Synthesis and biological evaluation of analogues of cryptolepine, an alkaloid isolated from the suriname rainforest

Article abstract of DOI:10.1021/np990035g

Bioassay-guided fractionation of an extract of a mixture of Microphilis guyanensis and Genipa americana collected in the rainforest of Suriname yielded the known alkaloid cryptolepine (2) as the major active compound in a yeast bioassay for potential DNA-damaging agents; the same compound was later reisolated from M. guyanensis. The structure of cryptolepine was identified unambiguously by spectral data and by its total synthesis. Several cryptolepine derivatives (3-29, 32-41) were synthesized based on modifications of the C-2, N-5, N-10, and C-11 positions. Two cryptolepine dimers (30, 31) were also prepared. The structure modifications did not result in compounds with a higher potency than the parent compound cryptolepine in the yeast assay system, although some derivatives did show significant activity. Selected compounds (6, 7, 17, 22, 23, 26, and 27) were also tested for cytotoxicity in mammalian cell culture, and two compounds showed significant cytotoxic activity.

Full text of DOI:10.1021/np990035g

976
J . Nat. Prod. 1999, 62, 976-983
Syn th esis a n d Biologica l Eva lu a tion of An a logu es of Cr yp tolep in e, a n Alk a loid
Isola ted fr om th e Su r in a m e Ra in for est1
Shu-Wei Yang,† Maged Abdel-Kader,† Stan Malone,‡ Marga C. M. Werkhoven,§ J an H. Wisse, Isia Bursuker,|
Kim Neddermann,| Craig Fairchild,∇ Carmen Raventos-Suarez,∇ Ana T. Menendez,∇ Kate Lane,∇ and
David G. I. Kingston*,†
Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212,
Conservation International Suriname, Burenstrasse 7, Paramaribo, Suriname, The National Herbarium of Suriname,
P.O. Box 9212, Paramaribo, Suriname, Bedrijf Geneesmiddelen Voorziening Suriname, Commissaris Roblesweg 156,
Geyersluit, Suriname, Bristol-Myers Squibb Pharmaceutical Research Institute, 5 Research Parkway,
Wallingford, Connecticut 06492-7660, and Bristol-Myers Squibb Pharmaceutical Research Institute, P.O. Box 4000,
Princeton, New J ersey 05843
Received February 1, 1999
Bioassay-guided fractionation of an extract of a mixture of Microphilis guyanensis and Genipa americana
collected in the rainforest of Suriname yielded the known alkaloid cryptolepine (2) as the major active
compound in a yeast bioassay for potential DNA-damaging agents; the same compound was later reisolated
from M. guyanensis. The structure of cryptolepine was identified unambiguously by spectral data and by
its total synthesis. Several cryptolepine derivatives (3-29, 32-41) were synthesized based on modifications
of the C-2, N-5, N-10, and C-11 positions. Two cryptolepine dimers (30, 31) were also prepared. The
structure modifications did not result in compounds with a higher potency than the parent compound
cryptolepine in the yeast assay system, although some derivatives did show significant activity. Selected
compounds (6, 7, 17, 22, 23, 26, and 27) were also tested for cytotoxicity in mammalian cell culture, and
two compounds showed significant cytotoxic activity.
In continuation of our search for anticancer and other
bioactive agents from the Suriname rainforest,2 an extract
of a mixture of Microphilis guyanensis (A. DC) Pierre
(Sapotaceae) and Genipa americana L. (Rubiaceae) col-
lected on an ethnobotanical basis near Asindopo village in
the rain forest of Suriname3 was found to show strong but
nonselective activity in a yeast bioassay utilizing mutants
1138, 1140, and 1353 of the yeast Saccharomyces cerevi-
siae.4 In this assay system, general DNA-damaging agents
and antifungal agents show activity against all three
strains.2 This extract was thus selected for further inves-
tigation.
instead of its hydrochloride 1. The free base form of
compound 1 was identified as cryptolepine (2) by compari-
son of its H NMR data with literature data. Compound 1
was active in the 1138, 1140, and 1353 yeast strains, with
IC12 values of 0.6 µg/mL in each strain. It was also cytotoxic
to the M109 cell line, with an IC50 of <1 µg/mL.
Following the completion of this work an extract of M.
guyanensis (A. DC) (Sapotaceae) was reinvestigated and
found to contain cryptolepine, thus implicating this plant
as the source of cryptolepine in the mixed extract.
Cryptolepine has previously been isolated from Cryptol-
epis triangulariz N. E. Br.,6 Cryptolepis sanguinolenta from
Africa,7 and Sida sp. (Malvaceae) from Sri Lanka.8 Most
recently it has been isolated as the antihyperglycemic
principle of C. sanguinolenta,9 and the introduction to this
paper provides a useful bibliography of previous work on
cryptolepine, including its antimicrobial, antibacterial,
antiinflammatory, antihypertensive, antipyretic, antimus-
carinic, antithrombotic, noradrenergic recepter antagonis-
tic, vasodilative, antimalarial, and antihyperglycemic bio-
logical activities. Cryptolepine belongs to the indoloquinoline
alkaloid family, a relatively rare group of alkaloids in
Nature, and interestingly its total synthesis was ac-
complished before its isolation from nature.10 Because of
its various interesting biological activities, several synthetic
pathways related to cryptolepine and its derivatives have
been established.11 Other examples of natural indoloquino-
lines include quindoline, hydroxycryptolepine, cryptohep-
tine, and cryptoquindoline,12 cryptospirolepine,13 neocryp-
tolepine,14 and isocryptolepine.15
1
Resu lts a n d Discu ssion
Isola tion Stu d ies. Bioassay-guided fractionation of the
extract was carried out using a combination of column
chromatography with Sephadex LH-20 and MCI gel to yield
compound 1 as the major active component. Once the salt
nature of 1 became clear it was obtained more efficiently
by an acid-base partition using methods described in the
literature,5 followed by further purification by chromatog-
raphy on LH-20.
The structure of compound 1 was assigned as cryptol-
epine hydrochloride by NMR techniques and HRFABMS,
and its anion was determined as chloride using negative-
ion FABMS (Cl- ) m/z 35, 37). The 1H and 13C NMR
resonances for 1 were assigned unambiguously by spectral
data including 1H-1H COSY, HMBC, HMQC, and ROESY
spectra, and are listed in the Experimental Section; most
NMR data are reported for the free base cryptolepine (2)
Syn th etic Stu d ies. Because of the promising biological
activity of cryptolepine in both our yeast assays and in the
M109 cytotoxicity assay, we decided to carry out a limited
study of the structure-activity relationships of this class
of compound. A similar study was also carried out by Bierer
and co-workers independently of this work.16 The com-
pounds prepared by Bierer et al. are, however, for the most
* To whom enquiries should be addressed. Tel.: (540) 231-6570. Fax:
(540) 231-7702. E-mail: dkingston@vt.edu.
† Virginia Polytechnic Institute and State University.
‡ Conservation International, Suriname.
§ National Herbarium of Suriname.
Bedrijf Geneesmiddelen Voorziening Suriname.
| Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford.
∇ Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton.
10.1021/np990035g CCC: $18.00
© 1999 American Chemical Society and American Society of Pharmacognosy
Published on Web 06/03/1999

Cryptolepine Analogues
J ournal of Natural Products, 1999, Vol. 62, No. 7 977
Sch em e 1
Sch em e 2
part different than those described in this work, and the
bioassays used are also different.
The total synthesis of 5-N-methylquindolinium salts was
achieved by the methods described in the literature (Scheme
1).9-11 Thus quindoline 11-carboxylic acid (3) was prepared
by condensation of isatin and indoxyl-1,3-diacetate in
aqueous KOH under argon,10,11 and decarboxylated by
heating at 300 °C to yield quindoline (4) in sublimed form.
5-N-Methylation of 4 could then be carried out in two
ways: treatment of quindoline mixed with iodomethane in
methanol in a tightly closed vial at 110 °C for 4 h gave the
iodide salt (5),10 while treatment with methyl triflate in
toluene at room temperature9 gave the triflate salt (6). The
5-N-ethyl-, 5-N-propyl-, and 5-N-butylquindolines (7, 8, and
9, respectively) were prepared by alkylation with iodoeth-
ane, propyl iodide, and butyl bromide, respectively, at high
temperatures in different solvents. Attempted alkylation
using isopropyl bromide and 1,4-dibromobutane failed to
produce quaternary salts.
