Synthesis and cytotoxic and antitumor activity of benzo[b]pyrano[3,2- h]acridin-7-one analogues of acronycine

Article abstract of DOI:10.1021/jm990972l

Benzo[b]acronycine (6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H- benzo[b]pyrano[3,2-h]acridin-7-one, 4), an acronycine analogue with an additional aromatic ring linearly fused on the natural alkaloid basic skeleton, was synthesized in three steps, starting

Full text of DOI:10.1021/jm990972l

J . Med. Chem. 2000, 43, 2395-2402
2395
Syn th esis a n d Cytotoxic a n d An titu m or Activity of
Ben zo[b]p yr a n o[3,2-h ]a cr id in -7-on e An a logu es of Acr on ycin e
Nadine Costes,§ Herve´ Le Deit,§ Sylvie Michel,§ Franc¸ois Tillequin,*,§ Michel Koch,§ Bruno Pfeiffer,†
Pierre Renard,† Ste´phane Le´once,# Nicolas Guilbaud,# Laurence Kraus-Berthier,# Alain Pierre´,# and
Ghanem Atassi#
Laboratoire de Pharmacognosie de l’Universite´ Rene´ Descartes, UMR/ CNRS No. 8638, Faculte´ des Sciences Pharmaceutiques
et Biologiques, 4 Avenue de l’Observatoire, 75006 Paris, France, ADIR et Compagnie, 1 rue Carle Hebert, 92415 Courbevoie
Cedex, France, and Division de Cance´rologie Expe´rimentale, Institut de Recherches Servier, 11 rue des Moulineaux,
92150 Suresnes, France
Received December 22, 1999
Benzo[b]acronycine (6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-
7-one, 4), an acronycine analogue with an additional aromatic ring linearly fused on the natural
alkaloid basic skeleton, was synthesized in three steps, starting from 3-amino-2-naphthalen-
ecarboxylic acid (5). Eight 1,2-dihydroxy-1,2-dihydrobenzo[b]acronycine esters and diesters (17-
24) were obtained by catalytic osmic oxidation, followed by acylation. All these compounds
were significantly more cytotoxic than acronycine, when tested against L1210 leukemia cells
in vitro. The potency of the cyclic carbonate 24 was in the range of the most active drugs
currently used in cancer chemotherapy. Two selected diesters (17 and 24) were evaluated in
vivo against P388 leukemia and colon 38 adenocarcinoma implanted in mice. Both compounds
were markedly active at doses 16-fold lower than the dose of acronycine itself. Against colon
38 adenocarcinoma, compounds 17 and 24 were highly efficient, inhibiting tumor growth by
more than 80%. Diacetate 17 was the most active, inhibiting tumor growth by 96% at 6.25
mg/kg, with two of seven mice being tumor-free on day 43.
Ch a r t 1. Acronycine (1), Acronycine Epoxide (2), and
(()-cis-1,2-Diacetoxy-1,2-dihydroacronycine (3)
In tr od u ction
The acridone alkaloid acronycine (1) (Chart 1), first
isolated from Acronychia baueri Schott (Rutaceae) in
1948,1,2 exhibits a broad spectrum of activity against
numerous solid tumors including sarcoma, myeloma,
carcinoma, and melanoma.2,3 Nevertheless, clinical tri-
als only gave poor results,4 probably due to the moderate
potency of this alkaloid. The isolation of the unstable
acronycine epoxide (2) from several New Caledonian
Sarcomelicope species led to the hypothesis of bioacti-
vation of acronycine by transformation of the 1,2-double
bond into the corresponding oxirane in vivo.2,5 Conse-
quently, there was interest in the search for new
acronycine derivatives modified in the pyran ring and
having improved stability but a similar reactivity
toward nucleophilic agents as acronycine epoxide.6a
Accordingly, we recently synthesized a series of cis- and
trans-1,2-dihydroxy-1,2-dihydroacronycine diesters which
exhibited interesting antitumor properties with a broad-
ened spectrum of activity and increased potency when
compared with acronycine.6 The cis isomers were the
most promising, and (()-cis-1,2-diacetoxy-1,2-dihydroa-
cronycine (3) was of particular interest, because of its
marked activity in vivo against P388 leukemia and
against the resistant solid tumor C38 colon carcinoma.6a
Despite the broad antitumor spectrum of acronycine
and its derivatives, the mechanism of their action at
both cellular and molecular level has not yet been
clearly established.2 Early experiments suggested that
this alkaloid acted primarily by alteration of membra-
nous organelles and that its delayed effects were due
at least in part to interference with the structure and
function of cell-surface components.7 Nevertheless, a
more recent investigation of the DNA binding property
of acronycine by Dorr and Liddil demonstrated that this
alkaloid should interact with DNA, either by intercala-
tion or by some other noncovalent process able to
stabilize the double helix against thermal denaturation.8
Interaction with DNA is known to occur mainly for
compounds with sufficiently large coplanar aromatic
chromophores in the related acridine, ellipticine, and
* To whom correspondence should be addressed. Tel: 33-1-43-25-
23-58. Fax: 33-1-40-46-96-58. E-mail: tillequi@pharmacie.univ-
paris5.fr.
§ Laboratoire de Pharmacognosie de l’Universite´ Rene´ Descartes.
† ADIR et Compagnie.
#
Institut de Recherches Servier.
10.1021/jm990972l CCC: $19.00 © 2000 American Chemical Society
Published on Web 05/24/2000

2396 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 12
Costes et al.
Sch em e 1. Synthesis of 6-Methoxy-3,3,14-trimethyl-
3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-onea
Ch a r t 2. Compounds 7, 8, and 10-15
phenol at 3-position of 7 was performed by a Claisen
rearrangement of the corresponding dimethylpropargyl
ether. Thus, treatment of 7 with 3-chloro-3-methyl-
but-1-yne (8)12 at 65 °C in dimethylformamide in the
presence of potassium carbonate and potassium iodide,
followed by heating at 130 °C, afforded the required
6-hydroxy-3,3-dimethyl-3,14-dihydro-7H-benzo[b]pyrano-
[3,2-h]acridin-7-one (9), isolated in 44% yield after
purification by column chromatography. This compound
was accompanied by 14% of 5-hydroxy-1,1-dimethyl-2-
methylene-1,2-dihydrobenzo[b]furo[3,2-h]acridin-6(13H)-
one (10), arising from cyclization in alkaline medium
of a product of the C-alkylation of 7 by 3-chloro-3-
methylbut-1-yne.13 In addition, the corresponding pyr-
ano and furano linear isomers were obtained in 2%
overall yield as a mixture and could only be separated
as their O,N-dimethyl derivatives 11 and 12. Methyla-
tion of 9 with dimethyl sulfate afforded the N-methyl
compound 13 when the reaction was carried out in the
presence of 1 equiv of sodium hydride and afforded the
desired 6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-
benzo[b]pyrano[3,2-h]acridin-7-one (4) when 2.5 equiv
of sodium hydride was used. In a similar way, 10 was
converted into the corresponding N-methyl derivative
14 and O,N-dimethyl derivative 15. Phase-sensitive
NOESY experiments performed on O,N-dimethyl de-
rivatives permitted to ascribe unambiguously angular
structures to compounds 4 and 15, obtained from the
major cyclization product 9 and 10, and linear struc-
tures to minor derivatives 11 and 12.14
a
Reagents and conditions: (i) refluxing heptan-1-ol, p-toluene-
sulfonic acid, 48 h; (ii) anhyd K2CO3 and KI in dry DMF under
argon, 24 h at 65 °C; (iii) heating 3 h at 130 °C; (iv) NaH (2.5
equiv) and (CH3)2SO4 (6 equiv) in dry DMF.
anthracene-dione series.9 Therefore, the assumption of
a step involving DNA intercalation in the mode of action
of acronycine8 prompted us to develop structural ana-
logues with an additional aromatic ring linearly fused
on the natural alkaloid basic skeleton. We describe here
the synthesis and the biological properties of 6-methoxy-
3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]-
acridin-7-one (4) and of related cis-1,2-dihydro-1,2-diol
diesters.
