Russujaponols A-F illudoid sesquiterpenes from the fruiting body of Russula japonica

Article abstract of DOI:10.1021/np068006a

Six new illudoid Sesquiterpenes, russujaponols A-F (1-6), were isolated from the fruiting bodies of Russula japonica Hongo. Their structures were established primarily by 2D NMR experiments, and the structure of the main compound, russujaponol A (1) was confirmed by X-ray crystallographic analysis of its benzoate (1a). Russujaponol A (1) suppressed invasion of human fibrosarcoma (HT1080) cells into Matrigel in a concentration-dependent manner and caused 63% inhibition at 3.73 μM.

Full text of DOI:10.1021/np068006a

J. Nat. Prod. 2006, 69, 1267-1270
1267
Russujaponols A-F, Illudoid Sesquiterpenes from the Fruiting Body of Russula japonica
Kazuko Yoshikawa,* Azusa Kaneko, Yuki Matsumoto, Hiroshi Hama, and Shigenobu Arihara
Faculty of Pharmaceutical Sciences, Tokushima Bunri UniVersity, Yamashiro-Cho, Tokushima 770-8514, Japan
ReceiVed March 6, 2006
Six new illudoid sesquiterpenes, russujaponols A-F (1-6), were isolated from the fruiting bodies of Russula japonica
Hongo. Their structures were established primarily by 2D NMR experiments, and the structure of the main compound,
russujaponol A (1), was confirmed by X-ray crystallographic analysis of its benzoate (1a). Russujaponol A (1) suppressed
invasion of human fibrosarcoma (HT1080) cells into Matrigel in a concentration-dependent manner and caused 63%
inhibition at 3.73 µM.
In the course of our program aimed at the discovery of
biologically active compounds from fungi,1,2 we have initiated an
investigation of Russula japonica Hongo (Russulaceae),3 which
grows in colonies in broad-leaved forests throughout Japan. In this
study, six new illudoid sesquiterpenes, russujaponols A-F (1-6),
together with the known compound 4b4 and deliquinone,5 were
isolated from the fruiting bodies of R. japonica. We describe here
the isolation and structure elucidation of 1-6, primarily by extensive
NMR and X-ray crystallographic analysis of the benzoate of 1 (1a).
Their cytotoxic activities against a disease-oriented panel of 39
human cancer cell lines were investigated.
Russujaponol B (2) showed an [M + Na]+ peak at m/z 317.1732
in its HRFABMS, indicative of the molecular formula C17H26O4,
requiring five unsaturation equivalents. The IR spectrum of 2
indicated the hydroxy (3370 cm-1) and acetoxy (1730 and 1245
cm-1) functionalities. The HMQC spectrum of 2 showed the
presences of two hydroxy groups [δC 71.3 (t), 87.7 (s)], one
secondary acetoxy group [δH 2.03 (3H, s), δC 20.7, 171.2, δH 5.54
(1H, br s), δC 78.8 (d)], one tetrasubstituted double bond [δC 140.3
(s) and 122.8 (s)], and one vinylic methyl group [δH 1.70 (br s), δC
13.0 (s)]. Combined analysis of COSY, HMQC, and HMBC spectra
enabled the assignment of all the functional groups as in 1 (Figure
2). The COSY correlations showed the connectivity due to two
vicinal couplings, H2-1/H-2 and H2-4/H2-5, an allylic coupling, H-8/
H3-13, and a homoallylic coupling, H2-5/H3-13. HMBC long-range
correlations from H3-12 (δ 1.14) to C-2 (δ 57.0), C-3 (δ 45.1),
C-4 (δ 37.3), and C-6 (δ 140.3), from H3-13 (δ 1.70) to C-6, C-7
(δ 122.8), and C-8 (δ 78.8), from H3-15 (δ 1.54) to C-1 (δ 37.5),
C-10 (δ 48.4), C-11 (δ 44.8), and C-14 (δ 71.3), from H-2 [δ 2.76
(dd, J ) 12.6, 7.7)] to C-8 and C-9 (δ 87.7), and from H-8 (δ
5.54) to the carbonyl (δ 171.2) of the acetoxy group revealed three
methyl groups at C-3, C-7, and C-11, one primary hydroxy group
at C-14, one hydroxy group at C-9, one acetoxy group at C-8, an
ethylene bridge at C-3 and C-6, and the C-6-C-7 double bond.
