Synthesis and nonlinear optical properties of linear and Λ-shaped pyranone-based chromophores

Article abstract of DOI:10.1016/j.tet.2008.02.009

New, pyranone-based chromophores were synthesized and their (nonlinear) optical properties were measured. The chromophores were prepared by first condensing an electron withdrawing group with pyranone, followed by reaction with an aldehyde-functionalized π-conjugated bridged donor molecule. This approach enables one to easily incorporate the pyranone moiety and to prepare both linear and Λ-shaped chromophores. The (nonlinear) optical properties were measured using femtosecond hyper-Rayleigh scattering. These measurements demonstrated the advantages of this approach.

Full text of DOI:10.1016/j.tet.2008.02.009

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 3772e3781
www.elsevier.com/locate/tet
Synthesis and nonlinear optical properties of linear
and L-shaped pyranone-based chromophores
a,b
Guy Koeckelberghs , Leen De Groof , Javier Perez-Moreno , Inge Asselberghs ,
a
b
b
´
Koen Clays b, Thierry Verbiest b, Celest Samyn a,
*
a Laboratory of Macromolecular and Physical Organic Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium
b Laboratory of Molecular Electronics and Photonics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Heverlee, Belgium
Received 10 January 2008; received in revised form 4 February 2008; accepted 5 February 2008
Available online 7 February 2008
Abstract
New, pyranone-based chromophores were synthesized and their (nonlinear) optical properties were measured. The chromophores were
prepared by first condensing an electron withdrawing group with pyranone, followed by reaction with an aldehyde-functionalized p-conjugated
bridged donor molecule. This approach enables one to easily incorporate the pyranone moiety and to prepare both linear and L-shaped chro-
mophores. The (nonlinear) optical properties were measured using femtosecond hyper-Rayleigh scattering. These measurements demonstrated
the advantages of this approach.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Nonlinear optics; Chromophores; Pyranone; L-Shaped chromophores
1. Introduction
L-shaped chromophores can be built-in into accordion-type
polymers.6,9,11,12 After polingdto obtain the necessary macro-
molecular noncentrosymmetrydaccordion polymers tend to
relax slower, resulting in a more stable NLO response.
Some 2,6-dimethyl-4H-pyran-4-on (pyranone)-based chro-
mophores, both linear and L-shaped, have already been pre-
pared and studied. The advantage of the incorporation of the
pyranone unit is that it not only extends the p-conjugation
in comparison with analogous chromophores, which lack
this group, but also that it gives the possibility to prepare
both linear and L-shaped chromophores.3,10,11 The L-shaped
pyranone-based chromophores, which have been prepared
and studied before, were typically equipped with rather
moderate electron withdrawing groups (usually a dicyano-
methylene group) and/or a poor variety of rather simple p-
conjugated systems.
The continuous interest in poled polymers for nonlinear
optical (NLO) applications has resulted in the development
of numerous chromophores and a profound understanding of
their structureeproperty relationship.1,2 Most chromophores
are linear, rigid, p-conjugated molecules, end-capped with
an electron donating and electron withdrawing group. The
DpA-structure, present in these molecules, triggers their large
second-order hyperpolarizabilities. Apart from linear DpA
chromophores, also L-shaped chromophores have been devel-
oped.3e11 Their assets are double. First, depending on the
angle between the constituting linear DpA parts, the hyperpo-
larizability of L-shaped chromophores can be higher than
the hyperpolarizability of the individual, linear chromophores
they consist of. Second, unlike linear chromophores, which
are usually incorporated as side-chains in polymer systems,
In this manuscript, the synthesis and (nonlinear) optical
properties of some new linear and L-shaped chromophores
are described. They all consist of a pyranone unit, which is
functionalized with different electron withdrawing groups
and one (linear) or two (L-shaped) amino-substituted
* Corresponding author. Tel.: þ32 (0) 16 32 74 38; fax: þ32 (0) 16 32 79 90.
E-mail address: celest.samyn@chem.kuleuven.be (C. Samyn).
0040-4020/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.02.009

G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
3773
p-conjugated system(s). A variety of moderate to excellent
2.2. Chromophore synthesis
electron withdrawing groups are used, together with an ex-
tended p-conjugated bridge. The (nonlinear) optical proper-
ties of both types of chromophores are compared and
evaluated in detail.
