Confirmation of the structure of (3S)-3-hydroxyquinine: Synthesis and X-ray crystal structure of its 9-aceto analogue

Article abstract of DOI:10.1021/np050015g

3(S)-3-Hydroxyquinine (2) has been separated from its epimeric mixture at C-3 by conversion into the 9-aceto analogue followed by chromatography. The molecular structure of the acetate was determined through single-crystal X-ray analysis, and this confirms the structure of (3S)-3-hydroxyquinine (2), the major metabolite of quinine (1).

Full text of DOI:10.1021/np050015g

9
42
J. Nat. Prod. 2005, 68, 942-944
Confirmation of the Structure of (3S)-3-Hydroxyquinine: Synthesis and X-ray
Crystal Structure of Its 9-Aceto Analogue
†
†
‡
,†
P. V. V. Srirama Sarma, Dongmei Han, Jefferey R. Deschamps, and James M. Cook*
Department of Chemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, and Laboratory for the Structure
of Matter, Code 6030, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, D.C. 20375
Received January 16, 2005
3
9
(S)-3-Hydroxyquinine (2) has been separated from its epimeric mixture at C-3 by conversion into the
-aceto analogue followed by chromatography. The molecular structure of the acetate was determined
through single-crystal X-ray analysis, and this confirms the structure of (3S)-3-hydroxyquinine (2), the
major metabolite of quinine (1).
Quinine (1) still remains the drug of choice for the
Scheme 1. Synthesis of 3(S)-3-Hydroxyquinine (2)
treatment of severe and complicated malaria in most parts
1
,2
of the world. Knowledge of the biotransformation of
quinine (1) in humans is incomplete. Although several
quinine (1) metabolites have been isolated and character-
ized, neither the quantitative importance of these metabo-
lites on the elimination of quinine nor the metabolic
3,4
pathways have been fully elucidated. Quinine (1) and its
diastereomer quinidine are metabolized in a very similar
fashion in man. The metabolites that result are the
products of oxidation reactions taking place on either the
quinoline or the quinuclidine moieties. In vitro studies with
human liver microsomes have shown that quinidine oxida-
tion to the (3S)-3-hydroxy and N-oxide products appears
to be catalyzed primarily by cytochrome P450-3A4.5
-7
The major biotransformation product of the metabolism
of quinidine has been isolated from human urine and was
8
found to be (3S)-3-hydroxyquinidine. On the basis of this
finding, 3-hydroxyquinine has been postulated to be the
major metabolite of quinine (1); however, only NMR
9
evidence in regard to the assignment of the configuration
at C-3 has been reported. Quinine and its metabolites have
been analyzed in plasma and urine using HPLC and GC-
MS methods, and 3-hydroxyquinine was indeed found as
the major metabolite of quinine.1
0-12
However, only one
epimer of 3-hydroxyquinine was reported as a major
metabolite, and it was proposed as the 3(S) isomer. In this
context, it was of importance to establish, unequivocally,
the structures of both epimers of 3-hydroxyquinine. Herein,
we wish to report the synthesis and the X-ray crystal
structure of the 9-aceto analogue of 3(S)-3-hydroxyquinine
and its conversion into 3(S)-3-hydroxyquinine (2). The
absolute configuration of 3(S)-3-hydroxyquinine (2) has,
therefore, been determined, and the comparison of NMR
spectra to those of previous reports9 can now be made.
mixture was rapidly and conveniently separated by column
chromatography on silica gel.
The major isomer was crystallized from CH Cl -hexane,
2
2
and its absolute configuration was established by single-
crystal X-ray analysis, the structure of which is depicted
in Figure 2 (see Experimental Section for details). This
confirmed the configuration of the major diastereomer 4
as 3(S). Hydrolysis of 4 under basic conditions with K CO
2
3
,13
in methanol yielded pure 3(S)-3-hydroxyquinine (2). The
structure of 2 was further established using 2D-NMR
spectroscopy (see Figure 1 for the NOE observed for 3(S)-
3-hydroxyquinine) and correlated with spectra from earlier
The 3-hydroxyquinine was synthesized from quinine
following the scheme reported previously by Diaz-Arauzo
9
,13
et al.
