Artemisinin derivatives bearing Mannich base group: Synthesis and antimalarial activity

Article abstract of DOI:10.1016/S0968-0896(03)00499-1

Novel artemisinin derivatives bearing Mannich base group were prepared and tested for their antimalarial activity. These water-soluble artemisinin derivatives were more stable than sodium artesunate and few compounds were found to be more active against Plasmodium berghei in mice than artesunic acid by oral administration. Two most potent derivatives 17b and 17d were examined for their antimalarial activity against Plasmodium knowlesi in rhesus monkeys.

Full text of DOI:10.1016/S0968-0896(03)00499-1

Bioorganic & Medicinal Chemistry 11 (2003) 4363–4368
Artemisinin Derivatives Bearing Mannich Base Group:
Synthesis and Antimalarial Activity
Ying Li,a,* Zhong-Shun Yang,a Hong Zhang,a Ben-Jun Cao,a Fang-Dao Wang,a
Yu Zhang,a Yun-Lin Shi,b Jun-De Yangb and Bo-An Wub
aDepartment of Synthetic Chemistry, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences,
Chinese Academy of Sciences, Shanghai 201203, China
bDepartment of Malaria, Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences,
Beijing 100071, China
Received 18 June 2003; accepted 16 July 2003
Abstract—Novel artemisinin derivatives bearing Mannich base group were prepared and tested for their antimalarial activity. These
water-soluble artemisinin derivatives were more stable than sodium artesunate and few compounds were found to be more active
against Plasmodium berghei in mice than artesunic acid by oral administration. Two most potent derivatives 17b and 17d were
examined for their antimalarial activity against Plasmodium knowlesi in rhesus monkeys.
# 2003 Elsevier Ltd. All rights reserved.
Introduction
In the modification of chemical structure of chloroquine
(8), a number of Mannich base derivatives (Fig. 3) were
developed. Amodiaquine (9) and amopyroquine (11)
had a slight advantage over chloroquine on chlor-
oquine-resistant strains of Plasmodium falciparum.
Later, it was found that cycloquine (10) and tebuquine
(12) were more active than amodiaquine in vivo and in
clinic.13ꢀ17 It seemed that bis-Mannich bases substituted
on the amino-phenol was superior to mono-Mannich
base for antimalarial activity.
Sodium artesunate (3) is the first water-soluble artemisi-
nin derivative, which has been successfully used for
treatment of chloroquine-resistant malaria patients by iv
or im administration since the 1980’s. Due to the
instability of its aqueous solution, some research groups
attempted to find more stable water-soluble artemisinin
derivatives, and their efforts were continuously
reported.1ꢀ11 Artelinic acid (4), in which an ether bond
links artemisinin nucleus with the acidic moiety was once
considered as a good substitute for artesunate owing to
its better activity and stability.1 However, further study
revealed that sodium artelinate was slightly less active
than artemisinin and artesunate both in culture and in
vivo.12 Based on the knowledge of known basic anti-
malarial drugs, another strategy of introducing basic
group into the artemisinin molecule was considered.
Thus compounds 5, 6, 7 (Fig. 1) were prepared and tested
in vivo by our groups.8 Some of these compounds
showed more active against P. berghei in mice but less
active against P. knowlesi in rhesus monkeys than arte-
sunate. Besides, more basic artemisinin derivatives (Fig.
2) were also evaluated in vitro and in vivo.3ꢀ6,11
During the 1960’s–1970’s, Chinese researchers synthe-
sized M 6407 (13), changroline (14), 6701 (15), pyr-
onaridine (16) and their analogues (Fig. 4). According
to expectation, these compounds had good antimalarial
activity in vivo and in clinical trials.18ꢀ23 Among them,
pyronaridine was the most promising and marketed in
China and until now related studies of pyronaridine and
its combinations have been performed by some
groups.24ꢀ26 It was interesting that changroline showed
obvious antiarrhythmia activity during clinical trials for
treatment of malaria patients suffering from arrhyth-
mia, hence it became a lead compound of a new type of
antiarrythmia drugs.27ꢀ29
From these observations, the Mannich base was recog-
nized to be a useful pharmacophoric group for anti-
malarial activity. Thus, we decided to introduce the
*Corresponding author at: 555 Zu Chong Zhi Road, Zhangjiang Hi-
Tech Park, Shanghai 201203, China. Tel.: +86-21-5080-5832; fax:
+86-21-5080-7088; e-mail: yli@mail.shcnc.ac.cn
0968-0896/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0968-0896(03)00499-1

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Y. Li et al. / Bioorg. Med. Chem. 11 (2003) 4363–4368
Figure 3.
