Pyrrolotriazine-5-carboxylate ester inhibitors of EGFR and HER2 protein tyrosine kinases and a novel one-pot synthesis of C-4 subsitituted pyrrole-2,3-dicarboxylate diesters

Article abstract of DOI:10.1139/V06-037

Pyrrolotriazines with an ester group at C-5 were prepared and evaluated as inhibitors of the EGFR and HER2 receptor tyrosine kinases, validated targets for cancer therapy. The C-5 ester (15) was at least as potent as its C-6 ester analogue (17), an exampl

Full text of DOI:10.1139/V06-037

528
Pyrrolotriazine-5-carboxylate ester inhibitors of
EGFR and HER2 protein tyrosine kinases and a
novel one-pot synthesis of C-4 subsitituted
pyrrole-2,3-dicarboxylate diesters1
Harold Mastalerz, Ashvinikumar V. Gavai, Brian Fink, Charles Struzynski,
James Tarrant, Gregory D. Vite, Tai W. Wong, Guifen Zhang, and Dolatrai M. Vyas
Abstract: Pyrrolotriazines with an ester group at C-5 were prepared and evaluated as inhibitors of the EGFR and
HER2 receptor tyrosine kinases, validated targets for cancer therapy. The C-5 ester (15) was at least as potent as its C-
6 ester analogue (17), an example of a known series of pyrrolotriazine EGRF/HER2 kinase inhibitors that show good
biochemical and cellular activity. The C-5 esters were synthesized from pyrrole 2,3-diesters that were made by a new,
one-pot procedure. This involved reaction of readily available N-tosyl derivatives of α-amino acid esters or ketones
with triphenylphosphine and diethyl acetylenedicarboxylate to form 3-pyrrolines via an intramolecular Wittig
olefination. The 3-pyrroline intermediates were not isolated but treated directly with base to eliminate toluenesulfinic
acid and generate the pyrrole 2,3-diesters in good yield.
Key words: pyrrolotriazine, EGFR, HER2, pyrrole, intramolecular Wittig reaction.
Résumé : On a préparé des pyrrolotriazines portant un groupe ester en position C-5 et on les a évalués comme inhibi-
teurs des kinases EGFR et HER2 du récepteur de tyrosine qui sont des cibles validées pour la thérapie du cancer.
L’ester en C-5 (15) est au moins aussi puissant que son analogue 17, l’ester en C-6, comme exemple d’une série
connue de pyrrolotriazines qui peuvent agir comme inhibiteurs de la kinase EGRF/HER2 et qui présentent une bonne
activité biochimique et cellulaire. Les esters en C-5 ont été synthétisés à partir de 2,3-diesters du pyrrole qui avaient
été préparés par une nouvelle méthode monotope. Celle-ci implique la réaction des dérivés N-tosylés d’esters d’acides
α-aminés ou de cétones avec de la triphénylphosphine et de l’acétylènedicarboxylate de diéthyle qui conduit à la for-
mation de 3-pyrrolines par le biais d’une oléfination de Wittig intramoléculaire. Les intermédiaires 3-pyrrolines n’ont
pas été isolés, mais traités directement avec une base pour éliminer l’acide toluènesulfinique et générer les 2,3-diesters
du pyrrole avec de bons rendements.
Mots clés : pyrrolotriazine, EGFR, HER2, pyrrole, réaction de Wittig intramoléculaire.
[Traduit par la Rédaction] Mastalerz et al. 533
Introduction
cancer therapy (2). Their frequent coexpression in a variety
of tumor types and their capacity to form heterodimers with
other members of the ErbB family provides a strong ratio-
nale for simultaneous targeting of both receptors. The
pyrrolo[2,1-f ][1,2,4]triazine nucleus has been identified as a
novel scaffold for ATP-competitive kinase inhibitors (3).
BMS scientists have shown that pyrrolotriazine analogs (1)
that carry an ester group at C-6 and a relatively large
lipohilic amino group at C-4 can show potent inhibition of
both the EGFR and the HER2 kinases (4). The C-6 ester
group can be modified to further improve biochemical po-
Receptor tyrosine kinases catalyze the phosphorylation of
proteins that are involved in the signaling processes that con-
trol cell proliferation and differentiation. Since aberrant acti-
vation of this kinases results in uncontrolled cell growth,
extensive drug discovery efforts have been made to find se-
lective, small molecule inhibitors for the treatment of can-
cers (1). The epidermal growth factor receptor (EGFR) and
HER2 are members of the ErbB family of receptor tyrosine
kinases and they have been clinically validated as targets for
Received 25 August 2005. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 21 April 2006.
Dedicated to Professor Walter A. Szarek for his scientific contributions, and just as important, for his long-time friendship.
