Efficient synthesis and biological evaluation of some 2,4-diamino-furo[2,3- d]pyrimidine derivatives

Article abstract of DOI:10.1016/j.bmcl.2010.08.122

The carbodiimides 2, obtained from aza-Wittig reactions of iminophosphorane 1 with aromatic isocyanates, reacted with ammonia to give ethyl 3,4-dihydro-6-methyl-4-oxo-2-arylamino-furo[2,3-d]pyrimidine-5-carboxylate 3. Further reaction of 3 with POCl₃

Full text of DOI:10.1016/j.bmcl.2010.08.122

Bioorganic & Medicinal Chemistry Letters 20 (2010) 6188–6190
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Efficient synthesis and biological evaluation of some
2,4-diamino-furo[2,3-d]pyrimidine derivatives
Yang-Gen Hu a,c, , Yan Wang b, Shi-Ming Du c, Xiao-Bao Chen a, Ming-Wu Ding d,
⇑
⇑
a Institute of Medicinal Chemistry, Hubei Medical University, Shiyan 442000, China
b Institute of Basic Medical Sciences, Hubei Medical University, Shiyan 442000, China
c Department of Pharmacy, Taihe Hospital of Hubei Medical University, Shiyan 442000, China
d Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 May 2010
Revised 28 July 2010
Accepted 25 August 2010
Available online 16 September 2010
The carbodiimides2, obtained from aza-Wittig reactions of iminophosphorane1 with aromatic isocyanates,
reacted with ammonia to give ethyl 3,4-dihydro-6-methyl-4-oxo-2-arylamino-furo[2,3-d]pyrimidine-
5-carboxylate 3. Further reaction of 3 with POCl3 and various amines generated ethyl 4-alkylamino-2-aryla-
mino-6-methyl-furo[2,3-d]pyrimidine-5-carboxylate 5 in good yields. Their structures were confirmed by
1H NMR, EI-Ms, IR and elemental analysis. Compound 5b was further analyzed by single crystal X-ray dif-
fraction. Compound 5 exhibited cytotoxicity against two lung cancer cell lines. For example, compound
Keywords:
5a showed the best inhibition activities against A459 with IC50 0.8
lM.
Ethyl 4-alkylamino-2-arylamino-6-methyl-
furo[2,3-d]pyrimidine-5-carboxylate
Aza-Wittig reactions
Ó 2010 Elsevier Ltd. All rights reserved.
Antitumor activity
The derivatives of fused pyrimidines have shown remarkable
biological properties such as antitumor and antibacterial activi-
ties.1–3 Among them, furo[2,3-d]pyrimidines have been considered
as templates for drug discovery for many years with the inhibition
of dihydrofolate reductase (DHFR) as the primary target.4,5 More
recently, furopyrimidines have been found to be active as kinase
inhibitors.6,7 For example, Gangjee et al. recently reported a series
of compounds containing the backbone of 2,4-diaminofuropyrimi-
dines which have potent dual thymidylate synthase and dihydrofo-
late reductase inhibitors (Fig. 1), However, there are only few
reports on the synthesis of 4-alkylamino-2-arylamino-furopyrimi-
dines, which are of considerable interest as potential biologically
active compounds or pharmaceuticals.
Over past twenty years, the aza-Wittig reactions of imino-
phosphoranes have received increased attention in view of their
utility in the synthesis of nitrogen-containing heterocyclic com-
pounds.8–10 Annelation of ring systems with N-heterocycles by
means an aza-Wittig reaction has been widely utilized because
of the availability of functionalized iminophosphoranes. Recently
we have been interested in the synthesis of fused pyrimidinones
and imidazolones via aza-Wittig reaction, with the aim of evalu-
ating their biological activities.11–13 Here, we wish to reported a
R2
R1
N
NH2
N
R1
N
N
COOCH2CH3
CH3
N
R2
O
O
H2N
HN
Ar
Figure 1. 2,4-Diaminofuropyrimidines have potent dual thymidylate synthase and
dihydrofolate reductase inhibitors.