Thus, the planar structure of 2 was determined to be 4a-hydroxy-
6-(hydroxymethyl)-3,6,7b-trimethyl-2,4,4a,5,6,7,7a,7b-octahydro-
1H-cyclobuta[e]inden-4-yl acetate. The relative configuration of the
chiral centers in 2 was established by a ROESY experiment.
Significant NOE correlations between H-2/H-1â (δ 1.63), H3-15
and between H3-12/H2-1, H-8 indicated the â-cis A/B junction, the
R-orientations of H3-12 and the C-14 hydroxymethyl, and the
â-orientation of the acetoxy moiety at C-8. On the basis of the
above findings and the fact that 2 was isolated in conjunction with
1, the structure of 2 was established as shown in Figure 1.
Results and Discussion
Russujaponol A (1) gave an [M + Na]+ peak at m/z 291.1562
(HRFABMS), which corresponds to the molecular formula C15H24O4,
requiring four unsaturation equivalents. The IR spectrum of 1
showed absorptions at 3370 (OH) and 1710 (CdO) cm-1. The 1H
NMR spectrum of 1 exhibited two methyl singlets at δ 1.80 and
1.54, one methyl doublet at δ 1.42 (d, J ) 6.3 Hz), and one
oxygenated methylene group at δ 3.62 and 3.59 (each d, J ) 10.2
Hz). The 15 carbon signals in the 13C NMR spectrum were sorted
by DEPT experiment into three methyls, five methylenes, one of
which is oxygen bearing (δ 70.1); two methines, four sp3 quaternary
carbons, two of which have oxygen substituents (δ 87.5 and 78.3);
and one carbonyl carbon (δ 214.3) (Table 1). Combined analysis
of COSY, HMQC, and HMBC spectra, together with the chemical
shifts and coupling constants, enabled the assignment of all the
functional groups on the protoilludane skeleton. As shown in Figure
2, the COSY spectrum revealed the connectivity of H2-4/H2-5, H-7/
H3-13, and H-9/H2-10. Moreover, HMBC correlations from H3-12
(δ 1.80) to C-2 (δ 87.5), C-3 (δ 52.3), C-4 (δ 24.4), and C-6 (δ
78.3), from H3-13 (δ 1.42) to C-6 (δ 78.3), C-7 (δ 48.1), and C-8
(δ 214.3), from H3-15 (δ 1.54) to C-1 (δ 47.3), C-10 (δ 40.5),
C-11 (δ 46.6), and C-14 (δ 70.1), and from H-9 [δ 3.53 (dd, J )
10.9, 6.0)] to C-2 and C-8 revealed three methyl groups at C-3,
C-7, and C-11, one primary hydroxy group at C-14, two tertiary
hydroxy groups at C-2 and C-6, one carbonyl group at C-8, and an
ethylene bridge at C-3 and C-6. Thus, the planar structure of 1
was determined as 2a,7a-dihydroxy-6-(hydroxymethyl)-3,6,7b-
trimethyloctahydro-1H-cyclobuta [e]inden-4(2H)-one. The relative
configuration of the six successive chiral centers at C-2, C-3, C-6,
C-7, C-9, and C-11 in 1 was defined by the following NOE analysis.
The NOEs between H-9/H-4a (δ 1.60), H3-15, H3-12/H2-1 (δ 2.81,
2.01), H-1R (δ 2.81)/H-7 (δ 3.75), H2-14 (δ 3.59, 3.62), and H3-
13/H2-5 (δ 2.19) established the 2R*, 3S*, 6R*, 7R*, 9R*, and 11S*
configurations. The X-ray crystallographic analysis6,7 of the ben-
zoate (1a) of 1 confirmed the proposed structure and established
the absolute configuration at the six stereocenters (Figure 3).
Russujaponol C (3) has the molecular formula C15H24O2,
requiring four unsaturation equivalents, by the 13C NMR data and
HREIMS. The IR spectrum of 3 also showed absorptions due to
hydroxy functions. The NMR data of 3 showed a close relationship
to that of 2, except for the absence of the acetyl signal at δ 2.03
1
and of the tertiary hydroxy resonance at δ 87.7 in 2. The H and
13C NMR spectra of 3 indicated the characteristic signals due to
two hydroxy groups [δC 73.4 (d), δH 4.39 (br d, J ) 8.0), and δC
71.4 (t), δH 3.75 (2H, s)] and to the double bond [δC 140.4 (s),
129.0 (s)]. The COSY data revealed the connectivity of H2-1/H-2,
H-9, H-8, H2-4/H2-5, and H-9/H2-10. HMBC correlations of H3-
12 (δ 1.13)/C-2, C-3, C-4, C-6, H3-13 (δ 1.98)/C-6, C-7, C-8 (δ
73.4), and H3-15 (δ 1.20)/C-1, C-10, C-11, C-14 (δ 71.4) revealed
two hydroxy groups at C-8 and C-14 and one double bond at C-6.
