Preparation and promotion of fruit growth in kiwifruit of fluorinated N-phenyl-N′-1,2,3-thiadiazol-5-yl ureas

Article abstract of DOI:10.1021/jf049921+

Seventeen phenyl-fluorinated analogues of thidiazuron [N-phenyl-N′- (1,2,3-thiadiazol-5-yl)urea, TDZ] have been prepared and characterized. The effects of each fluorinated urea on growth and quality of kiwifruits (Actinidia deliciosa) were evaluated by co

Full text of DOI:10.1021/jf049921+

J. Agric. Food Chem. 2004, 52, 4675−4683 4675
Preparation and Promotion of Fruit Growth in Kiwifruit of
Fluorinated N-Phenyl-N′-1,2,3-thiadiazol-5-yl Ureas
ANTONIO ABAD,* CONSUELO AGULL OÄ ,* ANA CARMEN CU N˜ AT,
RAQUEL JIM EÄ NEZ, AND CRISTINA VILANOVA
Departamento de Qu ´ı mica Org a´ nica, Facultad de Qu ´ı micas, Universidad de Valencia,
C/Dr. Moliner 50, E-46100 Burjassot, Valencia, Spain
Seventeen phenyl-fluorinated analogues of thidiazuron [N-phenyl-N′-(1,2,3-thiadiazol-5-yl)urea, TDZ]
have been prepared and characterized. The effects of each fluorinated urea on growth and quality
of kiwifruits (Actinidia deliciosa) were evaluated by comparison with untreated (control) and TDZ-
treated fruits. The results obtained showed a clear dependence of the growth-promoting activity of
these fluorinated ureas on the pattern and degree of fluorine substitution in the phenyl ring. The
most effective for promoting fruit growth was N-(2,3,5,6-tetrafluorophenyl)-N′-(1′,2′,3′-thiadiazol-5′-
yl)urea at 25 ppm (at harvest, treated fruits were 58% heavier than untreated ones) followed by
N-(3,5-difluorophenyl)-N′-(1′,2′,3′-thiadiazol-5′-yl)urea at 10 ppm (50%). Comparatively, TDZ-treated
fruits were 31% (10 ppm) and 38% (25 ppm) heavier than untreated ones. The results also indicate
that the effects of the more active phenyl-fluorinated ureas on some standard quality parameters of
fruits, for example, percent of fruit dry matter content, soluble solids contents, total titratable acids,
shape, and internal structure, are similar to those of TDZ. Quantitative structure-activity relationships
have been derived for the fruit growth promoting activity of the phenyl-fluorinated analogues of TDZ.
KEYWORDS: Actinidia deliciosa; kiwifruit; cytokinin; phenylurea; fluor; fluorinated; thidiazuron; TDZ;
fruit-growth activity; plant hormones; QSAR, substituent-induced chemical shifts
INTRODUCTION
several currently marketed formulations used for application not
only in kiwifruit but also in other important horticultural crops
such as melons, watermelons, and grapes (3). Recently, thia-
diazuron [1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea, TDZ, 2a], a
compound that is largely used as a defoliant in cotton (4), has
also proved to be very effective in stimulating kiwifruit growth,
producing a weight and size increase in fruits similar to those
produced by CPPU (5).
Control of plant growth with plant hormones has become an
important technique in agricultural and horticultural fields, and
in recent years substantial research efforts have been devoted
to finding new compounds that exhibit cytokinin-like hormonal
activity. For some fruit crops, such as kiwifruit (Actinidia
deliciosa), the production of larger and more uniform fruits has
become vital for the economic viability of the crop. Although
the use of traditional cultivation practices such as bee-aided
pollination and proper fertilization and irrigation may positively
affect the quality and size of the fruit, the use of growth
promoters gives extraordinary results and is becoming an
important technique in this sector. Early studies on kiwifruit
growth-promoting hormones begun in 1976 by Hopping (1)
found that some combinations of endogenous hormones, for
example, auxins, gibberellins, and cytokinins, were able to
effectively promote fruit growth. Since then, several other
compounds have also proved to be effective in improving
kiwifruit growth, but the most efficient and best-known of all
compounds tested so far is the synthetic phenylurea 1-(2-chloro-
The almost equivalent results obtained with CPPU and TDZ
in stimulating kiwifruit growth are not surprising, in view of
the structural similarity between both compounds that suggests
a common molecular mechanism of action. It is thought that
the increase in fruit size is due to a specific cell division or
expansion in the early stages of fruit development of treated
fruits, an effect that has been related with an intrinsic cytokinin
activity of these phenylureas (6) or an increase in the endog-
enous cytokinin levels either by inhibiting the action of cytokinin
oxidase on the endogenous cytokinins or by stimulating the
production of endogenous cytokinins (7).
Selective replacement of hydrogen by fluorine has been a
successful strategy in agrochemical and medicinal chemistry
in the search for compounds with increased biological activity
4
-pyridyl)-3-phenylurea (1a), also known as CPPU, forchlor-
fenuron, or KT-30 (2). In fact, CPPU is the active ingredient of
(
8). More concretely, the introduction of fluorine atoms in the
*
Correspondence should be addressed to Dr. Antonio Abad, Departa-
aromatic moiety of biologically active compounds may modify
their electronic and physical properties (for example, lipophi-
licity, acidity, and steric hindrance) (9), generally resulting in
mento de Qu ´ı mica Org a´ nica, Facultad de Qu ´ı micas, C/Dr. Moliner 50, 46100
Burjassot (Valencia), Spain (telephone 34-96-3544509; fax 34-96-3544328;
e-mail antonio.abad@uv.es).
1
0.1021/jf049921+ CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/24/2004

4676 J. Agric. Food Chem., Vol. 52, No. 15, 2004
Abad et al.
Scheme 1
SOCD
referenced to CFCl
spectra were measured as KBr pellets using a Nicolet Avatar 320
spectrometer. High-resolution mass spectra were recorded with a VG
AutoSpec spectrometer using the EI method (70 eV). Column chro-
matography purification was carried out using Merck silica gel 60, 230-
3
in DMSO-d
6
, set at δ 2.42, and 19F NMR chemical shifts are
as internal reference, which was set at δ 0.000. IR
more active and efficient compounds. A recent example is found
with fluorinated inhibitors of carbonic anhydrase II (CAII) (10,
3
1
1), which show distinct binding modes depending on the
patterns and degree of fluorine substitution in the aromatic
moiety of the inhibitor.
Some fluorinated analogues of CPPU [1-(2-chloro-4-pyridyl)-
4
00 mesh. Thin-layer chromatography (TLC) was carried out using
TLC C-18 reversed-phase TLC plates with fluorescent indicator (Merck
RP-18 F254S). The R (retention factor) refers to plates developed in
3-(2-fluorophenyl)urea (1b) (12), 1-(2-chloro-4-pyridyl)-3-(3-
fluorophenyl)urea (1c) (13), 1-(2-chloro-4-pyridyl)-3-(4-fluo-
rophenyl)urea (1d) (14), and 1-(2-chloro-4-pyridyl)-3-(3,5-
difluorophenyl)urea (1e) (15)] have been prepared, and the high
cytokinin activity of some of them, for example, 1c, has been
demonstrated in tobacco callus growth in vitro assays. However,
the correlation between the patterns and degree of fluorine
substitution at the phenyl ring of these compounds and cytokinin
activity has not yet been systematically studied. As far as we
know, no fluorinated analogue of TDZ has been prepared nor
any phenyl-fluorinated urea-type cytokinin tested as a fruit-
growth promoter.
f
70:30 methanol/water (v/v). The R range was 0.117-0.478.
f
Synthesis of Ureas 2b-2r. The preparation of phenyl-fluorinated
ureas 2b-2r was effected by reaction of 1,2,3-thiadiazole-5-carbonyl
azide (5), prepared from 1,2,3-thiadiazole-5-carboxylic acid (3), with
the appropriate commercially available mono-, di-, tri-, tetra-, or
pentafluoroanilines, 6b-6r (Scheme 1). The preparation and purifica-
tion of 2j, 2p, and 2r described below are representative examples.