new efficient synthesis and antitumor activities of ethyl 4-alkyl-
amino-2-arylamino-6-methyl-furo[2,3-d]pyrimidine-5-carboxyl-
ate 5 from easily accessible iminophosphorane 1.14
Iminophosphorane 1 reacted with aromatic isocyanates to
give carbodiimides 2, which were allowed to react with NH3 to
give selectively ethyl 3,4-dihydro-6-methyl-4-oxo-2-arylamino-
furo[2,3-d]pyrimidine-5-carboxylates 315 in satisfactory yields at
room temperature. Compounds
3 were further converted to
functionalized ethyl 4-chloro-6-methyl-2-arylamino-furo[2,3-d]-
pyrimidine-5-carboxylates 416 via reaction with POCl3 at 80–85 °C
(88–95%, Scheme 1).
Ethyl 4-chloro-6-methyl-2-arylamino-furo[2,3-d]pyrimidine-5-
carboxylates 4 reacted with primary amines or secondary amines
in acetonitrile at 70–80 °C to give ethyl 4-alkylamino-2-arylamino-
6-methyl-furo[2,3-d]pyrimidine-5-carboxylate 5 in good yields17
(80–90%, Table 1, Scheme 2).
⇑
Corresponding authors.
E-mail addresses: huyangg111@yahoo.com.cn (Y.-G. Hu), ding5229@yahoo.
com.cn (M.-W. Ding).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.08.122

Y.-G. Hu et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6188–6190
6189
EtO2C
H3C
CO2Et
NH3
EtO2C
H3C
CO2Et
N
ArNCO
PPh3
NCNAr
O
O
2
1
O
Cl
N
EtO2C
EtO2C
H3C
POCl3
NH
H3C
O
O
N
NH
Ar
N
NH
Ar
3
4
4a: Ar = C6H5
4b: Ar = 3-CH3-C6H4
3a: Ar = C6H5
3b: Ar = 3-CH3-C6H4
Scheme 1.
Figure 2. Ortep diagram of the crystal structure of compound 5b (drawn at the 50%
thermal ellipsoids).
Table 1
Preparation of ethyl-4-alkylamino-2-arylamino-furo[2,3-d]pyrimidine-5-carboxyl-
ates 5
Table 2
In vitro cytotoxicity (IC50
5
a
,
l
M) of furo[2,3-d]pyrimidine
Compound
Ar
NR1R2
Conditions
(°C/h)
Yieldsa
(%)
Compound
A459
SPC-A-1
5a
5b
5c
5d
5e
5f
5g
5h
5i
Ph
Ph
Ph
Ph
4-Methylpiperazin-1-yl
n-Butylamino
iso-Propylamino
2-Hydroxyethylamino
Morpholino
n-Butylamino
Morpholino
4-Methylpiperazin-1-yl
Diethylamino
iso-Propylamino
70–80/5
70–80/6
70–80/6
70–80/5
70–80/6
70–80/5
70–80/5
70–80/6
70–80/6
70–80/6
81
85
87
80
90
84
86
80
82
85
5a
5b
5c
5d
5e
5f
5g
5h
5i
0.8
2.7
21.5
13.0
15.2
9.0
14.0
5.5
8.8
26.1
50.2
—
24.2
69.0
—
70.8
18.2
—
Ph
3-CH3–C6H4
3-CH3–C6H4
3-CH3–C6H4
3-CH3–C6H4
3-CH3–C6H4
5j
5j
8.6
46.3
a
Isolated yields based on ethyl 4-chloro-6-methyl-2-arylamino-furo[2,3-
a
IC50 is the concentration of compound required to
inhibit the cell growth by 50% compared to an
untreated control.
d]pyrimidine-5-carboxylates 4.