Modification at the N-10 position was achieved by
treating quindoline 4 with base (BaO and KOH), followed
by treatment with the selected alkylating agent (methyl,
ethyl, or propyl iodide, butyl bromide, allyl bromide, or
benzyl bromide), as described for the synthesis of 10-N-
methylquindoline (10),9 to yield compounds 10-15 (Scheme
2). 10-N-Acetylquindoline (16) was obtained from treatment
of quindoline (4) with acetic anhydride in pyridine. Since
methyl substitution on N-5 is the most effective substitu-
tion for biological activity in our assays, all of the 10-N-
alkyl quindolines obtained were converted to their 5-N-
methyl derivatives (17-21) by treatment with methyl
triflate. 5-N-Methyl-10-N-acetylquindolinium chloride (22)
was prepared by acetylation of 1 in the usual way.
For modifications at the 11 position (Scheme 3), quin-
doline 11-carboxylic acid (3) was methylated to its methyl
ester 23 with diazomethane, and 23 was reduced under
moderate conditions to the alcohol 24 with lithium alumi-
num hydride (LAH). The use of excess LAH and a longer
duration of reflux gave 11-methylquindoline (26) as the
only reduced product, while oxidation of 24 with pyridinium
dichromate (PDC) gave aldehyde 25. The presence of the
11-CH2OH and 10-NH groups of compound 24 allowed the
formation of cyclic carbamate 27 by the use of 1,1′-carbonyl
diimidazole (CDI) and imidazole in CH2Cl2.
Further transformations of these 11-substituted com-
pounds yielded additional products. Thus two dimers were

978 J ournal of Natural Products, 1999, Vol. 62, No. 7
Yang et al.
Sch em e 3
Sch em e 4
prepared through acid chloride 28; the dimeric diester 30
and the cyclic dimer 31. Diester 30 was prepared from
mono-ester 29, which itself was formed by treatment of acid
chloride 28 with ethylene glycol. A second acylation of 29
with 3 under more vigorous conditions gave 30. The dimer
31 was made by self-condensation between two acid
chlorides (28), as previously described.11a Finally in this
group an aminopropanediol side chain was attached at the
C-11 position of 25 through reductive coupling of 2-amino-
2-methyl-1,3-propanediol to give compound 32; similar
derivatives of polycyclic aromatic hydrocarbons have shown
improved anticancer activity.17
2-Bromoquindoline-11-carboxylic acid (33) was prepared
through condensation of 5-bromoisatin and indoxyl-1,3-
diacetate. The decarboxylation of 33 at 300 °C led to both
decarboxylation and debromination, to generate quindoline
(4) as the major product. 11-Carboxylquindoline was found
to be the major product when the temperature was
controlled at 270-280 °C for 1 h, indicating that debromi-
nation occurs before decarboxylation. 2-Bromoquindoline
could thus not be obtained in acceptable yield by this route.
Some 2-bromo-11-substituted quindolines were prepared,
including the methyl ester 34, the acid halide 35, and the
amide 36. Bioassay of compound 34 gave an IC12 value of
100 µg/mL in the 1138 strain, which was worse than that
of compound 23 lacking the bromine substitution. This
indicated that the 2-bromo substitution decreases activity,
and the preparation of other derivatives of 2-bromo-
substituted quindolines was not pursued.
A final modification was the substitution of an oxygen
atom for the nitrogen atom at the 10-position. The ring
system of the target compound 40 has been synthesized
previously.18 We modified the route to improve the yield,
shown in Scheme 4; a similar strategy has been applied to
the synthesis of quindoline (4) from quinolone.11c Interme-
diates 37 and 3818c and target compound 40 were synthe-
sized. Finally, 5-N-methylation was achieved by refluxing
a mixture of compound 40, MeI and MeOH in the presence
of NaOMe. Compound 39, in which the 11-chloro substitu-
ent is converted to an 11-iodo substituent, was obtained
as the major product when 5-N-methylation of compound
38 was attempted under the same conditions used for
compound 41. Presumably iodide ion generated from reac-
tion of MeI with methoxide acts as a nucleophile to displace
the 11-chloro substituent, and N-methylation is inhibited
by the electron-withdrawing nature of the halo substituent.
Biologica l Stu d ies. The bioassay results are shown in
Table 1; most of the compounds were tested only in the
1138 yeast strain, so these results will be discussed first.
The initial conclusion is that methylation at the 5-N-
position is critical for activity. Thus quindoline (4) has an
IC12 of 150 µg/mL, but its 5-N-methyl derivative 1 has an
IC12 of 0.6 µg/mL. Replacement of the methyl group at the
5-N position with an ethyl group decreases the activity
significantly, and the activity decreases further as the
length of the N-5 alkyl chain increases. Thus the methyl,

Cryptolepine Analogues
J ournal of Natural Products, 1999, Vol. 62, No. 7 979
Ta ble 1. Bioactivity of Cryptolepine Analogsa
pound 22) gives a product which is as active as the
N-methyl analogue 17 (IC12 5 µg/mL), suggesting that the
N-acetyl analogue 22 may be partially hydrolyzed to 1.
Substitution at C-11 with the polar electron-withdrawing
groups COOH and CHO, compounds 3 and 25, leads to
greatly reduced activity (IC12 > 400 µg/mL in each case).
However, the activity is reduced by a lesser amount when
the C-11 substituent is carbomethoxy, hydroxymethyl, or
methyl (compounds 23, 24, and 26, with IC12 values of 40,
125, and 50 µg/mL, respectively). These results indicate
that the polarity and electron withdrawing characteristics
of C-11-substituted groups may affect the activity.
Replacement of N-10 by an oxygen atom (compounds 38-
41) caused the loss of activity, with IC12 values g400 µg/
mL. Finally, both dimers 30 and 31 were inactive at 400
µg/mL, as was compound 32 with the 2-amino-2-methyl-
1,3-propanediol side chain.
Selected analogues 6, 7, 17, 22, 23, 26, and 27 were
tested for cytotoxicity to the M109 Madison lung carcinoma
cell culture. The most active compounds were cryptolepine
hydrotriflate (6) and the N-acetyl derivative 22. As noted
above, the activity of 22 may be due to a ready hydrolysis
to the free base form. Compounds 6 and 22 were also tested
in a panel of 25 cell lines; both compounds gave similar
patterns, with the cell lines OVCAR-3 (IC50 0.5 µM) and
A431 (IC50 0.34 µM) being the most sensitive and M109
(IC50 5.6 µM) and MLF (IC50 4.9 µM) being the least
sensitive.
compound
IC12 (1138), µg/mL
M109 cytotoxicity, µM
1
2
4
0.6
0.5, 1.0, 5.0
150
5
1.5
6
<1
7
8
40
400
80
<50
16
17
18
19
20
21
22
23
24
26
27
34
36
41
5
80
125
90
200
5
40
125
50
<10
<1
<10
<10
<10
50
100
400
400
a
Compounds 3, 9, 15, 25, 29-32, and 37-40 had IC12 values
>400 µg/mL in the 1138 yeast strain.
Compounds 6 and 22 were also subjected to analysis of
their effect on cell cycle dependent growth disturbances.
The results showed a G1 cell cycle arrest and apoptosis in
A2780/p53wt cells at 5 × IC50. Higher concentrations
showed a dose-dependent increase in apoptosis. This effect
appears to be p53 dependent since A2780/mutp53 cells
showed no arrest in G1 and at 10 × IC50 showed a slow
cell cycle traverse with some arrest at G2/M. Apoptosis was
present only at 20 × IC50. These characteristics are typical
of DNA-damaging agents.
In conclusion, cryptolepine was isolated by bioassay-
guided fractionation of a mixture of two Surinamese plants,
and its source was subsequently identified as M. guyan-
ensis. Structure modification studies have shown that the
N-5 methyl substitution is critical for activity, and that
alkyl substitution on N-10 and replacement of 5-N-methyl
with larger alkyl groups causes reduction of activity.
Substitution on C-11 also led to decreased activity. The rest
of the modifications, including dimers, 2-bromo substitu-
tions, replacement of 10-NH with an oxygen, and addition
of a side chain at the C-11 position all cause total loss of
the yeast inhibitory activity. Besides cryptolepine hydro-
chloride itself (1), the most active compounds were 17 and
22.
Exp er im en ta l Section
Gen er a l Exp er im en ta l P r oced u r es. NMR spectra were
recorded in various deuterated solvents (CDCl3, DMSO-d6, and
CD3OD) on a Varian Unity 400 NMR instrument at 399.951
MHz for 1H and 100.578 MHz for 13C, using standard Varian
pulse sequence programs (J values are in Hz). LRMS were
taken on a VG 7070E-HF at VPI&SU. Exact mass measure-
ments were obtained at the Nebraska Center for Mass
Spectrometry. Other conditions were as previously described.2
All chemicals were purchased from Sigma or Aldrich and were
used without further purification.
ethyl, propyl, and butyl analogues 1, 7-9 gave IC12 values
of 0.6, 40, 400, and >400 µg/mL in the 1138 assay.
