to H-2a (ꢀ 1.63), H-3a (ꢀ 1.86–
1
1.96), and H-3b (ꢀ 2.05) in the H1H-COSY.
The six-membered ring is established through cou-
plings detected in the HMBC: Carbon C-1shows cor-
relations equivalent to those observed for compound 2.
The isopropyl group again is established through the
couplings of C-7 and of C-9/C-11 to both methyl groups
(H-12, H-13). Methyl group H-14 (appearing as one
1
doublet with H-12) gives one signal in the H1H-COSY
with the multiplet of proton H-2b/H-10 (ꢀ 1.73–1.82).
This connection is confirmed by the coupling of C-14 to
the same multiplet H-2b/H-10 and to H-9a. The two
methylene groups H-8a,b and H-9a,b show scalar cou-
1
plings in the H1H-COSY, by which they were identified
as adjacent. Carbon C-8 reveals more information: it
3
indicates a JCH coupling with H-6. From this informa-
tion the connectivity of compound 3 was deduced.
The NOE revealed the epi-cubebene structure as
depicted in Fig. 2. However, H-6 couples to H-2a, H-3a
and H-13 through space. Proton H-9a shows close
proximity to both neighbouring groups H-10 and H-14.
H-14 itself shows dipolar coupling to H-2a. From this
the same relative stereochemistry as in compound 2 is
deduced. This was further corroberated by acid cata-
lysed rearrangement of 3 and 2. The reaction products
Fig. 1. Observed important NOE couplings for compound 2.
(Couplings of other protons omitted for clarity.)

808
A.A. Kasali et al. / Phytochemistry 59 (2002) 805–810
Table 2
Two-dimensional NMR correlations of 6-epi-b-cubebene (3)
Proton and/or carbon
1H1H-COSY-couplings
HMBC-couplings
C-1
H-2a/C-2/C-10
–
H-2b, H-3a, H-3b
H-2a, H-2b/H-10, H-3b, H-5/H-9b, H-9a, H-12/H-14
H-2a, H-2b/H-10, H-3a, H-3b, H-5/H-9b, H-6, H-7/H-8b/H-11,
H-8a, H-9a, H-12/H-14
H-2b/H-10
H-3a/C-3
H-3b
H-2a, H-3a, H-3b, H-5/H-9b, H-6, H-9a, H-12/H-14
H-2a, H-3a, H-2b/H-10, H-5/H-9b
H-2a, H-3a, H-2b/H-10, H-5/H-9b
–
–
H-2a, H-2b/H-10, H-5/H-9b, H-15a, H-15b
–
C-4
H-2a, H-3a, H-3b, H-5/H-9b, H-6
H-2a, H-2b/H-10, H-3b, H-6, H-15a, H-15b
H-2a, H-2b/H-10, H-5/H-9b, H-7/H-8b/H-11, H-8a
–
H-5/H-9b/C-5
H-6 / C-6
H-7/H-8b/H-11
C-7
H-2b/H-10, H-3a, H-3b, H-6, H-8a, H-9a,
H-5/H-9b, H-7/H-8b/H-11
H-6, H-8a, H-9a, H-12/H-14, H-13
–
H-5/H-9b, H-7/H-8b/H-11, H-8a, H-9a, H-12/H-14, H-13
H-2b/H-10, H-5/H-9b, H-6, H-7/H-8b/H-11, H-9a
H-2b/H-10, H-7/H-8b/H-11, H-8a, H-12/H-14, H-13
H-7/H-8b/H-11, H-12/H-14, H-13,
–
H-8a/C-8
H-9a / C-9/C-11
H-12/H-14/C-12/C-13
H-13
H-5/H-9b, H-7/H-8b/H-11, H-9a
H-2b/H-10, H-5/H-9b, H-7/H-8b/H-11, H-8a
H-2b/H-10, H-7/H-8b/H-11, H-13
H-7/H-8b/H-11, H-12/H-14
–
C-14
H-15a/C-15
H-15b
H-2b/H-10, H-5/H-9b, H-9a
H-3a, H-3b, H-5/H-9b
H-2a, H-3a, H-3b, H-5/H-9b, H-6, H-15b
H-2a, H-3a, H-3b, H-5/H-9b, H-15a
–
tion of the hydrogen in position 6 in 1, 2 and 3 results in
a common intermediate after primary ionization and
identical or very similar secondary fragmentation in the
mass spectrometer. The occurrence of 2 and 3 in S.
canadensis has never before been reported. Interest-
ingly, in addition to b-ylangene (1) and b-copaene (9),
3 was obtained as a minor product by irradiation of
germacrene D at 254 nm (Bulow and Konig, 2000).
