Discovery of brivanib alaninate ((S)-((R)-1-(4-(4-fluoro-2-methyl-1H-indol- 5-yloxy)-5-methylpyrrolo[2,1-f][1,2,4]triazin-6-yloxy)propan-2-yl) 2-aminopropanoate), a novel prodrug of dual vascular endothelial growth factor receptor-2 and fibroblast growth

Article abstract of DOI:10.1021/jm7013309

A series of amino acid ester prodrugs of the dual VEGFR-2/FGFR-1 kinase inhibitor 1 (BMS-540215) was prepared in an effort to improve the aqueous solubility and oral bioavailability of the parent compound. These prodrugs were evaluated for their ability t

Full text of DOI:10.1021/jm7013309

1976
J. Med. Chem. 2008, 51, 1976–1980
Discovery of Brivanib Alaninate ((S)-((R)-1-(4-(4-Fluoro-2-methyl-1H-indol-5-yloxy)-5-
methylpyrrolo[2,1-f][1,2,4]triazin-6-yloxy)propan-2-yl)2-aminopropanoate), A Novel Prodrug of
Dual Vascular Endothelial Growth Factor Receptor-2 and Fibroblast Growth Factor Receptor-1
Kinase Inhibitor (BMS-540215)
Zhen-wei Cai,*,† Yongzheng Zhang,† Robert M. Borzilleri,† Ligang Qian,† Stephanie Barbosa,† Donna Wei,† Xiaoping Zheng,†
Lawrence Wu,† Junying Fan,# Zhongping Shi,# Barri S. Wautlet,‡ Steve Mortillo,‡ Robert Jeyaseelan, Sr.,‡ Daniel W. Kukral,‡
Amrita Kamath,§ Punit Marathe,§ Celia D’Arienzo,§ George Derbin, Joel C. Barrish,† Jeffrey A. Robl,† John T. Hunt,‡
Louis J. Lombardo,† Joseph Fargnoli,‡ and Rajeev S. Bhide†
Bristol-Myers Squibb Research and DeVelopment, Post Office Box 4000, Princeton, New Jersey 08543-4000
ReceiVed October 23, 2007
A series of amino acid ester prodrugs of the dual VEGFR-2/FGFR-1 kinase inhibitor 1 (BMS-540215) was
prepared in an effort to improve the aqueous solubility and oral bioavailability of the parent compound.
These prodrugs were evaluated for their ability to liberate parent drug 1 in in vitro and in vivo systems. The
L-alanine prodrug 8 (also known as brivanib alaninate/BMS-582664) was selected as a development candidate
and is presently in phase II clinical trials.
Chart 1. Examples of VEGFR-2 Inhibitors
Introduction
Vascular endothelial growth factor (VEGFa), fibroblast
growth factor (FGF), as well as their corresponding tyrosine
kinase receptors, VEGFR and FGFR, play a critical role in
physiological and pathological angiogenesis, a process of
forming new capillaries from existing blood vessels. Angio-
genesis is essential for solid tumor growth and metastasis.1,2
Tumor-induced angiogenesis is mediated by VEGF, FGF, and
other cytokines such as platelet-derived growth factor (PDGF).