Figure 1.
Figure 4.
Figure 2.
Mannich base group into artemisinin molecule (Fig. 5)
and evaluate the antimalarial activity. The details of
their syntheses and bioevaluation as antimalarial agents
are presented.
Results and Discussion
Preparation of 17
Figure 5.
The synthesis of compound 17 is described in Scheme 1.
.
In the presence of BF3 Et2O, dihydroartemisinin 2
reacted with corresponding m- or p-acetoxy benzyl
alcohol 19 to afford ether 20 (a pair of 12-epimers).
Without purification, the basic hydrolysis of compound
20 was carried out with 0.25% KOH/EtOH followed by
the column chromatography of the crude products to
furnish 21 (12-bisomer, major product) in good yield.
Compound 21 reacted with formalin or paraformalde-
hyde and various amines to give 17 in moderate yield. It
was worth noting that Mannich reaction of 21 was car-
ried out only in dioxane or THF solution, if in alcohol
or aqueous solution, the reaction products were always
too complex for separation.
Pure free Mannich bases may be obtained by column
chromatography. They combined with organic acids
(oxalic acid, maleic acid, etc.) to yield the corresponding
salts. A few compounds were directly prepared from
Scheme 1.

Y. Li et al. / Bioorg. Med. Chem. 11 (2003) 4363–4368
4365
crude Mannich bases and organic acid, and then puri-
fied by recrystallization.
decreased and were comparable with sodium artesunate
via intravenous injection. Hence 17b and 17d were fur-
ther evaluated in the monkey model. Each monkey was
inoculated with 2 ꢁ 107 P. knowlesi intravenously on
D0. Compound 17b at 10.0 and 3.16 mg/kg/day and 17d
at 3.16 mg/kg/day were given orally from D0 to D6. The
experimental results are listed in Table 2. Compound
17b reduced parasites more rapidly than artesunic acid,
but at 3.16 mg/kg/day, 17b and 17d could not cleanse all
parasites like compound 5 did.8 Whereas artesunic acid
could cleanse all parasites at 3.16 mg/kg/day, and no
recrudescence within 105 days was observed.
The stability of their aqueous solution was determined
by TLC. They could be kept at room temperature for
several weeks without any decomposition. Undoubt-
edly, the stability of this new type of artemisinin deri-
vatives was much greater than that of sodium
artesunate.
Biological Results
17b, 17e and 17g were tested in vitro against K1 and
NF54 strains of P. falciparum and exhibited potent
activity (IC50 0.18–0.36 ng/mL or 3–6 nM) (Table 1).
The most of compound 17 were evaluated on their
antimalarial activities in vivo. The in vivo antimalarial
activity was assessed in mice infected with 1.5 ꢁ 107 P.
berghei K173 and artesunic acid or sodium artesunate
was used as a control. The compounds to be tested were
dissolved in water and administrated orally or sub-
cutaneously once a day for D0–D3. Groups of 10mice
received these compounds at dose levels of 0.615, 1.25,
2.5 or 10mg/kg. Blood smears were made on D 4,
stained and examined under microscope. The results in
Table 1 showed that 17b and 17d were much more
active than artesunic acid by oral administration. In
contrast with compound 5,8 their antimalarial activities
via subcutaneous injection were not drastically
Conclusion
In summary, artemisinin derivatives bearing Mannich
base group, another new type of water-soluble com-
pounds, showed higher stability and good antimalarial
activity though they were found to be less potent than
artesunic acid in the monkey model.
Experimental
Melting points were taken in open capillary on BUCHI-
510melting point apparatus and were uncorrected. The
IR spectra were run on Perkin-Elmer 599B spectro-
photometer. 1H NMR spectra were determined in
CD3OCD3, D2O (for salts), or CDCl3 solution on a
Table 1. Antimalarial activity of 17 against P. berghei K173 and P. falciparum K1 and NF54
Compd
R0
OH
NR2
ED50
(mg/kg/day)
ED90
(mg/kg/day)
IC50
(ng/mL)
K1
NF54
3
6.33 (po)
0.97 (iv)
ND
1.00 (po)
0.96 (sc)
>5.0ND
0.64 (po)
2.45 (sc)
>5.0ND
ND
23.37 (po)
5.25 (iv)
ND
2.68 (po)
4.11 (sc)
ND
1.201.20
17a
17b
H
H
30
30
40-CH2NMe2
40-CH2NEt2
ND
0.18
ND
0.36
17c
17 d
H
H
30
30
40-CH2-pyrrolidino
40-CH2-morpholino
ND
ND
2.72 (po)
4.68 (sc)
ND
ND
17e
17f
17g
17h
17i
17j
H
H
H
H
H
Me
30
40
40
40
40
30
40-CH2-t-butylamino
30-CH2NMe2
0.25
ND
0.26
0.17
ND
0.29
ND
30-CH2NEt2
2.8011.52
>2.0ND
>10.0
30,50-bis-(CH2-pyrrolidino)
3,5-bis-(CH2-morpholino)
40-CH2-pyrrolidino
ND
ND
9.50ND
ND
ND
ND
2.62
ND, not done.