Preparation of 1,2,3-Thiadiazole-5-carbonyl Azide (5). A solution
of 1,2,3-thiadiazole-5-carboxylic acid (3, 6.0 g, 46 mmol), prepared as
described by Arndt (16), in SOCl
2
(20 mL, 274 mmol) was heated at
was distilled under
8
0 °C with stirring for 2 h. The excess of SOCl
2
We describe in this work the preparation of a small library
of mono-, di-, tri-, tetra-, and pentafluorophenyl analogues of
TDZ, ureas 2b-2r, and the testing of their growth-promoting
reduced pressure (40 °C, 210 mmHg) to give an oily residue. Addition
of dry toluene (20 mL) and removal of the solvent under vacuum (85
°C, 50 mmHg) afforded crude 1,2,3-thiadiazole-5-carbonyl chloride (4)
as a yellowish oil (6.8 g).
A solution of the above acyl chloride in dry acetone (25 mL) was
dropwise added to a stirred solution of NaN (3.32 g, 52 mmol) in
3
water (20 mL). After 1 h, the reaction mixture was poured into water
and extracted with hexane. Combined organic extracts were washed
with water and brine, dried (MgSO
to give spectroscopically pure 1,2,3-thiadiazole-5-carbonyl azide (5,
.2 g, 74% from acid 3) as a yellow oil that was used without further
4
), and concentrated under vacuum
5
purification for the preparation of the ureas.
Preparation of 1-(3,5-Difluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)-
urea (2j). To a stirred solution of 3,5-difluoroaniline (6j, 417.5 mg,
3.23 mmol) in toluene (2.3 mL) at reflux was added dropwise a solution
of 5 (455.6 mg, 2.94 mmol) in toluene (2.3 mL). The reaction mixture
was stirred for an additional 1 h at reflux and then cooled to room
temperature. The solid was collected by filtration and washed with a
1
:1 mixture of hexane/toluene and hexane and dried under vacuum to
give pure 2j (760.3 mg, 92%) as a white solid: mp 227 °C with decomp
1
(
from hexane/acetone); R
f 6
0.170; H NMR (DMSO-d ) δ 11.10 (1H, s,
NH3), 9.86 (1H, s, NH1), 8.62 (1H, s, H-4′), 7.22 (2H, dddd, J )
1
2
1.8, 2.8. 2.3, and 2.0 Hz, H-2 and H-6), 6.87 (1H, dddd, J ) 9.4, 9.4,
.3, and 2.3 Hz, H-4); 19F NMR (DMSO-d
) δ -108.7 (s, F-3 and
6
F-5); IR (KBr) 3291, 3169, 3106, 2972, 1710, 1616, 1566, 1477, 1310,
-
1
1
2
250, 1196, 1120, 977, 730, 660 cm ; HRMS, calcd for C
56.0230, found 256.0232.
9 6 2 4
H F N OS
Preparation of 1-(2,3,4,6-Tetrafluorophenyl)-3-(1′,2′,3′-thiadiazol-
′-yl)urea (2p). To a stirred solution of 2,3,4,6-tetrafluoroaniline (6p,
30 mg, 3.82 mmol) in benzene (3.5 mL) at reflux was added dropwise
effects on kiwifruits, with respect to weight, size, and some
other quality attributes.
5
6
a solution of 5 (536.0 mg, 458 mmol) in benzene (3.5 mL). The reaction
mixture was stirred for an additional 5 h at reflux and then cooled to
room temperature. The solid was filtered off and washed successively
with a 1:1 mixture of hexane/benzene and hexane. The yellowish solid
obtained was subjected to extraction with acetone, and the extracts were
evaporated under vacuum to give spectroscopically pure urea 2p (850.7
MATERIALS AND METHODS
Synthetic Procedures. All reactions were carried out with the
exclusion of moisture. All NMR spectra were recorded in DMSO-d
6
-
2
1
19
-1
13
[
(4-6) × 10 M for H and F and (1.6-2.3) × 10 M for C] at
room temperature on a Bruker AC-300 spectrometer (300.13 MHz for
H, 282.37 MHz for F, and 75.47 MHz for C). All H NMR chemical
shifts are reported in parts per million relative to the residual CHD
1
19
13
1
mg, 85%): mp 255 °C with decomp (from hexane/acetone); R
f
0.340;
1
2
-
H NMR (DMSO-d ) δ 11.36 (1H, s, NH3), 9.28 (1H, s, NH1), 8.57
6

Effect of Phenyl-fluorinated Ureas on Kiwifruit
1H, s, H-4′), 7.66 (1H, dddd, J ) 10.2, 10.2, 7.2, and 2.3 Hz, H-5);
J. Agric. Food Chem., Vol. 52, No. 15, 2004 4677
(
3022, 1701, 1641, 1579, 1545, 1500, 1320, 1246, 1194, 820, 746 cm-1.
1
9
F NMR (DMSO-d
6
) δ -164.3 (ddd, J ) 22.7, 22.7, and 10.3 Hz,
HRMS, calcd for C
Data for 1-(2,6-Difluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
(2h): yield 92%; mp 216 °C with decomp (from DMSO/H O); R 0.479;
) δ 11.27 (1H, s, NH3), 9.10 (1H, s, NH1), 8.56
(1H, s, H-4′), 7.37 (1H, dddd, J ) 8.1, 8.1, 6.5, and 6.5 Hz, H-4), 7.17
(2H, m, H-3 and H-5); 19F NMR (DMSO-d
) δ -118.1 (s, F-2 and
F-6); IR (KBr) 3255, 3174, 2993, 1698, 1561, 1470, 1313, 1245, 1190,
9 6 2 4
H F N OS 256.0230, found 256.0243.
F-3), -138.1 (dd, J ) 22.7 and 4.1 Hz, F-2), -134.8 (dd, J ) 22.7
and 4.1 Hz, F-4), -121.1(d, J ) 10.3 Hz, F-6); IR (KBr) 3262, 3228,
2
f
-1
1
3164, 3072, 2967, 1702, 1570, 1499, 1484, 1307, 1072, 816, 793 cm
;
H NMR (DMSO-d
6
HRMS, calcd for C OS 292.0042, found 292.0050.
9 4 4 4
H F N
Preparation of 1-(Pentafluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)-
urea (2r). To a stirred solution of 2,3,4,5,6-pentafluoroaniline (6r, 570.6
mg, 3.08 mmol) in benzene (4 mL) at reflux was slowly added (∼30
min) a solution of 5 (439.2 mg, 2.8 mmol) in the same solvent (4 mL).