Among them, VEGF is known to be one of the most important
angiogenic growth factor in the stimulation of tumor progres-
sion.1,3 Importantly, the specific binding of VEGF ligand to
vascular cell surface expressed protein kinase receptor VEGFR-2
triggers effective downstream cell proliferation signaling path-
ways and leads to tumor vascularization.4 The interruption of
VEGFR-2 signaling by binding of a small molecule inhibitor
to the VEGFR-2 kinase domain has been shown to inhibit
angiogenesis, tumor progression, and dissemination in a number
of preclinical and clinical studies.5 This approach has been
further validated by the recent FDA approval of the antiangio-
genic agents, such as bevacizumab (a monoclonal antibody
which targets to the VEGF-A ligand) and small molecule
inhibitors, sorafenib and sunitinib (Chart 1), for the treatment
of solid tumors.6 Similarly, FGFR-1 is also expressed on
endothelial cells and is important in cell survival and prolifera-
tion underlying blood vessel development and blood vessel
stabilization in tumor angiogenesis.7 Moreover, the FGFR family
of receptors has been associated with a variety of malignant
tumors including melanoma,8 glioma,9 pancreatic,10 as well as
bladder cancer.11
As part of our continuing effort to identify selective small-
molecule kinase inhibitors for antiangiogenic therapies underly-
ing cancer, we discovered a new class of pyrrolo[2,1-f]-
[1,2,4]triazine-based VEGFR-2 inhibitors. An optimized analog
1 (Chart 1) demonstrated potent inhibition against VEGFR-2
and FGFR-1, excellent kinase selectivity, and potent in vivo
efficacy versus H3396 and L2987 human lung carcinoma
xenografts implanted in athymic mice.12 However, oral admin-
istration of 1 in rat (at 25 mg/kg) as a micronized suspension
produced significantly lower systemic exposure levels of 1 than
those obtained from solution formulations. The low aqueous
solubility (<1 µg/mL at pH 6.5) of 1 presumably contributed
to dissolution rate-limited absorption of the compound, par-
ticularly at high doses. Efforts to improve the oral bioavailability
and increase drug plasma concentrations of 1 at high doses using
different formulation strategies were unsuccessful. To overcome
this potential development issue, we decided to investigate a
* To whom correspondence should be addressed. Phone: (609) 252-5627.
Fax: (609) 252-6601. E-mail: zhenwei.cai@bms.com.
†
Department of Chemistry.
Department of Process Discovery.
Department of Discovery Biology.
Department of Pharmaceutical Candidate Optimization.
#
‡
§
Department of Exploratory Biopharm. and Stability.
a Abbreviations: VEGFR-2, vascular endothelial growth factor receptor-
2; FGFR-1, fibroblast growth factor receptor-1; PDGF, platelet-derived
growth factor; Cbz, benzyloxycarbonyl; AUC, area under curve; DIPEA,
diisopropylethylamine; DMAP, 4-dimethylaminopyridine; HATU, 2-(3H-
[1,2,3]triazolo[4,5-b]pyridin-3-yl)-1,1,3,3-tetramethylisouronium hexafluoro-
phosphate; PEG, poly(ethylene glycol); TGI, tumor growth inhibition;
CYP450, cytochrome P450 enzyme.
10.1021/jm7013309 CCC: $40.75
2008 American Chemical Society
Published on Web 02/21/2008

Brief Articles
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1977
Scheme 1a
a Reagents and conditions: (a) K2CO3, DMF, 16 h; (b) MeMgBr, THF, 0 °C, 2–5 h, 75% yield over two steps; (c) H2O2, BF3/OEt2, CH2Cl2, -15 °C to
-25 °C, 1 h, 66%; (d) R-(+)- propylene oxide, LiCl, NEt3 (cat.), EtOH, 3 h, 81%; (e) CbzNHCR1R2COOH (7–15) or R3CO2H (16–20), HATU, DIPEA,
DMAP (cat.), THF, 5 h, 51–94%; (f) HCOO-NH4+, Pd/C, DMF, 69–99%.
prodrug approach. Amino acid ester prodrugs of alcohols have
been used successfully in marketed drugs to improve aqueous
solubility.13 Herein, we report our prodrug strategy of incor-
porating a variety of amino acids onto the secondary alcohol
group of 1 through a metabolically labile ester linkage to
improve its physicochemical and pharmacokinetic properties.
plasma are capable of hydrolyzing amino ester linkages. Our
desire was to identify prodrugs of high chemical stability that
displayed rapid and quantitative conversion to parent to
maximize drug exposure and minimize unproductive metabo-
lism. The prodrugs were initially evaluated to determine their
stability in human and mouse liver S9 fractions and in plasma.