Methylation at the N-10 position also causes a slight
decrease in activity (compare 1 with IC12 0.6 µg/mL and
17 with IC12 5 µg/mL). Increasing the size of the 10-
substituent causes further loss of activity, as indicated by
a comparison of 18, 19, and 20 (IC12 80, 125, and 90 µg/
mL, respectively). On the other hand, N-acetylation (com-
P la n t Ma ter ia l. The plants M. guyanensis (A. DC) Pierre
(Sapotaceae) and Genipa americana L. (Rubiaceae) were
collected near Asindopo Village, Suriname, as a part of an
effort to investigate plant mixtures as used by the tribal

980 J ournal of Natural Products, 1999, Vol. 62, No. 7
Yang et al.
healers; M. guyanensis was also collected as a single sample.
Voucher specimens of the plants are located in the National
Herbarium of Suriname, Paramaribo, Suriname. The mixed
plants were dried, ground, and extracted with EtOAc followed
by MeOH for 24 h each at BGVS, followed by separate
evaporation of each solvent in vacuo to give EtOAc and MeOH-
soluble fractions. The MeOH-soluble extract, coded as BGVS
M950167, was active in the yeast bioassays described earlier.2c
Isola tion a n d P u r ifica tion . Dried extract (500 mg) was
dissolved in MeOH (2 mL) and passed through a Sephadex
LH-20 column with elution with MeOH-EtOH (1:1). The
active fractions 2 and 3 were combined and dried (155 mg)
and then passed through a column of MCI gel eluted with H2O,
H2O-MeOH (1:1), and MeOH. The active and pure fractions
4-7, eluted with H2O-MeOH (1:1), were combined to give
cryptolepine hydrochloride (1) (3 mg). Cryptolepine hydrochlo-
ride was also isolated by an acid-base partition as previously
described.19
(s, 1H, H-11), 8.36 (d, J ) 7.6, 1H), 8.31 (d, J ) 8.8, 1H), 8.26
(d, J ) 8.8, 1H), 8.11 (t, J ) 8.0, 1H), 8.04 (t, J ) 8.0, 1H),
7.86 (t, J ) 7.6, 1H), 7.84 (d, J ) 8.8, 1H, H-9), 7.48 (t, J )
8.0, 1H, H-7), 5.50 (q, J ) 7.6, 2H, -CH2-), 2.01 (t, J ) 7.6,
1
3H, -CH3); H NMR (CD3OD) δ 9.18 (s, 1H, H-11), 8.70 (d, J
) 8.8, 1H, H-4), 8.62 (d, J ) 8.8, 1H, H-6), 8.51 (d, J ) 8.4,
1H, H-1), 8.20 (td, J ) 8.0, 1.2, 1H, H-3), 7.95 (m, 2H, H-2
and H-8), 7.84 (d, J ) 8.4, 1H, H-9), 7.59 (td, J ) 8.0, 1.2, 1H,
H-7), 5.62 (q, J ) 7.6, 2H, -CH2-), 1.91 (t, J ) 7.6, 3H, -CH3);
EIMS m/z 218 [M - I - Et]+; FABMS 247 [M - I]+, 219.
5-N-P r op ylqu in d olin iu m Iod id e (8). Quindoline (4, 15
mg) was mixed with excess propyl iodide (100 µL) and DMF
(200 µL) and heated at 150 °C for 24 h in a closed vial. The
solvent was removed under high vacuum, and the product
isolated using an alumina column as described for compound
1
7 to give compound 8 (5 mg) in the CH2Cl2-MeOH eluent. H
NMR (CD3OD) δ 9.18 (s, 1H, H-11), 8.69 (d, J ) 9.2, 1H, H-4),
8.50 (d, J ) 8.4, 1H, H-6), 8.49 (d, J ) 8.4, 1H, H-1), 8.19 (td,
J ) 8.4, 1.2, 1H, H-3), 7.96-7.91 (m, 2H, H-2 and H-8), 7.82
(d, J ) 8.4, 1H, H-9), 7.59 (td, J ) 8.4, 1.2, 1H, H-7), 5.51 (t,
J ) 7.6, 2H, -CH2-), 2.30 (sextet, J ) 7.6, 2H, -CH2-), 1.34
(t, J ) 7.6, 3H, -CH3); EIMS m/z 260 [M - HI]+, 218 [M -
PrI]+; HREIMS m/z 260.1299 (calcd for C18H17N2, 260.1313).
5-N-Bu tylqu in d olin iu m Hyd r obr om id e (9). Treatment
of quindoline (4, 23 mg) with butyl bromide as described for
compound 8 gave compound 9 (7 mg). 1H NMR (CD3OD) δ 9.09
(s, 1H, H-11), 8.58 (d, J ) 9.2, 1H, H-4), 8.42 (d, J ) 8.4, 2H,
H-1 and H-6), 8.14 (td, J ) 8.0, 1.6, 1H, H-3), 7.89 (td, J )
8.4, 1.6, 2H, H-2 and H-8), 7.77 (d, J ) 8.4, 1H, H-9), 7.54 (t,
J ) 8.4, 1H, H-7), 5.45 (t, J ) 7.6, 2H, -CH2-), 2.15 (quintet,
J ) 7.6, 2H, -CH2-), 1.75 (sextet, J ) 7.6, 2H, -CH2-), 1.11
(t, J ) 7.6, 3H, -CH3); 13C NMR (MeOD) δ 147.6 (s), 138.5 (s),
136.3 (s), 135.3 (d), 135.0 (s), 134.2 (d), 131.3 (d), 128.4 (d),
128.1 (s), 126.4 (d), 125.9 (d), 123.3 (d), 118.1 (d), 114.5 (d),
114.3 (s), 52.8 (t), 31.4 (t), 20.9 (t), 14.2 (q); EIMS m/z 274 [M
- HBr]+, 218 [M - BuBr]+, 190, 88; HREIMS m/z 274.1472
(calcd for C19H19N2, 274.1470).
Subsequent investigation of an extract of M. guyanensis
(BGVS M950147) using the same methods described above led
to the isolation of cryptolepine from this plant alone.
Cr yp tolep in e Hyd r och lor id e (5-N-Meth ylqu in d olin i-
u m Ch lor id e) (1). 1H NMR (CD3OD) δ 9.14 (s, 1H, H-11),
8.76 (d, J ) 8.4, 1H, H-6), 8.67 (d, J ) 9.6, 1H, H-4), 8.49 (d,
J ) 8.3, 1H, H-1), 8.18 (t, J ) 7.9, 1H, H-3), 7.93-7.95 (m,
2H, H-2 and H-8), 7.83 (d, J ) 8.6, 1H, H-9), 7.56 (td, J ) 8.0,
0.8, 1H, H-7);13C NMR (CD3OD) δ 147.5 (s, C-9a), 139.7 (s,
C-5a), 137.2 (s, C-4a), 135.4 (d, C-8), 134.0 (d, C-3), 131.2 (d,
C-1), 128.5 (d, C-2), 128.5 (s, C-11a), 128.1 (s, C-10a), 126.9
(d, C-6), 126.3 (d, C-11), 123.0 (d, C-7), 118.4 (d, C-4), 115.4
(s, C-5b), 114.4 (d, C-9), 40.4 (5-N-CH3); ROESY correlations,
H-1 and H-11, H-4 and 5-N-CH3, and H-6 and 5-N-CH3. NMR
1
assignments were based on H-1H COSY, HMQC, HMBC, and
ROESY; EIMS m/z 233 (22%, [M - Cl]+), 232 (53%, [M -
HCl]•+), HRFABMS m/z 233.1075 [M - Cl]+ (calcd. for C16H13N2,
233.1079).
