Cyclopenta[g]quinazolinone-based inhibitors of thymidylate synthase targeting α-folate receptor overexpressing tumours: synthetic approaches to 4-{N-[(6RS)-2-hydroxymethyl-4-oxo-3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-6-yl]-N-(prop-2-ynyl)amino}benz

Article abstract of DOI:10.1016/j.tet.2006.11.092

An advanced intermediate for the synthesis of cyclopenta[g]quinazolinone-based antifolates such as (6RS)-CB300945 was prepared by a convergent methodology. The oxo-functionality required for the formation of the C-6-N-10 bond in 4 was introduced in the in

Full text of DOI:10.1016/j.tet.2006.11.092

Tetrahedron 63 (2007) 1537–1543
Cyclopenta[g]quinazolinone-based inhibitors of thymidylate
synthase targeting a-folate receptor overexpressing tumours:
synthetic approaches to 4-{N-[(6RS)-2-hydroxymethyl-4-
oxo-3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-
6-yl]-N-(prop-2-ynyl)amino}benzoic acid
*
Vassilios Bavetsias, Elisa A. Henderson and Edward McDonald
Department of Chemistry, Cancer Research UK Centre for Cancer Therapeutics at The Institute of Cancer Research,
Cancer Research UK Laboratory, 15 Cotswold Road, Sutton, Surrey SM2 5NG, UK
Received 24 August 2006; revised 10 November 2006; accepted 30 November 2006
Abstract—An advanced intermediate for the synthesis of cyclopenta[g]quinazolinone-based antifolates such as (6RS)-CB300945 was pre-
pared by a convergent methodology. The oxo-functionality required for the formation of the C-6–N-10 bond in 4 was introduced in the initial
steps of the synthesis, then the tricyclic ring was constructed and finally the propargyl group was introduced using the (propargyl)Co2(CO)6+
complex without the need to protect the N-3–H or 2-hydroxymethyl functionalities.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
non-enzymatic route via a (propargyl)Co2(CO)+6 complex13
starting from 5-acetamido-6-bromoindan-1-one (13).14,15
Cyclopenta[g]quinazolinone-based antifolates have been
reported as potent inhibitors of the thymidylate synthase
(TS) enzyme1–3 that is an established target in cancer chemo-
therapy.4,5 It was also reported that certain compounds of
this class could utilise the a-folate receptor (a-FR) to enter
cells.3,6,7 The a-folate receptor is overexpressed in many car-
cinomas,8–11 and (6RS)-CB300638 (1), (6RS)-CB300945 (2)
(Fig. 1) displayed selectivity for cells that express the a-FR
(e.g., A431-FBP) over those without the a-FR (A431).3
Both (6RS)-CB300638 (1) and (6RS)-CB300945 (2) are
potent inhibitors of thymidylate synthase3 (for (6RS)-
CB300638 (1), L1210 TS Kiapp¼0.42 nM).1,3
2. Results
Access to 2-hydroxymethylcyclopenta[g]quinazolinone-
based antifolates such as (6RS)-CB300945 (2) was gained
via the intermediate 4 or its 2-hydroxymethyl ester protected
form, prepared in a linear fashion via a multistep synthesis
A linear multistep synthesis has been developed for the prep-
aration of this class of compounds with the benzoic acid de-
rivatives 3 and 4 (or their protected forms) being the crucial
intermediates.1–3 The first synthesis of 3 was achieved via
the N-10-alkylation of a suitably protected glutamate deriv-
ative of 3 using propargyl bromide, followed by removal
of the protecting groups and then enzymatic cleavage of
the glutamyl residue.1,12 Crystallographic analysis of a
derivative of 3 provided an unequivocal confirmation of its
structure.12 Subsequently, compound 3 was prepared by a
Keywords: Cyclopenta[g]quinazolinones; Dicobalt hexacarbonyl complex;
Antifolates.
* Corresponding author. E-mail: vassilios.bavetsias@icr.ac.uk
Figure 1.
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.11.092

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V. Bavetsias et al. / Tetrahedron 63 (2007) 1537–1543
Scheme 1. Conditions: (a) methoxyacetyl chloride, DMF, pyridine, rt; (b) Br2, AcOH; (c) CrO3, AcOH; (d) Zn(CN)2, Pd2(dba)3, dppf, DMA, 120 ꢀC; (e) H2O2,
NaOH, H2O, EtOH, 0–55 ꢀC; (f) 48% HBr, 120 ꢀC.
1
using 5-amino-6-carboxyindane as the chemical starting
point.3 In this route, the cyclopenta[g]quinazolinone ring
was first synthesised and the 2-hydroxymethyl substituent
was protected either as an acetate or trimethylacetate ester.3
Subsequent low yielding 6-oxo functionalisation facilitated
the C-6–N-10 bond formation via a reductive amination re-
action allowing the introduction of the p-aminobenzoate
moiety. Finally, the N-10-propargyl group was introduced
via a Nicholas reaction with (propargyl)Co2(CO)+6.3
had an H NMR identical to that of a sample synthesised
as described in Scheme 1. In the next step, cyanation of
the aryl bromide 9 was performed using Zn(CN)2 in DMA
under Pd-catalysis to afford 10 in 69% yield. The indanone
derivative 10 was then cyclised to the 2-methoxymethylcy-
clopenta[g]quinazolinone 11 by treatment with H2O2 and
NaOH in EtOH/H2O. At this stage, prior to the construc-
tion of the C-6–N-10 bond, it was attempted to generate the
2-hydroxymethyl functionality by cleaving the methyl ether
in 11 with a protic or a Lewis acid. Disappointingly, it was
not possible to form 12 in a workable yield, since all the
attempted conditions were either low yielding or completely
unsuccessful. The highest yield (w20%) was obtained by
heating 11 with 48% HBr at 120 ꢀC for 3 h.