Ch em istr y
The strategy used to build up the pentacyclic basic
core was similar with that previously developed by
Hlubucek et al. for the synthesis of acronycine.10 Con-
densation of 3-amino-2-naphthalenecarboxylic acid (5)
with phloroglucinol (6) carried out in 1-heptanol in the
presence of 4-toluenesulfonic acid11 afforded 1,3-dihy-
droxybenz[b]acridin-12(5H)-one (7) in 88% yield (Scheme
1). Construction of the dimethylpyran ring onto the
The (()-cis-diol 16 (Scheme 2) was conveniently
obtained by catalytic osmium tetroxide oxidation of 4
using N-methylmorpholine N-oxide to regenerate the
oxidizing agent.15 Treatment of diol 16 with excess acetic

Benzopyranoacridinone Analogues of Acronycine
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 12 2397
Ta ble 1. Cytotoxicity and Antitumor Activity of the
Compounds
Sch em e 2. Synthesis of (+)-cis-1,2-Dihydroxy-6-
methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-
benzo[b]pyrano[3,2-h]acridin-7-one Esters
cytotoxicity
IC50 L1210
(µM)a
P388 leukemiab
optimal dose,d
T/C (survival)
C38 adenocarcinomac
optimal dose,d
T/C (tumor vol)
compd
1 (acronycine)
3
19.9
3.4
200 mg/kg, ip, 125%
12.5 mg/kg, ip, 224%
12.5 mg/kg, iv, 202%
4
7
1.9
6.0
9
10.2
3.2
4.9
8.5
17.9
9.0
14.1
40.8
0.6
10
11
12
13
14
15
16
17
12.5 mg/kg, ip, 213% 6.25 mg/kg, iv, 4%
12.5 mg/kg, iv, 178%
18
19
20
21
22
23
24
0.9
0.5
1.9
1.7
0.5
0.2
0.02
12.5 mg/kg, ip, 327% 3.12 mg/kg, iv, 18%
12.5 mg/kg, iv, 157%
a
Inhibition of L1210 cell proliferation measured by the MTA
assay (mean of at least 2 values obtained in separate experiments).
b
Mice were inoculated ip on day 0 with 106 P388 cells, and the
compounds were administered ip or iv on day 1. c Tumor fragments
were implanted sc on day 0, and the compounds were administered
iv on days 10 and 19. The tumor volume was measured on day
d
31. Dose (mg/kg) giving the optimal therapeutic effect without
toxicity.
Resu lts a n d Discu ssion
These novel derivatives of acronycine were studied
in vitro on L1210 leukemic cells. The results, expressed
as IC50 values, are reported in Table 1. Compared to
acronycine, compounds 17-19 and 22-24 were mark-
edly more potent, the most cytotoxic derivative, com-
pound 24, being 1000-fold more potent than acronycine
in inhibiting L1210 cell proliferation. All these cytotoxic
compounds bear, in addition to the aromatic ring fused
to the acronycine skeleton, a methoxy group at position
6 and two esters at positions 1 and 2. The importance
of the esterification of positions 1 and 2 is illustrated
by the lack of significant cytotoxicity of the diol deriva-
tive (compound 16). The monoesterified compounds 20
and 21 show an intermediate cytotoxicity. The potency
of compound 24 is noteworthy, being in the range of the
most active cytotoxic drugs used in cancer chemo-
therapy.
The perturbation of the cell cycle induced by these
compounds was studied on the same cell line. Acrony-
cine induced a partial accumulation of cells in the
G2+M phase of the cell cycle at a high concentration,
as previously described6 (Figure 1B). In contrast, the
cytotoxic derivatives differently modified the DNA
distribution, in that they induced a marked accumula-
tion of cells in the S phase. Figure 1C shows the effect
of 100 nM compound 24 which induced the accumula-
tion of 74% of L1210 cells in the S phase (versus 36%
for untreated cells). Moreover, a good relation was found
in the series between cytotoxicity and potency in ac-
cumulating cells in the S phase of the cell cycle, which
suggests that the cell death is the consequence of an
irreversible arrest in S phase. Interestingly, the fact
that these compounds induced a perturbation of the cell
cycle different from that of acronycine suggests that they
anhydride, propionic anhydride, or isovaleryl chloride
afforded the corresponding diesters 17, 18, and 19,
respectively. Under controlled conditions, monoesters at
the less hindered 2-position, exemplified by valerate 20
and benzoate 21, were obtained. Treatment of monov-
alerate 20 and monobenzoate 21 with excess acetic
anhydride led to the mixed esters 22 and 23, respec-
tively. Finally, treatment of diol 16 with N,N′-carbon-
yldiimidazole in 2-butanone under reflux afforded the
cyclic carbonate 24.

2398 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 12
Costes et al.
curative in that they did not induce long-term survivors.
Interestingly, a significant antitumor activity was main-
tained following administration by the iv route, indicat-
ing a favorable distribution of these compounds. Against
the colon 38 adenocarcinoma, compounds 17 and 24
were highly efficient, inhibiting tumor growth by more
than 80%. The derivative 17 was the most active, since
tumor growth was inhibited by 96% at 6.25 mg/kg and
two of seven mice were tumor-free on day 43.
In conclusion, some of the derivatives described in this
work are markedly more potent in vitro and in vivo and
considerably more active in vivo than acronycine. The
most potent derivative, compound 17, is moderately
active on P388 leukemia and induces tumor regression
of the resistant C38 adenocarcinoma. The very favorable
profile of this series, in terms of solid tumor selectivity,
is currently under investigation in experimental models
of solid tumors, including resistant human tumors, for
the most active derivatives.
Exp er im en ta l Section
Ch em istr y. Melting points were determined on a hot stage
Reichert microscope and are uncorrected. Mass spectra were
recorded with a Nermag R-10-10C spectrometer using elec-
tronic impact (EIMS) and/or chemical ionization (CIMS;
reagent gas: NH3) techniques. UV spectra (λmax in nm) were
recorded in spectroscopic grade MeOH on a Beckman model
34 spectrophotometer. IR spectra (νmax in cm-1) were obtained
from potassium bromide pellets or sodium chloride films on a
1
Perkin-Elmer 257 instrument. H NMR (δ [ppm], J [Hz]) and
13C NMR spectra were recorded at 300 and 75 MHz, respec-
tively, using a Bruker AC-300 spectrometer. When necessary,
the signals were unambiguously assigned by 2D NMR tech-
niques: 1H-1H COSY, 1H-1H NOESY, 13C-1H HETCOR, and
13C-1H COLOC. These experiments performed using standard
Bruker microprograms. Column chromatographies were car-
ried out with silica gel 20-45 µm. Flash column chromatog-
raphies were conducted using silica gel 60 Merck (35-70 µm)
with an overpressure of 300 mbars.16 Microanalyses were in
agreement with calculated values (0.4%.
Biologica l Ma ter ia ls. Cell Cu ltu r e a n d Cytotoxicity.
