(±)-3,4-Dihydroxy-8,9-methylenedioxypterocarpan and derivatives: Cytotoxic effect on human leukemia cell lines

Article abstract of DOI:10.1016/j.ejmech.2008.01.027

Naturally occurring pterocarpans 1a,b, pterocarpan 1c, isoflavane 2 and ortho-quinone 3 were synthesized in the racemic form and their cytotoxic effect was evaluated on the human leukemia cell lines K562 (resistant to oxidative stress), Lucena-1 (MDR phenotype) and HL-60. Ortho-quinone 3 (IC₅₀ = 1.5 μM, 1.8 μM and 0.2 μM, respectively) and catechol pterocarpan 1a (IC₅₀ = 3.0 μM, 3.7 μM and 2.1 μM, respectively) were the most active compounds on these cells and were also evaluated on other human leukemia cell lines (Jurkat and Daudi). Ortho-quinone 3 was 2 to 10 times more potent than pterocarpan 1a, depending on the cell line considered, however, showed a greater toxicity for lymphocytes activated by PHA.

Full text of DOI:10.1016/j.ejmech.2008.01.027

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European Journal of Medicinal Chemistry 44 (2009) 920e925
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Short communication
(ꢀ)-3,4-Dihydroxy-8,9-methylenedioxypterocarpan and derivatives:
Cytotoxic effect on human leukemia cell lines
Chaquip D. Netto a, Eduardo S.J. Santos b, Carolina Pereira Castro b, Alcides J.M. da Silva a,
Vivian M. Rumjanek b, , Paulo R.R. Costa
*
a,**
a Laborato´rio de Qu´ımica Bioorgaˆnica (LQB), Nu´cleo de Pesquisas de Produtos Naturais, Centro de Cieˆncias da Sau´de, Bloco H,
Universidade Federal do Rio de Janeiro, RJ 21941-590, Brazil
b Laborato´rio de Imunologia Tumoral, Instituto de Bioqu´ımica Me´dica, Centro de Cieˆncias da Sau´de, Bloco H,
Universidade Federal do Rio de Janeiro, RJ 21941-590, Brazil
Received 22 October 2007; received in revised form 10 January 2008; accepted 18 January 2008
Available online 2 February 2008
Abstract
Naturally occurring pterocarpans 1a,b, pterocarpan 1c, isoflavane 2 and ortho-quinone 3 were synthesized in the racemic form and their cy-
totoxic effect was evaluated on the human leukemia cell lines K562 (resistant to oxidative stress), Lucena-1 (MDR phenotype) and HL-60.
Ortho-quinone 3 (IC50 ¼ 1.5 mM, 1.8 mM and 0.2 mM, respectively) and catechol pterocarpan 1a (IC50 ¼ 3.0 mM, 3.7 mM and 2.1 mM, respec-
tively) were the most active compounds on these cells and were also evaluated on other human leukemia cell lines (Jurkat and Daudi). Ortho-
quinone 3 was 2 to 10 times more potent than pterocarpan 1a, depending on the cell line considered, however, showed a greater toxicity for
lymphocytes activated by PHA.
Ó 2008 Published by Elsevier Masson SAS.
Keywords: Pterocarpans; Oxa-Heck reaction; Cytotoxic activity; MDR phenotype; Human leukemia; Quinones
1. Introduction
(ꢁ)-1b, was isolated from Cladrastis platycarpa but its cyto-
toxic effect was not evaluated [11,12]. Maakian (þ)-1d was
also isolated from P. purpureus and showed to be less potent
than (þ)-1a for KB cells [9]. Compound (þ)-1e, recently iso-
lated from Platymiscium floribundum, induced apoptotic cell
death in HL-60 leukemia cells [13]. Pterocarpan (ꢀ)-1c was
not isolated from natural sources. Compounds 1a, 1d and 2
had been previously synthesized by our group [14,15],
whereas compounds 3 and 1c are new and 1b, although a nat-
ural product, has never been synthesized previously.
