Synthesis and cytotoxic activity of benzo[a]pyrano[3,2-h] and [2,3-i]xanthone analogues of psorospermine, acronycine, and benzo[a]acronycine

Article abstract of DOI:10.1248/cpb.54.1113

Condensation of 2-hydroxy-1-naphthalenecarboxylic acid with phloroglucinol afforded 9,11-dihydroxy-12H-benzo[a]xanthen-12-one (6). Construction of an additional dimethylpyran ring onto this skeleton, by alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement, gave access to 6-hydroxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (12) and 5-hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (13), which were methylated into 6-methoxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (14) and 5-methoxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (15), respectively. Osmium tetroxide oxidation of 14 and 15 gave the corresponding (±)-cis-diols 16 and 17, which afforded the corresponding esters 18-21 upon acylation. Similarly, condensation of 2-hydroxy-1-naphthalenecarboxylic acid with 3,5-dimethoxyaniline gave 11-amino-9-methoxy-12H-benzo[a]xanthen-12- one (23) which was converted into 11-amino-9-hydroxy-12H-benzo[a]xanthen-12-one (24) upon treatment with hydrogen bromide in acetic acid. Alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement afforded 6-amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (25) and 5-amino-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (26). The new benzopyranoxanthone derivatives only displayed marginal antiproliferative activity when tested against L1210 and KB-3-1 cell lines. The only compounds found significantly active against L1210 cell line, 16 and 20, belong to the benzo[a]pyrano[3,2-h]xanthen-7-one series, which possess a pyran ring fused angularly onto the xanthone basic core.

Full text of DOI:10.1248/cpb.54.1113

August 2006
Chem. Pharm. Bull. 54(8) 1113—1118 (2006)
1113
Synthesis and Cytotoxic Activity of Benzo[a]pyrano[3,2-h] and
2,3-i]xanthone Analogues of Psorospermine, Acronycine, and
[
Benzo[a]acronycine
a
a
a
a
Chavalit SITTISOMBUT, Sabrina BOUTEFNOUCHET, Hanh TRINH VAN-DUFAT, Wen TIAN,
a
a
,a
b
b
Sylvie MICHEL, Michel KOCH, François TILLEQUIN,* Bruno PFEIFFER, and Alain PIERRÉ
a
Laboratoire de Pharmacognosie de l’Université René Descartes, U.M.R./C.N.R.S. n°8638, Faculté des Sciences
b
Pharmaceutiques et Biologiques; 4, Avenue de l’Observatoire, F-75006 Paris, France: and Institut de Recherches Servier,
Division Recherche Cancérologie; 125 Chemin de Ronde, 78290 Croissy sur Seine, France.
Received February 20, 2006; accepted April 14, 2006
Condensation of 2-hydroxy-1-naphthalenecarboxylic acid with phloroglucinol afforded 9,11-dihydroxy-12H-
benzo[a]xanthen-12-one (6). Construction of an additional dimethylpyran ring onto this skeleton, by alkylation
with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement, gave access to 6-hydroxy-3,3-dimethyl-
3
H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (12) and 5-hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xan-
then-6-one (13), which were methylated into 6-methoxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-
one (14) and 5-methoxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (15), respectively. Osmium
tetroxide oxidation of 14 and 15 gave the corresponding (ꢀ)-cis-diols 16 and 17, which afforded the correspon-
ding esters 18—21 upon acylation. Similarly, condensation of 2-hydroxy-1-naphthalenecarboxylic acid with 3,5-
dimethoxyaniline gave 11-amino-9-methoxy-12H-benzo[a]xanthen-12-one (23) which was converted into 11-
amino-9-hydroxy-12H-benzo[a]xanthen-12-one (24) upon treatment with hydrogen bromide in acetic acid. Alky-
lation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement afforded 6-amino-3,3-dimethyl-
3
H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (25) and 5-amino-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xan-
then-6-one (26). The new benzopyranoxanthone derivatives only displayed marginal antiproliferative activity
when tested against L1210 and KB-3-1 cell lines. The only compounds found significantly active against L1210
cell line, 16 and 20, belong to the benzo[a]pyrano[3,2-h]xanthen-7-one series, which possess a pyran ring fused
angularly onto the xanthone basic core.
Key words benzopyranoxanthone; acronycine; synthesis; cytotoxicity
Natural products play a major role in anticancer drug dis- group of DNA guanine residues by the carbocation resulting
covery as a unique source of original structures which can from the elimination of the ester leaving group at position 1
1
0—12)
provide models for future drug design. Relevant examples of the drug.
This mechanism is related to that implied
currently used in the clinic include teniposide and etoposide in the cytotoxic and antitumor properties of the natural fura-
derived from naturally occurring podophyllotoxin, taxotere noxanthone psorospermine (5), isolated from Psorospermum
1
3—15)
based on the structure of the yew diterpene paclitaxel, febrifugum.
Actually, psorospermine has been shown to
topotecan and irinotecan developed from camptothecin, and interact with DNA and to alkylate the N-7 of the guanine
1
6,17)
semisynthetic vinca alkaloids such as vinorelbine and vinflu- residues.
In a continuation of our studies on the structure
1)
18—24)
nine originating from the lead structure vinblastine. In this activity relationships in the acronycine series,
we
context, our group is interested in potential anticancer natural describe here the synthesis and biological activites of
product-like compounds including an acridone or xanthone
derived basic core and an additional fused dimethylpyran
ring. Indeed, the fused dimethylpyran system, which arises in
Nature from the condensation of a phenol with an active iso-
prene unit, appears as a privileged substructure present in nu-
merous bioactive compounds exemplified by the insecticide
2)
chromenes precocenes, the HIV-1 reverse transcriptase in-
3)
hibitors calanolides, and the antitumor acridone alkaloid
4)
acronycine (1). Based on this latter model, we recently pre-
pared the pentacyclic analogues benzo[a]acronycine (6-
methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[a]-
pyrano[3,2-h]acridin-7-one) (2) and and benzo[b]acronycine
(
6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]-
pyrano[3,2-h]acridin-7-one) (3), together with several series
of corresponding 1,2-dihydrodiol diesters, which displayed
significantly enhanced in vivo antitumor activity when com-
5—8)
pared to the parent alkaloid.
Such compounds are exem-
plified by cis-diacetate 4, developed under the code S23906-
9)
1
, which is currently undergoing phase I clinical trials. The
mechanism of its action implies alkylation of the 2-amino
Chart 1
∗
To whom correspondence should be addressed. e-mail: francois.tillequin@univ-parsi5.fr
© 2006 Pharmaceutical Society of Japan

1
114
Vol. 54, No. 8
pentacyclic xanthone isosters and analogues of benzo[a]- then-6-one (15), upon treatment with dimethylsulfate in the
acronycine, in the benzo[a]pyrano[3,2-h] and [2,3-i]xan- presence of sodium hydride. In contrast, Claisen rearrange-
thone series.
ment of the methoxy ether 11 under similar conditions
exclusively gave 6-methoxy-3,3-dimethyl-3H,7H-benzo[a]-
pyrano[3,2-h]xanthen-7-one (14), with the pyran ring angu-
Chemistry
Construction of the tetracyclic 9,11-dihydroxy-12H- larly fused onto the xanthone tricyclic system, most probably
benzo[a]xanthen-12-one (6) basic skeleton was achieved by due to the increased steric hindrance of the methoxy group at
condensation of 2-hydroxy-1-naphthalenecarboxylic acid (7) 5-position of 11, when compared with the chelated hydroxy
with phloroglucinol (8) in the presence of zinc chloride and group of 10. The mode of fusion of the newly formed di-
25,26)
phosphoryl chloride.
Chelation of the 11-hydroxy group methylpyran ring onto the xanthone basic core, angular for
of 6 by the carbonyl at the 12-position permitted the selective 12 and 14, and linear for 13 and 15, was unambiguously as-
O-alkylation of the 9-hydroxy group with 3-chloro-3-methyl- cribed for each compound from phase-sensitive NOESY ex-
27)
21,28)
but-1-yne (9), to give the corresponding propargylic ether periments.