Generally, the ester prodrugs tested were moderately stable to
ester cleavage in mouse plasma, and very stable to ester cleavage
in human plasma (data not shown), suggesting metabolic
conversion to 1 in the liver would be necessary. No attempts
were made to fully evaluate and rank the conversion of prodrugs
to 1 in human plasma since all prodrugs appeared to show the
remarkably low conversion. Thus, the assay for determining the
rate of conversion of prodrugs to parent 1 in liver S9 fraction
was considered to be the primary screening method. Table 1
illustrates the influence of the structure of the pro-moiety on
the hydrolytic rate. Prodrugs with R-substitution of less hindered
groups on amino acids such as 7 (glycinate), 8 (L-alaninate), 9
(D-alaninate), and 13 (L-leucinate) exhibited complete conversion
to parent 1 in both human and mouse liver S9 fractions within
the 5 min incubation time, with no additional major metabolites
detected. Compound 10 (R,R-dimethylglycinate) bearing chemi-
cal disubstitution on the R-carbon, also served as an excellent
substrate for esterase and was readily hydrolyzed under the assay
conditions. The use of more hindered amino acids, such as
compounds, 11 (L-valinate), 12 (D-valinate), 14 (L-isoleucinate),
and 15 (L-phenylalanine), provided lower rates of conversion
to parent drug 1. N,N-Dimethylglycinate 16 displayed a low
rate of conversion in mouse and moderate rate of conversion
in human liver S9 fractions. The 2-morpholinoacetate 17 gave
a moderate rate of conversion both in mouse and human liver
S9 fraction. Substituted benzoic acid prodrugs 18–20, in general,
demonstrated lower hydrolytic conversion rates.
Chemistry
The fluoroindole-substituted pyrrolotriazine ester 4 (Scheme
1) was synthesized in excellent yield by reacting chloroimidate
2
14 with 4-fluoro-2-methyl-1H-indol-5-ol (3)12 in the presence
of potassium carbonate in DMF. Treatment of ester 4 with
methyl magnesium bromide gave rise to the tertiary alcohol 5,
which underwent BF3/OEt2/50% H2O2 promoted oxidative
rearrangement15 to afford phenol 6 in good yield. This approach
was used as an effective alternative to the Baeyer–Villiger
reaction to prepare the key intermediate 6 from the correspond-
ing aldehyde.12 Base-catalyzed epoxide opening of R-(+)-
propylene oxide with 6 in ethanol at elevated temperature
afforded compound 1 in an enantiomeric excess of >99% ee.
The addition of lithium chloride to the reaction mixture enhanced
the rate of epoxide ring opening presumably due to chelation
of the lithium ion with the epoxide oxygen. The ester prodrugs
were generally prepared in excellent yield by coupling alcohol
1 with commercially available Cbz-protected amino acids or
the carboxylic acids bearing a tertiary amine in the presence of
HATU (2-(3H-[1,2,3]triazolo[4,5-b]pyridin-3-yl)-1,1,3,3-tetra-
methylisouronium hexafluorophosphate), DIPEA, and DMAP
in DMF to give esters 7–15 and 16–20, respectively. In the case
of 7–15, the final products were obtained after deprotection of
the Cbz group via a palladium-catalyzed hydrogen transfer
reaction with ammonium formate. No racemization of the chiral
amino esters occurred during the chemical transformations based
on an assessment of their enantiomeric purities in the synthesis of
L-alanine ester 8 and its enantiomeric isomer D-alanine ester 9.
