Amino acid-sensitive reagents with coumarin moiety for latent prints examination

Article abstract of DOI:10.1007/s00706-018-2260-5

Abstract: New ninhydrin derivatives were designed for the development of latent fingerprints on paper surfaces. The target compounds combine the selectivity of an amino acid-sensitive reagent with the variability of spectral characteristics of a fluorescent probe. These ninhydrin analogues, 2,2-dihydroxy-5-(2-oxo-2H-chromen-4-yloxy)-2H-indane-1,3-diones, prepared by multistep synthesis show enhanced fluorogenic properties compared with the commonly used ninhydrin. These types of derivatives can be potentially used for development of the latent prints on the dark surfaces, because their ninhydrin reaction products provide fluorescent prints under the UV light. The prints developed using these compounds are stable, visible and do not vanish from paper for a relatively long time (5?months). Graphical abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s00706-018-2260-5

Monatshefte für Chemie - Chemical Monthly
https://doi.org/10.1007/s00706-018-2260-5(0123456789(). -, vo Vl
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ORIGINAL PAPER
Amino acid-sensitive reagents with coumarin moiety for latent prints
examination
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Jan Gaspar Zuzana Nemethova Hana Janekova Anton Gaplovsky Henrieta Stankovicova
Received: 5 April 2018 / Accepted: 19 June 2018
Ó Springer-Verlag GmbH Austria, part of Springer Nature 2018
Abstract
New ninhydrin derivatives were designed for the development of latent fingerprints on paper surfaces. The target com-
pounds combine the selectivity of an amino acid-sensitive reagent with the variability of spectral characteristics of a
fluorescent probe. These ninhydrin analogues, 2,2-dihydroxy-5-(2-oxo-2H-chromen-4-yloxy)-2H-indane-1,3-diones, pre-
pared by multistep synthesis show enhanced fluorogenic properties compared with the commonly used ninhydrin. These
types of derivatives can be potentially used for development of the latent prints on the dark surfaces, because their
ninhydrin reaction products provide fluorescent prints under the UV light. The prints developed using these compounds are
stable, visible and do not vanish from paper for a relatively long time (5 months).
Graphical abstract
Keywords Amino acids Á Dual fingerprint reagent Á Heterocycles Á Ninhydrin Á Nucleophilic substitutions
Introduction
Ninhydrin (2,2-dihydroxyindane-1,3-dione, 1) has been
widely used in many fields of chemistry, biochemistry, and
forensic science since its synthesis by Ruhemann [1]. The
broad application of 1 (Fig. 1) results from its reactivity
Electronic supplementary material The online version of this
towards a plethora of substrates. The most extensively
studied and publicised have become the colour-forming
reactions with amines and amino acids leading to the non-
fluorescent Ruhemann’s purple (2) [2–6].
article (https://doi.org/10.1007/s00706-018-2260-5) contains
supplementary material, which is available to authorized
users.
ˇ
´
& Henrieta Stankovicova
henrieta.stankovicova@uniba.sk
Bodily fluids assembled in latent (invisible) fingerprints
on porous or non-porous surfaces and on a large variety of
materials are the most common type of evidence found at
the crime scenes and the most problematic, whereas they
require the enhancement methods to reach visible and
recordable fingerprints. Of considerable interest are
1
Institute of Chemistry, Faculty of Natural Sciences,
ˇ
Comenius University, Ilkovicova 6, Bratislava 842 15,
Slovakia
2
Institute of Forensic Science, Presidium of the Police Force,
´
Ministry of the Interior of the Slovak Republic, Sklabinska,
Bratislava 35 812 72, Slovakia
123

J. Gašpar et al.
Fig. 2 Structure of 1,8-diazafluoren-9-one (3, DFO) and 1,2-indane-
dione (4)
Fig. 1 Structure of ninhydrin (1) and Ruhemann’s purple (2)
chemical techniques for visualisation of latent prints on
paper and related cellulosic materials, since our society
relies on such materials for official documents, packaging,
and currency printing. The introduction of ninhydrin (1) as
an affordable and easily applicable chemical reagent for
visualisation of the amino acids present in latent finger-
prints on porous surfaces has revolutionised approaches to
forensic examinations [2, 4, 6].
which also produces colourless to faint pink impressions
´
with latent fingerprints (also known as the Joullie’s pink)
that fluoresce in the visible domain [12–14]. As a result,
compound 4 is regarded as the most sensitive of all com-
monly used reagents; however, 1 is the most widely used
due to the cost and intense initial colour [13].
