Journal of Steroid Biochemistry & Molecular Biology 148 (2015) 27–30
Contents lists available at ScienceDirect
Journal of Steroid Biochemistry & Molecular Biology journal homepage: www.elsevier.com/locate/jsbmb
Review
Synthesis and biological activities of vitamin D3 derivatives with cyanoalkyl side chain at C-2 position Hiroshi Saitoh * , Hidekazu Watanabe, Shinji Kakuda, Midori Takimoto-Kamimura, Kenichiro Takagi, Akiko Takeuchi, Kazuya Takenouchi Teijin Institute for Bio-Medical Research, Teijin Pharma Ltd., 4-3-2 Asahigaoka, Hino, Tokyo 191-8512, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 July 2014 Received in revised form 2 December 2014 Accepted 7 December 2014 Available online 10 December 2014
We synthesized and evaluated novel vitamin D3 derivatives with cyanoalkyl side chain at C-2 position on the basis of our previous research for 2a side chain which bears nitrogen atom-containing functional group. Through a study of X-ray co-crystal structures of human VDR and compound 3, we demonstrated that the 2a alkyl side chain in compound 3 shows a novel interaction in the complex of hVDR-LBD and ligand. This article is part of a Special Issue entitled ‘17th Vitamin D Workshop’. ã 2014 Elsevier Ltd. All rights reserved.
Keywords: Vitamin D3 2a-Functionalized vitamin D Vitamin D receptor Binding affinity Transactivation X-ray co-crystallographic analysis
Contents 1. 2. 3. 4.
Introduction . . . . . . . . Results and discussion Discussion . . . . . . . . . . Conclusion . . . . . . . . . References . . . . . . . . .
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1. Introduction 1a,25-Dihydroxyvitamin D3 (1a) shows various biological activities through interaction with a vitamin D receptor (VDR). The most important physiological role of 1a is a regulation of calcium and phosphorus metabolism as well as bone remodeling via action in bones, intestines, and kidneys, so 1a is used as therapeutic drug for osteoporosis in Japan. Among numerous synthetic derivatives of 1a, 2-substituted vitamin D3 derivatives show strong affinities to vitamin D receptor (VDR). The series of 2-substituted vitamin D3 derivatives, the derivatives which have
* Corresponding author. Tel.: +81 42 586 8265; fax: +81 42 587 5513. E-mail address: [email protected] (H. Saitoh). http://dx.doi.org/10.1016/j.jsbmb.2014.12.004 0960-0760/ ã 2014 Elsevier Ltd. All rights reserved.
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27 27 30 30 30
2-hydroxyalkyl side chain such as 2a-(3-hydroxypropoxy)-1a,25dihydroxyvitamin D3 (1b), show more potent biological activities to vitamin D receptor (VDR) pathway than 1a, because terminal hydroxyl group of 2a side chain in the ligand forms a hydrogen bond to Arg274 [1]. On the other hand, we previously designed and synthesized 2a[2-(tetrazol-2-yl)ethyl]-1a,25-dihydroxyvitamin D3 (1c) because we thought a nitrogen atom in the heteroaryl group would act as a hydrogen acceptor and form a hydrogen bond with Arg274. This compound showed a therapeutic effect in ovariectomized (OVX) rats models on enhancing bone mineral density, also formed a hydrogen bond between a nitrogen atom in the tetrazole group and Arg274 [2]. We took an interest of this findings and thought that cyano group might also act as a hydrogen acceptor same as tetrazole. Therefore, we designed and synthesized novel vitamin D3 derivatives with cyanoalkyl side chain at C-2 position (Fig. 1).