Cr yp tolep in e (2). Treatment of 1 with ammonium hydrox-
1
ide gave compound 2 as a purple solid. The H NMR data of 2
10-N-Meth ylqu in d olin e (10). The method described in the
literature was used and summarized as below.9 Quindoline (4,
15 mg) mixed with BaO (45 mg) and KOH (15 mg) in acetone
(5 mL) was refluxed for 1 h. Excess iodomethane (60 µL) was
added to the cooled residue and the mixture refluxed for an
additional 4 h; the excess reagent was then removed in a
vacuum. The organic material was extracted with ether, dried
over MgSO4, and the solution evaporated to obtain compound
were consistent with literature data.19
Qu in d olin e-11-ca r boxylic Acid (3). Compound 3 (990 mg)
was prepared by treatment of isatin (685 mg) with indoxyl-
1,3-diacetate (1 g) in aqueous KOH (4.15 g/18.5 mL) under
argon at room temperature for 10 days and workup as
previously described.11a 1H NMR (DMSO-d6) δ 11.5 (s, 1H, 10-
NH), 9.07 (dd, J ) 7.6, 2.0, 1H), 8.37 (d, J ) 7.6, 1H), 8.27
(dd, J ) 8.4, 2.0, 1H), 7.77 (d, J ) 8.4, 1H), 7.75-7.66 (m,
3H), 7.34 (t, J ) 7.6, 1H); EIMS m/z 218 [M - CO2]+ (calcd for
1
10 (15 mg). H NMR (CDCl3) δ 8.58 (d, J ) 8.4, 1H), 8.36 (d,
J ) 9.2, 1H), 7.95 (d, J ) 8.4, 1H), 7.92 (s, 1H, H-11), 7.65 (m,
2H), 7.54 (t, J ) 8.4, 1H), 7.40 (d, J ) 8.8, 1H), 7.34 (t, J )
8.4, 1H), 3.86 (s, 3H, 10-N-CH3); EIMS m/z 232 [M]+, 217 [M
- CH3]+, 190, 89; HREIMS m/z 232.0993 (calcd for C16H12N2,
232.1000).
C
15H10N2, 218).
Qu in d olin e (4). Decarboxylation of compound 3 (1 g) was
carried out by heating a vial containing compound 3 in an oil
bath at 300 °C for 1.5 h.11a Quindoline (4, 790 mg) was obtained
as yellow crystals through sublimation on the vial walls (95%).
1H and 13C NMR data were consistent with the data in the
literature.9,20 EIMS: 218 [M]+, 190, 89; C15H10N2.
5-N-Meth ylqu in d olin iu m Hyd r oiod id e (5). Compound
5 was synthesized by treatment of quindoline (4) with io-
domethane in anhydrous MeOH at 110 °C.11 The 1H NMR
spectral data for 5 in CD3OD were indistinguishable from those
of compound 1.
5-N-Meth ylqu in d olin iu m Tr ifla te (6). Compound 6 was
obtained by treatment of quindoline (4, 19 mg) with excess
methyl triflate (30 µL) in anhydrous toluene (3 mL) under
argon for 24 h.9 Toluene was removed in vacuo, and the residue
was washed with ether. The dry yellow solid was identified
as compound 6 (18 mg). The 1H NMR spectral data for 5 in
CD3OD were indistinguishable from those of compound 1.
5-N-Eth ylqu in d olin iu m Iod id e (7). Compound 7 (10 mg)
was synthesized from the N-ethylation of quindoline (4, 20 mg)
using iodoethane (30 µL) in anhydrous EtOH (2 mL) in a
tightly closed vial at 140 °C for 4 h.10a The product 7 and
starting material 4 were obtained in a 1:1 ratio and were
separated by chromatography on an alumina column eluted
with CH2Cl2, then CH2Cl2-MeOH (10:1). Compound 7 was
obtained in the CH2Cl2-MeOH fraction, and quindoline (4)
was recovered in the CH2Cl2 fraction. 1H NMR (CDCl3) δ 9.50
10-N-Eth ylqu in d olin e (11). Using iodoethane as alkylat-
ing agent (30 µL), compound 11 (5 mg, 95% yield) was
synthesized using the methods described for compound 10. 1H
NMR (CDCl3) δ 8.65 (d, J ) 8.0, 1H), 8.40 (d, J ) 7.9, 1H),
8.01 (s, 1H, H-11), 7.98 (d, J ) 8.3, 1H), 7.67 (m, 2H), 7.56 (t,
J ) 7.9, 1H), 7.44 (d, J ) 8.3, 1H), 7.35 (t, J ) 7.9, 1H), 4.42
(q, J ) 7.2, 2H, -CH2-), 1.49 (t, J ) 7.2, 3H, -CH3); EIMS
m/z 246 [M]+, 231 [M - CH3]+, 217 [M - Et]+, 190, 89;
HREIMS m/z 246.1150 (calcd for C17H14N2, 246.1157).
10-N-P r op ylqu in d olin e (12). Using propyl iodide as alky-
lating agent (30 µL), compound 12 (5 mg, 95% yield) was
synthesized using the methods described for compound 10. 1H
NMR (CDCl3) δ 8.62 (d, J ) 8.3, 1H), 8.38 (d, J ) 7.9, 1H),
7.99 (s, 1H, H-11), 7.97 (d, J ) 8.4, 1H), 7.66 (m, 2H), 7.56 (t,
J ) 7.9, 1H), 7.44 (d, J ) 8.3, 1H), 7.34 (t, J ) 7.9, 1H), 4.32
(t, J ) 7.2, 2H, -CH2-), 1.98 (sextet, J ) 7.2, 2H, -CH2-),
1.02 (t, J ) 7.2, 3H, -CH3); EIMS m/z 260 [M]+, 231 [M -
Et]+, 190; HREIMS m/z 260.1311 (calcd for C18H16N2, 260.1313).
10-N-Bu tylqu in d olin e (13). Using butyl bromide as alky-
lating agent (30 µL), compound 13 (5 mg, 95% yield) was
synthesized using the methods described for compound 10. 1H
NMR (CDCl3) δ 8.65 (d, J ) 8.3, 1H), 8.41 (d, J ) 7.9, 1H),
8.00 (s, 1H, H-11), 7.98 (d, J ) 8.4, 1H), 7.67 (m, 2H), 7.56 (t,
J ) 7.9, 1H), 7.44 (d, J ) 8.3, 1H), 7.35 (t, J ) 7.9, 1H), 4.36

Cryptolepine Analogues
J ournal of Natural Products, 1999, Vol. 62, No. 7 981
(t, J ) 7.2, 2H, -CH2-), 1.92 (quintet, J ) 7.2, 2H, -CH2-),
1.44 (sextet, J ) 7.2, 2H, -CH2-), 0.97 (t, J ) 7.2, 3H, -CH3);
EIMS m/z 274 [M]+, 231 [M - propyl]+, 217, 190, 89; HREIMS
m/z 274.1471 (calcd for C19H18N2, 274.1470).
(t, J ) 8.0, 1H, H-8), 7.66 (t, J ) 8.0, 1H, H-2), 7.60 (d, J )
8.4, 1H, H-9), 7.25 (t, J ) 8.0, 1H, H-7), 5.00 (s, 3H, 5-N-CH3),
4.58 (t, J ) 7.6, 2H, -CH2-), 1.88 (quintet, J ) 7.6, 2H,
-CH2-), 1.40 (sextet, J ) 7.6, 2H, -CH2-), 0.93 (t, 3H, -CH3);
EIMS m/z 289 [M - Tf]+, 275 [M - Tf - CH2]+, 245, 232 [M
- Tf - CH2 - propyl]+ (calcd for C20H21N2, 289).
5-N-Meth yl-10-N-a llylqu in d olin iu m Tr ifla te (21). Com-
pound 21 (0.6 mg) was synthesized from 14 (1.0 mg) using the
methods described for compound 17. 1H NMR (CD3OD) δ 9.33
(s, 1H, H-11), 8.82 (d, J ) 8.4, 1H, H-6), 8.69 (d, J ) 8.8, 1H,
H-4), 8.51 (d, J ) 8.0, 1H, H-1), 8.21 (td, J ) 8.8, 1.2, 1H,
H-3), 8.02 (td, J ) 8.0, 1.2, 1H, H-8), 7.97 (t, J ) 8.0, 1H, H-2),
7.92 (d, J ) 8.4, 1H, H-9), 7.62 (t, J ) 8.0, 1H, H-7), 6.15 (dddd,
J ) 17, 10, 5, 5, 1H, dCH-), 5.36 (brd, 5.0, 2H, -CH2-), 5.26
(d, J ) 10, 1H, dCH2), 5.11 (d, J ) 17, 1H, dCH2), (s, 3H,
5-N-CH3); EIMS m/z 273 [M - Tf]+, 258 [M - Tf - CH3]+, 231
[M - Tf - C3H6]+, 217 [M - Tf - C4H8]+ (calcd for C19H17N2,
273).