L1210 cells were cultivated in RPMI 1640 medium (Gibco)
supplemented with 10% fetal calf serum, 2 mM L-glutamine,
100 units/mL penicillin, 100 µg/mL streptomycin, and 10 mM
HEPES buffer (pH ) 7.4). Cytotoxicity was measured by the
microculture tetrazolium assay (MTA) as described.17 Cells
were exposed to graded concentrations of drug (nine serial
dilutions in triplicate) for 48 h. Results are expressed as IC50
,
the concentration which reduced by 50% the optical density
of treated cells with respect to the optical density of untreated
controls.
For the cell cycle analysis, L1210 cells (5 × 105 cells/mL)
were incubated for 21 h with various concentrations of drugs.
Cells were then fixed by 70% ethanol (v/v), washed, and
incubated in PBS containing 100 µg/mL RNAse and 50 µg/mL
propidium iodide for 30 min at 20 °C. For each sample, 10 000
cells were analyzed on a XLMCL flow cytometer (Beckman
Coulter, France).
F igu r e 1. Typical DNA histogram and distribution into the
different phases of the cell cycle of untreated L1210 cells (A)
or L1210 cells treated for 21 h with 50 µM compound 1 (B) or
0.1 µM compound 24 (C).
act, at the molecular level, through a different mecha-
nism of action.
An titu m or Activity. The antitumor activity of the com-
pounds was evaluated on two experimental murine models:
P388 leukemia and colon 38 adenocarcinoma. P388 cells (NCI,
Frederick) were inoculated ip (106 cells/mouse) into B6D2F1
mice (Iffa credo) on day 0. The drugs were dissolved in DMSO,
diluted in 5% Tween 80 in water, and injected ip or iv on day
1. The results are expressed in terms of percent T/C (median
survival time of treated animals divided by median survival
time of controls × 100). Colon adenocarcinoma 38 (NCI,
Frederick, MD) was introduced by sc implantation of a tumor
fragment into the dorsal flank. The drugs were administered
by iv injection on days 10 and 19. The tumor volume was
measured on day 31 and the results are expressed as percent
In vivo, two standard experimental models were used,
the sensitive ip P388 leukemia and the more resistant
sc colon 38 adenocarcinoma. To make this latter model
more resistant to chemotherapy, the compounds were
administered when the tumor volume reached a weight
of 60-100 mg, i.e., 10 days after tumor implant. Table
1 shows the results, in terms of percent T/C, obtained
at the dose giving the best therapeutic effect without
toxicity. Againt P388 leukemia, acronycine was only
marginally active, while compounds 3, 17, and 24 were
significantly active at doses 16-fold lower but not

Benzopyranoacridinone Analogues of Acronycine
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 12 2399
T/C (median tumor volume in treated animals divided by
median tumor volume of controls × 100).
min, the reaction mixture was diluted with ice water and
extracted with ethyl acetate. The organic layer, washed with
1 M NaOH solution and water was evaporated under reduced
pressure. Purification by flash chromatography (solvent: cy-
clohexane then cyclohexane/acetone, 96:4 to 90:10) gave 13 as
an orange amorphous solid (0.325 g, 89%): 1H NMR (300 MHz,
CDCl3) 1.54 (s, 6H), 3.95 (s, 3H, NCH3), 5.54 (d, J ) 9 Hz, 1H,
H2), 6.22 (s, 1H, H5), 6.59 (d, J ) 9 Hz, 1H, H1), 7.42 (td, J )
8, 1.5 Hz, 1H, H10), 7.56 (td, J ) 8, 1.5 Hz, 1H, H11), 7.68 (s,
1H, H13), 7.87 (dd, J ) 8, 1.5 Hz, 1H, H12), 7.98 (dd, J ) 8, 1.5
Hz, 1H, H9), 8.90 (s, 1H, H8), 14.30 (s, 1H, OH); 13C NMR (75
MHz, DMSO-d6) 26.9 (2 × CH3), 44.0 (NCH3), 76.6 (C3), 97.3
(C5), 101.0 (C14b), 106.0 (C6a), 112.2 (C13), 121.6 (C1), 121.7 (C7a),
123.0 (C2), 124.9 (C10), 126.9 (C12), 127.4 (C8), 128.3 (C8a), 128.8
(C11), 129.4 (C9), 136.3 (C12a), 141.6 (C13a), 145.1 (C14a), 162.2
(C4a), 165.6 (C6), 182.0 (C7); CIMS m/z 358 [MH]+.
1,3-Dih yd r oxyben z[b]a cr id in -12(5H)-on e (7). A solution
containing 3-amino-2-naphthalenecarboxylic acid (5) (5 g, 26.7
mmol), dried phloroglucinol (6) (3.5 g, 27.7 mmol), and p-
toluenesulfonic acid (63.5 g, 32.8 mmol) in heptanol (50 mL)
was heated for 48 h, under reflux, using a Dean-Stark trap
to remove water. The mixture was evaporated under reduced
pressure and the dark brown residue purified by flash chro-
matography (solvent: cyclohexane then cyclohexane/acetone,
9:1 to 7:3) to give 7 (6.3 g, 88%) as orange needles: mp > 350
1
°C (cyclohexane/acetone, 1:1); H NMR (300 MHz, DMSO-d6)
5.97 (d, J ) 2 Hz, 1H, H2), 6.28 (d, J ) 2 Hz, 1H, H4), 7.41 (td,
J ) 8, 1 Hz, 1H, H9), 7.56 (td, J ) 8, 1 Hz, 1H, H8), 7.82 (s,
1H, H6), 7.96 (dd, J ) 8, 1 Hz, 1H, H7), 8.13 (dd, J ) 8, 1 Hz,
1H, H10), 8.85 (s, 1H, H11), 10.68 (s, 1H, NH), 11.65 (s, 1H,
OH3), 14.08 (s, 1H, OH1); 13C NMR (75 MHz, DMSO-d6) 92.4
(C4), 96.4 (C2), 103.4 (C12a), 112.9 (C6), 121.2 (C11a), 125.8 (C9),
127.9 (C7 + C11), 129.2 (C4a), 130.2 (C8), 131.0 (C10), 137.3 (C10a),
138.8 (C6a), 145.9 (C5a), 165.6 (C3), 166.6 (C1), 182.4 (C12); CIMS
m/z 278 [MH]+; IR (KBr) 3350, 3080, 2980, 1647, 1591, 1546,
1510, 1474, 1428, 1346, 1272, 1176, 1101, 811; UV λ nm
(MeOH) (log ꢀ) 224 (4.17), 242 (sh), 279 (4.79), 351 (3.91).
Rea ction of 7 w ith 3-Ch lor o-1-m eth ylbu t-1-yn e (8). A
solution of 7 (2 g, 7.22 mmol) in dry N,N-dimethylformamide
(100 mL) was stirred and heated at 65 °C for 15 min, under
nitrogen, in the presence of anhydrous potassium carbonate
(2 g, 14.4 mmol). Then, dry potassium iodide (2.4 g, 14.4 mmol)
and excess 3-chloro-3-methylbut-1-yne (5.9 g, 57 mmol) were
added and the mixture was stirred for 24 h. Rearrangement
of the propargylic ether occurred by heating the mixture at
130 °C for 1.5 h. The cooled reaction mixture was diluted with
water and extracted with CH2Cl2. The combined organic layers
were washed with water and evaporated under reduced
pressure. Purification by flash chromatography (solvent: cy-
clohexane then cyclohexane/acetone, 98:2 to 90:10) afforded 9
as an amorphous orange solid (1.1 g, 44%), 10 as a yellow solid
(0.34 g, 14%), and an inseparable mixture of the corresponding
linear pyrano and furano isomers (0.05 g, 2%).
