Semisynthesis and myocardial activity of thaliporphine N-homologues

Article abstract of DOI:10.1021/np3007765

The N-homologues and optical isomers of thaliporphine (5a), a potent antiarrhythmic agent, were prepared starting from laurolitsine (1), an abundant aporphine present in Phoebe formosana. Treating N-propylnorglaucine with 90% H₂SO₄ yielded one additional product, an 11-sulfonyl-1,11-anhydroaporphine. Reaction of N-formylnorglaucine (3a) with 90% H₂SO₄, however, yielded the 9-sulfonyl-seco product as a major product. Treatment of 3a with 98% H₂SO₄ yielded pancordine (10), which, upon catalytic hydrogenation, yielded (±)-wilsonirine. ¹H NMR spectroscopic analysis was applied successfully to monitor the optical purity of the crystalline salt while undertaking optical resolution. Thaliporphine (5a) was demonstrated to possess better positive inotropic and less negative chronotropic effects than the left-hand optical isomer and showed the best activity on rat cardiac tissue among the N-homologues prepared.

Full text of DOI:10.1021/np3007765

Article
pubs.acs.org/jnp
Semisynthesis and Myocardial Activity of Thaliporphine
N‑Homologues
Chi-Ming Chiou,† Chin-Ting Lin,† Wei-Jang Huang,§ Yu-Mei Chang,‡ Yi-Jin Ho,‡ Ming-Jai Su,‡
and Shoei-Sheng Lee*,†
†School of Pharmacy, College of Medicine, National Taiwan University, Taipei 10051, Taiwan, Republic of China
‡Department of Pharmacology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan, Republic of China
§Graduate Institute of Pharmacognosy, Taipei Medical University, Taipei 11031, Taiwan, Republic of China
S
* Supporting Information
ABSTRACT: The N-homologues and optical isomers of
thaliporphine (5a), a potent antiarrhythmic agent, were
prepared starting from laurolitsine (1), an abundant aporphine
present in Phoebe formosana. Treating N-propylnorglaucine
with 90% H2SO4 yielded one additional product, an 11-
sulfonyl-1,11-anhydroaporphine. Reaction of N-formylnorglau-
cine (3a) with 90% H2SO4, however, yielded the 9-sulfonyl-
seco product as a major product. Treatment of 3a with 98%
H2SO4 yielded pancordine (10), which, upon catalytic
hydrogenation, yielded ( )-wilsonirine. 1H NMR spectro-
scopic analysis was applied successfully to monitor the optical purity of the crystalline salt while undertaking optical resolution.
Thaliporphine (5a) was demonstrated to possess better positive inotropic and less negative chronotropic effects than the left-
hand optical isomer and showed the best activity on rat cardiac tissue among the N-homologues prepared.
he aporphine alkaloid thaliporphine (5a) has been
demonstrated to possess a potent antiarrhythmic effect
(Lauraceae) (0.8% w/w in the stems),6,7 was isolated as a crude
precipitate. Since O,O-dimethylation of crude 1 with phenyl
trimethyl ammonium chloride under strong alkaline conditions
gave several products, and the N-acyl products of 1 were
crystallized easily, the first step for this approach was to react 1
with appropriate acid anhydrides. This step also served as the
purification step for laurolitsine (1), and the result suggested
the 25% purity of the crude precipitate. Reaction of 1 with ethyl
formate in DMF yielded N-formyllaurolitsine (2a), [M]+ 341,
N-CHO at δ 8.61 (s) and 8.44 (s). Subsequent O-methylation
of 2a with MeI−K2CO3 yielded N-formylnorglaucine (3a)
(87%), [M]+ 359. Under such conditions, 1 yielded the
corresponding quaternary ammonium salt. Reduction of the
amide 3a with lithium aluminum hydride afforded glaucine (4a)
(84%) with identical physical data (NMR, [α]D) to those
reported.5 Selective 1-O-demethylation by 90% H2SO4 yielded
the desired thaliporphine (5a) (63%),4 as well as three minor
products (Scheme 1). Of these, isoboldine (6a) and bracteoline
(7a) have been reported.4 The third compound (8a), [M]+ and
[M + 2]+ at m/z 389 and 391 with a peak intensity ratio of
100:4, is reported for the first time, and the corresponding N-
propyl homologue (8c) was obtained while using N-
propylnorglaucine (4c) as starting material (Scheme 1).
Compound 8c gave a molecular formula of C21H23O6NS as
T
with positive inotropic and slightly negative chronotropic
effects in the rat heart.1 This compound has been prepared via
total synthesis2 or by partial synthesis from selective 1-O-
demethylation of glaucine (4a), by reacting with dibenzyldise-
lenide3 or 90% H2SO4 for 13 days.4 Total synthesis of
aporphines usually starts from an appropriate catecholamine
and phenylacetic acid, requiring about 10 reaction steps to
achieve the products. Semisynthetic work requires the ready
availability of glaucine (4a). Our group reported a facile
preparation of this key intermediate by reacting boldine with
phenyl trimethyl ammonium salt under strong alkaline
conditions.5 Norglaucine (4d), a key intermediate for the
preparation of thaliporphine N-homologues, was also produced
by reduction of glaucine N-oxide with ferrous sulfate, which
gave secoglaucine, a B-ring-opening product.5 To shorten the
reaction time while preparing 5a from 4a by reacting with 90%
H2SO4 and to avoid the formation of secoglaucine while
preparing 4d, which will serve as a direct intermediate for
thaliporphine N-homologues (5a−c), several attempts have
been made. The following report describes progress made in
the semisynthesis of thaliporphine N-homologues and their
optical isomers, starting from laurolitsine (1), and the cardiac
effects of these compounds in a rat model.
Special Issue: Special Issue in Honor of Lester A. Mitscher
Received: November 6, 2012
RESULTS AND DISCUSSION
Laurolitsine (1), an abundant aporphine present in the
Formosan lauraceous plant Phoebe formosana (Hayata) Hayata
■
© XXXX American Chemical Society and
American Society of Pharmacognosy
A
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Scheme 1. Preparation of (+)-Thaliporphine Homologues (5a−5c) from Laurolitsine (1)
1
Table 1. H and 13C NMR Data and HMBC of Compounds 8c (CDCl3) and 10 (Methanol-d4)
a
a
8c
10
no.
δC multi.
δH multi. (J/Hz)
HMBC (C#)
δC multi.
