Simple and highly efficient preparation and characterization of (-)-lupanine and (+)-sparteine

Article abstract of DOI:10.1016/j.tet.2011.07.080

In a simple and convenient way, we have improved the non-chromatographic isolation of optically pure (-)-2-oxosparteine ((-)-lupanine) and (+)-sparteine. The fast and efficient method for the determination of the ee of bisquinolizidine alkaloids has been proposed. A relatively simple simple ¹H NMR method has been applied for evaluation of the % ee of enantiomers of the lupanines and sparteines with the chiral dibenzoyltartaric acids as the shift reagents. The ¹H NMR spectra of the bases and the new salts in polar solvents have been measured. The results are confirmed by chiral HPLC method. Additionally, for the first time X-ray analysis of the salt of (-)-lupanine has been performed. The improved method of purification of bisquinolizidine alkaloids will considerably facilitate the employment of these alkaloids as chiral ligands in asymmetric reactions and as pharmacological tools.

Full text of DOI:10.1016/j.tet.2011.07.080

Tetrahedron 67 (2011) 7787e7793
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Simple and highly efficient preparation and characterization of (ꢀ)-lupanine and
(þ)-sparteine
Anna K. Przyby1 *, Maciej Kubicki
ꢀ
Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 April 2011
Received in revised form 5 July 2011
Accepted 26 July 2011
Available online 2 August 2011
In a simple and convenient way, we have improved the non-chromatographic isolation of optically pure
(ꢀ)-2-oxosparteine ((ꢀ)-lupanine) and (þ)-sparteine. The fast and efficient method for the de-
termination of the ee of bisquinolizidine alkaloids has been proposed. A relatively simple simple 1H NMR
method has been applied for evaluation of the % ee of enantiomers of the lupanines and sparteines with
the chiral dibenzoyltartaric acids as the shift reagents. The 1H NMR spectra of the bases and the new salts
in polar solvents have been measured.
The results are confirmed by chiral HPLC method. Additionally, for the first time X-ray analysis of the salt
of (ꢀ)-lupanine has been performed. The improved method of purification of bisquinolizidine alkaloids
will considerably facilitate the employment of these alkaloids as chiral ligands in asymmetric reactions
and as pharmacological tools.
Keywords:
(ꢀ)-2-Oxosparteine
(þ)-Sparteine
Quinolizidine alkaloids
Optical resolution
NMR spectroscopy
X-ray diffraction
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
(ꢀ)-Lupanine has also been obtained by catalytic hydrogenation
of (þ)-5,6-dehydrolupanine on PtO2.8 It was established that the
Quinolizidine alkaloids with the sparteine, cytisine or lupinine
skeleton represent one of the largest groups of compounds dis-
tributed within the Leguminosae, the third largest family of flow-
ering plants.1 The extracts of the lupin alkaloids obtained from the
seeds of Lupinus albus have been used in traditional medicine for
the treatment of diabetes, eczema and as anti-inflammatory
agents.2 The pharmaceutical activity of these extracts is due to
the presence of derivatives of sparteine. The main structural types
of quinolizidine alkaloids are those with the sparteine skeleton and
these alkaloids are very interesting from a stereochemical point of
view.3 They also play an important role in many chemical reactions
and (ꢀ)-sparteine is still a popular chiral ligand in many reactions.4
The second most abundant lupin alkaloid after sparteine is 2-
oxosparteine (lupanine).5 However, the most widespread in na-
ture is the (ꢁ)-lupanine enriched with (þ)-lupanine isomer6 opti-
absolute configuration of (þ)-5,6-dehydrolupanine (Fig. 1) was the
same as those of (ꢀ)-lupanine, (ꢀ)-anagyrine, (ꢀ)-N-methylcytisine
and (ꢀ)-cytisine (Fig.1). It is presumed that the compounds have the
same intermediates and similar pathways of biosynthesis.8
Since (ꢀ)-sparteine has found numerous applications in asym-
metric reactions, the interest in synthesizing (þ)-sparteine has also
increased. The synthesis of (þ)-sparteine is time consuming, so
surrogates of (þ)-sparteine were taken under consideration.9,10 One
of them is N-methyl-2-deoxotetradehydrocytisine (Fig. 1) that was
obtained by reduction of naturally occurring compound (ꢀ)-cyti-
sine.10 The (þ)-enantiomers of sparteine derivatives can be obtained
by synthetic modification of (þ)-2-oxosparteine by introducing se-
lected substituents at the C-2 position. These compounds readily
form complexes with metals and can be potential chiral bases for
stereochemical reactions.11 (þ)-Sparteine was obtained by resolu-
tion of (ꢁ)-lupanine with (ꢀ)-(1R)-10-camphorsulfonate dihydrate
and then reduction.12
Due to the increasing interest in sparteine enantiomers, we de-
cided to perform the separation of a racemic mixture of 2-
oxosparteine enantiomers by crystallization with chiral acids. The
next step was reduction of the two enantiomers of lupanine from
which the corresponding enantiomers of sparteine were obtained.
Up to now, (ꢀ)-lupanine has been found in the seeds of L. albus cv.
Satmarean, in which (ꢁ)-lupanine is enriched with (ꢀ)-lupanine.