The epimeric mixture of 2 and 3, obtained in a 4:1
9
ratio, could not be separated by flash chromatography on
either silica gel or alumina. It appears that the isomers 2
and 3 undergo equilibration on chromatography. Conse-
quently, the mixture of 2 and 3 was partially acylated to
generate the epimeric mixture of 9-aceto analogues of
NMR work. This makes available the correct structures
of both metabolites (3-hydroxyquinine) and can be em-
ployed to clear the confusion in the literature as regards
the major metabolite 2 of quinine (1). In addition, the pure
R and S isomers of 3-hydroxyquinine as well as the related
9-aceto analogues are now available for biological screen-
ing.
3-hydroxyquinine 4 and 5 (see Scheme 1). This epimeric
*
To whom correspondence should be addressed. Tel: (414) 229-5856.
Experimental Section
General Experimental Procedures. The experimental
protocols were carried out as previously reported.
Fax: (414) 229-5530. E-mail: capncook@uwm.edu.
†
‡
University of Wisconsin-Milwaukee.
Naval Research Laboratory.
14
1
0.1021/np050015g CCC: $30.25
© 2005 American Chemical Society and American Society of Pharmacognosy
Published on Web 05/20/2005

Notes
Journal of Natural Products, 2005, Vol. 68, No. 6 943
C-4), 42.8 (CH
2
, C-6), 56.2 (CH
, C-2), 72.1 (C, C-3), 73.9 (CH, C-9), 101.9 (CH, C-5′), 113.6
, C-11), 119.2 (CH, C-3′), 122.3 (CH, C-7′), 127.3 (C, C-4A′),
3 3
, OCH ), 58.9 (CH, C-8), 65.1
(
CH
CH
2
(
2
1
1
3
6
32.3 (CH, C-8′), 143.9 (C and CH, C-4′, C-10), 145.2 (C, C-8A′),
47.8 (CH, C-2′), 158.5 (C, C-6′), 170.3 (C, COCH ); EIMS m/z
82 [M ], 231 (40), 189 (25), 152 (100); anal. C 57.67%, H
.07%, N 5.58%, calcd for C22 ‚1.2CH Cl , C 57.53%,
3
+
H
26
N
2
O
4
2
2
H 5.91%, N 5.78%.
(R)-3-Hydroxyquinine 9-acetate (5): mp 166-168 °C;
) 0.40 [silica gel, CHCl (98%)-MeOH (2%)]; IR (KBr) νmax
3
R
f
3
-
1
1
3
280, 2925, 1729, 1033 cm ; H NMR (CDCl
3
, 300 MHz) δ
8
.73 (1H, d, J ) 4.53 Hz), 8.02 (1H, d, J ) 9.2 Hz), 7.47 (1H,
d, J ) 2.62 Hz), 7.39-7.37 (1H, m), 7.35 (1H, d, J ) 2.66 Hz),
6
5
.54 (1H, d, J ) 7.56 Hz), 6.11 (1H, dd, J ) 10.77, 17.31 Hz),
.28 (1H, d, J ) 17.28 Hz), 5.15 (1H, d, J ) 11.01 Hz), 3.97
(
3H, s), 3.70 (1H, q, J ) 16.60 Hz), 3.19-3.10 (1H, m), 2.89
Figure 1. NOE observed for (3S)-3-hydroxyquinine (2).
(1H, d, J ) 14.33 Hz), 2.74 (1H, dd, J ) 1.25, 14.40 Hz), 2.64-
.55 (1H, m), 2.27-2.14 (1H, m), 2.14 (3H, s), 1.93-1.91 (2H,
2
1
3
3
m), 1.67-1.63 (2H, m), 1.53-1.42 (1H, m); C NMR (CDCl ,
7
1
1
1
5 MHz) 21.0, 23.1, 24.5, 33.5, 41.9, 55.6, 58.1, 64.3, 72.1, 73.4,
01.5, 113.3, 118.9, 121.8, 127.1, 131.6, 142.6, 143.7, 144.6,
+
47.3, 157.8, 170.0; EIMS m/z 382 [M ], 231 (40), 189 (25),
52 (100).