H. Mastalerz,2 C. Struzynski, J. Tarrant, G. Zhang, and D.M. Vyas. Discovery Chemistry, Bristol-Myers Squibb Pharmaceutical
Research Institute, 5 Research Parkway, Wallingford, CT 06492, USA.
A.V. Gavai, B. Fink, and G.D. Vite. Discovery Chemistry, Bristol-Myers Squibb PRI, P.O. Box 4000, Princeton, NJ 08543-4000,
USA.
T.W. Wong. Oncology Drug Discovery, Bristol-Myers Squibb PRI, P.O. Box 4000, Princeton, NJ 08543-4000 USA.
1This article is part of a Special Issue dedicated to Professor Walter A. Szarek.
Can. J. Chem. 84: 528–533 (2006)
doi:10.1139/V06-037
© 2006 NRC Canada

Mastalerz et al.
529
Scheme 1.
O
O
O
O
H
RO
O
N
NaH, DMF
then NH2Cl, Et2O
O
RO
R'
RO
R'
HCONH2
∆
OR
2
NH
OR
R
N
N
N
NH
1
2
R
R = Me, R1 = H, R2 = Me
R = Et, R1 = H, R2 = OMe
8 R = Me, R' = Me
9 R = Et, R' = OMe
6 R = Me, R' = Me
7 R = Et, R' = OMe
4
5
POCl3
EtN(i-Pr)2
toluene, ∆
N
N
F
N
N
F
HN
R'
Cl
N
H N
2
R'
N
13
R
N
N
R
N
N
NaHCO3, CH3CN
14 R = Me, R' = CO2Me
EtOH, K2CO3
10 R = Me, R' = CO2Me
11 R = OMe, R' = CO2Et
12 R = CO2Et, R' = Me
15 R = Me, R' = CO2Et
16 R = OMe, R' = CO2Et
17 R = CO2Et, R' = Me
tency and cellular activity. To explore the structure–activity
relationships of these dual EGFR/HER2 pyrrolotriazine
kinase inhibitors and expand the potential for further lead
optimization, we prepared analogues of 1 where the C-6 es-
ter function and the C-5 substitutent are transposed, e.g., 2
and 3. This report describes the synthesis and the
EGFR/HER2 kinase inhibition of some representative exam-
ples of these pyrrolotriazine 5-esters. It also details a conve-
nient, one-pot synthesis of the pyrrole 2,3-diesters that are
synthetic precursors of pyrrolotriazines 3.
Scheme 2.
CO Me
2
R'O
O
O
PPh
3
'
RO
CO Me
2
PPh3
R
NH
R
N
CO Me
2
CO Me
2
Boc
Boc
18
19
X
'
R O
CO Me
2
'
R O
CO Me
2
DDQ
Y
HN
R'
4
5
R
CO Me
2
N
N
R
CO Me
2
6
N
R
N
N
Boc
Boc
21
20
1 R = CO2R'', R' = alkyl
2 R = alkyl, R' = CO2R''
3 R = alkoxy, R = CO2R''
The preparation of 6-alkoxy pyrrolotriazine analogs 3 re-
quired access to pyrroles that have an alkoxy group at C-4,
e.g., 5. A novel synthesis of such pyrroles has been reported
(7) and is outlined in Scheme 2. The readily available N-Boc
derivatives of α-amino acid esters 18 were found to react
with dimethyl acetylenedicarboxylate and triphenylphos-
phine to give 3-pyrrolines 20 by way of the stabilized ylide
19. These pyrrolines were isolated and then could be oxi-
dized to pyrroles 21 by heating with DDQ. We explored the
potential one-pot version of this procedure that is outlined in
Scheme 3. It was thought that the N-tosyl derivative of α-
amino acid esters 22 would similarly react with triphenyl
phosphine and an acetylenedicarboxylate to form pyrrolines
23 that could be treated directly with base to eliminate
toluenesulfinic acid and give the desired pyrroles 24. A simi-
lar base-promoted elimination of toluenesulfinic acid from a
N-tosyl pyrroline intermediate has been reported (8) to gen-
erate the corresponding pyrrole.
Results and discussion
Preparation of the 6-methyl-5-ester 15 began with the
known pyrrole 4 (5) and is outlined in Scheme 1. The
pyrrole was converted to its N-amino derivative (6) by treat-
ment with sodium hydride and monochloramine (6).
Cyclization of 6 in hot formamide to the pyrrolotriazine-4-
one (8) was followed by treatment with POCl3 in refluxing
toluene to give the 4-chloropyrrolotriazine (10). The 1-(3-
fluorobenzyl)-1H-indazol-5-amino group was chosen as the
lipohilic C-4 substituent and was introduced by reaction of
10 with 13 in the presence of base. The resulting methyl es-
ter 14 was then converted to the ethyl ester 15 to enable a di-
rect comparison of its biological activity with that of the
transposed ethyl ester analogue (17).
© 2006 NRC Canada

530
Can. J. Chem. Vol. 84, 2006
Scheme 3.