The promising biochemical profile of compound 23 promp-
ted us to search for a convergent route to 4 in order to estab-
lish an alternative synthetic pathway to (6RS)-CB300945
(2), and facilitate the preparation of additional cyclopen-
ta[g]quinazolinone-based antifolates. We decided to investi-
gate two approaches, and in both cases the oxo-functionality
that is required for the formation of the C-6–N-10 bond was
efficiently introduced in the initial steps of the synthesis
(Schemes 1 and 3).
Scheme 2. Conditions: (a) 48% HBr, 70 ꢀC; (b) methoxyacetyl chloride,
DMF, pyridine, rt.
In the first approach, the aim was to first construct the tricy-
clic system (Scheme 1) and then introduce the tert-butyl 4-
aminobenzoate moiety followed by the introduction of the
propargyl group. The synthesis started with 5-aminoindane
(5), which was converted into the methoxyacetamide deriv-
ative 6 by treatment with methoxyacetyl chloride in DMF
using pyridine as base. Methoxyacetyl chloride was utilised
since it was envisaged that the 2-hydroxymethyl substituent
of the cyclopenta[g]quinazolinone ring could be generated at
a later stage from the methoxymethyl group via a demethyl-
ation reaction. Bromination of 6 was accomplished using
Br2/AcOH, and oxidation of 7 was performed under condi-
tions analogous to those utilised for the oxidation of its
2-acetamido counterpart.13,14 The indan-1-one 9 was iso-
lated as the major product (55%) of the oxidation reaction,
and only a small amount (3%) of indanone 8 was obtained.
Adopting the reaction conditions reported for the oxidation
of 5-acetamido-6-bromoindane15 resulted in obtaining the
ketone 9 in a higher yield (72%).
In the second approach, we were planning to first form the
C-6–N-10 bond, then construct the tricyclic scaffold and
generate the 2-hydroxymethyl functionality, and finally
introduce the propargyl group via a (propargyl)Co2(CO)6+
complex (Scheme 3) in a fashion similar to that reported
for the synthesis of 3.13 The synthesis started with 5-amino-
6-bromoindan-1-one (14) (Schemes 2 and 3), which was
converted into 15 by treatment with benzyloxyacetyl chlo-
ride in DMF. By using benzyloxyacetyl chloride it was
anticipated that the 2-hydroxymethyl substituent could be
generated by the Pd-catalysed hydrogenolysis of the benzyl
(Bn) group. Next the C-6–N-10 bond was formed by the
reductive amination of the ketone 15 with tert-butyl
4-aminobenzoate.16 For this transformation, the highest yield
(85%) was obtained when the reductive amination reaction
was performed using decaborane in methanol/dichloro-
methane.3,13,17 Cyanation of the aryl bromide 16 was
achieved by heating with copper(I) cyanide in 1-methyl-2-
pyrrolidinone (NMP) at 150 ꢀC. Cyclisation of 17 to give
the cyclopenta[g]quinazolinone derivative 18 was effected
by treatment with H2O2 and NaOH in EtOH/H2O. Hydro-
genolysis of the benzyloxymethyl ether 18 was performed
For the assignment of the regiochemistry in the oxidation
products 8 and 9 (Scheme 1), access to the indanone 9 was
also gained via 5-amino-6-bromoindan-1-one (14), which
was obtained from the known compound 1313–15 as shown in
Scheme 2. The methoxyacetamido derivative 9 (Scheme 2)

V. Bavetsias et al. / Tetrahedron 63 (2007) 1537–1543
1539
Scheme 3. Conditions: (a) benzyloxyacetyl chloride, DMF, pyridine, rt; (b) tert-butyl 4-aminobenzoate, 4-toluenesulfonic acid, NaBH3CN, AcOH or tert-butyl
4-aminobenzoate, CH2Cl2/MeOH, decaborane; (c) CuCN, NMP, 150 ꢀC; (d) H2O2, NaOH, H2O, EtOH, 0–55 ꢀC; (e) EtOH, 10% Pd/C, 50 ꢀC; (f) CH2Cl2,
DME, i-Pr2NEt, rt; (g) Fe(NO3)3, EtOH, rt; (h) TFA/CH2Cl2, rt; (j) (i) TFA/CH2Cl2, rt; (ii) 1 N NaOH, MeOH/H2O, rt.
in EtOH using 10% Pd/C to afford the 2-hydroxymethyl
substituted cyclopenta[g]quinazolinone 19. It should be
noted that heating of the reaction mixture at 50 ꢀC for several
hours was required for the hydrogenolysis to take place. The
propargyl group was next introduced on the N-10-position
by reacting 19 with (propargyl)Co2(CO)+6BF4ꢁ followed by
demetallation (Scheme 3).13,18 The propargylated derivative
21 was obtained in 53% yield from 19 without the need
to protect the N-3–H and 2-hydroxymethyl functionalities.
Finally, the tert-butyl ester was cleaved with TFA to afford
the benzoic acid derivative 4 as a racemic mixture, as it
was confirmed by chiral HPLC that indicated two peaks
(tR¼10.75, 12.27 min) for compound 4 in a ratio 1:1. As ex-
propargyl synthon without the need to protect the N-3–H or
2-hydroxymethyl functionalities.