Although fluorescence detection is a common practice in
fingerprint development now, in the available literature
there are not lots of published reports dealing with the idea
of linking ninhydrin (1) and some of the known fluorescent
probes to a single molecule. We report a synthesis of a new
type of ninhydrin analogue which combines the selectivity
of the amino acid-sensitive reagent with the variability of
the spectral characteristics of a fluorescent probe. A cou-
marin skeleton was chosen as the fluorescent probe. Its
derivatives are known for their spectral properties, mainly
the intense fluorescence observed in many derivatives with
appropriate substitution as they are important components
of functional molecules (e.g. probes, sensors, switches, and
molecular devices) [15–17].
Due to their high stability, amino acids are the most
desirable components of latent fingerprints on paper. Since
amino acids have a high affinity for cellulose, the main
component of paper, they do not bleed from paper’s surface
and the concentration in fingerprints does not vary in time
as in the case of uric acid or inorganic salts, for instance.
The main advantage of ninhydrin (1) lies in its ability to
visualise latent fingerprints with low concentration of
amino acids, corresponding to a content of about 250 ng
per print, on paper [3, 6]. The ninhydrin reaction provides a
product with a high molar extinction coefficient under very
mild reaction conditions. The introduction of various sub-
stituents and the extension of the conjugated system of the
ninhydrin skeleton, while preserving the reactivity of cyclic
triketone, cause an increase in molar extinction coefficients
yielding more sensitive reagents and inducing shifts of
absorption maxima, resulting in some variation in the
colour of the Ruhemann’s purple products [3]. However,
fingerprint experts are still trying to resolve the problem of
the lack of contrast and sensitivity observed in particular on
coloured surfaces. The Ruhemann’s purple (2) forms
a coordination complex with a metal salt (e.g. zinc chlo-
ride) which results in a colour change. Additionally, the
complex shows intense fluorescence viewed under argon
laser [7–9]. On reducing the temperature, the intensity of
fluorescence enhances significantly [7].
Despite the fact that more than 90 ninhydrin derivatives
and analogues have been reported in literature [2–5], syn-
thesis of a new type of ninhydrin derivatives with enhanced
fluorogenic and chromogenic properties is still of high
interest.
Results and discussion
Design and synthesis of a novel ninhydrin
analogue
Previously examined approaches concerning modification
of the structure of 1 have not led to any widely applicable
dual ninhydrin fingerprint reagent [2–9]. When proposing
the new reagent structure, it was necessary to fulfil the
requirement of preserving the cyclic triketone part of nin-
hydrin (1) to ensure the reactivity with the amino acids in
latent fingerprints. Having experience with the synthesis
and study of the spectral properties of coumarin (5) and its
derivatives [18–22], we have decided to link these two
substructures into molecule 6 (Fig. 3). In spite of a possible
applicability of the combined moieties, only one report in
literature concerning the combination of coumarin and
An ideal dual fingerprint reagent is expected to produce
both coloured and fluorescent impressions in a single
reaction with latent fingerprint. 1,8-Diazafluoren-9-one (3,
DFO, Fig. 2), undoubtedly the most significant fluorogenic
fingerprint reagent to date, can be considered as a dual
reagent, but the pink colour it produces with latent fin-
gerprints is very faint and insufficient for the detection of
most latent prints. DFO impressions are actually detected
only by their fluorescence [4, 10, 11]. A similar behaviour
is exhibited by a more recent reagent, 1,2-indanedione (4),
123

Amino acid-sensitive reagents with coumarin moiety for latent prints examination
also have a higher sensitivity than the ones only using the
detection of colour change.