R1
R2
N
Cl
N
N
EtO2C
EtO2C
H3C
In conclusion, we have developed an efficient iminophosphor-
ane-mediated synthesis of previously unreported ethyl 4-alkyl-
amino-2-arylamino-6-methyl-furo[2,3-d]pyrimidine-5-carboxyl-
ate 5 via aza-Wittig reactions. Bioassay of the compounds indicated
that 4-alkylamino-2-arylamino-6-methyl-furo[2,3-d]pyrimidines
can be used as lead structure for developing novel antitumor drugs.
Further bioassay, optimization and structure–activity relationships
of the title compounds are underway.
NHR1R2
CH3CN
N
H3C
O
O
N
NH
Ar
NH
Ar
4
5
Scheme 2.
The structure of ethyl 4-alkylamino-2-arylamino-6-methyl-
furo[2,3-d]pyrimidine-5-carboxylate 5 was confirmed by their
spectrum data. For example, the 1H NMR spectrum of 5a shows
the signals of –OCH2 at 4.32 ppm as quartets, signals of CH3 at
2.29, 2.57, 1.36 ppm as singlet or triplets. The signals attributable
to the NCH2 are found at 2.47 and 3.57 ppm as broad singlet. The
phenyl and ArN-H signals appeared at 6.96–7.60 ppm as multi-
plets. The IR spectra of 5a revealed C@O absorption bands at
1694 cmÀ1. The MS spectrum of 5a shows strong molecular ion
peak at m/z 395 with 100% abundance. Furthermore a single crystal
of 5b was obtained from a CH2Cl2 solution of 5b.18 X-ray structure
analysis verified again the structure, and showed that all ring
atoms in the furo[2,3-d]pyrimidine moiety are nearly coplanar
and the phenyl ring is twisted with respect to the pyrimidine ring
system by 8.00(7)° (Fig. 2).
Acknowledgments
We gratefully acknowledge financial support of this work by
the Key Science Research Project of the Hubei Provincial Depart-
ment of Education (No. D200724001) and the Science Research
Project of Yunyang Medical College (No. 2008CXG01 and No.
2009QDJ15).
References and notes
1. Zhang, J.; Yang, P. L.; Gray, N. S. Cancer 2009, 9, 28.
2. Joanna, H.; Stefano, S.; John, R. D.; Andrea, M.; Gary, J. Cancer Res. 2009, 69,
1509.
3. Frey, R. R.; Curtin, M. L.; Albert, D. H.; Glaser, K. B. J. Med. Chem. 2008, 51, 3777.
4. Miyazaki, Y.; Maeda, Y.; Sato, H.; Nakano, M.; Mellor, G. W. Bioorg. Med. Chem.
Lett. 2008, 18, 1967.
5. Gundl, R.; Kazemi, R.; Sanam, R.; Muttineni, R.; Sarma, J. A. R. P.; Dayam, R.;
Neamati, N. J. Med. Chem. 2008, 51, 3367.
6. Gibson, C. L.; Huggan, J. K.; Kennedy, A.; Kiefer, L.; Hwan Lee, J.; Suckling, C. J.;
Clements, C.; Harvey, A.; Hunter, W. N.; Tulloch, T. B. Org. Biomol. Chem. 2009, 7,
1829.
The biological activities of 5 were investigated, and the results
showed that these compounds exhibited cytotoxicity against two
lung cancer cell lines A459 and SPC-A-1.19 As indicated in Table
2, compound 5a showed the best inhibition activities against
A459 with IC50 0.8 lM (Table 2).

6190
Y.-G. Hu et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6188–6190
7. (a) Gangjee, A.; Li, W.; Lin, L.; Zeng, Y.; Ihnat, M.; Warnke, L. A.; Green, D. W.;
Cody, V.; Jim Pace, J.; Queener, S. F. Bioorg. Med. Chem. 2009, 17, 7324; (b)
Gangjee, A.; Jain, H. D.; Phan, J.; X., Guo; Queener, S. F.; Kisliuk, R. L. Bioorg. Med.
Chem. 2010, 18, 953.
(s, 1H, N–H); IR (KBr): 3288 (N–H), 1692 (C@O), 1618, 1533, 1417, 1127, 771.