3. Experimental
3.1. General
Thin layer chromatography (TLC) was performed on pre-
coated sheets of silica 60F254 (Merck Art 5735) and visual-
ised under UV light. Merck silica 60 (Art 15111) was used in
flash column chromatography. Column chromatography was
also performed on a FlashMaster personal unit (Jones Chro-
matography) using isolute silica columns. Petrol refers to
light petroleum (bp 60–80 ꢀC). Electrospray ionisation
(ESI) mass spectra were recorded using a TSQ 700 triple
quadrupole mass spectrometer (Finnigan MAT) fitted with
an electrospray ionisation source (Analytica). Proton NMR
spectra were recorded using a Bruker AC250 spectrometer
at 250 MHz. Field strengths are expressed in units of d (ppm)
relative to tetramethylsilane as an internal standard, and
peak multiplicities are designated as follows: s, singlet; d,
doublet; dd, doublet of doublets; dm, doublet of multiplets;
t, triplet; q, quartet, br s, broad singlet, m, multiplet.
High performance liquid chromatography (HPLC) analyses
were performed using a Waters system. The system used a
model 510 solvent delivery system, model 680 automated
gradient controller, model U6K injector and model M-490
programmable wavelength detector set to monitor at 230
1
pected, the H NMR of 4 was identical to that of a sample
derived from the known compound 223 by TFA and alkaline
cleavage of the tert-butyl and trimethylacetate esters,
respectively (Scheme 3).3
In summary, two new synthetic approaches to 4 were inves-
tigated, and a new convergent route to 4 was established. The
oxo-functionality required for the formation of the C-6–N-
10 bond in 4 was efficiently introduced in the initial steps
of the synthesis, and the benzyloxymethyl ether was used
to mask the hydroxymethyl functionality, which was gener-
ated after the introduction of the p-aminobenzoate moiety
and the formation of the cyclopenta[g]quinazolinone ring.
Subsequently, the N-10-propargyl substituent was intro-
duced utilising the (propargyl)Co2(CO)+6 as an electrophilic

1540
V. Bavetsias et al. / Tetrahedron 63 (2007) 1537–1543
and 280 nm. Retention times were determined on a Trivector
Trilab 3000 multichannel chromatography data system. Chi-
ral separations were performed on a 25 cmꢂ0.46 cm Astec
cyclobond I (cyclodextrin b) column (Astec, Advanced Sep-
aration Technologies Ltd., UK) and eluted isocratically with
different ratios of (25 mM Na2HPO4/25 mM NaH2PO4,
1:1 v/v)/CH3CN and a flow rate of 1 mL/min. LCMS analy-
sis was conducted using gradient elution (MeOH/0.1%
HCO2H in H2O) and a Supelco Discovery C18 HPLC col-
umn (5 cmꢂ0.46 cm, 5 mm). Samples were injected using
a Gilson 215 liquid handler. The HPLC system employed
a Thermoseparations P4000 quaternary pump and UV
2000 detector operating at 254 nm. HPLC eluent passed di-
rectly into an LCQ ion trap mass spectrometer (Finnigan
LCQ) operating in electrospray ionisation mode. Fast atom
bombardment (FAB) mass spectra were determined with
VG ZAB-SE spectrometer. Melting points were determined
on a Kofler block and are uncorrected. Elemental analyses
were determined by C.H.N. Analysis Ltd., Leicester, UK
or Warwick Analytical Service, University of Warwick Sci-
ence Park, Coventry, UK.
heated to 55 ꢀC was added dropwise a solution of CrO3
(1.2 g, 12.0 mmol) in aqueous glacial acetic acid (7 mL;
1:1 v/v) over a 15 min period. The reaction mixture was
then stirred at this temperature for 45 min. The reaction mix-
ture was cooled in an ice-bath, then isopropanol (4 mL) was
added and the mixture was stirred at this temperature for
10 min before being concentrated in vacuo. The black
residue was broken up with a spatula with the aid of water
and then partitioned between water (50 mL) and EtOAc
(150 mL). The aqueous layer was extracted with further
EtOAc (2ꢂ40 mL); the combined extracts were dried
(Na2SO4), and concentrated in vacuo to give an off-white
residue. Purification by column chromatography on silica
(5% EtOAc in dichloromethane) afforded in order of elution:
6-bromo-5-methoxyacetamidoindan-1-one (9) as a white
solid, which was further purified by trituration with EtOAc/
hexanes (1:5 v/v): 0.50 g (55%), mp 162–163 ꢀC; 1H NMR
(250 MHz, CDCl3) 2.72 (m, 2H, 2-CH2), 3.11 (m, 2H,
3-CH2), 3.57 (s, 3H, OCH3), 4.09 (s, 2H, 2-CH2OMe),
7.95 (s, 1H) and 8.65 (s, 1H) (4-H, 7-H), 9.27 (s, 1H,
CONH); MS (ESI, m/z) 298, 300 [(M+H)+, 100%, 97%];
found: C, 48.13; H, 3.99; N, 4.70; Br, 26.95; C12H12BrNO3
requires C, 48.34; H, 4.06; N, 4.70; Br, 26.80%, followed
by 6-bromo-5-methoxyacetamidoindan-3-one (8) as a solid,
which was further purified by trituration with EtOAc/
hexanes (1:5 v/v): 0.026 g, (3%), mp 149–151 ꢀC;
1H NMR (250 MHz, CDCl3) 2.71 (m, 2H, 2-CH2), 3.01 (m,
2H, 1-CH2), 3.56 (s, 3H, OCH3), 4.08 (s, 2H, 2-CH2OMe),
7.73 (s, 1H) and 8.71 (s, 1H) (4-H, 7-H), 8.97 (s, 1H,
CONH); MS (ESI, m/z) 298, 300 [(M+H)+, 100%, 98%];
found: C, 47.95; H, 3.96; N, 4.59; Br, 26.63; C12H12BrNO3
requires C, 48.34; H, 4.06; N, 4.70; Br, 26.80%.