Table 2. Rapidity of parasite clearance of 17b and 17d oral administrated on P. knowlesi in Rhesus monkeys (7-day treatment test)
Compd
Dose
(mg/kg/day)
Number of
monkeys
Parasitemia before
treatment (%)
Mean time for
50% reduction (h)
Mean time for
90% reduction (h)
Time of parasitemia
clearance (h)
3
10.0
3.16
3
3
35.0
42.7
8.21
7.84
13.74
13.3054
50
17b
17d
10.0
3.16
2
2
38.0
34.5
4.70
2.00
11.58
10.13
44
NC
3.16
1
112.0—
—
NC
NC, no clearance.

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Y. Li et al. / Bioorg. Med. Chem. 11 (2003) 4363–4368
1
JNM PS-100 or Brucker AM-400 spectrophotometer.
13C NMR spectra were determined in DMSO-d6 solu-
tion on Brucker AM-400 spectrophotometer. Elemental
analyses were performed on CE 1106 elemental analyser
and all the results had deviation within 0.4% of the
theoretical values.
2, H NMR (100 MHz, ppm, CDCl3): d 7.00 (1H, m,
aromatic H), 6.70(3H, m, aromatic H), 5.48 (1H, s, 5-
H), 4.80(1H, m, OC HCH3 ), 4.52 (1H, d, J=4.0Hz, 12-
H), 1.36 (3H, s, 15-CH3), 1.32 (3H, m, OCHCH3 ), 0.90
(3H, d, J=4.0Hz, 13-CH 3), 0.74 (3H, d, J=7.0Hz, 14-
CH3). Anal. calcd for C23H32O6: C, 68.29, H 7.97,
found: C, 68.44, H 8.20.
General method for preparation of compound 21
12ꢀ - Dihydroartemisinyl p - hydroxy - ꢁ - methyl - benzyl
ether (21d, R0=CH3). White crystal, mp 157–158 ꢂC
(from ethyl acetate–petroleum ether), yield: 63% from
Method A. To a solution of dihydroartemisinin (2, 5.7 g,
0.02 mol) and acetoxybenzyl alcohol (19, R0=H or
CH3, 0.03 mol) in 150 mL of CH2Cl2 was added five
1
2. H NMR (100 MHz, ppm, CDCl3): d 7.10, 6.80 (4H,
ꢂ
.
drops of BF3 Et2O at 0 C. The mixture was stirred at
room temperature until the reaction completed (mon-
itored by TLC). The solution was evaporated under
reduced pressure. The resultant oil was dissolved in
150mL of 0.25% KOH/EtOH and stirred at room
temperature overnight. After neutralizing with dilute
hydrochloric acid, the solution was evaporated in
vacuum. The residue was dissolved in CH2Cl2, washed,
dried, concentrated and purified by recrystallization or
column chromatography (silica gel, using ethyl acetate–
petroleum ether 5:100 v/v as the eluent ) to give 21.
q, JAB=8.0Hz, aromatic H), 6.79 (2H, q, JAB=8.4 Hz,
aromatic H), 5.46 (1H, s, 5-H), 4.80(1H, m, OC HCH3),
4.14 (1H, d, J=4.0Hz, 12-H ), 1.44 (3H, s, 15-CH 3),
1.30(3H, m, OCHC H3), 0.88–0.80 (6H, m, 13-CH3, 14-
CH3). Anal. calcd for C23H32O6: C, 68.29, H 7.97,
found: C 68.44, H 8.20.
