An expedient synthesis of 2-(ω-carboxyalkyl)polyhydroxyisoflavones

Article abstract of DOI:10.1055/s-2000-6351

Derivatives of the isoflavones daidzein and genistein, carrying a carboxyalkyl attachment at C-2 were prepared by cyclization of unprotected 2,4,4'-trihydroxy- or 2,4,4',6-tetrahydroxydeoxybenzoin in the presence of a number of 1,ω-alkanedicarboxylic acid monoester monochlorides, K₂CO₃ and a phase-transfer catalyst in dry acetone. Hydrolysis under basic conditions of the resulting 2-(ω-alkoxycarbonylalkyl)isoflavones gives the title compounds, useful for developing RIA techniques for the analysis of the parent isoflavones.

Full text of DOI:10.1055/s-2000-6351

PAPER
411
An Expedient Synthesis of 2-(w-Carboxyalkyl)polyhydroxyisoflavones
Nawaf Al-Maharik,a Ilpo Mutikainen,b Kristiina Wähälä*,a
aLaboratory of Organic Chemistry, Department of Chemistry, P. O. Box 55, FIN-00014 University of Helsinki, Finland
bLaboratory of Inorganic Chemistry, Department of Chemistry, P. O. Box 55, FIN-00014 University of Helsinki, Finland
Fax +(358)919140357; E-mail: Kristiina.Wahala@helsinki.fi
Received 30 September 1999; revised 15 November 1999
are used, optimally involving 1.5 equivalents of n-
Abstract: Derivatives of the isoflavones daidzein and genistein,
carrying a carboxyalkyl attachment at C-2 were prepared by cy-
clization of unprotected 2,4,4’-trihydroxy- or 2,4,4¢,6-tetrahydroxy-
deoxybenzoin in the presence of a number of 1,w-alkanedicarboxy-
-
Bu4N+Br- (but not n-Bu4N+HSO4 ) and anhydrous K2CO3
in dry acetone at reflux. This produces 2-alkylated isofla-
vone intermediates that we did not characterize but in
lic acid monoester monochlorides, K2CO3 and a phase-transfer cat- which the phenolic hydroxyl groups are presumably acyl-
alyst in dry acetone. Hydrolysis under basic conditions of the
resulting 2-(w-alkoxycarbonylalkyl)isoflavones gives the title com-
pounds, useful for developing RIA techniques for the analysis of the
ated to a certain extent. This, however, does not have any
bearing on the overall synthesis as on aqueous workup no
more than approx. 20% of the phenolic oxygens remain
parent isoflavones.
1
acylated, as judged from the H NMR of the resulting
Key words: genistein, daidzein, isoflavones, immunoassay
crude product. Basic hydrolysis of the 2-(ethoxycarbon-
yl)alkyl ester group also serves to liberate the remaining
phenolic hydroxyls.
The recent appearance of a report1 describing the synthe-
sis of 2-(4-carboxybutyl)genistein (2h) prompted us to
submit our own work, dating from 1997 onwards, on this
and related compounds. These compounds are of interest
for use as haptens for attachment to a carrier protein and
subsequent development of radioimmunoassay (RIA)
techniques for the epidemiological screening of the isofla-
vonoid plant phytoestrogens such as daidzein and
genistein.2-4 The latter compounds appear increasingly
important as natural hormone-dependent cancer protec-
tive agents.5-7
We demonstrate here the synthesis of a number of 2-car-
boxyalkyldaidzeins (2a-f) and -genisteins (2g-j) in unpro-
tected form from the corresponding deoxybenzoins 1
(Scheme). The advantages of our approach are: (1) no pro-
tection of phenolic hydroxyls is required (actually, protec-
tion and deprotection occur in situ); and thus (2)
unprotected phenolic 2-carboxyalkylisoflavones are ob-
tained directly; (3) both daidzein and genistein derivatives
are accessible; and most importantly, (4) long chain phe-
nolic 2-carboxyalkylisoflavones (e.g., 2e,f,i, and j) are
available without problems. Apparently, the previous
synthesis1 is limited to phenolic 2-carboxyalkylgenisteins
where the alkyl chain is (CH2)4 or shorter. Phenolic pro-
tected (CH2)7 and (CH2)8 analogues were also reported1
but presented problems in deprotection, making them un-
suitable for use in immunoassay development as the bio-
logical activity of these compounds is thought to depend
on the free phenolic hydroxy groups.
Although ethyl oxalyl chloride reacts smoothly with
2,4,4’-trihydroxydeoxybenzoin 1a in pyridine8 to give 2-
(ethoxycarbonyl)daidzein 2a, we found that this route
Reagents and conditions: (i) dry acetone, anhyd K2CO3 (6 eq),
n-Bu4N+Br- (1.5 eq), acid chloride (4 or 5 eq), reflux; (ii) KHCO3,
does not work with the higher ester chloride homologues,
for example with ethyl glutaroyl chloride, in keeping with
previous results.1 We now report that the latter reactants
respond very well if slightly modified reaction conditions
MeOH, H2O, benzene, r.t., 24 h; (iii) 10% NaOH, EtOH, r.t., 24 h
Scheme
Synthesis 2000, No. 3, 411–416 ISSN 0039-7881 © Thieme Stuttgart · New York