δH multi. (J/Hz)
HMBC (C#)
1
135.8 C
147.72 C
112.6 CH
132.0 C
124.4 C
28.9 CH2
180.2 C
156.3 C
108.0 CH
135.8 C
119.5 C
121.9 CH
2
3
6.67 s
1, 2, 4, 3b
6.27 s
1, 2, 3b, 4
3a
3b
4
3.08 ddd (16.7, 11.3, 4.9)
2.69 br d (16.7)
5
6.96 d (4.3)
8.24 d (4.3)
3, 3b, 5
3, 3a, 3b
3a, 6a
5
49.4 CH2
3.21 br dd (11.5, 5.3)
2.53 dt (3.2, 11.9)
3.55 br d (14.7)
149.7 CH
4, 3a, 6a
6a
7
58.0 CH
33.1 CH2
3b
140.4 C
3.16 dd (14.7, 4.9)
2. 07 t (14.7)
6a,
135.4 CH
7.33 s
6.30 s
8.03 s
3b, 6a, 8, 11a
7, 9, 10, 11a
7a, 9, 10, 11b
3b, 6a, 7a, 8, 11a,
7a
8
127.3 C
115.6 CH
147.67 C
142.0 C
116.6 C
120.4 C
118.3 C
56.4 CH3
56.7 CH3
131.9 C
7.00 s
7, 9, 10, 11a
107.2 CH
150.6 C
9
10
11
156.8 C
104.6 CH
131.3 C
11a
11b
118.6 C
MeO-2
MeO-9
MeO-10
3.88 s
3.95 s
2
9
56.2 CH3
56.1 CH3
55.9 CH3
3.72 s
3.71 s
3.61 s
2
9
10
a
1H (600 MHz) and 13C NMR (150 MHz) data for the N-propyl group in 8c: δH 2.89 (1H, ddd, J = 12.9, 10.0, 6.1 Hz) and 2.48 (1H, ddd, J = 12.5,
10.0, 6.0 Hz) (N-CH2-C2H5), 1.60 (2H, m, N-CH2-CH2-CH3), 0.96 (3H, t, J = 7.3 Hz, N-C2H4-CH3); δC 56.1 (CH2), 19.1 (CH2), 12.0 (CH3).
deduced by HRESIMS. Its IR spectrum showed strong
absorptions at 1365 and 1175 cm−1, characteristic for a
sulfonate group,8 and its 1H NMR spectrum (Figure S1,
Supporting Information) revealed two aryl methoxy singlets (δ
3.88 and 3.95) and two aromatic singlets (δ 7.00, H-8; δ 6.67,
H-3) but lacked any signal for H-11 (ca. 8.00 ppm). In a
NOED experiment, respective irradiation at the methoxy
frequency enhanced the H-3 (δ 3.88) and H-8 singlets (δ
3.94), permitting the designation of the MeO-2 and MeO-9
signals. 2D-NMR spectroscopic analysis (HMBC and HET-
displayed an almost unchanged chemical shift for C-1,
downfield shifts for C-9 (δ 151.9 vs 147.7), C-11 (δ 124.9 vs
116.7), and C-7a (δ 134.5 vs 127.3), and an upfield shift for C-
10 (δ 134.5 vs 142.0) relative to the corresponding signals in
8c, suggesting a phenolic functionality at C-10 in 8c. Therefore,
the sulfonate group could be located at C-11, and this formed a
cyclic six-membered anhydride with the C-1 phenolic OH by
condensation with the structure, as shown in Scheme 1.
Use of N-acetyl- (2b) and N-propionyllaurolitsine (2c) as
key intermediates, obtained by reacting 1 with the correspond-
ing acid anhydride, and following procedures similar to those
for the preparation of 5a, yielded N-ethylnorthaliporphine (N-
ethylwilsonirine, 5b) and N-propylnorthaliporphine (N-propyl-
wilsonirine, 5c) (Scheme 1), respectively. The 1H NMR
spectrum of 5b, [M]+ at m/z 355, revealed the signals of an N-
ethyl group at δ 2.59 (2H, q) and 1.14 (3H, t), while that of 5c,
1
COR) enabled the complete assignments of the H and 13C
NMR data of 8c to be made, as shown in Table 1. Of these, C-1
and C-9−11 were assigned by respective coupling to H-3 (C-
1), H-8 [C-9, C-10, and C-11 (very weak)], and MeO-9 (C-9)
in the HMBC spectrum (Figure S3, Supporting Information).
The 13C NMR spectrum of its O-acetylated product (CDCl3)
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Scheme 2. Reaction of N-Acylaporphines (3a−3c) with 50, 90, or 98% H2SO4
Scheme 3. Preparation of (−)-Thaliporphine [(−)-5a] and (−)-N-Propylwilsonirine [(−)-5c] from Pancoridine (10)
[M]+ at m/z 369, revealed the signals of an N-propyl group at δ
2.60 (2H, m), 1.57 (2H, m), and 1.14 (3H).
confirmed by analysis of the HMBC spectrum (Table 1;
Figure S6, Supporting Information), which showed key
correlations of H-3 (δ 6.27) to C-1 (δ 180.2), C-4 (δ 121.9),
and C-3b (δ 119.5) and of H-5 (δ 8.24) and H-7 (δ 7.33) to C-
6a (δ 140.4) (Table 1). This 2D-NMR analysis also led to the
Since 90% sulfuric acid could cleave selectively the sterically
hindered methyl group at MeO-1 in glaucine (4a), whether this
reagent possessed a similar propensity to the corresponding N-
acyl derivatives (3a−3c) was investigated. Reaction of N-
formylnorglaucine (3a) with 90% H2SO4, however, yielded a
secoaporphine, N-formyl-9-sulfonylseconorglaucine (9a)
(38%), and a trace amount of an oxidized product (10)
instead of the expected N-formylwilsonirine (N-formylnortha-
liporphine) (Scheme 2). Compound 9a gave a molecular
1
complete H and 13C NMR assignments shown in Table 1.
Pancoridine (10) has been prepared from 6′-aminopapaverine
by a two-step reaction, involving diazotization and skeletal
rearrangement under warm 65% sulfuric acid,10 and also has
been isolated from plants such as Popowia pisocarpa (Bl.) Endl.
(Annonaceae).11 Since compound 10 is an oxidative product, it
could be obtained in a better yield using a stronger oxidant such
as 98% H2SO4. This was found to be the case, and up to a
44.4% yield of 10 was obtained by reacting 3a with this reagent,
accompanied by three minor products, 9a, 12a, and 13a
1
formula of C21H23O8NS as deduced by HRFABMS. Its H
NMR spectrum exhibited four aromatic singlets, two
methylenes as multiplets, four methoxy singlets, and one
singlet for a formyl proton (δ 8.05). This structure was
confirmed by two NOED experiments. Irradiation at the H-2
frequency (δ 7.14) enhanced the signals of MeO-3 (δ 3.99,
10.2%), H2-12 (δ 3.30, 2.7%), and H2-11 (δ 3.58, 1.2%).
Irradiation of the H-10 singlet (δ 8.53) enhanced the latter two
signals only, suggesting C-9 to be sulfonated. Compound 9a
was produced by two reaction steps. The first one was similar
to the reaction of N-acylaporphines under refluxing HCl−
MeOH conditions,7,9 yielding the corresponding secoapor-
phines, and followed by sulfonation at the less hindered C-9.
This was verified since reaction of 3a with 50% H2SO4 yielded
1
(Scheme 2). The H NMR spectrum of 12a showed one
additional aryl proton signal but lacked the upfield-shifted
MeO-1 singlet as compared to that of 3a. Moreover, all the
chemical shifts of the parent four aryl protons and three
methoxy groups were downfield shifted, especially for H-11 (δ
9.21), accountable for a phenanthrene skeleton.7 On the basis
of these data, a selective O-demethylation at MeO-1 and
didehydrogenation at C-6a and C-7 occurred while treating 3c
with 98% H2SO4. The structure proposed for 12a, N-formyl-
6a,7-didehydronorthaliporphine, was supported by NOED
experiments upon irradiation at H-11 (δ 9.21), enhancing
MeO-10 (δ 4.06, 9.1%), and irradiation at NCHO (δ 8.86),
enhancing H2-5 (δ 4.11, 1.5%) and H-7 (δ 7.19, 14.1%).