General method for preparation of compound 17
Method A. To a solution of 21 (5 mmol) in 80mL of
dioxane (or THF) was added excess paraformaldehyde
(occasionally, formalin, 15ꢃ20mmol) and amine
(10ꢃ30mmol). The resulting mixture was heated at
60 ꢂC over 12 h and then evaporated in vacuum. The
residue was extracted with CH2Cl2 (or EtOAc), the
extract was washed successively with water, brine and
then dried (MgSO4) and concentrated in vacuum. The
crude products were purified by column chromato-
graphy (silica gel) using ethyl acetate–petroleum ether
(1:4 to 1:0) as the eluent to give 17.
Method B. Compound 20 was first isolated by column
chromatography to afford pure 12-b isomer and then
saponified as the procedure above mentioned.
12ꢀ-Dihydroartemisinyl m-hydroxybenzyl ether (21a,
R0=H). White crystal, mp 140–142 ꢂC (from ethyl ace-
tate–petroleum ether), yield: 57% from 2. 1H NMR
(100 MHz, ppm, CD3COCD3):d 6.60–7.20 (4H, m, aro-
matic H), 5.42 (1H, s, 5-H), 4.78 (1H, d, J=4 Hz, 12-H),
4.70, 4.35 (2H, q, JAB=12 Hz, OCH2), 3.32 (1H, s, OH),
1.28 (3H, s, 15-CH3), 0.88–0.80 (6H, m, 13-CH3, 14-
CH3). Anal. calcd for C22H30O6: C, 67.67, H, 7.74,
found: C, 68.04, H 8.04.
Method B. A solution of excess paraformaldehyde and
amine (as mentioned above) in dioxane was refluxed for
2 h then cooled to 60 ꢂC. After adding 21, the mixture
was stirred for 24 h at the same temperature. The
workup was the same as above.
12ꢀ - Dihydroartemisinyl p - hydroxybenzyl ether (21b,
R0=H) and its epimer. White crystal, mp 155–156 ꢂC
(from ethyl acetate–petroleum ether), yield: 68% from
30 -Hydroxy-40 -dimethylaminomethyl-benzyl 12-ꢀ-dihy-
droartemisinyl ether oxalate (17a). White crystal, mp
ꢂ
1
1
2. H NMR (400 MHz, ppm, CDCl3): d 7.09, 6.74 (4H,
171–174 C (from ethyl ether), yield 30% from 21a. H
NMR (free base, 400 MHz, ppm, CDCl3): d 6.93 (1H, d,
J=7.7 Hz, aromatic H), 6.81 (1H, s, aromatic H), 6.73
(1H, d, J=6.6 Hz, aromatic H), 5.46 (1H, s, 5-H), 4.91
(1H, d, J=3.6 Hz, 12-H), 4.87 (1H, d, J=12.4 Hz,
OCH2), 4.46 (1H, d, J=12.4 Hz, OCH2), 3.65 (2H, s,
CH2N), 2.34 (6H, s, NCH3 ꢁ 2), 1.47 (3H, s, 15-CH3),
0.97 (3H, d, J=7.7 Hz, 13-CH3), 0.89 (3H, d, J=6.9 Hz,
14-CH3). IR (KBr, cmꢀ1): 1626, 1585, 1466, 1377, 1281,
1101, 1013, 980, 876, 825. Anal. calcd for C25H37NO6:
C, 67.07, H, 8.34, N 3.13, found: C, 66.68, H 8.37, N
3.20.
q, JAB=8.4 Hz, aromatic H), 5.42 (1H, s, 5-H), 4.79
(1H, d, J=3.4 Hz, 12-H), 4.71, 4.38 (2H, q,
JAB=11.9 Hz, OCH2 ), 1.39 (3H, s, 15-CH3), 0.88 (3H,
d, J=5.9 Hz, 13-CH3), 0.83 (3H, d, J=7.3 Hz, 14-CH3).
Anal. calcd for C22H30O6: C, 67.67, H, 7.74, found: C,
68.02, H 7.97.
Its epimer: 12ꢁ-dihydroartemisinyl p-hydroxybenzyl ether.
White crystal, mp 146–148 ꢂC (from ethyl acetate–pet-
1
roleum ether), yield: 4% from 2. H NMR (400 MHz,
ppm, CDCl3): d 7.18, 6.78 (4H, q, JAB=8.4 Hz, aro-
matic H), 5.42 (1H, s, 5-H), 4.85, 4.52 (2H, q,
JAB=11.9 Hz, OCH2 ), 4.48 (1H, d, J=9.2 Hz, 12-H),
1.40(3H, s, 15-CH ), 0.88 (3H, d, J=5.9 Hz, 13-CH3),
3
0.80 (3H, d, J=7.1 Hz, 14-CH3). Anal. calcd for
C22H30O6: C, 67.67, H 7.74, found: C, 67.93, H 7.85.