6-Hyd r oxy-3,3-d im eth yl-3,14-d ih yd r o-7H-ben zo[b]p yr -
a n o[3,2-h ]a cr id in -7-on e (9): 1H NMR (300 MHz, DMSO-d6)
1.45 (s, 6H), 5.74 (d, J ) 10 Hz, 1H, H2), 6.01 (s, 1H, H5), 7.12
(d, J ) 10 Hz, 1H, H1), 7.43 (td, J ) 9, 1.5 Hz, 1H, H10), 7.60
(td, J ) 9, 1.5 Hz, 1H, H11), 7.96 (dd, J ) 9, 1.5 Hz, 1H, H12),
8.13 (dd, J ) 9, 1.5 Hz, 1H, H9), 8.16 (s, 1H, H13), 8.86 (s, 1H,
H8), 11.05 (s, 1H, N-H), 14.51 (s, 1H, OH); 13C NMR (75 MHz,
DMSO-d6) 28.7 (2 × CH3), 78.4 (C3), 96.7 (C5), 99.0 (C14b), 103.8
(C6a), 113.8 (C13), 117.2 (C1), 120.8 (C7a), 125.7 (C10), 126.9 (C2),
127.5 (C8), 127.9 (C12), 129.2 (C14a), 129.9 (C11), 130.7 (C9), 137.1
(C8a), 138.5 (C12a), 139.9 (C13a), 161.2 (C4a), 165.5 (C6), 182.8
(C7); EIMS m/z 343 [M]+, 328; IR (NaCl) 3350, 3200-2500,
1636, 1582, 1552, 1474, 1345, 1168, 1136, 871, 822; UV λ nm
(MeOH) (log ꢀ) 250 (sh), 275 (4.92), 291 (4.81), 311 (sh), 367
(4.06).
5-Hyd r oxy-1,1-d im eth yl-2-m eth ylen e-1,2-d ih yd r oben -
zo[b]fu r o[3,2-h ]a cr id in -6(13H)-on e (10): 1H NMR (300
MHz, DMSO-d6) 1.72 (s, 6H), 4.55 (d, J ) 3 Hz, 1H, H1′a), 4.70
(d, J ) 3 Hz, 1H, H1′b), 6.25 (s, 1H, H4), 7.42 (td, J ) 8, 1 Hz,
1H, H9), 7.59 (td, J ) 8, 1 Hz, 1H, H10), 7.92 (dd, J ) 8, 1 Hz,
1H, H11), 8.11 (dd, J ) 8, 1 Hz, 1H, H8), 8.46 (s, 1H, H12), 8.82
(s, 1H, H7), 10.05 (s, 1H, NH), 14.82 (s, 1H, OH); 13C NMR (75
MHz, DMSO-d6) 28.4 (2 × CH3), 44.1 (C1), 84.9 (C1′), 91.2 (C4),
104.7 (C5a), 108.0 (C13b), 114.3 (C12), 120.7 (C6a), 125.8 (C9),
127.5 (C7), 127.9 (C11), 129.2 (C13a), 130.0 (C10), 130.7 (C8), 137.0
(C7a), 138.3 (C11a), 139.6 (C12a), 163.1 (C3a), 166.4 (C5), 173.3
(C2), 183.1 (C6); EIMS m/z 343 [M]+; IR (KBr) 3054, 2966, 1646,
1595, 1509, 1162, 1074, 862; UV λ nm (MeOH) (log ꢀ) 231
(4.22), 284 (4.68), 316 (sh), 354 (3.91).
5-H yd r ox y-1,1,13-t r im e t h y l-2-m e t h y le n e -1,2-d ih y -
d r oben zo[b]fu r o[3,2-h ]a cr id in -6(13H)-on e (14). Compound
14 was prepared from 10 under conditions similar with those
described for the preparation of 13 from 10 (0.175 g, 0.5 mmol)
using dry N,N-dimethylformamide (10 mL), sodium hydride
(0.025 g of 50% oil dispersion, 0.5 mmol) and dimethyl sulfate
(0.15 mL, 1.6 mmol. Purification by flash chromatography
(solvent: cyclohexane then cyclohexane/acetone, 96:4 to 90:
10) gave 14 as a solid product (0.150 g, 82%): 1H NMR (300
MHz, CDCl3) 1.75 (s, 6H), 4.01 (s, 1H, NCH3), 4.40 (d, J ) 3
Hz, 1H, H1′a), 4.80 (d, J ) 3 Hz, 1H, H1′b), 6.32 (s, 1H, H4),
7.40 (td, J ) 8, 1 Hz, 1H, H9), 7.56 (td, J ) 8, 1 Hz, 1H, H10),
7.57 (s, 1H, H12), 7.80 (dd, J ) 8, 1 Hz, 1H, H11), 8.01 (dd, J )
8, 1 Hz, 1H, H8), 8.89 (s, 1H, H7), 15.42 (s, 1H, OH); 13C NMR
(75 MHz, CDCl3) 28.8 (2 × CH3), 43.4 (NCH3) 56.4 (C1), 83.9
(C1′), 97.5 (C4), 107.6 (C5a), 110.3 (C12 + C13b), 124.3 (C9), 124.4
(C6a), 125.9 (C7), 128.4 (C11), 128.8 (C10), 130.0 (C8), 130.9 (C7a),
135.8 (C11a), 136.2 (C12a), 140.6 (C13a), 160.9 (C3a), 164.1 (C5),
173.7 (C2), 179.5 (C6); CIMS m/z 358 [MH]+.
6-Meth oxy-3,3,14-tr im eth yl-3,14-d ih yd r o-7H-ben zo[b]-
p yr a n o[3,2-h ]a cr id in -7-on e (4). Compound 4 was obtained
from 9 (0.445 g, 1.3 mmol) according to the procedure described
for the preparation of 13, using N,N-dimethylformamide (20
mL), sodium hydride (0.155 g of 50% oil dispersion, 3.2 mmol)
and dimethyl sulfate (0.65 mL, 6.8 mmol). Silica gel column
chromatography (solvent: cyclohexane then cyclohexane/
acetone, 98:2 to 96:4) gave 4 (0.420 g, 94%) as small yellow
needles: mp 267-268 °C (CHCl3); 1H NMR (300 MHz, CDCl3)
1.56 (s, 6H, 2 × CH3), 3.90 (s, 3H, NCH3), 4.00 (s, 3H, OCH3),
5.54 (d, J ) 9 Hz, 1H, H2), 6.31 (s, 1H, H5), 6.58 (d, J ) 9 Hz,
1H, H1), 7.40 (td, J ) 8, 1.5 Hz, 1H, H10), 7.53 (td, J ) 8, 1.5
Hz, 1H, H11), 7.65 (s, 1H, H13), 7.86 (dd, J ) 8, 1.5 Hz, 1H,
H12), 8.10 (dd, J ) 8, 1.5 Hz, 1H, H9), 8.91 (s, 1H, H8); 13C
NMR (75 MHz, CDCl3) 26.8 (2 × CH3), 44.6 (NCH3), 56.2
(OCH3), 76.3 (C3), 93.7 (C5), 102.9 (C14b), 109.4 (C6a), 113.7 (C13),
121.9 (C1), 122.9 (C2), 124.3 (C10), 125.3 (C7a), 126.6 (C12), 127.9
(C8), 128.0 (C11), 128.4 (C8a), 129.4 (C9), 135.6 (C12a), 141.7
(C13a), 147.3 (C14a), 159.7 (C4a), 163.1 (C6), 177.9 (C7); CIMS
m/z 372 [MH]+; IR (NaCl) 3390, 2947, 1637, 1615, 1588, 1498,
1392, 1150, 1090, 808; UV λ nm (MeOH) (log ꢀ) 240 (3.95),
275 (4.23), 296 (sh), 307 (4.26), 362 (3.50).