Thus, the planar structure of 3 was determined to be 6-(hydroxym-
ethyl)-3,6,7b-trimethyl-2,4,4a,5,6,7,7a,7b-octahydro-1H-cyclobu-
ta [e]inden-4-ol. The relative configuration at the stereocenters in
* Corresponding author. Tel: +81-88-622-9611. Fax: +81-88-655-3051.
E-mail: yosikawa@ph.bunri-u.ac.jp.
10.1021/np068006a CCC: $33.50
© 2006 American Chemical Society and American Society of Pharmacognosy
Published on Web 09/02/2006

1268 Journal of Natural Products, 2006, Vol. 69, No. 9
Yoshikawa et al.
Table 1. NMR Data for Russujaponols A-F (1-6) [600 MHz (1H) and 150 MHz (13C) in pyridine-d5]
1
2
3
position
1
δC
δH (mult, J in Hz)
δC
37.5
δH (mult, J in Hz)
δC
δH (mult, J in Hz)
1.79 (m)
1.48 (ddd, 12.6, 8.1, 1.9)
2.49 (dt, 11.5, 8.1)
47.3
2.81 (d, J )13.7)
2.01 (d, J )13.7)
1.88 (dd, 12.6, 12.6)
1.63 (dd, 12.6, 7.7, 2.2)
2.76 (dd, J )12.6, 7.7)
36.6
2
3
4
5
6
7
8
9
87.5
52.3
24.4
27.7
78.3
48.1
214.3
62.2
40.5
57.0
45.1
37.3
25.6
140.3
122.8
78.8
87.7
48.4
46.4
45.9
36.5
25.2
140.4
129.0
73.4
50.5
42.5
1.60 (m), 1.79 (m)
2.19 (2H, m)
1.82 (m), 1.93 (m)
2.53 (m), 2.71 (m)
1.80 (2H, m)
2.58 (m), 2.74 (m)
3.75 (q, J )6.3)
5.54 (br s)
4.39 (br d, J )8.0)
2.71 (m)
2.13 (ddd, 12.4, 7.7, 1.9)
1.82 (m)
3.53 (dd, J )10.9, 6.0)
2.41 (dd, J )13.7, 6.0)
2.33 (dd, J )13.7, 10.9)
10
2.15 (d, J )13.5)
2.00 (dd, J )13.5, 2.2)
11
12
13
14
46.6
18.0
8.1
44.8
20.2
13.0
71.3
45.7
20.6
12.2
71.4
1.80 (s)
1.14 (s)
1.70 (s)
3.70 (2H, s)
1.13 (s)
1.98 (s)
3.75 (2H, s)
1.42 (d, J )6.3)
3.62 (d, J )10.2)
3.59 (d, J )10.2)
1.54 (s)
70.1
15
Ac
26.8
24.0
20.7, 171.2
1.54 (s)
2.03 (s)
23.3
1.20 (s)
4
5
6
position
1
δC
δH (mult, J in Hz)
δC
δH (mult, J in Hz)
δC
δH (mult, J in Hz)
38.0
1.84 (dd, J )12.4, 12.4)
1.48 (dd, J )12.4, 6.9)
2.09 (m)
42.7
3.19 (d, J )15.8)
2.72 (d, J )15.8)
42.7
3.08 (d, J )15.9)
2.58 (d, J )15.9)
2
3
4
5
6
7
8
9
44.8
45.2
25.4
34.0
72.0
136.2
128.4
39.1
43.4
142.0
133.2
61.8
140.3
132.9
61.6
1.34 (m), 1.57 (m)
2.10 (m), 2.38 (m)
4.10 (2H, t, J )7.0)
3.30 (2H, t, J )7.0)
3.98 (2H, t, J )7.6)
3.15 (2H, t, J )7.6)
33.1
34.1
134.0
140.0
123.3
140.6
43.5
133.7
134.1
124.6
140.5
43.4
5.30 (br s)
2.72 (m)
1.88 (dd, J )13.3, 1.8)
1.72 (dd, J )13.3, 8.5)
7.37 (s)
6.89 (s)
10
3.09 (d, J )15.8)
2.60 (d, J )15.8)
3.17 (d, J )15.7)
2.70 (d, J )15.7)
11
12
13
14
44.3
22.2
18.1
72.2
45.0
15.9
63.8
69.9
45.0
16.1
20.5
69.9
1.45 (s)
1.94 (s)
3.53 (d, J )10.2)
3.59 (d, J )10.2)
1.24 (s)
2.20 (s)
5.07 (2H, s)
3.75 (2H, s)
2.23 (s)
2.36 (s)
3.75 (2H, s)
15
27.3
25.1
1.33 (s)
25.2
1.34 (s)
H-8/H-10R (δ 1.82) indicated a â-cis A/B ring junction and
R-orientations of H-8, H3-12, and CH2OH at C-14.