30 -Hydroxy-40 -diethylaminomethyl-benzyl 12-ꢀ-dihy-
droartemisinyl ether oxalate (17b). White crystal, mp
148–150 ꢂC (from acetone–THF), yield 50% from 21a.
1H NMR (400 MHz, ppm, D2O): d 7.42 (1H, m, aro-
matic H), 6.98 (2H, d, J=8.3 Hz, aromatic H), 5.39
(1H, s, 5-H), 4.90(1H, d, J=3.7 Hz, 12-H), 4.71 (1H, d,
J=12.5 Hz, OCH2 ), 4.58 (1H, d, J=12.5 Hz, OCH2),
4.32 (2H, s, ArCH2N), 3.21 (4H, m, NCH2CH3 ꢁ 2),
1.42 (3H, s, 15-CH3), 1.33 (6H, m, CH2CH3 ꢁ 2), 0.93
12ꢀ - Dihydroartemisinyl m - hydroxy - ꢁ - methyl - benzyl
ether (21c, R0=CH3). White crystal, mp 144–145 ꢂC
(from ethyl acetate–petroleum ether), yield: 63% from

Y. Li et al. / Bioorg. Med. Chem. 11 (2003) 4363–4368
4367
(3H, d, J=6.2 Hz, 13-CH3), 0.90 (3H, d, J=3.5 Hz, 14-
CH3). 13C NMR (400 MHz, ppm, DMSO-d6): d 9.72
(q), 12.99 (q), 20.26 (q), 24.14 (t), 24.34 (t), 25.72 (q),
30.59 (d), 34.12 (t), 36.07 (t), 36.70 (t), 38.91 (d), 43.81
(d), 46.04 (t), 52.04 (t), 52.05 (d), 68.72 (t), 80.41 (s),
86.95 (d), 100.36 (d), 103.23 (s), 113.81 (d), 117.36 (d),
117.92 (s), 130.59 (d), 140.06 (s), 156.62 (s), 164.23
(s).30,31 Anal. calcd for C29H43NO10: C, 61.58, H, 7.66,
N, 2.48, found: C, 61.68, H, 7.64, N, 2.29.
J=12.1 Hz, OCH2), 3.67 (2H, m, ArCH2N), 2.33 (6H, s,
NCH3 ꢁ 2), 1.45 (3H, s, 15- CH3), 0.93 (3H, d, J=6.2 Hz,
13-CH3), 0.88 (3H, d, J=7.3 Hz, 14-CH3). IR (KBr,
cmꢀ1): 1614, 1495, 1467, 1375, 1263, 1103, 1030, 937, 881,
825. Anal. calcd for C25H37NO6: C, 67.09, H, 8.33, N,
3.13; found: C, 67.24, H, 8.31, N, 2.84.
40 -Hydroxy-30 -diethylaminomethyl-benzyl 12-ꢀ-dihy-
droartemisinyl ether oxalate (17g). White crystal, mp
152–154 ꢂC (from acetone), yield 41% from 21b. 1H
NMR (400 MHz, ppm, D2O): d 7.41 (1H, m, aromatic
H), 7.37 (1H, s, aromatic H), 6.98 (1H, d, J=8.3 Hz,
aromatic H), 5.52 (1H, s, 5-H), 4.90(1H, d, J=3.7 Hz,
12-H), 4.71 (1H, d, J=11.8 Hz, OCH2), 4.52 (1H, d,
J=11.8 Hz, OCH2), 4.32 (2H, q, J=13.3 Hz, ArCH2N),
3.21 (4H, m, NCH2CH3 ꢁ 2), 1.42 (3H, s, 15-CH3), 1.33
(6H, m, CH2CH3 ꢁ 2), 0.93 (3H, d, J=5.4 Hz, 13-CH3),
0.90 (3H, d, J=7.3 Hz, 14-CH3). Anal. calcd for
C29H43NO10: C, 61.59, H, 7.66, N, 2.48, found: C,
61.96, H, 8.01, N, 2.89.
