3730 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 18
Flammia et al.
used as an internal standard, and J values are in Hz. Infrared
spectra were recorded on a Nicolet 5ZDX FT-IR. Optical
rotations were determined using a J asco DIP-1000 polarim-
eter; measurements were made on 1% solutions in CHCl3.
Flash chromatography was performed on silica gel (Merck
grade 60, 230-400 mesh, 60 Å). Elemental analysis was
performed by Atlantic Microlab Inc. and determined values
are within 0.4% of theory.
1H, CH), 3.8-4.0 (m, 1H, CH), 4.99 (d, J ) 10.98 1H, CHOH),
7.19-7.39 (m, 10H, ArH); IR (KBr) 3279 cm-1. Anal. Calcd
for (C22H29NO‚HCl) C, H, N.
(-)cis-N-Meth yl-2-(2-ph en yleth en -1-yl)-6-(2-oxo-2-ph en -
ylet h yl)p ip er id in e (18). (-)Lobeline HCl (1) (1.00 g, 2.67
mmol) in phosphoric acid (85%, 23 mL) was warmed at 45-
50 °C for 22 h. The reaction mixture was taken up in H2O
(100 mL) and made basic with solid K2CO3 (pH ∼ 8). The pH
was adjusted by the addition of solid NaOH (pH ∼ 10) and
the aqueous solution was extracted with EtOAc (3 × 75 mL).
The combined organic portion was dried (K2CO3) and solvent
was removed under reduced pressure to give a solid. The solid
was recrystallized from hexane to give 18 (0.06 g, 75%) as
Some of the compounds used in the present investigation
were prepared according to previously published literature
procedures; these include lobelanidine HCl (4),28 7 HCl,29
8
HCl,30 9 HCl,31 (-)sedamine HCl (10), 32 11 HI,33 12 hydrogen
oxalate,34 and lobelan HCl (14).35 Two other compounds were
also prepared by literature procedures, but because their
melting points differed somewhat from those reported in the
literature they were submitted for elemental analysis; both
analyzed correctly for C, H, and N and include lobelanine HCl
(3; mp 203-205 °C, lit.28 mp 197-198 °C) and 13 HCl (mp
170-171 °C, lit.30 mp 161-162 °C). (-)Lobeline HCl was
purchased from Sigma-Aldrich (St. Louis, MO).
colorless crystals: mp 82-24 °C; [R]25 ) -28.3; 1H NMR
D
(CDCl3) δ 1.3-1.9 (m, 6H, CH), 2.27 (s, 3H, CH3), 2.70-3.00
(m, 3H, CH), 3.47 (dd, J ) 6.45, 16.23, 1H, CH), 6.18 (dd, J )
8.67, 15.93, 1H, CdCH), 6.50 (d, J ) 15.87, 1H, CdCH), 7.2-
7.61 (m, 8H, ArH), 7.99 (d, J ) 6.99, 2H, ArH); IR (KBr) 1687,
2775, 2943 cm-1. Anal. Calcd for (C22H25NO) C, H. N.
(-)cis-N-Meth yl-2-(2-h ydr oxy-2-ph en yleth yl)-6-(2-ph en -
yleth en -1-yl)p ip er id in e (19). (-)Lobeline HCl (1) (0.50 g,
1.34 mmol) was added to a suspension of amalgamated zinc
and aqueous 5% HCl (20 mL) and heated at reflux for 15 min.
The mixture was made basic by the addition of aqueous NaOH
(1 N, 25 mL) followed by solid NaOH to a pH ) 10 and
extracted with Et2O (3 × 50 mL). The combined organic portion
was dried (MgSO4) and the solvent was removed under reduced
pressure. The resulting oil was purified by column chroma-
tography (silica gel, 30 g) using EtOAc as eluent. The oil was
taken up in hot hexane and a precipitate formed on cooling.
