Synthesis of novel benzofuran isoxazolines as protein tyrosine phosphatase 1B inhibitors

Article abstract of DOI:10.1016/j.bmcl.2006.01.062

PTPases are considered to be involved in the etiology of diabetes mellitus and neural diseases, such as Alzheimer's disease and Parkinson's disease. Therefore, PTPase inhibitors should be useful tools to study the role of PTPases in these diseases and other biological phenomena, and which can be developed into chemotherapeutic agents. In the present study, we have synthesized novel benzofuran isoxazolines 13-21 via 1,3-dipolar cycloaddition reaction using karanjin (1) and kanjone (2), isolated from Pongamia pinnata fruits. All the synthesized compounds were evaluated against PTPase enzyme. Compounds 19 and 20 displayed significant inhibitory activity with IC₅₀ values 76 and 81 μM, respectively.

Full text of DOI:10.1016/j.bmcl.2006.01.062

Bioorganic & Medicinal Chemistry Letters 16 (2006) 2139–2143
Synthesis of novel benzofuran isoxazolines as protein
tyrosine phosphatase 1B inhibitorsq
Ghufran Ahmad,a Pushpesh K. Mishra,a Prasoon Gupta,a Prem P. Yadav,a Priti Tiwari,b
Akhilesh K. Tamrakar,b Arvind K. Srivastavab and Rakesh Mauryaa,*
aMedicinal and Process Chemistry Division, Central Drug Research Institute, Lucknow 226 001, India
bBiochemistry Division, Central Drug Research Institute, Lucknow 226 001, India
Received 14 October 2005; revised 4 January 2006; accepted 16 January 2006
Available online 7 February 2006
Abstract—PTPases are considered to be involved in the etiology of diabetes mellitus and neural diseases, such as Alzheimer’s disease
and Parkinson’s disease. Therefore, PTPase inhibitors should be useful tools to study the role of PTPases in these diseases and other
biological phenomena, and which can be developed into chemotherapeutic agents. In the present study, we have synthesized novel
benzofuran isoxazolines 13–21 via 1,3-dipolar cycloaddition reaction using karanjin (1) and kanjone (2), isolated from Pongamia
pinnata fruits. All the synthesized compounds were evaluated against PTPase enzyme. Compounds 19 and 20 displayed significant
inhibitory activity with IC50 values 76 and 81 lM, respectively.
ꢀ 2006 Published by Elsevier Ltd.
Diabetes mellitus is a chronic, incurable disease which
altered the metabolism of lipid, carbohydrates, and pro-
teins in humans and increased the risk of complications
from artery diseases, myocardial infarction, hyperten-
sion, and dyslipidemia, and clinically characterized by
peripheral hyperglycemia. Diabetes can be classified
clinically as insulin-dependent diabetes mellitus (IDDM,
or type-1 diabetes) and non-insulin-dependent diabetes
mellitus (NIDDM, or type-2 diabetes). Type-2 diabetes
is common and found in >90% patient characterized
by either normal/abnormal insulin secretion or function.
Insulin resistance is central to type-2 diabetes and is
known to involve decreased tyrosine phosphorylation
of insulin receptors (IR) despite normal insulin levels.1
between insulin resistance and the level of PTP1B in
muscle and adipose tissue.4 This is further supported
by a variety of cellular and biochemical studies where
PTP1B has been shown to play a role in the dephospho-
rylation of the IR. Therefore, the use of specific PTP1B
inhibitors may enhance insulin action and represents a
novel strategy for the treatment of type-2 diabetes.5
Small molecule PTP1B inhibitors may find an important
clinical role as novel insulin sensitizers in the treatment
of type-2 diabetes.6 Importantly, 2-(oxalylamino) benzo-
ic acid (OBA) I seems to be one of the potent ‘minimal
unit’ phenyl phosphate mimetics identified so far.7 A
synthetic small molecule that selectively inhibits PTP1B
action is, therefore, expected to have a similar beneficial
effect in human and might be developed into therapeutic
agents for treatment of type-2 diabetes and obesity.
Since N-phenyloxamic acid appears to be the potent
non-phosphorus containing PTyr mimetic, a series of
hetrocycle carboxylic acids (II–V) were identified as a
potential N-phenyloxamic acid mimetic with reduced
pKa in the literature8 and shown in Figure 1.