Russujaponol D (4) has the same molecular formula, C15H24O2,
and molecular ion at m/z 236.1780 [M]+ in the HREIMS as 3,
requiring four unsaturation equivalents. Indeed, the NMR spectra
of 4 were generally similar to those of 3. The COSY spectrum
indicated the connectivity of H2-1/H-2, H-9, H-8, H3-13, H2-4/H2-
5, and H-9/H2-10. HMBC correlations showed H3-12/C-2, C-3, C-4,
C-6 (δ 72.0), H3-13/C-6, C-7 (δ 136.2), C-8 (δ 128.4), and H3-
15/C-1, C-10, C-11, C-14 (δ 72.2). These observations confirmed
that compound 4 possesses the same skeleton as 1-3. Thus, the
planar structure of 4 was determined as 6-(hydroxymethyl)-3,6,-
7b-trimethyl-2,2a,4a,5,6,7,7a,7b-octahydro-1H-cyclobuta[e]inden-
2a-ol. The relative configuration of 4 was deduced from a NOESY
experiment, which indicated the R-orientation of H3-12, 6-OH, and
14-CH2OH and the â-orientation of H-2, H-9, and H3-15. The
structure of 4 is thus assigned as shown in Figure 1.
Russujaponol E (5) has the molecular formula C15H22O3 on the
basis of the 13C NMR data and HREIMS, thus requiring five
unsaturation equivalents. The HMQC data of 5 showed a penta-
substituted aromatic ring [δ 142.0 (s), 140.6 (s), 140.0 (s), 134.0
(s), 133.2 (s), and δC 123.3 (d), δH 7.37 (s)], two methyls [δ 1.33
(s), 2.20 (s)], and three primary hydroxy groups [δ 61.8 (t), 63.8
Figure 1. Structures of russujaponols A-F (1-6).
1
(t), 69.9 (t)]. A comparison of the H and 13C NMR data of 5 and
those of compound 4b4 suggested that compound 5 has the same
illudalane skeleton as compound 4b. The olefinic proton at δ 7.37
showed HMBC correlations to C-2 (δ 142.0), C-6 (δ134.0), C-10
3 was established by a ROESY experiment, which showed NOE
correlations between H-2 (δ 2.49)/H-9 (δ 2.71), H3-15 and between
H-9/H-10â (δ 2.13), H3-15, and further H3-12/H-8 (δ 4.39) and

Illudoid Sesquiterpenes from Russula japonica
Journal of Natural Products, 2006, Vol. 69, No. 9 1269
Figure 3. ORTEP drawing for 1a.
Fungus Material. The fruiting bodies of R. japonica were collected
at Tokushima, Japan, in autumn 1999. A voucher specimen (TB3066)
is deposited in the Herbarium of the Faculty of Pharmaceutical Sciences,
Tokushima Bunri University, Tokushima, Japan.