MS (70 eV) m/z (%): 354 (M+, 100), 339 (49), 293 (42), 252 (20), 147 (9), 119
(13), 77 (5). Anal. Calcd for C19H22N4O3 (354.40): C, 64.39; H, 6.26; N, 15.81.
Found: C, 64.24; H, 6.13; N, 15.67. Ethyl 4-(2-hydroxyethylamino)-6-methyl-2-
(phenylamino) furo[2,3-d]pyrimidine-5-carboxylate (5d). White crystals
(yield, 80%). Mp: 129–131 °C. 1H NMR (CDCl3, 600 MHz) d: 1.40 (t, J = 7.2,
3H, CH3), 2.62 (s, 3H, CH3), 3.68 (s, 1H, OH), 3.73 (t, J = 4.8, 2H, CH2), 3.86 (t,
J = 4.8, CH2), 4.34 (t, J = 4.8, 2H, CH2), 6.99–7.61 (m, 6H, Ar-H and ArN-H), 8.53
(s, 1H, N–H); IR (KBr): 3319 (N–H), 1691 (C@O), 1620, 1538, 1445, 1142, 770.
MS (70 eV) m/z (%): 356 (M+, 100), 325 (46), 280 (67), 252 (43), 77 (8). Anal.
Calcd for C18H20N4O4 (356.38): C, 60.66; H, 5.66; N, 15.72. Found: C, 60.47; H,
5.78; N, 15.61. Ethyl 6-methyl-4-morpholino-2-(phenylamino) furo[2,3-
d]pyrimidine-5-carboxylate (5e). White crystals (yield, 90%). Mp: 144–
146 °C. 1H NMR (CDCl3, 600 MHz) d: 1.40 (t, J = 7.2, CH3), 2.61 (s, CH3), 3.54
(t, J = 4.8, CH2), 3.80 (t, J = 4.8, CH2), 4.35 (q, J = 7.2, CH3); 7.00–7.62 (m, 6H, Ar-
H and ArN-H); IR (KBr): 3326 (N–H), 1713 (C@O), 1599, 1531, 1447, 1124, 746.
MS (70 eV) m/z (%): 382 (M+, 100), 337 (28), 324 (41), 222 (14), 118 (8), 77 (8).
8. Alvarez-Sarandés, R.; Peinador, C.; Quintela, J. M. Tetrahedron 2001, 57, 5413.
´
9. Cosslo, F. P.; Alonso, C.; Lecea, B.; Ayerbe, M.; Rubiales, G.; Palacios, F. J. Org.
Chem. 2006, 71, 2839.
10. Molina, P.; Fresneda, P. M.; Delgado, S.; Bleda, J. A. Tetrahedron Lett. 2002, 43,
1005.
11. Liu, M. G.; Hu, Y. G.; Ding, M. W. Tetrahedron 2008, 64, 9052.
12. Hu, Y. G.; Liu, M. G.; Ding, M. W. Helv. Chim. Acta 2008, 91, 862.
13. Huang, N. Y.; Liang, Y. J.; Ding, M. W.; Fu, L. W.; He, H. W. Bioorg. Med. Chem.
Lett. 2009, 19, 831.