Protein tyrosine phosphatases (PTPases) constitute a di-
verse family of enzymes and are responsible for the
selective dephosphorylation of tyrosine residues.2 Sever-
al PTPs, including PTP1B, LAR, PTPa, and PTPe, are
capable of dephosphorylation the IR, and thereby atten-
uating tyrosine kinase activity. Furthermore, PTP1B has
been implicated in the insulin resistance associated with
diabetes and obesity3 by the finding of correlations
Our phytochemical investigation9 resulted in isolation of
antihyperglycemic compound karanjin (1) from Pong-
amia pinnata fruits. Karanjin displayed around 35%
antihyperglycemic activity in Streptozotocin-induced
diabetic rat at 100 mg/kg dose. Similar observation
was also accorded in alloxan-induced diabetic rats in a
previous investigation.10 Inspired from the biological
Keywords: Protein tyrosine phosphatases 1B inhibitors; Isoxazolines;
Karanjic acid.
q
CDRI Communication No. 6914.
Corresponding author. Tel.: +91 522 2612411 18x4235; fax: +91 522
2623405/2623938/2629504; e-mail: mauryarakesh@rediffmail.com
*
0960-894X/$ - see front matter ꢀ 2006 Published by Elsevier Ltd.
doi:10.1016/j.bmcl.2006.01.062

2140
G. Ahmad et al. / Bioorg. Med. Chem. Lett. 16 (2006) 2139–2143
Br
4-methoxy styrene, 2-vinyl pyridine, 4-vinyl pyridine,
COOH
HO
O
COOH
NH
1-vinyl imidazole, and trans-methoxy cinnamate) in
the presence of chloramine-T13 to produce isoxazolines
(13–21) in good yield. Product 18 proceeds regiospecif-
ically to cis-cycloadduct, it is confirmed by vicinal
spin–spin coupling constant of Ha and Hb protons
(J = 7.0 Hz).14 All the synthesized compounds were
characterized by spectroscopic data and elemental
analysis.15–23
O
N
O
R
II.
I.
HOOC
HOOC
N
O
N
O
O
IV. R=H
V. R=F
O
COOCH3
OH
NH
III.
Vanadate is a non-selective inhibitor of PTPases, and
many of the studies have shown that treatment with
vanadate can normalize blood glucose level in diabet-
ics.24 Taking sodium vanadate as a standard inhibitor,
we have evaluated PTP1B inhibitory activity of benzofu-
ran isoxazolines at 100 lM concentration and their re-
sults are summarized in Table 1. Two of the screened
compounds, that is, 19 and 20 demonstrated PTP1B
inhibitory activity at 100 lM concentration to around
80%. The effect of the test compounds on PTPase was
studied by preincubating the test compound with en-
zyme in the reaction system for 10 min and the residual
protein tyrosine phosphatase activity was determined
according to the method of Goldstein et al.25 The
1.0 ml p-nitrophenylphosphate (pNPP) as the substrate,
assay mixture contained 10 mM PNPP in 50 mM
HEPES buffer (pH 7.0), with 1 mM EDTA and DTT,
respectively. The reaction was stopped by addition of
500 lL of 0.1 N NaOH and the optical density was
determined at 410 nm. Control tubes omitting the
enzyme were always run in parallel to nullify the non-
enzymic reaction and for calculating the concentration
Figure 1. Structures of PTP1B inhibitors.
profile of karanjin and emergence of PTP1B as important
therapeutic target in antidiabetic drug research, we have
designed a novel synthetic strategy to couple the benzof-
uranoid moiety from active compound 1 to known
PTPase inhibitor isoxazoline pharmacophore (Fig. 1).
We have thereby synthesized a new class of benzofuran
isoxazolines (13–21) and studied PTPase inhibition.
The key intermediates of the series 7 and 12 were synthe-
sized using 1 and 2 as starting material isolated from
P. pinnata. The synthesis of 7 and 12 is described in
(Scheme 1). Basic hydrolysis of 1 and 2 with KOH in
aqueous ethanol11 produced karanjic acid (3, 86%) and
kanjonic acid (8, 88%) as a white powder.
Reaction of 3 and 8 with methyl iodide in the presence
of K2CO3 in dry acetone afforded methyl esters 4 and
9 in quantitative yields. Reduction of esters 4 and 9 with
DIBAL afforded a mixture of aldehyde and alcohol.
Therefore, esters 4 and 9 were first converted to alcohols
5 (95%) and 10 (92%) with LiAlH4 and then oxidized
with pyridinium chloro chromate (PCC) to give alde-
hydes 6 and 11 in quantitative yields. Treatment of 6
and 11 with hydroxylamine hydrochloride in the pres-
ence of base afforded oximes 7 (92%) and 12 (90%) as
anti-isomer.12a,b (Scheme 2).