The precipitate was collected and recrystallized from hexane
(+)cis-N-Met h yl-2-(2-p h en ylet h yl)-6-(2-oxo-2-p h en yl-
eth yl)p ip er id in e Hyd r och lor id e (15). Pyridinium dichro-
mate (0.22 g, 0.58 mmol) was added to 16 (0.13 g free base,
0.39 mmol) in CH2Cl2 (50 mL), and the solution was allowed
to stir at room temperature. After 3 h NaOH (1 N, 50 mL)
was added and the organic layer was separated. The aqueous
portion was extracted with Et2O (3 × 50 mL) and the combined
organic portions were dried (MgSO4). The solvent was removed
under reduced pressure, the remaining oil was taken up in
anhydrous Et2O, and excess HCl(g)-saturated anhydrous Et2O
was added. The precipitate was collected by filtration and
recrystallized twice from absolute EtOH/anhydrous Et2O to
25
to give 19 (0.20 g, 46%) as a white solid: mp 109-111 °C; [R]D
) -45.7; 1H NMR (CDCl3) δ 1.4-1.7 (m, 6H, CH), 1.8-2.1 (m,
2H, CH), 2.32 (s, 3H, CH3), 2.9-3.0 (m, 1H, CH), 3.22-3.38
(m, 1H, CH), 4.9 (d, 1H, CHOH), 6.23 (dd, J ) 5.28, 16.11,
1H, CH), 6.46 (d, J ) 16.35, 1H, CH), 7.2-7.4 (m, 10H, ArH);
25
give 15 (0.05 g, 36%) as a white crystal: mp 166-168 °C; [R]D
) +12.9; 1H NMR (CDCl3) δ 1.4-1.8 (br m, 3H, CH), 1.8-2.2
(m, 3H, CH), 2.2-2.4 (m, 1H, CH), 2.5-3.1 (m, 6H, CH), 3.2-
3.5 (m, 1H, CH), 3.7-3.8 (m, 1H, CH), 3.9-4.1 (m, 1H, CH),
4.1-4.4 (m, 1H, CH), 7.16-7.38 (m, 5H, ArH), 7.50 (t, J )
8.8, 2H, ArH), 7.58-7.66 (m, 1H, ArH), 8.04 (d, J ) 7.14, 2H,
ArH); IR (KBr) 1687 cm.-1 Anal. Calcd for (C22H27NO‚HCl ‚
0.25H2O) C, H, N.
IR (KBr) 1457, 1600, 2937, 3552 cm-1. Anal. Calcd for (C22H27
NO) C, H, N.
-
(-)cis-N-Meth yl-2-(2-ch lor o-2-p h en yleth yl)-6-(2-oxo-2-
p h en yleth yl)p ip er id in e Hyd r och lor id e (20). Thionyl chlo-
ride (0.24 g, 2.01 mmol) was added to a solution of (-)lobeline
HCl (1) (0.50 g, 1.34 mmol) in CHCl3 (30 mL). The mixture
was stirred in a sealed tube at room temperature. After 24 h
the solvent was removed under reduced pressure and the
resulting oil was taken up in hot EtOAc (50 mL). Upon cooling,
a precipitate formed and was collected by filtration. The
precipitate was recrystallized from absolute EtOH/anhydrous
Et2O to give 20 (0.42 g, 80%) as colorless crystals: mp 184-
186 °C (lit.26 mp 172-174 °C); [R]D25 ) -38.4; 1H NMR (CDCl3)
δ 1.4-2.4 (m, 7H, CH), 2.72 (m, 5H, CH3), 3.3-3.5 (m, 1H,
CH), 3.8-4.0 (m, 1H, CH), 4.1-4.3 (m, 1H, CH), 4.97 (s, 1H,
CHOH), 7.30-7.7 (m, 8H, ArH), 8.03 (d, J ) 7.92, 2H, ArH);
IR (KBr) 1681 cm-1. Anal. Calcd for (C22H26ClNO‚HCl) C, H,
N.
(+)cis-N-Meth yl-2-(2-ph en yleth yl)-6-(2-h ydr oxy-2-ph en -
yleth yl)p ip er id in e Hyd r och lor id e (16). Compound 18 (0.39
g, 121 mmol) was suspended in absolute MeOH (50 mL) and
5% Pd/C (0.02 g) was added. The mixture was hydrogenated
on a Parr hydrogenation apparatus at 50 psi with shaking.