3.1.1. 5-Methoxyacetamidoindane (6). To a solution of
5-aminoindane (4.66 g, 35.0 mmol) in anhydrous DMF
(26 mL) was slowly added methoxyacetyl chloride (5.70 g,
52.50 mmol) followed by pyridine (8.5 mL, 105.0 mmol).
The red solution was stirred at room temperature for 3.5 h
under argon, then it was partitioned between EtOAc
(200 mL) and 1 M HCl (120 mL). The organic layer was
washed with more 1 M HCl (120 mL), brine (100 mL), dried
(Na2SO4) and concentrated in vacuo. The residue was tritu-
rated with diethyl ether; the white precipitate was collected
by filtration, washed with diethyl ether (10 mL) and dried to
afford the title compound (5.93 g, 83%), mp 104–105 ꢀC;
1H NMR (250 MHz, CDCl3) 2.06 (m, 2H, 2-CH2), 2.87
(m, 4H, 1-CH2 and 3-CH2), 3.50 (s, 3H, OCH3), 4.00
(s, 2H, 2-CH2OMe), 7.22 (m, 2H, 6-H, 7-H), 7.52 (s, 1H,
4-H), 8.18 (s, 1H, CONH); MS (ESI, m/z) 206 [(M+H)+,
100%]; found C, 70.10; H, 7.38; N, 6.81; C12H15NO2
requires C, 70.22; H, 7.37; N, 6.82%.
Method B:15 to a solution of 6-bromo-5-methoxyacetami-
doindane (5.00 g, 17.62 mmol) in AcOH (30 mL) was added
a solution of CrO3 (6.00 g, 60.00 mmol) in H2O (12 mL) en-
suring that the temperature remained between 25 and 30 ꢀC.
The mixture was stirred at room temperature for 30 min,
then a further portion of CrO3 (0.50 g, 5.00 mmol) in H2O
(2.5 mL) was added and the mixture was stirred at room tem-
perature for 1 h. H2O (3ꢂ50 mL) was added with 2 min of
stirring between additions resulting in the product crystallis-
ing from solution. The mixture was cooled to 0 ꢀC and the
crude product collected by filtration and dried in vacuo
over P2O5. The residue was purified by column chromato-
graphy eluting with 4% EtOAc in CH2Cl2 to yield the
desired product as a white solid (3.78 g, 72%).
3.1.2. 6-Bromo-5-methoxyacetamidoindane (7). A mix-
ture of 5-methoxyacetamidoindane (5.50 g, 0.027 mol) and
glacial acetic acid (25 mL) was cooled in an ice-water
bath (w10 ꢀC). Bromine (1.5 mL, 0.029 mol) was then added
dropwise over a 20 min period while the temperature was
kept between 10 and 15 ꢀC. The reaction mixture was stirred
for a further hour, then poured into an ice-water bath
(100 mL) and the reaction flask washed with a further por-
tion of water (70 mL). The precipitate was collected by fil-
tration, washed with water (150 mL) and dried in vacuo
over P2O5 to afford the title compound (6.98 g, 91%), mp
84–86 ꢀC; 1H NMR (250 MHz, CDCl3) 2.09 (m, 2H,
2-CH2), 2.88 (m, 4H, 1-CH2 and 3-CH2), 3.55 (s, 3H,
OCH3), 4.04 (s, 2H, 2-CH2OMe), 7.34 (s, 1H) and 8.22 (s,
1H) (4-H, 7-H), 8.83 (s, 1H, CONH); MS (ESI, m/z) 284,
286 [(M+H)+, 98%, 100%]; found C, 50.62; H, 4.93; N,
4.92; Br, 28.05; C12H14BrNO2 requires C, 50.72; H, 4.97;
N, 4.93; Br, 28.12%.
Method C: to a solution of 5-amino-6-bromoindan-1-one
(14) (0.113 g, 0.5 mmol) in anhydrous DMF (1 mL) was
slowly added methoxyacetyl chloride (0.081 g, 0.70 mmol)
followed by pyridine (0.20 mL, 2.5 mmol). The reaction
mixture was stirred at room temperature for 2 h under argon,
then it was partitioned between EtOAc (50 mL) and 1 M
HCl (30 mL). The organic layer was washed with further
1 M HCl (30 mL), brine (30 mL), dried (Na2SO4) and con-
centrated in vacuo. Purification by column chromatography
(5% EtOAc in dichloromethane) afforded the ketone 9
(0.073 g) as white solid.
3.1.3. 6-Bromo-5-methoxyacetamidoindan-1-one (9).
Method A: to a solution of 6-bromo-5-methoxyacetamido-
indane (0.85 g, 3.0 mmol) in glacial acetic acid (7 mL)
3.1.4. 6-Cyano-5-methoxyacetamidoindan-1-one (10). To
a solution of 6-bromo-5-methoxyacetamidoindan-1-one
(3.77 g, 12.65 mmol) in anhydrous DMA (75 mL) was

V. Bavetsias et al. / Tetrahedron 63 (2007) 1537–1543
1541
added Zn(CN)2 (0.91 g, 7.71 mmol), Pd2(dba)3 (0.49 g,
0.54 mmol) and dppf (0.57 g, 1.08 mmol). The mixture was
heated at 120 ꢀC for 2 h under argon, then cooled to room
temperature and partitioned between EtOAc (300 mL) and
2 M NH4OH (250 mL). The organic extract was washed
with brine (250 mL), dried (Na2SO4) and the solvent
removed in vacuo. The residue was purified by column chro-
matography eluting with 10% EtOAc in CH2Cl2 to yield the
desired product as a white solid (2.13 g, 69%), mp 170 ꢀC;
1H NMR (250 MHz, CDCl3) d 2.76 (m, 2H, 2-CH2), 3.23
(m, 2H, 3-CH2), 3.59 (s, 3H, CH3), 4.11 (s, 2H, OCH2),
8.00 (s, 1H, 7-H), 8.72 (s, 1H, 4-H), 9.26 (br s, 1H, NH);
MS (ESI, m/z) 245 [(M+H)+, 100%]; found C, 63.64;
H, 4.90; N, 11.40; C13H12N2O3 requires C, 63.93; H, 4.95;
N, 11.47%.