412
N. Al-Maharik et al.
PAPER
Table 1 13C NMR Chemical Shifts of 2-(w-Carboxyalkyl)isoflavone Estersa 2a–j
Compound
Solventb
2a
A
2b
A
2c
B
2d
B
2e
B
2f
B
2g
B
2h
B
2i
B
2j
B
C-2
C-3
C-4
C-4a
C-5
C-6
C-7
C-8
C-8a
C-1'
149.8
124.4
175.4
115.8
127.3
115.8
163.3
102.0
156.7
121.5
131.0
114.6
157.4
–
–
–
–
–
–
–
–
162.9
122.0
175.0
115.3
126.9
115.3
162.3
101.7
156.8
123.0
131.3
114.7
156.6
27.3
30.5
–
165.4
123.9
176.4
117.6
128.3
115.2
163.0
103.0
158.5
125.3
132.6
115.8
157.7
32.2
23.3
33.8
–
165.9
123.5
176.4
117.3
128.1
115.2
162.9
102.9
158.3
125.1
132.5
115.7
157.5
32.5
27.3
25.0
33.7
–
166.0
123.5
176.3
117.4
128.2
115.1
162.9
102.9
158.4
125.4
132.5
115.7
157.6
32.8
29.4
27.8
25.4
29.3
34.2
–
166.2
123.5
176.3
117.4
128.2
115.1
163.0
101.9
158.4
125.4
132.5
115.7
157.6
32.8
29.8
29.6
27.9
25.6
29.6
29.7
34.3
174.0
–
166.7
122.3
181.9
104.9
163.1
99.2
164.5
94.1
158.5
123.6
132.5
115.7
157.7
32.1
23.1
33.6
–
167.4
122.0
181.8
104.8
163.4
99.2
164.5
94.0
158.5
123.7
132.6
115.8
157.7
32.5
27.3
25.0
33.8
–
167.6
122.0
181.9
104.8
163.3
99.2
164.5
94.0
158.4
123.7
132.5
115.7
157.7
32.6
29.2
27.6
25.3
29.1
34.1
–
167.8
122.1
182.0
104.9
163.4
99.3
164.6
94.1
158.5
123.8
132.5
115.8
157.8
32.7
29.8
29.66
27.8
C-2',C-6'
C-3',C-5'
C-4'
C-1"
C-2"
C-3"
C-4"
C-5"
C-6"
C-7"
C-8"
C=O
CH2
–
–
–
–
–
–
–
–
–
–
–
–
25.6
–
–
–
–
–
–
29.66
29.75
34.3
174.0
–
–
–
–
161.3
61.9
13.3
171.8
60.1
14.0
173.0
60.6
14.5
173.6
–
51.5
173.9
–
51.5
172.7
60.6
14.4
173.6
–
51.5
173.8
–
51.3
CH3
51.5
51.4
a Where the multiplicities are the same and chemical shifts are close, assignments could be interchanged.
b Solvents: A = DMSO-d6; B = acetone-d6.
As seen from the Scheme, we have a generally applicable noassay development work. We must nevertheless
synthesis of phenolic unprotected 2-(w-carboxy- acknowledge that an early member of the series, namely
alkyl)isoflavones that should be amenable for the immu- the 2-(ethoxycarbonyl)methyl homologue, is not accessi-
Table 2 13C NMR Chemical Shifts of 2-(w-Carboxyalkyl)isoflavonesa 3a–j
Compound 3a
3b
A
3c
A
3d
A
3e
B
3f
B
3g
B
3h
B
3i
B
3j
B
Solventb
A
C-2
C-3
C-4
C-4a
C-5
C-6
C-7
C-8
C-8a
C-1’
C-2’,C-6’
C-3’,C-5’
C-4’
C-1"
C-2"
C-3"
C-4"
C-5"
C-6"
C-7"
C-8"
C=O
151.4
122.9
175.5
115.7
127.2
115.6
162.6
102.0
157.1
121.7
131.0
114.6
156.6
–
–
–
–
–
–
–
–
163.7
122.1
175.4
115.6
127.2
114.8
162.5
102.0
157.1
123.3
131.6
114.8
156.9
27.6
30.8
–
164.2
122.1
175.1
115.3
126.8
114.6
162.3
101.8
156.8
123.2
131.3
114.7
156.5
31.1
22.1
32.7
–
164.6
122.0
175.0
115.3
126.8
114.5
162.1
101.7
156.8
123.2
131.3
114.7
156.4
31.3
26.1
23.8
33.0
–
166.1
123.5
176.3
117.4
128.2
115.1
162.9
102.9
158.4
125.4
132.6
115.7
157.6
32.8
166.3
123.4
176.3
117.4
128.1
115.1
162.9
102.9
158.4
125.3
132.5
115.6
157.5
32.8
29.7
27.9
25.6
25.6
27.9
29.6
34.1
174.6
167.1
122.5
182.2
105.1
163.6
99.4
164.8
94.2
158.7
123.8
132.7
116.0
158.0
32.2
23.2
33.3
–
167.5
122.2
182.0
104.9
163.5
99.3
164.6
94.1
158.6
123.8
132.6
115.9
157.8
32.5
27.4
25.0
33.6
–
167.8
122.1
182.0
104.9
163.4
99.3
164.6
94.1
158.6
123.8
132.6
115.8
157.8
32.7
29.4
27.8
25.4
29.3
34.0
–
167.9
122.1
182.0
104.9
163.5
99.3
164.6
94.1
158.6
123.8
132.6
115.8
157.8
32.7
29.7
27.8
25.6
25.6
29.4
27.9
25.5
29.4
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
34.1
–
–
–
27.8
29.6
34.1
174.6
–
–
–
–
163.1
173.3
173.5
173.9
174.5
174.0
174.2
174.5
a Where the multiplicities are the same and chemical shifts are close, assignments could be interchanged.
b Solvents: A = DMSO-d6; B = acetone-d6.