The sample was isolated by HPLC using a chiral stationery phase and
cally pure (ꢀ)-lupanine ½a D20
ꢀ57.5 (c 0.15, EtOH) was isolated from
ꢂ
another Leguminosae plantdLygos raetam var. sarcocarpa.7 As well
as the above mentioned (ꢀ)-lupanine, this extracted mixture was
also found to contain (ꢀ)-anagyrine, (ꢀ)-cytisine and (ꢀ)-N-
methylcytisine (Fig. 1), having the same absolute configuration of
the methylene bridge (7R,9R).
* Corresponding author. Tel.: þ48 61 829 1004; fax: þ48 61 829 1505; e-mail
addresses: annaprz@amu.edu.pl (A.K. Przyby1), mkubicki@amu.edu.pl (M. Kubicki).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.07.080

7788
A.K. Przybył, M. Kubicki / Tetrahedron 67 (2011) 7787e7793
HPLC analysis with a chiral column (rt 26.139 min). We also
obtained (þ)-lupanine ½a D20
þ81.2 (c 1, EtOH) in 32% yield by
ꢂ
crystallising the (þ)-lupanine from the mother liquid with
(ꢀ)-dibenzoyltartaric acid. (þ)-Lupanine was also formed in 99.9%
by chiral HPLC (rt 28.120 min).
The same size optical rotations of the (ꢀ) and (þ) enantiomers
in the opposite directions suggested a complete resolution. How-
ever, we required an independent confirmation of enantiopurity of
the isomers. Our methodology of evaluation of enantiopurity as
described below showed that lupanine enantiomers (ꢀ) and (þ)
were more than 99% pure.
We have also developed a simple NMR method for determining
the % ee of the lupanines. The method relies on salt formations. We
used the same optically pure chiral acids that were applied for the
resolution of the (ꢀ) and (þ)-lupanine. The quantitative and rapid
formation of salts offers an alternative to other more expensive
reagents, such as chiral lanthanide shift reagents.
Well-separated peaks of H10(eq) between 4.47 and 4.27 ppm
were observed in the 1H NMR spectrum (500 MHz) of (ꢁ)-lupanine
with (þ)-2,3-dibenzoyl-
D-tartaric acid (Fig. 2b). The important
signal of H10(eq) as a doublet of triplets is shown in Fig. 2. The salt
of each enantiomer displayed a signal that overlapped with some of
those observed in the diastereomeric salts of the racemic mixture
(Fig. 2). Such overlaps occurred at 4.46 and 4.44 ppm for the
(ꢀ)-isomer (99% ee) and at 4.44 and 4.42 ppm for the (þ)-isomer in
the selected area (99% ee).
For the first time, the NMR spectra of lupanine were measured in
polar solvents, such as MeOD and DMSO. On the basis of these data,
thesolventeffectsweremeasuredandtheresultsareshowninTable 1.
Upon reduction of (ꢀ)-lupanine and (þ)-lupanine, the isomers
(þ)-sparteine and (ꢀ)-sparteine were obtained in 84% and 85%
yield, respectively (Fig. 3). (þ)-Sparteine is the target model com-
pound used in stereoselective reactions.5
The changes in the 1H NMR spectra of (ꢁ)-sparteine (syn-
thesised from (ꢁ)-lupanine) with a chiral acid were similar to those
observed for the lupanine salts. However, the best resolution of the
key signals of H-17(eq) (2.38 ppm) and H10(eq) (2.56 ppm) was
obtained with (ꢀ)-2,3-dibenzoyl-
D-tartaric acid (Fig. 4, Table 3).
The salts of each enantiomer of sparteine with (ꢀ)-2,3-dibenzoyl-
D
-
Fig. 1. Quinolizidine alkaloids: (ꢀ)- and (þ)-lupanine, (ꢀ)-anagyrine, (þ)-5,6-
dehydrolupanine, (þ)- and (ꢀ)-sparteine, (ꢀ)-cytisine, (ꢀ)-N-methylcytisine and
(þ)-N-methyl-2-deoxotetradehydrocytisine.
tartaric acid displayed a signal that overlapped with some of those
observed in the diastereomeric salts of the racemic mixture (Fig. 4).
The signal of H17(eq) occurred at 2.70 ppm as a doublet of dou-
blets for the salt of the (ꢀ)-isomer and at 2.65 ppm for the salt of
(þ)-isomer in the selected area (Fig. 4). Another signal that can
differentiate between the enantiomers is the chemical shift of H-10.
In the spectrum of the (ꢀ)-sparteine salt it is found at 2.60 as a broad
multiplet, while in the spectrum of (þ)-sparteine it is at 2.53 as
a doublet (Fig. 4).
The percentage of enantiomeric contamination was measured
according to a literature method13 to be 99%. In order to measure %
ee, to each sample, we added an opposite isomer together with the
chiral reagent in steps of 0.5% (wt %). This amount did not cause
detectable changes in the signals. Although, after addition of 1%
a weak signal of the minor isomer, which was distinguishable from
the background noise could be observed. These indicate that the
detection limit of % ee was between 1 and 0.5%. Thus, our resolved
compounds were at least 99% optically pure. That finding was
confirmed by chiral HPLC method.