Independent of their mode of action, the cytotoxicity ex-
erted by anti-tumor compounds tends to involve the induction
of apoptosis. Therefore, tumor cells presenting various mech-
anisms capable of interfering with the apoptotic process are
more resistant to treatment. In the present work the cytotoxic
effect of compounds 1aed, 2 and 3 was evaluated on human
leukemia cell lines selected based on their special characteris-
tics. All compounds were tested on the K562 cell line, derived
from a chronic myeloid human erythroleukemia, its multidrug
Pterocarpans are isoflavonoids [1] isolated mainly from
Leguminosae. These compounds act as phytoalexins, being bi-
osynthesized as a defense mechanism of these plants against
pathogens [2]. Some phytoalexins, such as phaseollidin and
erybraedins A, B and C, possess relevant antibiotic properties
[3,4]. Compounds prenylated at the A-ring, such as cabene-
grins A-I and A-II [5], edunol [6] and analogues [7], are potent
neutralizers of the effects of snake venoms, acting through the
inhibition of phospholipases and proteases [7,8].
Pterocarpan (þ)-1a (Fig. 1), isolated from Petalostemon
purpureus, showed to be cytotoxic for KB cells, a human epi-
dermoid carcinoma cell line [9,10]. Its isomer, pterocarpan
* Corresponding author. Tel.: þ55 21 2562 6791; fax: þ55 21 2562 6512.
** Corresponding author.
E-mail address: lqb@nppn.ufrj.br (V.M. Rumjanek).
0223-5234/$ - see front matter Ó 2008 Published by Elsevier Masson SAS.
doi:10.1016/j.ejmech.2008.01.027

C.D. Netto et al. / European Journal of Medicinal Chemistry 44 (2009) 920e925
921
R1
R1
OR3
OR4
ClHg
HO
HO
R2
O
BnO
R2
O
HO
HO
O
i
H
+
6a
11a
O
H
H
R3
R4
H
4a, R1=OBn, R2=H
4b, R1=H, R2=OBn
4c, R1=R2=H
5a, R3+R4=CH2
O
(-)-1b
O
5b, R3=Bn, R4=Me
O
(+)-1a, R1=OH, R2=H, R3=R4=OCH2O
( )-1c, R1=OH, R2=H, R3=OH, R4=OMe
(+)-1d, R1=R2=H, R3=R4=OCH2O
R1
BnO
R2
O
O
(+)-1e, R1=OH, R2=H, R3= H, R4=OMe
4a
4b
4a
4c
+
+
+
+
5a
5a
5b
5a
6a (56%)
6b (50%)
6c (50%)
6d (53%)
H
O
O
OH
H
H
( )-6
OR3
OR4
2
O
HO
O
1
H
( )-3
H
O
O
6a, R1=OBn, R2=H, R3=R4=CH2 6c, R1=OBn, R2=H, R3=Bn, R4=Me
O
HO
( )-2
O
6b, R1=H, R2=OBn, R3=R4=CH2 6d, R1=R2=H, R3=R4=CH2
O
i, PdCl2 / LiCl, acetone, r.t.
Fig. 1. Pterocarpans 1aee, isoflavane 2 and ortho-quinone 3.
Scheme 1. Synthesis of benzylated pterocarpans 6aed.
resistant counterpart K562-Lucena-1 cell line and HL-60, de-
rived from a pro-myelocytic leukemia. The more active com-
pounds were also tested on lymphoid cell lines: Daudi,
a Burkitt’s lymphoma, and Jurkat, derived from T lymphoblas-
tic leukemia. These cell lines show varying resistance to oxi-
dative stress (Table 1).
prepare quinones through the oxidation of 1a,b,d (Scheme 2)
[33]. In the presence of excess of DDQ, 1a was transformed
into ortho-quinone 3, but under the same conditions 1b led
to a non-identified mixture of products, while 1d led to the
corresponding coumestan (not shown).