28
[(Fig._1)TD$IG]
H. Saitoh et al. / Journal of Steroid Biochemistry & Molecular Biology 148 (2015) 27–30
Fig. 1. Structures of 1a,25-dihydroxyvitamin D3, its 2a-functionalized analogs (1b and 1c) and target compounds (2–7).
followed by oxime formation and dehydration. Trost’s Pdcatalyzed coupling between bromoolefin (10) and eneyne (17), followed by deprotection and purification by HPLC gave a target compound (7) (Scheme 2). The newly synthesized derivatives 2–7 were examined by affinity to human VDR (hVDR) and transactivation assay in Hos cells (osteocalcin promoter) (Table 1). Affinities to hVDR of the compounds except 6 decreased to 10–30% of those of 1a,25dihydroxyvitamin D3 (1a), but EC50 values of transactivation activities of 2,3, 4 and 7 show same as 1a. Affinity and
2. Results and discussion A-ring precursors eneynes (9) were synthesized from the known precursors (8) [1,3,4]. Then 9 were coupled with CD ring precursor bromoolefin (10) by Trost’s Pd-catalyzed coupling reaction, followed by deprotection and purification by HPLC to give compounds (2–6), respectively (Scheme 1). The synthesis of compound (7) was accomplished as follows. Aring precursor (14) was synthesized from D-glucose derivative (11) in a similar manner to reported A-ring precursor [1]. Target A-ring precursor (17) was obtained by oxidation of primary alcohol in 15,
[(Schem_1)TD$FIG] OP
TBSO
OTBS X
(1)
1) TsOH-H2O, THF-MeOH 2) TsCl, Pyr. 3) KCN, 18-crown-6, DMF TBSO
OTBS
OH
Pd(PPh3)4, toluene, Et3N 100 deg.
X n
n
OTBS
8
10 Br OP = O-Protective group (TES, TMS, THP)
(2) deprotection N
HO
(3) HPLC
9
OH X n N
2-6 Scheme 1. Synthesis of 2–6.
H. Saitoh et al. / Journal of Steroid Biochemistry & Molecular Biology 148 (2015) 27–30
[(Schem_2)TD$FIG]
Scheme 2. Synthesis of 7.
Table 1 Human VDR binding affinity and osteocalcin promoter transactivation activity in HOS cells. Compound
Affinity to hVDRa (%)
Transactivation assay in Hos cells (osteocalcin promoter) (EC50 pM)
1a 2 3 4 5 6 7
100 10 12 32 7
Contents lists available at ScienceDirect
Journal of Steroid Biochemistry & Molecular Biology journal homepage: www.elsevier.com/locate/jsbmb
Review
Synthesis and biological activities of vitamin D3 derivatives with cyanoalkyl side chain at C-2 position Hiroshi Saitoh * , Hidekazu Watanabe, Shinji Kakuda, Midori Takimoto-Kamimura, Kenichiro Takagi, Akiko Takeuchi, Kazuya Takenouchi Teijin Institute for Bio-Medical Research, Teijin Pharma Ltd., 4-3-2 Asahigaoka, Hino, Tokyo 191-8512, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 23 July 2014 Received in revised form 2 December 2014 Accepted 7 December 2014 Available online 10 December 2014
We synthesized and evaluated novel vitamin D3 derivatives with cyanoalkyl side chain at C-2 position on the basis of our previous research for 2a side chain which bears nitrogen atom-containing functional group. Through a study of X-ray co-crystal structures of human VDR and compound 3, we demonstrated that the 2a alkyl side chain in compound 3 shows a novel interaction in the complex of hVDR-LBD and ligand. This article is part of a Special Issue entitled ‘17th Vitamin D Workshop’. ã 2014 Elsevier Ltd. All rights reserved.
Keywords: Vitamin D3 2a-Functionalized vitamin D Vitamin D receptor Binding affinity Transactivation X-ray co-crystallographic analysis
Contents 1. 2. 3. 4.
Introduction . . . . . . . . Results and discussion Discussion . . . . . . . . . . Conclusion . . . . . . . . . References . . . . . . . . .