The reaction mixture was stirred under reflux for 4 h and then
concentrated under vacuum, and the solid residue was deposited on a
short column of silica gel and eluted with acetone. Evaporation of the
6
-
1
1002, 777, 702 cm ; HRMS, calcd for C
256.0222.
9 6 2 4
H F N OS 256.0230, found
Data for 1-(3,4-Difluorophenyl)-2-(1′,2′,3′-thiadiazol-5′-yl)urea
(2i): yield 83%; mp 239 °C with decomp (from hexane/acetone); R
f
1
0.223; H NMR (DMSO-d ) δ 10.99 (1H, s, NH3), 9.66 (1H, s, NH1),
6
solvent under reduced pressure afforded spectroscopically pure urea
8.61 (1H, s, H-4′), 7.61 (1H, ddd, J ) 13.0, 7.4, and 2.5 Hz, H-2),
7.36 (1H, ddd, J ) 9.6, 9.6, and 9.4 Hz, H-5), 7.22-7.19 (1H, m,
1
2
r (630 mg, 72%): mp 260-265 °C (from DMSO/H
2
O); R
f
0.245; H
H-6); 19F NMR (DMSO-d
6
) δ -136.6 (d, J ) 23.2 Hz, F-3), -144.7
(d, J ) 23.2 Hz, F-4); IR (KBr) 3286, 3243, 3143, 3115, 2956, 1702,
NMR (DMSO-d
6
) δ 11.44 (1H, s, NH3), 9.52 (1H, s, NH1), 8.58 (1H,
s, H-4′); F NMR (DMSO-d ) δ -162.9 (m, F-3 and F-5), -157.0 (t,
J ) 22.7 and 22.7 Hz, F-4), -145.5 (m, F-2 and F-6); IR (KBr) 3276,
1
9
6
-1
1627, 1585, 1547, 1518, 1302, 1272, 1239, 1204, 1192, 854, 818 cm
HRMS, calcd for C OS 256.0230, found 256.0236.
Data for 1-(2,3,4-Trifluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
2k): yield 91%; mp 263 °C with decomp (from hexane/acetone); R
;
-
1
3
225, 3006, 1713, 1578, 1528, 1505, 1308, 1197, 970 cm ; HRMS,
calcd for C OS 309.9948, found 309.9950.
Data for 1-(2-Fluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea (2b):
yield 89%; mp 242 °C with decomp (from hexane/acetone); R 0.309;
) δ 10.97 (1H, s, NH3), 9.16 (1H, s, NH1), 8.64
1H, s, H-4′), 7.94 (1H, ddd, J ) 8.1, 8.1 and 1.8 Hz, H-6), 7.24 (1H,
9 6 2 4
H F N
9
3 5 4
H F N
(
0
f
1
6
.223; H NMR (DMSO-d ) δ 11.07 (1H, s, NH3), 9.37 (1H, s, NH1),
f
1
8.64 (1H, s, H-4′), 7.64 (1H, dddd, J ) 9.0, 9.0, 5.3, and 2.3 Hz, H-6),
H NMR (DMSO-d
6
7
.29 (1H, dddd, J ) 10.2, 9.0, 9.0, and 2.1 Hz, H-5); 19F NMR (DMSO-
) δ -160.8 (dd, J ) 22.6 and 20.6 Hz, F-3), -146.4 (dd, J ) 20.6
(
d
6
ddd, J ) 11.2, 7.7, and 1.5 Hz, H-3), 7.15 (1H, ddd, J ) 8.1, 7.7, and
1
.5 Hz, H-5), 7.10 (1H, dddd, J ) 7.7, 7.7, 5.1, and 1.8 Hz, H-4)’ 19
and 2.1 Hz, F-2), -141.1 (dd, J ) 22.6 and 2.1 Hz, F-4); IR (KBr)
268, 3013, 1698, 1635, 1518, 1478, 1306, 1251, 1191, 1022, 818,
F
3
NMR (DMSO-d
6
) δ -127.3 (s); IR (KBr) 3269, 3208, 3028, 1698,
-
1
-1
and 685 cm ; HRMS, calcd for C
74.0138.
Data for 1-(2,3,6-Trifluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
9 5 3 4
H F N OS 274.0136, found
9 7
1629, 1561, 1529, 1308, 1184, 755, 731 cm ; HRMS, calcd for C H -
2
4
FN OS 238.0325, found 238.0318.
Data for 1-(3-Fluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea (2c):
yield 82%; mp 238 °C with decomp (from hexane/acetone); R 0.266;
) δ 10.92 (1H, s, NH3), 9.65 (1H, s, NH1), 8.61
(
2l): yield 88%; mp 256 °C with decomp (from hexane/acetone); R
f
f
1
1
0.426; H NMR (DMSO-d
6
) δ 11.34 (1H, s, NH3), 9.32 (1H, s, NH1),
H NMR (DMSO-d
6
8
7
d
.58 (1H, s, H-4′), 7.47 (1H, dddd, J ) 9.6, 9.6, 9.6, and 4.9 Hz, H-4),
(
(
1H, s, H-4′), 7.43 (1H, ddd, J ) 11.7, 2.0, and 2.0 Hz, H-2), 7.32
1H, ddd, J ) 8.0, 8.0, and 7.5 Hz, H-5), 7.21 (1H, ddd, J ) 8.0, 2.0,
.23 (1H, dddd, J ) 9.6, 9.6, 4.5, and 2.3 Hz, H-5); 19F NMR (DMSO-
6
) δ -141.4 (dd, J ) 22.7 and 14.5 Hz, F-3), -140.2 (d, J ) 22.7
and 2.0 Hz, H-6), 6.83 (1H, dddd, J ) 8.3, 8.0, 2.0, and 2.0 Hz, H-4);
1
9
Hz, F-2), -122.6 (d, J ) 14.5 Hz, F-6); IR (KBr) 3211, 3174, 2999,
F NMR (DMSO-d
613, 1556, 1487, 1441, 1301, 1277, 1194, 872, 816, 794 cm ; HRMS,
calcd for C FN OS 238.0325, found 238.0331.
Data for 1-(4-Fluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea (2d):
yield 93%; mp 259 °C with decomp (from hexane/acetone); R 0.309;
) δ 10.86 (1H, s, NH3), 9.45 (1H, s, NH1), 8.59
1H, s, H-4′), 7.47 (2H, ddd, J ) 8.9, 5.0, and 2.0 Hz, H-2 and H-6),
.13 (2H, ddd, J ) 8.9, 8.9, and 2.1 Hz, H-3 and H-5); 19F NMR
DMSO-d ) δ -119.2 (s); IR (KBr) 3288, 3146, 3108, 2948, 1702,
624, 1574, 1509, 1302, 1203, 1187, 1161, 835, 817, 795 cm-1; HRMS,
FN OS 238.0325, found 238.0326.
Data for 1-(2,3-Difluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
6
) δ -111.6 (s); IR (KBr) 3275, 3146, 2940, 1701,
-
1
-1
1708, 1638, 1574, 1557, 1486, 1306, 1254, 1190, 1000, 815 cm
HRMS, calcd for C OS 274.0136, found 274.0127.