The synthesis of the chromophores is displayed in Scheme
1. First, aldehyde 1 is reduced with NaBH4 to the correspond-
ing alcohol 2, which is converted into the phosphonium salt 3
in a one-step reaction with triphenyl phosphonium bromide.
Next, 3 was reacted with 4 using a Wittig reaction, rendering
5 as a cis/trans mixture. Although a Horner reaction would re-
sult in pure trans-alkene, a Wittig reaction was preferred to in-
troduce a double bond. The reason for this approach is the fact
that we encountered great difficulties in converting the alcohol
2 into its corresponding chloride. Presumably, polymerization
of the benzylic halide occurs. Compound 5 was protected as an
acetate ester, after which the aldehyde functionality was intro-
duced by a Vilsmeyer reaction. After deprotection of 7, the
building block 8 was obtained, still as a mixture of cis and
trans isomers.
2. Results and discussion
2.1. Chromophore design
Several parameters in the design of the chromophores were
taken into account. A general structure of the chromophores is
presented in Figure 1. All chromophores contain an amino
functionality as donor, while four different acceptor groups
were incorporated. Special attention has been given to the
p-conjugated bridge, in which a central thiophene moiety
was incorporated. The choice of the thiophene moiety can
be motivated as follows: on one hand, Marder et al. have
shown that very easily polarizable spacers, such as polyenic
spacers, when substituted with strong electron donating and
electron withdrawing groups, show minor NLO properties.13
Moreover, polyenic chromophores tend to have low thermal
and photochemical stabilities. Aromatic spacers based on ben-
zene, on the other hand, show superior stability, but are much
less polarizable. Thiophene-based chromophores, however,
have shown to combine the necessary stability with large sec-
ond-order nonlinear hyperpolarizabilities.14e21 As mentioned
earlier, a pyranone unit was incorporated to further extent
the conjugation length.
Next, also the shape of the (linear) chromophores was taken
into account. When incorporated to further extend the polymer
system, the highly dipolar chromophores interact with each
other above a critical chromophore concentration, resulting
in a centrosymmetric, NLO inactive, ensemble. These un-
wanted interactions can be diminished by carefully substitut-
ing the linear chromophore with alkyl groups, resulting in an
ellipsoidal shape.22 Moreover, these alkyl groups increase
the solubility of the chromophore.
The key step in the chromophore synthesis is the Knoeve-
nagel condensation of 9aed with aldehyde 8. This renders
all-trans chromophores. Compounds 9aed were prepared by
a Knoevenagel condensation of 10 with the appropriate accep-
tor molecules (Scheme 2).
Although it would be advantageous for the synthesis of
these particular chromophores to first condense 10 with 8
and then react the acceptor molecules 11e14 with 15 (since
that approach would reduce the total number of reaction steps,
Scheme 3), the former pathway was preferred, since it allows
to condense a large number of different aldehydes with
9aed. Consequently, this is an easy, fast and general way to
prolong the conjugation length of already existing chromo-
phoresdwhich are typically synthesized by condensing their
corresponding aldehydes with the appropriate acceptor mole-
culesdby two double bonds. It is worthwhile to mention that
it was also tried to condense 10 first with 8 and then react
the acceptor molecules with 15. Unfortunately, this synthesis
failed at the first stage.
In the condensation reaction of the pyranone derivatives
9aed with aldehyde 8, both mono and di-reaction takes pla-
ces, resulting in the linear (a1ed1) and L-shaped (a2ed2)
chromophores, respectively. In all cases, they could easily be
separated by column chromatography.
During the synthesis of d1, 9d, which is asymmetric, can
react with the aldehyde at each of both methyl groups, result-
ing in two different mono-reacted chromophores. Unfortu-
nately, both isomers could not be separated and purified;
therefore, that chromophore was not further investigated.
Finally, the chromophores are substituted with one (linear
chromophores) or two (L-shaped chromophores) alcohol
functionalities, allowing them to be covalently attached to
a polymer backbone (linear chromophores) or to be built-in
in accordion polymers (L-shaped chromophores). The synthe-
sis and nonlinear optical properties of those polymers, includ-
ing the influence of the molecular structure of the polymer
(linear vs accordion) on their properties, are now under
investigation.
