(2S,2′R)-Analogue of LG190178 is a major active isomer

Article abstract of DOI:10.1016/j.bmcl.2007.11.007

Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of the skin, prostat

Full text of DOI:10.1016/j.bmcl.2007.11.007

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry Letters 18 (2008) 120–123
(2S,20R)-Analogue of LG190178 is a major active isomer
Wataru Hakamata,a Yukiko Sato,a Haruhiro Okuda,a Shinobu Honzawa,b
Nozomi Saito,b Seishi Kishimoto,b Atsushi Yamashita,b Takayuki Sugiura,b
Atsushi Kittakab and Masaaki Kuriharaa,*
aDivision of Organic Chemistry, National Institute of Health Sciences, Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
bFaculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 199-0195, Japan
Received 27 June 2007; revised 17 October 2007; accepted 1 November 2007
Available online 5 November 2007
Abstract—Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary
hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of
the skin, prostate, colon, and breast as well as leukemia. LG190178 is a novel non-secosteroidal ligand for VDR. We synthesized
and evaluated stereoisomers of LG190178 and found that only an (2S,20R)-analogue of LG190178 (YR301) had strong activity.
Ó 2007 Elsevier Ltd. All rights reserved.
The active form of vitamin D3, 1a,25-dihydroxyvitamin
D3 (1a,25-(OH)2D3), is not only a regulator of calcium
OH
H
homeostasis and bone development and remodeling
but also a potent differentiator of leukemic cells.
1a,25-(OH)2D3 and its synthetic analogues exert these
effects by binding to the vitamin D receptor (VDR)
which belongs to the steroid/thyroid hormone nuclear
receptor superfamily. The X-ray crystal structure of
the ligand binding domain (LBD) of VDR with 1a,25-
dihydroxyvitamin D3 was determined by Moras et al.
in 2000 and the binding mode between ligands and
LBD-VDR was revealed.1 This enables the design of
VDR ligands by structure-based drug design. We have
also designed secosteroidal analogues2 (Fig. 1).
H
HO
OH
1α,25-dihydroxyvitamin D3
*
2
*
HO
O
O
2'
Recently, non-secosteroidal ligands for VDR have been
an attractive target for the development of new thera-
peutics.3 LG190178 is the first novel non-secosteroidal
ligand, with potential as therapeutic for cancer, leuke-
mia, and psoriasis with less calcium mobilization side ef-
fects than are associated with secosteroidal 1a,25-
(OH)2D3 analogues,4 however, LG190178 includes four
stereoisomers.5 We calculated to make ducking model of
four isomers and VDR, respectively,6 and the results are
summarized in Figure 2 and Table 1. The (2S,20R)-iso-
mer model was the most stable. There were hydrogen
bonds between 2-OH and Arg-274, Ser-237 and between
OH
OH
LG190178
(R)
2'
OH
(S)
2
OH
HO
O
O
YR301
Figure 1. Structure of 1a,25-dihydroxyvitamin D3, LG190178, and
YR301.
20-OH and His-305, His-397. (2S)-Isomers ((2S,20S) and
(2S,20R)) are expected to be more important than (2R)-
isomers.
Keywords: Vitamin D receptor; Non-secosteroidal ligand; (2S,20R)-L-
G190178; YR301.
*
Corresponding author. E-mail: masaaki@nihs.go.jp
0960-894X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.11.007

W. Hakamata et al. / Bioorg. Med. Chem. Lett. 18 (2008) 120–123
121
Figure 2. Modeled structure of stereoisomers of LG190178 bound to VDR.
to be the (2S,20R)-isomer. Using the same procedures
YR302, 303, and 304 were determined to be (2S,20S)-iso-
mer, (2R,20R)-isomer, and (2R,20S)-isomer, respectively
(Scheme 2).
Table 1. Difference of potential energy of docking modeling of four
isomers and VDR
Model
AE (kcal/mol)
I (2S,20R)
II (2S,20S)
III (2R,2R)
IV (2R,20S)
0
+1.87
+3.56
+4.94
Isomers were examined for transcriptional assays and
VDR affinity. The results are summarized in Table 2.
(2S,20R)-Isomer (YR301) exhibited potent transcrip-
tional activity, comparable to natural ligand 1a,
25-(OH)2D3. Moreover, in the cases of human colon
carcinoma cell, YR301 exhibited stronger activities than
1a,25-(OH)2D3. (2S,20S)- and (2R,20R)-isomers, diaste-
reomers of (2S,20R), decreased the activity by two orders
of magnitude, compared with (2S,20R)-isomer (YR301).
(2R,20S)-Isomer, the enantiomer of (2S,20R) exhibited
the weakest activity. It is very interesting that only
YR301 showed strong activity. Figure 4 shows an over-
lay of the X-ray structure of 1a,25-(OH)2D3 and mod-
eled structure of (2S,20R)-isomer (YR301) in LBD of
VDR. YR301 is well overlapped with 1a,25-(OH)2D3,
especially with the hydrophobic region, but YR301 is
not expected to be H-bonded to Tyr-143 and Ser-278,
which are H-bonded to 1a,25-(OH)2D3. It is important
to remember that considering H-bonds to Tyr-143 and
Ser-278 is important in the design of new ligands.
We synthesized (2S)-LG190178 and (2R)-LG190178. The
synthetic routes of (2S)-isomers and (2R)-isomers are
shown in Scheme 1. The 2-position asymmetric center
was constructed using optically active glycidols. (2S)-
Analogues and (2R)-analogues were analyzed by HPLC
with a chiral column (CHIRALPAK IA, solvent: hex-
ane/EtOH 9:1). HPLC charts are shown in Figure 3.
The four isomers are YR301, YR302, YR303, and
YR304, respectively. To determine the stereochemistry
of the 20-position, we synthesized the (2S,20R)-isomer
from (R)-diol 6. (R)-1-(Benzyloxy)-3,3-dimethylbutan-2-
ol 5 was separated using HPLC with a chiral column
(CHIRALPAK IA, DAICEL; solvent: hexane/EtOH
9:1) and hydrogenated in the presence of Pd(OH)2/C to af-
25
D
ford compound 6 (½aꢀ ꢁ31.6 (c = 1.00, methanol)) in
70% yield. Absolute configuration of 6 was determined
by comparing the optical rotation of 6 with that of the lit-
erature.7 Scheme 3 shows the synthesis of the (2S,20R)-
isomers from (R)-diol 6. Then YR301 was determined
In summary, we revealed that YR301, an (2S,20R)-ana-
logue of LG190178, was a major active isomer. YR301