Data for 1-(2,4,5-Trifluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
;
1
9
5 3 4
H F N
9
H
7
4
1
(2m): yield 89%; mp 245 °C (from hexane/acetone); R
f
0.181; H NMR
f
(
DMSO-d ) δ 11.01 (1H, s, NH3), 9.34 (1H, s, NH1), 8.67 (1H, s,
6
1
H NMR (DMSO-d
6
H-4′), 7.99 (1H, ddd, J ) 12.4, 8.1, and 8.1 Hz, H-6), 7.66 (1H, ddd,
(
7
(
1
J ) 10.7, 10.7, and 7.5 Hz, H-3); 19F NMR (DMSO-d
6
) δ -142.0 (dd,
J ) 23.7 and 13.4 Hz, F-5), -141.1 (d, J 2) 3.7 Hz, F-4), -128.6 (d,
J ) 13.4 Hz, F-2); IR (KBr) 3273, 3034, 2999, 1698, 1650, 1582,
6
-
1
1
532, 1506, 1434, 1302, 1213, 1202, 1192, 782, 737 cm ; HRMS,
calcd for C OS 274.0136, found 274.0138.
Data for 1-(2,4,6-Trifluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
calcd for C
9
H
7
4
9 5 3 4
H F N
1
(
2e): yield 90%; mp 229-230 °C (from hexane/acetone); R
NMR (DMSO-d ) δ 11.06 (1H, s, NH3), 9.39 (1H, s, NH1), 8.67 (1H,
s, H-4′), 7.78 (1H, dddd, J ) 8.1, 6.8, 2.0, and 2.0 Hz, H-6), 7.16 (2H,
f
0.255; H
1
(
2n): yield 77%; mp 244-245 °C (from hexane/acetone); R
NMR (DMSO-d ) δ 11.30 (1H, s, NH3), 9.02 (1H, s, NH1), 8.55 (1H,
s, H-4′), 7.31 (2H, dd, J ) 8.9 and 8.3 Hz, H-3 and H-5); F NMR
DMSO-d ) δ -114.9 (d, J ) 6.2 Hz, F-2 and F-6), -108.6 (s, F-4);
f
0.426; H
6
6
19
1
9
m, H-4 and H-5 overlapped); F NMR (DMSO-d
2
3
6
) δ -151.4 (d, J )
(
6
1.1 Hz, F-2), -138.0 (d, J ) 21.1 Hz, F-3); IR (KBr) 3278, 3221,
IR (KBr) 3230, 3142, 3081, 3029, 2967, 1686, 1545, 1514, 1445, 1296,
244, 1124, 1031, 1000, 866, 823, 708 cm ; HRMS, calcd for
-
1
040, 1708, 1634, 1577, 1542, 1479, 1314, 1264, 1191, 975 cm
OS 256.0230, found 256.0226.
Data for 1-(2,4-Difluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
2f): yield 83%; mp 225 °C with decomp (from hexane/acetone); R
;
-1
1
9 6 2 4
HRMS, calcd for C H F N
C
9
H F
5 3
4
N OS 274.0136, found 274.0136.
Data for 1-(2,3,4,5-Tetrafluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)-
(
0
f
urea (2o): yield 79%; mp 263-266 °C (from hexane/acetone); R 0.117;
f
1
1
.298; H NMR (DMSO-d
6
) δ 11.04 (1H, s, NH3), 9.18 (1H, s, NH1),
H NMR (DMSO-d ) δ 11.07 (1H, s, NH3), 9.56 (1H, s, NH1), 8.68
6
8
.63 (1H, s, H-4′), 7.84 (1H, ddd, J ) 9.0, 8.7, and 6.4 Hz, H-6), 7.30
(1H, s, H-4′), 7.86 (1H, dddd, J ) 12.4, 9.9, 7.7, and 2.4 Hz, H-6); 19
NMR (DMSO-d ) δ -163.2 (dd, J ) 22.7 and 22.6 Hz, F-4), -156.6
F
(1H, ddd, J ) 11.3, 8.9, and 2.5 Hz, H-3), 7.06 (1H, ddd, J ) 8.7, 8.7,
6
1
9
and 2.5 Hz, H-5); F NMR (DMSO-d
F-4); IR (KBr) 3226, 3146, 3039, 2952, 1698, 1576, 1505, 1305, 1301,
249, 1204, 1107, 843 cm-1; HRMS, calcd for C
OS 256.0230,
found 256.0240.
Data for 1-(2,5-Difluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)urea
2g): yield 83%; mp 255 °C with decomp (from DMSO/H O); R 0.223;
) δ 11.04 (1H, s, NH3), 9.36 (1H, s, NH1), 8.69
6
) δ -121.1 (s, F-2), -114.6 (s,
(dd, J ) 22.6 and 21.7 Hz, F-3), -151.4 (dd, J ) 21.7 and 9.3 Hz,
F-2), -139.3 (dd, J ) 22.7 and 9.3 Hz, F-5); IR (KBr) 3163, 3084,
1
H F N
9 6 2 4
2999, 1701, 1652, 1591, 1526, 1481, 1308, 1245, 1201, 1184, 1015,
964, 951, 713 cm-1; HRMS, calcd for C H F N OS 292.0042, found
9
4
4
4
292.0033.
Data for 1-(2,3,5,6-Tetrafluorophenyl)-3-(1′,2′,3′-thiadiazol-5′-yl)-
(
2
f
1
H NMR (DMSO-d
6
urea (2q): yield 70%; mp 255-258 °C (from hexane/acetone); R
f
0.340;
1
(
(
8
1
1H, s, H-4′), 7.85 (1H, ddd, J ) 10.0, 6.4, and 3.2 Hz, H-6), 7.31
H NMR (DMSO-d
6
) δ 11.39 (1H, s, NH3), 9.55 (1H, s, NH1), 8.60
1H, ddd, J ) 10.4, 9.2, and 5.1 Hz, H-3), 6.92 (1H, dddd, J ) 9.2,
(1H, s, H-4′), 7.88 (1H, dddd, J ) 10.7, 10.7, 7.5, and 7.5 Hz, H-4);
1
9
19
.5, 3.2, and 3.2 Hz, H-4); F NMR (DMSO-d
6
) δ -133.1 (d, J )
F NMR (DMSO-d
6
) δ -145.9 (dd, J ) 23.7 and 11.3 Hz, F-2 and
5.5 Hz, F-2), -116.1 (d, J ) 15.5 Hz, F-5); IR (KBr) 3262, 3210,
F-6), -139,7 (dd, J ) 23.7 and 11.3 Hz, F-3 and F-5); IR (KBr) 3284,

4
678 J. Agric. Food Chem., Vol. 52, No. 15, 2004
Abad et al.
Table 1. Effects of Treatments with TDZ (2a) and Ureas 2b−2r on
-1
3249, 3189, 3021, 1721, 1567, 1519, 1483, 1309, 1198, 1178, 937 cm ;
HRMS, calcd for C OS 292.0042, found 292.0047.
H F
9 4 4
N
4
a
Fruit Weight at Harvest
Effects of Phenyl-fluorinated Ureas 2b-2r on Kiwifruit Growth.