O
OCH3
R2
O
OCH3
(a)
R3
R2 = R3
R1
R1
N
N
O
OH
7. R1=H
12. R1=OCH3
13-21
The oximes 7 and 12 were subjected to oxime-olefin
cycloaddition reaction with substituted olefins (styrene,
Scheme 2. Reagent and condition: (a) chloramine-T, ethanol, reflux.
O
O
O
O
OCH3
OH
(b)
(a)
R1
4. R1=H
COOCH3
R1
R1'
R1
COOH
O
3. R1=H
8. R1=OCH3
1. R1=H, R1'=OCH3
2. R1=OCH3, R1'=H
9. R1=OCH3
(c)
O
O
O
OCH3
OCH3
CHO
OCH3
(e)
(d)
R1
C=N OH
R1
R1
CH2OH
7. R1=H
12. R1=OCH3
6. R1=H
11. R1=OCH3
5. R1=H
10. R1=OCH3
Scheme 1. Reagent and conditions: (a) KOH, aq EtOH, reflux; (b) CH3I, K2CO3, dry acetone, reflux; (c) LiAlH4, dry ether, ꢁC rt; (d) PCC, dry
DCM, stirred at rt; (e) HClÆNH2OH, aq EtOH, 10% NaOH, reflux.

G. Ahmad et al. / Bioorg. Med. Chem. Lett. 16 (2006) 2139–2143
Table 1. PTP1B inhibitory activity of the title compounds 13–21
2141
Product
R1
R2
R3
Inhibition (%)
IC50 (lM)
Ki (lM)
Karanjin
13
—
H
—
H
—
15.8
22.5 2.69
—
227
—
45.0
14
H
H
49.1 7.71
17.4 7.92
14.7 0.42
14.9 2.92
18.5 4.24
80.4 0.14
79.6 3.31
18.4 6.65
56.2
150
—
27.5
—
OCH3
N
15
H
H
16
H
H
—
—
N
N
17
H
H
—
—
N
18
H
CO2CH3
199
76
72.5
30.0
32.0
—
19
OCH3
OCH3
OCH3
—
H
H
H
—
20
81
OCH3
N
21
—
Na3VO4
—
—
—
Results are means+SE of three independent experiments.
2. Elchebly, M.; Paytee, P.; Michaliszyn, E.; Cromlish, W.;
Collins, S.; Loy, A. L.; Normandin, D.; Cheng, A.;
Himms-Hangen, J.; Chan, C. C.; Ramachandran, C.;
Gress, M. J.; Tremblay, M. L.; Kennedy, B. P. Science
1999, 283, 1544.
of p-nitrophenolate ions produced in the reaction mix-
ture. A molar extinction coefficient of 1.78 · 104 was
used to determine the concentration of p-nitrophenolate
produced in the system.
3. Zeil, F. H.; Venkatesan, N.; Davidson, M. B. Diabetes
1988, 37, 885.
4. Ahren, B.; Simonsson, E.; Larsson, H.; Landin-olsson,
M.; Torgeirsson, H.; Jansson, P. A.; Sandquist, M.;
Bavenholm, P.; Efendic, S.; Eriksson, J. W.; Dickinson,
S.; Holmes, D. Diabetes care 2002, 25, 869.
5. Liljebris, C.; Larsen, S. D.; Ogg, D.; Palazuk, B. J.;
Bleasdale, J. E. J. Med. Chem. 2002, 45, 1785.
6. Blaskovich, M. A.; Kim, H.-O. Exp. Opin. Ther. Pat.
2002, 12, 871.
7. Mc Cormack, J. C.; Iversen, L. F.; Andresen, H. S.;
Moller, N. P. H. Curr. Opin. Drug Discov. Dev. 2000, 3,
527.
It is evident from the activity profile (Table 1) that
karanjin is a weak PTP1B inhibitor, whereas its benzo-
furan isoxazolins were found to show good inhibition.
The structure–activity relationship study showed that
substitution at C-5 (phenyl, substituted phenyl, and het-
erocycles) of isoxazoline did not show any significant
improvement in activity except for 14, whereas introduc-
tion of methoxy at C-7 in compounds 19 and 20 remark-
ably enhanced the activity profile as compared to the
reference compound sodium vanadate.
In summary, we have synthesized benzofuran isoxazo-
lines 13–21 starting with naturally occurring furanoflavo-
noids 1 and 2, and tested for PTPase inhibitory activity.
Analogues 19 and 20 displayed promising inhibitory
activity among the synthesized compounds. Further mod-
ification and biological studies are under progress.