CO2Et
CO2Et
R2
R1
CO2Et
R2
CO2Et
R2
R1
O
PPh3
base
R1
CO2Et
NH
Ts
N
H
CO2Et
N
Ts
22
23
24
Table 2. EGFR and HER2 kinase inhibition.
IC50 (µmol/L)a,b
Table 1. Conversion of sulfonamides 22 to pyrroles.
Entry
22
R1
R2
Pyrrole (yield, %)
Compound
EGFR
HER2
1
2
3
4
a
b
c
H
OCH3
5 (82)
H
OCH2CH2OCH3
OCH3
24a (76)
24b (54)
24c (68)
0.31
>1
0.47
0.20
>1
0.63
15
16
17
CH3
Ph
d
OCH3
aRecombinant HER2 cytoplasmic sequence is ex-
pressed in Sf9 insect cells as an untagged protein
and purified by ion-exchange chromatography.
HER2 kinase activity is measured under the same
conditions as for EGFR. See refs. 3 and 9 for assay
conditions.
5
6
e
f
CH2CH2O
24d (7)
24e (94)
H
H
H
4-CH3OC6H5
7
8
g
CH3
24f (80)
24g (71)
h
CH2CH2CO2CH3
bIC50 values are reported as the mean of at least
three determinations. Variability around the mean
value was <15%.
Note: Reaction conditions: 22 (1 equiv.), PPh3 (1.25 equiv.), diethyl
acetylenedicarboxylate (1.2 equiv.), dioxane, 10 °C to room temperature,
1 h; reflux 16 h; DBU (2.0 equiv.), 90 °C, 2 h.
The proposed reaction was examined with toluene-
sulfonamide derivatives of α-amino acid esters of glycine,
alanine, phenylglycine, and α-amino butyrolactone (22a–
22d, Table 1, entries 1–5) that were prepared from commer-
cially available material by the Fischer esterification of
N-tosyl amino acids or by treatment of the α-amino acid es-
ters or lactone with p-toluenesulfonyl chloride in the pres-
ence of base. The derivatives were indeed found to react
with diethyl acetylenedicarboxylate and triphenyl phosphine
in refluxing dioxane to give the N-tosyl pyrroline intermedi-
ates 23 (confirmed by LC–MS analysis of the reaction mix-
ture). DBU was then added and the reaction was heating at
90 °C to effect the elimination of toluenesulfinic acid. Good
yields (82% to 54%) of the pyrroles 5 and 24a to 24c were
obtained. A low yield (7%) of the fused furopyrrole 24d was
obtained. LC–MS analysis of the initial cyclization reaction
mixture indicated the presence of the desired furopyrroline
23e together with other products that were not isolated or
identified. In this case, competing side reactions are most
likely seen because of the additional strain that is encoun-
tered in the transition state that leads to 23e.
To further explore the scope of this reaction, the
sulfonamide derivatives of some alkyl and aryl α-
aminoketones (22f–22h) were prepared and examined as
substrates (Table 1, entries 6–8). Good yields (94% to 71%)
of the pyrroles 24e–24g were obtained in all cases.
With a convenient synthesis of 4-alkoxy pyrrole-2,3-
dicarboxylic acid diesters in hand, an example of a
pyrrolotriazine 5-ester with an alkoxy group at C-6 was
made. The 6-methoxy pyrrolotriazine (16) was prepared
from 5 using the same sequence of reactions that were used
to make 15 (Scheme 1): N-amination of pyrrole 5;
cyclization of 7 in formamide; formation of the chloro-
imidate 9; and final attachment of the 1-(3-fluorobenzyl)-
1H-indazol-5-amino side chain. The 6-ester analogue (17)
was made for comparison purposes from the known (4) 4-
chloropyrrolotriazine intermediate (12).
Data for the inhibition of the EGFR and HER2 kinases by
15–17 is show in Table 2. The directly transposed analogue
(15) was found to be at least as potent a dual kinase inhibitor
as 17, while the 6-ether analogue (16) was less potent. Since
the 5-ester group in 15 is well-suited for functional group
modifications that could improve biochemical potency and
cellular activity, 15 became the focus of further structure ac-
tivity and lead optimization studies. These results will be re-
ported in the future.
Experimental section
Methyl 6-methyl-4-oxo-3,4-dihydropyrrolo[1,2- f ][1,2,4]-
triazine-5-carboxylate (8)
A
mixture of dimethyl 4-methyl-1H-pyrrole-2,3-
dicarboxylate (5) (4, 1.0 g, 5.1 mmol) and NaH (236 mg,
60% dispersion in oil, 1.3 equiv.) in dry DMF (2 mL) was
stirred at room temperature for 30 min. A solution of
monochloramine (6) (66 mL, 0.1 mol/L in diethyl ether,
1.3 equiv.) was added with vigorous stirring. After 2 h, the
reaction was cooled in an ice-water bath and an aqueous so-
lution of Na2S2O3 (20 mL, 1.0 N) was added with stirring.