10-N-Allylqu in d olin e (14). Using allyl bromide as alky-
lating agent (30 µL), compound 14 (2 mg, 95% yield) was
synthesized using the methods described for compound 10. 1H
NMR (CDCl3) δ 8.64 (d, J ) 8.3, 1H), 8.42 (d, J ) 7.9, 1H),
7.98 (s, 1H, H-11), 7.97 (d, J ) 8.4, 1H), 7.67 (m, 2H), 7.56 (t,
J ) 7.6, 1H), 7.41 (d, J ) 8.3, 1H), 7.36 (t, J ) 7.6, 1H), 6.04
(dddd, J ) 17, 10, 5.0, 5.0, 1H, dCH-), 5.23 (brd, J ) 10, 1H,
dCH2), 5.10 (brd, J ) 17, 1H, dCH2), 4.97 (brd, J ) 5.0, 2H,
-CH2-); EIMS m/z 258 [M]+, 231 [M - CHdCH2]+, 217 [M -
CH2CHdCH2]+, 190.
10-N-Ben zylqu in d olin e (15). Using benzyl bromide as
alkylating agent (30 µL), compound 15 (4 mg, 95% yield) was
synthesized using the methods described for compound 10. 1H
NMR (CDCl3) δ 8.70 (d, J ) 8.3, 1H), 8.43 (d, J ) 7.9, 1H),
7.97 (s, 1H, H-11), 7.92 (d, J ) 8.0, 1H), 7.69 (t, J ) 7.6, 1H),
7.64 (t, J ) 8.3, 1H), 7.55 (t, J ) 7.6, 1H), 7.41 (d, J ) 8.2,
1H), 7.38-7.18 (m, 6H), 5.58 (s, 2H); EIMS m/z 308 [M]+, 216
[M - C7H8]+.
10-N-Acetylqu in d olin e (16). Quindoline (4, 8 mg) was
stirred with acetic anhydride (0.5 mL) and pyridine (0.5 mL)
at room temperature for 48 h. The product 16 (9 mg) was
obtained after removing excess reagent in vacuo, and passing
through an alumina column with elution with CH2Cl2. 1H NMR
(CD3OD) δ 9.00 (s, 1H, H-11), 8.50 (d, J ) 8.0, 1H), 8.27 (d, J
) 8.4, 1H), 8.13 (d, J ) 8.0, 1H), 7.99 (d, J ) 8.4, 1H), 7.75 (t,
J ) 7.6, 1H), 7.66 (t, J ) 7.6, 1H), 7.59 (t, J ) 7.6, 1H), 7.51
(t, J ) 7.6, 1H), 2.95 (s, 3H, -N-CO-CH3); 13C NMR (CD3OD)
δ 169.7 (s), 147.3 (s), 145.9 (s), 141.4 (s), 131.3 (s), 130.6 (d),
128.8 (d), 128.6 (d), 128.5 (d), 127.2 (s), 126.1 (d), 125.6 (s),
124.4 (d), 122.0 (d), 121.5 (d), 115.7 (d), 27.6 (q); FABMS m/z
261 [M + 1]+, 219; HREIMS m/z 260.0941 (calcd for C17H12N2O,
260.0950).
5-N-Met h yl-10-N-a cet ylq u in d olin iu m Ch lor id e (22).
Compound 1 (1 mg) was stirred with acetic anhydride (0.3 mL)
and pyridine (0.3 mL) for 24 h. The product 22 (1 mg) was
obtained after removing excess reagent in a vacuum, extraction
1
with 1 mL of MeOH-H2O (1:1), and drying. H NMR (CDCl3)
δ 10.02 (s, 1H, H-11), 8.77 (d, J ) 8.2, 1H), 8.59 (d, J ) 9.0,
1H), 8.40 (d, J ) 8.5, 1H), 8.27 (d, J ) 8.5, 1H), 8.20 (t, J )
8.5, 1H), 7.97 (t, J ) 8.2, 1H), 7.91 (t, J ) 7.6, 1H), 7.71 (t, J
) 8.2, 1H), 5.26 (s, 3H, 5-N-CH3), 3.16 (s, 3H, COCH3); FABMS
m/z 275 [M - Cl]+, 233 [M - Cl - COCH2]+, 218 [M - Cl -
Ac - CH3]+ (calcd for C18H15N2O, 275).
Meth yl Qu in d olin e-11-ca r boxyla te (23). Compound 3 (30
mg) was treated with excess diazomethane in ether, and the
mixture was stirred at room temperature for 3 h until the
starting material had dissolved. The solvent was removed, and
the product purified by chromatography on alumina with
1
elution by CH2Cl2 to give 23 (31 mg). H NMR (CDCl3) δ 9.73
(bs, 1H, 10-NH), 9.04 (dd, J ) 7.6, 2.4, 1H), 8.49 (d, J ) 7.6,
1H), 8.37 (dd, J ) 7.6, 2.0, 1H), 7.67 (m, 2H), 7.60 (td, J ) 7.9,
1.2, 1H,), 7.46 (d, J ) 8, 1H,), 7.35 (td, J ) 8, 1.2, 1H,), 4.16
(s, 3H, CH3); 13C NMR (CDCl3) δ 168.1 (s), 147.7 (s), 144.3 (s),
143.5 (s), 133.8 (s), 130.5 (d), 130.1 (d), 127.4 (d), 126.2 (d),
125.0 (d), 123.6 (s), 122.2 (d), 121.5 (s), 121.0 (d), 111.2 (d),
109.1 (s), 52.5 (q); HREIMS m/z 276.0895 (calcd for C17H12N2O2,
276.0899).
5,10-N,N-Dim eth ylqu in d olin iu m Tr ifla te (17). Com-
pound 10 (7.5 mg) in anhydrous toluene was treated with
excess methyl triflate under argon at room temperature for
24 h. The excess reagent was removed in a vacuum, and
compound 17 (7 mg) was obtained after washing with ether
1
and drying. H NMR (CD3OD) δ 9.36 (s, 1H, H-11), 8.81 (d, J
) 8.4, 1H, H-6), 8.69 (d, J ) 8.4, 1H, H-4), 8.53 (d, J ) 8.4,
1H, H-1), 8.21 (td, J ) 8.4, 0.8, 1H, H-3), 8.04 (t, J ) 8.0, 1H,
H-8), 7.97 (m, 2H, H-2 and H-9), 7.62 (t, J ) 8.4, 1H, H-7),
5.13 (s, 3H, 5-N-CH3), 4.21 (s, 3H, 10-N-CH3); 13C NMR (CD3-
OD) δ 148.3 (s), 135.8 (s), 135.6 (d), 134.0 (d), 133.3 (s), 131.2
(d), 130.2 (s), 128.7 (d), 127.9(s), 127.2 (d), 124.7 (d), 123.1 (d),
118.4 (d), 115.3 (s), 112.3 (d), 40.8 (q), 30.2 (q); EIMS m/z 247
[M - Tf]+, 233 [M - Tf - CH2]+ (calcd for C17H15N2, 247).
5-N-Meth yl-10-N-eth ylqu in d olin iu m Tr ifla te (18). Us-
ing compound 11 (2.5 mg) as starting material, compound 18
(2.3 mg) was synthesized using the methods described for
11-Hyd r oxym eth ylqu in d olin e (24). Methylquindoline-11-
carboxylate (23, 23 mg) was treated with LAH (30 mg) in THF
(5 mL) under reflux for 30 min. The reaction residue was
cooled, excess LAH allowed to settle out, and the supernatant
transferred to another flask and treated with EtOAc (25 mL)
and MeOH (1 mL). After filtration, the filtrate was evaporated
1
to give compound 24 (21 mg). H NMR (CDCl3) δ 8.45 (ddd, J
) 8.0, 0.8, 0.8, 1H), 8.27 (ddd, J ) 8.4, 0.8, 0.8, 1H), 8.20 (ddd,
J ) 8.0, 0.8, 0.8, 1H), 7.67 (td, J ) 8.0, 1.2, 1H), 7.63-7.54
1
1
(m, 3H), 7.28 (td, J ) 8.0, 1.2, 1H), 5.49 (s, 2H, CH2OH); H
compound 17. H NMR (CD3OD) δ 9.39 (s, 1H, H-11), 8.81 (d,
NMR (CD3OD) δ 8.56 (d, J ) 8.0, 1H), 8.52 (d, J ) 8.4, 1H),
8.35 (d, J ) 8.4, 1H), 8.05 (td, J ) 8.0, 1.2, 1H), 7.87 (t, J )
8.4, 2H), 7.81 (d, J ) 8.4, 1H), 7.48 (td, J ) 8.0, 1.2, 1H), 5.74
(s, 2H, -CH2OH); 13C NMR (CD3OD) δ 147.3 (s), 145.8 (s),
144.7 (s), 132.8 (s), 131.3 (d), 129.1 (d), 127.5 (d), 126.3 (d),
126.1 (s), 125.5 (s), 124.3 (d), 122.8 (d), 121.8 (s), 120.7 (d),
112.5 (d), 58.7 (t); EIMS m/z 248 [M]+, 230 [M - H2O]+, 218
[M - CH2O]+, 190 (calcd for C16H12N2O, 248).