Synthesis 2000, No. 3, 411–416 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
An Expedient Synthesis of 2-(w-Carboxyalkyl)polyhydroxyisoflavones
413
NMR spectra were recorded on a Varian GEMINI-2000 or a Varian
Inova 300 WB spectrometer. TMS was used as an internal standard
and chemical shifts are given in d (ppm) and J values in Hz. Mps
were determined in open capillary tubes with an Electrothermal ap-
paratus and are uncorrected. Mass spectra were obtained with a
JEOL JMS SX102 mass spectrometer operating at 70 eV and the
samples were introduced by a direct inlet probe. TLC was conduct-
ed on Merck silica gel 60 F254 plates. All compounds were homog-
enous on TLC. Combustion analyses were performed at the
Analytische Laboratorien, Lindlar, Germany.
ble applying our general synthetic procedure with ethyl
malonoyl chloride. On the other hand, we feel confident in
predicting that a “spacer” unit of just one CH2 group
would not be sufficient for a good immunological re-
sponse. The structures of the compounds were confirmed
by low and high resolution MS and 2D NMR techniques
(GHSQCTOCSY and GHMBC).
2a-j; General Procedure
The acid ester chloride (8 mmol for 1a, or 10 mmol for 1b) was add-
ed dropwise to a stirred suspension of a deoxybenzoin 1 (2 mmol),
anhyd K2CO3 (1.66 g, 12 mmol) and tetra-n-butylammonium bro-
mide (0.97 g, 3 mmol) in anhyd acetone (40 mL) under Ar at r.t. The
mixture was stirred for 2 h at r.t. After heating for several hours
(Scheme) at 75 °C (oil bath temperature), the mixture was allowed
to cool to r.t., the acetone solution was filtered, and the remaining
solid was dissolved in H2O (100 mL). The aqueous solution was
neutralized with 2 N HCl and extracted with EtOAc (2 x 60 mL).
The EtOAc extracts were washed with H2O (100 mL), dried
(MgSO4), and combined with the above acetone solution. The re-
sulting mixture was evaporated to yield an orange oil, which was
dissolved in MeOH (100 mL), 0.5 M aq KHCO3 (20 mL), and ben-
zene (20 mL). The solution was stirred for 24 h at r.t. The organic
solvents were evaporated under reduced pressure, H2O (50 mL) was
added, the solution neutralized with dilute HCl, and extracted with
EtOAc (50 mL). The EtOAc solution was washed with H2O (20
mL), dried (MgSO4), filtered, and concentrated to give an orange
oil. Purification by flash chromatography (gradient elution with
CH2Cl2 to CH2Cl2/acetone, 8:2) gave a viscous oil, recrystallised
from benzene/Et2O (3:7) to afford the desired isoflavones 2a-j (see
Scheme, and Table 1).
Figure Molecular structure of 2g. Thermal ellipsoids at 30% proba-
bility level.
2-Ethoxycarbonyl-7,4’-dihydroxyisoflavone (2a)
Light yellow solid; yield: 0.42 g (63%); mp 194-195 °C (Lit.8 mp
194-195 °C).
1H NMR (300 MHz, DMSO-d6): d = 0.98 (t, 3H, J = 7.2 Hz,
CO2CH2CH3), 4.11 (q, 2H, J = 7.2 Hz, CO2CH2CH3), 6.80 (d, 2H,
J = 8.4 Hz, H-3', H-5'), 6.90 (d, 1H, J = 2.2 Hz, H-8), 6.98 (dd, 1H,
J = 8.8, 2.2 Hz, H-6), 7.05 (d, 2H, J = 8.4 Hz, H-2', H-6'), 7.94 (d,
1H, J = 8.8 Hz, H-5), 9.68 (s, 1H, 4'-OH), 11.16 (s, 1H, 7-OH).
MS: m/z (%) = 326 (M+, 22), 297 (10), 279 (3), 244 (15), 149 (9),
137 (100), 107 (9). HRMS: m/z calc for C18H14O6 (M+) 326.0791.
Found: 326.0787.
Table 3 Selected Bond Lengths [A] and Angles [deg] for
C(21)H(20)O(7)
O(1)-C(2)
O(1)-C(8A)
C(4)-O(2)
C(5)-O(3)
C(4’)-O(5)
C(4’’)-O(6)
C(4’’)-O(7)
O(7)-C(5’’)
1.361(3)
1.368(3)
1.267(3)
1.352(4)
1.368(3)
1.216(8)
1.316(11)
1.503(17)
2-[2-(Ethoxycarbonyl)ethyl]-7,4’-dihydroxyisoflavone (2b)
White solid; yield: 0.48 g (67%); mp 177-178 °C.
1H NMR (200 MHz, DMSO-d6): d = 1.14 (t, 3H, J = 7.2 Hz,
CO2CH2CH3), 2.69 (t, 2H, J = 7.0 Hz, H-2"), 2.78 (t, 2H, J = 7.0
Hz, H-1"), 4.04 (q, 2H, J = 7.2 Hz, CO2CH2CH3), 6.80 (d, 1H,
J = 2.2 Hz, H-8), 6.80 (d, 2H, J = 8.6 Hz, H-3', H-5'), 6.89 (dd, 1H,
J = 8.8, 2.2 Hz, H-6), 7.04 (d, 2H, J = 8.6 Hz, H-2', H-6'), 7.85 (d,
1H, J = 8.8 Hz, H-5).
MS: m/z (%) = 354 (M+, 27), 340 (30), 325 (7), 309 (20), 281 (100),
251 (3), 137 (9).
HRMS: m/z calc for C20H18O6 (M+) 354.1104. Found: 354.1088.