The experiments were performed at the end of May 2002 in Almussafes
urea (ppm)
fresh wt (g)
urea (ppm)
fresh wt (g)
(
Valencia, Spain) on mature vines of Actinidia deliciosa (A. Chev.) of
the cv. Hayward with cv. Matua and Tomuri at 50% as pollinizer (8:
). The vines used were from the same orchard blocks. The treatment
control (0)
TDZ (10)
TDZ (25)
2b (10)
115.0 ± 22.9
150.2 ± 13.0 (30.6)
159.0 ± 11.3 (38.2)
133.2 ± 16.2 (15.8)
163.5 ± 20.1 (42.2)
149.3 ± 15.9 (29.8)
138.8 ± 10.5 (20.7)
120.3 ± 12.5 (4.6)
123.1 ± 9.9 (7.0)
158.2 ± 20.5 (37.5)
144.7 ± 18.2 (25.8)
119.0 ± 9.8 (3.5)
138.8 ± 9.2 (20.7)
116.2 ± 16.5 (1.0)
108.6 ± 15.4 (−5.6)
126.5 ± 8.1 (10.0)
132.6 ± 8.7 (15.3)
144.2 ± 17.6 (25.4)
136.3 ± 18.9 (18.5)
2j (10)
2j (25)
2k (10)
2k (25)
2l (10)
2l (25)
2m (10)
2m (25)
2n (10)
2n (25)
2o (10)
2o (25)
2p (10)
2p (25)
2q (10)
2q (25)
2r (10)
2r (25)
172.5 ± 30.8 (50.0)
159.5 ± 22.5 (38.7)
120.4 ± 16.3 (4.7)
136.1 ± 15.9 (18.3)
147.8 ± 5.7 (28.5)
124.6 ± 9.9 (8.31)
121.8 ± 14.4 (5.9)
137.6 ± 17.7 (19.6)
141.0 ± 10.9 (22.6)
136.0 ± 10.2 (18.3)
105.7 ± 13.9 (−8.0)
93.4 ± 9.2 (−18.8)
131.9 ± 6.5 (14.7)
133.0 ± 4.4 (15.7)
153.7 ± 23.8 (33.6)
181.3 ± 25.2 (57.6)
135.0 ± 6.1 (17.4)
138.9 ± 8.8 (20.7)
1
consisted of dipping fruits for ∼5 s, ∼2 weeks after full bloom, into
an aqueous solution of each urea at 10 or 25 ppm. The solutions were
prepared by first dissolving the corresponding urea (100 mg) in a 3:2
mixture of 1-methyl-2-pyrrolidone/DMSO (20 mL), and then this
solution was slowly added with vigorous stirring to a volume of water
adequate to obtain the urea concentration (w/v) used for the treatments.
Between 100 and 120 uniform fruits of three different vines were used
in each treatment. All treatments were effected in two consecutive days.
Control fruits were also dipped for ∼5 s in an aqueous solution of a
2
2
2
2
2
2
2
b (25)
c (10)
c (25)
d (10)
d (25)
e (10)
e (25)
2f (10)
2f (25)
2g (10)
3
:2 mixture of 1-methyl-2-pyrrolidone/DMSO (0.2% v/v).
The treated and control fruits were harvested in the second week of
2
2
2
2
g (25)
h (10)
h (25)
i (10)
i (25)
October, ∼140 days after the treatment, and their weight, diameter,
length, structure (proportion among outer and inner pericarp and core),
flesh firmness, total titratable acids, number of seeds, dry matter of
the fruits, and content of soluble solids were measured paralleling the
methodology previously followed by other authors on related studies
with CPPU (5, 17). All of the fruits from each treatment were used to
determine the final fresh weight and to estimate fruit shape (calculating
length/average diameter and maximum/minimum diameter ratios and
by counting the number of fruits having a protruding distal end). The
rest of the properties were determined for only fruits in those
experiments that produced a significant increment of average fruit
weight with respect to the control. Twenty-five fruits were randomly
selected from each treatment and used to estimate the average internal
structure by measuring, on the cross-sectional area, the maximum and
minimum diameters of the inner pericarp and core and weighing the
core. The same fruits were used to examine the number of seeds visible
on the cut surface, to estimate the seed content, and to measure the
total soluble solids content, expressed as °Brix, using a hand refrac-
tometer. Fifteen fruits per treatment were oven-dried at 105 °C to
constant weight for the determination of the percentage of dry matter
of the fruit. Total titratable acidity was determined by titrating a known
volume of fruit juice with 0.1 N NaOH to the end point of pH 8.1, and
the results were expressed as percentage of citric acid. Fruit firmness
was measured at harvest on two pared sides of each fruit (10
measurements/treatment) using a hand-held penetrometer with an 8-mm-
diameter plunger.
2
a
Values are fruit weight at harvest ± standard deviation. Values in parentheses
represent the percentage of fruit weight with respect to control, calculated by (fwt
fwc)/fwc × 100, where fwt ) fresh weight of treated fruit and fwc ) fresh weight
−
of control
resolution mass spectra. A complete assignment of the spec-
troscopic data for all of them is given in Tables 6, 7, and 8 of
the Supporting Information.
Effect of Fluorinated Urea Treatments on Fruit Growth.
The fruits treated with TDZ and most of the fluorinated analogue
ureas showed a rapid increase in diameter such that differences
in growth with respect to control began to be clearly visible
after the first 2 weeks. Those treatment differences observed
after 2 weeks were still present at harvest (Table 1). As may
be observed, most of the urea treatments produced, to more or
less extent, an increase in fresh fruit weight with respect to the
control. The only exceptions were the ureas 2g and 2o, which
even at the highest concentration showed a significantly
antagonist effect on the fruit weight. Interestingly, some of the
fluorinated ureas produced a larger increase in weight than TDZ,
the effect produced by 2j and 2q at 10 and 25 ppm, respectively,
being particularly notable.
Statistical Analysis. Results were processed by an analysis of
variance (ANOVA), and statistical significance was determined by
Student’s test. Statistical analyses were performed with the software
package SPSS 10.0.6 for Windows obtained from SPSS Espa n˜ a,
Madrid, Spain (1999).
It is interesting to note that, as deduced from the data given
in Table 1, there seems to be a different dose-response for
some of the fluorinated ureas. Thus, whereas ureas 2a, 2b, 2d,
2
f, 2h, 2k, 2m, 2p, 2q, and 2r are all more active at 25 ppm
RESULTS AND DISCUSSION
than at 10 ppm, ureas 2c, 2e, 2i, 2j, 2l, and 2n are less active
at 25 ppm than at 10 ppm. This is not particularly surprising in
view of the results previously obtained in cytokinin activity
studies of other phenyl ureas, for which the dose-response
curves showed a characteristic parabolic shape with the optimum
concentration for maximum cytokinin activity varying substan-
tially over a wide concentration range depending on the urea
substituents (19).