3. Results and discussion
2. Chemistry
The cytotoxic effect of compounds 1aed, 2 and 3 on
leukemic cells is summarized in Table 2. The pterocarpan 1a
exhibited antiproliferative activity on K562 (IC50 ¼ 3.0 mM),
Lucena-1 (IC50 ¼ 3.7 mM) and HL-60 (IC50 ¼ 2.1 mM) to
a similar extent. In contrast, 1b and maakian 1d were inactive
on those cell lines (IC50 w 20e50 mM). Pterocarpan 1c and
isoflavane 2 were almost inactive compared to 1a on K562
and Lucena-1 cells (IC50 w 10e20 mM), however, were active
in HL-60 cells (IC50 ¼ 6.4 mM and 5.7 mM, respectively),
a much more sensitive cell line. The ortho-quinone 3 was
twice as effective compared to compound 1a on K562
(IC50 ¼ 1.5 mM) and Lucena-1 (IC50 ¼ 1.8 mM) and almost
10 times more active on HL-60 (IC50 ¼ 0.2 mM).
Compounds 1a,d and 2 were prepared in the racemic form,
as previously described by our group [14, 15], while the
synthesis of catechol pterocarpans 1b,c and ortho-quinone 3
is reported herein for the first time. The benzylated pterocar-
pans 6aed, intermediates required to prepare these target
compounds, were synthesized through a PdCl2 mediated oxa-
Heck or oxy-arylation reaction [25] between chromens 4aec
and organomercurials 5a,b in moderated yields (Scheme 1)
[14,15,26,27].
Debenzylation of 6aed with H2/PdeC (3 atm) led to the
pterocarpans 1aed in excellent yields (Scheme 2). In the pres-
ence of excess of Pd/C the benzylic CeO bond in 6a was also
cleaved and isoflavane 2 was formed in quantitative yield.
Once phenols and catechols can be oxidized to quinones in
biological medium, acting as pro-drugs [28e32], we tried to
The cytotoxic effect of the more active compounds, 1a and
3, was also studied in Jurkat and Daudi cells (Table 2).
Compound 1a did also show a potent effect on Daudi cell lines
(IC50 ¼ 2.8 mM) being w2 times less active on Jurkat cells
(IC50 ¼ 7.6 mM). As mentioned in Section 1, Jurkat cells
present a high expression of Bcl-2, which confers a certain de-
gree of resistance to mitochondria induced oxidative stress.
The compound 3, already shown to be more active than 1a
on K562, Lucena-1 and HL-60 cells, was also nearly 3e9-
fold more potent on Jurkat (IC50 ¼ 1.9 mM) and Daudi
(IC50 ¼ 0.9 mM) cell lines.
Table 1
Cell line panel
Cell lines Characteristics
Response to
oxidative stress
References
K562
High levels of intracellular GSH Resistant
High levels of catalase
[16,17]
[18,19]
Lucena-1 Overexpression of P-glycoprotein Resistant
Increased levels of catalase
However, as shown in Fig. 2, despite the fact that com-
pound 3 was very active against leukemia cells it presented
high toxicity against normal lymphocytes (IC50 ¼ 2.4 mM) ac-
tivated by the mitogen phytohemaglutinin (PHA). In contrast,
pterocarpan 1a, although less potent for leukemia cells, was 10
HL-60
Daudi
Jurkat
Moderate levels of Bcl-2
No expression of Bcl-2
High levels of Bcl-2
Sensitive
Sensitive
Moderately
resistant
[16,20,21]
[22]
[23,24]

922
C.D. Netto et al. / European Journal of Medicinal Chemistry 44 (2009) 920e925
R1
R1
BnO
O
HO
O
i
H
H
R2
R2
H
( )-6
H
( )-1
OR3
OR4
O
OR3
OR4
O
6a, R1=OBn, R2=H, R3=R4=CH2
6b, R1=H, R2=OBn, R3=R4=CH2
6c, R1=OBn, R2=H, R3=Bn,R4=Me
6d, R1=R2=H, R3=R4=CH2
1a, R1=OH, R2=H, R3=R4=CH2 (100%)
1b, R1=H, R2=OH, R3=R4=CH2 (95%)
1c, R1=OH, R2=H, R3=H,R4=Me (95%)
1d, R1=R2=H, R3=R4=CH2 (90%)
ii from 6a
iii
from 1a
O
OH
O
O
HO
O
H
H
H
O
O
HO
O
( )-2
100%
( )-3
71%
O
O
i, H2 (3 atm), Pd-C (10%), acetone; ii, H2 (3 atm),
Pd-C(excess), acetone; iii, DQQ, CH2Cl2
Scheme 2. Transformation of 6a-d into the target compound 1aed, 2 and 3.