3. Experimental
3.1. General experimental procedures
3.1.1. Gas chromatography
Orion Micromat 412 double column instrument with
25 m fused silica capillaries with polysiloxane CPSil-5
and polysiloxane CPSil-19 (Chrompack); Carlo Erba
Fractovap 2150 or 4160 gas chromatographs with 25 m
fused silica capillaries with octakis(2,6-di-O-methyl-
3-O-pentyl)-g-cyclodextrin, heptakis(2,6-di-O-methyl-
3-O-pentyl)-b-cyclodextrin or heptakis(6-O-tert-butyl-
dimethylsilyl-2,3-di-O-methyl)-b-cyclodextrin in OV 1701
(50%, w/w), split injection; split ratio approx. 1:30;
FID; carrier gas 0.5 bar H2; injector and detector
Fig. 2. Observed important NOE couplings for compound 3.
(Couplings of other protons omitted for clarity.)
on treatment with acidic ion exchange resin were in each
case (+)-ꢀ-amorphene (5) and (+)-6-epi-cubenol (4). As
dehydration of (+)-4 yielded (À)-trans-calamenene (6)
among other products, the absolute configuration of 2,
3 and 5 was established as shown in Fig. 3.
ꢀ
temperatures 200 and 250 C, respectively.
It is quite remarkable that the mass spectra of both
new compounds are practically undistinguishable from
that of b-ylangene (1) and totally different from the
mass spectra of a- and b-cubebene (7 and 8) (Joulain
and Konig, 1998). This again shows that one should be
very cautious in identifying unknown compounds only
by mass spectral library search. Apparently b-orienta-
3.1.2. Preparative GC
Modified Varian 1400 and 2800 instrument, equipped
with a stainless steel column (1.85 mÂ4.3 mm) with 10%
polydimethylsiloxane SE-30 on Chromosorb W-HP or
with 6% heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-
methyl)-b-cyclodextrin in SE-52 (50%, w/w) on Chro-
mosorb W-HP; FID; helium as carrier gas at a flow rate

A.A. Kasali et al. / Phytochemistry 59 (2002) 805–810
809
Fig. 3. Reactions performed to elucidate the absolute configuration of the epi-cubebenes 2 and 3. [Reaction conditions: (a) Amberlyst1, benzene,
room temperature, 30 min; (b) SOCl2, pyridine/CHCl3 (1:1), 0 ꢀC, 40 min.]
of 240 ml/min; injector and detector temperatures were
ꢀ
3.2. Plant material and essential oils
200 C and 250 ꢀC, respectively.
Solidago canadensis was collected at Szczyrk near
Kattowice (Poland) in June 2001. The essential oils of
the plant were obtained by hydrodistillation (2 h) of the
fresh green parts of the plant using ca. 1ml of n-hexane
as collection solvent.
3.1.3. GC–MS
GC–MS measurements (EI, 70 eV) were carried out
with a Hewlett Packard HP 5890 gas chromatograph
coupled to a VG Analytical 70–250S mass spectrometer.
ꢀ
Ion source temperature: 200 C.
3.3. Isolation of single constituents of the essential oil
3.1.4. NMR-spectroscopy
NMR measurements were carried out with a Bruker
WM 500 instrument using TMS as internal standard.
The isolation was carried out using preparative GC:
The oil of Solidago cadensis was fractionated by prep.
ꢀ
GC usingꢀan SE-30 column at 100 C with a heating
3.1.5. Polarimetry
rate of 2 C/min and yielded 2 and 3 in one fraction.
The single compounds were obtained from that fraction
using a column with heptakis(6-O-tert-butyldimethylsi-
Measurements were carried out with a Polarimeter
341(Perkin Elmer) at 589 nm at 20 ꢀC. Due to very
small amounts of isolated compounds only the sense of
optical rotation is given to avoid inaccuracies.
Rearrangement reaction of (+)-2 and (+)-3 was per-
formed at room temperature in benzene by addition of
acidic ion exchange resin Amberlyst115. A sample was
taken after 30 min and analysed by GC and GC–MS.
ꢀ
lyl-2,3-di-O-methyl)-b-cyclodextrin (110 C isothermal).
4 was isolated from the essential oil using a column with
SE 30 as stationary phase.
3.3.1. 6-epi-ꢁ-Cubebene (2)
3aa,3bb,4,5,6,7-hexahydro-3,7-dimethyl-4-(1-methy-
lethyl) - 1H - cyclopenta[1,3]cyclopropa[1,2]benzene, col-
ourless oil, RICPSIL5:1412, sense of optical rotation
(benzene): (+) ; 1H NMR (500.1MHz, C 6D6): ꢀ=0.55–
0.59 (m, 1H, H-6), 0.64–0.72 (m, 1H, H-8a), 0.93 (d, 3H,
H-12, J=6.1Hz), 0.89–1.04 ( m, 1H, H-9a), 1.02 (d, 3H,
H-13, J=5.9 Hz), 1.07 (d, 3H, H-14, J=7.1Hz), 1.26–
1.30 (m, 1H, H-5), 1.37–1.46 (m, 3H, H-7, H-8b, H-11),
1.46–1.53 (m, 1H, H-9b), 1.79 (dd, 3H, H-15, J=2.0, 4.0
ꢀ
Dehydration of (+)-4 was performed at 0 C in pyri-
dine/chloroform (1:1) by addition of thionyl chloride
during 40 min. The reactions was quenched by addition
of saturated aq. NaHCO3 solution. The aqueous layer
was extracted three times with chloroform. The organic
layer was washed twice with saturated aq. NaHCO3
solution and dried over anhydrous MgSO4 prior to GC
and GC–MS investigation.

