Photochemistry and Photobiology, 2012, 88 905
analogs, to better understand why octocrylene causes photo-
contact allergy. We also aimed at studying octocrylene’s ability
to protect amino acid analogs from photodegradation, i.e. to
mimic its protective ability of proteins.
Preparative HPLC was performed using a Gilson pump model 305,
a Gilson UV ⁄ VIS detector model 119 and a Zorbax Semi-Preparative
column (250 · 9.4 mm, 5 lm particles; Agilent Technologies), the flow
)1
rate was 13.36 mL min and the compounds were monitored at
2
30 nm. Aliquots of 100 lL were injected onto the column and eluted
with acetonitrile ⁄ water 9:1.
1
13
3 3
H and C NMR spectra were recorded in CDCl or CD CN on a
MATERIALS AND METHODS
JEOL eclipse + 400 MHz spectrometer at 400 and 100 MHz, respec-
tively. Chemical shifts (d) are reported in ppm with the solvent residual
Chemicals. Reagents were obtained from commercial suppliers
and used without further purification. Benzylamine was obtained
from Fluka, Sigma–Aldrich Chemie (Steinheim, Germany) and
benzophenone from Merck–Schuchardt (Hohenbrunn, Germany).
2-Ethylhexyl-2-cyano-3,3-diphenylacrylate (octocrylene), 3-methylin-
dole, 4-propylphenol and 1-octanethiol were purchased from Sigma–
Aldrich Chemie. Argon (99.99%) and synthetic air (78% N
were used as received from AGA (Sweden).
Instrumentation and modes of analyses. Column chromatographic
1
peaks as internal standard: CHCl
3
d 7.26 ( H NMR), CDCl
3
d 77.0
1
3
1
13
(
NMR). H and C NMR spectra were assigned using C distortion-
C NMR), CH CN d 1.94 ( H NMR) and CD CN d 118.2 ( C
3 3
1 13 13
1
1
less enhancement by polarization transfer (DEPT), H- H correlation
1 1
spectroscopy (COSY), H- H total correlation spectroscopy (TOCSY),
1
13
2
, 22% O
2
)
H- C heteronuclear multiple-quantum correlation spectroscopy
1 13
(HMQC) and H- C heteronuclear multiple-bond correlation spec-
troscopy (HMBC).
separations were performed using Merck silica gel Geduran Si 60
(0.063–0.200 mm) and Sigma–Aldrich hexane mixture of isomers (bp
Photolysis of octocrylene in EtOH. Photolysis was performed on
370 mL of a 10 mM solution of octocrylene in EtOH, continuously
saturated with air by bubbling with synthetic air through a sintered
glass frit in the reaction mixture reservoir. The mixture was illuminated
for 6 h and samples of approximately 4 mL were withdrawn from the
photoreactor at 0.25, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 h and analyzed with
HPLC ⁄ MS. Each sample was diluted with acetonitrile (1:20) before
analysis with HPLC ⁄ MS. Octocrylene and ethyl 2-cyano-3,3-diphenyl
acrylate were quantified with HPLC ⁄ UV at 280 nm by using standard
curves (see Supporting information).
Photolysis of octocrylene in EtOH in the absence of oxygen. Photo-
lysis was performed on 370 mL of a 10 mM solution of octocrylene in
EtOH. Instead of synthetic air, argon was bubbled through the mixture
during the experiment. The mixture was illuminated for 6 h and
samples of approximately 4 mL were withdrawn from the photoreac-
tor at 0.00, 0.25, 0.50, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 h and analyzed with
HPLC ⁄ MS. Each sample was diluted with acetonitrile (1:20) before
analysis with HPLC ⁄ MS. Ethyl 2-cyano-3,3-diphenyl acrylate was
quantified with HPLC ⁄ UV at 280 nm by using a standard curve (see
Supporting information).
Fractionation of the mixture obtained from 6 h photolysis of
octocrylene in EtOH. The reaction mixture from the 6 h photolysis
experiment of octocrylene in EtOH was concentrated under reduced
pressure and fractionated by semipreparative HPLC. The main
compound formed in the photolysis experiment was ethyl 2-cyano-
3,3-diphenyl acrylate. It was isolated as a white solid and the obtained
NMR spectra were in accordance with reference (14). Three other,
much smaller fractions, contained compounds that were possible to
identify: 3,3-diphenylacrylonitrile, benzophenone and 2-ethylhexyl 2-
68–70ꢁC). Photolysis reactions were performed in a falling film
photoreactor, according to Professor de Meijere (12) with forced
liquid circulation, purchased from NORMAG Labor- und Prozess-
technik. The photoreactor was equipped with a medium pressure
mercury UV lamp (700 W, Heraeus, TQ 718, Z4 doped) as
irradiation source. The total radiant power of the lamp in the
wavelength interval 200–600 nm is 389 W. Both the lamp and the
reaction mixture were cooled with water, which kept the temperature
of the reaction mixture at 20–25ꢁC during the experiments. Argon or
synthetic air was continuously bubbled through the sample and
allowed to pass through the reaction zone. For a more detailed
description of the photoreactor equipment see Supporting Informa-
tion.
