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R. Shimazawa et al. / Bioorg. Med. Chem. Lett. 14 (2004) 4339–4342
when the molecule is bound to Cdc25A (Fig. 1).1
Therefore, introduction of a hydrophilic phosphate
residue into carbon frameworks such as those found in
steroids or vitamin D3, might generate a new class of
potent inhibitors.7–9
The synthesis of b-methyl derivatives (6c,e) were started
from the b-methyl vinyl compound 108 as shown in
Scheme 3. Reductive removal of the carbonyl group by
means of Wolff–Kishner protocol provided the deoxy-
genated product 11, which was converted to the alcohol
5c by ozonolysis followed by NaBH4 reduction, and to
the alcohol 5e by hydroboration–oxidation transfor-
mation. Introduction of phosphate residue was per-
formed as described above to give 6c and 6e,
respectively.
Here, we report the design, synthesis and biological
activities of novel inhibitors of dual-specificity phos-
phatase Cdc25A. These inhibitors contain both a
phosphate group as a hydrophilic residue and a per-
hydroindan framework, derived from vitamin D3, as the
hydrophobic structure. In order to evaluate the effect of
the stereochemistry of the quaternary carbon centre and
the length of the spacer between the perhydroindan
framework and phosphate, five compounds (6a–e) were
designed and synthesized (Fig. 2).
Next, the synthesized compounds 6a–e10 were tested for
Cdc25A and Cdc25B-inhibitory activities in an assay
system utilizing dephosphorylation of O-methylfluores-
cein monophosphate (Table 1).11 As the phosphate
analogs might be substrates of Cdc25A and Cdc25B to
generate dephosphorylated carbinol products (5a–e), the
inhibitory activity of these compounds was also exam-
ined. The carboxylic acid derivative 3, a potent Cdc25A-
inhibitor, was employed as a positive reference com-
pound.6
The synthesis of 6a, having no spacer between the per-
hydroindan framework and phosphate, was performed
as shown in Scheme 1. The alcohol 5a was obtained by
complete ozonolysis of vitamin D3 followed by reductive
work-up with NaBH4. Phosphorylation of 5 by the
amidite method gave the dibenzyl phosphate 7a, which
was deprotected by hydrogenolysis using Pd-black to
give the phosphate 6a.
The phosphate analogs 6a–e displayed moderate to
strong inhibitory activity towards both Cdc25A and
Cdc25B. The strength of the Cdc25A/Cdc25B-inhibitory
activity depended on the length of the carbon chain
between the hydrophilic substructure and the hydro-
phobic substructure. Both of the derivatives 6b and 6c
having a one-methylene spacer showed higher Cdc25A/
Cdc25B-inhibitory activity than the other analogs.
However, the analogs 6d and 6e having a two-methylene
spacer showed contrasting results. The b-methyl deriv-
ative 6e showed higher inhibitory activity while the
a-methyl derivative 6d displayed only moderate activity.
Interestingly, 6b and 6c were Cdc25A-specific, while 6e
was Cdc25B-specific. Although the observed specificity
was moderate, these results demonstrated that the
phosphate analogs can differentiate the active site of
The a-methyl derivatives (6b,d) and b-methyl derivatives
(6c,e) were synthesized via the aldehyde 8 and the vinyl
derivative 10, both of which were the key intermediates
of dysidiolide analogs in previous report, respectively.8
The a-methyl alcohol 5b, having one-methylene as a
spacer, was obtained by reduction of the aldehyde 8.
The a-methyl alcohol 5d, having two-methylene as a
spacer, was synthesized from the aldehyde 9, which was
obtained by Magnus homologation of the aldehyde 8.
Finally, phosphorylation–deprotection of 5b and 5d, as
described for the synthesis of 6a, afforded 6b and 6d,
respectively (Scheme 2).
OR
RO
RO
RO
5d
6d R = PO3H2
RO
5e
5a
5b
5c
R = H
R = H
6b R = PO3H2
R = H
6c R = PO3H2
R = H
R = H
6e R = PO3H2
6a R = PO3H2
Figure 2.
C8H17
C8H17
C8H17
a
b
c
2
OH
5a
OPO(OBn)2
OPO3H2
6a
7a
Scheme 1. Reagents and conditions: (a) i. O3, MeOH, pyridine, )78 °C, ii. NaBH4, )78 °C to rt, 89%; (b) i. (BnO)2PNEt2, 1H-tetrazole, CH2Cl2, rt,
ii. mCPBA, H2O, )78 °C to rt, 8%; (c) Pd-black, EtOH, 87%.