A concise, multistep synthesis was designed to afford
new ninhydrin derivatives. The two above-mentioned
moieties were linked through an O-bridge (Scheme 1).
Commercially available 5-methoxyindanone (7) was
dealkylated using AlCl3 to afford the indanone 8 in good
yield [24]. The coumarin substructures suitable for link-
ing with 5-hydroxyindanone (8) were prepared by facile
bromination of 4-hydroxycoumarins 9 with POBr3 to give
4-bromocoumarins 10 in acceptable yields. As coumarins 5
substituted with good leaving groups in position 4 of the
skeleton are very useful substrates for coupling and
nucleophilic substitution reactions [25, 26], we carried out
the nucleophilic reaction of coumarins 9 with indanone 8.
This reaction in dry acetonitrile in the presence of K2CO3
under reflux led to coumarin derivatives 10 in 67–71%
yields. The isolation of products was simple due to their
precipitation after the addition of ice to the reaction mix-
tures. All other components of the reaction mixtures
remained in the acetonitrile/water mixture. Simple purifi-
cation of 4-(1-oxo-2,3-dihydro-1H-inden-5-yloxy)-2H-
chromen-2-ones (11) by crystallisation from appropriate
solvent (ethanol or n-heptane) is an additional benefit.
Contrary to the reaction in acetonitrile, the same reaction
performed in dry acetone or dry dichloromethane did not
lead to the desired products; only starting materials and
traces of products (\ 5%) were obtained in those cases,
possibly because of a worse transition state solvation.
Fig. 3 Structure of coumarin (5, FP - fluorescent probe) and ninhy-
drin-coumarin derivative (6)
ninhydrin skeletons into one molecule has been published,
although without preserving the triketone function [23].
We hoped to find a reagent that would react with fin-
gerprint amino acids within 4 h to afford a molecule
exhibiting sufficiently different absorption and fluores-
cence characteristics compared to those of the reagent (e.g.
a change in the position of the absorption and emission
maxima, a change of the extinction coefficients, a change
of the quantum yield of fluorescence or the lifetime of the
fluorescence emission). The formation of a product in
which absorption and emission maxima are significantly
redshifted (bathochromically) as a consequence of a more
intense intramolecular charge transfer could lead to an
elimination of background fluorescence. The increase of
the signal/noise ratio results in a significant augmentation
of the contrast between the developed fingerprint and the
surface. Various non-covalent interactions (e.g. electro-
static interactions, hydrogen bonds) might also contribute
to the increase of the contrast between visualised finger-
prints and paper surface. The proposed molecules should
Scheme 1
123

J. Gašpar et al.
Coumarins 11 can be readily oxidised to ninhydrin
derivatives 12 by SeO2 in dioxane. The addition of water
(5%) to the reaction mixture improved the yields of the
products. We obtained two new derivatives 12 in good
yields (61–63%) as stable hydrates. A formation of dihy-
droxy derivatives was expected, since it is generally known
that ninhydrin exists as a stable hydrate and the tricarbonyl
form is only present under rigorously anhydrous conditions
Furthermore, the methoxy derivative 12b fluoresces
more intensively due to the electron-donating substituent
bound in the position C-7 of the coumarin skeleton com-
pared to the unsubstituted 12a. The intensity of fluores-
cence depends on the solvent polarity; however, it has only
slight influence on the position of the emission maxima.
The ratio of band’s intensity I453/I376 for 12b is larger than
1 in chloroform; this applies vice versa to methanol
(Fig. 4).
´
[1]. Applying reaction conditions reported by Joullie [2] to
the oxidation of indanone derivatives to ninhydrins in
acetic acid/dioxane mixture or in glacial acetic acid did not
lead to an increase of yields of products, and tarry by-
products only separable by chromatography were formed in
addition to the desired ninhydrins 12.