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1. Introduction 1a,25-Dihydroxyvitamin D3 (1a) shows various biological activities through interaction with a vitamin D receptor (VDR). The most important physiological role of 1a is a regulation of calcium and phosphorus metabolism as well as bone remodeling via action in bones, intestines, and kidneys, so 1a is used as therapeutic drug for osteoporosis in Japan. Among numerous synthetic derivatives of 1a, 2-substituted vitamin D3 derivatives show strong affinities to vitamin D receptor (VDR). The series of 2-substituted vitamin D3 derivatives, the derivatives which have
* Corresponding author. Tel.: +81 42 586 8265; fax: +81 42 587 5513. E-mail address: [email protected] (H. Saitoh). http://dx.doi.org/10.1016/j.jsbmb.2014.12.004 0960-0760/ ã 2014 Elsevier Ltd. All rights reserved.
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27 27 30 30 30
2-hydroxyalkyl side chain such as 2a-(3-hydroxypropoxy)-1a,25dihydroxyvitamin D3 (1b), show more potent biological activities to vitamin D receptor (VDR) pathway than 1a, because terminal hydroxyl group of 2a side chain in the ligand forms a hydrogen bond to Arg274 [1]. On the other hand, we previously designed and synthesized 2a[2-(tetrazol-2-yl)ethyl]-1a,25-dihydroxyvitamin D3 (1c) because we thought a nitrogen atom in the heteroaryl group would act as a hydrogen acceptor and form a hydrogen bond with Arg274. This compound showed a therapeutic effect in ovariectomized (OVX) rats models on enhancing bone mineral density, also formed a hydrogen bond between a nitrogen atom in the tetrazole group and Arg274 [2]. We took an interest of this findings and thought that cyano group might also act as a hydrogen acceptor same as tetrazole. Therefore, we designed and synthesized novel vitamin D3 derivatives with cyanoalkyl side chain at C-2 position (Fig. 1).
28
[(Fig._1)TD$IG]
H. Saitoh et al. / Journal of Steroid Biochemistry & Molecular Biology 148 (2015) 27–30
Fig. 1. Structures of 1a,25-dihydroxyvitamin D3, its 2a-functionalized analogs (1b and 1c) and target compounds (2–7).
followed by oxime formation and dehydration. Trost’s Pdcatalyzed coupling between bromoolefin (10) and eneyne (17), followed by deprotection and purification by HPLC gave a target compound (7) (Scheme 2). The newly synthesized derivatives 2–7 were examined by affinity to human VDR (hVDR) and transactivation assay in Hos cells (osteocalcin promoter) (Table 1). Affinities to hVDR of the compounds except 6 decreased to 10–30% of those of 1a,25dihydroxyvitamin D3 (1a), but EC50 values of transactivation activities of 2,3, 4 and 7 show same as 1a. Affinity and
2. Results and discussion A-ring precursors eneynes (9) were synthesized from the known precursors (8) [1,3,4]. Then 9 were coupled with CD ring precursor bromoolefin (10) by Trost’s Pd-catalyzed coupling reaction, followed by deprotection and purification by HPLC to give compounds (2–6), respectively (Scheme 1). The synthesis of compound (7) was accomplished as follows. Aring precursor (14) was synthesized from D-glucose derivative (11) in a similar manner to reported A-ring precursor [1]. Target A-ring precursor (17) was obtained by oxidation of primary alcohol in 15,
[(Schem_1)TD$FIG] OP
TBSO
OTBS X
(1)
1) TsOH-H2O, THF-MeOH 2) TsCl, Pyr. 3) KCN, 18-crown-6, DMF TBSO
OTBS
OH
Pd(PPh3)4, toluene, Et3N 100 deg.
X n
n
OTBS
8
10 Br OP = O-Protective group (TES, TMS, THP)
(2) deprotection N
HO
(3) HPLC
9
OH X n N
2-6 Scheme 1. Synthesis of 2–6.
H. Saitoh et al. / Journal of Steroid Biochemistry & Molecular Biology 148 (2015) 27–30
[(Schem_2)TD$FIG]
Scheme 2. Synthesis of 7.
Table 1 Human VDR binding affinity and osteocalcin promoter transactivation activity in HOS cells. Compound
Affinity to hVDRa (%)
Transactivation assay in Hos cells (osteocalcin promoter) (EC50 pM)
1a 2 3 4 5 6 7
100 10 12 32 7