(150 mL). The aqueous layer was extracted with further
EtOAc (100 mL) and the combined extracts were washed
with 1 M HCl (100 mL) and brine (100 mL), dried (Na2SO4)
and concentrated in vacuo. Purification by column chro-
matography (40% EtOAc in hexane and then 2% EtOAc
in CH2Cl2/hexane (9:1 v/v)) afforded a yellow solid. This
solid was reprecipitated from CH2Cl2/hexane to obtain a
pale yellow solid (2.07 g, 75%), mp 120 ꢀC; 1H NMR
(250 MHz, CDCl3) 2.72 (m, 2H, 2-CH2), 3.10 (m, 2H,
3-CH2), 4.18 (s, 2H) and 4.72 (s, 2H) (PhCH2 and
OCH2CO), 7.39 (m, 5H, PhCH2), 7.95 (s, 1H) and 8.65 (s,
1H) (4-H and 7-H), 9.39 (s, 1H, CONH); MS (ESI, m/z)
396, 398 [(M+Na)+, 50%]; 374, 376 [(M+H)+, 100%];
found: C, 57.53; H, 4.23; N, 3.71; Br, 21.35; C18H16BrNO3
requires C, 57.77; H, 4.31; N, 3.74; Br, 21.35%.
3.1.5. 2-Methoxymethyl-3,4,7,8-tetrahydro-6H-cyclo-
penta[g]quinazolin-4,6-dione (11). Toamixtureof6-cyano-
5-methoxyacetamidoindan-1-one (2.00 g, 8.20 mmol), EtOH
(25 mL), H2O (5.25 mL) and 30% H2O2 (7.25 mL) cooled in
an ice-bath was added granulated NaOH pellets (0.55 g,
13.42 mmol). The mixture was stirred at room tempera-
ture for 15 min, then slowly heated to 55 ꢀC until a
homogeneous solution was obtained before being allowed
to cool to room temperature. The solvent was removed
in vacuo and the residue was suspended in H2O (300 mL),
then heated to 50 ꢀC for 5 min. The solution was again
cooled to room temperature and acidified to pH 4 with
1 M HCl. The resulting precipitate was collected by filtration
and dried in vacuo over P2O5 to yield the desired product as
a white solid (1.93 g, 96%), mp 257–259 ꢀC; 1H NMR
(250 MHz, DMSO-d6) d 2.71 (m, 2H, 7-CH2), 3.24 (m,
2H, 8-CH2), 3.37 (s, 3H, CH3), 4.36 (s, 2H, 2-CH2), 7.76
(s, 1H, 9-H), 8.28 (s, 1H, 5-H); MS (FAB, m/z) 245
[(M+H)+, 100%]; HRMS: measured 245.0933; calculated
for C13H13N2O3 (M+H)+: 245.0926.
3.1.8. tert-Butyl 4-[N-(5-(2-benzyloxy-ethanoylamino)-
6-bromoindan-1-yl)amino]-benzoate (16). Method A: to
a round-bottom flask containing 5-benzyloxyacetamido-
6-bromoindan-1-one (0.750 g, 2.0 mmol), 4-toluenesulfonic
acid (0.030 g), tert-butyl 4-aminobenzoate16 (0.540 g,
2.8 mmol) was added anhydrous DME (24 mL). An Aldrich
azeotropic distillation apparatus containing molecular sieves
˚
(3 A) was fitted to the reaction flask, which was then placed
in an oil bath preheated to 115 ꢀC. The mixture was stirred at
this temperature for 3.5 h under argon, then cooled to room
temperature. A solution of Na(CN)BH3 in THF (1 M; 2.8 mL,
2.8 mmol) was then added followed by AcOH (0.094 mL).
The reaction mixture was stirred at room temperature for
2.5 h, then it was partitioned between EtOAc (200 mL)
and saturated aqueous NaHCO3 (150 mL). The aqueous
layer was extracted with further EtOAc (100 mL) and the
combined extracts were washed with brine (100 mL), dried
(Na2SO4) and concentrated in vacuo. Purification by column
chromatography (EtOAc/petroleum ether (1:1 v/v)) afforded
a yellow solid. This solid was reprecipitated from EtOAc/
hexane to obtain the desired compound as a pale yellow solid
(0.233 g, 21%), mp 150–151 ꢀC; 1H NMR (250 MHz,
CDCl3,) 1.56 (s, 9H, C(CH3)3), 1.92 (m, 1H) and 2.63 (m,
1H) (2-CH2 indanyl), 2.82–3.00 (m, 2H, 3-CH2 indanyl),
4.15 (s, 2H) and 4.71 (s, 2H) (PhCH2 and OCH2CO), 4.24
(d, J¼8.1 Hz, 1H, N10–H), 5.02 (m, 1H, 1-CH indanyl),
6.64 (d, J¼8.7 Hz, 2H, 3,5-ArH), 7.39 (m, 5H, PhCH2),
7.50 (s, 1H) and 8.33 (s, 1H) (4-H and 7-H), 7.85 (d,
J¼8.7 Hz, 2H, 2,6-ArH), 9.06 (s, 1H, CONH); MS (ESI,
m/z) 575, 573 [(M+Na)+, 100%, 98%]; found: C, 63.03; H,
5.65; N, 5.04; Br, 14.46; C29H31BrN2O4 requires C, 63.16;
H, 5.67; N, 5.08; Br, 14.49%.