C(2)-O(1)-C(8A)
C(3)-C(2)-O(1)
O(1)-C(2)-C(1’’)
O(2)-C(4)-C(4A)
O(2)-C(4)-C(3)
O(3)-C(5)-C(6)
O(4)-C(7)-C(8)
O(4)-C(7)-C(6)
O(1)-C(8A)-C(8)
O(1)-C(8A)-C(4A)
O(6)-C(4’’)-O(7)
O(6)-C(4’’)-C(3’’)
O(7)-C(4’’)-C(3’’)
121.1(2)
122.4(3)
110.5(2)
120.9(3)
121.6(3)
119.2(3)
118.4(3)
120.4(3)
117.4(3)
120.1(2)
122.8(7)
128.8(6)
108.4(6)
2-[3-(Ethoxycarbonyl)propyl]-7,4’-dihydroxyisoflavone (2c)
White solid; yield: 0.53 g (71%); mp 159-160 °C.
1H NMR (300 MHz, acetone-d6): d = 1.15 (t, 3H, J = 7.1 Hz,
CO2CH2CH3), 2.03 (quintet, 2H, J = 7.2 Hz, H-2"), 2.33 (t, 2H,
J = 7.4 Hz, H-3"), 2.64 (t, 2H, J = 7.2 Hz, H-1"), 4.00 (q, 2H,
C(4’’)-O(7)-C(5’’)
C(6’’)-C(5’’)-O(7)
117.5(7)
109.6(11)
Synthesis 2000, No. 3, 411–416 ISSN 0039-7881 © Thieme Stuttgart · New York

414
N. Al-Maharik et al.
PAPER
J = 7.1 Hz, CO2CH2CH3), 6.87 (d, 2H, J = 8.8 Hz, H-3’, H-5’), 6.90
(d, 1H, J = 2.2 Hz, H-8), 6.94 (dd, 1H, J = 8.8, 2.2 Hz, H-6), 7.11
(d, 2H, J = 8.8 Hz, H-2’, H-6’), 7.96 (d, 1H, J = 8.8 Hz, H-5).
MS: m/z (%) = 368 (M+, 54), 339 (3), 323 (16), 295 (12), 281 (100),
6), 6.41 (d, 1H, J = 2.2 Hz, H-8), 6.91 (d, 2H, J = 8.8 Hz, H-3', H-
5'), 7.14 (d, 2H, J = 8.8 Hz, H-2', H-6').
MS: m/z (%) = 384 (M+, 59), 353 (8), 311 (9), 297 (100), 283 (7),
153 (29), 131 (7).
268 (15), 251 (5), 144 (3), 137 (11).
HRMS: m/z calc for C21H20O6 (M+) 368.1260. Found: 368.1276.
HRMS: m/z calc for C21H20O7 (M+) 384.1209. Found: 384.1217.
5,7,4’-Trihydroxy-2-[6-(methoxycarbonyl)hexyl]isoflavone (2i)
7,4’-Dihydroxy-2-[4-(methoxycarbonyl)butyl]isoflavone (2d)
White solid; yield: 0.48 g (64%); mp 168-169 °C.
White solid; yield: 0.47 g (56%); mp 124-125 °C.
1H NMR (200 MHz, acetone-d6): d = 1.25-1.30 (m, 4H, H-3", H-
4"), 1.54 (quintet, 2H, J = 7.1 Hz, H-5"), 1.70 (quintet, 2H, J = 7.8
Hz, H-2"), 2.25 (t, 2H, J = 7.3 Hz, H-6"), 2.59 (t, 2H, J = 7.7 Hz, H-
1"), 3.60 (s, 3H, CO2CH3), 6.24 (d, 1H, J = 2.2 Hz, H-6), 6.41 (d,
1H, J = 2.2 Hz, H-8), 6.91 (d, 2H, J = 8.4 Hz, H-3', H-5'), 7.14 (d,
2H, J = 8.4 Hz, H-2', H-6').
1H NMR (200 MHz, acetone-d6): d = 1.54-1.79 (m, 4H, H-2", H-
3"), 2.26 (t, 2H, J = 7.2 Hz, H-4"), 2.61 (t, 2H, J = 7.3 Hz, H-1"),
3.57 (s, 3H, CO2CH3), 6.89 (d, 2H, J = 8.8 Hz, H-3', H-5'), 6.89 (d,
1H, J = 2.2 Hz, H-8), 6.95 (dd, 1H, J = 8.8, 2.2 Hz, H-6), 7.12 (d,
2H, J = 8.8 Hz, H-2', H-6'), 7.97 (d, 1H, J = 8.8 Hz, H-5).
MS: m/z (%) = 368 (M+, 56), 337 (3), 323 (14), 295 (13), 281 (100),
MS: m/z (%) = 412 (M+, 77), 381 (11), 353 (4), 339 (6), 311 (9), 297
268 (13), 251 (3), 137 (12).
(100), 283 (14), 153 (13), 131 (5).
HRMS: m/z calc for C21H20O6 (M+) 368.1259. Found: 368.1260.
HRMS: m/z calc for C23H24O7 (M+) 412.1522. Found: 412.1526.
7,4’-Dihydroxy-2-[6-(methoxycarbonyl)hexyl]isoflavone (2e)
5,7,4’-Trihydroxy-2-[8-(methoxycarbonyl)octyl]isoflavone (2j)
White solid; yield: 0.42 g (52%); mp 175-176 °C.
White solid; yield: 0.51 g (60%); mp 138-139 °C.