122
W. Hakamata et al. / Bioorg. Med. Chem. Lett. 18 (2008) 120–123
OBn
OH
OH
(a)
(b)
OTs
OTs
OH
(R)
(a)
(R)
(R)
8
6
HO
OH
HO
O
7
O
1
2
(c)
(R)
HO
O
(b)
OBn
9
HO
HO
O
O
O
OH
O
3a
(d)
(S)
(R)
OH
HO
O
O
OH
O
10
OH
O
3b
Scheme 3. Reagents and conditions: (a) TsCl, C5H5N, CH2C12, rt,
19 h, 52%; (b) benzy trichloroacetimidate, TMSOTf, DMF, rt, 5 h,
72%; (c) 1, NaH, DMF, rt, l h, 32%; (d) (S)-glycidol, NaH, DMF,
80 °C, 3 h, 43%; H2, Pd(OH)2/C, rt, 24 h, 93 h.
(c)
Table 2. Biological activities for transcriptional assays and VDR
affinity
HO
O
O
OH
OH
Compound
Transcription EC50 (nM)
VDR
affinity
(2S)-isomers
(2R)-isomers
HOS/SFa HOS/5% Caco-2/5%
FCSb
FCSc
1a,25(OH)2D3
YR301 (2S,20R) 0.0396
YR302 (2S,20S)
YR303 (2R,20R) 4.68
YR304 (2R,20S) 15.6
0.0106
0.555
0.79
9.9
3.52
1.80
21.1
22.1
131.4
100
28.3
HO
O
O
1.66
0.831
0.482
0.112
OH
OH
16.8
83.2
a Human osteosarcoma cell, serum free.
b Human osteosarcoma cell, 5% fetal calf serum.
c Human colon carcinoma cell, 5% fetal calf serum.
Scheme 1. Reagents and conditions: (a) ClCH2COtBu, NaH, DMF,
80 °C, 12 h, 40%; (b) (S)-glycidol (or (R)-glycidol), NaH, DMF, 80 °C,
3 h, 59%; (c) NaBH4, MeOH, rt, 2 h, 89%.
Ser-278
His-305
YR301
YR303
YR302
YR304
(2S)-isomers
Tyr-143
Ser-237
(2R)-isomers
His-397
Figure 3. HPLC chart.
Arg-274
Separation by HPLC
with chiral column
OH
OH
OBn
OBn
Figure 4. Overlay of the X-ray structure of 1a,25-(OH)2D3 and
modeled structure of YR301 in VDR. la,25-(OH)2D3 and YR301 are
shown in orange and green, respectively. Hydrogen bonds are drawn as
dotted lines.
(R)
CHIRALPAK IA
Hex / EtOH = 9 / 1
4
5
OH
H2, Pd(OH)2-C
OH
[α]D25= -31.6o
(R)
Acknowledgments
6
This work was supported in part by the Budget for Nu-
clear Research of the Ministry of Education, Culture,
Sports, Science, and Technology, based on the screening
and counseling by the Atomic Energy Commission and
by a Grant-in-Aid for Scientific Research (C) from the
Japan Society for the Promotion of Science.
Scheme 2. Separation and determination of chiral.
exhibited potent biological activity, comparable to natu-
ral ligand 1a,25-(OH)2D3. Non-secosteroidal ligands for
VDR are novel candidates for therapeutic agents.

W. Hakamata et al. / Bioorg. Med. Chem. Lett. 18 (2008) 120–123
123
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