J ) 8.0, 1H, H-6), 8.68 (d, J ) 8.8, 1H, H-4), 8.52 (d, J ) 8.4,
1H, H-1), 8.20 (td, J ) 8.0, 1.2, 1H, H-3), 8.03 (t, J ) 8.0, 1H,
H-8), 7.98 (m, 2H, H-2 and H-9), 7.61 (td, J ) 8.0, 0.8, 1H,
H-7), 5.12 (s, 3H, 5-N-CH3), 4.78 (q, J ) 7.2, 2H, -CH2-), 1.56
(t, J ) 7.2, 3H, -CH3); EIMS m/z 261 [M - Tf]+, 246 [M - Tf
- CH3]+ (calcd for C18H17N2, 261).
5-N-Meth yl-10-N-pr opylqu in dolin iu m Tr iflate (19). Com-
pound 19 (2.1 mg) was synthesized from 12 (2.5 mg) using the
methods described for compound 17. 1H NMR (CD3OD) δ 9.40
(s, 1H, H-11), 8.81 (d, J ) 8.4, 1H, H-6), 8.69 (d, J ) 8.8, 1H,
H-4), 8.53 (d, J ) 8.4, 1H, H-1), 8.20 (td, J ) 8.0, 1.6, 1H,
H-3), 8.03 (td, J ) 8, 1.2, 1H, H-8), 7.98 (m, 2H, H-2 and H-9),
7.61 (td, J ) 8.0, 1.6, 1H, H-7), 5.13 (s, 3H, N-CH3), 4.70 (t,
J ) 7.2, 2H, -CH2-), 2.04 (sextet, J ) 7.2, 7.2, 2H, -CH2-),
1.04 (t, J ) 7.2, 3H, -CH3); EIMS m/z 275 [M - Tf]+, 260 [M
- Tf - Me]+, 231 [M - Tf - Et]+ (calcd for C19H19N2, 275).
5-N-Meth yl-10-N-bu tylqu in d olin iu m Tr ifla te (20). Com-
pound 20 (2.0 mg) was synthesized from 13 (2.5 mg) using the
methods described for compound 17. 1H NMR (CD3OD) δ 9.19
(s, 1H, H-11), 8.59 (d, J ) 8.4, 1H, H-6), 8.42 (d, J ) 8.8, 1H,
H-4), 8.39 (d, J ) 8.8, 1H, H-1), 7.96 (t, J ) 8.0, 1H, H-3), 7.87
11-F or m ylqu in d olin e (25). Compound 24 (10 mg) was
treated with PDC (30 mg) in CH2Cl2 at room temperature for
12 h. The reaction mixture was passed through an alumina
column eluted with n-hexanes-EtOAc (3:1), and fractions
containing the desired compound were combined and dried to
give 25 (5 mg). Continued elution with MeOH gave recovered
starting material 24 (4 mg). 1H NMR (CDCl3-CD3OD, 10:1) δ
11.19 (s, 1H, COH), 8.67 (m, 1H), 8.44 (d, J ) 7.6, 1H, H-6),
8.32 (m, 1H), 7.68 (m, 2H, H-2 and H-3), 7.59 (t, J ) 8.0, 1H,
H-8), 7.50 (d, J ) 8.0, 1H, H-9), 7.34 (t, J ) 8.0, 1H, H-7); 13
C
NMR (CDCl3-CD3OD, 10:1) δ 191.6 (d), 148.3 (s), 144.4 (s),
143.3 (s), 133.1 (s), 131.0 (s), 130.8 (d), 129.8 (d), 127.8 (d),
126.6 (d), 124.1 (s), 122.2 (d), 121.6 (d), 120.4 (s), 119.9 (d),

982 J ournal of Natural Products, 1999, Vol. 62, No. 7
Yang et al.
111.7 (d); EIMS m/z 246 [M]+, 217 [M - COH]+; HREIMS m/z
246.0794 (calcd for C16H10N2O, 246.0793).
H2O (3 mL each). The EtOAc layer was dried (Na2SO4), and
the EtOAc was removed in a vacuum. The residue was purified
by PTLC on alumina and developed by CHCl3-MeOH (10:1).
The product band gave compound 32 (1.2 mg). 1H NMR (CD3-
OD) δ 8.45 (dd, J ) 7.6, 0.8, 1H), 8.38 (d, J ) 8.4, 1H), 8.21 (d,
J ) 8.4, 1H), 7.67 (td, J ) 8.0, 1.2, 1H), 7.64-7.58 (m, 2H),
7.54 (dd, J ) 8.0, 0.8, 1H), 7.29 (td, J ) 8.0, 1.2, 1H), 4.57 (s,
2H, -CH2-N), 3.68 (s, 4H, 2 × -CH2OH), 1.21 (s, 3H, -CH3);
13C NMR (CD3OD) δ 147.0 (s), 145.7 (s), 144.8 (s), 133.6 (s),
131.2 (d), 129.3 (d), 127.5 (d), 126.6 (s), 126.4 (d), 125.6 (s),
124.2 (d), 122.8 (d), 122.0 (s), 120.8 (d), 112.5 (d), 66.2 (t, 2C),
59.1 (s), 39.2 (t), 18.7 (q); FABMS m/z 336 [MH]+, 231 [M -
side chain]+ (calcd for C20H22N3O2, 336).
11-Meth ylqu in d olin e (26). Treatment of methylquindo-
line-11-carboxylate (23, 15 mg) with LAH (60 mg) in THF (5
mL) under reflux for 5 h, followed by chromatography on
alumina with CH2Cl2-MeOH (50:1) as eluent gave 26 (8 mg).
1H NMR (CDCl3-CD3OD, 10:1) δ 8.4 (d, J ) 8.8, 1H), 8.22 (d,
J ) 8.8, 1H), 7.98 (dd, J ) 9.2, 0.8, 1H), 7.613 (td, J ) 8.0,
1.2, 1H), 7.49 (td, J ) 8.0, 1.2, 1H), 7.33 (d, J ) 9.2, 1H), 7.16
(td, J ) 8.8, 1.2, 1H), 2.78 (s, 3H, -CH3); 13C NMR (CDCl3-
CD3OD, 10:1) δ 143.7 (s), 142.2 (s), 132.0 (s), 130.0 (d), 127.4
(d), 126.7 (d), 125.8 (s), 124.8 (d), 123.5 (s), 122.9 (d and s,
2C), 122.2 (d), 120.3 (s), 119.8 (d), 111.1 (d), 12.4 (q); EIMS
m/z 233 [MH]+, 232 [M]+; HREIMS m/z 232.1001 (calcd for
Meth yl 2-Br om oqu in d olin e-11-ca r boxyla te (34). 2-Bro-
moquindoline-11-carboxylic acid (33) (850 mg) was synthesized
in crude form as described for compound 3 from 5-bromoisatin
(685 mg) and indoxyl-1,3-diacetate (1 g) in aqueous KOH (4.15
g/18.5 mL) under argon at room temperature for 10 days. 13C
NMR (DMSO-d6) δ 168.2, 145.0, 143.5, 132.7, 132.0, 131.3,
130.9, 129.7, 129.3, 127.2, 126.5, 125.4, 124.1, 121.8, 120.8,
113.0; EIMS m/z 342, 340 [M]+, 324, 322 [M - H2O]+, 296,
294, 262, 244, 216, 215, 188 (calcd for C16H9N2O2Br, 342, 340).
Treatment of crude 33 (15 mg) with excess CH2N2 as described
C
16H12N2, 232.1000).
Ca r ba m a te 27. Compound 24 (3 mg) was treated with
excess 1,1′-carbonyldiimidazole (15 mg) and imidazole (1 mg)
in CH2Cl2 (3 mL) at room temperature for 24 h. The reaction
residue was purified by PTLC on alumina PTLC with develop-
ment by CH2Cl2. To give carbamate 27 (1.5 mg). 1H NMR
(CDCl3) δ 8.46 (d, J ) 8.0, 1H), 8.40 (d, J ) 8.4, 1H), 8.38 (d,
J ) 8.4, 1H), 7.80 (t, J ) 8.0, 1H), 7.75 (m, 2H), 7.69 (t, J )
8.0, 1H), 7.57 (t, J ) 8.0, 1H), 6.24 (s, 2H, -CH2O-); EIMS
m/z 274 [M]+, 230 [M - CO2]+ (calcd for C17H10N2O2, 274).