14. Hu, Y. G.; Li, G. H.; Ding, M. W. Arkivoc 2008, 151.
15. Preparation of ethyl 3,4-dihydro-6-methyl-4-oxo-2-arylamino-furo[2,3-
d]pyrimidine-5-carboxylate 3a–3b. To
a solution of ammonia hydrate
(ꢀ20 mmol) in EtOH (20 mL) was added carbodiimide (5 mmol)14
2 in
methylene chloride. After stirring for 1–2 h, the solution was concentrated
under reduced pressure and the residue was recrystallized from methylene
chloride/petroleum ether to give ethyl 3,4-dihydro-6-methyl-4-oxo-2-
arylamino-furo[2,3-d]pyrimidine-5-carboxylate 3a–3b. Ethyl 3,4-dihydro-6-
methyl-4-oxo-2-phenylamino-furo[2,3-d]pyrimidine-5-carboxylate (3a). White
crystals (yield, 90%) mp: 281–282 °C. IR (KBr): 3236 (N–H), 1706 (C@O), 1568,
1379, 1048. 1H NMR (400 MHz, DMSO-d6) d: 1.37(t, J = 7.2, 3H, CH3), 2.88 (s,
3H, CH3), 4.34 (q, J = 7.2, 2H, CH2), 5.22 (s, H, NH), 7.33–7.63 (m, 6H, Ar-H and
ArN-H). MS m/z: 313 (M+, 100), 198 (43), 145 (50), 77 (12). Anal. Calcd
for C16H15N3O4 (313.31), C, 61.34; H, 4.83; N, 13.41. Found: C, 61.01; H, 4.58; N,
13.29. Ethyl 2-(m-tolylamino)-3,4-dihydro-6-methyl-4-oxofuro[2,3-d]pyrim-
idine-5-carboxylate (3b). White crystals (yield, 88%), mp: 262–284 °C. IR (KBr):
3337 (N–H), 1700 (C@O), 1545, 1168. 1H NMR (400 MHz, DMSO-d6) d: 1.37
(t, J = 7.2, 3H, CH3), 2.43 (s, 3H, CH3), 2.85 (s, 3H, CH3), 4.34 (q, J = 7.2, 2H, CH2),
5.24 (s, H, NH), 7.06–7.54 (m, 5H, Ar-H and ArN-H). MS m/z: 327 (M+, 100), 203
(37), 160 (29), 91 (46). Anal. Calcd for C17H17N3O4 (327.33): C, 62.38; H, 5.23;
N, 12.84. Found: C, 62..21; H, 5.17; N, 12.75.
Anal. Calcd for C20H22N4O4 (382.41): C, 62.82; H, 5.80; N, 14.65. Found:
C, 62.58; H, 5.79; N, 14.55. Ethyl 2-(m-tolylamino)-4-(butylamino)-6-
methylfuro[2,3-d]pyrimidine-5-carboxylate (5f). White crystals (yield, 84%).
Mp: 123–125 °C. 1H NMR (CDCl3, 600 MHz) d: 0.97 (t, J = 7.2, 3H, CH3), 1.40 (t,
J = 7.2, 3H, CH3), 1.44–1.48 (m, 4H, CH2CH2), 2.34 (s, 3H, CH3), 2.62 (s, 3H, CH3),
3.53–3.56 (m, 2H, CH2), 4.34 (t, J = 7.2, 2H, CH2), 6.78–7.49 (m, 5H, Ar-H and
ArN-H), 8.18 (s, 1H, N–H); 13C NMR (CDCl3, 100 MHz) d: 13.8, 14.1, 14.3, 14.7,
20.3, 21.6, 31.5, 40.7, 61.2, 92.6, 108.8, 115.8, 119.4, 122.4, 128.5, 138.3, 140.1,
156.0, 157.4, 165.5, 166.4. IR (KBr): 3378, 3286 (N–H), 1692 (C@O), 1628, 1532,
1415, 770. MS (70 eV) m/z (%): 382 (M+, 100), 322 (34), 277 (15), 222 (16), 118
(7), 91 (5). Anal. Calcd for C21H26N4O3 (382.46): C, 65.95; H, 6.85; N, 14.65.