TM
Photolysis experiments were also performed in a Solarlux
solar
simulation system from EYE Lighting International ⁄ Iwasaki Electric
that generates similar spectral distribution as the sun. Light source:
TM
EYE Solarlux
150R lamp with AM1.5 spectral filter. Solar spectral
match is class B according to IEC standards; spectral match 0.2 and
.8 in the intervals 300–350 and 350–400 nm, respectively. The distance
0
2
between the lamps and the quartz glass reaction vessel (4 cm ) was
0 cm and the irradiation power controller was set on 11. This set up
4
)
2
gives an intensity of 1033 W m , which corresponds to approximately
one sun. The temperature of the reaction mixture was 43–45ꢁC during
the experiment. A more detailed description of the solar simulation
system is available on the homepage of the EYE Lighting Interna-
tional ⁄ Iwasaki Electric of North America (13).
GC ⁄ MS analyses were performed using electron impact ionization
ethoxy-4-phenylquinoline-3-carboxylate.
3,3-Diphenylacrylonitrile
(70 eV) on a Hewlett-Packard model 5973 mass spectrometer (scanned
1
m ⁄ z 50–500), connected to a gas chromatograph (Hewlett-Packard
model 6890). The GC was equipped with an on-column inlet and an
HP-5MSI fused silica capillary column (30 · 0.25 mm, 0.25 lm film
was isolated and the obtained H NMR was in agreement with the
literature (14,15). The formation of benzophenone was verified with a
standard. Characterization data for 2-ethylhexyl 2-ethoxy-4-phenyl-
1
H
thickness). Helium was used as carrier gas, the flow rate was
quinoline-3-carboxylate:
J = 8.4 Hz, H
.52–7.43 (m, 4H, H
dd, 1H, J = 8.4 Hz, J
11), 3.98–3.90 (m, 2H, H14), 1.44 (t, 3H, J = 7.0 Hz, H12), 1.41–1.34
NMR (CDCl
= 8.4 Hz, J
and H24-H25), 7.41–7.36 (m, 2H, H23), 7.29
= 6.9 Hz, H ), 4.61 (q, 2H, J = 7.0 Hz,
3
)
d: 7.87 (d, 1H,
.2 mL min) , and the injection volume was 1 lL. The column
1
9
), 7.63 (dd, 1H, J
1
2
= 6.9 Hz, H ),
8
1
7
(
6
temperature was 100ꢁC at injection and raised to 200ꢁC at a rate of
)
1
)1
5
ꢁC min , then raised from 200 to 270ꢁC at a rate of 15ꢁC min , and
1
2
7
finally held at 270ꢁC for 20 min.
H
HPLC ⁄ MS analyses were performed using electrospray ionization
on a Hewlett-Packard 1100 HPLC ⁄ MS. The system included a vacuum
degasser, a binary pump, an autoinjector, a column thermostat, a
diode array detector and a single quadrupole mass spectrometer. The
electrospray interface was used with the following spray chamber
settings: nebuliser pressure, 35 psig; capillary voltage, 3000 V; drying
(m, 1H, H15), 1.29–1.13 (m, 8H, H16-H18 and H20), 0.87 (t, 3H,
13
3
J = 7.1 Hz, H19), 0.78 (t, 3H, J = 7.4 Hz, H21). C NMR (CDCl ) d:
1
1
1
66.9 (C13), 157.8 (C
29.4 (C23), 128.6 (C25), 128.4 (C24), 127.5 (C
23.8 (C ), 119.6 (C
2
), 148.1 (C
4
), 146.7 (C10), 135.4 (C12), 130.2 (C
8
),
),
9
), 126.7 (C ), 124.4 (C
6
7
5
3
), 67.5 (C14), 62.4 (C11), 38.6 (C15), 30.2 (C16), 28.9
(C17), 23.5 (C20), 23.0 (C18), 14.6 (C12), 14.2 (C19), 10.9 (C21). High
resolution mass spectrum (ESI) m ⁄ z calculated for C26H31NO + H,
3
406.2382; found, 406.2377.
Photolysis of octocrylene in EtOH using the solar simulation system.
Photolysis was performed on a 10 mM solution of octocrylene in
EtOH in a 1.5 mL quartz cuvette. The mixture was illuminated for
30 h and samples of approximately 0.1 mL were withdrawn from the
reaction vessel at 0.00, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 24 and 30 h and
)
1
gas temperature, 350ꢁC; and drying gas flow rate, 12 L min . For
mass spectral analysis, the mass spectrometer was used in the scan
mode detecting ions with m ⁄ z ranging from 50 to 1000. Mass spectral
analysis was performed in positive ionization mode with fragmentor
voltage of 70 V. A Zorbax SB-C18 column (150 · 2.1 mm, 5 lm
particles; Agilent Technologies) was used and the column temperature
was set to 40ꢁC. Mobile phase A consisted of 0.1% formic acid in milli-
Q water, and mobile phase B consisted of 0.1% formic acid in
acetonitrile. Aliquots of 5 lL were injected onto the column and eluted
analyzed with HPLC ⁄ MS. The samples were diluted with acetonitrile
(
(
1:20) before analysis with HPLC ⁄ MS using selected ion monitoring
SIM) to detect ions with the m ⁄ z of 278.0 (see Supporting
)1
with a gradient flow of 0.40 mL min . A linear gradient from 10% to
Information). To verify that ethyl 2-cyano-3,3-diphenyl acrylate was
formed the 30 h sample was spiked with a synthetic standard (see
Supporting Information).
1
1
00% B in 20 min was followed by 10 min of isocratic eluation at
00% B. The column was equilibrated with 10% B for 10 min between
each run.