This was diluted with water (200 mL) and extracted with
EtOAc (3 × 200 mL). The combined organic extracts were
washed with brine and dried (Na2SO4). Removal of the sol-
vent followed by silica gel column chromatography (gradi-
ent elution with mixtures of hexane containing 0%– 50%
EtOAc) afforded dimethyl 1-amino-4-methyl-1H-pyrrole-
2,3-dicarboxylate (6, 845 mg, 79% yield) as an oil. 1H NMR
(MeOH-d4, 500 MHz, ppm) δ: 2.08 (s, 3H), 3.78 (s, 3H),
3.82 (s, 3H), 6.69 (s, 1H). A suspension of 6 (805 mg,
3.80 mmol) in formamide (8 mL) was heated at 170 °C for
2 h under a N2 atmosphere. After cooling to room tempera-
© 2006 NRC Canada

Mastalerz et al.
531
ture, this was poured into water (20 mL) and left stirring
overnight. The product was collect by filtration, washed
with water and Et2O, and then dried (590 mg, 75%). H
NMR (MeOH-d4, 300 MHz, ppm) δ: 2.30 (s, 3H), 3.87 (s,
3H), 7.32 (s, 1H), 7.72 (s, 1H). HPLC purity: 93%. MS
(ESI) m/z: 208 (M + H).
an ice-cooled mixture of DL-alanine methyl ester hydrochlo-
ride (768 mg, 5.5 mmol) and toluenesulfonyl chloride
(1.05 g, 1 equiv.) in dry dichloromethane (12 mL). After
1 h, the bath was removed and after a further 2 h, the reac-
tion was filtered. The filtrate was washed with water, dried
(Na2SO4), and the solvent removed. This left the crude prod-
1
1
uct as an oil (1.26 g). H NMR (CDCl3, 500 MHz, ppm) δ:
1.35 (d, 3H, J = 7 Hz), 2.39 (s, 3H), 3.51 (s, 3H), 3.96 (m,
1H), 5.33 (d, J = 8.5 Hz, 1H), 7.27 (d, J = 8.0 Hz, 2H), 7.70
(d, J = 8.0 Hz, 2H). HPLC purity: 93%. MS (ESI) m/z: 228
(M + H).
Methyl 4-(1-(3-fluorobenzyl)-1H-indazol-5-ylamino)-6-
methylpyrrolo[1,2- f ][1,2,4]triazine-5-carboxylate (14)
A mixture of methyl 6-methyl-4-oxo-3,4-dihydropyrrolo-
[1,2-f ][1,2,4]triazine-5-carboxylate (8, 1.00 g, 4.83 mmol),
POCl3 (0.54 mL, 1.2 equiv.) and diisopropylethylamine
(0.67 mL, 0.8 equiv.) in dry toluene (15 mL) was heated at
reflux for 5 h. After cooling to room temperature, the reac-
tion was poured into a saturated aqueous solution of
NaHCO3 with vigorous stirring. The organic phase was sep-
arated, washed with additional satd. aq. NaHCO3 solution
and dried (Na2SO4). Removal of the solvent followed by sil-
ica gel chromatography (elution with dichloromethane)
afforded methyl 4-chloro-6-methylpyrrolo[1,2-f][1,2,4]-
triazine-5-carboxylate (10, 777 mg, 72%) as a solid. 1H
NMR (CDCl3, 500 MHz, ppm) δ: 2.45 (s, 3H), 3.95 (s, 3H),
7.68 (s, 1H), 8.26 (s, 1H). MS (ESI) m/z 226 (M + H). A
mixture of 10 (1.29 g, 5.06 mmol), 1-(3-fluorobenzyl)-1H-
indazol-5-amine (13, 1.46 g, 1.2 equiv.) and NaHCO3
(2.13 g, 5 equiv.) in dry CH3CN (50 mL) was left stirring at
room temperature for 4 h. The product was collected by fil-
tration, washed with water, and dried (2.06 g, 95%). 1H
NMR (CDCl3, 300 MHz, ppm) δ: 2.43 (s, 3H), 3.97 (s, 3H),
5.59 (s, 2H), 6.95 (m, 3H), 7.34 (m, 3H) 7.65 (m, 1H), 8.06
(s, 2H), 8.40 (s, 1H). MS (ESI) m/z: 431 (M + H). HRMS
(ESI) calcd. for C23H20N6O2F: 431.1737; found: 461.1653.