The structure of the newly obtained salt of (ꢀ)-lupanine was
confirmed by X-ray crystallographic analysis (Fig. 5). The lupani-
nium cation is protonated at the N16 nitrogen atom, and one of the
carboxylic groups of the tartrate anion is deprotonated. This was
proved by the successful location of these hydrogen atoms as well
as by the bond length (carboxylate) and angle (lupaninium) pat-
terns. The crystal structure also contains two water molecules per
cationeanion pair. All these structural components are connected
the optical purity 99% of (ꢀ)-lupanine ½a D20
ꢀ80.8 (c 0.51, EtOH) was
ꢂ
determined.6
This work presents an improved methodology for extraction of
lupanine from L. albus, followed by isolation of the optically pure
enantiomers of (þ)-lupanine and (ꢀ)-lupanine on a preparative
scale by resolution using dibenzoyltartaric acids. The reduction of
(þ)-lupanine and (ꢀ)-lupanine then led to (ꢀ)-sparteine and
(þ)-sparteine, respectively. Detailed NMR spectroscopic and X-ray
crystallographic analyses of these alkaloids are performed.
2. Results and discussion
Our aim was to develop a relatively fast and effective method for
separation of the pure enantiomers of lupanine, as the literature
procedure was time-consuming and ineffective on a large scale. The
extraction of a racemic mixture of naturally occurring lupanine
from L. albus as well as the optical resolution of the enantiomers is
described in the Experimental section. The NMR spectroscopic data
of lupanine and sparteine are given in Tables 1e3.
By crystallisation of the racemic mixture of lupanine with
(þ)-dibenzoyltartaric acid we obtained (ꢀ)-lupanine with ½a D20
ꢂ
ꢀ81.2 (c 1, EtOH) in 37% yield. An ee of 99.9% ee was found using

A.K. Przybył, M. Kubicki / Tetrahedron 67 (2011) 7787e7793
7789
Table 1
1H NMR and 13C NMRechemical shifts of lupanine in MeOD and DMSO
Atom C
d
[ppm]
Atom H
d
[ppm]
d [ppm]
MeOD
DMSO
D¼d
MeODedDMSO
MeOD
J [Hz]
DMSO
J [Hz]
2
3
174.00
33.7
169.7
32.6
4.28
1.09
d
d
d
d
d
3a
3b
4a
4b
5a
5b
ax
eq
eq
ax
ax
eq
w2.35 m
m; 2H
w2.21
m; 2H; 8.7; 9.3; 4.0; 4.6; 0.6
4
5
20.3
28.1
19.2
26.7
1.14
1.45
1.64e1.58
1.83
1.64e1.58
1.81
3.42
w2.12
2.14
1.36
1.65
4.42
2.58
1.63
1.64e1.58
1.40
1.30
1.73
m; 3H
1.52
1.70
1.45
1.71
3.28
1.98
2.00
1.19
1.51
4.29
2.43
1.46
1.47
1.26
1.15
1.64
1.43e1.37
m
dddd 11.4; 7.6; 4.8; 2.7; 2.1
m; 3H
dddd 9.5; 5.8; 3.6; 2.3; 1.1
dddd 11.2; 7.0; 5.0; 2.0
m
dddd 12.4; 4.2; 4.1; 2.2
ddd 12.4; 4.6; 2.3
m; br s
ddd 13.2; 4.9; 2.5
dd 13.2; 2.8
ddd 8.3; 3.4; 1.6
m
ddd 10.0; 4.0; 2.4
dddd 11.1; 7.0; 5.0; 1.9
6
7
8
62.3
33.6
27.3
59.8
31.6
26.2
2.47
1.93
1.1
6 ax
7 equiv
m
8
8
a
b
eq
ax
dddd 11.7; 4.1; 4.0; 2.1
ddd 11.7; 4.6; 2.4
m
ddd 12.9; 4,8; 2,4
dd 12.9; 2.07
m
m
dddd 14.6; 13.2; 11.6; 3.8
ddddd 12.7; 9.1; 8.0; 4.3; 3.7
m 12.7; 6.2; 4.8; 2.8; 2.6; 1.4
m; 2H
9
10
36.3
48.0
34.5
45.9
1.78
2.12
9 eq
10
10
a
b
eq
ax
11
12
65.7
34.2
63.4
32.8
2.27
1.37
11 ax
m
m; 3H
12
12
13
13
14
14
15
15
17
17
a
b
a
b
a
b
a
b
a
b
eq
ax
ax
eq
eq
ax
ax
eq
ax
eq
dddd 14.7; 12.8; 11.2; 3.7
dddd 12.8; 9.0; 7.9; 4.2; 3.9
dddddd 12.8; 4.7; 4.1; 3.6; 3.3; 1.4
m; 2H
13
14
15
17
25.7
25.9
56.8
53.9
24.4
24.8
54.8
52.1
1.35
1.08
1.99
1.75
1.58e1.55
1.93
2.79 d
1.95
ddd 12.0; 11.5; 4.5
ddd 11.5; 5.6; 4.5; 3.0
dd 12.2; 3.9
1.79
2.68
1.82
2.72
ddd 11.5; 11.4; 3.2
d 11.5
dd 11.4; 3.7
2.87
dd 12.2; 10.1; 2.1