times less toxic for lymphocytes when compared to 3
(IC50 ¼ 24.1 mM).
catechol group at the A-ring like in 1a, the presence of a polar
phenol group at the D-ring led to a decrease in the cytotoxic
effect on K562 and Lucena-1 cells. Due to the cis-fusion be-
tween B and C rings, compound 1a is conformationally con-
strained, while in isoflavane 2, inactive on the K562 and
Lucena-1 cell lines, the D-ring is conformational free. How-
ever, these compounds were active against the oxidative stress
sensitive cell HL-60.
It has been shown that ortho-quinones can be reduced to the
corresponding semiquinones radical by P450 reductases,
leading to the formation of reactive oxygen species [34e36].
However, ortho-quinone 3 was very active on either oxidative
stress resistant or sensitive cell lines. As the Cb (C1) in 3 is
highly electrophilic, this ortho-quinone could act as a Michael
acceptor and we would like to suggest this as an alternative
mechanism of action.
Among the pterocarpans, the potency on leukemia cells was
dependent on the pattern of substitution at the A- and D-rings.
Since 1a was active on K562 and Lucena-1, cell lines very re-
sistant to the oxidative stress, a mechanism of action through
the redox cycle seems unlikely. It has been suggested that or-
tho-quinones are formed by oxidation of catechols and these
metabolites are responsible for the toxicity of these com-
pounds [28e31]. However, when comparing IC50 towards
lymphocytes, this conversion seems unlikely. Should this
mechanism be operating, similar levels of toxicity should be
expected. When the position of the catechol group in A-ring
was changed (1b), the activity on all cell lines studied was
abolished. In addition, the absence of the catechol group on
maakian (1d) dramatically reduced the effect on all cell lines
tested, confirming the importance of this group for the
cytotoxic effect. On the other hand, although 1c has the
4. Conclusions
The cytotoxic effect shown by compound 1a toward several
human leukemia cell lines, including K562 (oxidative stress
resistant), Lucena-1 (multidrug resistance phenotype e
MDR) and, to a lesser extent, Jurkat (Bcl-2 high), in addition
to its low toxicity against lymphocytes activated by PHA,
make this compound an attractive target. Furthermore, multi-
drug resistance is the major cause of chemotherapy failure
in our days and we present evidence, herein, that MDR cells
overexpressing Pgp are sensitive to compound 1a, suggesting
it is not a substrate to this pump. On the other hand, compound
3, despite its high potency and broad spectrum of anti-tumor
activity, probably could not be used in humans because of
its high toxicity.
Table 2
Cytotoxic effect (IC50, mM) of compounds 1aec, 2 and 3 on human leukemia
cell lines
1a
1b
1c
1d
2
3
Compounds (IC50, mM)a
K562
3.0
3.7
2.1
7.6
2.8
>20
>50
>20
nd
>10
>20
6.4
nd
>50
>50
>50
nd
>10
>20
5.7
nd
1.5
1.8
0.2
1.9
0.9
Lucena I
HL-60
Jurkat
Daudi
nd
nd
nd
nd
a
Effect of compounds 1aed, 2 and 3 on the viability of various leukemic
cell lines was determined by MTT assay 72 h after incubation. Each point
of the experiments was performed in triplicate and results are expressed as
the mean of at least three experiments. nd (not done).

C.D. Netto et al. / European Journal of Medicinal Chemistry 44 (2009) 920e925
923
Compound 1a
Compound 3
100
50
0
100
50
0
PHA CTR
2.5
3.75
5.0
7.5
10
PHA CTR
2.5
3.75
5.0
7.5
10
PHA
PHA
Drug concentration (µM)
Fig. 2. Effect of compounds 1a and 3 on the viability of normal human peripheral lymphocytes. Viability was determined by MTT assay 72 h after incubation.