2.3. Linear optical properties
A
The optical properties of the chromophores are listed in
Table 1. In order to avoid the influence of the intramolecular
H-bridge between the terminal OH and the amino functionality,
which weakens the electron donating capacity of the dialkyl-
amino functionality, the alcohol groups of the chromophores
aed were converted into acetate groups for this study. The
acylation was performed with acetic anhydride (Scheme 4).
No base was added to prevent nucleophilic attack on the
R1
HO
O
R
S
N
R = CH3 / R1
A = electron accepting group
Bu
Bu
Figure 1. General structure of the chromophores.

3774
G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
Bu
Bu
CHO
Bu
Bu
CH2OH
Bu
Bu
CH2
HO
Br
P
i
ii
Ph
Ph
Ph
S
S
S
1
2
3
N
CHO
iii
4
Bu
Bu
RO
S
N
R = H
5
iv
6
R = OAc
Bu
v
Bu
CHO
RO
S
N
R = OAc 7
vi
R = H 8
A
vii
9a-d
O
A
R1
HO
R = CH3 a1-d1
R =R1 a2-d2
O
R
S
N
Bu
Bu
O
O
O
O
O
CN
CN
N
N
O
N
A =
S
O
N
N
a
c
b
d
Scheme 1. Synthesis of the chromophores. Reagents and conditions: (i) (1) NaBH4, (2) H2O; (ii) P(C6H5)3$HBr; (iii) NaOEt; (iv) Ac2O; (v) OPCl3/DMF; (vi)
NaOH (aq); (vii) piperidine, H2O.
p-conjugated bridge.23 It must be noted that it was also tried to
convert the hydroxyl group to a tert-butyldimethylether, but that
the reaction resulted in very low yields and highly impure reac-
tion compounds. Probably, nucleophilic attack of the base pres-
ent (DMAP) is the most common side-reaction.
Although the general belief is that intramolecular H-bridges
on the amino functionality would weaken its electron donating
capability, this effect is not observed upon comparing the alco-
hol-terminated chromophores xi (x¼a, b, c or d; i¼1 or 2) with
the acetate-terminated ones xieOAc. Quite on the contrary, all
xieOAc show a wavelength of maximal absorption that is
10 nm blue-shifted with respect to the maximum for the xi vari-
ants. This points at a minor negative electronic effect on the do-
nor, rather than the expected positive effect through preventing
H-bridging. This spectral shift (10 nm) is minor with respect to
the shifts that are induced by the structural modifications for
this study (linear or L-shape, and variation of electron acceptor
strength). Because (intermolecular) H-bridges can also have
a concentrationedependant effect, especially on even-order non-
linear properties because of the importance of noncentrosymme-
try, the second-order nonlinear optical properties have therefore
onlybeendeterminedoftheacetate-terminatedxieOAc variants.
The effect of the use of our pyranone conjugated moiety is
already clearly observed in the red-shift for the wavelength of
maximal absorption for our new pyranone-based chromo-
phores when comparing with the analogous chromophores
without this moiety.16 This clearly demonstrates already in
the linear optical properties one of the assets of our protocol,
e.g., the increase of the conjugation length, resulting in
a higher lmax by simply condensing aldehyde 8 with the pyr-
anone-based electron-accepting groups 9aed instead of the
electron-accepting groups 11e14.

G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
3775
O
DπΑ
Ac2O
DπΑ
a-OAc - d-OAc
HO
AcO
NC
CN
O
O
a-d
N
N
O
Scheme 4. Acylation of the chromophores aed.
O
O
CN
11
CN
O
9a
O
N
N
13
When comparing the effect of the different electron accep-
tors on the linear optical properties, it is clear that the dicyano-
methylene benchmark acceptor group is the weakest in our
series. The wavelengths of maximal observation progressively
shift to larger values upon replacing this benchmark by barbi-
turic acid, thiobarbituric acid and isoxazolone. This will have
its influence on the second-order nonlinear optical properties
(vide infra).