dd 11.4; 10.1; 1.3
Table 2
Comparison of the chemical shifts (13C NMR, TMS) of sparteine measured in different solvents
14
15
At C
C6D6
CDCl3
MeOD
D2O pH 1016
D
¼
dCDCl3
ꢀdC6C6
D
¼
d
MeODedC6C6
D
¼
dMeODꢀdCDCl3
D
¼
dD2O
2.45
ꢀdCDCl3
D
¼
dD2O dMeOD
ꢀ
2
3
4
5
6
7
8
9
10
11
12
13
14
15
17
56.48
26.23
25.10
29.56
66.51
33.75
28.02
36.97
62.29
64.40
35.18
25.51
26.58
55.78
54.00
56.0
25.7
24.5
29.1
66.2
33.0
27.4
36.0
61.8
64.1
34.5
24.7
25.8
55.2
53.4
57.41
26.19
25.70
30.46
68.02
34.30
28.34
37.25
62.95
65.63
34.96
25.89
26.72
56.55
54.19
58.45
27.50
26.00
31.88
68.70
35.35
28.90
35.51
63.88
65.85
25.46
25.75
20.69
55.49
49.87
0.48
0.53
0.60
0.46
0.31
0.75
0.62
0.97
0.49
0.30
0.68
0.81
0.78
0.58
0.60
0.93
0.04
0.60
0.90
1.51
0.55
0.32
0.28
0.66
1.23
0.22
0.38
0.14
0.77
0.19
1.41
0.49
1.20
1.36
1.82
1.30
0.94
1.25
1.15
1.53
0.46
1.19
0.92
1.35
0.79
1.04
1.31
0.30
1.42
0.68
1.05
0.56
1.80
1.50
2.78
2.50
2.35
1.50
ꢀ0.49
ꢀ1.74
2.08
1.75
0.93
0.22
ꢀ9.04
ꢀ9.5
1.05
ꢀ0.14
ꢀ6.03
ꢀ1.06
ꢀ4.32
ꢀ5.11
0.29
ꢀ3.53
into a three-dimensional network by means of the relatively strong
hydrogen bond network (Table 4). The NH group acts as a donor for
a hydrogen bond with the deprotonated carboxylate group and the
carboxylic group acts as a donor for a hydrogen bond with the
oxygen atom from one of the water molecules. The water molecules
are involved in hydrogen bonds with the remaining oxygen atoms.
The lupaninium cation (Fig. 6) has the typical conformation of
the rings: half-chair, chair, boat, chairdring C is inverted from the
boat conformation typical for the free base (e.g., lupanine itself17).
Additionally, to analyze the influence of solvent on the chemical
shifts of sparteine, the NMR data obtained in MeOD were compared
with those available in the literature (only in non-polar solvents,
such as CDCl3 and C6D6). On the basis of this comparison, the dif-
ferences in the chemical shifts were calculated. The solvent effect is
illustrated in Tables 2 and 3. This bisquinolizidine compound was
chosen as a model compound with ring C as a pure boat conformer.
According to Brukwicki the chemical shifts of C-12 and C-14 as well
as the JH7eH17b coupling constantof sparteine permit the calculation
of the conformational equlibria in bisquinolizidine system.3 Thenew
values of the chemical shifts C-12, C-14 and JH7eH17b for the model
with 100% boat conformer are: 34.9 ppm, 26.0 ppm and 10.8 Hz,
respectively. While for the model with 100% chair conformer, the
corresponding values are: 21.0 ppm (C-12), 18.0 ppm (C-14) and
1.9 Hz (JH7eH17b) (Tables 2 and 3). The calculations based on the
Haasnoot equation have been published.3 However, it seems that
these data are correct for the NMR spectra measured only in CDCl3,
because the values of chemical shifts and coupling constant in MeOD
are higher than those mentioned above needed for the calculation:
35.0 ppm, 26.7 ppm and 11.4 Hz, respectively. For this reason it is
impossible to use the above-mentioned equation for the calculation
of conformational equilibrium of sparteine in polar solvents, such as
MeOD or DMSO. This result emphasises that for the identification of
conformational equilibrium it is necessary to take under consider-
ation the influence of the solvent and compare the values of chem-
ical shifts and coupling constants obtained in the same solvent.