Compound 13a exhibited a molecular formula of C20H21O8NS,
as deduced from the HREIMS, representing a CH2 unit less
1
N-formylseconorglaucine (11a, 51%), for which the H NMR
spectrum showed a characteristic AB system for the H-9 and H-
10 in the phenanthrene skeleton (δ 7.77 and 7.55, JAB = 9.1 Hz)
similar to that in N-formylsecolaurolitsine.7 Compound 10 gave
a molecular formula of C19H15NO4 as deduced from the
HREIMS and was identified as pancoridine by comparison of
its 1H NMR data with literature values,10,11 showing four
singlets and an AX system (δ 8.24 and 6.96, JAX = 4.3 Hz) for
aryl protons and three methoxy singlets (δ 3.72, 3.71, and 3.61)
(Figure S4, Supporting Information). This structure was
1
than 3a. Its H NMR spectrum was very similar to that of 3a
except for the absence of the MeO-4 signal (δ 3.84, 3a).
Therefore, 13a was elucidated as 4-O-demethylated 9a, i.e., N-
formyl-9-sulfonylsecowilsonirine.
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It has been reported that racemic wilsonirine (north-
aliporphine) [( )-14] can be obtained by reduction of
pancoridine (10) with Zn−Hg/HCl in 52% yield.10 It was
found that this product can be produced in a better yield (72%)
by catalytic hydrogenation under the following conditions: 5
bar H2, Pt−C, AcOH, 60 °C, 2 days (Scheme 3). Optical
resolution of the racemate by (−)-di-O-toluoyltartaric acid and
(+)-di-O-toluoyltartaric acid was accomplished to yield
(−)-6aR- [(−)-14] and (+)-6aS-wilsonirine [(+)-14], respec-
tively. Conventionally, the optical purity of the resolved
compound was judged by the specific optical rotation of the
crystalline acid−amine salt, obtained by fractional recrystalliza-
tion. In this study, a convenient method for this purpose was
The effects on the contractility and heart rate of rat cardiac
tissues were evaluated for the thaliporphine homologues
prepared and the corresponding optical isomers. The results
shown in Table 2 indicate that all of the prepared thaliporphine
homologues including both optical isomers (5a−5c, 14)
showed a negative chronotropic effect on the spontaneously
beating rat right atrium at the concentration range of 10−30
μM. In right atria and electrically driven left atria and right
ventricular strips, only thaliporphine [(+)-5a] showed a
significant positive inotropic effect at a concentration between
3 and 30 μM. Since the positive inotropic effect of (+)-5a in the
electrically driven left atrium and right ventricle was affected
neither by prazosin (1 μM) nor by atenolol (3 μM), but
partially by verapamil (1 μM) (unpublished observation), this
effect caused by (+)-5a might be mediated by its partial calcium
channel agonistic activity.1 In contrast with (+)-5a, (−)-5a and
(+)-N-propylwilsonirine [(+)-5c] showed negative inotropic
effects in electrically driven right ventricular strips, which were
similar to those of isoquinolines and bisbenzylisoquino-
lines.14,15 The latter two types of compounds have been
reported to exert a negative inotropic effect by inhibition of an
L-type calcium inward current14 or Bay K8644-stimulated 45Ca
uptake, probably via interaction with the diltiazem-binding
sites.15 Other compounds [(+)-14, (−)-14, (+)-5b, and
(−)-5c] showed a significant negative chronotropic effect
with an insignificant inotropic effect on right ventricular strips.
In conclusion, the common observation of the negative
chronotropic effects of most compounds shown in Table 2
may be mediated by their prolongation of action potential
duration via inhibition of the potassium outward current. The
differences in inotropic effects among these compounds may be
due to their difference in activation or inhibition of L-type
calcium currents. These speculations, however, need to be
clarified by electrophysiological studies.
1
found by examining the H NMR spectrum of the crystalline
salts (Figure 1; Figure S7, Supporting Information). While
1
Figure 1. H NMR spectra of the (−)-di-O-4-toluoyl-L-tartrates of
( )-14 (top) and (−)-14 in the aromatic region (methanol-d4, 400
MHz).
1
adding the resolving agent, the H NMR spectrum of the
1
racemate 14 was found to split into two sets. Tracing the H
NMR spectra of the crystalline amine acid salts revealed that
only one spectrum was observed for the product with constant
specific optical rotation. This method is facile and is useful for
tracing the optical purity of the resolved compounds.
The left-handed optical isomers of thaliporphine and N-
propylwilsonirine [(−)-5a and (−)-5c] were prepared from
(−)-wilsonirine [(−)-14] by reductive N-methylation and N-
alkylation, respectively (Scheme 3).
This study provides a practical method to prepare glaucine
(4) and establishes a method to prepare thaliporphine N-
homologues, both starting from laurolitsine (1). A convenient
method for examining the optical purity of the optically
1
resolved isomers by H NMR analysis is also disclosed. A
preliminary investigation on the structure−activity relationships
of the optical isomers of thaliporphine homologues revealed
a
Table 2. Effects of Thaliporphine N-Homologues on Contractile Tension and Heart Rate of Rat Cardiac Tissues
assay
μM
(+)-14
(−)-14
(+)-5a
(−)-5a
(+)-5b
(+)-5c
(−)-5c
c
% heart rate (RA)
3
10
30
91
78
6
8
100
0
4
6
92
8
5
7
92
85
5
7
97
3
3
4
91
80
61
6
7
8
88
79
68
4
6
7
c
c
c
c
c
c
c
c
96
79
86
82
97
84
c
c
c
c
61 15
69 10
% tension
1. RA
d
c
3
10
30
3
99
99
3
3
101
103
1
6
104
4
106 17
121 32
129 41
93
3
103
103
103
99
6
6
8
1
4
7
1
3
2
121
4
c
b
b
140 12
180 12
127 17
162 24
131 15
141 24
d
c
117 13
105 12
d
2. LA
3. RV
94
93
6
8
9
4
9
7
103
104
105
108
8
9
5
7
110
7
106
4
105
122
6
9
101
105
99
1
5
1
0
2
9
b
d
d
b
10
30
3
180 12
103 10
100 13
90
c
c
89
243 24
131 10
74
c
102
96
125
6
93
4
100
108
0
8
95
100
100
96
c
c
b
d
10
30
111 10
120 10
154 17
163 23
80 10
72 12
85
b
90
111 16
75
a
Contractions of left atrial (LA) and right ventricular (RV) strips were elicited by electrical stimulation driven at 2 Hz. Spontaneous contraction of
the right atrium (RA) and heart rate were measured. Data are expressed as % of control values before chemical treatment. Mean values (control
group: heart rate 242 7 beats/min, twitch tension RA 121 10, LA 140 11, and RV 225 17 mg) were obtained from four to five experiments.
b
c
d
p < 0.05. p < 0.01. p < 0.001, compared with the respective control by the Student’s t-test.
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EIMS (70 eV) 383 (77, [M]+), 324 (44), 311 (100), 297 (12), 265
(20).
N-Propionylnorglaucine (3c): H NMR (MeOH-d4, 400 MHz) δ
8.13 (1H, s, H-11), 6.76 (1H, s, H-8), 6.60 (1H, s, H-3), 3.89 (3H, s,
MeO-9), 3.87 (6H, s, MeO-2 and 10), 3.59 (3H, s, MeO-1), 2.45 (2H,
q, J = 7.2 Hz, NCOCH2CH3), 1.16 (3H, t, J = 7.2 Hz, NCOCH2CH3);
EIMS (70 eV) m/z 397 (79, [M]+), 324 (58), 311 (100), 265 (16), 57
(20).
thaliporphine (5a) to be the best cardiotonic agent, with a
potent positive inotropic but a slightly negative chronotropic
effect on rat cardiac tissues. These findings could be of value for
the selection of lead compounds of the type studied herein for
the potential development of cardiovascular drugs.