Extraction and Isolation. The fresh fruiting bodies (3.8 kg) of R.
japonica were extracted with 70% EtOH at room temperature for 4
weeks (×2). The EtOH extract was partitioned between EtOAc and
H2O. The EtOAc-soluble portion (36.0 g) was subjected to silica gel
column chromatography with diisopropyl ether-MeOH (50:1-25:8)
to afford fractions 1-6. Fraction 2 was purified by preparative HPLC
(ODS, 36% MeOH) to afford russujaponols D (4, 5 mg) and F (6, 63
mg). Fraction 3 was passed through silica gel with diisopropyl ether-
MeOH (30:1) to afford fractions 3-1 to 3-4. Fractions 3-2 and 3-3 were
successively purified by preparative HPLC (ODS, 30-32% MeOH)
to afford compound 4b (45 mg) and deliquinone (20 mg) from fraction
3-2 and russujaponols B (2, 5 mg) and C (3, 10.2 mg) from fraction
3-3, respectively. Fraction 5 was passed through silica gel with
diisopropyl ether-MeOH-H2O (25:2:0-25:6:0.1) to afford fractions
5-1 to 5-4. Similar purification by silica gel column chromatography
and preparative HPLC (ODS, 30-32% MeOH) afforded russujaponol
A (1, 226.5 mg) from fraction 5-2 and russujaponol E (5, 16.5 mg)
from fraction 5-3.
Figure 2. COSY (bold line), selected HMBC (arrow line), and
selected ROESY (dashed arrow line) correlations of 1-4.
(δ 43.5), and C-13 (δ 63.8). Combined analysis of COSY, HMQC,
and HMBC spectra enabled assignment of the hydroxyl groups at
C-4, C-13, and C-14. Hence, the structure of 5 was formulated as
(6-(2-hydroxyethyl)-2,7-dimethyl-2,3-dihydro-1H-indene-2,5-diyl)-
dimethanol. On the basis of the above findings and the fact that 5
coexisted with 1-4, the structure of 5 was formulated as shown in
Figure 1.
Russujaponol D (6) showed the molecular formula C15H22O2,
as determined by HREIMS. The 1H NMR data of 6 were compatible
with those of 5, implying that 6 could possess the same skeleton
as 5. The NMR spectra showed one methyl group [δH 2.36 (s), δC
20.5] instead of the hydroxymethyl group [δH 5.07 (2H, s), δC 63.8
(t)] in 5. The HMBC correlations from the methyl signal (δ 2.36)/
C-6 [δ 133.7 (s)], C-7 [δ 134.1(s)], and C-8 [δ 124.6 (d)]) confirmed
the additional methyl group at C-7. From analysis of all of this
data, the structure of 6 was formulated as 2-(2-hydroxymethyl-
2,4,6-trimethylindan-5-yl)ethanol. Compound 6 has previously been
obtained as the product of Clemmensen reduction of epipterosin
L.8
Russujaponol A (1): amorphous powder; [R]25 -110.1 (c 1.5,
D
MeOH); FT-IR (film) νmax 3370, 1710, 1080, 1070 cm-1; HRFABMS
m/z [M + Na]+ 291.1562 (calcd for C15H24O4 + Na, 291.1572).
Russujaponol B (2): amorphous powder; [R]25 -100.2 (c 0.4,
D
MeOH); FT-IR (film) νmax 3370, 1730, 1245, 1085, 1070 cm-1
;
HRFABMS m/z [M + Na]+ 317.1732 (calcd for C17H26O4 + Na,
317.1729).
Russujaponol C (3): amorphous powder; [R]25 -48.6 (c 0.4,
D
MeOH); FT-IR (film) νmax 3370, 1080, 1070 cm-1; HREIMS m/z [M]+
236.1791 (calcd for C15H24O2, 236.1776).
Russujaponol D (4): amorphous powder; [R]25 -26.2 (c 0.5,
D
MeOH); FT-IR (film) νmax 3370, 1080, 1070 cm-1; HREIMS m/z [M]+
Compounds 1, 2, and 4 were subjected to a cytotoxic activity
assay against cell lines, including 39 human cancer cell lines.9,10
No activity was observed in the assay. The main compound 1 was
investigated for the inhibitory activity on migration of the human
HT1080 fibrosarcoma cell line and inhibited invasion of 63% of
HT1080 to reconstituted basal membrane, at 3.73 M (positive
control, doxorubicin 52% at 0.17 µM).
236.1780 (calcd for C15H24O2, 236.1776).
Russujaponol E (5): amorphous powder; [R]25 -18.2 (c 0.2,
D
MeOH); UV (MeOH) λmax (log ꢀ) 230 (4.16), 280 (4.13); FT-IR (film)
νmax 3370, 1600, 1070 cm-1; HREIMS m/z [M]+ 250.1562 (calcd for
C15H22O3, 250.1569).