30-Hydroxy-40-pyrrolidinomethyl-benzyl 12-ꢀ-dihydroar-
temisinyl ether oxalate (17c). White crystal, mp 165–
166 ꢂC (from ethyl acetate–acetone), yield 43% from
1
21a. H NMR (400 MHz, ppm, D2O): d 7.38 (1H, d,
J=6.7 Hz, aromatic H), 7.04 (2H, s, aromatic H), 5.42
(1H, s, 5-H), 4.90(1H, d, J=3.7 Hz, 12-H), 4.73 (1H, d,
J=12.5 Hz, OCH2), 4.64 (1H, d, J=12.5 Hz, OCH2),
4.38 (2H, s, ArCH2N), 3.53, 3.23 (2H, 2H, m, m,
CH2NCH2), 2.17, 2.02 (2H, 2H, m, m, CH2CH2), 1.43
(3H, s, 15-CH3), 0.97 (6H, m, 13-CH3, 14-CH3). Anal.
.
calcd for C29H40NO10 3=4H2O: C, 60.46, H, 7.26, N,
2.43, found: C, 60.46, H, 7.29, N, 2.34.
40-Hydroxy-30, 50-bis(pyrrolidinomethyl)-benzyl 12-ꢀ-di-
hydroartemisinyl ether fumarate (17h). White crystal,
mp 152–154 ꢂC (from ethyl alcohol–petroleum ether),
yield 57% from 21b. 1H NMR (free base, 100 MHz, ppm,
CDCl3): d 7.07 (1H, s, aromatic H), 6.80 (1H, s, aromatic
H), 5.14 (1H, s, 5-H), 4.67 (1H, d, J=3.8 Hz, 12-H), 4.41
(2H, q, J=12 Hz, OCH2), 3.85 (4H, s, ArCH2N ꢁ 2),
30-Hydroxy-40-morpholinomethyl-benzyl 12-ꢀ-dihydroar-
temisinyl ether oxalate (17d). White crystal, mp 163–
ꢂ
1
164 C (from acetone–ether), yield 68% from 21a. H
NMR (400 MHz, ppm, D2O): d 7.39 (1H, d, J=8.2 Hz,
aromatic H), 7.05 (2H, m, aromatic H), 5.41 (1H, s, 5-H),
4.95 (1H, d, J=3.4 Hz, 12-H), 4.73 (1H, J=12.6 Hz,
OCH2), 4.64 (1H, J=12.6 Hz, OCH2), 4.40(2H, s,
ArCH2N), 4.10, 3.82 (2H, 2H, d, d, J=13.2 Hz,
CH2OCH2), 3.49, 3.31 (2H, 2H, d, d, J=12.9 Hz,
CH2NCH2), 1.41 (3H, s, 15-CH3), 0.97 (3H, d, J=7.4 Hz,
13-CH3), 0.95 (3H, d, J=5.0Hz, 14-CH 3), 13C NMR
(400 MHz, ppm, DMSO-d6)30,31: d 13.00 (q), 20.26 (q),
24.15 (t), 24.33 (t), 25.71 (q), 30.58 (d), 34.11 (t), 36.06 (t),
36.70(d), 43.80(d), 51.38 (t), 52.04 (d), 55.38 (t), 64.12 (t),
68.67 (t), 80.41 (s), 86.95 (d), 100.37 (d), 103.24 (s), 113.79
(d), 116.47 (s), 117.42 (d), 131.58 (d), 140.53 (s), 156.33(s),
163.17(s).30,31 Anal. calcd for C29H41NO11: C, 60.09, H,
7.13, N, 2.42; found: C, 59.69, H, 7.09, N, 2.36.
2.60(8H, m, CH NCH2 ꢁ 2), 1.76 (8H, m, CH2CH2 ꢁ
2
2), 1.38 (3H, s, 15-CH3), 0.88 (6H, m, 13-CH3, 14-CH3).
Anal. calcd for C40H56N2O14: C, 60.90, H, 7.15, N, 3.55,
found: C, 60.82, H, 7.34, N, 3.77.
40-Hydroxy-30, 50-bis(morpholinomethyl)-benzyl 12-ꢀ-di-
hydroartemisinyl ether fumarate (17i). White crystal, mp
147–148 ꢂC (from acetone), yield 40% from 21b. 1H
NMR (400 MHz, D2O): d 7.42 (2H, s, aromatic H), 6.57
(2H, s, CH¼CH), 5.44 (1H, s, 5-H), 4.90(1H, d,
J=3.7 Hz, 12-H), 4.62 (2H, q, J=12 Hz, OCH2), 4.32
(4H, s, ArCH2N ꢁ 2), 3.92 (8H, m, CH2OCH2 ꢁ 2),
3.22 (8H, m, CH2NCH2 ꢁ 2), 1.40(3H, s, 15-CH 3), 0.92
(3H, d, J=5.7 Hz, 13-CH3), 0.90 (3H, d, J=7.3 Hz, 14-
CH3). Anal. calcd for C36H54N2O13: C, 59.82, H, 7.53.