Pharmacokinetics and Pharmaceutical Properties. Four
prodrugs (7, 8, 10, and 13) that demonstrated rapid conversion
to parent 1 in human and mouse liver S9 fraction were assessed
in oral exposure studies in mice (Table 2). All compounds were
administered as a 70:30 PEG70/water solution at 50 and 200
Results and Discussion
In Vitro Assessment of Prodrugs. A number of specific and
nonspecific esterases found in the stomach, intestines, liver, and

1978 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Table 1. Prodrug Stability in Liver S9 Fraction (5 Min Incubation)a,b
Brief Articles
Table 3. Inhibition of Human CYP Isozymes by Various Prodrugsa,b,c
IC50 for CYP inhibition (µM)
3A4
3A4
cmpd
1A2
2C9
>40
2C19
2D6
(BFC)
(BzRes)
1
7
8
13
>40
>40
0.16
2.1
>40
12
24
18
>40
0.31
1.6
3.7
0.063
9.7
2.7
0.16
0.51
0.095
>40
34
1.8
24
0.37
a Data are expressed as a mean of at least two measurements. b Highest
test concentration: 40 µM. c For assay condition, see ref 16.
Figure 1. In vivo antitumor activity of 8 vs L2987 xenografts in
athymic mice.
exposure of 1 relative to the other three natural amino acid
prodrugs (7, 8, and 13) and was not further pursued.
When evaluated in a cytochrome P450 panel to assess the
potential for drug-drug interactions, compounds 7, 8, and 13
were found to be more potent inhibitors of these metabolizing
enzymes than parent 1 (Table 3). Although no circulating
prodrug was observed for any of these compounds in the mouse
oral exposure assay, analogues with modest activity were
desirable since it was difficult to rule out the possibility of
incomplete conversion of prodrug to parent drug in the clinical
setting. Compound 7 was a highly potent inhibitor of the
CYP2C9 isoform (IC50 ) 63 nM), and demonstrated submi-
cromolar potency versus CYP3A4 and CYP2C19. Compound
13 also demonstrated submicromolar activity versus the CYP3A4
isoform. Overall, compound 8 showed the most favorable CYP
inhibition profile. The risk of drug-drug interactions was further
mitigated by the demonstration that compound 8 was rapidly
converted to parent 1 in human intestinal microsomes (18%
remaining of 8 after 10 min of incubation).
Prodrug 8 also exhibited high solid state stability (only 0.3%
degradation at 50 °C with desiccant over a period of 12 weeks)
and acceptable solution state stability up to pH 6.5. The
compound was extremely stable at pH 4.2 in buffer solution at
37 °C, with less than 1% of prodrug degrading to parent 1 over
a 24 h period. Furthermore, 8 possessed high aqueous solubility
(73 mg/mL at pH 5.8). Based on its promising results in the
above studies, 8 was selected for in vivo evaluation in tumor
xenograft studies.
a See Experimental Section for a description of assay conditions. b Data
are expressed as a mean of at least of two determinations (variation < 20%).
Table 2. Oral Exposure of Various Compounds in Micea,b,c
plasma concentration of 1
dose
(mg/kg)
AUC
(0–4 h; µM·hr)
AUC fold
increased
cmpd
Cmax (µM)
1
50
200
50
200
50
200
50
200
50
12 ( 6
14 ( 10
21 ( 3
126 ( 15
21 ( 5
78 ( 20
15 ( 6
66 ( 29
31 ( 4
152 ( 17
45 ( 16
52 ( 14
1.2
4.4
4.0
4.6
4.0
7
69 ( 26
303 ( 63
69 ( 16
276 ( 74
46 ( 16
213 ( 107
113 ( 26
451 ( 37
8
10
13
200
a Average of three female mice for each dose group. b Vehicle: PEG400/
water (70:30). c For assay condition, see ref 16. d AUC (200 mpk)/AUC
(50 mpk).