0. Methylation of the 11-hydroxy group of 10, carried out In order to obtain dihydrodiols diesters similar to the
with dimethylsulfate in the presence of sodium hydride, gave highly active compounds in the benzo[a] and [b]acronycine
1
5—8)
1
1. When thermal cyclization was performed on the hydroxy series,
the (ꢀ)-cis-diols 16 and 17 were prepared by cat-
ether 10 for 2 h at 130 °C in dimethylformamide, the two iso- alytic osmium tetroxide oxidation of 14 and 15, respectively,
meric 6-hydroxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2- using N-methylmorpholine N-oxide to regenerate the oxidiz-
29)
h]xanthen-7-one (12) and 5-hydroxy-2,2-dimethyl-2H,6H- ing agent. The diols 16 and 17 were subsequently con-
benzo[a]pyrano[2,3-i]xanthen-6-one (13) were isolated in verted into the corresponding diacetates 18 and 19 upon
57% and 30% yield, respectively, after separation by column treatment with acetic anhydride, and the cyclic carbonates 20
chromatography. Benzopyranoxanthones 12 and 13 could be and 21, when N,Nꢁ-carbonyldiimidazole was used as acylat-
subsequently successfully converted into 6-methoxy-3,3-di- ing agent.
methyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (14) and
-methoxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xan- results in terms of cytotoxic activitiy were observed when the
electron donating methoxy group at C-6 was replaced by an
In the acronycine and benzoacronycine series, interesting
5
30)
amino substituent. Therefore, it appeared to us interesting
Chart 3
Reagents and conditions: (i) POCl , ZnCl , 65 °C; (ii) 9, K CO , KI, DMF,
3
2
2
3
6
5 °C; (iii) (CH ) SO , NaH, DMF, rt; (iv) DMF, 130 °C; (v) OsO , NMMO,
Reagents and conditions: (i) POCl , ZnCl , 65 °C; (ii) HBr, AcOH, Reflux; (iii)
3
2
4
4
3
2
tBuOH–THF–H O, rt; (vi) Ac O, C H N, rt.
9, K CO , KI, DMF, 65 °C, then 130 °C.
2
2
5
5
2
3
Chart 2
Chart 4

August 2006
1115
Table 1. Inhibition of L1210 and KB-3-1 Cell Proliferation by Benzo[a]pyrano[3,2-h]xanthone Derivatives 14, 16, 18, 20, 25 and Benzo[a]pyrano[2,3-
i]xanthone Derivatives 15, 17, 19, 21, 26 in Comparison with Acronycine (1), Benzo[a]acronycine (2), and Benzo[b]acronycine (3)
Compound
1
2
3
14
15
16
17
18
19
20
21
25
26
L1210 IC50 (mM)
KB-3-1 IC50 (mM)
23
37
2.5
8.5
2.0
3.4
22
34.5
21
30
1.0
28
16
19.5
42
7.5
19
50
3.0
37
46
30
40
19
27.5
31.5
1
1
1
1
13
1
13
1
to prepare compounds bearing a NH group at the correspon- techniques: H– H COSY, H– H NOESY, C– H HMQC, and C– H
2
ding position in both benzo[a]pyrano[3,2-h] and [2,3-i]xan- HMBC. These experiments were performed using standard Bruker micro-
programs. Mass spectra were recorded with a Nermag R-10-10C spectrome-
ter using electron impact (MS) and/or desorption chemical ionization (DCI-
thone series. The synthetic strategy used was similar to that
previously developed for the preparation of 12 and 13.
Accordingly, condensation of 2-hydroxy-1-naphthalenecar-
MS; reagent gas: NH ) techniques. Flash column chromatographies were
3
conducted using silica gel 60 Merck (35—70 mm) with an overpressure of
boxylic acid (7) with 3,5-dimethoxyaniline (22) gave 11- 300 mbars.
amino-9-methoxy-12H-benzo[a]xanthen-12-one (23), which
was converted into 11-amino-9-hydroxy-12H-benzo[a]xan-
then-12-one (24) upon treatment with hydrogen bromide in
acetic acid. Alkylation with 3-chloro-3-methyl-1-butyne fol-
9,11-Dihydroxy-12H-benzo[a]xanthen-12-one (6) To a mixture of 2-
hydroxy-1-naphthalenecarboxylic acid (7) (18.8 g, 100 mmol), anhydrous
phloroglucinol (8) (12.6 g, 100 mmol), and freshly fused zinc chloride (41 g),
phosphoryl chloride (100 ml) was added. The reaction mixture was stirred at
65 °C for 4 h, poured onto ice (1500 g) and left overnight. After filtration, the
lowed by Claisen rearrangement, afforded the desired 6- dark red precipitate was washed with saturated aqueous sodium bicarbonate
and water, and dried. Purification by flash column chromatography (solvent:
cyclohexane, then cyclohexane/acetone 99 : 1 to 80 : 20) gave 6 (6.31 g,
amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-
7-one (25) and 5-amino-2,2-dimethyl-2H,6H-benzo[a]py-
2
3%) as yellow needles, mp 194—195 °C (acetone/ethyl acetate 4 : 1). IR
rano[2,3-i]xanthen-6-one (26).
ꢂ1
(KBr) cm : 3380, 3270, 3100, 1639, 1573, 1511, 1437, 1336, 1235, 1153,
8
19. UV l (MeOH) nm (log e): 238 (sh.), 273 (4.63), 329 (4.30), 367
max
1
Pharmacology
(sh.). H-NMR (400 MHz, DMSO-d ) d: 6.23 (1H, d, Jꢃ2 Hz, C10-H), 6.41
6
(1H, d, Jꢃ2 Hz, C8-H), 7.61 (1H, td, Jꢃ8, 1 Hz, C3-H), 7.63 (1H, d,
The new benzopyranoxanthone derivatives were evaluated
in vitro for their cytotoxicity against two tumor cell lines, a
murine leukemia cell line (L1210) and a human epidermoid
Jꢃ9 Hz, C6-H), 7.74 (1H, td, Jꢃ8, 1 Hz, C2-H), 8.03 (1H, dd, Jꢃ8, 2 Hz,
C4-H), 8.31 (1H, d, Jꢃ9 Hz, C5-H), 9.91 (1H, dd, Jꢃ8, 1 Hz, C1-H), 10.99
13
(
1H, s, D O exch., C9-OH), 13.31 (1H, s, D O exch., C11-OH). C-NMR
2
2
carcinoma cell line (KB-3-1). The results (IC ) are reported (75 MHz, DMSO-d ) d: 182.7 (C-12), 165.6 (C-11), 163.3 (C-9), 157.7 (C-
5
0
6
in Table 1. Most compounds only displayed marginal an- 6a), 156.7 (C-7a), 138.0 (C-5), 130.5 (2C, C-12b, C-4a), 130.0 (C-2), 129.4
(
9
C-4), 126.7 (C-6), 126.4 (C-1), 118.3 (C-3), 112.6 (C-12a), 104.1 (C-11a),
9.1 (C-10), 93.9 (C-8). DCI-MS m/z: 279 [MH] . Anal. Calcd for
tiproliferative activity on both cell lines, within the same
order of magnitude as acronycine itself. Nevertheless, diol 16
and carbonate 20 showed significant cytotoxicity when tested
against L1210 cells.
ꢄ
C H O : C, 73.37; H, 3.62. Found: C, 73.25; H, 3.74.