1
EXPERIMENTAL SECTION
■
Preparation of (+)-Glaucine (4a), (+)-N-Ethyl- (4b), and (+)-N-
Propylnorglaucine (4c). To a suspension of LiAlH4 (1.80 g, 47.4
mmol) in dry THF (20 mL) was added a solution of 3a (8.0 g, 21.7
mmol) in dry THF (10 mL) dropwise at room temperature. The
mixture was refluxed for 2 h under nitrogen. After quenching the
excess LiAlH4 with hydrated Na2SO4, the suspension was filtered with
the aid of a Celite cake and the precipitate was washed with CHCl3
(100 mL × 2). The filtrate and CHCl3 washings were dried (Na2SO4)
and evaporated to give a brown residue, which yielded 4a (7.30 g,
84.0%) after recrystallization from diethyl ether. In a similar manner,
reduction of 3b (2.67 g, 6.97 mmol) by LiAlH4 (380 mg, 10 mmol) in
dry THF (30 mL in total) gave 4b (2.22 g, 86.0% yield), while
reduction of 3c (4.01 g, 10.1 mmol) by LiAlH4 (380 mg, 10 mmol) in
dry THF (30 mL in total) gave 4c (3.36 g, 86.0%).
General Experimental Procedures. The physical data of the
prepared compounds were obtained using the following instruments:
Fisher-Johns melting point apparatus (uncorrected); JASCO DIP-370
polarimeter; Perkin-Elmer 1760-X IR FT spectrometer (KBr); Hitachi
150-20 double-beam spectrophotometer (MeOH); Bruker AMX400
and AVIII600 NMR spectrometers using solvent peak as reference
standard (methanol-d4, δH 3.30 and δC 49.0; CDCl3, δH 7.24 and δC
77.0) and standard pulse programs for 1D and 2D NMR measure-
ments; JEOL JMX-HX110 (HREIMS), Finnigan TSQ-700 (EIMS),
JEOL JMX-HX D100 (FABMS), and Bruker micrOTOF orthogonal
ESI-TOF (HRESIMS) mass spectrometer.
Preparation of N-Formyl- (2a), N-Acetyl- (2b), and N-
Propionyllaurolitsine (2c). Crude laurolitsine (1)6 (50 g), DMF
(112 mL), and ethyl formate (117 mL) were placed in a screw-tight
sealed tube (500 mL). After degassing under a vacuum, the mixture
was stirred at 90 °C for 60 h and was evaporated to give a residue. The
residue was recrystallized from MeOH to afford 2a (15.6 g). In a
similar manner, reaction of crude 1 (10.0 g) with Ac2O (2 mL) in
DMF (25 mL) afforded 2b (3.60 g), while reaction of crude 1 (30.0 g)
with propionic anhydride (6.0 mL) in DMF (75 mL) yielded 2c (8.02
g).
(+)-Glaucine (4a): mp 112−114 °C (Et2O); [α]24 +120 (c 0.30,
D
1
MeOH); H NMR (CDCl3) δ 8.06 (1H, s, H-11), 6.75 (1H, s, H-8),
6.56 (1H, s, H-3), 3.91 (3H, s, MeO-9), 3.88 (3H, s, MeO-10), 3.86
(3H, s, MeO-2), 3.64 (3H, s, MeO-1), 2.53 (3H, s, NCH3).
(+)-N-Ethylnorglaucine (4b): mp 94−96 °C (Et2O); [α]24D +97 (c
1
0.31, MeOH); H NMR (CDCl3, 400 MHz) δ 8.05 (1H, s, H-11),
6.75 (1H, s, H-8), 6.56 (1H, s, H-3), 4.03 (3H, s, MeO-9), 3.90 (3H, s,
MeO-2), 3.88 (3H, s, MeO-10), 3.59 (3H, s, MeO-1), 2.45 (2H, q, J =
7.2 Hz, NCH2CH3), 1.16 (3H, t, J = 7.2 Hz, NCH2CH3); EIMS (70
eV) m/z 369 (100, [M]+), 354 (78), 338 (37), 312 (14), 281 (20).
N-Formyllaurolitsine (2a): 1H NMR (MeOH-d4, 400 MHz) δ
8.36/8.22 (1:3) (1H, s, NCHO), 8.06/8.05 (3:1) (1H, s, H-11), 6.76/
6.72 (1:3) (1H, s, H-8), 6.62/6/61 (1H, s, H-3), 4.72 (dd, J = 13.8, 4.2
Hz)/4.50 (dd, J = 14.4, 4.3 Hz) (3:1) (1H, H-6a),3.89 (3H, s, MeO-
10), 3.59 (3H, s, MeO-1); EIMS (70 eV) m/z 341 (90, [M]+), 296
(40), 283 (100), 240 (30), 58 (70).
(+)-N-Propylnorglaucine (4c): mp 95−97 °C (Et2O); [α]24 +107
D
1
(c 0.33, MeOH); H NMR (CDCl3, 400 MHz) δ 8.03 (1H, s, H-11),
6.75 (1H, s, H-8), 6.54 (1H, s, H-3), 3.86 (3H, s, MeO-9), 3.83 (6H, s,
MeO-2 and 10), 3.60 (3H, s, MeO-1), 2.88 (1H) and 2.43 (1H) (m,
NCH2C2H5), 1.50 (2H, m, NCH2CH2CH3), 0.93 (3H, t, J = 7.2 Hz,
NC2H4CH3); EIMS (70 eV) m/z 383 (100, [M]+), 368 (82), 354
(45), 352 (36), 281 (19).
Preparation of (+)-Norglaucine (4d). N-Formylnorglaucine (3a,
2.00 g, 5.42 mmol), potassium hydroxide (2.30 g, 41.5 mmol), and
ethanol (50 mL) were placed in a 100 mL reaction bottle. The mixture
was heated under reflux for 3 h. On cooling, the reaction mixture was
concentrated under reduced pressure to give a residue that was
partitioned between water (100 mL) and chloroform (300 mL × 3).
The combined organic phase was dried (Na2SO4) and concentrated
under reduced pressure to give a solid residue, which was purified by
1
N-Acetyllaurolitsine (2b): H NMR (MeOH-d4, 400 MHz) δ 8.06
(1H, s, H-11), 6.77/6.70 (1:2) (1H, s, H-8), 6.61 (1H, s, H-3), 3.89
(3H, s, MeO-10), 3.58 (3H, s, MeO-1), 2.21/2.19 (2:1) (3H, s,
NCOCH3); EIMS (70 eV) m/z 355 (88, [M]+), 296 (74), 283 (100),
269 (42), 240 (18).
1
N-Propionyllaurolitsine (2c): H NMR (MeOH-d4, 400 MHz) δ
8.06 (1H, s, H-11), 6.71 (1H, s, H-8), 6.61 (1H, s, H-3), 3.88 (3H, s,
MeO-10), 3.59 (3H, s, MeO-1), 2.52 (2H, q, NCOCH2CH3), 1.16
(3H, t, NCOCH2CH3); EIMS (70 eV) m/z 369 (100, [M]+), 296
(87), 283 (85), 269 (44), 240 (16), 57 (34).