mg/kg doses, and the plasma concentrations of 1 were deter-
mined at 0.5, 1, and 4 h time points. Parent drug 1 demonstrated
the lowest systemic exposure at 50 mg/kg and no further
increase in circulating plasma levels at the high dose of 200
mg/kg. In contrast, prodrugs 7, 8, 10, and 13 produced higher
exposure levels of 1, where the AUC increased proportionally
with dose at levels of 50 and 200 mg/kg. These data demon-
strated efficient in vivo conversion of these four prodrugs to 1
in mice and suggested our prodrug strategy could serve to
overcome the pharmaceutics issues associated with 1. Among
the four prodrugs tested, 10 gave slightly lower levels of
In Vivo Antitumor Activity of 8. The in vivo antitumor
activity of 8 was evaluated in a L2987 nonsmall cell lung tumor
xenografts assay in athymic mice (Figure 1).17 Once daily oral
administration of 8 for 14 consecutive days inhibited the growth
of the established tumor (80–100 mm3 size) in a dose-dependent
manner. At 80 and 107 mg/kg doses, essentially complete tumor
stasis was observed throughout the dosing period, with a percent
tumor growth inhibition (%TGI) of 85 and 97%, respectively.
No overt toxicity was observed in either cohort of animals,

Brief Articles
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1979
white solid. The filtrate was further purified on silica gel using 40%
EtOAc/heptane to give additional product 6 (2.5 g, 14% yield).
MS (ESI+) m/z 313.2 (M + H)+. 1H NMR (400 MHz, DMSO-d6)
δ 11.34 (s, 1H), 9.60 (br s, 1H), 7.85 (s, 1H), 7.51 (s, 1H), 7.13 (d,
1H, J ) 8.7 Hz), 6.98 (t, 1H, J ) 8.7 Hz), 6.24 (s, 1H), 2.41 (s,
3H), 2.39 (s, 3H).
suggesting good safety margins in mice for this compound. This
result supported the concept that prodrug 8 could provide an
effective means to improve the pharmaceutical and pharmaco-
kinetic properties of 1 for clinical development.
Conclusions
(R)-1-(4-(4-Fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyr-
rolo[2,1-f][1,2,4]triazin-6-yloxy)propan-2-ol (1). A mixture of 6
(7.5 g, 24 mmol), R-(+)-propylene oxide (120 mmol), LiCl (3.02
g, 72 mmol), and NEt3 (300 µL) in EtOH (50 mL) was heated in
a sealed tube at 70 °C for 3 h. The solvent was reduced to about
10 mL and the residue was poured into water. The precipitate was
collected by filtration and washed with water. The crude solid was
dissolved in 5% EtOH/DCM and passed through a short pad of
silica gel, eluting with 20% EtOAc/DCM. The filtrate was
concentrated, and the solid residue was triturated with 30% EtOH/
heptane to afford 1 (7.2 g, 81% yield) as an off-white solid. MS
(ESI+) m/z 371.2 (M + H)+. 1H NMR (500 MHz, CD3OD) δ 7.72
(s, 1H), 7.61 (s, 1H), 7.10 (d, 1H, J ) 8.80 Hz), 6.90 (t, 1H, J )
7.15 Hz), 6.23 (s, 1H), 4.12–4.20 (m, 1H), 3.92 (d, 2H, J ) 6.55
Hz), 2.48 (s, 3H), 2.43 (s, 3H), 1.29 (d, 3H, J ) 6.6 Hz). Mp
208–210 °C. Anal. (C19H19FN4O3): C, H, N, F.
The synthesis and biological evaluation of a series of amino
ester prodrugs of 1 are reported. In vitro assessment of the
conversion of various prodrugs to 1 in liver S9 fraction and
serum and in vivo evaluation of their oral exposure in mice led
to the identification of compounds 7, 8, and 13 as potential lead
prodrugs. Evaluation of inhibition of human CYP enzymes by
these compounds revealed that prodrug 8 possessed favorable
CYP profile and least likelihood for drug-drug interactions.
Further studies showed that 8 demonstrated excellent pharma-
ceutical properties and significant antitumor activity against
L2987 human lung carcinoma xenografts. Based on these results,
8 was selected for advancement into preclinical toxicity studies
to support clinical development of this interesting drug candidate.