1
7
10
4
1
1-Hydroxy-9-(1,1-dimethylpropargyloxy)-12H-benzo[a]xanthen-12-
one (10) A solution of 9,11-dihydroxy-12H-benzo[a]xanthen-12-one (6)
3.48 g, 12.5 mmol) in dry N,N-dimethylformamide (140 ml) was stirred and
(
heated at 65 °C for 24 h under nitrogen, in the presence of potassium carbon-
ate (3.45 g), potassium iodide (4.15 g) and 3-chloro-3-methylbut-1-yne (9)
Results and Discussion
All benzo[a]pyrano[2,3-i]xanthen-6-one derivatives, with
a pyran ring linearly fused on the tricyclic xanthone system,
(10.25 g, 100 mmol). Water (100 ml) was added and the precipitate was fil-
tered and dried. Flash column chromatography (solvent: cyclohexane/
are almost devoid of significant antiproliferative activity. In dichloromethane 50 : 50 to 5 : 95, then dichloromethane) gave 10 (3.19 g,
ꢂ1
7
1
(
(
4%) as a pale yellow amorphous solid. IR (KBr) cm : 3245, 2920, 1654,
contrast, it is interesting to note that compounds 16 and 20,
found significantly active against L1210 cell line, as well as
diacetate 18, which exhibits cytotoxic properties against
KB-3-1 cells, possess a pyran ring fused angularly onto the
581, 1503, 1448, 1355, 1247, 1142, 1025, 831, 749. UV lmax ꢄ(MeOH) nm
1
log e): 274 (4.45), 324 (4.23). DCI-MS m/z: 345 [MH] . H-NMR
400 MHz, CDCl ) d: 1.26 (6H, s, C(CH ) ), 2.74 (1H, s, C3ꢁ-H), 6.74 (1H,
3
3 2
d, Jꢃ2 Hz, C10-H), 6.89 (1H, d, Jꢃ2 Hz, C8-H), 7.54 (1H, d, Jꢃ9 Hz, C6-
benzoxanthone basic core. This is a common structural H), 7.62 (1H, td, Jꢃ8, 1 Hz, C3-H), 7.79 (1H, td, Jꢃ8, 1 Hz, C2-H), 7.93
1H, dd, Jꢃ8, 1 Hz, C4-H), 8.15 (1H, d, Jꢃ9 Hz, C5-H), 9.98 (1H, dd, Jꢃ8,
Hz, C1-H), 13.40 (1H, s, D O exch., C11-OH). Anal. Calcd for C H O :
(
1
feature with highly active acronycine and benzo[a] and
b]acronycine derivatives, which present a pyran ring angu-
larly fused onto the acridone tricyclic system. Nevertheless,
2
22 16
4
[
C, 76.73; H, 4.68. Found: C, 76.85; H, 4.69.
1-Methoxy-9-(1,1-dimethylpropargyloxy)-12H-benzo[a]xanthen-12-
1
all the new benzo[a]pyrano[3,2-h]xanthen-7-one derivatives one (11) Sodium hydride (0.07 g of 50% oil dispersion, 1.5 mmol) was
remain less potent than their benzo[a]pyrano[3,2-h]acridin-7- added to an ice-cooled solution of 11-hydroxy-9-(1,1-dimethylpropargy-
loxy)-12H-benzo[a]xanthen-12-one (10) (0.172 g, 0.5 mmol) in N,N-di-
one and benzo[b]pyrano[3,2-h]acridin-7-one counterparts in
methylformamide (5 ml). Dimethylsulfate (0.19 ml, 2 mmol) was added and
inhibiting the proliferation of L1210 and KB-3-1 cells. Con-
the reaction mixture was stirred under nitrogen at room temperature for
sidering the structure activity relationships, the acridone moi-
3.5 h. After addition of water (50 ml) and neutralization with 10% sulfuric
ety present in the natural alkaloid acronycine appears as an acid, the mixture was extracted with dichloromethane (4ꢅ20 ml). The or-
important structural requirement to maximize the cytotoxic ganic layers were evaporated under reduced pressure. Flash chromatography
(
solvent: cyclohexane, then cyclohexane/acetone 99 : 1 to 90 : 10) gave 11
effects in this series of drugs.
(0.14 g, 78%) as pale yellow prisms, mp 173—174 °C (acetone/ethyl acetate
ꢂ1
Experimental
4 : 1). IR (KBr) cm : 3200, 3114, 2932, 1635, 1611, 1577, 1511, 1433,
Chemistry The melting points were determined on a Leica VM appara-
1351, 1246, 1134, 819, 753. UV lmax (MeOH) nm (log e): 263 (sh.), 270
ꢂ1
1
tus and are not corrected. IR spectra (nmax in cm ) were obtained on a (4.86), 306 (4.47), 319 (4.50), 341 (sh.), 375 (sh.). H-NMR (400 MHz,
Perkin–Elmer 257 instrument. UV spectra (lmax in nm) were determined in CDCl ) d: 1.73 (6H, s, C(CH ) ), 2.46 (1H, s, C3ꢁ-H), 4.05 (3H, s, OCH ),
3
3
2
3
1
spectroscopic grade MeOH on a Beckman Model 34 spectrophotometer. H-
6.64 (1H, d, Jꢃ1 Hz, C10-H), 7.06 (1H, d, Jꢃ1 Hz, C8-H), 7.61 (1H, td,
1
3
NMR (d [ppm], J [Hz]) and C-NMR spectra were recorded at 400 and Jꢃ8, 1 Hz, C3-H), 7.67 (1H, d, Jꢃ9 Hz, C6-H), 7.73 (1H, td, Jꢃ8, 1 Hz, C2-
7
5 MHz, using Bruker Avance 400 and AC-300 spectrometers, respectively. H), 8.04 (1H, dd, Jꢃ8, 1 Hz, C4-H), 8.28 (1H, d, Jꢃ9 Hz, C5-H), 9.94 (1H,
1
3
When necessary, the signals were unambiguously assigned by 2D NMR dd, Jꢃ8, 1 Hz, C1-H). C-NMR (75 MHz, CDCl ) d: 177.8 (C-12), 161.4
3

1
116
Vol. 54, No. 8
(C-11), 160.5 (C-9), 157.5 (C-6a), 156.1 (C-7a), 135.6 (C-5), 131.1 (C-4a),
etate (3ꢅ50 ml). The organic layers were washed with 10% aqueous NaOH,
130.3 (C-12b), 129.0 (C-2), 128.2 (C-4), 127.2 (C-1), 125.8 (C-3), 117.3 (C-
and evaporated under reduced pressure. Flash chromatography (solvent: cy-
6), 115.6 (C-12a), 109.5 (C-11a), 99.0 (C-10), 98.2 (C-8), 84.9 (C-2ꢁ), 75.2 clohexane, then cyclohexane/acetone 99 : 1 to 90 : 10) gave 14 (1.03 g, 80%)
(
C-3ꢁ), 72.6 (C-1ꢁ), 56.4 (OCH ), 29.6 (2C, C-2ꢁ(CH ) ). DCI-MS m/z: 359 as pale yellow prisms, mp 202—203 °C.
3 3 2
ꢄ
[MH] . Anal. Calcd for C H O : C, 77.08; H, 5.06. Found: C, 76.99; H,
5-Methoxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one
(15) Methylation of 5-hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-
i]xanthen-6-one (13) (1.25 g, 3.6 mmol), under conditions similar to those
2
3
18
4
5
.08.
-Hydroxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one
6
(
6
12) and 5-Hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen- described for the preparation of 14 from 12, afforded 15 (1.01 g, 78%) as a
-one (13) A solution of 11-hydroxy-9-(1,1-dimethylpropargyloxy)-12H- yellow amorphous solid. IR (KBr) cm : 3052, 2971, 2924, 1643, 1604,
ꢂ1
benzo[a]xanthen-12-one (10) (1 g, 2.9 mmol) in N,N-dimethylformamide
1511, 1433, 1243, 1146, 823, 749. UV l (MeOH) nm (log e): 261 (sh.),
max
1
(60 ml) was heated under nitrogen at 130 °C for 2 h. Water (50 ml) was 282 (4.75), 340 (4.37). H-NMR (400 MHz, CDCl ) d: 1.51 (6H, s, C2-
3
added and the mixture was extracted with dichloromethane (3ꢅ50 ml). The
(CH ) ), 4.02 (3H, s, OCH ), 5.73 (1H, d, Jꢃ10 Hz, C3-H), 6.70 (1H, s,
3 2 3
organic layers were evaporated under reduced pressure. Flash chromatogra- C14-H), 6.80 (1H, d, Jꢃ10 Hz, C4-H), 7.47 (1H, d, Jꢃ9 Hz, C12-H), 7.56
phy (solvent: cyclohexane, then cyclohexane/acetone 99 : 1 to 95 : 5) gave (1H, td, Jꢃ8, 1 Hz, C9-H), 7.74 (1H, td, Jꢃ8, 1 Hz, C8-H), 7.87 (1H, dd,
successively 5-hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-
Jꢃ8, 1 Hz, C10-H), 8.05 (1H, d, Jꢃ9 Hz, C11-H), 10.06 (1H, dd, Jꢃ8, 1 Hz,
1
3
6-one (13) (0.301 g, 30%) and 6-hydroxy-3,3-dimethyl-3H,7H-benzo[a]-
C7-H). C-NMR (75 MHz, CDCl ) d: 177.4 (C-6), 158.5 (C-5), 157.2 (C-
3
pyrano[3,2-h]xanthen-7-one (12) (0.572 g, 57%) as pale yellow amorphous
solids.
13a), 156.3 (2C, C-14a, C-12a), 135.8 (C-11), 131.2 (C-6b), 130.4 (2C, C-3,
C-10a), 129.3 (C-8), 128.5 (C-10), 127.0 (C-7), 125.9 (C-9), 117.6 (C-12),
115.4 (2C, C-4, C-6a), 112.8 (C-5a), 112.4 (C-4a), 100.3 (C-14), 77.9 (C-2),
6
-Hydroxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one
ꢂ1
ꢄ
(
12): IR (KBr) cm : 3250, 3064, 2963, 2920, 1647, 1577, 1518, 1448,
62.9 (OCH ), 28.5 (2C, C-2(CH ) ). DCI-MS m/z: 359 [MH] . Anal. Calcd
3
3 2
1
3
344, 1274, 1145, 1114, 827, 746. UV l (MeOH) nm (log e): 276 (3.81),
for C H O : C, 77.08; H, 5.06. Found: C, 76.92; H, 5.15.
max
23 18 4
1
80 (2.94). H-NMR (400 MHz, CDCl ) d: 1.51 (6H, s, C(CH ) ), 5.62 (1H,
(ꢀ)-cis-1,2-Dihydroxy-6-methoxy-3,3-dimethyl-1,2-dihydro-3H,7H-
benzo[a]pyrano[3,2-h]xanthen-7-one (16) Compound 14 (0.537 g, 1.5
mmol) was added to a solution of osmium tetroxide (2.5% in 2-methyl-2-
3
3 2
d, Jꢃ10 Hz, C2-H), 6.30 (1H, s, C5-H), 6.82 (1H, d, Jꢃ10 Hz, C1-H), 7.45
(1H, d, Jꢃ9 Hz, C13-H), 7.56 (1H, td, Jꢃ8, 1 Hz, C10-H), 7.73 (1H, td,
Jꢃ8, 1 Hz, C9-H), 7.85 (1H, dd, Jꢃ8, 1 Hz, C11-H), 8.07 (1H, d, Jꢃ9 Hz, propanol, 1.08 ml) and 4-methylmorpholine N-oxide monohydrate (0.204 g,
C12-H), 9.89 (1H, dd, Jꢃ8, 1 Hz, C8-H), 13.54 (1H, s, D O exch., C6-OH). 1.5 mmol) in t-BuOH–THF–H O (10 : 3 : 1, 12 ml). The reaction mixture
2
2
13
C-NMR (75 MHz, CDCl ) d: 183.1 (C-7), 163.2 (C-6), 160.1 (C-4a),
was stirred at room temperature for 48 h. After addition of saturated aqueous
3
1
1
1
7
57.4 (C-13a), 150.7 (C-14a), 137.0 (C-12), 130.8 (C-7b), 130.3 (C-11a),
29.6 (C-9), 128.6 (C-11), 127.2 (C-2), 126.9 (C-8), 126.3 (C-10), 117.5 (C-
3), 115.3 (C-1), 113.2 (C-7a), 105.1 (C-6a), 100.6 (C-14b), 99.8 (C-5),
solution of sodium bisulfite (30 ml), the mixture was stirred for 1 h and then
extracted with dichloromethane (4ꢅ25 ml). The combined organic layers
were dried with sodium sulfate, filtered and evaporated under reduced pres-
sure. The crude product was purified by flash chromatography (solvent:
dichloromethane, then dichloromethane/acetone 99 : 1 to 90 : 10) to give 15
ꢄ
8.2 (C-3), 28.4 (2C, C3-(CH ) ). DCI-MS m/z: 345 [MH] . Anal. Calcd for
3
2
C H O : C, 76.73; H, 4.68. Found: C, 76.85; H, 4.63.
22
16
4
ꢂ1
5
-Hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one
(0.537 g, 90%) as a yellowish amorphous solid. IR (KBr) cm : 3425, 2971,
ꢂ1
(13): IR (KBr) cm : 3247, 3083, 2966, 2932, 1647, 1592, 1514, 1448,
2932, 1645, 1635, 1580, 1511, 1433, 1278, 1204, 1107, 819, 753. UV l
max
1
1
297, 1239, 1138, 823, 757. UV l (MeOH) nm (log e): 251 (4.49), 261
(MeOH) nm (log e): 260 (sh.), 271 (4.63), 320 (4.28), 358 (sh.). H-NMR
max
1
(
4.52), 298 (4.66), 349 (4.28). H-NMR (400 MHz, CDCl ) d: 1.51 (6H, s, (400 MHz, DMSO-d ) d: 1.41 (6H, s, C3-(CH ) ), 3.67 (1H, dd, Jꢃ8, 5 Hz,
3
6
3
2
C(CH ) ), 5.63 (1H, d, Jꢃ10 Hz, C3-H), 6.42 (1H, s, C14-H), 6.80 (1H, d, C2-H), 3.87 (3H, s, OCH ), 5.02 (1H, t, Jꢃ5 Hz, C1-H), 5.03 (1H, d,
3
2
3
Jꢃ10 Hz, C4-H), 7.51 (1H, d, Jꢃ9 Hz, C12-H), 7.61 (1H, td, Jꢃ8, 1 Hz, C9-
Jꢃ8 Hz, D O exch., C2-OH), 5.43 (1H, d, Jꢃ5 Hz, D O exch., C1-OH),
2
2
H), 7.78 (1H, td, Jꢃ8, 1 Hz, C8-H), 7.91 (1H, dd, Jꢃ8, 1 Hz, C10-H), 8.13
6.39 (1H, s, C5-H), 7.61 (1H, td, Jꢃ8, 1 Hz, C10-H), 7.73 (1H, td, Jꢃ8,
(
1H, d, Jꢃ9 Hz, C11-H), 9.98 (1H, dd, Jꢃ8, 1 Hz, C7-H), 13.82 (1H, s, D O 1 Hz, C9-H), 7.75 (1H, d, Jꢃ9 Hz, C13-H), 8.04 (1H, dd, Jꢃ8, 1 Hz, C11-
2
13
13
exch., C5-OH). C-NMR (75 MHz, CDCl ) d: 183.0 (C-6), 163.1 (C-14a),
1
H), 8.29 (1H, d, Jꢃ9 Hz, C12-H), 9.84 (1H, dd, Jꢃ8, 1 Hz, C8-H). C-
3
60.0 (2C, C-5, C-12a), 157.3 (C-13a), 136.8 (C-11), 130.8 (C-6b), 130.2 NMR (75 MHz, DMSO-d ) d: 177.0 (C-7), 161.6 (C-6), 158.4 (C-4a), 157.1
6
(C-10a), 129.5 (C-8), 128.5 (C-10), 127.1 (C-3), 126.8 (C-7), 126.2 (C-9),
(C-13a), 156.5 (C-14a), 136.6 (C-12), 131.3 (C-7b), 131.1 (C-11a), 129.9
(C-9), 129.7 (C-11), 127.0 (C-8), 126.8 (C-10), 119.1 (C-13), 115.6 (C-7a),
1
17.4 (C-12), 114.9 (C-4), 113.3 (C-6a), 105.2 (C-5a), 100.5 (C-4a), 99.7
ꢄ
(
C-14), 78.1 (C-2), 28.3 (2C, C3-(CH ) ). DCI-MS m/z: 345 [MH] . Anal. 108.9 (C-6a), 105.3 (C-14b), 97.1 (C-5), 80.4 (C-3), 75.2 (C-2), 65.1 (C-1),
3 2
ꢄ
Calcd for C H O : C, 76.73; H, 4.68. Found: C, 76.62; H, 4.73.