Preparation of N-Formyl- (3a), N-Acetyl- (3b), and N-
Propionylnorglaucine (3c). N-Formylnorlaurolitsine (2a) (10.3 g,
29.4 mmol), K2CO3 (12.3 g), MeI (13 mL, 209 mmol), and MeOH
(100 mL) were placed in a screw-tight sealed flask. After degassing
under a vacuum, the mixture was stirred under reflux (70 °C) for 24 h.
The reaction mixture was evaporated in vacuo, and the residue was
partitioned between CHCl3 (300 mL) and H2O (pH 8.0, 150 mL ×
2). The CHCl3 layer was dried (Na2SO4) and evaporated to a residue,
which was recrystallized from MeOH to afford 3a (9.5 g, 87.0%). In a
similar manner, reaction of 2b (3.0 g, 7.83 mmol) with MeI (3.5 mL,
56.2 mmol)−K2CO3 (3.3 g) in MeOH (30 mL) gave 3b (2.76 g,
89.0%), while reaction of 2c (2.50 g, 6.78 mmol) with MeI (3.5 mL,
56.2 mmol)−K2CO3 (3.3 g) in MeOH (30 mL) yielded 3c (2.21 g,
82.4%).
silica gel column chromatography, eluted with 0.2% MeOH−CHCl3,
1
to give 4d (1.75 g, 95%): [α]24 +77.1 (c 0.35, CHCl3); H NMR
D
(CDCl3, 400 MHz) δ 8.09 (1H, s, H-11), 6.73 (1H, s, H-8), 6.58 (1H,
s, H-3), 3.90 (3H, s, MeO-9), 3.88 (3H, s, MeO-10), 3.86 (3H, s,
MeO-2), 3.65 (3H, s, MeO-1), 3.81 (1H, dd, J = 13.9, 4.2 Hz, H-6a);
(+)-HRESIMS m/z 342.1682 [M + H]+, calcd for C20H24NO4,
342.1705.
Reaction of Glaucine (4a) with 90% Sulfuric Acid. Compound
4a (3.0 g, 8.45 mmol) and 90% H2SO4(aq) (6.0 mL) were placed in a
screw-tight sealed flask (100 mL).4 The mixture after degassing under
a vacuum was stirred for 13 days at room temperature. The reaction
mixture was added dropwise into a beaker containing ice−water (100
mL), and the resultant suspension was adjusted to pH 8.0 with
ammonia−water (25%) at 0 °C and partitioned against CHCl3 (50 mL
× 3). The combined CHCl3 layers were dried (Na2SO4) and
evaporated to give a brown residue, which was chromatographed
over a silica gel column (160 g, 230−400 mesh), eluted with 1−3%
MeOH in CHCl3, to give 5a (1.82 g, 63.0% yield), 6a (148 mg, 5%),
7a (167 mg, 6%), and 8a (5 mg).
1
N-Formylnorglaucine (3a): H NMR (CDCl3, 400 MHz) δ 8.37/
8.23 (1.0:2.2) (1H, s, N-CHO), 8.12/8.11 (1H, s, H-11), 6.78/6.74
(2.2:1.0) (1H, s, H-8), 6.63/6.60 (1.0:2.2) (1H, s, H-3), 4.89 (dd, J =
13.9, 4.2 Hz) and 4.46 (dd, J = 14.4, 4.3 Hz) (2.2:1.0) (1H, H-6a),
3.90 (9H, s, MeO-2, 9 and 10), 3.65 (3H, s, MeO-1); EIMS (70 eV)
m/z 369 (5, [M]+), 355 (100), 340 (40).
1
N-Acetyllnorglaucine (3b): H NMR (CDCl3, 400 MHz) δ 8.15/
11-Sulfonyl-1,11-anhydrobracteoline (8a): mp 174−178 °C
(MeOH); IR νmax 3450 (s), 2750 (s), 1725 (m), 1600 (m), 1580
(s), 1500 (s), 1365 (s), 1280 (s), 1240 (s), 1165 (s), 1122 (s) cm−1;
1H NMR (CDCl3, 400 MHz) δ 6.99 (1H, s, H-8), 6.67 (1H, s, H-3),
8.12 (1.0:1.6) (1H, s, H-11), 6.76/6.74 (1H, s, H-8), 6.64/6.60
(1.0:1.6) (1H, s, H-3), 3.89 (3H, s, MeO-9), 3.87 (6H, s, MeO-2 and
10), 3.64 (3H, s, MeO-1), 2.20/2.16 (1.6:1.0) (3H, s, NCOCH3);
E
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3.94 (3H, s, MeO-9), 3.88 (3H, s, MeO-2), 2.52 (3H, s, NCH3); EIMS
(20 eV) m/z 391 (4, [M + 2]+), 389 (46, [M]+), 388 (100), 346 (22),
267 (16).
mmol) and 3c (100 mg, 0.252 mmol), respectively, by reacting with
90% H2SO4(aq) (each 2.0 mL).
N-Formyl-9-sulfonylseconorglaucine (9a): mp 205−208 °C
(MeOH); IR νmax 3410, 3210, 1665, 1530, 1470, 1400, 1250, 1125,
1050 cm−1; 1H NMR (MeOH-d4, 400 MHz) δ 9.26 (1H, s, H-5), 8.53
(1H, s, H-10), 8.45 (1H, s, H-8), 8.05 (1H, s, NCHO), 7.14 (1H, s, H-
2), 4.04 (3H, s, MeO-7), 3.99 (6H, s, MeO-6 and 3), 3.84 (3H, s,
MeO-4), 3.58 (2H, m, H-11), 3.30 (2H, m, H-12); FABMS m/z 472
(33, [M + Na]+), 451 (38, [M + 2]+), 450 (100, [M + H]+), 449 (95,
[M]+).
N-Acetyl-9-sulfonylseconorglaucine (9b): mp 216−220 °C
(MeOH); IR νmax 3450, 3200, 1630, 1525, 1470, 1400, 1270, 1120,
1050 cm−1; 1H NMR (MeOH-d4, 400 MHz) δ 9.30 (1H, s, H-5), 8.54
(1H, s, H-10), 8.42 (1H, s, H-8), 7.31 (1H, s, H-2), 4.04 (3H, s, MeO-
7), 3.99 (6H, s, MeO-6 and 3), 3.86 (3H, s, MeO-4), 3.51 (2H, m, H-
11), 3.30 (2H, m, H-12), 1.91 (3H, s, NCOCH3); FABMS m/z 486
(38, [M + Na]+), 465 (38, [M + 2]+), 464 (100, [M + H]+), 463 (95,
[M]+).
N-Propioyl-9-sulfonylseconorglaucine (9c): mp 236−240 °C
(MeOH); IR νmax 3450, 3200, 1610, 1520, 1470, 1270, 1250, 1215,
1170, 1120, 1040 cm−1; 1H NMR (MeOH-d4, 400 MHz) δ 9.29 (1H,
s, H-5), 8.53 (1H, s, H-10), 8.41 (1H, s, H-8), 7.30 (1H, s, H-2), 4.03
(3H, s, MeO-7), 4.00 (6H, s, MeO-6 and 3), 3.85 (3H, s, MeO-4),
3.50 (2H, m, H-11), 3.29 (2H, m, H-12), 2.11 (2H, m,
NCOCH2CH3), 1.07 (3H, t, NCOCH2CH3); FABMS m/z 500 (44,
[M + Na]+), 479 (38, [M + 2]+), 478 (100, [M + H]+), 477 (95,
[M]+).