As mentioned above, the structure of compounds 12 was
designed to improve the quality of fingerprint impressions
by the enhancement of the contrast between a background
and the developed fingerprint itself. We have assumed that
the fluorescence of ninhydrin reaction products obtained by
reaction of 12 with the amino acids presented in latent
fingerprints contributes to the quality improvement of the
fingerprint impressions without another secondary treat-
ment. Therefore, we have examined the reactivity of nin-
hydrins 12 with amino acids. We have monitored the
influence of the amino acid phenylalanine on the fluores-
cence of 12 in solutions under conditions simulating some
real circumstances of the fingerprint development process
(Figs. 5, 6).
Behaviour of prepared ninhydrins
Fluorescence spectroscopy was used for monitoring the
spectral behaviour of ninhydrin derivatives 12 in methanol
and chloroform. The fluorescence of coumarin derivatives
depends on the substitution of the coumarin skeleton (5).
We have observed a different structural character for the
fluorescence spectra of the prepared ninhydrins 12. Nin-
hydrin 12a (unsubstituted phenyl ring in the coumarin
scaffold) has an emission maximum at 376 nm in CHCl3
and at 388 nm in MeOH. A substitution with an electron-
donating group (OMe) leads to an intramolecular charge
transfer in the compound 12b affecting the formation of the
new batochromically shifted band caused by a new deac-
tivation path in the de-excitation process (Fig. 4). Thus, the
spectrum of the methoxy derivative 12b exhibits two
emission maxima in chloroform, one just like 12a at
376 nm and the second one at 453 nm.
As can be seen in Figs. 5 and 6, a significant increase of
fluorescence intensity occurs after the addition of the
amino acid to ninhydrins 12 solutions. The largest change
in the fluorescence intensity is achieved after heating the
solutions with phenylalanine for 3 min in both cases. This
behaviour of prepared derivatives 12 fulfils the funda-
mental objective of using fluorescence to increase the
quality of visualised fingerprints. The heating treatment
corresponds with a commonly used ninhydrin latent print
enhancement procedure in forensic laboratories.
Fig. 5 Emission spectra of 12a in methanol in the presence of 0.5 eq
phenylalanine and glacial acetic acid (c12a = 5 9 10-5 M, kex-
= 320 nm, T = 50 °C for 3 min)
Fig. 4 Emission spectra of compounds 12 in methanol and chloro-
form (c = 5 9 10-5 M, kex = 320 nm)
123

Amino acid-sensitive reagents with coumarin moiety for latent prints examination
donors who had not consumed food or handled chemicals
30 min prior to providing specimen fingerprints. Brown-
red fingerprints were developed in 5 min. Figures 7 and 8
show comparisons of the developed fingerprints in daylight
as well as with a 365 nm light source.
Compounds 12 provide fingerprint impressions with
improved contrast between the developed fingerprint and
the background. The developed fingerprints are visible in
daylight; moreover, the change of wavelength to 365 nm
results in improved and clear fingerprints suitable for fin-
gerprint identification. This fact is consistent with the
measured fluorescent spectra of the prepared compounds.
These types of the derivatives are potentially suitable for
the development of latent prints on dark surfaces, since
ninhydrin reaction products produce fluorescent prints
under UV light. The prints developed using these com-
pounds are stable and do not vanish from paper for a rel-
atively long time (5 months).
Fig. 6 Emission spectra of 12b in methanol in the presence of 0.5 eq
phenylalanine and glacial acetic acid (c12b = 5 9 10-5 M, kex-
= 320 nm, T = 50 °C for 3 min)
Fingerprint development
Conclusion
The detection of a latent fingerprint can be done in many
ways, although some are purely theoretical and unusable in
forensic practice. On the other hand, there is no method
which is known to be universal and applicable for all
materials or conditions; therefore, the usage of each
method varies from case to case.
New ninhydrin derivatives were designed and successfully
synthesised by a good yielding, multistep protocol. These
compounds can be used as dual fingerprint reagents. 2,2-
Dihydroxy-5-(2-oxo-2H-chromen-4-yloxy)-2H-indane-1,3-
diones produce highly coloured Ruhemann’s purple species
that also exhibit fluorescence without secondary metal
treatment. The usage of these compounds could simplify
the visualisation of latent fingerprints and may benefit the
forensic community.