Found: C, 65.89; H, 6.79; N, 14.55. Ethyl 2-(m-tolylamino)-6-methyl-4-
morpholino-furo[2,3-d]pyrimidine-5-carboxylate (5g). White crystals (yield,
86%). Mp: 177–179 °C. 1H NMR (CDCl3, 600 MHz) d: 1.36 (t, J = 7.2, 3H, CH3),
2.33 (s, 3H, CH3), 2.59 (s, 3H, CH3), 3.53 (t, J = 4.8, 4H, 2 Â CH2), 3.80 (t, J = 4.8,
4H, 2 Â CH2), 4.34 (q, J = 7.2, 2H, CH2); 6.80–7.42 (m, 5H, Ar-H and ArN-H); 13
C
NMR (CDCl3, 100 MHz) d: 13.9, 14.2, 21.5, 48.9, 61.0, 66.4, 94.0, 109.2, 116.1,
119.6, 122.7, 128.4, 138.2, 139.7, 155.5, 155.9, 159.8, 163.8, 168.3. IR (KBr):
3336 (N–H), 1706 (C@O), 1549, 1531, 1442, 748. MS (70 eV) m/z (%): 396 (M+,
100), 352 (19), 291 (14), 222 (21), 118 (6), 91 (7). Anal. Calcd for C21H24N4O4
(396.44): C, 63.62; H, 6.10; N, 14.13. Found: C, 63.56; H, 5.99; N, 14.04. Ethyl 2-
(m-tolylamino)-6-methyl-4-(4-methylpiperazin-1-yl) furo[2,3-d]pyrimidine-
5-carboxylate (5h). White crystals (yield, 80%). Mp: 148–150 °C. 1H NMR
(CDCl3, 600 MHz) d: 1.36 (t, J = 7.2, 3H, CH3), 2.30 (s, 3H, CH3), 2.33 (s, 3H, CH3),
2.48 (br s, 4H, 2 Â CH2), 2.58 (s, 3H, CH3), 3.59 (br s, 4H, 2 Â CH2), 4.31 (q,
J = 7.2, 2H, CH2), 6.80–7.45 (m, 5H, Ar-H and ArN-H); IR (KBr): 3342 (N–H),
1699 (C@O), 1545, 1528, 740 cmÀ1. MS (70 eV) m/z (%):409 (M+, 100), 365 (24),
260 (35), 118 (14), 91 (5). Anal. Calcd for C22H27N5O3 (409.48): C, 64.53; H,
6.65; N, 17.10. Found: C, 64.50; H, 6.48; N, 17.01. Ethyl 2-(m-tolylamino)-4-
(diethylamino)-6-methylfuro [2,3-d]pyrimidine-5-carboxylate (5i). White
crystals (yield, 82%). Mp: 158–160 °C. 1H NMR (CDCl3, 600 MHz) d: 1.15 (t,
J = 7.2, 6H, 2 Â CH3), 1.36 (t, J = 7.2, 3H, CH3), 2.34 (s, 3H, CH3), 2.55 (s, 3H, CH3),
3.51 (q, J = 7.2, 4H, 2 Â CH2), 4.31 (q, J = 7.2, 2H, CH2), 6.79–7.50 (m, 5H, Ar-H
and ArN-H); 13C NMR (CDCl3, 100 MHz) d: 12.7, 13.3, 14.1, 21.3, 43.0, 60.8,
93.0, 109.7, 115.9, 119.4, 122.2, 128.1, 137.9, 140.0, 153.5, 155.8, 159.0, 164.2,
168.1. IR (KBr): 3364 (N–H), 1702 (C@O), 1545, 1530, 748. MS (70 eV) m/z (%):
382 (M+, 100), 322 (34), 277 (15), 118 (21), 91 (8). Anal. Calcd for C21H26N4O3
(382.46): C, 65.95; H, 6.85; N, 14.65. Found: C, 65.86; H, 6.79; N, 14.58.
Ethyl 2-(m-tolylamino)-4-(isopropylamino)-6-methylfuro[2,3-d]pyrimidine-5-
carboxylate (5j). White crystals (yield, 85%). Mp: 168–170 °C. 1H NMR (CDCl3,
600 MHz) d: 1.32 (d, J = 7.2, 6H, 2 Â CH3), 1.40 (t, J = 7.2, 3H, CH3), 2.34 (s, 3H,
CH3), 2.62 (s, 3H, CH3), 4.35 (t, J = 7.2, 3H, CH and CH2), 6.78–7.54 (m, 5H, Ar-H
and ArN-H), 8.08 (s, 1H, N–H); 13C NMR (CDCl3, 100 MHz) d: 14.1, 14.7, 21.5,
22.5, 42.3, 61.1, 92.5, 108.7, 115.8, 119.4, 122.2, 128.4, 138.2, 140.2, 155.9,
156.6, 157.4, 165.4, 166.4. IR (KBr): 3288 (N–H), 1696 (C@O), 1618, 1532, 1418,
710. MS (70 eV) m/z (%): 368 (M+, 100), 324 (34), 296 (12), 239 (25), 118 (6), 91
(7). Anal. Calcd for C20H24N4O3 (368.43): C, 65.20; H, 6.57; N, 15.21. Found: C,
65.14; H, 6.49; N, 15.08.