3. Conclusions
The most abundant lupin alkaloid besides sparteine is 2-
oxosparteine (lupanine). In order to provide ready access to gram

7790
A.K. Przybył, M. Kubicki / Tetrahedron 67 (2011) 7787e7793
Table 3
Comparison of the chemical shifts of sparteine (1H NMR, TMS) measured in different solvents
D2O pH 1016
D¼
dCDCl3
ꢀdC6C6
D
¼dMeODꢀdCDCl3
D
¼
dD2O dMeOD
ꢀ
14
15
At H
C6D6
CDCl3
MeOD
2
2
3
3
4
4
5
5
6
7
8
8
9
10
10
11
12
12
13
13
14
14
15
15
17
17
a
b
a
b
b
a
a
b
eq
ax
ax
eq
ax
eq
ax
eq
2.62
1.88
1.56
1.44
1.12
1.62
1.40
1.09
1.62
1.74
1.02 ax
2.34 equiv
1.41
1.96
2.47
2.11
1.45
1.37
1.25
1.66
1.65
1.51
2.04
2.64
1.89
2.01
2.01
1.30
1.67
1.35
1.20
1.67
1.84
1.00
2.01
1.42
1.96
2.48
1.90
1.45
1.34
1.67
1.67
1.51
1.51
1.89
2.64
2.30
2.65
2.70 dd 11.04; 5.7
1.98 ddd 15.3; 11.3; 4.1
1.59 m
2.92
2.10
1.50
1.62
1.40
1.77
1.55
1.38
2.55
1.87
1.60
2.07
1.89
2.64
3.04
3.44
2.03
1.48
1.52
1.87
1.77
1.52
3.1
0.02
0.01
0.45
0.57
0.18
0.05
ꢀ0.05
0.11
0.05
0.1
ꢀ0.02
ꢀ0.33
0.01
0
0.01
ꢀ0.21
0
ꢀ0.03
0.42
0.01
ꢀ0.14
0
ꢀ0.15
ꢀ0.12
ꢀ0.17
ꢀ0.02
0.06
0.09
ꢀ0.42
ꢀ0.42
d
0.22
0.12
ꢀ0.09
0.03
d
1.59 m
1.30e1.25 m (2H)
1.74e1.71 m (2H)
1.40 ddd 16.7; 12.7; 3.8
1.30e1.25 m (2H)
1.79 bd 11.3
1.85 m
1.13 dt 12.3; 4.7
2.07 m
d
d
0.05
d
0.15
d
0.12
0.01
0.13
0.06
0.08
0.08
0.08
0.20
0.08
d
0.76
0.02
0.47
0
0.39
0.60
0.48
1.34
0.50
d
b
a
ax
eq
1.50 m
b
a
ax
eq
2.04 dd 11.1; 2.5
2.56 ddd 11.1; 4.4; 2.2
2.10 m
b
a
a
b
b
a
a
b
a
b
ax
eq
ax
eq
ax
eq
ax
eq
ax
eq
1.53 m
1.38e1.33 m (2H)
1.38e1.33 m (2H)
1.74e1.71 m (2H)
1.55 m (2H)
1.55 m (2H)
2.05 m
2.78 bd 11.4
2.38 dd 11.4; 3.4
2.72 dd 11.4; 11.4
d
d
d
d
0.04
0.04
0.16
0.14
0.08
0.07
0.22
ꢀ0.03
1.05
0.32
1.20
0.39
2.76
2.47
2.67
3.1
3.58
3.11
and (þ)-2,3-dibenzoyl-
D-tartaric acid was developed. This quanti-
tative and rapid formation of salts offers an alternative to other
much more expensive used reagents, such as chiral lanthanide shift
reagents.
In this work, a new method of obtaining (þ)-sparteine by optical
resolution of racemic mixture of lupanine followed by reduction is
proposed as well as a new application of the well known chiral
dibenzoyltartaric acids has been introduced.
Additionally, the influence of solvents on the NMR spectra of
lupanine and sparteine has been analyzed (Tables 1e3).
The improved method of resolution of bisquinolizidine alkaloids
will considerably facilitate the employment of these alkaloids as
chiral ligands in asymmetric reactions and as pharmacological
tools.
4. Experimental
4.1. General techniques
Plant material: The lupin seeds of L. albus cv. BAC (Leguminosae
plant), Gene Bank, Experimental Station of Plant, Wiatrowo,
62e100 Wa˛growiec, Poland.
Fig. 2. The chemical shift of H10
a
(eq) in the spectra of: (a) (ꢁ)-lupanine; (b) the salt of
(ꢁ)-lupanine and (þ)-2,3-dibenzoyl-D-tartaric acid; (c) the salt of (ꢀ)-lupanine and
(þ)-2,3-dibenzoyl-D-tartaric acid; (d) (þ)-lupanine and (þ)-2,3-dibenzoyl-D-tartaric
acid (1H NMR, MeOD, TMS, 400 MHz).
Thin layer chromatography (TLC) was performed using alu-
minium sheets precoated with silica gel 60 F254 (Merck). Flash
chromatography was carried out on silica gel 60 G F254 (Merck).
Melting points were determined on a Boetius apparatus (PHMK 05
VEB Wagetechnik Rapido, Radebeul). Low- and high-resolution
electron ionization (EIMS) mass spectra were recorded using
a model 402 two-sector mass spectrometer (AMD Intectra GmbH,
Harpsted, Germany; ionising voltage 70 eV, accelerating voltage
8 kV, resolution 1000 for low-resolution and 10,000 for high-
resolution mass spectra). IR spectra were obtained on an FTIR
Bruker IFS 113 v spectrometer (KBr pellets technique).
Fig. 3. Reduction (ꢀ)-lupanine to (þ)-sparteine.
NMR spectra: 1D and 2D correlation spectra: 1H, 13C, 1He1H
COSY, 1He13C HSQC and 1He13C HMBC were recorded on a Bruker
AVANCE II 400 (400.13 MHz for 1H and 100.63 MHz for 13C) spec-
trometer, with a 5 mm broadband probe head with actively shiel-
quantities of the optically pure 2-oxosparteine, we improved the
resolution of (ꢁ)-lupanine and determined the optical purity of its
enantiomers by optical rotation and using relatively simple 1H NMR
method with optically pure acids: (ꢀ)-2,3-dibenzoyl-
D-tartaric acid
ded z gradient coil (90ꢃ 1H pulse width 10.8 s, 13C pulse width
m

A.K. Przybył, M. Kubicki / Tetrahedron 67 (2011) 7787e7793
7791
Fig. 5. X-ray of the salt of (ꢀ)-lupanine and (þ)-2,3-dibenzoyl-D-tartaric acid. Elipsoids
are drawn at the 33% probability level, hydrogen bonds are spheres of arbitrary radii.