Qu in d olin e-11-ca r bon yl Ch lor id e (28). Quindoline-11-
carboxylic acid (5) was refluxed with SOCl2 for 2 h, and then
excess SOCl2 was removed in vacuo. The dried material was
used directly without further purification.
2-Hyd r oxyeth yl Qu in d olin e-11-ca r boxyla te (29). Quin-
doline-11-carbonyl chloride (28, 10 mg) was heated in ethylene
glycol (0.5 mL) at 110 °C for 1 h. The cooled reaction mixture
was filtered and the residue was washed with cold acetone to
give 29 (9 mg).1H NMR (CD3OD) δ 9.06 (d, J ) 8.5, 1H), 8.57
(d, J ) 8.1, 1H), 8.38 (d, J ) 8.6, 1H), 8.04 (t, J ) 7.4, 1H),
7.90 (t, J ) 8.3, 2H), 7.76 (d, J ) 8.3, 1H), 7.51 (t, J ) 7.6,
1H), 4.80 (t, J ) 4.7, 2H, -CO2CH2-), 4.08 (t, J ) 4.7, 2H,
-CH2OH); 13C NMR δ 165.3 (s), 147.8 (s), 141.5 (s), 136.3 (d),
136.2 (s), 134.9 (s), 132.3 (d), 129.7 (d), 127.4 (d), 124.7 (d),
123.4 (d), 122.2 (s), 121.8 (d), 115.2 (s), 114.3 (d), 69.2 (t), 60.7
(t); FABMS m/z 307 [MH]+ (calcd for C18H15N2O3, 307).
1,2-Eth a n ed iol 1,2-Bis(qu in d olin e-11-ca r boxyla te) (30).
A mixture of compound 29 (1.2 mg), compound 3 (3 mg), DCC
(15 mg), 4-pyrrolidinylpyridine (trace), and CH2Cl2 (2 mL) was
stirred at room temperature for 12 h. The excess of compound
3 was sparingly soluble in CH2Cl2, and was separated easily
by filtration. The reaction residue was purified by PTLC on
alumina with development by CH2Cl2 to give compound 30 (2
mg). 1H NMR (CDCl3) δ 9.87 (s, 2H, NH-10 and -10′), 9.12
(dd, J ) 8.8, 0.8, 2H), 8.44 (d, J ) 8.0, 2H), 8.33 (dd, J ) 8.0,
0.4, 2H), 7.62 (td, J ) 8.4, 1.2, 2H), 7.48-7.58 (m, 4H), 7.323
(t, J ) 8.0, 2H), 7.21 (d, J ) 8.0, 2H), 5.17 (s, 4H, -O-CH2-
CH2-O-); 13C NMR δ 167.4 (s), 147.9 (s), 144.3 (s), 143.6 (s),
139.8 (s), 133.7 (s), 130.6 (d), 130.3 (d), 127.6 (d), 126.2 (d),
124.7 (d), 123.6 (s), 122.1 (d), 121.5 (s), 121.1 (d), 111.2 (d),
63.5 (t); FABMS m/z 551 [MH]+, 307 (calcd for C34H23N4O4,
551).
Bisqu in d olin e (31). Compound 31 was prepared as previ-
ously described.11a 1H NMR (CDCl3) δ 9.05 (d, J ) 8.8, 2H),
8.65 (d, J ) 8.0, 2H), 8.48 (d, J ) 8.4, 2H), 7.87-7.74 (m, 8H),
7.38 (t, J ) 8.0, 2H); 13C NMR (CDCl3) δ 166.9 (s), 145.3 (s),
135.3 (s), 132.6 (d), 132.3 (d), 129.9 (s), 128.0 (d), 127.4 (d),
125.5 (s), 125.4 (d), 123.4 (s), 123.3 (s), 123.0 (d), 120.9 (d),
117.5 (s), 113.0 (d).
2-Meth yl-2-[11-(am in om eth yl)qu in dolin e]-1,3-pr opan e-
d iol (32). A mixture of aldehyde 25 (2 mg), anhydrous MgSO4
(40 mg), and 2-amino-2-methyl-1,3-propanediol (10 mg) was
dissolved in CH2Cl2-anhydrous MeOH (5:1, 2 mL) and the
mixture stirred at room temperature for 24 h. The reaction
residue was treated with an additional 4 mL of solvent (CH2-
Cl2-MeOH, 5:1), then filtered to remove MgSO4 and excess
amine. The filtrate was evaporated in vacuo, and the dried
residue was dissolved in 1.5 mL of MeOH. NaB(CN)H3 (15 mg)
was added, and the solution was stirred at room temperature
for 1 h. The MeOH in the reaction mixture was then removed
in vacuo, and the product was partitioned between EtOAc and
1
for 23 gave 34 (16 mg). H NMR (CDCl3) δ 9.75 (bs, 1H, 10-
NH), 9.23 (d, J ) 2, 1H), 8.45 (d, J ) 8, 1H), 8.20 (d, J ) 8.8,
1H), 7.73 (dd, J ) 8.8, 2.4, 1H), 7.63 (td, J ) 7.6, 1.2, 1H),
7.47 (d, J ) 8, 1H), 7.37 (td, J ) 8, 0.8, 1H), 4.19 (s, 3H,
COOCH3); EIMS m/z 356, 354 [MH]+, 324, 322 [M - HOCH3]+,
296, 294 [M - C2H4O2]+, 276, 244, 215 [M - HCO2CH3 - Br]+,
216, 188 (calcd for C17H12N2O2Br, 356, 354).
2-Br om oqu in d olin e-11-ca r bon yl Ch lor id e (35). Com-
pound 33 (10 mg) was mixed with SOCl2 (1 mL) and heated
at 70 °C for 2 h. After cooling to room temperature, excess
SOCl2 was quickly removed at room temperature in vacuo. The
residue was used directly without further purification.
2-Br om oqu in d olin e-11-ca r boxa m id e (36). Freshly pre-
pared 35 (12 mg) was treated with aqueous ammonia (37%,
0.5 mL). The dried residue containing compound 36 (8 mg)
was obtained after removal of excess ammonia and water in
1
vacuo, and washed with CHCl3 and MeOH. H NMR (DMSO-
d6) δ 11.54 (s, 1H, 10-NH), 8.50 and 8.26 (2 × bs, 2H,
-CONH2), 8.33 (m, 2H, H-1 and H-6), 8.15 (d, J ) 8.8, 1H,
H-4), 7.76 (dd, J ) 8.8, 2.3, 1H, H-3), 7.62 (m, 2H, H-8 and
H-9), 7.31 (t, J ) 7.2, 1H, H-7); 13C NMR (DMSO-d6) δ 166.6
(s), 146.9 (s), 144.7 (s), 141.6 (s), 135.3 (s), 131.3 (d), 130.5 (d),
129.0 (d), 126.3 (d), 123.7 (s), 121.4 (d), 120.4 (s), 120.0 (d),
119.6 (s), 118.7 (s), 112.1(d); EIMS m/z 341, 339 [M]+, 324,
322 [M - NH3], 296, 294 [M - CONH3]+, 215 [M - Br -
CONH3]+ (calcd for C16H10N3OBr, 341, 339).
Ben zofu r o[3,2-b]qu in olin -6(11H)on e (37). Compound 37
(220 mg) was synthesized by a literature procedure.18c 1H NMR
(DMSO-d6) δ 8.30 (d, J ) 8.0, 1H), 8.16 (d, J ) 8.0, 1H), 7.73
(d, J ) 8.4, 1H), 7.61 (d, J ) 8.0, 1H), 7.52 (t, J ) 8.4, 1H),
7.45 (t, J ) 8.4, 1H), 7.33 (t, J ) 8.4, 1H), 7.12 (t, J ) 8.0,
1H); 13C NMR (DMSO-d6) δ 162.0 (s), 156.3 (s), 147.2 (s), 138.9
(s), 128.8 (d), 128.3 (d), 127.9 (s), 125.2 (d), 125.1 (d), 124.2
(s), 122.6 (d), 121.9 (d), 119.8 (d), 117.5 (s), 112.5 (d); EIMS
m/z 235 [M]+ (calcd for C15H9NO2, 235).