16. Preparation of ethyl 4-chloro-6-methyl-2-arylamino-furo[2,3-d]pyrimidine-5-
carboxylates 4: To a mixture of 3 (5 mmol) prepared above and phosphorous
oxychloride (5 mL) were stirred at 80–90 °C for 6–8 h. The solution was
concentrated under reduced pressure to remove excessive phosphorous
oxychloride. The residue was poured into ice water and recrystallized from
methylene chloride/petroleum ether to give ethyl 2-arylamino-4-chloro-6-
methyl-furo[2,3-d]pyrimidine-5-carboxylate 4a–4b. Ethyl 4-chloro-6-methyl-
2-phenylamino-furo [2,3-d] pyrimidine-5-carboxylate (4a). White crystals
(yield, 91%), mp: 165–167 °C. IR (KBr): 3361 (N–H), 1707 (C@O), 1523, 1450,
1165, 754. 1H NMR (400 MHz, CDCl3) d: 1.42 (t, J = 7.2, 3H, CH3), 2.68 (s, 3H,
CH3), 4.41 (q, J = 7.2, 2H, CH2), 7.07–7.63 (m, 6H, Ar-H and ArN-H). MS m/z: 331
(M+, 100), 302 (25), 250 (20), 222 (9), 180 (5), 118 (6), 77 (10). Anal. Calcd for
C16H14ClN3O3 (331.75): C, 57.93; H, 4.25; N, 12.67. Found: C, 57.65; H, 4.00; N,
12.52. Ethyl 4-chloro-6-methyl-2-(m-tolylamino)-furo[2,3-d]pyrimidine-5-
carboxylate (4b). White crystals (yield, 93%), mp: 140–142 °C. IR (KBr): 3361
(N–H), 1702 (C@O), 1530, 1438, 748. 1H NMR (400 MHz, CDCl3) d: 1.40 (t,
J = 7.2, 3H, CH3), 2.30 (s, 3H, CH3), 2.62 (s, 3H, CH3), 4.40 (q, J = 7.2, 2H, CH2),
6.99–7.58 (m, 5H, Ar-H, ArN-H). MS m/z: 345 (M+, 100), 315 (45), 250 (28), 77
(8). Anal. Calcd for C17H16ClN3O3 (345.78): C, 59.05; H, 4.66; N, 12.15. Found: C,
58.96; H, 4.60; N, 12.03.