General Procedure for the synthesis of N-Cbz-Protected
Compounds 7–15 and 16–20. A mixture of 1 (1 equiv, 0.16 mmol),
the appropriate N-CbzNHCR1R2COOH or R3COOH (2.5 equiv,
0.4 mmol), HATU (253 mg, 0.4 mmol), DIPEA (103 mg, 0.8
mmol), and DMAP (5 mg) in DMF (1 mL) was stirred overnight.
The volatiles were removed in vacuo, and the residue was purified
by flash column chromatography or preparative HPLC conditions
to afford N-Cbz-protected compounds 7–15 and 16–20.
General Procedure for the Synthesis of Compounds 7–15. A
mixture of the appropriate N-Cbz-protected derivatives 7–15 (1
equiv, 0.11 mmol), Pd/C (10%, 6 mg), and ammonium formate
(200 mg) in DMF (1.5 mL) was stirred at RT for 0.5 to 2 h (the
reaction was monitored by HPLC for completion). The mixture
was diluted with ethyl acetate and filtered through a pad of celite.
The filtrate was washed with water, dried over Na2SO4, and passed
through a pad of silica gel, eluting with EtOAc. The filtrate was
concentrated and if necessary further purified by prep-HPLC
conditions. The desired fraction was lyophilized with HCl (1 N in
water) to afford the title compounds 7–15 as HCl salts.
Pharmacology. Incubation with Liver S9 Fractions. The in
vitro metabolism of prodrugs was investigated in incubations with
S9 subcellular fractions from mouse (CD-1) and human liver
homogenates. Incubation of prodrugs was done in duplicate with
S9 fractions from each species. The rate of metabolism was
measured under the following conditions: prodrug, 20 µM final
concentration (400 µM stock solutions in 4% DMSO/96% water;
final incubation solutions contained 0.2% DMSO); 20 µL of S9
per 200 µL incubation, final protein concentration 2 mg/mL; MgCl2,
10 mM; pH 7.4 sodium phosphate buffer, 60 mM. Incubations were
performed in 96-well plates at 37 °C under an atmosphere of 5%
CO2. Incubations were initiated by the addition of S9 and were
quenched at various times (0, 10, or 30 min) by the addition of an
equal volume (0.2 mL) of acetonitrile to each well. Plates were
sealed, vortexed, and centrifuged to pellet-precipitated proteins, and
the supernatants were transferred to clean plates or HPLC vials.
Samples were analyzed using a LC/MS/MS assay.
Stability of Prodrug 8 in Human Intestinal Microsomes. The
in vitro metabolism of 8 was investigated in incubations (in
duplicate) with human intestinal microsomes. The rate of oxidative
metabolism was measured under the following conditions: 8, 10
µM final concentration for intestinal microsomes (100 µM stock
solutions in 2% DMSO/19.5% acetonitrile/80% water; final incuba-
tion solutions contained 0.05% DMSO, 1.95% acetonitrile); final
protein concentration, 1 mg/mL; NADPH, 0.9 mg/mL; pH 7.4
sodium phosphate buffer, 56 mM. Incubations were performed in
96-well plates at 37 °C under an atmosphere of 5% CO2. Incubations
were initiated by the addition of NADPH and were quenched at
various times (0, 10, or 30 min) by the addition of an equal volume
(0.2 mL) of acetonitrile to each well. Plates were sealed, vortexed,
Experimental Section
Chemistry. Preparation of 2-(4-(4-Fluoro-2-methyl-1H-indol-
5-yloxy)-5-methylpyrrolo[2,1-f][1,2,4]triazin-6-yl)propan-2-ol
(5). To a solution of freshly prepared chloroimidate 214,18 (167.8
g, 0.7 mol) in DMF (1.1 L) was added K2CO3 (267 g, 2.1 mol)
and 4-fluoro-2-methyl-1H-indol-5-ol 312 (109.5 g, 0.7 mol). The
reaction mixture was stirred at rt for 16 h and then cooled to 0 °C.
The mixture was diluted with water and extracted with EtOAc. The
organic layer was washed with water, 10% aqueous LiCl, and water.