8. Liu, G.; Xin, Z.; Pei, Z.; Hajduck, P. J.; Abad-Zapatero,
C.; Hutchins, C. W.; Zhao, H.; Lubben, T. H.; Ballaron,
S. J.; Haasch, D. L.; Kaszubska, W.; Rondinone, C. M.;
Trevillyan, J. M.; Jirousek, M. R. J. Med. Chem. 2003, 46,
4232.
9. Yadav, P. P.; Ahmad, G.; Maurya, R. Phytochemistry
2004, 65, 439.
10. Mandal, B.; Maity, C. R. India Acta Physiol. Pharma. Col.
Blug. 1987, 12, 42.
11. Mukerjee, S. K.; Seshadri, T. R. J. Chem. Soc. C 1955,
2048.
12. (a) Preparation of 4-Methoxy-benzofuran-5-carbaldehyde
oxime (7) as a representative of 7, 12. The aldehyde 6
(5.3 g, 30.11 mmol) was dissolved in ethanol (40 mL),
added hydroxylamine hydrochloride (3.11 g, 45.16 mmol).
The reaction mixture was basified to pH 10 by 10% aq
NaOH and refluxed for 1 h. The mixture was allowed to
cool, extracted with ethyl acetate (100 mL 4·); combined
organic layer was washed with water (100 mL 2·) and
Acknowledgments
Authors are thankful to MOH, DBT, and ICMR, New
Delhi for financial assistance.
References and notes
1. Ross, A. A.; Gulve, E. A.; Wang, M. Chem. Rev. 2004,
104, 1255.

2142
G. Ahmad et al. / Bioorg. Med. Chem. Lett. 16 (2006) 2139–2143
brine (100 mL), dried over anhydrous sodium sulfate,
(C-9), 115.4 (C-5), 114.4 (C-30, C-50), 107.2 (C-3), 105.4
(C-7), 82.8 (C-12), 60.9 (OMe-4), 55.7 (OMe-40), 45.9 (C-
11); FAB MS (+ve): m/z 324 [M+H]+. Elemental analysis:
calcd for C19H17NO4: C, 70.58; H, 5.30; N, 4.33. Found:
C, 70.82; H, 5.11; N, 4.69%.
filtered, and concentrated. The resulting residue was
purified by column chromatography over silica gel (60–
120 mesh size), eluting with hexane and ethyl acetate
(93:07 v/v) to give a white solid. Recrystallization from
methanol yielded 7 (5.46 g, 92% yield), white crystals, mp
132–133 ꢁC; IR (KBr) mmax: 3239, 3155, 3018, 2927, 1588,
17. The procedure for the synthesis of 13 was repeated with 7
(0.52 g, 2.72 mmol), 2-vinyl pyridine (0.42 g, 4.08 mmol),
and chloramine-T (0.91 g, 3.26 mmol). The crude product
was purified by column chromatography over silica gel
(60–120 mesh) using isocratic elution with hexane–ethyl
1479, 1358, 1268, 1221, 1074, 977, 953 cmꢀ1 1H NMR
;
(CDCl3, 200 MHz) d: 8.57 (1H, s, CHNOH) 7.67 (1H, d,
J = 8.6 Hz, H-6), 7.57 (1H, d, J = 2.2 Hz, H-2), 7.21 (1H,
d, J = 8.6 Hz, H-7), 6.94 (1H, d, J = 2.2 Hz, H-3), 4.10
(3H, s, OMe-4); 13C NMR (CDCl3, 50 MHz) d: 158.3 (C-
8), 152.8 (C-4), 147.1 (CHNOH), 144.7 (C-2), 123.2 (C-6),
118.7 (C-9), 117.3 (C-5), 107.3 (C-3), 105.3 (C-7), 61.1
(OMe-4); FAB MS (+ve): m/z 191, 192 [M+H]+ for
C10H9NO3.; (b) 4,7-Dimethoxy-benzofuran-5-carbaldehyde
oxime (12). Preparation from aldehyde 11. (Yield 90%)
white crystals, mp 136–137 ꢁC; IR (KBr) mmax: 3290, 3014,
2949, 2834, 1629, 1608, 1491, 1473, 1355, 1215, 1070, 1007,
31
acetate (85:15), afforded 15 (0.57 g, 71%); viscous; ½aꢁD
ꢀ2.0 (c 0.53, CHCl3); IR (neat) mmax: 2938, 1593, 1472,