17. Preparation of ethyl 6-methyl-4-alkylamino-2-arylamino-furo[2,3-d]pyrim-
idine-5-carboxylate 5a–5j. To a solution of 4 (1 mmol) prepared above in
CH3CN (5 mL) was added K2CO3 and primary amines or secondary amines
(3 mmol). The mixture was stirred at 70–80 °C for 6–8 h. The solution was
concentrated under reduced pressure and the residue was recrystallized from
methylene chloride/petroleum ether to give 6-methyl-4-alkylamino-2-
arylamino-furo[2,3-d]pyrimidine-5-carboxylate 5a–5j. Ethyl 6-methyl-4-(4-
methylpiperazin-1-yl)-2-(phenylamino)furo[2,3-d]pyrimidine-5-carboxylate
(5a). White crystals (yield, 81%). Mp: 126–128 °C. 1H NMR (CDCl3, 600 MHz) d:
1.36 (t, J = 7.2, 3H, CH3), 2.29 (s, 3H, CH3), 2.47 (br s, 4H, 2 Â NCH2), 2.57 (s, 3H,
CH3), 3.57 (br s, 4H, 2 Â NCH2), 4.32 (t, J = 7.2, 2H, CH2), 6.96–7.60 (m, 6H, Ar-H
and ArN-H); 13C NMR (CDCl3, 100 MHz) d: 13.8, 14.3, 46.0, 48.1, 54.5, 61.0,
93.9, 109.3, 118.9, 121.8, 128.6, 139.8, 155.1, 155.8, 159.6, 163.9, 168.3. IR
(KBr): 3364 (N–H), 1694 (C@O), 1628, 1531, 1410, 748. MS (70 eV) m/z (%): 395
(M+, 100), 302 (30), 260 (17), 222 (26), 77 (9). Anal. Calcd for C21H25N5O3
(395.45): C, 63.78; H, 6.37; N, 17.71. Found: C, 63.68; H, 6.43; N, 17.66. Ethyl 4-
(butylamino)-6-methyl-2-(phenylamino) furo[2,3-d]pyrimidine-5-carboxylate
(5b). White crystals (yield, 85%). Mp: 144–146 °C. 1H NMR (CDCl3, 600 MHz) d:
0.98 (t, J = 7.2, 3H, CH3), 1.40 (t, J = 7.2, 3H, CH3), 1.45–1.48 (m, 4H, CH2CH2),
2.63 (s, 3H, CH3), 3.53–3.56 (m, 2H, CH2), 4.37 (t, J = 7.2, 2H, CH2), 6.97–7.68 (m,
6H, Ar-H and ArN-H), 8.20 (s, 1H, N–H); IR (KBr): 3378, 3287 (N–H), 1693
(C@O), 1628, 1532, 1415, 1138, 770 cmÀ1. MS (70 eV) m/z (%): 368 (M+, 100),
339 (36), 279 (41), 252 (29), 184 (5), 77 (5). Anal. Calcd for C20H24N4O3
(368.43): C, 65.20; H, 6.57; N, 15.21. Found: C, 65.07; H, 6.43; N, 15.10. Ethyl
4-(iso-propylamino)-6-methyl-2-(phenylamino) furo[2,3-d]pyrimidine-5-car-
boxylate (5c). White crystals (yield, 87%). Mp: 181–182 °C. 1H NMR (CDCl3,
600 MHz) d: 1.32 (d, J = 6.6, 6H, 2 Â CH3), 1.40 (t, J = 7.2, 3H, CH3), 2.63 (s, 3H,
CH3), 4.36 (t, J = 7.2, 3H, CH2 and CH), 6.97–7.67 (m, 6H, Ar-H and ArN-H), 8.10
18. X-ray crystal structure analysis for compound (5b). Formula C20H24N4O3, colorless
crystal. The crystal is of monoclinic, space group P21/n with a = 8.0852(5) Å,
b = 9.3902(6) Å, c = 25.3685(17) Å, b = 97.4950(10)°, V = 1909.6(2) Å3, Z = 4,
Dc = 1.282 g/cm3, F(0 0 0) = 784,
l
= 0.088 mmÀ1, R = 0.0495 and wR = 0.1465
for 4748 observed reflections with I >2r(I0). X-ray structure showed that all
ring atoms in the furo[2,3-d]pyrimidine moiety are nearly coplanar and the
phenyl ring is twisted with respect to the pyrimidine ring system by 8.00(7)°.
Crystallographic data for 5b have been deposited in the Cambridge Crys-
tallographic Data Center as supplementary publication numbers CCDC 778650.
Copies of the data may be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (fax: +44 1223 336033 or e-mail:
deposit@ccdc.cam.ac.uk).
19. Cytotoxic activities were evaluated by using standard MTT assay after
exposure of cells to the tested compounds for 48 h. Results are presented as
mean values of two independent experiments done in quadruplicates.
Coefficients of variation were <10%.