1H NMR (200 MHz, acetone-d6): d = 1.23-1.34 (m, 4H, H-3", H-
4"), 1.54 (quintet, 2H, J = 7.2 Hz, H-5"), 1.71 (quintet, 2H, J = 7.3
Hz, H-2"), 2.25 (t, 2H, J = 7.3 Hz, H-6"), 2.58 (t, 2H, J = 7.7 Hz, H-
1"), 3.59 (s, 3H, CO2CH3), 6.89 (d, 2H, J = 8.8 Hz, H-3', H-5'), 6.90
(d, 1H, J = 2.2 Hz, H-8), 6.95 (dd, 1H, J = 8.8, 2.2 Hz, H-6), 7.11
(d, 2H, J = 8.8 Hz, H-2', H-6'), 7.96 (d, 1H, J = 8.8 Hz, H-5).
1H NMR (200 MHz, acetone-d6): d = 1.23 (br, 8H, H-3", H-4", H-
5", H-6"), 1.53 (quintet, 2H, J = 7.2 Hz, H-7"), 1.68 (quintet, 2H,
J = 7.4 Hz, H-2"), 2.25 (t, 2H, J = 7.3 Hz, H-8"), 2.57 (t, 2H, J = 7.5
Hz, H-1"), 3.59 (s, 3H, CO2CH3), 6.22 (d, 1H, J = 2.2 Hz, H-6), 6.39
(d, 1H, J = 2.2 Hz, H-8), 6.90 (d, 2H, J = 8.8 Hz, H-3', H-5'), 7.12
(d, 2H, J = 8.8 Hz, H-2', H-6'),
MS: m/z (%) = 396 (M+, 48), 365 (10), 337 (4), 323 (7), 295 (15),
MS: m/z (%) = 440 (M+, 100), 409 (16), 381 (6), 367 (9), 353 (6),
281 (100), 268 (19), 252 (14), 137 (10).
339 (7), 311 (10), 297 (82), 284 (26), 153 (17), 131 (7).
HRMS: m/z calc for C23H24O6 (M+) 396.1573. Found: 396.1565.
HRMS: m/z calc for C25H28O7 (M+) 440.1835. Found: 440.1817.
7,4’-Dihydroxy-2-[8-(methoxycarbonyl)octyl]isoflavone (2f)
White solid; yield: 0.39 g (45%); mp 142-143 °C.
Hydrolysis of 2-(w-Alkoxycarbonylalkyl)isoflavones 2a-j; Gen-
eral Procedure
10% aq NaOH (10 mL) was added to a solution of the isoflavone
2a-j (100 mg) in EtOH (10 mL) and the mixture stirred for 24 h at
r.t. The EtOH was removed under reduced pressure, H2O (10 mL)
was added to the yellow solution, which was then acidified at 0 °C
to pH 4 with 37% HCl, and kept overnight in the refrigerator. The
precipitate was filtered off and dried to provide the desired acid 3a-
j in an almost quantitative yield (Table 2).
1H NMR (200 MHz, acetone-d6): d = 1.23-1.34 (br, 8H, H-3", H-
4", H-5", H-6"), 1.53 (quintet, 2H, J = 7.3 Hz, H-7"), 1.68 (quintet,
2H, J = 7.4 Hz, H-2"), 2.25 (t, 2H, J = 7.3 Hz, H-8"), 2.56 (t, 2H,
J = 7.5 Hz, H-1"), 3.58 (s, 3H, CO2CH3), 6.87 (d, 2H, J = 8.8 Hz, H-
3', H-5'), 6.87 (d, 1H, J = 2.2 Hz, H-8), 6.93 (dd, 1H, J = 8.8, 2.2 Hz,
H-6), 7.09 (d, 2H, J = 8.8 Hz, H-2', H-6'), 7.94 (d, 1H, J = 8.8 Hz,
H-5).
MS: m/z (%) = 424 (M+, 48), 393 (7), 365 (3), 351 (6), 337 (4), 323
(4), 295 (10), 281 (100), 268 (26), 137 (9).
HRMS: m/z calc for C25H28O6 (M+) 424.1886. Found: 424.1883.
2-Carboxy-7,4’-dihydroxyisoflavone (3a)
White solid; yield: 89 mg (97%); mp 288-289 °C from EtOAc-ac-
etone (Lit.8 mp 290 °C).
1H NMR (200 MHz, DMSO-d6): d = 6.76 (d, 2H, J = 8.4 Hz, H-3',
H-5'), 6.89 (d, 1H, J = 2.2 Hz, H-8), 6.96 (dd, 1H, J = 8.8, 2.2 Hz,
H-6), 7.06 (d, 2H, J = 8.4 Hz, H-2', H-6'), 7.92 (d, 1H, J = 8.8 Hz,
H-5), 9.56 (s, 1H, 4'-OH), 10.89 (s, 1H, 7-OH).
MS: m/z (%) = 298 (M+, 85), 281 (9), 268 (16), 254 (100), 240 (5),
217 (6), 149 (3), 137 (65), 118 (20), 108 (11).
2-[3-(Ethoxycarbonyl)propyl]-5,7,4’-trihydroxyisoflavone (2g)
White solid; yield: 0.37 g (50%); mp 179 °C.
1H NMR (200 MHz, acetone-d6): d = 1.16 (t, 3H, J = 7.2 Hz,
CO2CH2CH3), 1.99 (quintet, 2H, J = 7.4 Hz, H-2"), 2.34 (t, 2H,
J = 7.4 Hz, H-3"), 2.65 (t, 2H, J = 7.4 Hz, H-1"), 4.02 (q, 2H,
J = 7.2 Hz, CO2CH2CH3), 6.24 (d, 1H, J = 2.2 Hz, H-6), 6.41 (d,
1H, J = 2.2 Hz, H-8), 6.91 (d, J = 8.8 Hz, 2H, H-3', H-5'), 7.15 (d,
2H, J = 8.8 Hz, H-2', H-6').
