Transcript 1,2-DIHYDROPYRAZOLO[1,2-A]

ISMNCNR
Palermo
aIstituto
per lo Studio dei Materiali Nanostrutturati, CNR, Via U. La Malfa 153, 90146 Palermo, Italy. [email protected]
bDipartimento di Scienze e Tecnologie Molecolari e Biomolecolari (STEMBIO), Sezione di Chimica Farmaceutica e Biologica, Università di Palermo,
via Archirafi 32. 90123, Palermo, Italy.
The pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-one derivatives 1 have
been previously designed by us as new alkylating agent because
of their peculiar chemical behavior related to azolo-fused tetrazines
such as Mitozolomde and Temozolomide, currently used in cancer
therapy. The NCI (USA) screening performed against more than 50
types of human tumor cell lines showed antiproliferative activity
reaching in some cases sub-micromolar values [1].
O
O
N
N
N
N
N
R1
N
R2
NH
R1
1
2
Like tetrazines, variously fused pyrazolo-triazines derivatives are
also of interest for their antiproliferative activity. In particular they
behave as novel potent inhibitors of CYP1A1, a cytochrome P450
family of enzymes involved in the metabolism of chemical
carcinogens [2] and inhibit CdK2 involved in the transition from G1
to S phase [3]. Drugs that inhibit Cdk2 and arrest the cell cycle
represent a strategy for prevention of chemotherapy induced
alopecia [4].
Recently, dihydro-1,3,5-triazino[1,2-a]benzimidazoles have also
been found to possess antifolate activity [5]. Antifolate drugs have
been developed as anticancer, antibacterial, antifungal, and
antiparasitic agents [6]. However, antifolate activity of the
compounds with benzo-pyralzol-3-one scaffold has not been yet
investigated.
Here, with the aim to modulate the biological profile, we planned to
switch our interest to the deaza tricycle 1,2-dihydropyrazolo[1,2a]benzo[1,2,4]triazine-3-one 2 exploiting the advantage of
introducing new moieties in R2 useful for carrying out SAR studies.
In the present work, we designed and synthesized a new series of
1,2-DIHYDROPYRAZOLO[1,2-A]BENZO[1,2,4]TRIAZINE-3-ONE
derivatives of type 2 containing selected functional groups in
order to evaluate their anticancer potential on human tumor cell
line.
Although in some cases derivatives 2 are metabolically unstable,
because of their nature of cyclic aminals, there are relatively
common structural elements with some commercial drugs,
including Aquamox and Thiabutazide, two members of the
benzo(thia)diazine class of cyclic aminals used for the treatment of
high blood pressure [10].
In our opinion, a good balance between the appropriate selection
of R1 and R2 moities could bring more stable derivatives.
Synthesis
O
N2+X-
NH2
NO2
R
4
N
R
N
(v)
N N
6
NO2
(iii)
O
O
NH
NH
NH2
R
2
O
5
R2
NH
H
(ii)
O
1
O
R1
3
N
O
NO2
(i)
1
R1
N
NO2
(iv)
R1
1
8
7
R1 = 4,5-di- Me; R'2 = Et, Ph, o-NO2Ph, o-BrPh, 2-Pyridil, (CH3O)3Ph, benzo[d][1,3]dioxole-5-yl;
There are some common
structural features, which are
unique to the triazine antifolates:
-(1) one of the carbon atoms of
triazine ring should be in sp3
hybridization (gem-dimethyl
substitution is usually preferred);
-(2) the other two carbon atoms
ought to be connected with
nitrogen atoms of amino group or
fused ring;
-(3) lypophilic aromatic moiety is
required at the distal part of
molecule [7].
Human DHFR with bound
dihydrofolate and NADPH
DHFR is responsible for the levels of tetrahydrofolate in a cell, and their
inhibition can limit the growth and proliferation of cells that are
characteristic of cancer.
Since folate is needed by rapidly dividing cells to make thymine, this
effect may be used to therapeutic advantage. Thus, human DHFR can
be targeted in the treatment of cancer.
A competitive inhibitor of human DHFR, is methotrexate, used as
anticancer drug [8]. Other drugs, acting only to bacterial DHFR and
used as antimicrobial agents include trimethoprim and pyrimethamine
[9].
(i) NaNO2/HCl, 0° C, (ii) HCl/ H2O r.t.; (iii) HCl conc, H2O; (iv) H2, 60 psi, EtOH, Pd/C o.n.;
(v) R2CHO EtOH reflux 4-6h.
The amino key intermediate 8 has been prepared by us
according to a previously optimized procedure [1]. The easy
condensation with selected commercial aldehydes afforded the
the di-hydro-1,2,4-triazine derivatives (40-80% yields).
The method, other than the high overall yields, allows the easy
introduction of selected moieties on crucial positions (R1 and R2),
simply choosing from the large amount of commercial availability
of orto-nitro amines and aldehydes.
Additionally, such a type of approach can be suitably exploited in
combinatorial chemistry for the synthesis of a small or virtual
library of compounds to be employed in computer aided drug
design for specific biological target. In this first step, we are
optimizing the yields, we are testing the compound stability, in a
second step we will be engaged to set up a stereoselective
approach.
Remarks
Antiproliferative screening of dervatives 2 are currently in
progress. Further target specifically testing will be made on human DHFR
References
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