i
i
O
9c
O
10
i
i
O
O
N
O
O
O
O
N
N
O
S
N
12
O
O
14
N
N
O
9d
The effect of the molecular structural motif (linear vs
L-shaped) is already visible in their different linear optical
properties. Careful inspection of the absorption spectra not
only reveals a substantial red-shift of the wavelength of max-
imal absorption for the L-shaped motives with respect to the
linear molecules. The former molecules, incorporating two
chromophoric subunits sharing the pyranone-acceptor moiety,
also exhibit a larger oscillator strength and a larger full-width-
half-max (FWHM) spectral breath (a consequence of a second
transition, showing up as a shoulder to the right of the maxi-
mum). A similar behaviour has also been observed by Moylan
et al.3 They assumed that two transitions are present in
L-shaped chromophores, closely situated to the single transi-
tion of the parent linear chromophore. The absorption of the
L-shaped chromophores is a superposition of two transitions,
which can explain the red-shift and significant increase in
extinction coefficient.
We have analyzed the spectra in terms of their maximum
extinction coefficient (in Mꢀ1 cmꢀ1) and FWHM (in nm),
resulting in an approximated area S (in Mꢀ1 cmꢀ1 nm).
This integrated linear property relates very nicely to the num-
ber of chromophoric subunits in the molecules: around
5000 Mꢀ1 cmꢀ1 nm for the x1eOAc molecules versus around
10,000 Mꢀ1 cmꢀ1 nm for the x2eOAc variants (Table 1).
S
9b
Scheme 2. Synthesis of the pyranone derivatives 9aed. Reagents and condi-
tions: (i) Ac2O.
Bu
Bu
HO
S
S
CHO
N
N
8
O
O
Bu
10
Bu
HO
15
O
O
11, 12
13, 14
a-d
Scheme 3. Alternative pathway to chromophores aed.
2.4. Second-order nonlinear optical properties
Table 1
Linear optical properties of the chromophores in THF
The second-order nonlinear optical properties of the ace-
tate-terminated chromophores have been determined in THF.
We have used femtosecond hyper-Rayleigh scattering (HRS)
at 800 nm to determine the depolarization ratio and the first
hyperpolarizability (molecular second-order nonlinear polariz-
ability) of the molecules in solution. The femtosecond pulses
at high repetition rate provide the means to check for multi-
photon fluorescence contribution to the HRS signal. We
have clearly observed that the apparent first hyperpolarizabil-
ity as a function of amplitude modulation frequency is con-
stant. This is a clear experimental proof of the absence of
this potential source of systematic overestimation of the first
hyperpolarizability.
Chromophore lmax
3
FWHM
(nm)
S
Ratio
(nm) (103 l molꢀ1 cmꢀ1
)
(Mꢀ1 cmꢀ1 nm)
a1
a1eOAc
534 43.0
523 34.0
140
158
140
177
130
160
4760
10,900
6090
1
a2
a2eOAc
564 65.8
553 69.0
2.3
1
b1
b1eOAc
577 43.7
567 43.5
b2
b2eOAc
601 54.3
591 68.5
12,154
5460
2
c1
c1eOAc
549 45.0
539 42.0
1
c2
c2eOAc
579 64.4
566 62.5
Concerning the molecular motive (linear or L-shaped), the
first observation relates the HRS depolarization ratio r. For the
linear molecules x1eOAc, this r-value should be relatively
high (in the limit of strictly only one hyperpolarizability tensor
10,000
1.8
d2
d2eOAc
590 68.3
580 80.0

3776
G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
element bzzz contributing along the unique molecular z-axis, in
combination with a limiting experimental numerical aperture
of zero, this r-value should be 5). For L-shaped molecules
x2eOAc with more off-diagonal tensor elements contributing,
this depolarization ratio r should be lower, with a lower limit
of 1.5.8 A larger r-value for all x1eOAc and the lower r-value
for all x2eOAc is consistently observed (Table 2).
acid and thiobarbituric acid and reaches its maximum for
isoxazolone as acceptor moiety.
When comparing the hyperpolarizability values between
monomeric x1eOAc and L-shaped dimeric chromophores
x2eOAc, only the overall HRS response in terms of bHRS
can be analyzed without taking the symmetry into consider-
ation. A slight improvement in overall nonlinear response is
observed for the L-shaped molecules. The detailed analysis
in terms of contributing tensor elements (see above) clearly
reveals the correlated nature of the two.
Due to the correlated nature of the two chromophoric sub-
units at 120ꢁ with respect to each other, it can be expected that
the L-shaped chromophores will perform better in nonlinear
optical devices such as an electro-optic modulator, than their
linear counterparts. The reason is double. First, they will
more effectively be aligned, due to their larger dipole moment,
which increases the macroscopic nonlinear optical response.