Hydrogen bonds are depicted as dashed lines.
Table 4
Hydrogen bond data (A,
ꢃ
ꢁ
)
D
H
A
DeH
H/A
D/A
DeH/A
N16
O24
O1W
O1W
O2W
O2W
H16
H24
H1W1
H1W2
H2W1
H2W2
O37a
O2W
O36b
O2c
0.91
0.82
1.00
0.94
0.84
0.99
1.86
1.76
1.80
1.86
1.99
1.78
2.765 (4)
2.551 (4)
2.784 (4)
2.769 (4)
2.803 (4)
2.704 (4)
177
161
165
162
165
154
O37d
O1W
Symmetry codes:
a
1þx,ꢀ1þy,z.
b
1þx,y,z.
c
1þy,1ꢀx,1/4þz.
d
y,1ꢀx,0.25þz.
Fig. 4. The chemical shift of H10
a
(eq) and H17
b
(eq) in the spectra of: (a) (ꢁ)-spar-
teine; (b) salt of (ꢁ)-sparteine and (ꢀ)-2,3-dibenzoyl-D-tartaric acid; (c) salt of
(ꢀ)-sparteine and (ꢀ)-2,3-dibenzoyl-D-tartaric acid; (d) (þ)-sparteine and (ꢀ)-2,3-
dibenzoyl-D-tartaric acid (1H NMR spectra, MeOD, TMS).
12 ms). All 2D spectra were acquired and processed using standard
Bruker software. Spectral width of 4000 Hz and 16,666.7 Hz in
1He13C HSQC, and 4000 Hz and 22,321.4 Hz in the case of 1He13C
HMBC were used for 1H and 13C, respectively. Relaxation delays of
1.0 s were used for all 2D experiments. All 2D spectra were collected
with 2K points in F2 and 256 increments (F1) with 4 (g-COSY) and
64 (g-HSQC) transients each.
The HPLC analysis was performed with a Waters HPLC system
with an analytical column Chiracel OD-H and the solvent system:
hexane/2-propanol (19:1); flow rate 0.5 mL/min; detection at UV
light, l¼220 nm.6 Optical rotation was measured using a Per-
kineElmer 242B polarimeter at 20 ꢃC in ethanol solution.
Fig. 6. The perspective view of the (ꢀ)-lupaninium cation. Elipsoids are shown at the
33% probability level.
4.2. Extraction and isolation of ( )-lupanine
(ꢁ)-Lupanine was obtained from the lupin seeds (L. albus cv.
BAC) according to a literature procedure,18 but modified to obtain
only quite pure lupanine. For this reason 2.5 kg of the grounded
seeds were defatted in a soxhlet with hexane (or with cheaper
petroleum ether) for 40 h. After drying, the 2.2 kg of the powdered
seeds were macerated for 3 h with 25% KOH(aq) (2 L) in order to
sufficiently destroy the tissues and release the alkaloids from their
ester forms or salts. A longer time of maceration can lead to the on
hydrolysis of the lactam group to give lupaninic acid.

7792
A.K. Przybył, M. Kubicki / Tetrahedron 67 (2011) 7787e7793
The pulp was mixed with 1 kg of Celite (diatomaceous earth) to
(196 mg, 84%); ½a D20
þ21.2 (c 1.6, EtOH) compared to mmc3 ꢀ20.7 (c
ꢂ
increase the surface of the mixture and to absorb the excess of
water. Such mass was poured into a linen sack and placed into
a soxhlet. The mixture of (ꢁ)-lupanine and (þ)-lupanine (1:1)18
were eluted for 40 h with petroleum ether to avoid the extraction
of the minor more polar alkaloids. This yielded 23.2 g of a yellow
solidifying oil. This extract was crystallized from diethyl ether to
obtain 12.46 g of yellow crystals of (ꢁ)-lupanine that was recrys-
tallized from hexane to get 10.3 g of white crystals of (ꢁ)-lupanine.
1.8, EtOH) measured for the laevorotatory material purchased from
Aldrich and lit.10
(þ)-2,3-dibenzoyl-
½
a 2D0
ꢂ
þ21.3 (c 1.7, EtOH); mp 128e129 ꢃC of
L-tartaric acid salt. Examination of the substance
under polarized light showed that the sample does not contain
single crystals. NMR in Tables 2 and 3, and Fig. 4. EIMS m/z 234
(15%), 137 (100%), 98 (73%), 136 (50%), 193 (35%), 110 (20%).