57.1 (OCH ), 27.9 (C3-CH ), 22.0 (C3-CH ). DCI-MS m/z: 393 [MH] .
3 3 3
22
16
4
6
-Methoxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one Anal. Calcd for C H O : C, 70.40; H, 5.14. Found: C, 70.32; H, 5.11.
23 20 6
(14) Method A: A solution of 11-methoxy-9-(1,1-dimethylpropargyloxy)-
(ꢀ)-cis-3,4-Dihydroxy-5-methoxy-2,2-dimethyl-3,4-dihydro-2H,6H-
1
2H-benzo[a]xanthen-12-one (11) (0.716 g, 2 mmol) in N,N-dimethylform- benzo[a]pyrano[2,3-i]xanthen-6-one (17) Oxidation of 15 (0.309 g,
0.86 mmol) under conditions similar to those described for the preparation
mixture was diluted with water (200 ml) and extracted with ethyl acetate of 16 from 14, afforded 17 (0.286 g, 85%) as a yellowish amorphous solid.
amide (50 ml) was heated under nitrogen at 130 °C for 1.5 h. The cooled
ꢂ1
(
3ꢅ50 ml). The organic layers were evaporated under reduced pressure. IR (KBr) cm : 3440, 3052, 2974, 2940, 1639, 1604, 1511, 1433, 1235,
Flash chromatography (solvent: cyclohexane/acetone 4 : 1) gave 14 (0.634 g, 1130, 827, 749. UV lmax (MeOH) nm (log e): 261 (sh.), 269 (4.70), 298
1
8
8%) as pale yellow prisms, mp 202—203 °C (cyclohexane/acetone 4 : 1). (4.21), 324 (4.45), 360 (sh.). H-NMR (400 MHz, DMSO-d ) d: 1.42 (3H, s,
6
ꢂ1
IR (KBr) cm : 3060, 2963, 2932, 1645, 1635, 1569, 1507, 1429, 1340, C2-CH ), 1.51 (3H, s, C2-CH ), 3.26 (1H, d, D O exch., Jꢃ4.5 Hz, C3-OH),
3
3
2
1
2
243, 1114, 815, 773. UV lmax (MeOH) nm (log e): 246 (4.44), 277 (4.66),
3.89 (1H, t, Jꢃ4.5 Hz, C3-H), 4.16 (3H, s, OCH ), 4.26 (1H, d, D O exch.,
3
2
1
99 (sh.), 326 (4.11), 362 (3.88). H-NMR (400 MHz, CDCl ) d: 1.52 (6H, Jꢃ1 Hz, C4-OH), 5.17 (1H, dd, Jꢃ4.5, 1 Hz, C4-H), 6.78 (1H, s, H-14),
3
s, C3-(CH ) ), 4.03 (3H, s, OCH ), 5.63 (1H, d, Jꢃ10 Hz, C2-H), 6.38 (1H,
7.49 (1H, d, Jꢃ9 Hz, C12-H), 7.59 (1H, td, Jꢃ8, 1 Hz, C9-H), 7.77 (1H, td,
3
2
3
s, C5-H), 6.92 (1H, d, Jꢃ10 Hz, C1-H), 7.48 (1H, d, Jꢃ9 Hz, C13-H), 7.56
Jꢃ8, 1 Hz, C8-H), 7.90 (1H, dd, Jꢃ8, 1 Hz, C10-H), 8.09 (1H, d, Jꢃ9 Hz,
1
3
(1H, td, Jꢃ8, 1 Hz, C10-H), 7.73 (1H, td, Jꢃ8, 1 Hz, C9-H), 7.87 (1H, dd, C11-H), 10.02 (1H, dd, Jꢃ8, 1 Hz, C7-H). C-NMR (75 MHz, DMSO-d6)
Jꢃ8, 1 Hz, C11-H), 8.10 (1H, d, Jꢃ9 Hz, C12-H), 10.18 (1H, dd, Jꢃ8, 1 Hz,
d: 177.3 (C-6), 160.8 (C-5), 158.0 (C-13a), 157.3 (C-14a), 156.6 (C-12a),
136.3 (C-11), 131.1 (C-6b), 130.4 (C-10a), 129.5 (C-8), 128.6 (C-10), 126.8
(C-7), 126.1 (C-9), 117.6 (C-12), 115.2 (C-6a), 114.2 (C-5a), 111.7 (C-4a),
13
C8-H). C-NMR (75 MHz, CDCl ) d: 178.0 (C-7), 161.6 (C-6), 158.2 (C-
3
4a), 155.9 (C-13a), 152.6 (C-14a), 135.7 (C-12), 131.3 (C-7b), 130.5 (C-
11a), 129.2 (C-9), 128.3 (C-11), 127.4 (C-2), 127.3 (C-8), 125.9 (C-10),
117.3 (C-13), 115.6 (C-7a), 115.5 (C-1), 108.7 (C-6a), 102.0 (C-14b), 96.2
101.0 (C-14), 79.0 (C-2), 70.8 (C-3), 62.8 (C-4), 62.6 (OCH ), 24.6 (C2-
3
ꢄ
CH ), 23.0 (C2-CH ). DCI-MS m/z: 393 [MH] . Anal. Calcd for C H O :
3
3
23 20
6
(
C-5), 78.2 (C-3), 56.6 (OCH ), 28.4 (2C, C3-(CH ) ). DCI-MS m/z: 359 C, 70.40; H, 5.14. Found: C, 70.27; H, 5.16.
3 3 2
ꢄ
[MH] . Anal. Calcd for C H O : C, 77.08; H, 5.06. Found: C, 77.01; H,
(ꢀ)-cis-1,2-Diacetoxy-6-methoxy-3,3-dimethyl-1,2-dihydro-3H,7H-
benzo[a]pyrano[3,2-h]xanthen-7-one (18) An ice-cooled mixture of
acetic anhydride (0.8 ml, 8 mmol) and pyridine (4 ml) was added to (ꢀ)-cis-
2
3
18
4
5
.12.