Second, the polarization sensitivity of any nonlinear device
made of these L-shaped molecules will be less. There will
be more nonlinear response irrespective of the incoming polar-
ization, because of the off-diagonal tensor elements present in
these L-shaped molecules.
Next, from the intensity HRS measurements, the overall,
symmetry-independent bHRS can be determined. A slightly
larger one can be observed for the bHRS of the L-shaped chro-
mophores. For a more detailed analysis of this overall response
towards specific hyperpolarizability tensor elements, an as-
sumption about the (approximate, effective for nonlinear op-
tics) molecular symmetry should be made. This effective
symmetry is largely determined by the relative orientation of
the electron donating and accepting groups and the conjuga-
tion path, rather than by saturated substitutions. The symmetry
for the x1eOAc molecular motives can be CN,v with a single
bzzz hyperpolarizability tensor element. For the x2eOAc
L-shaped molecules, C2v symmetry with two hyperpolarizabil-
ity tensor elements bzzz and bzxx can be assumed. It is also
assumed that the L-shaped molecules are built up from two
monomeric x1eOAc subunits with a monomeric hyperpolar-
izability bmono¼bzzz. The relations between these parameters
as a function of the angle between the two subunits in the
L-shaped chromophore based on pyranone (120ꢁ) have been
enumerated in earlier publications about correlated chromo-
phores.8,24 The fact that the retrieved bmono for the L-shaped
molecules are within experimental error identical to the bzzz
for the monomeric x1eOAc molecules, validates our assump-
tion that the L-shaped chromophores can indeed be considered
as consisting of two correlated monomeric subunits with an
angle of 120ꢁ between the two arms.
3. Conclusion
New, pyranone-based chromophores were synthesized and
their linear and second-order nonlinear optical properties
were measured. The chromophores were prepared by first con-
densing an electron withdrawing group to pyranone, followed
by reaction with an aldehyde-functionalized p-conjugated
bridge donor molecule. This approach enables one to easily
incorporate the pyranone moiety in new chromophores and
to prepare both linear and L-shaped chromophores. The non-
linear optical properties were measured using femtosecond
hyper-Rayleigh scattering and analyzed assuming a simple
symmetry. The measurements of the (nonlinear) optical prop-
erties demonstrate the advantages of this synthetic approach
for chromophores with enhanced properties.
Continuing the analysis of our use of the pyranone as a con-
jugated building block, we observe that also concerning their
second-order nonlinear optical properties, our chromophores
outperform their non-pyranone-based analogues.16 This obser-
vation further justifies our chromophore design strategy based
on the pyranone moiety.
The trend in hyperpolarizability value upon increasing the
electron-accepting capacity in the x1eOAc series clearly
follows the expectations from the linear optical properties:
the dicyanomethylene benchmark shows the lowest hyperpo-
larizability and this value steadily increases for the barbituric
4. Experimental
4.1. General
1H and 13C nuclear magnetic resonance (NMR) measure-
ments were carried out with a Bruker Avance 300 MHz. All
starting materials were purchased from Acros Organics, Fluka,
Merck or Aldrich and were used as received. N,N-dimethyl-
formamide (DMF) was distilled over CaH2 and further dried
Table 2
Second-order nonlinear optical properties of the chromophores in THF
Chromophore
r
bHRS
bzzz
bzxx
bmono
over molecular sieve (4 A). Compounds 125 and 9a26 were syn-
˚
(10ꢀ30 esu) (10ꢀ30 esu) (10ꢀ30 esu) (10ꢀ30 esu)
thesized according to literature procedures. The experimental
details for hyper-Rayleigh scattering experiments at 800 nm
were as previously described.27
a1eOAc
a2eOAc
2.4ꢂ0.3 260ꢂ20
1.7ꢂ0.2 300ꢂ20
630ꢂ50
150ꢂ10
d
450ꢂ30
d
630ꢂ50
600ꢂ40
b1eOAc
b2eOAc
2.0ꢂ0.2 340ꢂ20
830ꢂ50
830ꢂ50
1.4ꢂ0.2 490ꢂ20
250ꢂ10
750ꢂ30
d
580ꢂ30
990ꢂ40
4.2. Synthesis of 3,4-dibutyl-5-(hydroxymethyl)thiophene 2
c1eOAc
c2eOAc
2.2ꢂ0.2 350ꢂ20
1.5ꢂ0.2 380ꢂ20
1.6ꢂ0.2 400ꢂ40
850ꢂ50
190ꢂ10
200ꢂ20
850ꢂ50
770ꢂ40
800ꢂ80
A solution of 1 (236 mmol, 53.2 g) in ethanol (360 mL)
was added dropwise at 0 ꢁC to a suspension of NaBH4
d2eOAc
620ꢂ60

G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
3777
(236 mmol, 8.68 g) in ethanol (90 mL). The reaction mixture
was stirred overnight at room temperature in a flask, equipped
with a CaCl2-tube. The solvent was removed and the reaction
mixture was redissolved in dichloromethane and washed with
a saturated NH4Cl-solution. The organic layer was separated
and dried over MgSO4. The crude reaction product was
purified with column chromatography (silica gel; eluents: di-
chloromethane/hexane 4/6) and isolated as an oil.