To test the efficiency of the prepared compounds 12a
and 12b for the latent fingerprint enhancement, we pre-
pared a reagent solution. Latent fingerprints were collected
on a white paper (the standard copy paper, 80 g/m2) from
Fig. 7 Latent fingerprints developed on paper using 12a (left: in daylight; right: at 365 nm)
123

J. Gašpar et al.
Fig. 8 Latent fingerprints developed on paper using 12b (left: in daylight; right: at 365 nm)
4-Bromo-7-methoxychromen-2-one (10b) A mixture of
400 mg chromen-2-one 9b (2.08 mmol) and 775 mg
POBr3 (2.70 mmol) was stirred at 130 °C for 2 h and at
160 °C for an additional 15 min. The mixture was cooled
to room temperature, and 100 g of ice was added to the
resulting dark brown mixture. After allowing the mixture to
stand overnight, a brown precipitate was collected, washed
well with water, dried and recrystallised from EtOH to give
370 mg (70%) of 10b as orange solid. M.p.: 88–90 °C
Experimental
Chemicals and solvents were purchased from major
chemical suppliers (Merck Millipore, Darmstadt, Germany;
Acros Organics, Geel, Belgium; Sigma-Aldrich, St. Louis,
MO, USA) with the highest purity grade. All solvents were
dried by standard methods and distilled prior to use.
CeliteÒ 545 (Acros Organics), flux-calcined diatomaceous
earth, was used as filter agent. Thin-layer chromatography
was performed on Merck Millipore precoated aluminium
TLC plates with silica gel 60 F254 (hexanes/EtOAc).
Melting points were measured on a Kofler hot stage. IR
spectra were acquired on Nicolet FT-IR-ATR 6700
(Thermo Fisher Scientific, US) spectrometer and are given
1
(EtOH); H NMR (300 MHz, DMSO-d6): d = 3.88 (s, 3H,
OMe), 6.89 (s, 1H, H-3), 7.03–7.06 (m, 2H, H-4, H-5), 7.72
(d, J = 8.4 Hz, 1H, H-8) ppm; 13C NMR (75 MHz,
DMSO-d6): d = 56.68, 101.31, 112.47, 113.63, 116.21,
129.28, 141.25, 154.24, 158.78, 163.94 ppm. The IR
spectrum was found to be identical to the one described in
Ref. [29].
1
in cm-1. The H NMR and 13C NMR spectra were recor-
ded at 300 MHz and 75 MHz, respectively, on a Varian
VNMRS 300 MHz spectrometer in CDCl3 or DMSO-d6
with TMS as internal standard. Chemical shift values were
recorded in d units (ppm) and coupling constants (J) ex-
pressed in Hertz (Hz). Elemental analyses (C, H, N, S)
were conducted using a Carlo Erba Strumentazione 1106
apparatus (Carlo Erba Strumentazione, Milan, Italy), and
their results were found to be in good agreement ( 0.3%)
with the calculated values.
4-(1-Oxo-2,3-dihydro-1H-inden-5-yloxy)-2H-chromen-2-one
(11a, C18H12O4) A mixture of 300 mg 5-hydroxyindanone
(8, 2.02 mmol) and 550 mg K2CO3 (4.04 mmol) in 60 cm3
of dry acetonitrile was stirred for 30 min at room temper-
ature. Bromocoumarin 10a (460 mg, 2.02 mmol) was
added in one portion and the reaction mixture was refluxed
for 10 h. After cooling to room temperature, 70 g of ice
was added to the mixture. The brown precipitate was col-
lected, washed well with water, dried, and recrystallised
from acetone to give 420 mg (71%) of 11a as yellow solid.
M.p.: 162–164 °C (acetone); 1H NMR (300 MHz, CDCl3):
d = 2.79 (t, 2H, Ar–CH2–CH2–CO), 3.21 (t, 2H, Ar–CH2–
CH2–CO), 5.48 (s, 1H, H-3), 7.21 (dd, J = 8.3 Hz, 2.0 Hz,
1H, H-60), 7.31 (d, J = 2.0 Hz, 1H, H-40), 7.34–7.43 (m,
4-Hydroxy-7-methoxy-2H-chromen-2-one (9b) [27] and
4-bromo-2H-chromen-2-one (10a) [28] were prepared
according to the literature procedures. The structures of the
prepared compounds were proven by 1H NMR spectra and
by measuring their melting points.