Lymphocytes were stimulated with the mitogen PHA (5 mg/mL). CTR e control cells were treated with diluent and no PHA. Each point of the experiment was
performed in triplicate and results are expressed as the mean þ SD of at least three experiments.
5. Experimental protocols
5.1.4. Cell viability
Cell viability was accessed by MTT colorimetric assay.
MTT is a substance capable of being reduced by dehydroge-
nase enzymes present inactive mitochondria of living cells.
After 72 h of incubation 20 mL of MTT (5 mg/mL) were added
to each well. Plates were kept at 37 ꢃC, 5% CO2 for 3 h. After
centrifugation, 200 mL DMSO was added to all wells in order
to dissolve the dark blue crystals formed by the reduction of
MTT. Absorbance was then read in an ELISA reader at wave-
length of 490 nm. The absorbance was directly proportional to
the amount of formazan (reduction product) present, indicat-
ing the percentage of living cells. All drugs remained in the
media during incubation.
5.1. Biology
5.1.1. Cell lines
Human leukemic cell lines: Jurkat, Daudi, HL-60, K562
and its resistant variant, Lucena I, were all maintained in
RPMI 1640 medium, supplemented with 5 ꢂ 10ꢁ5 M b-mer-
captoethanol, 25 mM Hepes, pH adjusted to 7.4 with NaOH,
60 mg/L penicillin, 100 mg/L streptomycin and 10% fetal
calf serum (FCS), inactivated at 56 ꢃC for 1 h. Daudi cells
were supplemented with 20% fetal calf serum (FCS). Lucena
I cultures had also 60 nM of vincristine sulfate added in order
to maintain the resistant phenotype. All cells, except Jurkat,
were passaged at a concentration of 2 ꢂ 104 cells/mL after 3
days in culture and kept at 37 ꢃC in 5% CO2 humidified envi-
ronment. Jurkat cells were passaged at a concentration of
106 cells/mL.
5.2. Chemistry
Column chromatography was performed on silica gel
230e400 mesh (Aldrich). 1H NMR and 13C NMR spectra
were recorded on a Varian Gemini 200 and Bruker ARX
400 instruments using tetramethylsilane (TMS) as standard,
CDCl3 and acetone-d6 as solvents. J values are given in Hertz.
5.1.2. Preparation of peripheral blood mononuclear cells
Peripheral blood mononuclear cells (PBMC) were obtained
by fractionating heparinized blood from healthy volunteers on
ficoll-hypaque (Hystopaque), density gradient centrifugation.
The PBMC fraction was washed twice and resuspended in
RPMI 1640, supplemented as described above. The cell num-
ber was adjusted at 106 cells/mL and incubated with 5 mg/mL
of the mitogen PHA, in the presence or absence of compounds
being tested.
5.2.1. Oxy-Heck reaction between 4b and 5a:
synthesis of 6b
To a mixture of PdCl2 (87 mg, 0.49 mmol) and LiCl
(42 mg, 1.0 mmol) in acetone (5 mL) was added chromen 4b
(158 mg, 0.46 mmol) in acetone (10 mL). This mixture was
stirred for 15 min at 0 ꢃC and then 2-chloromercurio-4,5-
methylenedioxyphenol 5a (172 mg, 0.42 mmol) in acetone
(10 mL) was added. The suspension thus obtained was stirred
for 12 h at 25 ꢃC. After this time, brine (150 mL) was added to
it and the mixture was extracted with acetyl acetate
(3 ꢂ 50 mL), the organic extract dried (Na2SO4), and submit-
ted to column chromatography to give the compound 6b as
a solid (101.0 mg, 50%).
5.1.3. Treatment with the different compounds
Cell lines were exposed to the compounds 1e3 (0.1e
50 mM) in culture for 72 h. Briefly, 2 ꢂ 104 cells/mL were
seeded in 96 well microtiter plates in drug-free medium or
in medium containing different concentrations of compounds
1e3 and kept for 72 h at 37 ꢃC in an atmosphere of 5%
CO2. After that period cell viability was measured.