5-Me t h ox y-1,1,13-t r im e t h yl-2-m e t h yle n e -1,2-d ih y -
d r oben zo[b]fu r o[3,2-h ]a cr id in -6(13H)-on e (15). Compound
15 was obtained from 10 (0.100 g, 0.29 mmol) according to
the procedure described for the preparation of 13, using N,N-
dimethylformamide (15 mL) sodium hydride (0.035 g of 50%
oil dispersion, 0.73 mmol) and dimethyl sulfate (0.16 mL, 1.75
mmol). Silica gel column chromatography (solvent: cyclohex-
ane then cyclohexane/acetone, 98:2 to 94:6) gave 15 (0.90 g,
83%) as a yellow amorphous solid: 1H NMR (300 MHz, CDCl3)
1.77 (s, 6H, 2 × CH3), 3.97 (s, 3H, NCH3), 4.00 (s, 3H, OCH3),
4.33 (d, J ) 3 Hz, 1H, H1′a), 4.70 (d, J ) 3 Hz, 1H, H1′b), 6.43
(s, 1H, H4), 7.41 (td, J ) 8, 1 Hz, 1H, H9), 7.55 (td, J ) 8, 1
Hz, 1H, H10), 7.65 (s, 1H, H12), 7.85 (dd, J ) 8, 1 Hz, 1H, H11),
8.00 (dd, J ) 8, 1 Hz, 1H, H8), 8.82 (s, 1H, H7); 13C NMR (75
MHz, CDCl3) 30.8 (2 × CH3), 45.9 (NCH3 + C1), 56.4 (OCH3),
83.0 (C1′), 89.3 (C4), 112.0 (C5a), 112.3 (C12), 113.1 (C13b), 124.5
(C9), 126.2 (C6a), 126.6 (C7), 127.6 (C11), 128.2 (C7a + C10), 128.7
6-Hyd r oxy-3,3,14-tr im eth yl-3,14-d ih yd r o-7H-ben zo[b]-
p yr a n o[3,2-h ]a cr id in -7-on e (13). Sodium hydride (0.5 g of
50% oil dispersion, 1 mmol) was added to an ice-cooled solution
of 9 (0.35 g, 1 mmol) in dry N,N-dimethylformamide (20 mL).
The mixture was stirred under nitrogen for 15 min at 0 °C
and dimethyl sulfate (0.28 mL, 3 mmol) was added. After 30

2400 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 12
Costes et al.
(C11a), 129.5 (C8), 135.6 (C12a), 142.6 (C13a), 162.7 (C5 + C3a),
173.4 (C2), 179.5 (C6); CIMS m/z 372 [MH]+; UV λ nm (MeOH)
(log ꢀ) 238 (4.09), 252 (sh), 282 (4.38), 344 (3.77).
washed with water (2 × 10 mL), and dried in vacuo over P2O5
to afford 17 (816 mg, 96.5%) as an amorphous yellow-green
solid: 1H NMR (300 MHz, CDCl3) 1.48 (s, 3H, CH3), 1.58 (s,
3H, CH3), 1.97 (s, 3H, CH3CO), 2.04 (s, 3H, CH3CO), 3.72 (s,
3H, NCH3), 4.03 (s, 3H, OCH3), 5.49 (d, J ) 5 Hz, 1H, H2),
6.30 (s, 1H, H5), 6.58 (d, J ) 5 Hz, 1H, H1), 7.42 (td, J ) 8, 2
Hz, 1H, H10), 7.53 (s, 1H, H13), 7.54 (td, J ) 8, 2 Hz, 1H, H11),
7.85 (dd, J ) 8, 2 Hz, 1H, H12), 8.02 (dd, J ) 8, 2 Hz, 1H, H9),
8.88 (s, 1H, H8); 13C NMR (75 MHz, CDCl3) 20.7 (CH3CO), 21.1-
(CH3CO), 23.4 (CH3), 24.5 (CH3), 43.0 (NCH3), 56.3 (OCH3),
65.7 (C1), 69.3 (C2), 76.6 (C3), 94.4 (C5), 97.8 (C14b), 111.6 (C6a
+ C13), 124.5 (C10), 125.8 (C7a), 126.7 (C12), 128.2 (C8), 128.3
(C11), 128.6 (C8a), 129.6 (C9), 135.8 (C12a), 142.3 (C13a), 150.3
(C14a), 160.2 (C4a), 162.9 (C6), 170.5 (CH3CO), 171.0 (CH3CO),
178.0 (C7); CIMS m/z 490 [MH]+; IR (KBr) 3448, 2924, 2851,
1751, 1651, 1621, 1588, 1492, 1238, 1198, 1086, 1029, 913, 813,
742; UV λ nm (MeOH) (log ꢀ) 237 (4.57), 257 (sh), 288 (4.97).
(+)-cis-6-Meth oxy-3,3,14-tr im eth yl-1,2-dipr opioxy-1,2,3,-
14-tetr ah ydr o-7H-ben zo[b]pyr an o[3,2-h ]acr idin -7-on e (18).
To a cooled solution (0 °C) of 16 (0.25 g, 0.62 mmol) in dry
pyridine (5 mL) was added propionic anhydride (1.6 mL, 12.3
mmol). The mixture was stirred at room temperature for 2
days and evaporated in vacuo. Column chromatography on
silica gel (solvent: cyclohexane then cyclohexane/acetone, 99:1
to 84:16) gave 18 (0.26 g, 81%) as bright yellow sheets: mp
202 °C (cyclohexane/acetone, 9:1); 1H NMR (300 MHz, CDCl3)
1.06 (m, 6H, 2 × CH3), 1.47 (s, 3H, CH3), 1.58 (s, 3H, CH3),
2.18 (q, J ) 8 Hz, 2H, CH2), 2.30 (m, 2H, CH2), 3.72 (s, 3H,
NCH3), 4.02 (s, 3H, OCH3), 5.51 (d, J ) 5 Hz, 1H, H2), 6.30 (s,
1H, H5), 6.60 (d, J ) 5 Hz, 1H, H1), 7.42 (td, J ) 8, 1.5 Hz,
1H, H10), 7.52 (s, 1H, H13), 7.55 (td, J ) 8, 1.5 Hz, 1H, H11),
7.84 (dd, J ) 8, 1.5 Hz, 1H, H12), 8.02 (dd, J ) 8, 1.5 Hz, 1H,
H9), 8.80 (s, 1H, H8); 13C NMR (75 MHz, CDCl3) 9.0 (2 × CH3
CH2), 23.5 (CH3), 24.5 (CH3), 27.3 (CH2), 27.8 (CH2), 44.1
(NCH3), 56.3 (OCH3), 65.6 (C1), 69.2 (C2), 76.6 (C3), 94.4 (C5),
98.0 (C14b), 111.2 (C6a), 111.7 (C13), 124.5 (C10), 125.8 (C7a),
126.7 (C12), 128.0 (C8), 128.2 (C11), 128.6 (C8a), 129.6 (C9), 135.7
(C12a), 142.3 (C13a), 150.3 (C14a), 160.3 (C4a), 162.8 (C6), 173.8
(COCH2), 174.3 (COCH2), 178.3 (C7); CIMS m/z 518 [MH]+;
IR (NaCl) 3450, 3000, 2980, 2940, 1745, 1650, 1620, 1590,
1490, 1460, 1400, 1200, 1155, 1085; UV λ nm (MeOH) (log ꢀ)
236 (4.42), 260 (sh), 288 (4.88), 335 (4.08).