N, 3.88, found: C, 60.21, H, 7.45, N, 3.73.
30-Hydroxy-40-t-butylmethylamino-benzyl 12-ꢀ-dihydroartem-
isinyl ether maleate (17e). White crystal, mp 161–162 ꢂC
(from acetone), yield 27% from 21a. 1H NMR
(400 MHz, ppm, CD3COCD3): d 7.37 (1H, d, J=7.7 Hz,
aromatic H), 7.04 (1H, s, aromatic H), 6.85 (1H, d,
J=7.8 Hz, aromatic H), 6.16 (2H, s, CH¼CH), 5.45
(1H, s, 5-H), 4.81 (1H, d, J=3.9 Hz, 12-H), 4.78 (1H,
J=12.5 Hz, OCH2), 4.43 (1H, J=12.6 Hz, OCH2), 4.31
(2H, s, ArCH2N), 1.58 (9H, s, C4H9), 1.34 (3H, m, 15-
CH3), 0.94 (6H, m, 13-CH3, 14-CH3). Anal. calcd for
C31H45NO10: C, 62.93, H, 7.67, N, 2.37, found: C,
62.66, H, 7.72, N, 2.18.
30-Hydroxy- 40-pyrrolidinomethyl-ꢁ-methyl-benzyl 12-ꢀ-
dihydroartemisinyl ether oxalate (17j). White crystal,
mp 157–158 ꢂC (from acetone–water), yield 38% from
1
21c. H NMR (400 MHz, ppm, D2O): d 7.35 (1H, m,
aromatic H), 6.95 (2H, m, aromatic H), 5.62 (1H, s, 5-
H), 4.62 (1H, m, OCHCH3), 4.33 (2H, d, J=9.0Hz,
ArCH2N), 3.50, 3.17 (2H, 2H, m, m, CH2NCH2), 2.14,
2.00 (2H, 2H, m, m, CH2CH2), 1.44 (3H, d, J=7.6 Hz,
OCHCH3), 1.41 (3H, s, 15-CH3), 0.95 (3H, d,
J=5.2 Hz, 13-CH3), 0.86 (3H, d, J=6.5 Hz, 14-CH3).
Anal. calcd for C30H43NO10: C, 62.38, H, 7.50. N, 2.42,
found: C, 62.33, H, 7.69, N, 2.35.
40 -Hydroxy-30 -dimethylaminomethyl-benzyl 12-ꢀ-dihy-
droartemisinyl ether maleate (17f). White crystal, mp
103–106 ꢂC (from ethyl acetate–petroleum ether), yield
33% from 21b. H NMR (free base, 400 MHz, ppm,
40 -Hydroxy-30 -dimethylaminomethyl-ꢁ -methyl-benzyl
12-ꢀ-dihydroartemisinyl ether oxalate (17k). White
crystal, mp 128–130 ꢂC (from ethyl acetate–acetone),
yield 48% from 21d. 1H NMR (free base, 400 MHz,
ppm, CDCl3): d 7.10(1H, m, aromatic H), 6.86 (1H, d,
1
CDCl3): d 7.13 (1H, d, J=8.1 Hz, aromatic H), 6.90
(1H, s, aromatic H), 6.80(1H, d, J=8.4 Hz, aromatic
H), 5.43 (1H, s, 5-H), 4.87 (1H, d, J=3.3 Hz, 12-H),
4.74 (1H, d, J=11.7 Hz, OCH2), 4.42 (1H, d,

4368
Y. Li et al. / Bioorg. Med. Chem. 11 (2003) 4363–4368
J=2.4 Hz, aromatic H), 6.75 (1H, m, aromatic H), 5.48
(1H, s, 5-H), 4.81 (1H, m, OCHCH3), 4.61 (1H, d,
J=3.7 Hz, 12-H), 3.60(2H, m, ArCH N), 2.30(6H, s,
NCH3 ꢁ 2), 1.44 (3H, s, 15-CH3), 1.39 (3H, d,
J=6.7 Hz, OCHCH3), 0.97 (3H, d, J=6.1 Hz, 13-CH3),
0.74 (3H, d, J=7.3 Hz, 14-CH3). IR (KBr, cmꢀ1): 3200–
2500, 1600, 1498, 1466, 1373, 1257, 1099, 987, 875.