3.1.6. 5-Amino-6-bromoindan-1-one (14). A solution of
5-acetamido-6-bromoindan-1-one13–15 (2.85 g, 10.60 mmol)
in 48% HBr (90 mL) was placed in an oil bath preheated to
70 ꢀC. The mixture was stirred at this temperature for
1.5 h, then cooled in an ice-bath and diluted with aqueous
NaOH (1 M, 50 mL). The pH was then adjusted tow5 with
aqueous NaOH (50% w/w). The brown solid was collected
by filtration, washed with water, and dried in vacuo over
P2O5. Purification by column chromatography (8% EtOAc
in CH2Cl2) gave an orange solid. This solid was triturated
with 30% hexane in diethyl ether to obtain a pale brown solid
(1.80 g, 75%), mp 209–211 ꢀC (lit.15 199–200 ꢀC; prepared
by alkaline amide hydrolysis); 1H NMR (250 MHz,
CDCl3) 2.65 (m, 2H, 2-CH2), 2.99 (m, 2H, 3-CH2), 4.65
(br s, 2H, NH2), 6.73 (s, 1H) and 7.86 (s, 1H) (4-H and
7-H); MS (ESI, m/z) 226, 228 [(M+H)+, 100%]; found:
C, 47.59; H, 3.49; N, 6.11; Br, 35.16; C9H8BrNO requires
C, 47.82; H, 3.57; N, 6.20; Br, 35.34%.
Method B: to a solution of 5-benzyloxyacetamido-6-bro-
moindan-1-one (3.45 g, 9.22 mmol) in anhydrous methanol
(330 mL) and CH2Cl2 (40 mL) was added tert-butyl 4-ami-
nobenzoate (1.94 g, 10.05 mmol) followed by decaborane
(0.310 g). The reaction mixture was stirred at room temper-
ature overnight before being concentrated in vacuo. Purifica-
tion by column chromatography (40% EtOAc in petroleum
ether (60–80 ꢀC)) afforded the desired product: 4.30 g,
(85%).
3.1.7. 5-Benzyloxyacetamido-6-bromoindan-1-one (15).
To a stirred solution of 5-amino-6-bromoindan-1-one
(1.70 g, 7.5 mmol) in anhydrous DMF (15 mL) was added
slowly benzyloxyacetyl chloride (2.07 g, 11.25 mmol) fol-
lowed by pyridine (3.0 mL, 37.5 mmol). The reaction
mixture was stirred at room temperature for 18 h under argon
and then partitioned between EtOAc (200 mL) and 1 M HCl
3.1.9. tert-Butyl 4-[N-(5-(2-benzyloxy-ethanoylamino)-
6-cyanoindan-1-yl)amino]-benzoate (17). To a stirred
solution of tert-butyl4-[N-(5-(2-benzyloxy-ethanoylamino)-
6-bromoindan-1-yl)amino]-benzoate (0.210 g, 0.38 mmol)

1542
V. Bavetsias et al. / Tetrahedron 63 (2007) 1537–1543
in anhydrous NMP (2.2 mL) was added CuCN (0.068 g,
0.76 mmol). The reaction flask was placed in an oil bath pre-
heated to 150 ꢀC and it was stirred at this temperature for 3 h
under argon. The mixture was then allowed to cool to room
temperature and poured into a mixture of aqueous ammonia
(2 mL) and ice-water (5 mL). This mixture was stirred at
room temperature for 5 min, the brown precipitate was then
collected by filtration and washed with water. This preci-
pitate was then suspended in CH2Cl2 (70 mL), dried
(Na2SO4) and concentrated in vacuo. Purification of the
residue by column chromatography, eluting with 35%
EtOAc in hexane, afforded a brown solid (0.084 g, 45%),
and 2.57 (m, 1H) (7-CH2), 2.90–3.17 (m, 2H, 8-CH2), 4.38
(d, J¼6.0 Hz, 2H, 2-CH2OH), 5.17 (m, 1H, 6-CH), 5.54 (t,
J¼6.1 Hz, 1H, CH2OH), 6.79 (d, J¼8.8 Hz, 2H, 30,50-
ArH), 6.91 (d, J¼7.8 Hz, 1H, N10–H), 7.51 (s, 1H) and
7.91 (s, 1H) (5-H and 9-H), 7.68 (d, J¼8.8 Hz, 2H, 20,60-
ArH), 11.83 (s, 1H, CONH); MS (ESI, m/z) 408 [(M+H)+,
t
65%], 352 [(Mꢁ Bu)+, 100%], 215 (60%); found: C,
67.41; H, 6.20; N, 10.17; C23H25N3O4 requires C, 67.80;
H, 6.18; N, 10.31%.