(+)-cis-1,2-Diisova ler yloxy-6-m eth oxy-3,3,14-tr im eth yl-
1,2,3,14-tetr a h yd r o-7H-ben zo[b]p yr a n o[3,2-h ]a cr id in -7-
on e (19). To an ice-cooled solution of 16 (0.175 g, 0.43 mmol)
in dry pyridine (5 mL) was added isovaleryl chloride (0.5 mL,
4.16 mmol). The mixture was stirred for 15 min and evapo-
rated in vacuo. Column chromatography on silica gel (sol-
vent: cyclohexane then cyclohexane/acetone, 94:6 to 90:10)
gave 19 (0.23 g, 93%) as a yellow amorphous solid: 1H NMR
(300 MHz, CDCl3) 0.84-0.92 (m, 12H, 2 × (CH3)2), 1.44 (s, 3H,
CH3), 1.54 (s, 3H, CH3), 1.94-2.09 (m, 4H, 2 × CH, CH2), 2.15
(d, J ) 7 Hz, 2H, CH2), 3.70 (s, 3H, NCH3), 3.98 (s, 3H, OCH3),
5.49 (d, J ) 5 Hz, 1H, H2), 6.27 (d, J ) 5 Hz, 1H, H1), 6.61 (s,
1H, H5), 7.37 (td, J ) 8, 1.5 Hz, 1H, H10), 7.51 (td, J ) 8, 1.5
Hz, 1H, H11), 7.52 (s, 1H, H13), 7.79 (dd, J ) 8, 1.5 Hz, 1H,
H12), 7.98 (dd, J ) 8, 1.5 Hz, 1H, H9), 8.85 (s, 1H, H8); 13C
NMR (75 MHz, CDCl3) 22.2 (2 × (CH3)2), 23.8 (CH3), 24.2
(CH3), 24.9 (CH), 25.2 (CH), 42.8 (OCH2), 43.0 (OCH2), 43.2
(NCH3), 56.2 (OCH3), 65.3 (C1), 69.3 (C2), 76.4 (C3), 94.4 (C5),
98.2 (C14b), 110.0 (C6a), 111.8 (C13), 124.4 (C10), 125.6 (C7a),
126.5 (C12), 127.8 (C8), 128.1 (C11), 128.5 (C8a), 129.4 (C9), 135.6
(C12a), 142.2 (C13a), 150.2 (C14a), 160.3 (C4a), 162.7 (C6), 172.2
(C1OCO), 172.8 (C2OCO), 178.8 (C7); CIMS m/z 574 [MH]+; IR
(KBr) 3390, 3010, 2965, 1740, 1645, 1618, 1589, 1498, 1463,
1400, 1200, 1149, 1086; UV λ nm (MeOH) (log ꢀ) 237 (4.47),
260 (sh), 288 (4.91), 338 (4.11).
5-Me t h oxy-2,2,13-t r im e t h yl-2,13-d ih yd r o-6H -b e n zo-
[b]p yr a n o[2,3-i]a cr id in -6-on e (11) a n d 4-Meth oxy-3,3,-
12-t r im e t h y l-2-m e t h y le n e -2,3-d ih y d r o b e n zo [b ]fu r o -
[2,3-i]a cr id in -5(12H)-on e (12). Compounds 11 and 12 were
synthesized according to the procedure described for the
preparation of 4, from the mixture (0.65 g, 0.19 mmol)
of the two nonisolated linear products obtained in the course
of the synthesis of 9 using N,N-dimethylformamide (10 mL),
sodium hydride (0.023 g of 50% oil dispersion, 0.48 mmol)
and dimethyl sulfate (0.1 mL, 1.14 mmol). The crude product
was purified by silica gel column chromatography (solvent:
cyclohexane then cyclohexane/acetone, 99:1 to 98:2) to give
11 (0.039 g, 55%) and 12 (0.015 g, 22%) as solid products.
11: 1H NMR (300 MHz, CDCl3) 1.42 (s, 3H, CH3), 1.50 (s,
3H, CH3), 3.86 (s, 3H, NCH3), 4.00 (s, 3H, OCH3), 5.68 (d, J )
10 Hz, 1H, H3), 6.65 (s, 1H, H14), 6.81 (d, J ) 10 Hz, 1H, H4),
7.41 (td, J ) 8, 1.5 Hz, 1H, H9), 7.55 (td, J ) 8, 1.5 Hz, 1H,
H
10), 7.71 (s, 1H, H12), 7.88 (dd, J ) 8, 1.5 Hz, 1H, H11), 8.02
(dd, J ) 8, 1.5 Hz, 1H, H8), 9.03 (s, 1H, H7); 13C NMR (75 MHz,
CDCl3) 28.3 (2 × CH3), 34.5 (NCH3), 62.3 (OCH3), 77.5 (C2),
97.1 (C14), 109.1 (C5a), 109.8 (C12), 110.0 (C4a), 116.2 (C4), 123.7
(C6a), 124.1 (C9), 126.7 (C11), 127.8 (C7a), 128.0 (C3), 128.2 (C7),
128.7 (C10), 129.1 (C8), 135.5 (C11a), 138.8 (C12a), 146.4 (C13a),
157.7 (C14a), 160.6 (C5), 177.0 (C6); CIMS m/z 372 [MH]+; IR
(KBr) 3010, 2930, 1643, 1607, 1551, 1485, 1213, 1126, 1089,
776; UV λ nm (MeOH) (log ꢀ) 245 (4.33), 303 (4.90).
12: 1H NMR (300 MHz, CDCl3) 1.63 (s, 6H, 2 × CH3), 3.81
(s, 3H, NCH3), 4.03 (s, 3H, OCH3), 4.33 (d, J ) 3 Hz, 1H, H1′a),
4.73 (d, J ) 3 Hz, 1H, H1′b), 6.69 (s, 1H, H13), 7.39 (t, J ) 8 Hz,
1H, H8), 7.52 (t, J ) 8 Hz,1H, H9), 7.65 (s, 1H, H11), 7.82 (d, J
) 8 Hz, 1H, H10), 7.99 (d, J ) 8 Hz, 1H, H7), 9.01 (s, 1H, H6);
13C NMR (75 MHz, CDCl3) 29.2 (2 × CH3), 35.3 (NCH3), 43.9
(C3), 62.8 (OCH3), 83.4 (C1′), 91.0 (C13), 110.0 (C11), 111.1 (C4a),
120.6 (C3a), 124.0 (C5a), 124.4 (C8), 126.8 (C6), 128.1 (C6a), 128.3
(C10), 128.5 (C9) 129.3 (C7), 135.8 (C10a), 139.1 (C11a), 147.8
(C12a), 159.2 (C13a), 161.7 (C4), 172.1 (C2), 177.3 (C5); CIMS m/z
372 [MH]+.
(+)-cis-1,2-Dih ydr oxy-6-m eth oxy-3,3,14-tr im eth yl-1,2,3,-
14-tetr ah ydr o-7H-ben zo[b]pyr an o[3,2-h ]acr idin -7-on e (16).