(S)-Methyl 2-(4-methylphenylsulfonamido)-2-
phenylacetate (22d)
Similarly, (S)-(+)-phenylglycine methyl ester hydrochlo-
ride was converted to the product. 1H NMR (CDCl3,
500 MHz, ppm) δ: 2.38 (s, 3H), 3.56 (s, 3H), 5.05 (d, J =
8 Hz, 1H), 5.63 (d, J = 8 Hz, 1H), 7.24 (m, 7H), 7.62 (d, J =
8.0 Hz, 2H). HPLC purity: 92%. MS (ESI) m/z: 320 (M + H).
4-Methyl-N-(2-oxo-tetrahydrofuran-3-yl)benzene-
sulfonamide (22e)
Similarly, 3-amino-dihydrofuran-2(3H)-one hydrobromide
1
was converted to the product. H NMR (CDCl3, 500 MHz,
ppm) δ: 2.29 (m, 1H), 2.43 (s, 3H), 2.70 (m, 1H), 3.89 (m,
1H), 4.18 (m, 1H), 4.20 (t, J = 9.0 Hz, 1H), 5.15 (m, 1H),
7.32 (d, J = 8.5 Hz, 2H), 7.78 (d, J= 8.5 Hz, 2H). HPLC pu-
rity: 90%. MS (ESI) m/z: 256 (M + H).
1-(4-Methoxyphenyl)-2-(4-methylphenylsulfonamido)-
ethanone (22f)
Similarly, 2-amino-1-(4-methoxyphenyl)ethanone hydro-
chloride was converted to the product (solid). 1H NMR
(CDCl3, 300 MHz, ppm) δ: 2.38 (s, 3H), 3.85 (s, 3H), 4.38
(d, 2H, (d, 1H, J = 4.5 Hz), 5.66 (m, 1H), 6.91 (d, 2H), 7.26
(d, 2H), 7.79 (m, 4H). HPLC purity: 90%. MS (ESI) m/z:
320 (M + H).
Ethyl 4-(1-(3-fluorobenzyl)-1H-indazol-5-ylamino)-6-
methylpyrrolo[1,2- f][1,2,4]triazine-5-carboxylate (15)
Transesterification (EtOH, K2CO3) of 14 gave the prod-
1
uct: H NMR (CDCl3, 500 MHz) (ppm) δ: 1.44 (t, J = 7 Hz,
3H), 4.42 (q, J = 7 Hz, 2H), 5.58 (s, 2H), 6.85 (m, 1H), 6.94
(m, 2H), 7.27 (m, 3H), 7.63 (m, 1H), 8.05 (s, 2H), 8.39 (s,
1H). 7.65 (m, 1H), 8.06 (s, 2H), 8.40 (s, 1H). MS (ESI) m/z:
445 (M + H). HRMS (ESI) for C24H22N6O2F calcd.:
445.1788; found: 445.1778.
4-Methyl-N-(2-oxopropyl)benzenesulfonamide (22g)
Tetrapropylammonium perruthenate (70 mg, 0.1 equiv.)
was added to a stirred suspension of N-(2-hydroxypropyl)-4-
methylbenzenesulfonamide (458 mg, 2.0 mmol), N-
methylmorpholine N-oxide (35 mg, 1.5 equiv.), and pow-
dered, dry 4 Å molecular sieves (1.6 g) in dry CH3CN. After
20 min, the CH3CN was removed under vacuum and the res-
idue was dissolved in dichloromethane and filtered through a
short pad of silica gel. The solvent was removed from the
filtrate and the product was isolated by radial silica gel chro-
matography (step gradient elution with mixtures of hexane
containing 0%–30% ethyl acetate) as a solid (159 mg, 35%).
1H NMR (CDCl3, 500 MHz, ppm) δ: 2.09 (s, 3H), 2.39 (s,
3H), 3.83 (d, J = 5 Hz, 2H), 5.35 (m, 1H), 7.28 (d, J =
8.0 Hz, 2H), 7.71 (d, J = 8.0 Hz, 2H). HPLC purity: 84%.
MS (ESI) m/z: 228 (M + H).
2-Methoxyethyl 2-(4-methylphenylsulfonamido)acetate
(22b)
A mixture of 2-(4-methylphenylsulfonamido)acetic acid
(5.0 g, 21.8 mmol), 2-methoxyethanol (10.0 g, 6 equiv.), and
p-toluenesulfonic acid (0.2 g, 0.05 equiv.) in xylene (50 mL)
was heated at 150 °C for 10 h. After cooling to room tem-
perature, this was washed with satd. aq. NaHCO3 solution
and dried (Na2SO4). Removal of the solvent followed by sil-
ica gel chromatography (step gradient elution with mixtures
of hexane containing 5%–30% EtOAc) afforded the product
1
as an oil (5.3 g, 84%). H NMR (CDCl3, 300 MHz, ppm) δ:
2.37 (s, 3H), 3.28 (s, 3H), 3.47 (t, J = 4.5 Hz, 2H), 3.76 (d,
J = 5.4 Hz, 2H), 4.12 (t, J = 4.5 Hz, 2H), 5.38 (m, 1H), 7.26
(d, J = 8.1 Hz, 2H), 7.70 (d, J = 8.1 Hz, 2H). HPLC purity:
92%. MS (ESI) m/z: 320 (M + H).