1H NMR d 7.37 (10H, m), 7.07 (1H, s), 6.70 (1H, s), 6.53
(1H, s), 6.43 (1H, s), 5.90 (1H, d, J ¼ 5.49 Hz), 5.89 (1H, d,
J ¼ 5.49 Hz), 5.41 (1H, d, J ¼ 6.87 Hz), 5.13 (2H, s), 5.11

924
C.D. Netto et al. / European Journal of Medicinal Chemistry 44 (2009) 920e925
(2H, s), 4.18 (1H, dd, J ¼ 10.8, 4.63 Hz), 3.59 (1H, t,
J ¼ 10.75 Hz), 3.46 (1H, m).
IR (KBr) nmax/cmꢁ1: 3392 (OH), 2923 (aromatic H),
1629e1602 (aromatic ring).
13C NMR d 153.90 (C), 150.53 (C), 150.23 (C), 147.84 (C),
143.71 (C), 141.82 (C), 137.15 (C), 136.56 (C), 128.31e
126.97 (10 CH), 117.67 (C), 116.60 (CH), 111.31 (C),
104.51 (CH), 103.18 (CH), 101.06 (CH2), 93.53 (CH), 78.30
(CH), 72.01 (CH2), 70.59 (CH2), 66.31 (CH2), 40.00 (CH).
5.2.5. Hydrogenolysis of 6a: synthesis of 2
A solution of cis-(ꢀ)-3,4-di-O-benzyl-pterocarpan 6a [24]
(31.8 mg ¼ 0.07 mmol) in acetone (5 mL) was hydrogenated
(3 atm) in the presence of PdeC (100% by weight). After
3 h the catalyst was filtered and the reaction mixture was con-
centrated in vacuo to furnish 2 (21.0 mg, 0.07 mmol) in 100%
5.2.2. Oxa-Heck reaction between 4b and 5b:
synthesis of 6c
1
yield. H NMR (CDCl3, 200 MHz): d 6.7 (1H, s, aromatic),
6.52 (1H, s), 6.46 (1H, d, J ¼ 8.33 Hz), 6.38 (1H, d,
J ¼ 8.33 Hz), 5.87 (2H, dd, J ¼ 2.1 Hz, 1.0 Hz), 4.28 (1H,
ddd, J ¼ 1.70 Hz, 3.48 Hz, 10.21 Hz), 4.04 (1H, t,
J ¼ 10.0 Hz), 3.54 (1H, m), 2.9 (2H, m). 13C NMR (CDCl3,
100 MHz): d 32.69 (CH) 70.42 (CH2), 98.57 (CH), 101.70
(CH2), 107.74 (CH). 108.69 (CH), 114.84 (C), 119.90 (C),
120.34 (CH), 133.69 (C), 141.77 (C), 143.56 (C), 144.61
(C), 147.27 (C), 150.33 (C).
To a mixture of PdCl2 (98 mg, 0.56 mmol) and LiCl
(47 mg, 1.12 mmol) in acetone (5 mL) was added chromen
4b (193 mg, 0.56 mmol) in acetone (10 mL). This mixture
was stirred for 15 min at 0 ꢃC and then 2-chloromercurio-4-
benzyloxy,5-methoxyphenol 5b (250 mg, 0.56 mmol) in ace-
tone (10 mL) was added. The suspension thus obtained was
stirred for 12 h at 25 ꢃC. After this time, brine (150 mL) was
added to it and the mixture was extracted with acetyl acetate
(3 ꢂ 50 mL), the organic extract dried (Na2SO4), and submit-
ted to column chromatography to give the compound 6c as
a solid (160.6 mg, 50%).
1H NMR (CDCl3) d 7.45e7.25 (m, 15H), 7.17 (d,
J ¼ 8.43 Hz, 1H), 6.81 (s, 1H), 6.69 (d, J ¼ 8.42 Hz, 1H),
6.51 (s, 1H), 5.46 (d, J ¼ 6.23 Hz, 1H), 5.13 (s, 2H), 5.11 (s,
2H), 5.04 (s, 2H), 4.22 (m, 1H), 3.83 (s, 3H), 3.51 (m, 2H).