The organic extract was concentrated in vacuo, and the residue was
coevaporated with toluene to give crude 4. MS (ESI+) m/z 369.4
1
(M + H)+. H NMR (400 MHz, CDCl3) δ 8.15 (s, 1H), 7.90 (s,
1H), 7.08 (d, 1H, J ) 8.25 Hz), 6.98 (dd, 1H), 6.34 (s, 1H), 4.39
(q, 2H, J ) 7.15 Hz), 2.87 (s, 3H), 2.45 (s, 3H), 1.41 (t, 3H, J )
7.15 Hz).
To a mixture of compound 4 and LiCl (140 g) in THF (1.1 L)
at 0 °C was added MeMgBr (1 M in toluene, 2.8 mol) at a rate so
as to maintain internal temperature below 5 °C. The resulting
mixture was stirred at 0 °C for 2 h and 15 °C for 3 h. The mixture
was recooled to 5 °C, and additional MeMgBr (0.14 mol) was
added. The mixture was stirred at 15 °C for another 1.5 h. The
mixture was extracted with EtOAc and 15% aqueous NH4Cl. The
organic extract was concentrated. The residue was dissolved in
dichloromethane (DCM) and passed through a short pad of silica
gel, eluting with DCM, 5% EtOAc in DCM. The filtrate was
concentrated to give a white solid that was recrystallized from
EtOAc/heptane afforded 5 (186 g, 75% yield). MS (ESI+) m/z 355.4
1
(M + H)+. H NMR (400 MHz, CDCl3) δ 8.00 (s, br, 1H), 7.83
(s, 1H), 7.68 (s, 1H), 7.08 (d, 1H, J ) 8.60 Hz), 6.97 (dd, 1H),
6.35 (s, 1H), 2.78 (s, 3H), 2.46 (s, 3H), 1.80 (s, OH), 1.70 (s, 6H).
4-(4-Fluoro-2-methyl-1H-indol-5-yloxy)-5-methylpyrrolo[2,1-
f][1,2,4]triazin-6-ol (6). To a solution of BF3/OEt2 (120 mL, 0.948
mol) in DCM (200 mL) at 0 °C was added H2O2 (50% aqueous
solution, 4.6 mL, 0.079 mol). The mixture was stirred at 0 °C for
30 min and then cooled to -20 °C. To this mixture was added a
solution of 5 (20 g, 0.0564 mol) in DCM (400 mL) via cannula at
a rate so as to keep the reaction temperature between -15 to -25
°C. The resulting mixture was stirred at -15 °C for 40 min. The
reaction was quenched with 20% aq Na2SO3 (200 mL) and 33%
aq ethanolamine (300 mL) and stirred below 0 °C for 2 h. The
organic layer was then separated, and the aqueous layer was
extracted with EtOAc. The combined extracts were washed with
5% aq citric acid, 10% aq NaHCO3, water, and brine, dried, and
then concentrated to give an orange foam. The crude material was
dissolved in THF and loaded to a Florisil column, eluting with 30%
EtOAc/heptane. The desired fractions were concentrated in vacuo
and recrystallized from EtOAc/heptane. The solid was collected
and washed with heptane to afford 6 (9.1 g, 52% yield) as an off-

1980 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
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J. C.; Kim, S.-H.; Leavitt, K.; Mathur, A.; Leith, L.; Chao, S.; Wautlet,
B.; Mortillo, S.; Jayaseelan Sr., R.; Kukral, D.; Hunt, J.; Kamath, A.;
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Acknowledgment. The authors thank the Discovery Ana-
lytical Sciences Department at BMS for obtaining high
resolution MS analyses and enantiomeric excess determina-
tions.
Supporting Information Available: Characterization data for
chiral purity determination of 1, 8, and 9, prodrugs 7–20, and a
table of reaction yields and HPLC analysis data for key compounds.
This material is available free of charge via the Internet at http://
pubs.acs.org.
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