1357, 1238, 1059, 971, 889 cmꢀ1; UV (CHCl3) kmax
:
252 nm; 1H NMR (CDCl3, 200 MHz) d: 8.58 (1H, d,
J = 4.6 Hz, H-30), 7.73 (1H, d, J = 8.6 Hz, H-6), 7.70 (1H,
d, J = 4.7 Hz, H-50), 7.60 (1H, d, J = 8.1 Hz, H-7), 7.57
(1H, d, J = 2.2 Hz, H-2), 7.21 (2H, br d, J = 8.9 Hz, H-40,
H-60), 6.92 (1H, d, J = 2.1 Hz, H-3), 5.81 (1H, dd,
J = 10.9, 6.9 Hz, H-12), 4.04 (3H, s, OMe-4), 4.01 (1H,
dd, J = 17.3, 10.9 Hz, H-11a), 3.76 (1H, dd, J = 17.3,
6.9 Hz, H-11b); 13C NMR (CDCl3, 50 MHz) d: 160.1 (C-
10), 158.3 (C-10), 156.4 (C-8), 152.6 (C-4), 149.6 (C-30),
144.8 (C-2), 137.4 (C-50), 125.9 (C-6), 123.1 (C-60), 120.8
(C-40), 119.2 (C-9), 115.4 (C-5), 107.2 (C-3), 105.3 (C-7),
82.7 (C-12), 60.8 (OMe-4), 44.7 (C-11); FAB MS (+ve): m/
977 cmꢀ1 1H NMR (CDCl3, 200 MHz) d: 8.57 (1H, s,
;
CHNOH) 7.59 (1H, d, J = 2.1 Hz, H-2), 7.18 (1H, s, H-6),
6.89 (1H, d, J = 2.1 Hz, H-3), 3.99 (6H, s, 2· OMe); 13C
NMR (CDCl3, 50 MHz) d: 149.3 (C-4), 147.3 (C-8), 147.0
(CHNOH), 145.2 (C-2), 142.5 (C-7), 121.5 (C-5), 117.9 (C-
9), 105.4 (C-3), 103.2 (C-6), 62.1 (OMe-4), 56.6 (OMe-7);
FAB MS (+ve): m/z 221, 222 [M+H]+ for C11H11NO4.
z
294, 295 [M+H]+. Elemental analysis: calcd for
13. Hassner, A.; Lokanath Rai, K. M. Synthesis 1989, 57.
14. Lukevis, E.; Arsenyan, P.; Belyakov, S.; Popelis, J.
J. Organomet. Chem. 1998, 558, 155.
C17H14N2O3: C, 69.38; H, 4.79; N, 9.52. Found: C,
69.64; H, 4.52; N, 9.73%.
18. The procedure for the synthesis of 13 was repeated with 7
(0.51 g, 2.67 mmol), 4-vinyl pyridine (0.42 g, 4.00 mmol),
and chloramine-T (0.90 g, 3.20 mmol), afforded 16 (0.59 g,
15. A solution of oxime 7 (1.52 g, 7.95 mmol), styrene (1.23 g,
11.92 mmol), and chloramine-T (2.68 g, 9.54 mmol) in
absolute alcohol (30 mL) was refluxed with stirring for 9 h.
The reaction mixture was concentrated and the resulting
residue was purified by column chromatography over
silica gel (60–120 mesh size) by isocratic elution with
hexane: acetone (95:05 v/v) to affored 13 (2.19 g, 94%);
31
75%); viscous; ½aꢁD ꢀ3.5 (c 0.33, CHCl3); IR (neat) mmax
:
2952, 1601, 1473, 1418, 1357, 1240, 1160, 1061, 972, 889,
811 cmꢀ1; UV (CHCl3) kmax: 249 nm; H NMR (CDCl3,
1
200 MHz) d: 8.60 (2H, d, J = 5.8 Hz, H-30, H-50), 7.72
(1H, d, J = 8.6 Hz, H-6), 7.59 (1H, d, J = 2.2 Hz, H-2),
7.34 (2H, d, J = 5.9 Hz, H-20, H-60), 7.23 (1H, d,
J = 8.6 Hz, H-7), 6.93 (1H, d, J = 2.1 Hz, H-3), 5.68 (1H,
dd, J = 10.9, 7.3 Hz, H-12), 4.04 (3H, s, OMe-4), 4.03 (1H,
dd, J = 17.5, 10.9 Hz, H-11a), 3.44 (1H, dd, J = 17.2,
7.2 Hz, H-11b); 13C NMR (CDCl3, 50 MHz) d: 158.4 (C-
10), 156.0 (C-8), 152.5 (C-4), 150.0 (C-30, C-50), 145.6 (C-
10), 144.9 (C-2), 126.7 (C-6), 125.9 (C-20), 121.3 (C-60),
119.0 (C-9), 114.7 (C-5), 107.3 (C-3), 105.4 (C-7), 80.9 (C-
12), 60.8 (OMe-4), 46.0 (C-11); FAB MS (+ve): m/z 294,
295 [M+H]+. Elemental analysis: calc. for C17H14N2O3: C,
69.38; H, 4.79; N, 9.52. Found: C, 69.74; H, 4.57; N,
9.77%.