3.1.12. tert-Butyl 4-{N-[(6RS)-2-hydroxymethyl-4-oxo-
3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-6-yl]-N-
(prop-2-ynyl)amino}benzoate (21). To a round-bottomed
flask containing (propargyl)Co2(CO)+6BFꢁ4 13,19 (0.390 g,
0.95 mmol) under argon was added anhydrous dichloro-
methane (14 mL), a nearly clear solution was obtained. To
this solution a suspension of tert-butyl 4-{N-[(6RS)-2-hy-
droxymethyl-4-oxo-3,4,7,8-tetrahydro-6H-cyclopenta[g]-
quinazolin-6-yl]amino}benzoate (0.285 g, 0.71 mmol) in
anhydrous CH2Cl2 (14 mL) and DME (20 mL) was added
in one portion. The mixture was stirred at room temperature
for 10 min under argon, then diisopropylethylamine
(0.14 mL) was added and stirring was continued at room
temperature for 20 min. The reaction mixture was then par-
titioned between EtOAc (350 mL) and brine (100 mL). The
organic layer was washed with 10% aqueous citric acid
(100 mL) and brine (100 mL), dried (Na2SO4) and concen-
trated in vacuo. Purification by chromatography (silica iso-
lute 20 g, 70 mL column), on elution with 70% EtOAc in
CH2Cl2, gave a red solid (0.391 g, 76%), mp 190 ꢀC (dec);
1H NMR (250 MHz, DMSO-d6) 1.52 (s, 9H, C(CH3)3),
2.24 (m, 1H) and 2.60 (m, 1H) (7-CH2), 2.96–3.25 (m, 2H,
8-CH2), 4.37 (d, J¼5.9 Hz, 2H, 2-CH2OH), 4.58 (d,
J¼17.2 Hz, 1H) and 4.73 (d, J¼17.2 Hz, 1H) (N10–CH2),
5.55 (t, J¼6.2 Hz, 1H, CH2OH), 5.80 (t, J¼7.7 Hz, 1H,
6-CH), 6.68 (s, 1H, propargyl H), 7.01 (d, J¼8.8 Hz, 2H,
30,50-ArH), 7.56 (s, 1H) and 7.76 (s, 1H) (5-H and 9-H),
7.79 (d, J¼9.8 Hz, 2H, 20,60-ArH), 11.83 (s, 1H, CONH).
To a solution of this material (0.380 g, 0.52 mmol) in EtOH
(65 mL) was added Fe(NO3)3$9H2O (2.60 g, 6.5 mmol).
The mixture was stirred at room temperature for 2.5 h,
brine (w200 mL) was then added into the reaction mix-
ture that was extracted with EtOAc (3ꢂ150 mL). The com-
bined organic extracts were washed with brine (120 mL),
dried (Na2SO4) and concentrated in vacuo. Purification
by column chromatography, eluting with 5% MeOH in
EtOAc, gave an off-white solid (0.161 g, 70%), mp 195–
197 ꢀC; 1H NMR (250 MHz, DMSO-d6,) 1.52 (s, 9H,
C(CH3)3), 2.17 (m, 1H) and 2.55 (m, coincides with solvent
peak, 1H) (7-CH2), 2.90–3.20 (m, 3H, C^CH, 8-CH2), 3.87
(d, J¼18.7 Hz, 1H) and 4.10 (d, J¼18.7 Hz, 1H) (N10–CH2),
4.38 (d, J¼5.8 Hz, 2H, 2-CH2OH), 5.56 (br t, 1H, CH2OH),
5.78 (t, J¼8.7 Hz, 1H, 6-CH), 7.02 (d, J¼9.0 Hz, 2H,
30,50-ArH), 7.55 (s, 1H) and 7.80 (s, 1H) (5-H and 9-H),
7.76 (d, J¼9.8 Hz, 2H, 20,60-ArH), 11.82 (s, 1H, CONH);
MS (ESI, m/z) 468 [(M+Na)+, 60%], 446 [(M+H)+, 50%],
1
mp 194–195 ꢀC; H NMR (250 MHz, CDCl3) 1.55 (s, 9H,
C(CH3)3), 1.95 (m, 1H) and 2.64 (m, 1H) (2-CH2 indanyl),
2.99 (m, 2H, 3-CH2 indanyl), 4.13 (s, 2H) and 4.72 (s, 2H)
(PhCH2 and OCH2CO), 4.22 (d, J¼8.1 Hz, 1H, N10–H),
5.05 (m, 1H, 1-CH indanyl), 6.65 (d, J¼8.7 Hz, 2H,
3,5-ArH), 7.39 (m, 5H, PhCH2), 7.54 (s, 1H) and 8.37 (s,
1H) (4-H and 7-H), 7.86 (d, J¼8.7 Hz, 2H, 2,6-ArH), 9.06
(s, 1H, CONH); MS (ESI, m/z) 520 [(M+Na)+, 100%]; found:
C, 72.26; H, 6.26; N, 8.41; C30H31N3O4 requires C, 72.41; H,
6.28; N, 8.44%.
3.1.10. tert-Butyl 4-{N-[(6RS)-2-benzyloxymethyl-4-oxo-
3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-6-yl]-
amino}benzoate (18). To a stirred, ice-bath cooled mixture
of tert-butyl 4-[N-(5-(2-benzyloxy-ethanoylamino)-6-cya-
noindan-1-yl)amino]-benzoate (3.77 g, 7.59 mmol), EtOH
(70 mL) and H2O (11 mL) was added 30% H2O2 (8.05 mL)
followed by granulated NaOH pellets (0.640 g, 16.0 mmol).
The reaction mixture was stirred at 0 ꢀC for 10 min, then
placed in an oil bath preheated to 55 ꢀC and stirred at this
temperature for 1 h. The solvents were then removed
in vacuo; the residue was treated with H2O (80 mL) and
the pH was adjusted tow5 with 1 M HCl. The pale yellow
solid was collected by filtration, washed with H2O and
dried in vacuo over P2O5 (3.56 g, 95%), mp 194–195 ꢀC;
1H NMR (250 MHz, DMSO-d6) 1.52 (s, 9H, C(CH3)3),
1.90 (m, 1H) and 2.62 (m, 1H) (7-CH2), 2.90–3.17 (m,
2H, 8-CH2), 4.43 (s, 2H) and 4.60 (s, 2H) (PhCH2
and OCH2C]N), 5.18 (q, J¼7.4 Hz, 1H, 6-CH), 6.79
(d, J¼8.8 Hz, 2H, 30,50-ArH), 6.87 (d, J¼8.0 Hz, 1H,
N10–H), 7.34 (m, 5H, PhCH2), 7.54 (s, 1H) and 7.92
(s, 1H) (5-H and 9-H), 7.68 (d, J¼8.9 Hz, 2H, 20,60-
ArH), 12.20 (s, 1H, CONH); MS (ESI, m/z) 520
[(M+Na)+, 90%], 498 [(M+H)+, 100%]; found: C, 72.13;
H, 6.25; N, 8.38; C30H31N3O4 requires C, 72.41; H, 6.28;
N, 8.44%.