Compound 4 (2 g, 5.39 mmol) was added to a solution of
osmium tetroxide (2.5% in 2-methyl-2-propanol) (3.8 mL) and
N-methylmorpholine N-oxide dihydrate (0.735 g, 5.4 mmol) in
t-BuOH/THF/H2O (10/3/1, v/v/v, 40 mL). The reaction mixture
was stirred at room temperature for 2 days. After addition of
saturated aqueous NaHSO3, the mixture was stirred for 1 h
and then extracted with CH2Cl2 (6 × 60 mL). The organic
layers were evaporated under reduced pressure. Flash chro-
matography (solvent: cyclohexane then cyclohexane/acetone,
95:5 to 85:15) afforded 16 (1.55 g, 71%) as yellow needles: mp
1
295 °C (recrystallized in CH2Cl2/acetone, 1:1); H NMR (300
MHz, DMSO-d6) 1.40 (s, 3H, CH3), 1.45 (s, 3H, CH3), 3.68 (t,
J ) 4.5 Hz, 1H, H-2), 3.81 (s, 3H, OCH3), 3.90 (s, 3H, NCH3),
4.62 (d, J ) 9 Hz, 1H, OH-C1), 5.07 (d, J ) 4.5 Hz, 1H, OH-
C2), 5.09 (dd, J ) 9, 4.5 Hz, 1H, H1), 6.18 (s, 1H, H5), 7.42 (td,
J ) 8, 1.5 Hz, 1H, H10), 7.57 (td, J ) 8, 1.5 Hz, 1H, H11), 7.90
(s, 1H, H13), 8.02 (dd, J ) 8, 1.5 Hz, 1H, H12), 8.09 (dd J ) 8,
1.5 Hz, IH, H9) 8.65 (s, 1H, H8); 13C NMR (75 MHz, DMSO-d6)
23.4 (CH3), 26.2 (CH3), 49.2 (NCH3), 56.9 (OCH3), 65.1 (C1),
71.2 (C2), 78.7 (C3), 94.5 (C5), 104.5 (C14b), 110.8 (C6a), 113.0
(C13), 125.3 (C10), 126.2 (C7a), 127.3 (C12), 128.0 (C8), 128.7 (C8a),
129.0 (C11), 130.2 (C9), 136.5 (C12a), 142.7 (C13a), 150.9 (C14a),
160.8 (C4a), 162.3 (C6), 177.4 (C7); CIMS m/z 406 [MH]+; IR
(NaCI) ν max cm-1 3385, 2920, 1635, 1600, 1585, 1500, 1390,
1090, 810;UV λ nm (MeOH) (log ꢀ) 236 (4.35), 286 (4.85), 345
(4.02).
(+)-cis-1-H yd r oxy-2-isova ler yloxy-6-m et h oxy-3,3,14-
tr im eth yl-1,2,3,14-tetr a h yd r o-7H-ben zo[b]p yr a n o[3,2-h ]-
a cr id in -7-on e (20). To an iced-cooled solution of 16 (0.120 g,
0.30 mmol) in dry pyridine (4 mL) was added isovaleryl
chloride (0.16 mL, 1.33 mmol). The reaction mixture was
stirred at 0 °C for 90 min and then evaporated under reduced
pressure (T < 40 °C). Flash chromatography (solvent: cyclo-
(+)-cis-1,2-Dia cetoxy-6-m eth oxy-3,3,14-tr im eth yl-1,2,3,-
14-tetr ah ydr o-7H-ben zo[b]pyr an o[3,2-h ]acr idin -7-on e (17).
An ice-cooled mixture of acetic anhydride (4 mL, 42 mmol) and
dry pyridine (4 mL) was added to 16 (700 mg, 1.73 mmol).
After stirring at room temperature for 1 week, the mixture
was poured on cold water (20 mL). The precipitate was filtered,

Benzopyranoacridinone Analogues of Acronycine
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 12 2401
hexane then cyclohexane/acetone, 94:6 to 90:10) gave 20 (0.126
g, 87%) as a yellow amorphous solid and a small amount of
the disubstituted derivative 19 (0.020 g, 12%). 20: 1H NMR
(300 MHz, CDCl3) 0.86-0.92 (m, 6H, (CH3)2), 1.49 (s, 3H, CH3),
1.54 (s, 3H, CH3), 2.02-2.17 (m, 2H, CH + OH), 2.32 (d, J )
7 Hz, 2H, CH2), 3.68 (s, 3H, NCH3), 3.90 (s, 3H, OCH3), 5.37
(m, 1H, H1), 5.48 (d, J ) 5 Hz, 1H, H2), 5.86 (s, 1H, H5), 7.39
(td, J ) 8, 1.5 Hz, 1H, H10), 7.50 (td, J ) 8, 1.5 Hz, 1H, H11),
7.59 (s, 1H, H13), 7.79 (dd, J ) 8, 1.5 Hz, 1H, H12), 8.01 (dd, J
) 8, 1.5 Hz, 1H, H9), 8.76 (s, 1H, H8); 13C NMR (75 MHz,
CDCl3) 22.2 (CH3), 22.4 (2 × CH3), 25.4 (CH3+CH), 42.2
(OCH2), 43.0 (NCH3), 55.7 (OCH3), 63.8 (C1), 71.5 (C2), 76.6
(C3), 93.5 (C5), 101.9 (C14b), 110.4 (C6a), 111.6 (C13), 124.2 (C10),
125.0 (C7a), 126.7 (C12), 127.8 (C8), 128.1 (C11), 128.3 (C8a), 129.4
(C9), 135.6 (C12a), 141.7 (C13a), 149.5 (C14a), 159.3 (C4a), 162.2
(C6), 173.1 (C2OCO), 177.9 (C7); CIMS m/z 490 [MH]+; IR (KBr)
3450, 3274, 2930, 1734, 1640, 1613, 1590, 1498, 1395, 1152,
1090, 812, 734, 668; UV λ nm (MeOH) (log ꢀ) 236 (4.39), 259
(sh), 287 (4.85), 343 (4.00).
Flash chromatography (solvent: cyclohexane then cyclohexane/
acetone, 98:2 to 85:15) gave 23 (0.058 g, 96%) as an amorphous
orange solid: 1H NMR (300 MHz, CDCl3) 1.52 (s, 3H, CH3),
1.65 (s, 3H, CH3), 1.87 (s, 3H, C1-OCOCH3), 3.72 (s, 3H,
NCH3), 4.06 (s, 3H, OCH3), 5.76 (d, J ) 5 Hz, 1H, H2), 6.38 (s,
1H, H5), 6.66 (d, J ) 5 Hz, 1H, H1), 7.37 (m, 3H, H10, H3′, H5′),
7.51 (m, 3H, H11, H4′, H13), 7.82 (d, J ) 8 Hz, 1H, H12), 7.85
(m, 2H, H2′, H6′), 7.99 (d, J ) 8 Hz, 1H, H9), 8.87 (s, 1H, H8);
13C NMR (75 MHz, CDCl3) 21.0 (CH3CO), 23.0 (CH3), 24.8
(CH3), 42.8 (NCH3), 56.3 (OCH3), 66.0 (C1), 69.6 (C2), 76.5 (C3),
94.1 (C5), 97.6 (C14b), 111.1 (C6a), 111.4 (C13), 124.4 (C10), 125.6
(C7a), 126.6 (C12), 128.0 (C8), 128.2 (C11), 128.4 (C3′, C5′), 128.7
(C1′), 129.5 (C9), 129.6 (C2′, C6′), 130.8 (C8a), 133.4 (C4′), 135.7
(C12a), 142.1 (C13a), 150.2 (C14a), 160.3 (C4a), 162.9 (C6), 165.8
(C2OCO), 171.0 (C1OCO), 178.3 (C7); CIMS m/z 552 [MH]+; IR
(KBr) 3390, 2930, 1751, 1717, 1646, 1619, 1588, 1498, 1461,
1397, 1281, 1196, 1086, 770, 720; UV λ nm (MeOH) (log ꢀ) 233
(4.39), 258 (sh), 288 (4.67), 340 (3.87).