123

Amino acid-sensitive reagents with coumarin moiety for latent prints examination
2H, H-6, H-8), 7.65 (ddd, J = 8.6 Hz, 7.3 Hz, 1.5 Hz, 1H,
H-7), 7.89 (d, J = 8.3 Hz, 1H, H-70), 8.01 (dd, J = 7.9 Hz,
1.5 Hz, 1H, H-5) ppm; 13C NMR (75 MHz, CDCl3):
d = 25.86, 36.44, 94.41, 115.11, 117.01, 119.27, 120.95,
122.99, 124.29, 126.16, 133.12, 135.56, 153.71, 157.57,
2,2-Dihydroxy-5-(7-methoxy-2-oxo-2H-chromen-4-yloxy)-
2H-indene-1,3-dione (12b, C19H12O8) mixture of
A
137 mg freshly sublimed, pulverised SeO2 (1.24 mmol),
0.6 cm3 of water, and 12 cm3 of dioxane was stirred at
60 °C until homogeneous (1 h). Indanone 11b (100 mg,
0.31 mmol) was added to one portion, and the reaction
mixture was refluxed for 2 h. The hot reaction mixture was
filtered through CeliteÒ and washed with 20 cm3 of diox-
ane. The filtrate was discoloured with activated charcoal,
filtered through a pad of CeliteÒ, and the solvent was
removed under reduced pressure. The crude product was
recrystallised from water to give 69.5 mg (61%) of 12b as
ꢀ
157.67, 162.15, 165.60, 204.91 ppm; IR (neat): m = 1703,
1621, 1605, 1262, 1231, 1180 cm-1
.
7-Methoxy-4-(1-oxo-2,3-dihydro-1H-inden-5-yloxy)-2H-
chromen-2-one (11b, C19H14O5) A mixture of 174 mg 5-
hydroxyindanone (8, 1.17 mmol) and 325 mg K2CO3
(2.35 mmol) in 40 cm3 of dry acetonitrile was stirred for
30 min at room temperature. Bromocoumarin 10b
(300 mg, 1.17 mmol) was added in one portion and the
reaction mixture was refluxed for 10 h. After cooling to
room temperature, 35 g of ice was added to the mixture.
The brown precipitate was collected, washed well with
water, dried and recrystallised from acetone to give 250 mg
(67%) of 11b as yellow solid. M.p.: 224–227 °C (acetone);
1H NMR (300 MHz, CDCl3): d = 2.78 (t, 2H, Ar–CH2–
CH2–CO), 3.19 (t, 2H, Ar–CH2–CH2–CO), 3.91 (s, 3H,
OCH3), 5.33 (s, 1H, H-3), 6.87 (d, J = 2.3 Hz, 1H, H-8),
6.93 (dd, J = 9 Hz, 2.4 Hz, 1H, H-60), 7.19 (dd,
J = 8.4 Hz, 2.3 Hz, 1H, H-6), 7.29 (d, J = 2.4 Hz, 1H, H-
40), 7.85–7.90 (m, 2H, H5, H-70) ppm; 13C NMR (75 MHz,
CDCl3): d = 25.81, 36.41, 55.85, 91.75, 100.65, 108.28,
112.64, 119.23, 120.95, 124.05, 126.04, 135.40, 155.62,
157.59, 157.65, 162.69, 163.81, 165.92, 204.94 ppm; IR
1
brown-yellow solid. M.p.: 159–161 °C (H2O); H NMR
(300 MHz, DMSO-d6): d =3.90 (s, 3H, OCH3), 5.48 (s,
1H, H-3), 7.04 (dd, J = 8.7 Hz, 2.1 Hz, 1H, H-60), 7.11 (d,
J = 2.1 Hz, 1H, H-40), 7.61 (s, 2H, OH), 7.90 (d, J = 9 Hz,
1H, H-5), 7.96–8.01 (m, 2H, H-6, H-8), 8.16 (d,
J = 8.7 Hz, 1H, H-70) ppm; 13C NMR (75 MHz, DMSO-
d6): d = 56.10, 87.86, 92.89, 100.82, 107.79, 112.54,
115.83, 124.26, 126.86, 130.01, 136.21, 141.06, 155.17,
159.23, 161.36, 163.52, 164.82, 195.66, 196.15 ppm; IR
ꢀ
(neat): m = 3233, 1765, 1721, 1682, 1621, 1594, 1233,
1161 cm-1
.