Method B: Sodium hydride (0.52 g of 50% oil dispersion, 10.8 mmol) was
slowly added to an ice-cooled solution of 5-hydroxy-2,2-dimethyl-2H,6H- 1,2-dihydroxy-6-methoxy-3,3-dimethyl-1,2-dihydro-3H,7H-benzo[a]-
benzo[b]pyrano[2,3-i]xanthen-6-one (12) (1.25 g, 3.6 mmol) in N,N-di- pyrano[3,2-h]xanthen-7-one (16) (0.078 g, 0.2 mmol). After stirring at room
methylformamide (60 ml). Dimethylsulfate (1.0 ml, 10.8 mmol) was added temperature for 3 d, the mixture was poured into cold water (10 ml). The pre-
and the reaction mixture was stirred under nitrogen at room temperature for cipitate was filtered, washed with water (2ꢅ5 ml) and dried in vacuo over
ꢂ1
2
h. After addition of ice (100 g), the mixture was extracted with ethyl ac- P O to give 16 (0.076 g, 80%) as an amorphous white solid. IR (KBr) cm
:
2 5

August 2006
1117
3
8
052, 2978, 2936, 1747, 1647, 1584, 1475, 1375, 1247, 1134, 1041, 1021,
23. UV lmax (MeOH) nm (log e): 270 (4.56), 319 (4.22). H-NMR MS m/z: 419 [MH] . Anal. Calcd for C H O : C, 68.90; H, 4.34. Found: C,
76.3 (C-2), 68.6 (C-4), 64.2 (OCH ), 24.3 (C2-CH ), 22.5 (C2-CH ). DCI-
3
3
3
1
ꢄ
24
18
7
(400 MHz, CDCl ) d: 1.48 (3H, s, C3-CH ), 1.53 (3H, s, C3-CH ), 2.16 (6H, 69.01; H, 4.25.
3
3
3
s, C1-OCOCH , C2-OCOCH ), 4.05 (3H, s, OCH ), 5.32 (1H, d, Jꢃ5 Hz,
11-Amino-9-methoxy-12H-benzo[a]xanthen-12-one (23) To a mixture
3
3
3
C2-H), 6.38 (1H, s, C5-H), 6.70 (1H, d, Jꢃ5 Hz, C1-H), 7.36 (1H, d, of 2-hydroxy-1-naphthalenecarboxylic acid (7) (5.64 g, 30 mmol), 3,5-
Jꢃ9 Hz, C13-H), 7.57 (1H, td, Jꢃ8, 1 Hz, C10-H), 7.73 (1H, td, Jꢃ8,1 Hz, dimethoxyaniline (22) (12.6 g, 100 mmol), and freshly fused zinc chloride
C9-H), 7.88 (1H, dd, Jꢃ8, 1 Hz, C11-H), 8.06 (1H, d, Jꢃ9 Hz, C12-H), (12 g), phosphoryl chloride (50 ml) was added. The reaction mixture was
1
3
1
7
(
0.07 (1H, dd, Jꢃ8, 1 Hz, C8-H). C-NMR (75 MHz, CDCl ) d: 177.5 (C-
stirred at 65 °C for 1.5 h, poured onto ice (500 g) and left overnight. After
filtration, the red precipitate was washed with saturated aqueous sodium bi-
carbonate and water, and dried in vacuum over P O . Purification by flash
3
), 170.4 (OCOCH ), 170.0 (OCOCH ), 162.5 (C-6), 158.3 (C-4a), 156.2
C-13a), 155.8 (C-14a), 136.1 (C-12), 131.1 (C-7b), 130.6 (C-11a), 129.4
C-9), 128.4 (C-11), 127.3 (C-8), 126.1 (C-10), 117.2 (C-13), 115.7 (C-7a),
3
3
2
5
(
column chromatography (solvent: cyclohexane, then cyclohexane/acetone
1
5
09.2 (C-6a), 98.9 (C-14b), 96.2 (C-5), 78.2 (C-3), 71.3 (C-2), 60.9 (C-1),
6.6 (OCH ), 26.1 (C3-CH ), 21.9 (OCOCH ), 21.0 (OCOCH ), 20.8 (C3-
99 : 1 to 80 : 20) gave 23 (2.04 g, 23%) as yellow needles, mp 186—187 °C
(cyclohexane/acetone 9 : 1). IR (KBr) cm : 3379, 3270, 3103, 2998, 1639,
ꢂ1
3
3
3
3
ꢄ
CH ). DCI-MS m/z: 477 [MH] . Anal. Calcd for C H O : C, 68.06; H, 1573, 1514, 1441, 1239, 1157, 819. UV l
(MeOH) nm (log e): 242
3
27 24
8
max
1
5
.08. Found: C, 68.12; H, 5.21.
(4.52), 285 (4.45), 299 (sh.), 381 (3.86). H-NMR (400 MHz, DMSO-d ) d:
6
(
ꢀ)-cis-3,4-Diacetoxy-5-methoxy-2,2-dimethyl-3,4-dihydro-2H,6H- 3.84 (3H, s, OCH ), 6.02 (1H, d, Jꢃ2 Hz, C10-H), 6.26 (1H, d, Jꢃ2 Hz, C8-
3
benzo[a]pyrano[2,3-i]xanthen-6-one (19) Acetylation of 17 (0.080 g, H), 6.82 (2H, br s, D O exch., C11-NH ), 7.44 (1H, d, Jꢃ9 Hz, C6-H), 7.56
2
2
0.204 mmol) under conditions similar to those described for the preparation
(1H, td, Jꢃ8, 1 Hz, C3-H), 7.74 (1H, td, Jꢃ8, 1 Hz, C2-H), 7.88 (1H, dd,
of 18 from 16, gave 19 (0.077 g, 79%) as a white amorphous solid. IR (KBr)
cm : 3056, 2990, 2936, 1744, 1650, 1608, 1514, 1437, 1375, 1235, 1091, C1-H). C-NMR (75 MHz, DMSO-d ) d: 181.1 (C-12), 164.6 (C-9), 158.1
Jꢃ8, 2 Hz, C4-H), 8.05 (1H, d, Jꢃ9 Hz, C5-H), 10.06 (1H, dd, Jꢃ8, 1 Hz,
ꢂ1
13
6
1
045, 827, 757. UV l
(MeOH) nm (log e): 251 (3.89), 274 (4.22), 299 (C-6a), 156.6 (C-7a), 152.3 (C-11), 135.7 (C-5), 131.2 (C-12b), 130.2 (C-
max
1
(
1
4.00), 322 (4.21). H-NMR (400 MHz, CDCl ) d: 1.45 (3H, s, C2-CH ), 4a), 129.0 (C-2), 128.4 (C-4), 126.8 (C-1), 125.6 (C-3), 117.6 (C-6), 114.4
3
3
.49 (3H, s, C2-CH ), 2.12 (6H, s, C3-OCOCH , C4-OCOCH ), 4.03 (3H, s, (C-12a), 104.7 (C-11a), 95.1 (C-10), 89.5 (C-8), 55.4 (OCH ). DCI-MS m/z:
3 3 3 3
ꢄ
OCH ), 5.26 (1H, d, Jꢃ5 Hz, C3-H), 6.48 (1H, d, Jꢃ5 Hz, C4-H), 6.75 (1H,
292 [MH] . Anal. Calcd for C H NO : C, 74.22; H, 4.50; N, 4.81. Found:
18 13 3
3
s, C14-H), 7.47 (1H, d, Jꢃ9 Hz, C12-H), 7.57 (1H, td, Jꢃ8, 1 Hz, C9-H),
C, 74.17; H, 4.49; N, 4.72.
7
.74 (1H, td, Jꢃ8, 1 Hz, C8-H), 7.87 (1H, dd, Jꢃ8, 1 Hz, C10-H), 8.06 (1H,
11-Amino-9-hydroxy-12H-benzo[a]xanthen-12-one (24) To a solution
of 23 (2.04 g, 7 mmol) in acetic acid (70 ml) was added 48% hydrogen bro-
mide aqueous solution (45 ml). The reaction mixture was refluxed for 4 d.