Reaction of N-Formylnorglaucine with 50% H2SO4. Com-
pound 3a (101 mg, 0.27 mmol) and 50% H2SO4 (2.0 mL) were placed
in a screw-tight sealed flask (25 mL). The mixture after degassing by a
vacuum was stirred at 80 °C for 3.5 h. On cooling, the reaction mixture
was added dropwise into a beaker containing ice−water (30 mL), and
the resultant suspension was adjusted to pH 7.0 with ammonia−water
at 0 °C and passed through an Amberlite XAD-2 column (20 g),
eluted in sequence with H2O (100 mL) and MeOH (100 mL), to give
11a (52.0 mg, 51%) from the MeOH elution.
Preparation of (+)-N-Ethyl- (5b) and (+)-N-Propylwilsonirine
(5c). In a similar manner for the preparation of 5a from 4a, reaction of
4b (1.50 g, 4.07 mmol) with 90% H2SO4(aq) (3.0 mL) yielded 5b
(247 mg, 17.0%), 6b (152 mg, 11%), and 7b (30 mg, 2.2%), while
reaction of 4c (1.20 g, 3.13 mmol) with 90% H2SO4(aq) (3.0 mL)
gave (+)-5c (346 mg, 30.0%), 6c (122 mg, 11.0%), and 8c (10 mg).
(+)-N-Ethylwilsonirine (5b): mp 94−96 °C (MeOH); [α]24D +58.5
1
(c 0.32, MeOH); H NMR (CDCl3, 400 MHz) δ 8.02 (1H, s, H-11),
6.76 (1H, s, H-8), 6.52 (1H, s, H-3), 3.90 (6H, s, MeO-2 and 9), 3.88
(3H, s, MeO-10), 2.59 (2H, q, J = 7.2 Hz, NCH2CH3), 1.14 (3H, t, J =
7.2 Hz, NCH2CH3); EIMS (20 eV) m/z 355 (100, [M]+), 354 (78),
340 (42), 298 (30), 267 (25).
(+)-N-Propylwilsonirine (5c): mp 66−70 °C (MeOH); [α]24
D
1
+60.2 (c 0.33, MeOH); H NMR (CDCl3, 400 MHz) δ 8.00 (1H, s,
H-11), 6.75 (1H, s, H-8), 6.51 (1H, s, H-3), 3.90 (6H, s, MeO-2 and
9), 3.89 (3H, s, MeO-10), 2.60 (1H, m) and 2.43 (1H, m)
(NCH2C2H5), 1.57 (2H, m, NCH2CH2CH3), 0.95 (3H, t, J = 7.2
Hz, NC2H4CH3); EIMS (20 eV) m/z 369 (100, [M]+), 354 (22), 340
(36), 298 (20), 267 (18).
1
N-Ethylnorbracteoline (6b): H NMR (CDCl3, 400 MHz) δ 8.00
(1H, s, H-11), 6.74 (1H, s, H-8), 6.52 (1H, s, H-3), 3.90 (3H, s, MeO-
9), 3.87 (3H, s, MeO-2), 2.59 (2H, q, J = 7.2 Hz, NCH2CH3), 1.15
(3H, t, J = 7.2 Hz, NCH2CH3); EIMS (20 eV) m/z 341 (100, [M]+),
326 (18), 284 (15), 253 (4).
1
N-Propylnorbracteoline (6c): H NMR (CDCl3, 400 MHz) δ 8.00
(1H, s, H-11), 6.75 (1H, s, H-8), 6.51 (1H, s, H-3), 3.90 (3H, s, MeO-
10), 3.88 (3H, s, MeO-2), 2.83 (1H, m) and 2.47 (1H, m)
(NCH2C2H5), 1.56 (2H, m, NCH2CH2CH3), 0.95 (3H, t, J = 7.2
Hz, NC2H4CH3); EIMS (20 eV) m/z 355 (100, [M]+), 340 (24), 326
(26), 284 (22), 265 (8), 253 (8).
N-Ethylnorisoboldine (7b): 1H NMR (MeOH-d4, 400 MHz) δ 7.99
(1H, s, H-11), 6.79 (1H, s, H-8), 6.52 (1H, s, H-3), 3.90 (3H, s, MeO-
10), 3.88 (3H, s, MeO-2), 2.59 (2H, q, J = 7.2 Hz, NCH2CH3), 1.12
(3H, t, J = 7.2 Hz, NCH2CH3); EIMS (20 eV) m/z 341 (100, [M]+),
326 (25), 284 (26), 253 (16).
N-Formylseconorglaucine (11a): mp 134−135 °C (MeOH); Rf
0.51 (10% MeOH−CHCl3); UV λmax (log ε) 318 (4.01), 305 (3.96),
283 (4.38), 263 (4.87) nm; IR νmax 3350, 2950, 1675, 1510, 1470,
11-Sulfonyl-1,11-anhydrobracteoline (8a): mp 174−178 °C
1
1410, 1260, 1240, 1115, 1095 cm−1; H NMR (CDCl3, 400 MHz) δ
(MeOH); IR νmax 3450 (br s), 2960 (s), 2750 (s), 1580 (s), 1500
9.23 (1H, s, H-5), 8.17 (1H, s, NCHO), 7.77 (1H, d, J = 9.1 Hz, H-
10), 7.55 (1H, d, J = 9.1 Hz, H-9), 7.18 (1H, s, H-8), 7.14 (1H, s, H-
2), 4.05 (3H, s, MeO-7), 4.02 (3H, s, MeO-6), 4.01 (3H, s, MeO-3),
3.84 (3H, s, MeO-4), 3.69 (2H, m, H-11), 3.31 (2H, m, H-12); EIMS
(20 eV) m/z 369 (100, [M]+), 324 (20), 311 (42), 297 (30);
HREIMS m/z 369.1573 [M]+, calcd for C21H23O5N, 369.1576.
Reaction of N-Formylnorglaucine with 98% H2SO4: Preparation
of Pancoridine (10). Compound 3a (4.04 g, 11.5 mmol) and 98%
H2SO4 (8.1 mL) were placed in a screw-tight sealed flask (25 mL).
The mixture after degassing by a vacuum was stirred for 8 days at
room temperature. The reaction mixture was added dropwise into a
beaker containing ice−water (100 mL), and the resultant suspension
was adjusted to pH 7.0 with ammonia−water (25%) at 0 °C and
extracted by CHCl3 (200 mL × 3). The combined CHCl3 layers were
dried (Na2SO4) and evaporated to give a brown residue (2.56 g),
which, on recrystallization from CHCl3, yielded 10 (1.54 g, 44.4%):
mp 211−213 °C; EIMS (70 eV) mlz 321 (100, [M]+), 290 (100);
HREIMS [M]+ m/z 321.0992, calcd for C19H15O4N, 321.1001. The
mother liquor was chromatographed over a silica gel column (30 g,
70−230 mesh), eluted with 0−3% MeOH−CHCl3, to give 12 (25 mg,
0.62%). The aqueous layer, after removal of the residual CHCl3 left
during partition, by condensation under reduced pressure, was passed
through a Sephadex LH-20 column, eluted with MeOH−0.1%
HOAcaq. (1:1), to give 9a (10 mg, 0.19%) and 13a (22.3 mg, 0.45%).