MS: m/z (%) = 384 (M+, 53), 355 (5), 339 (11), 311 (5), 297 (100),
283 (12), 253 (4), 153 (13), 131 (7).
HRMS: m/z calc for C21H20O7 (M+) 384.1210. Found: 384.1205.
HRMS: m/z, calc for C16H10O6 (M+) 298.0478. Found: 298.0484.
2-(2-Carboxyethyl)-7,4’-dihydroxyisoflavone (3b)
White solid; yield: 87 mg (95%); mp 274 °C from EtOAc-acetone.
1H NMR (300 MHz, DMSO-d6): d = 2.58 (t, 2H, J = 7.4 Hz, H-2"),
2.75 (t, 2H, J = 7.3 Hz, H-1"), 6.79 (d, 2H, J = 8.6 Hz, H-3', H-5'),
6.80 (d, 1H, J = 2.2 Hz, H-8), 6.88 (dd, 1H, J = 8.8, 2.2 Hz, H-6),
7.04 (d, 2H, J = 8.6 Hz, H-2', H-6'), 7.84 (d, 1H, J = 8.8 Hz, H-5),
9.49 (s, 1H, 4'-OH), 10.81 (s, 1H, 7-OH), 12.2 (s, 1H, CO2H).
5,7,4’-Trihydroxy-2-[4-(methoxycarbonyl)butyl]isoflavone (2h)
White solid; yield: 0.36 g (49%); mp 186 °C.
1H NMR (200 MHz, acetone-d6): d = 1.52-1.69 (m, 2H, H-3"),
1.70-1.81 (m, 2H, H-2"), 2.26 (t, 2H, J = 7.2 Hz, H-4"), 2.61 (t, 2H,
J = 7.3 Hz, H-1"), 3.59 (s, 3H, CO2CH3), 6.25 (d, 1H, J = 2.2 Hz, H-
MS: m/z 326 (M+, 52), 281 (100), 266 (5), 252 (4), 137 (13), 115 (4).
HRMS: m/z, calc for C18H14O6 (M+) 326.0790. Found: 326.0788.
Synthesis 2000, No. 3, 411–416 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
An Expedient Synthesis of 2-(w-Carboxyalkyl)polyhydroxyisoflavones
415
Anal. Calc for C18H14O6: C, 66.26, H, 4.32. Found: C, 65.79, H,
4.70.
2-(3-Carboxypropyl)-5,7,4’-trihydroxyisoflavone (3g)
White solid; yield: 87 mg (94%); mp 218-219 °C from EtOAc-ac-
etone.
1H NMR (300 MHz, acetone-d6): d = 1.99 (quintet, 2H, J = 7.4 Hz,
H-2"), 2.35 (t, 2H, J = 7.3 Hz, H-3"), 2.67 (t, 2H, J = 7.5 Hz, H-1"),
6.24 (d, 1H, J = 2.1 Hz, H-6), 6.42 (d, 1H, J = 2.1 Hz, H-8), 6.90 (d,
2H, J = 8.6 Hz, H-3', H-5'), 7.15 (d, 2H, J = 8.6 Hz, H-2', H-6').
MS: m/z (%) = 356 (M+, 92), 327 (5), 297 (15), 153 (17), 131 (10),
115 (6).
2-(3-Carboxypropyl)-7,4’-dihydroxyisoflavone (3c)
White solid; yield: 86 mg (93%); mp 210 °C from EtOAc/acetone.
1H NMR (300 MHz, DMSO-d6): d = 1.85 (quintet, 2H, J = 7.2 Hz,
H-2"), 2.21 (t, 2H, J = 7.2 Hz, H-3"), 2.54 (t, 2H, J = 7.2 Hz, H-1"),
6.81 (d, 2H, J = 8.4 Hz, H-3', H-5'), 6.88 (d, 1H, J = 2.1 Hz, H-8),
6.92 (dd, 1H, J = 8.8, 2.1 Hz, H-6), 7.01 (d, 2H, J = 8.4 Hz, H-2', H-
6'), 7.86 (d, 1H, J = 8.8 Hz, H-5), 9.52 (s, 1H, 4'-OH), 10.85 (s, 1H,
7-OH), 12.08 (s, 1H, COOH).
HRMS: m/z calc for C19H16O7 (M+) 356.0896. Found 356.0901.
Anal. Calc for C19H16O7: C, 64.04, H, 4.53. Found: C, 63.72, H,
4.49.
MS: m/z (%) = 340 (M+, 52), 295 (14), 281 (100), 268 (13), 254 (7),
237 (3), 144 (3), 137 (14), 115 (3).
HRMS: m/z calc for C19H16O6 (M+) 340.0947. Found: 340.0939.
2-(4-Carboxybutyl)-5,7,4’-trihydroxyisoflavone (3h)
White solid; yield: 91%, mp 229-230 °C from EtOAc-acetone
(Lit.1 mp 230-232 °C).
Anal. Calc for C19H16O6: C, 67.05, H, 4.74. Found: C, 66.68, H,
5.06.
1H NMR (300 MHz, acetone-d6): d = 1.68 (quintet, 2H, J = 7.4 Hz,
H-3"), 1.77 (quintet, 2H, J = 7.2 Hz, H-2"), 2.23 (t, 2H, J = 7.1 Hz,
H-4"), 2.62 (t, 2H, J = 7.3 Hz, H-1"), 6.23 (d, 1H, J = 2.1 Hz, H-6),
6.41 (d, 1H, J = 2.1 Hz, H-8), 6.92 (d, 2H, J = 8.6 Hz, H-3', H-5'),
7.16 (d, 2H, J = 8.6 Hz, H-2', H-6').