Russujaponol F (6): amorphous powder; [R]25D +1.3 (c 3.1, MeOH);
UV (MeOH) λmax (log ꢀ) 230 (4.16), 280 (4.13); FT-IR (film) νmax
3370, 1080, 1070 cm-1; HREIMS m/z [M]+ 234.1615 (calcd for
C15H22O2, 234.1620).
Experimental Section
p-Bromobenzoylation of 1. To a solution of 1 (15 mg) in pyridine
(2 mL) were added p-bromobenzoyl chloride (15 mg) and 4-(dimethy-
lamino)pyridine (2 mg). The reaction mixture was stirred at room
temperature for 24 h and then concentrated in vacuo to give a residue,
which was purified by HPLC (ODS, 40% MeOH) to afford 1a (5 mg)
as colorless plates from diethyl ether-EtOH, mp 180 °C. X-ray
crystallographic analysis confirmed the structure of 1a (absolute
configuration; ORTEP diagram, Figure 2).
General Experimental Procedures. Optical rotations were recorded
on a JASCO DIP-1000 polarimeter. IR spectra were recorded on a
JASCO FT/IR-410, UV spectra were recorded on a Shimadzu UV-
1650PC, and NMR spectra were recorded on a Varian UNITY 600
spectrometer in C5D5N and CDCl3 using TMS as internal standard.
Coupling constants (J values) are given in Hz. The MS spectra were
measured on a JEOL AX-500 mass spectrometer.

1270 Journal of Natural Products, 2006, Vol. 69, No. 9
Yoshikawa et al.
Crystal Data for 1a. Data collection: DIP image plate. Cell
refinement: Scalepack (HKL). Data reduction: maXus. Program used
to solve structure: maXus.8 Program used to refine structure: SHELXS-
97.9 Refinemen on F2: full matrix least-squares. Diffractometer: DIP
image plate. Colorless crystal of C22H27BrO5 having approximate
dimensions 0.5 × 0.2 × 0.05 mm, MW 451.3508, monoclinic, P21, a
) 6.5200(4) Å, b ) 12.0380(5) Å, c ) 13.6460(11) Å, â ) 91.679-
(2)°, V ) 1070.58(12) Å, Z ) 2, Mo Ka radiation, λ ) 0.71073 Å, µ
) 1.949 mm-1, 3758 reflections, 253 parameters; only coordinates of
H atom refined, R ) 0.0541, Rw ) 0.1442, S ) 1.028, Flack parameter
) -0.008.
References and Notes
(1) Yoshikawa, K.; Kouso, K.; Takahashi, J.; Matsuda, A.; Okazoe, M.;
Umeyama, A.; Arihara, S. J. Nat. Prod. 2005, 68, 911-914.
(2) Yoshikawa, K.; Inoue, M.; Matsumoto, Y.; Sakakibara, T.; Miyataka,
H.; Matsumoto, H.; Arihara, S. J. Nat. Prod. 2005, 68, 69-73.
(3) Imazeki, R.; Hongo, T. Colored Illustrations of Mushrooms of Japan;
Hoikusha Press: Osaka, Japan, 1998; Vol II, p 47.
(4) Clericuzio, M.; Fu, J.; Pan, F.; Pang, Z.; Sterner, O. Tetrahedron
1997, 53, 9725-9740.
(5) Clericuzio, M.; Han, F.; Pan, F.; Pang, Z.; Sterner, O. Acta. Chem.
Scand. 1998, 52, 1333-1337.
(6) Sheldrick, G. M. SHELXS-97, Programs for Crystal Structure Solution
and the Refinement of Crystal Structures; University of Gottingen:
Germany, 1997.
Acknowledgment. We are grateful to Mr. T. Ohashi, fungologist,
Tokushima Prefectural Tomioka Nishi High School, for confirming the
identification of the fungus and to Ms. Ohashi for gathering the fungus.
We are grateful to Dr. S. Takaoka for the X-ray spectral measurement.
We would like to thank the Screening Committee of Anticancer Drugs
supported by a Grant-in Aid for Scientific Research on Priority Area
“Cancer” from The Ministry of Education, Culture, Sports, Science
and Technology, Japan.
(7) Mackay, S.; Gilmore, C. J.; Edwards, C.; Stewart, N.; Shankland,
K. maXus, Computer Program for the Solution and Refinement of
Crystal Structures; Bruker Nonius: The Netherlands; MacScience:
Japan; The University of Glasgow, 1999.
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