The cooled mixture was poured onto ice water (500 ml). The brown precipi-
tate was filtered, washed with water (4ꢅ100 ml), and dried in vacuum over
P O . Column chromatography (solvent: dichloromethane, then dichloro-
1
3
d, Jꢃ9 Hz, C11-H), 10.00 (1H, dd, Jꢃ8, 1 Hz, C7-H). C-NMR (75 MHz,
CDCl ) d: 177.2 (C-6), 170.2 (OCOCH ), 170.0 (OCOCH ), 161.6 (C-5),
3
3
3
1
1
58.1 (C-13a), 157.9 (C-14a), 156.4 (C-12a), 136.2 (C-11), 131.0 (C-6b),
30.4 (C-10a), 129.5 (C-8), 126.9 (C-7), 126.1 (C-9), 117.5 (C-12), 115.2
(C-6a), 112.2 (C-5a), 110.9 (C-4a), 100.6 (C-14), 77.0 (C-2), 71.5 (C-3),
2
5
6
2
6
2.8 (OCH ), 61.0 (C-4), 26.3 (C2-CH ), 21.9 (C2-CH ), 21.0 (OCOCH ), methane/methanol, 99 : 1 to 95 : 5) gave 24 (1.50 g, 77%) as bright yellow
3 3 3 3
ꢄ
ꢂ1
0.8 (OCOCH ). DCI-MS m/z: 477 [MH] . Anal. Calcd for C H O : C,
needles, mp 235—236 °C (dichloromethane/methanol 9 : 1). IR (KBr) cm :
3
27 24
8
8.06; H, 5.08. Found: C, 68.05; H, 5.14.
3476, 3359, 3309, 3091, 1643, 1549, 1514, 1464, 1347, 1169, 819, 742. UV
1
(
ꢀ)-cis-1,2-Di-O-carbonyloxy-6-methoxy-1,2-dihydro-3,3-dimethyl- lmax (MeOH) nm (log e): 241 (4.43), 286 (4.36), 382 (3.77). H-NMR
3
H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (20) To a solution of (ꢀ)-
(400 MHz, DMSO-d ) d: 6.05 (2H, s, C8-H, C10-H), 7.56 (1H, d, Jꢃ9 Hz,
6
cis-1,2-dihydroxy-6-methoxy-3,3-dimethyl-1,2-dihydro-3H,7H-benzo[a]- C6-H), 7.58 (1H, td, Jꢃ8, 1 Hz, C3-H), 7.70 (2H, br s, D O exch., C11-
2
pyrano[3,2-h]xanthen-7-one (16) (0.137 g, 0.35 mmol) in 2-butanone
NH ), 7.71 (1H, td, Jꢃ8, 1 Hz, C2-H), 8.01 (1H, dd, Jꢃ8, 2 Hz, C4-H), 8.23
2
(
10 ml), N,Nꢁ-carbonyldiimidazole (0.36 g, 2.1 mmol) was added. The reac- (1H, d, Jꢃ9 Hz, C5-H), 9.97 (1H, dd, Jꢃ8, 1 Hz, C1-H), 10.31 (1H, s, D O
2
1
3
tion mixture was refluxed for 24 h and after cooling, 5% aqueous Na CO
(
exch., C9-OH). C-NMR (75 MHz, DMSO-d ) d: 181.2 (C-12), 164.6 (C-
6
2
3
7 ml) was added. The mixture was extracted with EtOAc (3ꢅ10 ml). The 9), 158.9 (C-6a), 157.3 (C-7a), 154.7 (C-11), 137.1 (C-5), 132.0 (C-12b),
combined organic layers were dried over anhydrous Na SO and evaporated 131.3 (C-4a), 130.1 (C-2), 130.0 (C-4), 127.4 (C-1), 126.9 (C-3), 118.9 (C-
2
4
under reduced pressure. The crude product was purified by flash chromatog- 6), 114.8 (C-12a), 103.9 (C-11a), 97.0 (C-10), 91.2 (C-8). DCI-MS m/z: 278
ꢄ
raphy (solvent: dichloromethane, then dichloromethane/acetone 99 : 1 to
0 : 10) to give 20 (0.069 g, 47%) as a white amorphous solid. IR (KBr)
[MH] . Anal. Calcd for C H NO : C, 73.64; H, 4.00; N, 5.05. Found: C,
17 11 3
9
74.71; H, 4.06; N, 4.97.
6-Amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one
(25) and 5-amino-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-
ꢂ1
cm : 3052, 2975, 2940, 1794, 1658, 1580, 1476, 1243, 1173, 1106, 823.
1
UV lmax (MeOH) nm (log e): 270 (4.56), 318 (4.21). H-NMR (400 MHz,
DMSO-d ) d: 1.40 (3H, s, C3-CH ), 1.66 (3H, s, C3-CH ), 4.05 (3H, s, one (26) A solution of 24 (0.277 g, 1 mmol) in dry N,N-dimethylform-
6
3
3
OCH ), 4.85 (1H, d, Jꢃ8 Hz, C2-H), 6.18 (1H, d, Jꢃ8 Hz, C1-H), 6.41 (1H,
amide (15 ml) was stirred and heated at 65 °C for 15 min, under argon, in the
presence of anhydrous potassium carbonate (0.276 g, 2 mmol). Dry potas-
sium iodide (0.332 g, 2 mmol) and 3-chloro-3-methylbut-1-yne (0.308 g,
3 mmol) were added and the mixture was stirred for 24 h at 65 °C, then was
heated at 130 °C for 3 h. The cooled reaction mixture was diluted with water
(40 ml) and extracted with ethyl acetate (3ꢅ30 ml). The combined organic
3
s, C5-H), 7.54 (1H, d, Jꢃ9 Hz, C13-H), 7.60 (1H, td, Jꢃ8, 1 Hz, C10-H),
7
.75 (1H, td, Jꢃ8, 1 Hz, C9-H), 7.91 (1H, dd, Jꢃ8, 1 Hz, C11-H), 8.11 (1H,
1
3
d, Jꢃ9 Hz, C12-H), 10.06 (1H, dd, Jꢃ8, 1 Hz, C8-H). C-NMR (75 MHz,
DMSO-d ) d: 177.2 (C-7), 163.3 (C-6), 158.0 (C-4a), 156.7 (C-13a), 155.8
6
(C-14a), 154.0 (O–CO–O), 136.2 (C-12), 131.0 (C-7b), 130.7 (C-11a),
1
29.5 (C-9), 128.5 (C-11), 127.2 (C8), 126.3 (C-10), 117.3 (C-13), 115.8 layers were washed with water and evaporated under reduced pressure. Pu-
rification by flash column chromatography (solvent: cyclohexane, then cy-
), 56.8 (OCH ), 24.1 (C3-CH ), 22.6 (C3-CH ). DCI-MS m/z: 419 [MH] . clohexane/acetone 99 : 1 to 95 : 5) gave successively 5-amino-2,2-dimethyl-
(C-7a), 110.0 (C-6a), 97.1 (C-14b), 96.7 (C-5), 78.2 (2C, C-2, C-3), 68.3 (C-
ꢄ
1
3
3
3
Anal. Calcd for C H O : C, 68.90; H, 4.34. Found: C, 68.92; H, 4.39.
2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (26) (0.064 g, 19%) and 6-
ꢀ)-cis-3,4-Di-O-carbonyloxy-5-methoxy-2,2-dimethyl-3,4-dihydro- amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h] xanthen-7-one (25)
H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (21) Treatment of 17 (0.045 g, 13%) as bright yellow crystals.