31
white crystals, mp 85–86 ꢁC; ½aꢁD ꢀ3.6 (c 0.27, CHCl3); IR
(KBr) mmax: 2940, 1593, 1468, 1442, 1354, 1244, 1156,
1060, 977, 897, 763, 699, 668 cmꢀ1; UV (CHCl3) kmax: 266
nm; 1H NMR (CDCl3, 200 MHz) d: 7.74 (1H, d,
J = 8.6 Hz, H-6), 7.57 (1H, d, J = 1.4 Hz, H-2), 7.41–
7.31 (5H, m, H-20 to H-60), 7.23 (1H, dd, J = 8.6, 0.6 Hz,
H-7), 6.92 (1H, d, J = 1.4 Hz, H-3), 5.69 (1H, dd, J = 10.6,
8.5 Hz, H-12), 4.04 (3H, s, OMe-4), 3.93 (1H, dd, J = 17.2,
10.7 Hz, H-11a), 3.48 (1H, dd, J = 17.2, 8.4 Hz, H-11b);
13C NMR (CDCl3, 50 MHz) d: 158.2 (C-10), 156.1 (C-8),
152.5 (C-4), 144.8 (C-2), 141.6 (C-10), 129.0 (C-30, C-50),
128.4 (C-40), 126.3 (C-20, C-60), 125.9 (C-6), 119.2 (C-9),
115.5 (C-5), 107.3 (C-3), 105.3 (C-7), 82.9 (C-12), 60.9
(OMe-4), 46.2 (C-11); FAB MS (+ve): m/z 293, 294
[M+H]+. Elemental analysis: calcd for C18H15NO3: C,
73.71; H, 5.15; N, 4.78. Found: C, 73.93; H, 5.03; N,
4.89%.
19. The procedure for the synthesis of 13 was repeated with 7
(0.53 g, 2.77 mmol), 1-vinyl imidazole (0.39 g, 4.15 mmol),
and chloramine-T (0.93 g, 3.32 mmol), afforded 17 (0.48 g,
31
61%); viscous; ½aꢁD ꢀ2.5 (c 0.27, CHCl3); IR (neat) mmax
:
3014, 2955, 1595, 1474, 1423, 1360, 1219, 1082, 1061, 972,
921, 874 cmꢀ1; UV (CHCl3) kmax: 249 nm; 1H NMR
(CDCl3, 200 MHz) d: 8.07 (1H, d, J = 2.1 Hz, H-2), 7.89
(1H, br s, H-20), 7.66 (1H, d, J = 8.6 Hz, H-6), 7.41 (1H, d,
J = 8.6 Hz, H-7), 7.35 (1H, d, J = 2.1 Hz, H-3), 7.23 (1H,
br s, H-40), 6.94 (1H, br s, H-50), 6.78 (1H, dd, J = 9.0,
2.9 Hz, H-12), 4.15 (3H, s, OMe-4), 4.10 (1H, dd, J = 18.5,
16. The procedure for the synthesis of 13 was repeated with 7
(0.51 g, 2.67 mmol), p-methoxy styrene (0.53 g,
4.00 mmol), and chloramine-T (0.90 g, 3.20 mmol), affor-
31
ded 14 (0.71 g, 82%); colorless crystals, mp 97–98 ꢁC; ½aꢁD
ꢀ6.6 (c 0.33, CHCl3); IR (KBr) mmax: 2949, 2837, 1597,
1512, 1465, 1355, 1243, 1169, 1034, 973, 888, 826 cmꢀ1
;
UV (CHCl3) kmax: 242, 252 nm; 1H NMR (CDCl3,
200 MHz) d: 7.74 (1H, d, J = 8.6 Hz, H-6), 7.57 (1H, d,
J = 2.2 Hz, H-2), 7.34 (2H, d, J = 8.7 Hz, H-30, H-50),
7.22 (1H, d, J = 8.6 Hz, H-7), 6.90 (3H, dd, J = 8.7,
2.1 Hz, H-20, H-60, H-3), 5.63 (1H, dd, J = 10.3, 8.930 Hz,
H-12), 4.04 (3H, s, OMe-4), 3.85 (1H, dd, J = 17.2,
10.5 Hz, H-11a), 3.79 (3H, s, OMe-40), 3.46 (1H, dd,
J = 17.2, 8.7 Hz, H-11b); 13C NMR (CDCl3, 50 MHz) d:
159.9 (C-10), 157.8 (C-40), 156.2 (C-8), 152.5 (C-4), 144.8
(C-2), 133.5 (C-10), 127.8 (C-20, C-60), 125.9 (C-6), 119.3
9.1 Hz, H-11a), 3.80 (1H, dd, J = 18.5, 2.9 Hz, H-11b); 13
C
NMR (CDCl3, 50 MHz) d: 157.5 (C-10), 156.3 (C-8),
152.1 (C-4), 145.7 (C-2), 125.2 (C-6, C-20), 118.1 (C-9),
113.2 (C-5), 106.3 (C-3, C-50), 105.5 (C-7, C-40), 84.9 (C-
12), 60.3 (OMe-4), 43.3 (C-11); FAB MS (+ve): m/z 284
[M+H]+. Elemental analysis: calcd for C15H13N3O3: C,
63.60; H, 4.63; N, 14.83. Found: C, 63.83; H, 4.40; N,
14.97%.