3
2 3
(S)-3-Hydroxyquinine (2). Anhydrous K CO (108 mg,
0.78 mmol) was added to a solution of 4 (100 mg, 0.26 mmol)
in methanol (5 mL). The mixture that resulted was stirred at
room temperature for 3 h. It was then diluted with water and
extracted with ethyl acetate (3 × 50 mL). The combined
2 4
organic extracts were washed with brine, dried (Na SO ), and
filtered, and the solvent was removed under reduced pressure.
The residue that resulted was washed with ether to yield pure
1
5
2
0
0
f
(80 mg, 90%): mp 148-150 °C [lit. mp 147-149 °C]; R )
25
.15 [silica gel, CHCl
.50, MeOH); IR (KBr) νmax 3350, 1615, 1500, 1240 cm ; H
OD, 500 MHz) δ 8.67 (1H, d, J ) 4.55 Hz, H-2′),
3
(98%)-MeOH (2%)]; [R] -196.80° (c
D
-
1 1
NMR (CD
3
7
7
1
.96 (1H, d, J ) 9.15 Hz, H-8′), 7.70 (1H, d, J ) 4.55 Hz, H-3′),
.46-7.42 (2H, m, H-5′ and H-7′), 5.98 (1H, dd, J ) 10.85,
7.25 Hz, H-10), 5.60 (1H, d, J ) 3.35 Hz, H-9), 5.22 (1H, d, J
)
17.2 Hz, H-11t), 5.02 (1H, d, J ) 10.85 Hz, H-11c), 3.99 (3H,
s, OCH
m, H-8 and H-2c), 2.83-2.77 (2H, m, H-6ex and H-2t), 2.14-
.10 (1H, m, H-5ex), 2.06-2.01 (1H, m, H-7en), 1.82 (1H, br s,
3
), 3.63 (1H, br t, J ) 10.5 Hz, H-6en), 3.07-3.00 (2H,
Figure 2. Structure of the 9-aceto analogue of 3(S)-3-hydroxyquinine
(
4) as determined by X-ray crystallography with displacement ellipsoids
2
shown at the 50% level.
13
H-4), 1.67-1.62 (1H, m, H-5en), 1.48-1.43 (1H, m, H-7ex);
NMR (CD OD, 125 MHz) δ 20.8 (CH , C-5), 22.8 (CH , C-7),
34.3 (CH, C-4), 43.0 (CH , C-6), 55.5 (CH , OCH ), 59.5 (CH,
C-8), 64.3 (CH , C-2), 71.1 (C, C-9), 71.3 (CH, C-3), 101.5 (CH,
C-5′), 112.0 (CH , C-11), 119.1 (CH, C-3′), 122.3 (CH, C-7′),
C
3
2
2
(
3S)-3-Hydroxyquinine 9-acetate (4). To a round-bot-
2
3
3
tomed flask (50 mL) that contained a solution of the epimeric
mixture of 3-hydroxyquinines 2 and 3 (800 mg, 2.35 mmol)
and pyridine (8 mL) was added acetic anhydride (0.34 mL, 3.53
mmol), and the contents were heated at 100 °C for 3 h. The
reaction mixture was cooled and the pyridine was removed
under reduced pressure. The residue was dissolved in MeOH
2
2
127.2 (C, C-4A′), 130.4 (CH, C-8′), 143.6 (CH, C-10), 143.8 (C,
C-8A′), 147.2 (CH, C-2′), 149.7 (C, C-4′), 158.7 (C, C-6′); EIMS
+
m/z no M peak observed 189 (95), 152 (100); anal. C 67.94%,
H 7.04%, N 7.70%, calcd for C20
24 2 3 3
H N O ‚0.8CH OH, C 68.24%,
(
10 mL), followed by the addition of a cold saturated solution
H 7.49%, N 7.65%. The spectral data for 2 were in excellent
9,13
of methanolic hydrogen chloride (10 mL). The solvent was
removed under reduced pressure, and the solid was dissolved
in water and extracted with chloroform (3 × 50 mL). The
organic layer was discarded, the aqueous phase was brought
agreement with the literature.