Preparation of Fluorinated Ureas 2a-2r. 1-(Fluorophenyl)-
3
-(1′,2′,3′-thiadiazol-5′-yl)ureas 2a-2r were prepared in high
yield and in a straightforward way by reaction of 1,2,3-
thiadiazole-5-carbonyl azide (5) with the appropriate fluorinated
aniline in refluxing toluene, except in the case of the less
nucleophilic tetra- and pentafluorinated anilines, 6o, 6p, 6q, and
6
r, for which benzene at reflux was used as the solvent (Scheme
1
). In these cases, the use of the higher temperature resulted in
The results obtained in the above experiments show diverse
degrees of growth-promoting activity for the different fluorinated
analogues of TDZ that logically should be attributable to the
pattern of fluorine substitution. Despite being quite different
biological systems, the results obtained in our field experiments
agree relatively well with the conclusions previously obtained
from in vitro studies of phenyl substituent requirements for high
cytokinin activity of phenylureas (20). Thus, a clear cor-
respondence is found between the high efficacy of the 3,5-
difluorophenyl urea 2j, the most active at 10 ppm, and the in
lower yields, as a consequence of the formation of substantial
amounts of symmetric 1,3-bis(1,2,3-thiadiazol-5-yl)urea. The
carbonyl azide (5) has been previously described in the literature
(18) and may be prepared using conventional procedures from
1
,2,3-thiadiazole-5-carboxylic acid (3). First, 3 is transformed
into the corresponding acid chloride 4 by treatment with thionyl
chloride, which is then reacted at room temperature with sodium
azide in aqueous acetone. All of the ureas prepared were
1
13
19
confirmed by H, C, and F NMR, IR, and high- and low-

Effect of Phenyl-fluorinated Ureas on Kiwifruit
J. Agric. Food Chem., Vol. 52, No. 15, 2004 4679
subset of nine ureas (2a, 2c, 2h, 2i, 2l, 2m, 2n, 2o, and 2q), for
which a nonlinear regression analysis gave the eq 1,
Table 2. Data for Compounds 2a−2r
fluorine
substitution
pattern
TLC
log P
A ) -7.057 (( 0.848) + 9.614 (( 1.081) TLC log P -
1
0
a
ΣFb
SCSNH1a
SCSNH3a
A10c
urea
2
3
.128 (( 0.340) (TLC log P)
2
a
TDZ
2-F
3-F
4-F
2,3-F2
2,4-F2
2,5-F2
2,6-F2
1.52
1.57
1.65
1.57
1.67
1.59
1.72
1.28
1.72
1.82
1.72
1.37
1.80
1.37
1.91
1.52
1.52
1.69
0.00
0.54
0.42
0.43
0.96
0.97
0.96
1.08
0.85
0.84
1.39
1.50
1.39
1.51
1.81
1.93
1.92
2.34
0.00
−0.26
0.23
0.00
0.15
0.10
0.04
0.24
0.22
0.22
0.45
0.17
0.28
0.25
0.52
0.18
0.48
0.25
0.54
0.57
0.62
0.306
0.158
0.298
0.046
0.375
0.035
0.010
0.100
0.254
0.500
0.047
0.285
0.059
0.226
−0.080
0.146
0.336
0.174
2
b
2
(
n ) 9, r ) 0.949, s ) 0.036, F ) 56) (1)
2
c
2
d
0.03
where A10 expresses the activity at 10 ppm [A10 ) (fwt - fwc)/
fwc, see Table 2]. The remaining nine ureas (2b, 2d, 2e, 2f,
2g, 2j, 2k, 2p, and 2r) form a group with intermediate or high
hydrophobicity that does not correlate with activity.
Figure 1 shows the set of data points relating TLC log P
and activity values given in Table 2 and illustrates the parabolic
relationship of the activity to TLC log P for the first subgroup
of ureas mentioned above, showing for them an optimum
hydrophobicity close to TLC log P ) 1.53.
The lack of a good correlation between TLC log P and
activity for the entire group of ureas, and particularly the fact
that two ureas with nearly identical hydrophobicities, for
example 2p versus 2q or 2a, produced a very different effect
on fruit weight, suggests that other factors besides overall
hydrophobicity may also influence the activity. In this respect,
we noted an interesting correlation between the activity of the
whole library of ureas with the Swain-Lupton substituent
parameter F (see ΣF in Table 2) and the substituent-induced
chemical shifts observed for the NH protons of the urea bridge
2
e
−0.03
−0.24
−0.06
−0.32
0.24
2
f
2
g
2
h
2
i
3,4-F2
3,5-F2
2
j
0.44
2
k
2,3,4-F3
2,3,6-F3
2,4,5-F3
2,4,6-F3
2,3,4,5-F4
2,3,4,6-F4
2,3,5,6-F5
2,3,4,5,6-F5
−0.05
−0.10
−0.08
−0.40
0.14
−0.14
0.13
0.10
2
l
2
m
2
n
2
o
2
p
2
q
2r
a
TLC log P, SCSNH1, and SCSNH3 have estimated uncertainties of <±3%, based
on separate measurements. Swain−Lupton F values used are scaled by aromatic
ring position (ortho, meta, para) following the procedure described in Williams, S.
G.; Norrington, F. E. J. Am. Chem. Soc. 1976, 98, 508. A10 ) (fwt − fwc)/fwc (fwt
b
c
)
fresh weight of treated fruit; fwc ) fresh weight of control) at 10 ppm.
(
SCSNH1 and SCSNH3, Table 2) as shown by eq 2,
A ) 0.244 (( 0.050) + 0.416 (( 0.114) SCS +
NH1
vitro activity of the 3,5-difluorophenyl analogue of the N-oxide
of CPPU (21). As with 2j, an increment in activity at 10 ppm
is observed in the less fluorinated ureas by meta fluorination at
the phenyl ring, for example, 2b versus 2e, 2d versus 2i, or 2h
versus 2l, although this effect disappears or even inverts with
increasing fluorination, for example, 2m versus 2o. The effect
of para substitution by fluorine is also significant, generally
resulting in a diminution of activity, for example, 2a versus
1
0
1
.078 (( 0.245) SCSNH3 - 0.319 (( 0.074) ΣF
â* ) 0.587 â* ) 1.348 â* ) -1.301 (2)
n ) 18, r ) 0.664, s ) 0.096, F ) 9)
2
(
2
d, 2b versus 2f, or 2e versus 2k, which should be in accordance
which may be considerably improved if the values of four ureas
are excluded from the analysis (ureas 2d, 2e, 2g, and 2h, the
data points that fit worst to the correlation line) as shown by
eq 3
with the reduced cytokinin activity observed for the structurally
related 1-(2-chloro-1-oxypyridin-4-yl)-3-(4-fluorophenyl)urea
with respect to the parent compound in the chlorophyll retention
bioassay (22). Ortho fluorination of the phenyl ring does not
produce a uniform effect on activity, but, in general, the presence
of the fluorine atom at C-2 and/or C-6 does not seem to have
a particularly detrimental effect on activity. Even some of the
ortho fluorinated ureas produce a remarkable increase in activity
with respect to the parent TDZ, as the symmetrically fluorinated
urea 2q, by far, the most active of all these ureas at 25 ppm.
The great activity of this tetrafluorinated urea shows that the
steric effects produced by the fluorine atoms, which could also
affect the conformational disposition between the ureido and
phenyl moieties, do not seem to influence very negatively the
interaction of the fluorinated phenyl moiety with the specific
local receptor site. In fact, and with the exception of only urea
A ) 0.286 (( 0.031) + 0.346 (( 0.065) SCS +
NH1
1
0
1
.193 (( 0.147) SCSNH3 - 0.369 (( 0.043) ΣF (3)
â* ) 0.523 â* ) 1.568 â* ) -1.632
n ) 14, r ) 0.906, s ) 0.052, F ) 32)
2
(
and Figure 2. [Results from a parallel study have shown that
all of the ureas exist in the solvent used for recording their NMR
data (DMSO-d6 solutions) as monomers in the trans-trans
conformation, which is strongly stabilized by formation of a
three-center bond between the ureido protons (NH) and the
oxygen atom of the sulfoxide moiety. No significant variations
are observed in the chemical shifts of the NH hydrogens with
the concentration of the fluorinated urea (at least over a 3-fold
concentration range). It is interesting to note that there is a good
linear dependence between the chemical shift of the ureido
hydrogens and both F and R substituent constants (Swain-
Lupton model). These results will be published elsewhere.]