After 1.5 h the mixture was filtered through Celite and the
solvent was removed under reduced pressure. The remaining
oil was taken up in H2O (50 mL) and made basic with solid
Na2CO3 (pH ∼ 9). The aqueous solution was extracted with
Et2O (3 × 50 mL) and the combined ethereal portion was dried
(MgSO4); solvent was removed under reduced pressure and
the resulting oil was purified by column chromatography (silica
gel, 30 g) using EtOAc/hexane (4:1). The oily product was taken
up in anhydrous Et2O and excess HCl(g)-saturated anhydrous
Et2O was added. The precipitate was collected and recrystal-
lized from absolute EtOH/anhydrous Et2O to give 16 (0.10 g,
(-)Lobelin e Meth iod id e (21). Methyl iodide (0.38 g, 2.67
mmol) was added to a stirred mixture of (-)lobeline (1) (0.5 g,
1.34 mmol) and EtOAc (100 mL) and heated at reflux. After 3
h the solvent was removed under reduced pressure and the
remaining oil was purified by column chromatography (silica
gel, 60 g) using EtOAc and MeOH (9:1) as eluent. The most
polar fraction was dissolved in EtOAc and the solution stored
in a refrigerator overnight. The hygroscopic precipitate was
collected dried (33 °C, 0.5 mmHg) to give 21 (0.03 g, 5%) as
25
26%) as colorless crystals: mp 189-190 °C; [R]D ) +29.6;
1H NMR (CDCl3) δ 1.40-2.00 (m, 8H, CH), 2.32-2.91 (m, 7H,
CH), 3.51-3.58 (m, 1H, CH), 3.82-3.90 (m, 1H, CH), 5.01 (d,
J ) 11.43, 1H, CHOH), 7.18-7.41 (m, 10H, ArH); IR (KBr)
3285 cm-1. Anal. Calcd for (C22H29NO‚HCl‚0.25H2O) C. H. N.
(-)cis-N-Meth yl-2-(2-ph en yleth yl)-6-(2-h ydr oxy-2-ph en -
yleth yl)p ip er id in e Hyd r och lor id e (17). Compound 19 (0.10
g, 0.31 mmol) was suspended in absolute MeOH (50 mL) and
PtO2 (0.02 g) was added. The solution was hydrogenated on a
Parr hydrogenation apparatus at 1 atm with shaking. After 1
h the mixture was filtered through a Celite pad and the solvent
was removed under reduced pressure. The resulting oil was
taken up in NaOH (1 N, 50 mL) and extracted with Et2O (3 ×
50 mL); the combined ethereal layers were dried (MgSO4) and
solvent was removed under reduced pressure. The residual oil
was taken up in anhydrous Et2O and HCl(g) saturated
anhydrous Et2O was added. The precipitate was collected and
colorless crystals: mp 86-88 °C; [R]D ) -9.9; 1H NMR
25
(CDCl3) δ 1.71 (s, 6H, CH), 1.78-1.85 (m, 1H, CH), 2.18-2.2
(m, 1H, CH), 2.3-2.6 (m, 2H, CH), 3.30 (s, 6H, CH3), 4.2-4.4
(m, 2H, CH), 4.85 (d, J ) 7.7, 1H, CHOH), 6.96-7.04 (m, 2H,
ArH), 7.33(t, J ) 7.14 2H, ArH), 7.42 (d, J ) 7.83, 2H, ArH),
7.48 (d, J ) 7.2, 1H, ArH), 7.56 (t, J ) 6.18, 1H, ArH), 7.96 (d,
J ) 7.8, 2H, ArH); IR (KBr) 1668, 3422 cm-1. Anal. Calcd for
(C23H29INO2) C, H, N.
Ra d ioliga n d Bin d in g Assa y. The [3H]nicotine binding
assay using rat brain homogenates followed the method of
Scimeca and Martin.36 Briefly, tissue homogenates were
prepared from whole rats brain (minus cerebellum) in 10
volumes of ice-cold 0.05 M Na-K phosphate buffer (pH 7.4) and
centrifuged at 17 500g (4 °C) for 30 min. The pellet was then
recrystallized from absolute EtOH/anhydrous Et2O to give 17
25
(0.09 g, 80%) as a white crystal: mp 189-190 °C; [R]D
)
1
-27.9; H NMR (CDCl3) δ 1.4-2.0 (m, 8H, CH), 2.3-2.6 (m,
2H, CH), 2.66 (s, 3H, CH3), 2.7-2.9 (m, 2H, CH), 3.5-3.6 (m,