3(R)-3-Hydroxyquinine (3): mp 157 °C; R
gel, CHCl (98%)-MeOH (2%)]; IR (KBr) νmax 3350, 1610, 1500,
f
) 0.18 [silica
3
1 1
-
3
1248 cm ; H NMR (CD OD, 300 MHz) δ 8.67 (1H, d, J ) 4.5
to pH 8-9 with Na
chloroform (3 × 100 mL). The organic layer was washed with
water and brine and dried (Na SO ). The solvent was removed
under reduced pressure, and the two epimers were separated
2
CO
3
, and the solution was extracted with
Hz), 7.94 (1H, d, J ) 9.1 Hz), 7.70 (1H, d, J ) 4.5 Hz), 7.44-
7.39 (2H, m), 6.14 (1H, dd, J ) 10.8, 17.3 Hz), 5.67 (1H, d, J
) 2.88 Hz), 5.28 (1H, d, J ) 17.3 Hz), 5.12 (1H, d, J ) 10.77
Hz), 3.98 (3H, s), 3.83-3.73 (1H, m), 3.47-3.42 (1H, m), 3.36-
3.32 (1H, m), 3.00-2.96 (1H, m), 2.82-2.78 (1H, m), 2.71-
2
4
by flash chromatography [silica gel, CHCl
3
(98%)-MeOH
) 0.35 [silica gel, CHCl (98%)-
-57.7° (c 0.60, MeOH); IR (KBr) νmax 3283,
1
3
(
2%)]. 4: mp 146-148 °C; R
f
3
3
2.62 (1H, m), 1.92-1.62 (4H, m); C NMR (CD OD, 75 MHz)
2
5
MeOH (2%)]; [R]
D
δ 158.2, 149.1, 146.6, 143.3, 142.4, 129.8, 126.6, 121.9, 118.5,
112.0, 101.0, 71.2, 70.8, 63.5, 58.5, 55.0, 42.3, 33.4, 22.0, 20.4.
X-ray Crystal Structure of 3(S)-3-Hydroxyquinine
9-acetate (4). Single-crystal X-ray diffraction data on com-
pound 4 were collected at 103 K using Mo KR radiation and a
Bruker SMART 1000 CCD area detector. A 0.40 × 0.35 × 0.28
-
1
1
2
8
7
3
936, 1732, 1623, 1033 cm ; H NMR (CDCl , 500 MHz) δ
.78 (1H, d, J ) 4.5 Hz, H-2′), 8.08 (1H, d, J ) 9.2 Hz, H-8′),
.49 (1H, d, J ) 2.15 Hz, H-5′), 7.43 (1H, dd, J ) 2.65, 9.15
Hz, H-7′), 7.39 (1H, d, J ) 4.5 Hz, H-3′), 6.60 (1H, br d, J )
5
.85 Hz, H-9), 6.11 (1H, dd, J ) 10.8, 17.25 Hz, H-10), 5.34
1H, d, J ) 17.85 Hz, H-11t), 5.18 (1H, d, J ) 10.8 Hz, H-11c),
.02 (3H, s, OCH
3
(
mm crystal was prepared for data collection by coating with
4
3
), 3.30 (1H, br q, J ) 16 Hz, H-8), 3.16 (1H,
high-viscosity microscope oil (Paratone-N, Hampton Research).
The oil-coated crystal was mounted on a glass rod and
transferred immediately to the cold stream (-170 °C) on the
diffractometer. The crystal was tetragonal in space group
m, H-6en), 3.02 (1H, br d, J ) 14.25 Hz, H-2c), 2.87-2.84 (2H,
br m, H-2t, H-6ex), 2.23-2.19 (1H, br m, H-5ex), 2.19 (3H, s,
COCH
m, H-7en), 1.57 (1H, br m, H-5en); C NMR (CDCl
δ 21.5 (CH and CH , C-5, COCH ), 26.4 (CH , C-7), 34.7 (CH,
3
), 1.92-1.85 (2H, br m, H-4, H-7ex), 1.77-1.74 (1H, br
13
3
, 125 MHz)
P4
1 1
2 2 with unit cell dimensions a ) b ) 10.8089(12) Å, c )
2
3
3
2
42.926(7) Å. Corrections were applied for Lorentz polarization

9
44 Journal of Natural Products, 2005, Vol. 68, No. 6
Notes
and absorption effects. Data were 95.4% complete to 28.31° θ
(2) List, A. F. Leukemia 1996, 10, 937-942.