Anal. calcd for C28H41NO10: C, 60.97, H, 7.49, N, 2.54;
found: C, 60.88, H, 7.82, N, 2.85.
References and Notes
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2
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40-Hydroxy-30,50-bis(diethylaminomethyl)-ꢁ-methyl-ben-
zyl-12-ꢀ-dihydro artemisinyl ether oxalate (17l). White
crystal, mp 136–138 ꢂC (from ethyl alcohol–petroleum
ether), yield 56% from 21d. 1H NMR (free base,
400 MHz, ppm, CDCl3): d 6.99 (2H, s, aromatic H),
5.49 (1H, s, 5-H), 4.83 (1H, q, J=6.4 Hz, OCHCH3),
4.64 (1H, d, J=3.4 Hz, 12-H), 3.66 (4H, ArCH2N ꢁ 2),
2.58 (8H, m, NCH2CH3 ꢁ 4), 1.44 (3H, s, 15-CH3), 1.40
(3H, d, J=6.7 Hz, OCHCH3), 1.24 (12H, t, J=6.5 Hz,
NCH2CH3 ꢁ 4), 0.96 (3H, d, J=6.4 Hz, 13-CH3), 0.75
(3H, d, J=7.2 Hz, 14-CH3). IR (KBr, cmꢀ1): 3300–
2500, 1608, 1470, 1375, 1227, 1099, 989, 875, 825. Anal.
calcd for C37H58N2O14: C, 58.87, H, 7.74. N, 3.71,
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40-Hydroxy-30-pyrrolidinomethyl-ꢁ-methyl-benzyl 12-ꢀ-
dihydroartemisinyl ether oxalate (17m). White crystal,
mp 160–162 ꢂC (from acetone–petroleum ether), yield
1
44% from 21d. H NMR (free base, 400 MHz, ppm,
CDCl3): d 7.10(1H, m, aromatic H), 6.90(1H, m, aro-
matic H), 6.78 (1H, t, J=8.4 Hz, aromatic H), 5.50(1H,
s, 5-H), 4.80(1H, m, OC HCH3), 4.63 (1H, d, J=3.3 Hz,
12-H), 3.78 (2H, m, ArCH2N), 2.60(4H, m,
CH2NCH2), 1.84 (3H, OCHCH3), 1.46 (3H, s, 15-CH3),
1.39 (4H, m, CH2CH2), 0.97 (3H, d, J=6.4 Hz, 13-
CH3), 0.75 (3H, d, J=7.3 Hz, 14-CH3). IR (KBr, cmꢀ1):
3300–2500, 1600, 1498, 1462, 1257, 1099, 985, 875.
Anal. calcd for C30H43NO10: C, 62.38, H, 7.50. N, 2.42,
found: C, 62.49, H, 7.42, N, 2.52.
40-Hydroxy-30, 50-bis(piperidinomethyl)-ꢁ-methyl-benzyl
12-ꢀ-dihydro artemisinyl ether oxalate (17n). White
crystal, mp 104–106 ꢂC (from ethyl alcohol–petroleum
ether), yield 36% from 21d. 1H NMR (free base,
400 MHz, ppm, CDCl3): d 6.94 (2H, s, aromatic H),
5.49 (1H, s, 5-H), 4.80(1H, q, J=6.5 Hz, OCHCH3),
4.62 (1H, d, J=3.6 Hz, 12-H), 3.56 (4H, s, ArCH2N ꢁ
2), 2.40(8H, m, CH NCH2 ꢁ 2), 1.42–1.56 (12H, m,
2
CH2CH2CH2 ꢁ 2), 1.38 (3H, s, 15-CH3), 1.35 (3H, d,
J=6.0Hz, OCHC H3), 0.94 (3H, d, J=7.8 Hz, 13-CH3),
0.75 (3H, d, J=7.4 Hz, 14-CH3). IR (KBr, cmꢀ1): 3427,
2540, 1612, 1456, 1226, 1099, 989, 721. Anal. calcd for
C39H58N2O14: C, 60.14, H, 7.51, N, 3.60, found: C,
60.21, H, 7.41, N, 3.81.
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Acknowledgements
We thank the State Committee of Science and Technol-
ogy of China for financial support of this work (No. 85-
922-01-12). We also thank Dr. Reto Brun in Swiss
Tropical Institute for determination of antimalarial
activity in vitro.
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