11-Ch lor oben zofu r o[3,2-b]qu in olin e (38). Compound 38
(64 mg) was synthesized as previously described.18c 1H NMR
(CDCl3) δ 8.82 (dd, J ) 8.8, 1.2, 1H), 8.08 (dd, J ) 8.0, 1.2,
1H), 7.73 (dd, J ) 8.0, 1.6, 1H), 7.59 (td, J ) 8.0, 1.6, 1H),
7.26 (td, J ) 8.0, 1.6, 1H), 7.11 (td, J ) 8.0, 1.2, 1H), 6.78 (td,
J ) 8.0, 1.2, 1H), 6.71 (dd, J ) 8.0, 1.2, 1H); EIMS m/z 255,
253 [M]+, 218 [M - Cl]+, 190 (calcd for C15H8NOCl, 255, 253).
11-Iod oben zofu r o[3,2-b]qu in olin e (39). A mixture of
compound 38 (12 mg), iodomethane (0.7 mL), NaOMe (26 mg),
and anhydrous MeOH (2 mL) was refluxed for 24 h. Methanol
was removed in vacuo, and the residue was partitioned
between H2O and EtOAc. The EtOAc layer was dried, and the
resulting solid (14 mg) was collected as 39. 1H NMR (CD3OD)
δ 8.29 (d, J ) 8.0, 1H), 8.19 (d, J ) 8.4, 1H), 8.14 (d, J ) 8.0,
1H), 7.89 (d, J ) 8.4, 1H), 7.83 (t, J ) 8.0, 1H), 7.77 (m, 2H),
7.55 (t, J ) 8.0, 1H); EIMS: 345 [M]+, 218 [M - I]+, 180 (calcd
for C15H8NOI, 345).

Cryptolepine Analogues
J ournal of Natural Products, 1999, Vol. 62, No. 7 983
Ben zofu r o[3,2-b]qu in olin e (40). A mixture of compound
38 (30 mg) and 10% Pd/C (60 mg) in 4 mL of alcoholic KOH
(1N) under H2 was left at room temperature for 12 h. The Pd/C
was removed by filtration through Celite, and EtOH was
removed in vacuo. Acetone (1 mL) and distilled water (1 mL)
were added to the residue. The insoluble precipitate (20 mg)
was collected and identified as product 40 (78%). 1H NMR
(CDCl3) δ 8.39 (d, J ) 8.0), 8.30 (d, J ) 8.5), 8.16 (s), 7.97 (d,
J ) 8.0), 7.73 (ddd, J ) 8.0, 8.5, 1.0), 7.6 (m, 3H), 7.46 (ddd, J
) 8.0, 8.5, 1.0); 13C NMR (CDCl3) δ 159.6 (s), 147.9 (s), 147.5
(s), 146.1 (s), 130.9 (d), 129.3 (d), 128.0 (d), 127.9 (d), 127.4
(s), 126.1 (d), 123.6 (d), 122.9 (s), 122.2 (d), 114.5 (d), 112.2
(d); EIMS m/z 219 [M]+, 190 (calcd for C15H9NO, 219).
gratefully acknowledged. Mass spectra were obtained by Mr.
Kim Harich of Virginia Polytechnic Institute and State
University and the Midwest Center for Mass Spectroscopy in
the Department of Chemistry, University of Nebraska.
Refer en ces a n d Notes
(1) Biodiversity Conservation and Drug Discovery in Suriname. Part 5.
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K.; Kingston, D. G. I. J . Nat. Prod., 1997, 60, 1287-1293. (b) Abdel-
Kader, M. S.; Wisse, J . H.; Evans, R.; van der Werff, H.; Kingston,
D. G. I. J . Nat. Prod. 1997, 60, 1294-1297. (c) Abdel-Kader, M. S.;
Bahler, B. D.; Malone, S.; Werkhoven, M. C. M.; van Troon, F.; David,
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W.; Zhou, B.-N.; Wisse, J . H.; Evans, R.; van der Werff, H.; Miller, J .
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(3) The tribal healers of Suriname frequently use mixtures of plants in
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R. C.; Spitzer, T. D.; J ohnson, R. L.; Dunn, J .; Minick, D.; Martin, G.
E. J . Nat. Prod. 1993, 56, 653-670.
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1995, 39, 735-736.
(16) Bierer, D. E.; Dubenko, L. G.; Zhang, P.; Lu, Q.; Imbach, P. A.;
Garofalo, A. W.; Phuan, P.-W.; Fort, D. M.; Litvak, J .; Gerber, R. E.;
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5-N-Meth ylben zofu r o[3,2-b]qu in olin iu m iod id e (41). A
mixture of compound 40 (16 mg), iodomethane (0.5 mL),
NaOMe (20 mg), and anhydrous MeOH (2 mL) was refluxed
for 24 h.21 Ether was added, and the precipitate was obtained
through filtration. The solid was washed with CH2Cl2, col-
lected, and identified as compound 41 (12 mg). 1H NMR (CD3-
OD) δ 9.41 (s, 1H, H-11), 8.80 (dd, J ) 8.0, 1.2, 1H, H-6), 8.74
(d, J ) 8.8, 1H, H-4), 8.55 (dd, J ) 8.4, 1.6, 1H, H-1), 8.30 (td,
J ) 8.4, 1.6, 1H, H-3), 8.11 (td, J ) 8.4, 1.2, 1H, H-8), 8.03 (m,
2H, H-2 and H-9), 7.81 (td, J ) 8.4, 1.2, 1H, H-7), 5.10 (s, 3H,
5-N-CH3);13C NMR (CD3OD) δ 162.3 (s, C-9a), 149.5 (s, C-10a),
144.5 (s, C-5a), 138.9 (s, C-4a), 137.5 (d, C-8), 135.6 (d, C-3),
131.9 (d, C-1), 130.1 (d, C-2), 129.1 (s, C-11a), 127.5 (d, C-6),
127.2 (d, C-11), 126.9 (d, C-7), 119.1 (d, C-4), 117.8 (s, C-5b),
1
114.8 (d, C-5b), 41.4 (q, 5-N-CH3), assigned by H-1H COSY
and HMBC; FABMS m/z 234 [M - I]+; HRFABMS m/z
234.0914 [M - I]+ (calcd for C16H12NO, 234.0919).
Yea st Bioa ssa y. The manipulated yeast (1138, 1140, and
1353) assay was performed on a 9-well agar plate as previously
described.2c
Cytotoxicity Assa ys. Cytotoxicity bioassays were carried
out in the M109 cell line at Bristol-Myers Squibb Pharmaceu-
tical Research Institute by standard methods, with the results
indicated in Table 1. Compounds 6 and 22 were also tested in
a panel of 25 cell lines; both compounds gave similar patterns,
with the cell lines OVCAR-3 (IC50 0.5 µM) and A431 (IC50 0.34
µM) being the most sensitive and M109 (IC50 5.6 µM) and MLF
(IC50 4.9 µM) being the least sensitive.
In d u ction of Cell Cycle Dep en d en t Gr ow th Distu r -
ba n ces. Compounds 6 and 22 were subjected to analysis of
their effect on cell cycle dependent growth disturbances. FACS
analysis was done after 24 h exposure at increasing IC50
concentrations of these drugs. Results showed a G1 cell cycle
arrest and apoptosis in A2780/p53wt cells at 5 × IC50. Higher
concentrations showed a dose dependent increase in apoptosis.
This effect appears to be p53 dependent since A2780/mutp53
cells showed no arrest in G1 and at 10 × IC50 showed a slow
cell cycle traverse with some arrest at G2/M. Apoptosis was
present only at 20 × IC50. These characteristics are typical of
DNA damaging agents.
(18) (a) Reid, W.; Berg, A.; Schmidt, G. Chem. Ber. 1952, 85, 216-224.
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1379-1382.
(19) Ablordeppey, S. Y.; Hufford, C. D.; Borne, R. F.; Dwuma-Badu, D.
Planta Med. 1990, 56, 416-417.
(20) Spitzer, T. D.; Crouch, R. C.; Martin, G. E.; Sharaf, M. H. M.; Schiff,
P. L., J r.; Tackie, A. N.; Boye, G. L. J . Heterocycl. Chem. 1991, 28,
2065-2070.
Ack n ow led gm en t. This work was supported by an Inter-
national Collaborative Biodiversity Grant, number U01 TW/
CA-00313 from the Fogarty Center, NIH, and this support is
(21) Kaslow, C. E.; Moe, H. J . Org. Chem. 1960, 25, 1512-1516.
NP990035G