MS: m/z (%) = 370 (M+, 77), 311 (14), 297 (100), 283 (9), 153 (11),
141 (6), 131 (5).
2-(4-Carboxybutyl)-7,4’-dihydroxyisoflavone (3d)
White solid; yield: 91 mg (95%); mp 230 °C from EtOAc-acetone.
1H NMR (200 MHz, DMSO-d6): d = 1.44 (quintet, 2H, J = 7.4 Hz,
H-3"), 1.61 (quintet, 2H, J = 7.4 Hz, H-2"), 2.14 (t, 2H, J = 7.0 Hz,
H-4"), 2.50 (t, 2H, J = 7.0 Hz, H-1"), 6.80 (d, 2H, J = 8.4 Hz, H-3',
H-5'), 6.81 (d, 1H, J = 2.2 Hz, H-8), 6.89 (dd, 1H, J = 8.8, 2.2 Hz,
H-6), 7.01 (d, 2H, J = 8.4 Hz, H-2', H-6'), 7.86 (d, 1H, J = 8.8 Hz,
H-5), 9.49 (s, 1H, 4'-OH), 10.72 (s, 1H, 7-OH), 12.01 (s, 1H,
COOH).
MS: m/z (%) = 354 (M+, 57), 295 (23), 281 (100), 268 (17), 252
(14), 235 (6), 152 (7), 137 (14), 115 (4), 94 (8), 77 (14).
HRMS: m/z calc for C20H18O6 (M+) 354.1103. Found: 354.1108.
HRMS: m/z calc for C20H18O7 (M+) 370.1053. Found: 370.1042.
2-(6-Carboxyhexyl)-5,7,4’-trihydroxyisoflavone (3i)
White solid; yield: 93 mg (96%), mp 201 °C from EtOAc-acetone.
1H NMR (200 MHz, acetone-d6): d = 1.26-1.47 (m, 4H, H-3", H-
4"), 1.56 (quintet, 2H, J = 7.1 Hz, H-5"), 1.72 (quintet, 2H, J = 7.4
Hz, H-2"), 2.25 (t, 2H, J = 7.3 Hz, H-6"), 2.60 (t, 2H, J = 7.5 Hz, H-
1"), 6.25 (d, 1H, J = 2.2 Hz, H-6), 6.41 (d, 1H, J = 2.2 Hz, H-8),
6.91 (d, 2H, J = 8.4 Hz, H-3', H-5'), 7.16 (d, 2H, J = 8.4 Hz, H-2',
H-6').
Anal. Calc for C20H18O6: C, 67.79, H, 5.12. Found: C, 67.85, H,
5.13.
2-(6-Carboxyhexyl)-7,4’-dihydroxyisoflavone (3e)
MS: m/z (%) = 398 (M+, 100), 369 (4), 339 (5), 311 (7), 297 (67),
White solid; yield: 92 mg (95%); mp 171 °C from EtOAc-acetone.
1H NMR (200 MHz, acetone-d6): d = 1.27-1.32 (m, 4H, H-3", H-
4"), 1.55 (quintet, 2H, J = 7.0 Hz, H-5"), 1.72 (quintet, 2H, J = 7.4
Hz, H-2"), 2.25 (t, 2H, J = 7.3 Hz, H-6"), 2.59 (t, 2H, J = 7.7 Hz, H-
1"), 6.87 (d, 2H, J = 8.4 Hz, H-3', H-5'), 6.89 (d, 1H, J = 2.2 Hz, H-
8), 6.95 (dd, 1H, J = 8.8, 2.2 Hz, H-6), 7.11 (d, 2H, J = 8.4 Hz, H-
2', H-6'), 7.96 (d, 1H, J = 8.8 Hz, H-5).
MS: m/z (%) = 382 (M+, 50), 323 (8), 295 (12), 281 (100), 268 (21),
252 (7), 137 (9), 131 (6).
HRMS: m/z calc for C22H22O6 (M+) 382.1416. Found 382.1413.
283 (13), 153 (9), 131 (5).
HRMS: m/z calc for C22H22O7 (M+) 398.1366. Found: 398.1375.
Anal. Calc for C22H22O7: C, 66.32, H, 5.57. Found: C, 66.04, H,
5.53.
2-(8-Carboxyoctyl)-5,7,4’-trihydroxyisoflavone (3j)
White solid; yield: 92 mg (95%), mp 181 °C from EtOAc-acetone.
1H NMR (200 MHz, acetone-d6): d = 1.26 (br, 8H, H-3", H-4", H-
5", H-6"), 1.56 (quintet, 2H, J = 7.0 Hz, H-7"), 1.70 (quintet, 2H,
J = 7.2 Hz, H-2"), 2.27 (t, 2H, J = 7.5 Hz, H-8"), 2.59 (t, 2H, J = 7.7
Hz, H-1"), 6.24 (d, 1H, J = 2.2 Hz, H-6), 6.41 (d, 1H, J = 2.2 Hz, H-
8), 6.91 (d, 2H, J = 8.6 Hz, H-3', H-5'), 7.14 (d, 2H, J = 8.6 Hz, H-
2', H-6').
Anal. Calc for C22H22O6: C, 69.10, H, 5.80. Found: C, 68.80, H,
5.74.
2-(8-Carboxyoctyl)-7,4’-dihydroxyisoflavone (3f)
MS: m/z (%) = 426 (M+, 100), 367 (7), 339 (7), 297 (80), 284 (20),
White solid; yield: 93 mg (96%); mp 199 °C from EtOAc-acetone.