N-Formyl-6a,7-didehydronorthaliporphine (12a): 1H NMR
(MeOH-d4, 400 MHz) δ 9.21 (1H, s, H-11), 8.86 (1H, s, NCHO),
8.41 (1H, s, H-8), 7.19 (1H, s, H-7), 7.14 (1H, s, H-8), 7.02 (1H, s, H-
3), 4.11 (2H, m, H-5), 4.06 (3H, s, MeO-11), 4.03 (3H, s, MeO-9),
4.02 (3H, s, MeO-2), 3.18 (2H, m, H-4); NOEDs δ 9.21 (H-11) →
4.06 (MeO-10, 9.1%), δ 4.11 (H2-5, 1.5%) ← 8.86 (NCHO) → 7.19
1
(s), 1365 (s), 1280 (s), 1240 (s), 1165 (s), 1122 (s) cm−1; H NMR
(CDCl3, 400 MHz) δ 6.99 (1H, s, H-8), 6.67 (1H,, H-3), 3.94 (3H, s,
MeO-9), 3.88 (3H, s, MeO-2), 2.52 (3H, s, NCH3); EIMS (20 eV) m/
z 391 (4, [M + 2]+), 390 (14), 389 (46, [M]+), 388 (100), 346 (22).
11-Sulfonyl-1,11-anhydro-N-propylnorbracteoline (8c): mp 190−
193 °C (MeOH); IR νmax 3400 (br s), 2960 (s), 2940 (s), 1580 (s),
1
1505 (s), 1365 (s), 1270 (s), 1240 (s), 1175 (s), 1115 (s) cm−1; H
NMR (CDCl3, 400 MHz) δ 7.02 (1H, s, H-8), 6.67 (1H, s, H-3), 3.94
(3H, s, MeO-9), 3.88 (3H, s, MeO-2), 2.87 (1H, m) and 2.47 (1H, m)
(NCH2C2H5), 1.59 (2H, m, NCH2CH2CH3), 0.95 (3H, t, J = 7.2 Hz,
NC2H4CH3); 13C NMR (CDCl3, 100 MHz) δ 147.7 (s, C-2 and C-9),
142.0 (s, C-10), 135.8 (s, C-1), 127.1 (s, C-1a), 124.6 (s, C-3a), 118.3
(s, C-7a), 116.7 (s, C-1b), 115.6 (d, C-8), 112.5 (d, C-3), 58.0 (d, C-
6a), 56.6 (q, MeO-9), 56.4 (q, MeO-2), 49.4 (t, C-5), 33.2 (t, C-7),
29.0 (t, C-4), 56.1 (t, NCH2C2H5), 19.2 (t, NCH2CH2CH3), 12.0 (q,
NC2H4CH3); EIMS (20 eV) m/z 419 (2, [M + 2]+), 417 (50, [M]+),
416 (100), 389 (18), 388 (85), 359 (35); HREIMS m/z 417.1207
[M]+, calcd for C21H23O6NS, 417.1246.
Reaction of N-Acylnorglaucines with 90% H2SO4. Compound
3a (100 mg, 0.271 mmol) and 90% H2SO4(aq) (2.0 mL) were placed
in a screw-tight sealed flask (25 mL). The mixture after degassing by
vacuum was stirred for 4 days at room temperature. The reaction
mixture was added dropwise into a beaker containing ice−water (30
mL), and the resultant suspension was adjusted to pH 8.0 with
ammonia−water (25%) at 0 °C, passed through an Amberlite XAD-2
column (20 g), and eluted in sequence with H2O (100 mL) and
MeOH (100 mL) to give 9a (47.1 mg, 37.5%) and a trace amount of
10 (1 mg) from the MeOH elution. In a similar manner, 9b (50.4 mg,
41.2%) and 9c (51.1 mg, 43%) were afforded from 3b (101 mg, 0.264
F
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(H-7, 14.1%), δ 3.18 (H2-4, 5.0%) ← 7.02 (H-3) → 4.02 (MeO-2,
9.1%); EIMS (20 eV) 353 (100, [M]+), 338 (35), 311 (88), 297 (40).
N-Formyl-9-sulfonylseconorthaliporphine (13a): mp 193−195 °C
(MeOH); IR νmax 3500, 3200, 1680, 1525, 1480, 1385, 1260, 1180,
1050 cm−1; 1H NMR (MeOH-d4, 400 MHz) δ 9.57 (1H, s, H-5), 8.54
(1H, s, H-10), 8.41 (1H, s, H-8), 8.04 (1H, s, NCHO), 7.28 (1H, s, H-
2), 4.04 (3H, s, MeO-7), 4.01 (3H, s, MeO-3), 4.00 (3H, s, MeO-6),
3.57 (2H, m, H-11), 3.28 (2H, m, H-12); NOEDs δ 8.41 (H-8) →
4.04 (MeO-9, 11.0%), δ 3.28 (H2-12, 3.3%) ← 8.54 (H-10) → 3.57
(H-11, 9.0%), δ 3.28 (H2-11, 4.8%) ← 7.28 (H-2) → 4.01 (MeO-3,
11.6%); FABMS m/z 458 (48, [M + Na]+), 436 (60, [M + H]+), 435
(100, [M]+); HREIMS m/z 435.1010 [M]+, calcd for C20H21O8NS,
435.0991.
(−)-5a to give (−)-5c (20.1 mg, 46%): [α]25D −55.2 (c 0.32, MeOH),
mp 66−69 °C (MeOH).
Mechanical Response of Thaliporphine Homologues on Rat
Cardiac Tissues. The functions of the prepared thaliporphine
homologues on rat cardiac tissues were evaluated following a reported
method.1 Strips of the right atrium, left atrium, and right ventricle,
quickly dissected from the hearts of male Wistar-Kyoto rats, were put
in an organ bath containing Tyrode’s solution, bubbled with CO2−O2
(1:19), at 36 0.2 °C. Contractions of spontaneously beating right
atria and of electrically driven left atria and right ventricular strips were
recorded by a force displacement transducer, connected to one end of
the preparation by a fine silk thread. An optimal preload (0.5−1.0 g)
on these preparations was set to obtain the maximum developed
tension. The left atria and right ventricular strips were stimulated at a
frequency of 2 Hz by a 1 ms rectangular pulse at supramaximal
intensity via an isolated stimulator. Compounds were dissolved in
DMSO, and the final concentration of DMSO in the bath did not
exceed 0.1% (v/v), which caused no significant effect on the muscle
contraction and heart rate.
Preparation of ( )-Wilsonirine [( )-14]. Compound 10 (203
mg, 0.632 mmol), acetic acid (40 mL), and 10% Pt/C (150 mg) were
placed in a 50 mL flask, in turn, and then the flask was placed in a Par
hydrogenation apparatus. After degassing as usual for hydrogenation,
H2 (5 bar) was introduced and the mixture was stirred at 60 °C for 2
days. The reaction mixture was filtered with the aid of a Celite cake.
After filtration, the Celite cake was washed with acetone (200 mL).
The filtrate and acetone washings were evaporated to give a residue
that yielded ( )-14 (151 mg, 72%) after purification over a silica gel
column (6 g, 70−230 mesh), eluted with 2−6% MeOH−CHCl3.