Spectral study and development of fingerprints
Fluorescence spectra were measured in a 1 cm cuvette with
an FSP 920 (Edinburgh Instruments, UK) spectrofluo-
rimeter in front-face arrangement to avoid the self-ab-
sorption effect. Fingerprint images were taken by DSC4
Fingerprint Imaging System (Foster ? Freeman, UK) with
Crime–liteÒ 8 9 4, 365 nm filter.
ꢀ
(neat): m = 1718, 1692, 1624, 1603, 1290, 1239,
1152 cm-1
.
2,2-Dihydroxy-5-(2-oxo-2H-chromen-4-yloxy)-2H-indene-
1,3-dione (12a, C18H10O7) A mixture of 220 mg freshly
sublimed, pulverised SeO2 (2.05 mmol), 1 cm3 of water,
and 20 cm3 of dioxane was stirred at 60 °C until homo-
geneous (1 h). Indanone 11a (150 mg, 0.51 mmol) was
added in one portion, and the reaction mixture was refluxed
for 2 h. The hot reaction mixture was filtered through
CeliteÒ and washed with 30 cm3 of dioxane. The filtrate
was discoloured with activated charcoal, filtered through a
pad of CeliteÒ, and the solvent was removed under reduced
pressure. The crude product was recrystallised from water
to give 110 mg (63%) of 12a as white solid. M.p.: 123–
Working solution: 10 mg of ninhydrin derivative 12 was
dissolved in 0.13 cm3 EtOH, followed by the addition of a
drop of ethyl acetate and a drop of glacial acetic acid. The
prepared solution was diluted with 0.10 cm3 of HFE-7100
(methoxynonafluorobutane, Sigma-Aldrich).
Fingerprints: Latent fingerprints were collected on a
white paper (standard copy paper, 80 g/m2) from donors
who had not consumed food or handled chemicals 30 min
prior to providing specimen fingerprints. Donors were
instructed to gently place fingertips onto the paper and not
to remove their hands until fingers had been outlined in
graphite pencil. The paper substrate was left to age for
2 days in a dark place and then immersed into the prepared
working solution. The paper was air dried at room tem-
perature and heated in an oven at 150 °C.
1
126 °C (H2O); H NMR (300 MHz, DMSO-d6): d = 5.67
(s, 1H, H-3), 7.44–7.53 (m, 2H, H6, H-8), 7.64 (s, 2H, OH),
7.74–7.80 (m, 1H, H-7), 8.00–8.04 (m, 3H, H-5, H-40, H-
60), 8.18 (dd, J = 8.1 Hz, 0.9 Hz, 1H, H-70) ppm; 13C
NMR (75 MHz, DMSO-d6): d = 88.31, 96.17, 115.18,
116.40, 117.07, 123.55, 125.02, 127.41, 130.53, 133.94,
136.75, 141.56, 153.61, 159.66, 161.43, 164.95, 196.16,
Acknowledgements This publication is the result of the project
implementation: Centre of Excellence in Security Research supported
by the Research and Development Operational Programme funded by
the ERDF. Grant Number: ITMS 26240120034.
ꢀ
196.63 ppm; IR (neat): m = 3260, 1759, 1720, 1677, 1623,
1593, 1257, 1230, 1194 cm-1
.
123

J. Gašpar et al.
16. Grigg R, Mongkolaussavaratana T, Pounds CA, Sivagnanam S
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