Methyl 5-(4-methylphenylsulfonamido)-4-oxopentanoate
(22h)
Methyl 5-amino-4-oxopentanoate hydrochloride was con-
1
verted to the product as described for 22c. H NMR (CDCl3,
Methyl 2-(4-methylphenylsulfonamido)propanoate (22c)
Triethylamine (1.53 mL, 2 equiv.) was added dropwise to
500 MHz, ppm) : 2.41 (s, 3H), 2.60 (m, 4H), 3.62 (s, 3H),
δ
2.89 (d, J = 5 Hz, 2H), 5.30 (m, 1H), 7. 28 (d, J = 8.0 Hz,
© 2006 NRC Canada

532
Can. J. Chem. Vol. 84, 2006
2H), 7.71 (d, J = 8.0 Hz, 2H). HPLC purity: 93%. MS (ESI)
m/z: 300 (M + H).
Diethyl 4-(4-methoxyphenyl)-1H-pyrrole-2,3-dicarboxylate
(24e)
1H NMR (500 MHz, CDCl3, ppm) δ: 1.28 (t, J = 7.2 Hz,
3H), 1.34 (t, J = 7.2 Hz, 3H), 3.80 (s, 3H), 4.32 (m, 4H),
6.88 (m, 2H), 6.94 (d, J = 3.1 Hz, 1H), 7.32 (m, 2H), 9.33
(s, 1H). 13C NMR (125 MHz, CDCl3, ppm) δ: 166.8, 160.4,
158.8, 128.8, 126.3, 125.8, 121.3, 120.4, 120.0, 114.1, 61.4,
61.0, 55.3, 14.3, 14.2. HRMS (ESI) calcd. for C17H19NO5:
316.1185; found: 316.1178.
General procedure for the preparation of 5 and 24a–
24g
A mixture of the sulfonamide (22a–22h) (1.0 equiv.) and
triphenylphosphine (1.25 equiv.) in dry dioxane (0.5 mol/L)
under a N2 atmosphere was cooled in an ice-water bath. Di-
ethyl acetylenedicarboxylate (1.2 equiv.) was added
dropwise over 5 min and the bath was removed. After 1 h,
the reaction was brought to reflux and left heating overnight.
The temperature was reduced to 90 °C and DBU (2.0 equiv.)
was added. After 2 h, the solvent was removed and the prod-
uct was isolated by silica gel column chromatography
eluting with mixtures of hexane containing 0%–25% ethyl
acetate.
Diethyl 4-methyl-1H-pyrrole-2,3-dicarboxylate (24f)
1H NMR (500 MHz, CDCl3, ppm) δ: 1.29 (t, J = 7.2 Hz,
3H), 1.33 (t, J = 7.0 Hz, 3H), 2.12 (s, 3H), 4.27 (m, 2H),
4.31 (m, 2H), 6.63 (d, J = 2.8 Hz, 1H), 9.55 (s, 1H). 13C
NMR (125 MHz, CDCl3, ppm) δ: 165.8, 160.5, 122.1,
121.9, 120.7, 120.5, 60.9, 60.7, 14.3, 14.2, 10.9. HRMS
(ESI) calcd. for C11H15NO4: 224.0922; found: 224.0913.
Diethyl 4-methoxy-1H-pyrrole-2,3-dicarboxylate (5)
1H NMR (300 MHz, CDCl3, ppm) δ: 1.28 (m, 6H), 3.71
(m, 3H), 4.28 (m, 4H), 6.43 (d, J = 2.93 Hz, 1H), 9.58 (s,
1H). 13C NMR (125 MHz, CDCl3, ppm) δ: 164.2, 160.4,
148.5, 119.4, 109.9, 104.1, 61.1, 61.0, 58.7, 14.3. HRMS
(ESI) calcd. for C11H14NO5: 240.0872; found: 240.0875.
Diethyl 4-(3-methoxy-3-oxopropyl)-1H-pyrrole-2,3-
dicarboxylate (24g)
1H NMR (500 MHz, CDCl3, ppm) δ: 1.25 (t, J = 7.0 Hz,
3H), 1.30 (t, J = 7.0 Hz, 3H), 2.53 (t, J = 7.5 Hz, 3H), 2.83
(t, J = 7.63 Hz, 2H), 3.58 (s, 3H), 4.26 (m, 4H), 9.83 (s,
1H). 13C NMR (125 MHz, CDCl3, ppm) δ: 173.6, 165.5,
160.4, 125.1, 122.1, 120.4, 119.9, 60.9, 60.8, 51.6, 35.1,
21.2, 14.3, 14.2. HRMS (ESI) calcd. for C14H19NO6:
298.1291; found: 298.1277.