20. The procedure for the synthesis of 13 was repeated with 7
(1.25 g, 6.54 mmol), trans-methyl cinnamate (1.58 g,

G. Ahmad et al. / Bioorg. Med. Chem. Lett. 16 (2006) 2139–2143
2143
31
9.81 mmol), and chloramine-T (2.20 g, 7.84 mmol), affor-
31
ded 18 (1.55 g, 67%); colorless crystals, mp 88–90 ꢁC; ½aꢁD
66%); colorless crystals, mp 128–129 ꢁC; ½aꢁD ꢀ4.2 (c 0.28,
CHCl3); IR (KBr) mmax: 3145, 2961, 2915, 2838, 1612, 1514,
1478, 1413, 1354, 1250, 1055, 889, 829 cmꢀ1; UV (CHCl3)
ꢀ4.1 (c 0.31, CHCl3); IR (KBr) mmax: 2953, 1738, 1594,
1469, 1354, 1244, 1165, 1062, 976, 855 cmꢀ1; UV (CHCl3)
k
max: 319 nm; 1H NMR (CDCl3, 200 MHz) d: 7.59 (1H, d,
k
max: 244 nm; 1H NMR (CDCl3, 200 MHz) d: 7.80 (1H, d,
J = 1.9 Hz, H-2), 7.35 (2H, d, J = 8.5 Hz, H-30, H-50), 7.31
(1H, s, H-6), 6.90 (2H, d, J = 8.5 Hz, H-20, H-60), 6.88 (1H,
br s, H-3), 5.65 (1H, dd, J = 10.0, 8.0 Hz, H-12), 3.99 (3H, s,
OMe-4), 3.92 (3H, s, OMe-7), 3.92 (H-11a, merged with
J = 8.6 Hz, H-6), 7.56 (1H, d, J = 2.2 Hz, H-2), 7.37 (5H,
m, H-20 to H-60), 7.22 (1H, d, J = 8.9 Hz, H-7), 6.92 (1H,
d, J = 1.6 Hz, H-3), 5.83 (1H, d, J = 7.0 Hz, H-12), 4.68
(1H, d, J = 7.0 Hz, H-11), 4.0 (3H, s, OMe-4), 3.70 (3H, s,
COOMe); 13C NMR (CDCl3, 50 MHz) d: 170.3
(COOMe), 158.6 (C-10), 153.7 (C-8), 151.9 (C-4), 144.7
(C-2), 140.2 (C-10), 129.2 (C-30, C-50), 128.9 (C-40), 126.2
(C-6), 126.0 (C-20, C-60), 118.1 (C-9), 113.7 (C-5), 107.1
(C-3), 105.6 (C-7), 86.7 (C-12), 64.0 (C-11), 60.2 (OMe-4),
53.0 (COOMe); FAB MS (+ve): m/z 351, 352 [M+H]+.
Elemental analysis: calcd for C20H17NO5: C, 68.37; H,
4.88; N, 3.99. Found: C, 68.58; H, 4.69; N, 4.15%.
methoxy signal), 3.50 (1H, dd, J = 17.4, 8.8 Hz, H-11b); 13
C
NMR (CDCl3, 50 MHz) d: 159.9 (C-40), 156.2 (C-10), 147.I
(C-4), 146.5 (C-8), 145.2 (C-2), 142.2 (C-7), 133.5 (C-10),
128.2 (C-20, C-60), 121.8 (C-9), 116.0 (C-5), 114.5 (C-30, C-
50), 106.2 (C-3), 105.5 (C-6), 83.1 (C-12), 61.6 (OMe-40),
56.7 (OMe-4), 55.7 (OMe-7), 45.7 (C-11); FAB MS (+ve):
m/z 353, 354 [M+H]+. Elemental analysis: calcd for
C20H19NO5: C, 67.98; H, 5.42; N, 3.96; Found: C, 68.11;
H, 5.27; N, 4.16%.