Because the ΣF factor measures the field-inductive effects
of the fluorine atoms on the phenyl moiety of each urea, both
equations seem to reveal the importance of the electronic
interactions of this region of the urea framework with its specific
receptor site, an aspect that could be more significant to their
2o, all of the polyfluorinated ureas produce an increase in fruit
weight with respect to the control.
We have estimated the hydrophobicity of ureas 2a-2r by
determining the corresponding TLC log P values using an
adaptation of the procedure used by Henrie for related ureas
(22). These values are given in Table 2. As can be seen, the
degree and pattern of fluorine substitution of the benzene ring
have a significant influence in the overall hydrophobicity of
these ureas. There does not seem to be a good-quality correlation
between the overall hydrophobicity and the growth-promoting
activity for the whole group of fluorinated ureas. However, there
is a good correlation between hydrophobicity and activity for a

4680 J. Agric. Food Chem., Vol. 52, No. 15, 2004
Abad et al.
Figure 3. Effect of fruit size distribution in response to phenyl-fluorinated
urea treatments
Figure 1. Parabolic relationship of growth-promoting activity of fluorinated
analogues of TDZ to TLC log P expressed by eq 1. Squares represent
data points not included in the quadratic curve-of-best-fit drawn.
Effects of Fluorinated Urea Treatments on Fruit Quality
Properties. A more detailed evaluation of the effects caused
by the urea treatments on some commercially important fruit
properties was effected on a reduced selection of experiments.
In particular, the fruits harvested from control experiments and
treatments with TDZ (2a) and ureas 2b, 2e, 2j, and 2q were
selected for this evaluation. Additionally to the increase in the
average fruit weight, the treatment with the more active ureas
resulted in a greater uniformity and size grade increase for the
fruits obtained. As graphically expressed in Figure 3, the
percentage of large size fruits (weight g 135 g), medium size
fruits (110 e weight e 135 g), and small size fruits (weight e
110 g) changed substantially from control to TDZ-treated fruits
and from these to the rest of fluorinated urea-treated fruits. In
the latter case, few fruits of small size were obtained, and most
of the fruits were of the largest size, the results obtained with
Figure 2. Plot of A10 versus a linear combination of SCSNH1, SCSNH3
and Swain−Lupton F constant (A10calcd as expressed by eq 3). Squares
represent data points not included in the line-of-best-fit drawn.
,
2
b and 2q at 25 ppm and with 2e and 2j at 10 ppm being
particularly relevant.
activity than the global transport process measured by the overall
hydrophobicity. On the other hand, the dependence of the
activity on the SCSs may be associated with the capacity of
the ureido N-H protons of the urea bridge to participate in
hydrogen-bonding interactions, a factor that has been suggested
to play an important role in the cytokinin activity of N-phenyl-
and N-pyridylureas and related carbamates (23). The consider-
ation of these two factors leads to the conclusion that two of
the main effects produced by fluorination of the benzene ring,
for example, changes in the acidity of the ureido hydrogens
and alteration of electron donor/acceptor capacity of the phenyl
ring, are important for the cytokinin-like activity of these
fluorinated ureas. Thus, an enhancement of acidity of the ureido
protons results in an increase in activity, whereas a lowering of
the phenyl ring electronic density leads to a lesser activity. The
highest activity should result from a subtle balance of both
effects.
The above conclusion will explain the elevated activity of
tetrafluorinated urea 2q as opposed to the rest of the highly
fluorinated ureas, because the relatively large inductive-field
effect associated with the polyfluorinated phenyl ring is
compensated by the acidity of the ureido protons, particularly
the N3-H proton, to which should probably be added a very
favorable overall hydrophobicity for an efficient transport to
the receptor. On the other hand, the urea 2j, one of the most
hydrophobic fluorinated ureas, has an adequate combination of
the inductive effects associated with the fluorine atoms and
acidity of the ureido N-H that results in a very high activity.
As a consequence of the increase in size, the treatments with
these ureas also resulted in an increase in the length and diameter
of the fruits (Table 3). Although a slight elongation of the fruits
treated with the more active ureas was observed, as shown by
the relationship between the length and average diameter, in
general, the global fruits shape was not affected very negatively.
It is interesting to note that a modification of the shape of the
fruits treated with TDZ at 10 ppm was observed, with more
rounded fruits being obtained in this experiment. This result
contrasts with that obtained at the higher concentration; the
treatment with TDZ at 25 ppm did not cause any change in the
relative diameters and lengths. Previous studies with TDZ and
CPPU showed that the effect of the treatments with these ureas
on the relative diameter and length of the fruits is not regular;
in some cases CPPU or TDZ treatments caused more fruit
growth in the diameter than in length (5), whereas in other cases
the treatment did not cause any significant change in the relative
diameters and lengths (24). As previously noted, an increase in
the percentage of fruits having a protruding distal end was
observed for all of the treated fruits, an effect that was
appreciably more marked in the fruits treated with the more
active ureas.
The effect of treatments on fruit internal structure is also
evident by comparison of the data given in Table 4. As can be
seen from these data, all of the treatments caused a similar
modification of the relative proportion of the fruit tissues that
led to fruits with proportionally smaller cores than untreated
fruits. These results contrast with those previously obtained with

Effect of Phenyl-fluorinated Ureas on Kiwifruit
J. Agric. Food Chem., Vol. 52, No. 15, 2004 4681
Table 3. Effects of Phenyl-fluorinated Urea Treatments on Fruit Size and Shape at Harvesta
length
(mm)
max diameter
(mm)
min diameter
(mm)
length/av
diameter
protruding distal
end (% fruits)
urea (ppm)
Dmax/Dmin
control (0)
TDZ (10)
TDZ (25)
66.7 g
67.4 g
58.6 e
62.9 cd
61.6 a
61.8 d
66.0 b
64.9 bc
61.9 d
66.3 b
64.9 bc
65.0 bc
66.8 b
52.8 e
1.11 ab
1.10 b
1.10 b
1.13 ab
1.14 ab
1.15 ab
1.12 ab
1.11 ab
1.16 a
1.20 c
1.12 d
1.20 c
1.20 c
6 d
26 c
28 c
50 b
72 ab
52 b
36 c
84 a
52 b
32 c
40 c
57.4 abcd
56.2 bcd
55.0 de
57.8 abc
56.7 abcd
55.3 d
56.8 ab
55.9 cd
58.4 ab
59.1 a
70.8 ef
70.2 fg
74.2 bcd
74.2 bcd
73.1 cdef
76.8 ab
75.4 cd
75.4 bc
79.4 a
2
b (10)
b (25)
e (10)
e (25)
j (10)
j (25)
q (10)
q (25)
2
2
1.20 c
1.22 bc
1.25 ab
1.23 abc
1.25 ab
1.22 bc
1.22 bc
2
2
2
2
1.11 ab
1.11 ab
2
a
In each column, means followed by the same letter are not significantly different at P e 0.05.