Diethyl 4-(2-methoxyethoxy)-1H-pyrrole-2,3-dicarboxylate
(24a)
1H NMR (500 MHz, CDCl3, ppm) δ: 1.24 (t, J = 7.2 Hz,
3H), 1.27 (t, J = 7.2 Hz, 3H), 3.34 (s, 3H), 3.61 (m, 2H),
3.95 (m, 2H), 4.24 (m, 4H), 6.45 (d, J = 3.1 Hz, 1H), 9.69
(s, 1 H). 13C NMR (125 MHz, CDCl3, ppm) δ: 164.3, 160.4,
146.9, 119.1, 110.9, 106.7, 71.7, 71.1, 60.9, 60.4, 59.5, 14.2,
14.0. HRMS (ESI) calcd. for C13H19NO6: 285.1134; found:
284.1131.
Ethyl 6-methoxy-4-oxo-3,4-dihydropyrrolo[1,2- f][1,2,4]-
triazine-5-carboxylate (9)
A
solution of diethyl 4-methoxy-1H-pyrrole-2,3-
dicarboxylate (5, 2.48 g, 10.3 mmol) in dry CH3CN (10 mL)
was added to an ice-cooled suspension of NaH (535 mg,
60% dispersion in oil, 1.3 equiv.) in dry dimethyl formamide
(20 mL) over 3 min. The bath was removed and the reaction
was left stirring for 1 h after which it was cooled in an ice
bath. A solution of monochloramine (135 mL, 0.1 mol/L in
diethyl ether, 1.3 equiv.) was added with vigorous stirring.
After 30 min, the bath was removed and the reaction was
left stirring for 1.5 h. It was then cooled in an ice-water bath
and worked up as described for 6. Silica gel column chroma-
tography (gradient elution with mixtures of hexane contain-
ing 0%–25% ethyl acetate) afforded diethyl 1-amino-4-
methoxy-1H-pyrrole-2,3-dicarboxylate (7) as an oil (1.53 g,
Diethyl 4-methoxy-5-methyl-1H-pyrrole-2,3-dicarboxylate
(24b)
1H NMR (500 MHz, CDCl3, ppm) δ: 1.31 (t, J = 7.2 Hz,
3H), 1.35 (t, J = 7.2 Hz, 3H), 2.20 (s, 3H), 3.77 (s, 3H), 4.28
(q, J = 7.1 Hz, 2H), 4.33 (q, J = 7.2 Hz, 2H), 9.42 (s, 1H).
13C NMR (125 MHz, CDCl3, ppm) δ: 164.9, 161.0, 143.5,
122.8, 115.4, 114.1, 62.7, 61.0, 60.8, 14.3, 14.2, 9.5. HRMS
(ESI) calcd. for C12H16NO5: 254.1028; found: 254.1021.
Diethyl 4-methoxy-5-phenyl-1H-pyrrole-2,3-dicarboxylate
(24c)
1
58% yield). H NMR (CDCl3, 300 MHz, ppm) δ: 1.30 (m,
1H NMR (500 MHz, CDCl3, ppm) δ: 1.33 (t, J = 7.2 Hz,
3H), 1.39 (t, J = 7.2 Hz, 3H), 3.79 (s, 3H), 4.32 (q, J =
7.1 Hz, 2H), 4.39 (q, J = 7.0 Hz, 2H), 7.31 (t, J = 7.3 Hz,
1H), 7.42 (t, J = 7.8 Hz, 2H), 7.69 (d, J = 7.7 Hz, 2H), 9.18
(s, 1 H). 13C NMR (125 MHz, CDCl3, ppm) δ: 164.7, 160.8,
143.8, 129.8, 128.9, 127.8, 125.9, 124.7, 117.4, 115.4, 62.2,
61.3, 61.2, 14.3, 14.2. HRMS (ESI) calcd. for C17H18NO5:
316.1185; found: 316.1179.
6H), 3.70 (s, 3H), 4.27 (m, 4H), 5.4 (br s, 2H), 6.47 (s, 1H).
MS (ESI) m/z: 257 (M + H). A suspension of 7 (880 mg,
3.44 mmol) in formamide (5 mL) was heated at 170 °C for
4 h under a N2 atmosphere. This was worked up as described
1
for 8 to give the product (514 mg, 63%) as a solid. H NMR
(300 MHz, DMSO-d6, ppm) δ: 1.25 (t, J = 7.2 Hz, 3H), 3.76
(s, 3H), 4.20 (q, J = 7.2 Hz, 2H), 7.44 (s, 1H), 7.91 (s, 1H).
MS (ESI) m/z: 238 (M + H). HRMS (ESI) calcd. for
C10H12N3O: 238.0828; found: 238.0824.