21. The procedure for the synthesis of 13 was repeated with 12
(0.31 g, 1.40 mmol), styrene (0.21 g, 2.10 mmol), and
chloramine-T (0.47 g, 1.68 mmol), afforded 19 (0.34 g,
23. The procedure for the synthesis of 13 was repeated with 12
(0.36 g, 1.62 mmol), 2-vinyl pyridine (0.25 g, 2.43 mmol),
and chloramine-T (0.54 g, 1.94 mmol), afforded 21 (0.31 g,
31
31
75%); white crystals, mp 104–105 ꢁC; ½aꢁD ꢀ2.5 (c 0.23,
59%); viscous; ½aꢁD +5.2 (c 0.34, CHCl3); IR (neat) mmax
:
CHCl3); IR (KBr) mmax: 2940, 2848, 1596, 1574, 1481,
2933, 1622, 1477, 1358, 1220, 1058 cmꢀ1; UV (CHCl3)
k
max: 242, 308 nm; 1H NMR (CDCl3, 200 MHz) d: 8.60
1356, 1222, 1104, 1060, 971, 912, 881 cmꢀ1; UV (CHCl3)
k
max: 280, 314 nm; 1H NMR (CDCl3, 200 MHz) d: 7.60
(1H, d, J = 3.1 Hz, H-30), 7.73 (2H, m, H-50, H-60), 7.61
(1H, br s, H-2), 7.29 (1H, s, H-6), 7.23 (1H, br s, H-40),
6.89 (1H, br s, H-3), 5.83 (1H, br t, J = 7.3 Hz, H-12), 3.99
(3H, s, OMe-4), 3.92 (3H, s, OMe-7), 3.92 (H-11a and H-
11b merged with methoxy signal); 13C NMR (CDCl3,
50 MHz) d: 160.8 (C-10), 156.3 (C-10), 149.7 (C-30), 147.2
(C-4), 146.6 (C-8), 145.2 (C-2), 142.1 (C-7), 137.4 (C-50),
123.2 (C-60), 121.8 (C-9), 115.6 (C-5), 106.2 (C-3), 105.5
(C-6), 83.0 (C-12), 61.6 (OMe-4), 56.7 (OMe-7), 44.4 (C-
11); FAB MS (+ve): m/z 325 [M+H]+. Elemental analysis:
calcd for C18H16N2O4: C, 66.66; H, 4.97; N, 8.64. Found:
C, 66.79; H, 4.82; N, 8.80%.
(1H, d, J = 2.2 Hz, H-2), 7.46–7.34 (5H, m, H-20 to H-60),
7.31 (1H, s, H-6), 6.88 (1H, d, J = 2.2 Hz, H-3), 5.71 (1H,
dd, J = 10.7, 8.5 Hz, H-12), 4.0 (3H, s, OMe-4), 3.93 (1H,
dd, J = 17.3, 10.4 Hz, H-11a), 3.91 (3H, s, OMe-7), 3.51
(1H, dd, J = 17.3, 8.4 Hz, H-11b); 13C NMR (CDCl3,
50 MHz) d: 156.0 (C-10), 147.1 (C-4), 146.5 (C-8), 145.2
(C-2), 142.2 (C-7), 141.6 (C-10), 129.1 (C-30, C-50), 128.5
(C-40), 126.3 (C-20, C-60), 121.8 (C-9), 115.9 (C-5), 106.3
(C-3), 105.5 (C-6), 83.2 (C-12), 61.6 (OMe-4), 56.7 (OMe-
7), 45.9 (C-11); FAB MS (+ve): m/z 323, 324 [M+H]+.
Elemental analysis: calcd for C19H17NO4: C, 70.71; H,
5.30; N, 4.33. Found: C, 70.85; H, 5.21; N, 4.49%.
24. Sekar, N.; Li, J.; Shechter, Y. Crit. Rev. Biochem. Mol.
Biol. 1996, 31, 339.
25. Goldstein, B. J.; Bittner-Kowalezyk, A.; White, M. F.;
Harbeck, M. J. Biol. Chem. 2000, 275, 4283.
22. The procedure for the synthesis of 13 was repeated with 12
(0.34 g, 1.53 mmol), p-methoxy styrene (0.30 g, 2.29 mmol),
and chloramine-T (0.51 g, 1.83 mmol), afforded 20 (0.36 g,