(
(
(
3) Barrow, S. E.; Taylor, A. A.; Horning, E. C.; Horning, M. G. J.
Chromatogr. 1980, 181, 219-226.
4) Wanwimolruk, S.; Wong, S. M.; Zhang, H.; Coville, P. F.; Walker, R.
J. J. Pharm. Pharmacol. 1995, 47, 957-963.
(approximately 0.75 Å resolution) with an average redundancy
of 5.5. The structure was solved by direct methods and refined
2
by full-matrix least squares on F values using the programs
1
7
found in the SHELXTL suite. Parameters refined included
atomic coordinates and anisotropic thermal parameters for all
non-hydrogen atoms. Hydrogen atoms on carbons were in-
cluded using a riding model [coordinate shifts of C applied to
H atoms] with C-H distance set at 0.96 Å. The absolute
configuration was set based on the known configuration of the
optically pure quinine (one of the starting materials for the
synthesis). The asymmetric unit contains one molecule plus
two molecules of solvent (dichloromethane). Both solvent
molecules were disordered; one of these sits on a special
position at half-occupancy. Atomic coordinates for compound
5) Guengerich, F. P.; Muller-Enoch, D. M.; Blair, I. A. Mol. Pharmacol.
1
986, 30, 287-295.
(6) Zhao, X. J.; Yokoyama, H.; Chiba, K.; Wanwimolruk, S.; Ishizaki, T.
J. Pharmacol. Exp. Ther. 1996, 279, 1327-1334.
(7) Zhang, H.; Coville, P. F.; Walker, R. J.; Miners, J. O.; Birkett, D. J.;
Wanwimolruck, S. Br. J. Clin. Pharmacol. 1997, 43, 245-252.
(
8) Carroll, F. I.; Philip, A.; Coleman, M. C. Tetrahedron Lett. 1976, 21,
757-1760.
1
(
9) Diaz-Arauzo, H. Synthesis, High-Resolution NMR Spectroscopy of the
Metabolites of Quinine and Quinidine and Antibody-Mediated Platelet
Destruction. M.S. Thesis, University of Wisconsin-Milwaukee, WI,
1988.
4
have been deposited with the Cambridge Crystallographic
(10) Mirghani, R. A.; Ericsson, O.; Gustafsson, L. L. J. Chromatogr. B
998, 708, 209-216.
1
Data Centre (deposition number 260728). Copies of the data
can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK [fax: +44(0)-1223-
(
(
(
11) Bannon, P.; Yu, P.; Cook, J. M.; Roy, L.; Villeneuve, J. P. J.
Chromatogr. B 1998, 715, 387-393.
12) Mirghani, R. A.; Ericsson, O.; Cook, J. M.; Yu, P.; Gustafsson, L. L.
J. Chromatogr. B 2001, 754, 57-64.
336033 or e-mail: deposit@ccdc.cam.ac.uk
13) Diaz-Arauzo, H.; Cook, J. M.; Christie, D. J. J. Nat. Prod. 1990, 53,
Acknowledgment. We acknowledge NIDA and NIMH
MH 46851) for support of this work.
1
12-124.
(14) Yu, P.; Wang, T.; Li, J.; Cook, J. M. J. Org. Chem. 2000, 65, 3173-
191.
(
3
Supporting Information Available: Crystal data and structural
(15) Brodie, B. B.; Baer, J. E.; Craig, L. C. J. Biol. Chem. 1951, 188, 567-
refinement for 4. Coordinates are also available from Cambridge
Crystallographic Database.16 This material is available free of charge
via the Internet at http://pubs.acs.org.
581.
(16) Cambridge Crystallographic Database, 12 Union Road, Cambridge
CBZ 1EZ, UK (deposit@ccdc.cam.ac.uk).
(
17) SHELXTL v6.10; Bruker AXS Inc.: Madison, WI, 2000.
References and Notes
(
1) White, N. J. Clin. Pharmacokin. 1985, 10, 187-215.
NP050015G