(+)-cis-1,2-Di-O-car bon yl-1,2-dih ydr oxy-6-m eth oxy-3,3,-
14-tr im eth yl-1,2,3,14-tetr a h yd r o-7H-ben zo[b]p yr a n o[3,2-
h ]a cr id in -7-on e (24). To a solution of 16 (1.05 g, 2.6 mmol)
in 2-butanone (50 mL) was added N,N′-carbonyldiimidazole
(2.10 g, 12.3 mmol). The reaction mixture was refluxed for 2
h under argon and after cooling, 5% aqueous NaHCO3 (60 mL)
was added. The solution was extracted with EtOAc (3 × 50
mL) and the combined organic layers were dried over anhy-
drous Na2SO4, filtered and evaporated under reduced pressure.
Flash chromatography (solvent: cyclohexane then cyclohexane/
acetone, 98:2 to 96:4) afforded 24 (0.610 g, 55%) as a yellow
amorphous solid: 1H NMR (300 MHz, CDCl3) 1.47 (s, 3H, CH3),
1.61 (s, 3H, CH3), 3.98 (s, 3H, NCH3), 4.00 (s, 3H, OCH3), 4.84
(d, J ) 8 Hz, 1H, H2), 6.31 (s, 1H, H5), 6.33 (d, J ) 8 Hz, 1H,
H2), 7.43 (td, J ) 8, 2 Hz, 1H, H10), 7.56 (td, J ) 8, 2 Hz, 1H,
(+)-cis-2-Ben zoyloxy-1-h yd r oxy-6-m et h oxy-3,3,14-t r i-
m eth yl-1,2,3,14-tetr ah ydr o-7H-ben zo[b]pyr an o[3,2-h ]acr i-
d in -7-on e (21). To a solution of 16 (0.200 g, 0.49 mmol) in
dry pyridine (5 mL) was added benzoic anhydride (1.380 g,
5.72 mmol). The reaction mixture was stirred at room tem-
perature for 5 days. After evaporation of the reaction mixture
under reduced pressure, the residue was chromatographed on
a silica gel column (solvent: cyclohexane then cyclohexane/
acetone, 98:2 to 88:12) to give 21 (0.152 g, 61%) as a yellow
amorphous solid: 1H NMR (300 MHz, CDCl3) 1.48 (s, 3H, CH3),
1.58 (s, 3H, CH3), 3.00 (br. s, 1H, C1-OH), 3.88 (s, 3H, NCH3),
3.98 (s, 3H, OCH3), 5.46 (d, J ) 5 Hz, 1H, H1), 5.65 (d, J ) 5
Hz, 1H, H2), 6.26 (s, 1H, H5), 7.30 (m, 3H, H10, H3′, H5′), 7.43
(m, 2H, H11, H4′), 7.48 (s, 1H, H13), 7.65 (d, J ) 8 Hz, 1H, H12),
7.90 (m, 3H, H9, H2′, H6′), 8.72 (s, 1H, H8); 13C NMR (75 MHz,
CDCl3) 22.6 (CH3), 25.3 (CH3), 41.1 (NCH3), 56.0 (OCH3), 64.1
(C1), 72.6 (C2), 76.6 (C3), 93.5 (C5), 101.7 (C14b), 110.7 (C6a),
111.7 (C13), 124.2 (C10), 126.6 (C7a), 127.6 (C12), 127.9 (C8), 128.3
(C3′, C5′, C11), 129.0 (C1′), 129.3 (C9), 129.8 (C2′, C6′), 129.9 (C8a),
133.3 (C4′), 135.5 (C12a), 141.7 (C13a), 149.6 (C14a), 159.4 (C4a),
162.4 (C6), 166.3 (C2OCO), 178.1 (C7); CIMS m/z 510 [MH]+;
IR (KBr) 3400-3100, 2926, 1720, 1643, 1590, 1493, 1397, 1276,
1118, 707, 668; UV λ nm (MeOH) (log ꢀ) 232 (4.56), 258 (sh),
287 (4.87), 345 (4.07).
H
11), 7.68 (s, 1H, H13), 7.87 (dd, J ) 8, 2 Hz, 1H, H12), 8.01
(dd, J ) 8, 2 Hz, 1H, H9), 8.82 (s, 1H, H8); 13C NMR (75 MHz,
CDCl3) 21.9 (CH3), 24.3 (CH3), 44.3 (NCH3), 56.4 (OCH3), 71.0
(C1), 74.1 (C3), 78.8 (C2), 95.3 (C5), 97.5 (C14b), 111.6 (C6a),
112.6 (C13), 124.8 (C10), 126.0 (C7a), 126.8 (C12), 127.6 (C8), 128.4
(C11), 128.9 (C8a), 129.5 (C9), 135.6 (C12a), 142.3 (C13a), 150.2
(C14a), 153.4 (CO), 159.7 (C4a), 163.7 (C6), 178.6 (C7); CIMS m/z
432 [MH]+; IR (KBr) 3450, 2940, 1808, 1641, 1615, 1585, 1492,
1452, 1400, 1312, 1200, 1169, 1087, 980, 748; UV λ nm (MeOH)
(log ꢀ) 236 (4.57), 257 (sh), 288 (4.80), 335 (3.93).
(+)-cis-1-Acetoxy-2-isova ler yloxy-6-m eth oxy-3,3,14-tr i-
m eth yl-1,2,3,14-tetr ah ydr o-7H-ben zo[b]pyr an o[3,2-h ]acr i-
d in -7-on e (22). To an iced-cooled solution (0 °C) of 20 (0.086
g, 0.18 mmol) in dry pyridine (3 mL) was added acetic
anhydride (3 mL, 31 mmol). The reaction mixture was stirred
at room temperature during 3 days and evaporated under
reduced pressure (T < 40 °C). Flash chromatography (sol-
vent: cyclohexane/acetone, 94:6) gave 22 (0.070 g, 75%) as a
yellow amorphous solid: 1H NMR (300 MHz, CDCl3) 0.86 (m,
6H, (CH3)2), 1.47 (s, 3H, CH3), 1.59 (s, 3H, CH3), 1.95 (s, 3H,
CH3CO), 2.01 (m, 1H, CH), 2.17 (d, J ) 7 Hz, 2H, CH2), 3.70
(s, 3H, NCH3), 4.02 (s, 3H, OCH3), 5.50 (d, J ) 5 Hz, 1H, H2),
6.30 (s, 1H, H5), 6.56 (d, J ) 5 Hz, 1H, H1), 7.42 (td, J ) 8, 1.5
Hz, 1H, H10), 7.53 (s, 1H, H13), 7.55 (td, J ) 8, 1.5 Hz, 1H,
H11), 7.85 (dd, J ) 8, 1.5 Hz, 1H, H12), 8.02 (dd, J ) 8, 1.5 Hz,
1H, H9), 8.89 (s, 1H, H8); 13C NMR (75 MHz, CDCl3) 21.2 (CH3),
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+
CH2), 56.3 (OCH3), 65.9 (C1), 69.0 (C2), 76.4 (C3), 94.3 (C5),
97.8 (C14b), 110.2 (C6a), 111.6 (C13), 124.5 (C10), 125.8 (C7a),
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dry pyridine (2 mL) was added acetic anhydride (2 mL, 21
mmol). The reaction mixture was stirred at room tempera-
ture for 3 days and evaporated under reduced pressure.

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