4.4. X-ray diffraction
4.3. Compounds
X-ray diffraction data were collected on a KUMA KM4CCD dif-
fractometer, using graphite-monochromated Mo
Ka radiation
4.3.1. (ꢁ)-Lupanine. White crystals, mp 98e99 ꢃC, 1H NMR and 13C
NMR (MeOH, DMSO) in Table 1, 13C NMR (CDCl3): 171.0, 63.9, 60.9,
55.4, 52.9, 46.7, 34.9, 33.7, 33.1, 32.4, 27.4, 26.8, 25.4, 24.5, 19.7; IR
ꢁ
(
l
¼0.71073 A) at room temp. The unit-cell parameters were de-
termined by the least-squares fit of the positions of the 11,388 most
intense reflections chosen from the whole experiment. The Lor-
entz-polarization and absorption corrections were applied.21 The
structures were solved with SIR9222 and refined with the full-
matrix least-squares procedure on F2 by SHELXL97.23 Scattering
factors incorporated in SHELXL97 were used. The function
(KBr):
n
C]O 1632 cmꢀ1, trans-band11 2810e2760 cmꢀ1 with
maxima at 2756 cmꢀ1 and weaker at 2820 cmꢀ1; m/z (rel int.): 248
(28%), 136 (100%), 149 (52%), 150 (36%), 98 (25%). The 13C NMR and
EIMS data were consistent with those in the literature.19,20
Sw(rFor2ꢀrFcr2)2 was minimized, with wꢀ1¼[
s
2(Fo)2þ(0.0387 P)2
4.3.2. (þ)-Lupanine. The petroleum ether mother liquor after re-
moving (ꢁ)-lupanine was concentrated to give 10.86 g of solidified
oil, which was dissolved in MeOH (50 mL). To the solution 10 mL of
10% HClO4 from MeOH was added (pH¼6) to obtain the perchlorate
of lupanine (11.6 g) that was recrystallized from MeOH to yield
10.8 g of lupanine perchlorate as a mixture enriched with the
dextrorotary enantiomer. Mp 251e252 ꢃC of the HClO4 salt; IR (KBr)
þ0.5248 P], where P¼[Max (Fo2, 0)þ2F2c/3]. Table 5 lists relevant
crystal data and refinement details. All non-hydrogen atoms were
refined anisotropically. The hydrogen atoms from water molecules
were found in difference Fourier maps and refined as a riding
model in positions found; all other hydrogen atoms were placed
geometrically, in idealized positions, and refined as rigid groups the
Uiso values for all hydrogen atoms were set at 1.2 times Ueq of the
appropriate carrier atom. Absolute configuration could not be de-
termined solely on the basis of X-ray data and was assigned on the
basis of known configuration of tartaric acid.
n
C]O 1620 cmꢀ1
, n
NþeH 3140 cmꢀ1. The free base of lupanine
½
a 2D0
ꢂ
þ21.1 (c 1.0, EtOH); NMRdTable 1 and Fig. 2.
4.3.3. Optical resolution of (ꢀ)-lupanine and (þ)-lupanine. Optical
resolution of the two enantiomers was performed with (þ)-2,3-
Table 5
dibenzoyl-
D
-tartaric acid. To the solution of (ꢁ)-lupanine (2.48 g,
Crystal data, data collection and structure refinement
10 mmol) in MeOH (10 mL) (þ)-2,3-dibenzoyl-
D-tartaric acid
Compound
1
(3.58 g, 10 mmol) in MeOH (10 mL) was added. The mixture was
heated, then cooled down to rt. After half an hour white crystals
started to precipitate.
Formula
C
15H25N2Oþ$C18H13O8ꢀ$2H2O
Formula weight
Crystal system
Space group
642.70
Tetragonal
P43
10.906 (2)
27.233 (4)
3239.1 (9)
4
1.32
1368
0.099
The white crystals were recrystallized from EtOH (10 mL) to
yield 2.37 g of (ꢀ)-lupanine salt, mp 144e145 ꢃC. The obtained
tartrate salt was transformed into the free base of (ꢀ)-lupanine by
dissolving the salt in water (20 mL) and basified with KOH to
pH¼14. The alkaloid was extracted with diethyl ether (5ꢄ5 mL, the
alkaloids in the eluent were monitored in Dragendorf reagent) to
ꢁ
a(A)
ꢁ
c(A)
3
ꢁ
V(A )
Z
Dx(g cmꢀ3
F(000)
)
(mmꢀ1
)
give (ꢀ)-lupanine (0.92 g, 37%) ½a D20
ꢂ
ꢀ81.8 (c¼1, EtOH); HPLC rt
m
Crystal size (mm)
Q
hkl Range
0.2ꢄ0.2ꢄ0.1
1.87e25.50
ꢀ13ꢅhꢅ13
ꢀ13ꢅkꢅ13
ꢀ32ꢅlꢅ32
26.139 min (Supplementary data). X-raydFigs. 5 and 6.
Range (ꢃ)
After removal of (ꢀ)-lupanine the mother liquor was concen-
trated and dissolved in water (20 mL), basified with KOH to pH¼14,
and (þ)-lupanine was extracted with diethyl ether (5ꢄ5 mL, the
alkaloids in the eluent were monitored in Dragendorf reagent) to
give 1.56 g of the crude oil that was dissolved in MeOH (10 mL) and
Reflections:
collected
59,234
3086 (0.080)
2430
417
0.051
unique (Rint
)
(ꢀ)-2,3-dibenzoyl-
L-tartaric acid (1.79 g, 5 mmol) was added. The
with I>2
Number of parameters
R(F) [I>2 (I)]
wR(F2) [I>2
(I)]
s(I)
mixture was heated, then cooled down to rt. After 1 h white crystals
started to precipitate. The crystals were recrystallized from EtOH
(10 mL) to yield white crystals 2.34 g, mp 143e144 ꢃC. Free base of
s
s
0.092
R(F) [all data]
0.072
0.098
1.131
0.14/ꢀ0.13
a 20
(þ)-lupanine (0.87 g, 35%) ½ ꢂD þ80.9 (c¼1, EtOH); HPLC rt
wR(F2) [all data]
Goodness of fit
28.120 min (Supplementary data); NMRdTable 1 and Fig. 2.