3.1.11. tert-Butyl 4-{N-[(6RS)-2-hydroxymethyl-4-
oxo-3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-6-
yl]amino}benzoate (19). To a solution of tert-butyl
4-{N-[(6RS)-2-benzyloxymethyl-4-oxo-3,4,7,8-tetrahydro-
6H-cyclopenta[g]quinazolin-6-yl]amino}benzoate (1.40 g,
2.8 mmol) in EtOH (150 mL) was added 10% Pd/C
(0.665 g). The mixture was stirred at 45 ꢀC for 3 h, then
more catalyst (0.200 g) was added and stirring was con-
tinued at 50 ꢀC for 6 h. The catalyst was removed by filtra-
tion, washed with EtOH and the filtrate was concentrated
in vacuo. Purification of the residue by column chromato-
graphy, eluting with 8% methanol in EtOAc, gave a white
solid (0.679 g, 60%), mp 265–266 ꢀC; 1H NMR
(250 MHz, DMSO-d6) 1.52 (s, 9H, C(CH3)3), 1.88 (m, 1H)
t
390 [(Mꢁ Bu)+, 70%], 215 (100%); found: C, 69.63;
H, 6.13; N, 9.31; C26H27N3O4 requires C, 70.09; H, 6.11;
N, 9.43%.
3.1.13. 4-{N-[(6RS)-2-Hydroxymethyl-4-oxo-3,4,7,8-tet-
rahydro-6H-cyclopenta[g]quinazolin-6-yl]-N-(prop-
2-ynyl)amino}benzoic acid (4). Method A: a solution of

V. Bavetsias et al. / Tetrahedron 63 (2007) 1537–1543
1543
tert-butyl 4-{N-[(6RS)-2-hydroxymethyl-4-oxo-3,4,7,8-tetra-
References and notes
hydro-6H-cyclopenta[g]quinazolin-6-yl]-N-(prop-2-ynyl)-
amino}benzoate (0.050 g, 0.11 mmol) in CH2Cl2 (1 mL)
and TFA (2.4 mL) was stirred at room temperature for
1 h. The solvents were then removed in vacuo and the resi-
due was treated with water (8 mL). The pH was adjusted
tow10 with 1 N NaOH (a clear solution was obtained) and
then tow4 with 1 M HCl, resulting in the product precipitat-
ing from solution. The white precipitate was collected by
filtration, washed with water and dried in vacuo over P2O5
to give the desired compound as a white solid (0.037 g,
88%), mp 173 ꢀC (decomposed); 1H NMR (250 MHz,
DMSO-d6) 2.26 (m, 1H, 7-CH2), 2.90–3.15 (m, 3H,
C^CH, 8-CH2), 3.85 (d, J¼18.3 Hz, 1H) and 4.10 (d,
J¼18.3 Hz, 1H) (N10–CH2), 4.38 (s, 2H, 2-CH2OH), 5.56
(br s, 1H, 2-CH2OH), 5.78 (t, J¼8.3 Hz, 1H, 6-CH), 7.03
(d, J¼9.0 Hz, 2H, 30,50-ArH), 7.55 (s, 1H) and 7.83 (s, 1H)
(5-H and 9-H), 7.81 (d, J¼8.5 Hz, 2H, 20,60-ArH); MS
(ESI, m/z) 390 [(M+H)+, 100%], 215 (20%); found: C,
61.53; H, 5.04; N, 9.57; C22H19N3O4$2.1H2O requires C,
61.86; H, 5.44; N, 9.84%.
1. Bavetsias, V.; Marriott, J. H.; Melin, C.; Kimbell, R.; Matusiak,
Z. S.; Boyle, F. T.; Jackman, A. L. J. Med. Chem. 2000, 43,
1910–1926.
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Method B: a solution of tert-butyl 4-{N-[(6RS)-2-(2,2-di-
methylpropionyloxymethyl)-4-oxo-3,4,7,8-tetrahydro-6H-
cyclopenta[g]quinazolin-6-yl]-N-(prop-2-ynyl)amino}benz-
oate (22)3 (0.150 g, 0.28 mmol) in CH2Cl2 (2 mL) and TFA
(6 mL) was stirred at room temperature for 1 h. The solvents
were removed in vacuo, the residue was triturated with ether
and the precipitate was collected by filtration and suspended
in water (5 mL) and MeOH (3 mL). A solution of aqueous
NaOH (1 N; 1.1 mL, 1.1 mmol) was then added and the
reaction mixture was stirred at room temperature for 8 h.
The pH of the solution was then adjusted to w5 with 1 M
HCl and the white precipitate was collected by filtration,
washed with water and dried in vacuo over P2O5 to give
the desired product 4 (0.086 g, 79%).
13. Bavetsias, V.; Clauss, R.; Henderson, E. A. Org. Biomol. Chem.
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Acknowledgements
The authors would like to acknowledge the leadership of
Professor A. L. Jackman in the folate receptor project and
thank her for the support and encouragement given through-
out these studies. The work of the Cancer Research UK
Centre for Cancer Therapeutics is funded primarily by
Cancer Research UK [CUK] Grant C309/A2187. We thank
BTG International for their support and assistance with
this project. We also thank Dr. Amin Mirza and Angela
Hayes for obtaining the ESI spectra.
15. Scheigetz, J.; Zamboni, R.; Roy, B. Synth. Commun. 1995, 25,
2791–2806.
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