1H NMR (200 MHz, acetone-d6): d = 1.26 (br, 8H, H-3", H-4", H-
5", H-6"), 1.56 (quintet, 2H, J = 7.0 Hz, H-7"), 1.71 (quintet, 2H,
J = 7.3 Hz, H-2"), 2.26 (t, 2H, J = 7.1 Hz, H-8"), 2.58 (t, 2H, J = 7.7
Hz, H-1"), 6.88 (d, 2H, J = 8.4 Hz, H-3', H-5'), 6.89 (d, 1H, J = 2.2
Hz, H-8), 6.94 (dd, 1H, J = 8.8, 2.2 Hz, H-6), 7.11 (d, 2H, J = 8.4
Hz, H-2', H-6'), 7.96 (d, 1H, J = 8.8 Hz, H-5).
MS: m/z (%) = 410 (M+, 47), 392 (4), 351 (7), 323 (5), 295 (11), 281
(100), 268 (28), 252 (7), 137 (9), 131 (5).
HRMS: m/z calc for C24H26O6 (M+) 410.1729. Found: 410.1732.
153 (15), 131 (7).
HRMS: m/z calc for C24H26O7 (M+) 426.1678. Found: 426.1668.
Anal. Calc for C24H26O7: C, 67.59, H, 6.15. Found: C, 67.06, H,
5.94.
X-ray Crystal Structure Analysis
Crystal data for 2g (C21H20O7) M = 384.37, monoclinic P21/n (no.
14), a = 9.553(2), b = 14.637(3), c = 13.386(3) Å, b = 100.08(3) E,
V = 1842.8(6) Å3, Z = 4, Dc = 1.385 gcm-3, T = 193(1) K, m(Mo-
Ka) = 0.0875 mm–1, F(000) = 808, R1 = 0.049, wR2 = 0.1167 with
I>2s(I), S = 0.911, 2796 data collected, 1935 I>2s(I), 296 parame-
ters (Table 3).
Anal. Calc for C24H26O6: C, 70.23, H, 6.38. Found: C, 69.86, H,
6.25.
Synthesis 2000, No. 3, 411–416 ISSN 0039-7881 © Thieme Stuttgart · New York

416
N. Al-Maharik et al.
PAPER
A colorless crystal with dimensions of 0.30 x 0.22 x 0.16 mm was
mounted to the glass fiber using the oil-drop method.9 The data was
collected using Enraf-Nonius CAD-4 diffractometer, graphite
monochromatizad Cu-Ka radiation (l = 1.54184 Å) in w-2q-mode.
Data reduction was done using the XCAD-4 package.10 The inten-
sity data were corrected for Lorentz and polarization effects and for
absorption and extinction. The structure was solved using direct
methods. All non-H atoms were refined anisotropically. The atoms
C4¢¢’, O6, O7, and C5¢¢ were disordered and refined in two positions
with population parameters of 0.4 and 0.6. H atoms were refined us-
ing a riding model. The final difference Fourier map had peak max-
ima of 0.220 and minima 0.221 eÅ-3. Programs from the Siemens
SHELXTL- package and SHELXL-97 were used for the solution,
refinement, and graphical representation of the structure.11,12 Full
crystallographic data has been deposited at Cambridge Crystallo-
graphic Data Centre and is available as supplementary information.
(3) Lapcik, O.; Hampl, R.; Hill, M.; Wähälä, K.; Al-Maharik, N.;
Adlercreutz ,H. J. Steroid Biochem. Molec. Biol. 1998, 64,
261.
(4) Lapcik, O.; Hill, M.; Hampl, R.; Wähälä, K.; Adlercreutz, H.,
Steroids 1998, 63, 14.
(5) Mazur, W.; Wähälä, K.; Wang, G.; Adlercreutz, H. Kemia-
Kem. 1998, 25, 48.
(6) Adlercreutz, H. In Reproductive and Developmental
Toxicology; Korach, K. S., Ed.; Marcel Dekker: New York,
1998; p 299.
(7) Fotsis, T.; Pepper, M. S.; Aktas, E.; Breit, S.; Rasku, S.;
Adlercreutz, H.; Wähälä, K.; Montesano, R.; Schweigerer, L
Bailliére´s Clin. Endocrinol. Metab., vol. 12, 1998, 649.
(8) Baker, W.; Chadderton, J.; Harborne, J. B.; Ollis W. D. J.
Chem. Soc. 1953, 1852.
(9) Kottke, T.; Stalke, D. J. Appl. Crystallogr. 1993, 26, 615.
(10) Harms, K.; Wocadlo, S. 1995, XCAD-4. Program for
Processing CAD-4 Diffractometer Data., University of
Marburg, Germany.
Acknowledgement
(11) Sheldrick, G. M. 1994, SHELXTL-PC. Realease 5.03
Siemens Analytical X-Ray Instruments Inc., Madison, WI
53719, USA.
(12) Sheldrick, G. M. SHELXL-97. Program for the Refinement of
Crystal Structures. University of Göttingen, Germany.
We thank Dr. Jorma Matikainen for running the mass spectra, Mr.
Seppo Kaltia for the 2D-NMR spectra, and Mr. Torsten Eifler for
the skilful laboratory assistance. Financial support to KW from Uni-
versity of Helsinki is gratefully acknowledged.
References
Article Identifier:
(1) Pelter, A.; Ward, R. S.; Whalley J. Synthesis 1998, 1973.
(2) Lapcik, O.; Hampl, R.; Al-Maharik, N.; Salakka, A.; Wähälä,
K.; Adlercreutz, H. Steroids 1997, 62, 315.
1437-210X,E;2000,0,03,0411,0416,ftx,en;Z07199SS.pdf
Synthesis 2000, No. 3, 411–416 ISSN 0039-7881 © Thieme Stuttgart · New York