ꢁꢀ3
max/min Dr (e A
)
4.3.4. (þ)-Sparteine. (ꢀ)-Lupanine (248 mg, 1 mmol) was dis-
solved in dry THF (10 mL) and cooled to 0 ꢃC. LiAlH4 (309 mg,
8 mmol) was added in one portion. The reaction mixture was
stirred and refluxed in 100 ꢃC for 17 h and then was cooled to 0 ꢃC
Et2O (10 mL) was added. Then, saturated Na2SO4(aq) was added
dropwise until gas evolution ceased. The layers were separated in
a separating funnel. The aqueous layer was extracted with CH2Cl2
(5ꢄ20 mL). The organic extracts were dried over MgSO4 and con-
centrated under reduced pressure to give light oil of (þ)-sparteine
Crystallographic data (excluding structure factors) for the
structural analyses have been deposited with the Cambridge
Crystallographic Data Centre, CCDC Nos. 819,528 Copies of this
information may be obtained free of charge from: the Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK. Fax: 44 1223 336
033, e-mail: deposit@ccdc.cam.ac.uk, or www.ccdc.cam.ac.uk.

A.K. Przybył, M. Kubicki / Tetrahedron 67 (2011) 7787e7793
7793
Saffon, N.; Diehl, J.-P.; Martin-Vaca, B.; Bourissou, D. Biomacromolecules 2010,
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akoshi, I. Phytochemistry 1992, 31, 3251e3253.
4.4.1. The salt of (ꢀ)-lupanine and (þ)-2,3-dibenzoyl-
D-tartaric
acid. C15H25N2Oþ$C18H13O8ꢀ$2H2O, MW¼642.70, tetragonal, P43,
3
ꢁ
ꢁ
ꢁ
a¼10.906(2) (A), c¼27.233(4) (A), V¼3239.1(9) (A ), Z¼4,
Dx¼1.32 (g cmꢀ3), F(000)¼1368,
m
¼0.099 (mmꢀ1), crystal size
0.2ꢄ0.2ꢄ0.1 (mm),
Q
range 1.87e25.50 (ꢃ), hkl range: ꢀ13ꢅhꢅ13,
ꢀ13ꢅkꢅ13, ꢀ32ꢅlꢅ32; reflections: collected 59,234, unique 3086
8. Saito, K.; Takamatsu, S.; Sekine, T.; Ikegami, F.; Ohmiya, S.; Kubo, H.; Otomasu,
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s(I) 2430. Number of parameters 417, R(F)
[I>2s
(I)]¼0.051, wR(F2) [I>2
(I)]¼0.090, R(F) [all data]¼0.072,
s
9. (a) Stymiest, J. L.; Dutheuil, G.; Mahmood, A.; Aggarwal, V. K. Angew. Chem., Int.
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Hussain, N. Tetrahedron 2006, 62, 1833e1844; (e) Morita, Y.; Tokuyama, H.;
Fukuyama, T. Org. Lett. 2005, 7, 4337e4340; (f) Dearden, M. J.; McGrath, M. J.;
O’Brien, P. J. Org. Chem. 2004, 69, 5789e5792; (g) O’Brien, P.; Wiberg, K. B.;
Bailey, W. F.; Hermet, J.-P. R.; McGrath, M. J. J. Am. Chem. Soc. 2004, 126,
15480e15489; (h) Johanssen, M.; Schwartz, L. O.; Amedjkouh, M.; Kann, N. C.
Eur. J. Org. Chem. 2004, 1894e1896; (i) Johansson, M. J.; Schwartz, L.; Amedj-
kouh, M.; Kann, N. Tetrahedron: Asymmetry 2004, 15, 3531e3538; (j) Wilkinson,
J. A.; Rossington, S. B.; Ducki, S.; Leonard, J.; Hussain, N. Tetrahedron: Asymmetry
2004, 15, 3011e3013; (k) Hermet, J.-P. R.; Porter, D. W.; Dearden, M. J.; Harrison,
J. R.; Koplin, T.; O’Brien, P.; Parmene, J.; Tyurin, V.; Whitwood, A. C.; Gilday, J.;
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wR(F2) [all data]¼0.098, goodness of fit 1.131, max/min Dr 0.14
ꢁꢀ3
and ꢀ0.13 e A
.
Acknowledgements
The authors are grateful to Prof. M. Chrzanowska for analysis
using chiral HPLC as well as for the detailed information connected
with position 6 in references, and Prof. W. Wysocka and Dr. T.
Brukwicki (Faculty of Chemistry, A. Mickiewicz University, Grun-
ꢀ
waldzka 6, 60-780 Poznan; Poland) for helpful advices. This work
was supported by the Scientific Research Committee of Poland
(MiMiSW; Grant No NN312 187835).
ꢀ
Smith, B. T.; Wendt, J. A.; Aube, J. Org. Lett. 2002, 4, 2577e2579.
10. O’Brien, P. Chem. Commun. 2008, 655e667.
Supplementary data
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1989, 322, 399e403.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2011.07.080.
13. Greiner, E.; Folk, J. E.; Jacobson, A. E.; Rice, K. C. Bioorg. Med. Chem. 2004, 12,
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