( )-Wilsonirine [( )-14]: mp 210−212 °C (MeOH) (lit.12 202−
ASSOCIATED CONTENT
■
S
* Supporting Information
1D (1H and 13C NMR) and HMBC spectra of 8c and 10 and
1H NMR spectrum of the (−)-di-O-4-toluoyl-L-tartrates of
( )-14 (top) and (−)-14. This material is available free of
charge via the Internet at http://pubs.acs.org.
1
204 °C); H NMR (MeOH-d4, 400 MHz) δ 8.18 (1H, s, H-11), 6.88
(1H, s, H-8), 6.72 (1H, s, H-3), 3.89 (3H, s, MeO-2), 3.85 (3H, s,
MeO-9), 3.84 (3H, s, MeO-10); EIMS (70 eV) m/z 327 (70, [M]+),
326 (100).
AUTHOR INFORMATION
Corresponding Author
*Tel/fax: +886 2 23916127. E-mail: shoeilee@ntu.edu.tw.
Optical Resolution of ( )-Wilsonirine [( )-14]. To a 500 mL
round-bottomed flask were added ( )-14 (2.0 g, 6.12 mmol), (−)-di-
O-4-toluoyl-L-tartaric acid (2.6 g, 6.42 mmol), and MeOH (150 mL).
The mixture was stirred under reflux until a solution was formed. After
cooling to room temperature, the precipitate was filtered off and was
recrystallized from MeOH three times to give white crystalline salts of
(−)-14 and (−)-di-O-4-toluoyl-L-tartaric acid [(−)-15] (680 mg) with
■
Notes
The authors declare no competing financial interest.
[α]22 −90 (c 0.32, MeOH). The solution of (−)-15 (680 mg) in
ACKNOWLEDGMENTS
D
■
H2O (80 mL) was adjusted to pH 8.0 by ammonia−water (25%) and
extracted with CHCl3 (80 mL × 4). The combined CHCl3 solution
was dried (Na2SO4) and evaporated under reduced pressure to give a
pinkish solid, which, upon recrystallization from MeOH, yielded
(−)-14 (281 mg): mp 111−113 °C, [α]25D −55 (c 0.31, MeOH) [lit.13
mp 106−108 °C, [α]24D −53.9 (c 0.2, MeOH)]. The mother liquor of
the crystalline (−)-15 was evaporated under reduced pressure to give a
residue, which was suspended in H2O (100 mL), adjusted to pH 8.0
by ammonia−water (25%), and extracted with CHCl3 (100 mL × 4).
The combined CHCl3 layers were dried (Na2SO4) and evaporated
under reduced pressure to give a residue (1.22 g). Optical resolution of
this residue with (+)-di-O-4-toluoyl-D-tartaric acid (1.5 g) was carried
out by fractional recrystallization from MeOH three times to give
(+)-15 (580 mg): [α]25D +93.3 (c 0.31, MeOH), which yielded (+)-14
(230 mg), mp 110−113 °C and [α]25D 56.7 (c 0.31, MeOH) [lit.13 mp
This work was supported by National Science Council,
Republic of China, under grants NSC 85-2331-B-002-241,
NSC 97-2323-B-002-015, and NSC 100-2325-B-002-021.
DEDICATION
■
Dedicated to Dr. Lester A. Mitscher, of the University of
Kansas, for his pioneering work on the discovery of bioactive
natural products and their derivatives.
REFERENCES
■
(1) Su, M. J.; Chang, Y. M.; Chi, J. F.; Lee, S. S. Eur. J. Pharmacol.
1994, 254, 141−150.
(2) Teng, C. M.; Yu, S. M.; Lee, S. S.; Ko, F. N.; Su, M. J.; Huang, T.
F. Eur. J. Pharmacol. 1993, 233, 7−12.
107−109 °C, [α]24 +54.8 (c 0.1, MeOH)], from (+)-15 (580 mg),
D
following a similar procedure to that for the recovery of (−)-14 from
(−)-15.
(3) Ahmad, R.; Saa,
1230.
(4) Castedo, L.; de Lera, A. R.; Saa,
Heterocycles 1980, 14, 1135−1138.
́
J. M.; Cava, M. P. J. Org. Chem. 1977, 42, 1228−
Preparation of (−)-Thaliporphine [(−)-5a] and (−)-N-Propyl-
wilsonirine [(−)-5c]. To the mixture of (−)-14 (51 mg, 0.16 mmol),
MeOH (4 mL), and 37% HCHO (0.1 mL) in a 50 mL round-
bottomed flask was added NaBH4 (50 mg) portionwise while stirring
at room temperature. The reaction mixture was stirred for 1 h and was
evaporated to give a residue, which was partitioned between H2O (50
mL) and CHCl3 (50 mL × 3). The combined CHCl3 solution was
dried (Na2SO4) and evaporated to give a residue (49.3 mg), which was
chromatographed over a silica gel column (70−230 mesh, 5 g), eluted
́
J. M.; Suau, R.; Villaverde, C.
(5) Huang, W. J.; Chen, C. H.; Singh, O. V.; Lee, S. L.; Lee, S. S.
Synth. Commun. 2002, 32, 3681−3686.
(6) Lee, S. S.; Tsai, F. Y.; Chen, I. S.; Liu, K. C. S. J. Chin. Chem. Soc.
(Taipei, Taiwan) 1993, 40, 209−212.
(7) Chiou, C. M.; Kang, J. J.; Lee, S. S. J. Nat. Prod. 1998, 61, 46−50.
(8) Nakanishi, K.; Solomon, P. H. Infrared Absorption Spectroscopy,
2nd ed.; Holden-Day, Inc.: San Francisco, 1981; p 51.
(9) Hufford, C. D.; Sharma, A. S.; Oguntimein, B. O. J. Pharm. Sci.
1980, 69, 1180−1183.
with 2% MeOH−CHCl3, to give (−)-5a (39.3 mg, 75%): [α]25
D
−63.3 (c 0.40, MeOH), mp 185−187 °C (MeOH). Then, (−)-14
(42.6 mg, 0.13 mmol) in DMF (4 mL) was reacted with n-propyl
bromide (20 μL) in the presence of K2CO3 (60 mg) in a 2 mL round-
bottomed flask at 50 °C overnight. After removal of DMF using an oil
pump, the residue was purified in a similar manner as described for
(10) Cava, M. P.; Noguchi, I.; Buck, K. T. J. Org. Chem. 1973, 38,
2394−2397.
(11) Jossang, A.; Leboeuf, M.; Cave, A. J. Nat. Prod. 1986, 49, 1028−
́
1035.
G
dx.doi.org/10.1021/np3007765 | J. Nat. Prod. XXXX, XXX, XXX−XXX

Journal of Natural Products
Article
(12) Kupchan, S. M.; Liepa, A. J. J. Am. Chem. Soc. 1973, 95, 4062−
4062.
(13) Hara, H.; Komoriya, S.; Miyashita, T.; Hoshino, O. Tetrahedron:
Asymmetry 1995, 6, 1683−1692.
(14) Su, M. J.; Liu, P. J.; Tseng, C. D.; Tseng, Y. Z.; Lee, C. S. J.
Formosan Med. Assoc. 1994, 93, 673−680.
(15) Felix, J. P.; King, F.; Shevell, J. L.; Garcia, M. L.; Kaczorowski, G.
J.; Bick, I. R. C.; Slaughter, R. S. Biochemistry 1992, 31, 11793−11800.
H
dx.doi.org/10.1021/np3007765 | J. Nat. Prod. XXXX, XXX, XXX−XXX