810
A.A. Kasali et al. / Phytochemistry 59 (2002) 805–810
Hz), 1.82–1.92 (m, 1H, H-10), 2.26–2.35 (m, 1H, H-2a),
2.62–2.70 (m, 1H, H-2b), 4.98 (d, 1H, H-3, J=1.5 Hz);
13C NMR (125.75 MHz, C6D6): ꢀ=16.86 (q, C-15),
20.19 (q, C-14), 21.08 (q, C-13), 21.12 (q, C-12), 23.99 (t,
C-8), 31.88 (d, C-10), 32.73 (s, C-1), 32.98 (t, C-9), 33.85
(d, C-11), 35.28 (d, C-6), 35.86 (d, C-5), 40.53 (t, C-2),
41.16 (d, C-7), 120.73 (d, C-3), 145.20 (s, C-4); MS (EI,
70 eV), m/z (rel. Int.): 39 (16), 41 (46), 43 (16), 55 (24),
77 (20), 79 (28), 81(20), 91(45), 93 (23), 105 (46), 107
(22), 119 (23), 120 (100), 121 (16), 161 (72), 204 (12).
1.48–1.58 (m, 2H, H-2a, H-11), 1.61–1.69 (m, 4H, CH3-
4, H-8b, H-10), 1.88–2.05 (m, 2H, H-2b, H-3b), 2.42 (br.
s, 1H, H-6), 5.20 (br. s, 1H, H-5); 13C NMR (100.6
MHz, C6D6): ꢀ=14.8 (q, C-14), 20.7 (q, C-12), 21.9 (q,
C-13), 23.4 (q, C-15), 26.8 (t, C-8), 28.9 (d, C-11), 29.9
(t, C-3), 30.9 (d, C-10), 31.0 (t, C-9), 35.1( t, C-2), 42.7
(d, C-7), 45.6 (d, C-6), 71.8 (s, C-1), 121.1 (d, C-5), 134.7
(s, C-4); MS (EI, 70 eV), m/z (rel. int.): 39 (36), 41(100),
43 (83), 53 (25), 55 (41), 77 (28), 79 (27), 81(29), 91(35),
93 (26), 105 (33), 119 (25), 161 (45), 179 (77), 204 (12),
222 (2).
3.3.2. 6-epi-ꢂ-Cubebene (3)
2,3,3aa,3bb,4,5,6,7-Octahydro-7-methyl-3-methylene-4-
(1-methylethyl)-1H-cyclopenta[1,3]cyclopropa[1,2]benzene,
colourless oil, RICPSIL5:1449, sense of optical rotation
(benzene): (+) ; 1H NMR (500.1MHz, C 6D6): ꢀ=0.63–
0.72 (m, 1H, H-8a), 0.80–0.90 (m, 1H, H-9a), 0.91 (d,
3H, H-13, J=6.3 Hz), 1.01 (d, 6H, H-12, H-14, J=6.0
Hz), 1.08–1.12 (m, 1H, H-6), 1.36–1.44 (m, 3H, H-7, H-
8b, H-11), 1.44–1.49 (m, 2H, H-5, H-9b), 1.63 (dd, 1 H,
H-2a, J=8.2, 12.0 Hz), 1.73–1.82 (m, 2H, H-2b/H-10),
1.86–1.96 (m, 1H, H-3a), 2.05 (dd, 1H, H-3b, J=9.1,
16.7 Hz), 4.80 (s, 1H, H-15a), 4.99 (s, 1H, H-15b); 13C
NMR (125.8 MHz, C6D6): ꢀ=19.94 (q, C-14), 20.86 (q,
C-12), 20.89 (q, C-13), 23.52 (t, C-8), 27.49 (d, C-6),
29.16 (t, C-3), 31.17 (t, C-2), 31.34 (d, C-10), 32.94 (t, C-
9), 33.44 (d, C-11), 33.93 (d, C-5), 36.00 (s, C-1), 40.72
(d, C-7), 101.46 (t, C-15), 154.47 (s, C-4); MS (EI, 70
eV), m/z (rel. int.): 39 (18), 41 (50), 43 (16), 55 (29), 77
(20), 79 (27), 81 (25), 91 (48), 93 (23), 105 (51), 107 (20),
119 (27), 120 (100), 121 (15), 161 (90), 204 (12).
Acknowledgements
We would like to acknowledge the financial support
from DAAD for A.A. Kasali and of the Fonds der
Chemischen Industrie. We are grateful to Dr. V. Sinn-
well, University of Hamburg, for his support in obtain-
ing the NMR spectra and to Mrs. A. Meiners and Mr.
M. Preusse, University of Hamburg, for their assistance
in the GC–MS investigations.
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