Diethyl 3,4-dihydro-2H- furo[3,2-b]pyrrole-5,6-
dicarboxylate (24d)
Ethyl 4-(1-(3-fluorobenzyl)-1H-indazol-5-ylamino)-6-
methoxypyrrolo[1,2- f][1,2,4]triazine-5-carboxylate (16)
A mixture of 9 (887 mg, 3.37 mmol), POCl3 (0.79 mL,
1.5 equiv.), and diisopropylethylamine (0.59 mL, 1.0 equiv.)
in dry toluene (12 mL) was heated at reflux for 5 h and then
worked up as described for 10. Silica gel radial chromatog-
raphy (elution with DCM) afforded ethyl 4-chloro-6-
1H NMR (500 MHz, CDCl3, ppm) δ: 1.35 (m, 6H), 3.12
(t, J = 8.4 Hz, 2H), 4.32 (m, 4H), 4.96 (t, J = 8.2 Hz, 2H),
9.20 (s, 1H). 13C NMR (125 MHz, CDCl3, ppm) δ: 162.7,
160.3, 153.3, 122.3, 121.6, 103.9, 78.4, 61.0, 60.7, 26.2,
14.4, 14.3. HRMS (ESI) calcd. for C12H16NO5: 254.1029;
found: 254.1038.
© 2006 NRC Canada

Mastalerz et al.
533
methoxypyrrolo[1,2-f][1,2,4]triazine-5-carboxylate (11,
458 mg, 53%) as a solid. MS (ESI) m/z: 256 (M + H).
HRMS (ESI) calcd. for C10H11N3O3Cl: 256.0489; found:
256.0496. A mixture of 11 (1.30 g, 5.10 mmol), 1-(3-
fluorobenzyl)-1H-indazol-5-amine (13, 1.25 g, 1.05 equiv.),
and diisopropylethylamine (1.07 mL, 1.2 equiv.) in dry
CH3CN (45 mL) was heated at 70 °C overnight. The product
was collected by filtration, washed with CH3CN, and dried
Conclusion
In summary, pyrrolotriazine analogs with an ester function
at C-5 were made and evaluated as dual inhibitors of EGFR
and HER2 kinases. The 5-ester 6-methyl analog (15) showed
kinase inhibition that was at least comparable to that seen
for the 6-ester 5-methyl analogue (17). It became the focus
of further structure activity and lead optimization studies
and these results will be reported in the future. In addition, a
general, one-pot procedure for the synthesis of C-4 substi-
tuted pyrrole-2,3-diesters from readily available N-tosyl de-
rivatives of α-amino acid esters and α-amino ketones was
developed.
1
(2.15 g, 92%). H NMR (300 MHz, CDCl3, ppm) δ: 1.43 (t,
J = 6.9 Hz, 3H), 3.89 (s, 3H), 4.42 (q, J = 6.9 Hz, 2H), 5.57
(s, 2H), 6.84 (m, 1H), 6.94 (m, 2H), 7.14 (s, 1H), 7.26 (m,
2H) 7.60 (m, 1H), 8.04 (s, 1H), 8.08 (s, 1H), 8.38 (m, 1H).
MS (ESI) m/z: 461 (M + H). HRMS (ESI) calcd. for
C24H22N6O3F: 461.1737; found: 461.1726.
References
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methyl-pyrrolo[2,1- f][1,2,4]triazine-6-carboxylate (17)
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1
the product as a white crystalline solid (76.3 g, 76%). H
NMR (500 MHz, CDCl3, ppm) δ: 1.39 (t, J = 7.2 Hz, 3H),
2.93 (s, 3H), 4.35 (q, J = 7.2 Hz, 2H), 5.59 (s, 2H), 6.86 (d,
J = 9.3 Hz, 1H), 6.97 (m, 2H), 7.26 (ddd, J = 6.04, 8.24,
14.29 Hz, 1H), 7.35 (d, 1H, J = 8.80 Hz), 7.42 (br s, 1H),
7.49 (dd, 1H, J = 1.65, 8.80 Hz), 7.91 (s, 1H), 8.00 (s, 1H),
8.07 (s, 1H), 8.09 (s, 1H). 13C NMR (125 MHz, CDCl3,
ppm) δ: 164.5, 163.0 (d, J = 246 Hz), 154.9, 148.5, 139.1 (d,
J = 5 Hz), 137.6, 133.8, 130.3, 131.2 (d, J = 7 Hz), 124.6,
123.5, 122.7, 121.9 (2C), 115.4, 115.3, 114.8 (d, J = 20 Hz),
114.1 (d, J = 22 Hz), 113.4, 109.7, 60.2, 52.6, 14.4, 11.9.
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C24H22FN6O2: 445.171; found: 445.1805. Anal calcd. for
C24H21FN6O2: C 64.85, H 4.76, N 18.90; found: C 64.62, H
4.73, N 18.85.
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© 2006 NRC Canada