13C NMR (CDCl3) d 39.99 (CH), 55.92 (CH3), 66.43
(CH2), 70.86 (CH2), 72.70 (CH2), 74.99 (CH2), 78.12 (CH),
95.62 (CH), 107.80 (CH), 112.85 (CH), 114.39 (C), 116.79
(C), 125.37 (CH), 127.14e128.31 (15 CH), 136.65 (C),
136.73 (C), 137.27 (C), 137.42 (C), 142.31 (C), 149.74 (C),
151.20 (C), 152.67 (C), 154.30 (C).
5.2.6. Oxidation of 1a: synthesis of 3
To a solution of 1a (24.7 mg, 0.08 mmol) in methylene chlo-
ride (25 mL) was added DDQ (four portions of 20.85 mg,
0.37 mmol) at room temperature. After 24 h the reaction was
quenched with brine and extracted with ethyl acetate, dried
with sodium sulfate and concentrated. Flash chromatography
(50:50 EtOAc/hexane) furnished a yellow solid (17.9 mg,
0.06 mmol) in 71% yield. The chemical shifts were based on
1
COSY spectrum. H NMR (CDCl3 6.96 (d, 2H, J ¼ 9.52 Hz),
200 MHZ), 6.49 (s, 1H), 6.41 (s, 1H), 6.15 (d, 1H, J ¼ 10.26
Hz), 5.89 (d, 1H, J ¼ 4.40 Hz), 5.88 (d, 1H, J ¼ 4.76 Hz),
4.72 (d, 1H, J ¼ 8.79), 4.30 (dd, 1H, J ¼ 8.97, 2.38), 3.28e
3.22 (m, 1H). 13C NMR (CDCl3, 400 MHz): d 69.31(CH),
165.50 (CH), 150.27 (CH), 135.61 (CH), 128.79 (CH2),
5.2.3. Hydrogenolysis of 6b: synthesis of 1b
128.05 (CH), 101.31 (CH2), 67.05 (CH); IR (KBr) nmax
/
(ꢀ)-2,3-di-O-benzyl-pterocarpan 6b (31.8 mg, 0.07 mmol)
in acetone was hydrogenated (3 atm) in the presence of Pde
C (10% by weight). After 30 min the catalyst was filtered to
give 1b (21.0 mg) in 95% yield.
cmꢁ1: 1689 (C]O), 1638 (C]O), 1484e1384 (aromatic
ring).
1H NMR: 6.91 (s, 1H), 6.87 (s, 1H), 6.38 (s, 1H), 6.37 (s,
1H), 5.91 (2d, J ¼ 5.49 Hz, 2H), 5.44 (d, J ¼ 6.59 Hz, 1H),
4.21 (dd, J ¼ 8.42 Hz and 2.93 Hz, 1H), 3.57 (m, 2H).
13C NMR: 41.25 (CH), 67.09 (CH2), 79.52 (CH), 93.90
(CH), 102.07 (CH2), 104.31 (CH), 105.89 (CH), 112.11
(CH), 117.01 (C), 119.55 (C), 140.81 (CH), 142.38 (C),
147.63 (C), 148.83 (C), 150.19 (C), 155.26 (C).
Acknowledgments
Our research was supported by grants from FINEP,
Programa de Oncobiologia FAF/FECD, PRONEX, FAPERJ,
CNPq and CAPES. C.D.N. and P.R.R.C. are supported by
CNPq fellowship and E.S.J.S. was partly supported by FAF/
FECD fellowship and now by CAPES. We are grateful to
Dr. Ottilia R. Affonso-Mitidieri for useful suggestions and
IR (KBr) nmax/cmꢁ1: 3369 (OH), 2924 (aromatic H),
1674e1602 (aromatic ring).
´
Central Analıtica NPPN-UFRJ for the analytical data.
References
5.2.4. Hydrogenolysis of 6c: synthesis of 1c
(ꢀ)-2,3-di-O-benzyl-pterocarpan 6c (35.0 mg, 0.06 mmol)
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