0.105 g, 0.27 mmol) with N,Nꢁ-carbonyldiimidazole (0.220 g, 1.35 mmol) 6-Amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (25):
under conditions similar to those described for the preparation of 20, gave Yellow sheets, mp 175—176 °C (dichloromethane/methanol 4 : 1). IR (KBr)
24
18
7
(
2
(
ꢂ1
ꢂ1
2
2
1 (0.083 g, 73%) as a white amorphous solid. IR (KBr) cm : 3087, 2986, cm : 3301, 3056, 2971, 1635, 1569, 1514, 1433, 1340, 1243, 1142, 823,
944, 1817, 1647, 1608, 1511, 1433, 1375, 1243, 1161, 1087, 831, 765. UV 753. UV l (MeOH) nm (log e): 243 (4.45), 288 (4.60), 305 (sh.), 401
max
1
1
lmax (MeOH) nm (log e): 251 (3.72), 274 (4.09), 299 (3.80), 321 (3.98). H- (3.72). H-NMR (400 MHz, CDCl ) d: 1.50 (6H, s, C(CH ) ), 5.54 (1H, d,
3
3 2
NMR (400 MHz, CDCl ) d: 1.31 (3H, s, C2-CH ), 1.65 (3H, s, C2-CH ), Jꢃ10 Hz, C2-H), 5.97 (1H, s, C5-H), 6.87 (1H, d, Jꢃ10 Hz, C1-H), 6.88
3
3
3
4
.18 (3H, s, OCH ), 4.80 (1H, d, Jꢃ8 Hz, C3-H), 6.11 (1H, d, Jꢃ8 Hz, C4-
(2H, br s, D O exch., C6-NH ), 7.46 (1H, d, Jꢃ9 Hz, C13-H), 7.57 (1H, td,
3
2
2
H), 6.82 (1H, s, C14-H), 7.50 (1H, d, Jꢃ9 Hz, C12-H), 7.61 (1H, td, Jꢃ8, Jꢃ8, 1 Hz, C10-H), 7.73 (1H, td, Jꢃ8, 1 Hz, C9-H), 7.87 (1H, dd, Jꢃ8,
1
Hz, C9-H), 7.78 (1H, td, Jꢃ8, 1 Hz, C8-H), 7.91 (1H, dd, Jꢃ8, 1 Hz, C10-
1 Hz, C11-H), 8.04 (1H, d, Jꢃ9 Hz, C12-H), 10.05 (1H, dd, Jꢃ8, 1 Hz, C8-
1
3
13
H), 8.12 (1H, d, Jꢃ9 Hz, C11-H), 9.99 (1H, dd, Jꢃ8, 1 Hz, C7-H). C-
H). C-NMR (75 MHz, CDCl ) d: 181.3 (C-7), 158.7 (C-4a), 156.4 (C-
3
NMR (75 MHz, CDCl ) d: 177.0 (C-6), 162.5 (C-5), 158.6 (C-13a), 157.6
13a), 152.2 (C-14a), 152.0 (C-6), 135.8 (C-12), 131.3 (C-7b), 130.4 (C-11a),
129.2 (C-9), 128.5 (C-11), 126.9 (C-8), 125.7 (C-10), 125.7 (C-2), 117.6 (C-
13), 115.8 (C-1), 114.7 (C-7a), 104.4 (C-6a), 95.8 (C-14b), 97.1 (C-5), 77.6
3
(C-14a), 156.5 (C-12a), 154.0 (O–CO–O), 136.6 (C-11), 131.0 (C-6b),
130.5 (C-10a), 129.7 (C-8), 128.6 (C-10), 126.8 (C-7), 126.3 (C-9), 117.4
ꢄ
(C-12), 115.4 (C-6a), 113.0 (C-5a), 109.2 (C-4a), 101.8 (C-14), 78.2 (C-3),
(C-3), 28.4 (2C, C3-(CH ) ). DCI-MS m/z: 344 [MH] . Anal. Calcd for
3
2

1
118
Vol. 54, No. 8
C H NO : C, 76.95; H, 4.99; N, 4.08. Found: C, 77.07; H, 4.92; N, 3.99.
(2002).
22
17
3
5-Amino-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (26): 11) David-Cordonnier M.-H., Laine W., Joubert A., Tardy C., Goossens J.-
Yellow needles, mp 193—194 °C (ethyl acetate/acetone 4 : 1). IR (KBr)
F., Kouach M., Briand G., Doan Thi Mai H., Michel S., Tillequin F.,
Koch M., Léonce S., Pierré A., Bailly C., Eur. J. Biochem., 270,
2848—2859 (2003).
ꢂ1
cm : 3289, 2971, 1639, 1584, 1514, 1445, 1340, 1239, 1142, 823, 746. UV
1
lmax (MeOH) nm (log e): 252 (4.51), 260 (sh.), 317 (4.68), 389 (3.76). H-
NMR (400 MHz, CDCl ) d: 1.48 (6H, s, C(CH ) ), 5.62 (1H, d, Jꢃ10 Hz, 12) David-Cordonnier M.-H., Laine W., Kouach M., Briand G., Vezin H.,
3
3 2
C3-H), 6.23 (1H, s, C14-H), 6.42 (1H, d, Jꢃ10 Hz, C4-H), 7.11 (2H, br s,
D O exch., C6-NH ), 7.44 (1H, d, Jꢃ9 Hz, C12-H), 7.56 (1H, td, Jꢃ8, 1 Hz,
Gaslonde T., Michel S., Doan Thi Mai H., Tillequin F., Koch M.,
Léonce S., Pierré A., Bailly C., Bioorg. Med. Chem., 12, 23—29
(2004).
2
2
C9-H), 7.73 (1H, td, Jꢃ8, 1 Hz, C8-H), 7.87 (1H, dd, Jꢃ8, 1 Hz, C10-H),
1
3
8
.04 (1H, d, Jꢃ9 Hz, C11-H), 10.06 (1H, dd, Jꢃ8, 1 Hz, C7-H). C-NMR 13) Kupchan S. M., Streelman D. R., Sneden A. T., J. Nat. Prod., 43,
(
75 MHz, CDCl ) d: 181.1 (C-6), 158.8 (C-14a), 157.8 (C-12a), 156.5 (C-
296—301 (1980).
3
1
1
4
3a), 147.0 (C-5), 135.8 (C-11), 131.3 (C-6b), 130.4 (C-10a), 129.1 (C-8),
14) Habib A. M., Ho D. K., Masuda S., McCloud T., Reddy K. S.,
Aboushoer M., McKenzie A., Byrn S. R., Chang C.-J., Cassady J. M.,
J. Org. Chem., 52, 412—418 (1987).
28.5 (C-10), 127.4 (C-3), 126.9 (C-7), 125.7 (C-9), 117.7 (C-12), 115.7 (C-
), 114.5 (C-6a), 104.7 (C-5a), 101.8 (C-4a), 92.7 (C-14), 76.9 (C-2), 27.9
ꢄ
(2C, C3-(CH ) ). DCI-MS m/z: 344 [MH] . Anal. Calcd for C H NO : C, 15) Abou-Shoer M., Boettner F. E., Chang C.-J., Cassady J. M., Phyto-
3
2
22 17
3
7
6.95; H, 4.99; N, 4.08. Found: C, 76.85; H, 4.96; N, 4.09.
chemistry, 27, 2795—2800 (1988).
Pharmacology Cytotoxicity: Murine leukemia L1210 cells from the 16) Permana P. A., Ho D. K., Cassady J. M., Snapka R. M., Cancer Res.,
American Type Culture Collection (Rockville Pike, MD, U.S.A.) were
grown in RPMI medium 1640 supplemented with 10% fetal calf serum,
54, 3191—3195 (1994).
17) Hansen M., Lee S.-J., Cassady J. M., Hurley L. H., J. Am. Chem. Soc.,
118, 5553— 5561 (1996).
2
mM L-glutamine, penicillin 100 U/ml, streptomycin 100 mg/ml and 10 mM
HEPES buffer (pH 7.4). The cytotoxicity was measured using the microcul- 18) Michel S., Seguin E., Tillequin F., Curr. Med. Chem., 9, 1689—1700
31)
ture tetrazolium assay essentially as described. Cells were exposed for
8 h to nine graded concentrations in triplicate of the test drug. Results are
(2002).
4
19) David-Cordonnier M.-H., Laine W., Gaslonde T., Michel S., Tillequin
F., Koch M., Léonce S., Pierré A., Bailly C., Curr. Med. Chem.-Anti-
Cancer Agents, 4, 82—92 (2004).
expressed as IC50 values (mean, nꢃ3), which are defined as the drug con-
centration inhibiting the absorbance by 50% with respect to that of untreated
cells.
20) Michel S., Gaslonde T., Tillequin F., Eur. J. Med. Chem., 39, 649—655
(2004).
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