Table 4. Effects of Phenyl-fluorinated Urea Treatments on Fruit Structure at Harvesta
Dmax of
Dmin of
inner pericarp +
core/Dmax of fruit
inner pericarp +
core/Dmin of fruit
Dmax of core/
Dmax of fruit
Dmin of core/
Dmin of fruit
core fw/
fruit fw (%)
urea (ppm)
seed no.
control (0)
TDZ (10)
TDZ (25)
0.64 ab
0.63 b
0.65 ab
0.66 ab
0.68 a
0.66 ab
0.67 ab
0.64 ab
0.64 ab
0.66 a
0.58 a
0.34 ab
0.30 b
0.30 b
0.35 ab
0.36 a
0.35 ab
0.34 ab
0.34 ab
0.33 ab
0.33 ab
0.31 ab
0.24 a
0.18 b
0.20 b
0.20 b
0.19 b
0.19 b
0.20 b
0.18 b
0.18 b
0.19 b
0.19 b
8.7 a
5.0 c
4.9 c
6.7 b
6.0 bc
5.6 bc
5.6 bc
5.6 bc
5.7 bc
5.3 c
50.6 ab
43.2 b
43.4 b
50.6 ab
43.4 b
43.8 b
54.5 a
46.8 ab
50.8 ab
43.2 b
43.2 b
0. 52 c
0.55 abc
0.56 abc
0.52 c
0.53 bc
0.57 ab
0.53 bc
0.53 bc
0.53 bc
0.53 bc
2
b (10)
b (25)
e (10)
e (25)
j (10)
j (25)
q (10)
q (25)
2
2
2
2
2
2
2
0.64 ab
4.9 c
a
In each column, means followed by the same letter are not significantly different at P e 0.05.
Table 5. Changes in Flesh Firmness, Soluble Carbohydrates, and Total Titratable Acids at Harvest and after 13 Days at 25 °C As Affected
a
Phenyl-fluorinated Urea Treatments
total titratable acids
flesh firmness (kgf)
3 days after
soluble carbohydrates (°Brix)
(g of citric acid/L of juice)
1
13 days after
13 days after
dry matter
urea (ppm)
at harvest
harvest
at harvest
harvest
at harvest
harvest
content (% fw)
control (0)
TDZ (10)
TDZ (25)
7.6 a
5.7 cde
4.7 e
4.2 c
6.2 f
9.7 b
13.1 a
12.5 a
8.4 c
8.2 c
8.6 bc
9.1 b
8.0 c
8.5 c
12.7 a
12.3 a
17.2 b
15.0 f
14.9 f
15.9 d
15.9 d
15.8 d
15.5 e
16.5 c
16.5 c
17.6 a
14.9 f
16.3 a
14.3 e
14.7 d
15.4 c
15.9 b
15.3 c
15.1 c
14.5 h
15.8 b
15.7 b
13.9 f
15.9 a
1.5 d
1.5 d
5.7 ab
6.2 a
5.0 bc
4.2 c
5.5 abc
4.7 bc
1.6 d
1.8 d
7.4 de
7.7 cde
8.1 abc
8.3 ab
8.4 a
8.3 ab
8.2 abc
7.8 bcd
7.2 e
12.5 cd
12.9 b
12.8 bc
13.0 b
13.0 b
12.0 efg
12.1 ef
12.3 de
11.9 fg
11.7 g
2
b (10)
b (25)
e(10)
e (5)
j (10)
j (25)
q (10)
q (25)
6.7 abc
6.6 abc
6.8 ab
5.7 cde
6.1 bcd
7.0 ab
6.6 abc
5.1 de
2
2
2
2
2
2
2
7.1 e
a
In each column, means followed by the same letter are not significantly different at P e 0.05.
TDZ, which caused an increase in the size of all the tissues of
the fruits without changing their relative proportions (5). An
important modification of the shape of the core was also
observed in all of the treated fruits, being appreciably flatter
than in the control fruits (see Figure 4 of the Supporting
Information). No significant variation in the number of seeds
was observed between the fruits of different treatments, nor with
respect to control. Similar observations have also been made
in previous studies with TDZ and CPPU (5, 17).
treatments advance fruit ripening with respect to untreated fruits
more or less proportionally to the increase in fruit weight (Table
5). This observation is also in agreement with the results
previously obtained on kiwifruit treatments with TDZ and
CPPU. However, although the more active ureas produced a
more rapid fruit ripening, the effect is in general less pronounced
for the fluorinated ureas than for TDZ. A very interesting
observation deduced from the data referring to the postharvest
period is the substantially slower ripening of the fruits treated
with some of the more active fluorinated ureas with respect to
both control and TDZ-treated fruits. In fact, of all the ureas
studied, only the polyfluorinated urea 2q showed a behavior
Fruit ripening at harvest was affected by all of the treatments.
Comparison of the values of flesh firmness and total soluble
solid content of treated and control fruits indicates that the

4682 J. Agric. Food Chem., Vol. 52, No. 15, 2004
Abad et al.
1
similar to that of TDZ. The effect of the treatments on
maturation was also confirmed by the lower total titratable
acidity measured for treated fruits with respect to untreated ones.
Supporting Information Available: Copies of H and 13C
NMR spectra and mass spectra of compounds 2b-2r; tables
1
13
19
with completed H, C, and F NMR chemical shifts and
coupling constants assignments (Tables 6, 7, and 8, respec-
tively); photograph of representative longitudinal and equatorial
cross sections of untreated and treated kiwifruits (Figure 4).
This material is available free of charge via the Internet at http://
pubs.acs.org.
Finally, the effect of the treatments with the fluorinated ureas
on dry matter content at harvest was also determined (Table
5). In concordance with the results previously described for TDZ
and CPPU treatments, all of the fluorinated ureas also produced
an important decrease in the percentage of dry matter of fruit
at harvest that was not very different from that produced by
TDZ (2). [The data set corresponding to the different measured
or calculated agronomical variables (length, maximum diameter,
minimum diameter, Dmax/Dmin, length/average diameter, percent
of fruits with protruding distal end, Dmax of inner pericarp +
core/Dmax of fruit, Dmin of inner pericarp + core/Dmin of fruit,
Dmax of core/Dmax of fruit, Dmin of core/Dmax of fruit, core fw/
fruit fw, flesh firmness, soluble carbohydrates, total titratable
acids, and dry matter content) was also statistically analyzed
with principal component analysis (PCA), which revealed that
the variance in this data set is explained by a three-component
model to 92%. According to this analysis the agronomical
parameters corresponding to the kiwifruits treated with the more
active fluorinated ureas (2b, 2e, 2j, and 2q) are statistically
homogeneous, different from those corresponding to TDZ-
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(
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(
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4
(
(
6
From a potential profitability point of view, the great increase
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Received for review January 15, 2004. Revised manuscript received
May 12, 2004. Accepted May 12, 2004. We thank the Direcci o´ n General
de Ense n˜ anza Superior e Investigaci o´ n Cient ´ı fica (Grants 1FD-97-0705
and BQU2002-00272) for financial support. We also thank Protagric
S.A., Valencia, Spain, for financial support of our research.
(
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JF049921+