Yield: 46.4 g (88%).
13C NMR (CDCl3, ppm): d¼148.0, 143.5, 139.2, 138.0,
130.8, 127.8, 127.7, 126.6, 117.5, 113.2, 60.6, 52.9, 46.1,
33.6, 32.3, 29.2, 27.5, 23.2, 23.1, 14.4, 12.4.
MS: m/z¼385 (Mþ), 354 (MþꢀC8H3O).
C24H35NOS calcd: C 74.76%, H 9.15%, N 3.63%; found: C
74.58%, H 8.95%, N 3.54%.
4.5. Synthesis of 2-[N-ethyl-N-[4-[2-[2-(3,4-dibutyl)-
thienyl]ethenyl]phenyl]amino]ethylethanoate 6
1H NMR (CDCl3, ppm): d¼6.87 (s, 1H), 4.75 (s, 2H), 2.51
(m, 4H), 1.65 (m, 4H), 1.44 (m, 4H), 0.97 (t, 6H).
13C NMR (CDCl3, ppm): d¼142.5, 140.4, 134.2, 119.2,
64.5, 33.1, 31.9, 27.3, 26.7, 22.9, 22.5, 14.0, 13.9.
MS: m/z¼225 (Mþ).
A mixture of 5 (10.0 mmol, 3.86 g) and acetic anhydride
(5 mL) was stirred at 60 ꢁC for 12 h in a flask, equipped
with a CaCl2-tube. Acetic acid and the excess acetic anhydride
was evaporated and the crude mixture was purified with col-
umn chromatography (silica gel; eluents: dichloromethane)
and isolated as an oil in a mixture of cis/trans isomers (10/90).
Yield: 3.90 g (90%).
C13H22OS calcd: C 68.97%, H 9.80%; found: C 68.86%, H
9.68%.
4.3. Synthesis of (3,4-dibutyl-5-thienylmethyl)triphenyl-
phosphonium bromide 3
1H NMR (CDCl3, ppm): trans: d¼7.34 (d, 2H), 7.03 (d,
J¼16.1 Hz, 1H), 6.79 (d, J¼16.1 Hz, 1H), 6.69 (d, 2H), 6.68
(s, 1H), 4.23 (t, 2H), 3.56 (t, 2H), 3.42 (q, 2H), 2.61 (t, 2H),
2.48 (t, 2H), 2.04 (s, 3H), 1.60 (m, 4H), 1.42 (m, 4H), 1.18
(t, 3H), 0.95 (t, 6H).
cis: d¼7.15 (d, 2H), 6.59 (d, 2H), 6.45 (d, J¼8.8 Hz, 1H),
6.42 (d, J¼8.8 Hz, 1H), 6.68 (s, 1H), 4.23 (t, 2H), 3.56 (t, 2H),
3.42 (q, 2H), 2.61 (t, 2H), 2.48 (t, 2H), 2.04 (s, 3H), 1.60 (m,
4H), 1.42 (m, 4H), 1.18 (t, 3H), 0.95 (t, 6H).
Triphenylphosphonium bromide (110 mmol, 39.0 g) and 2
(110 mmol, 24.9 g) were dissolved in acetonitrile (280 mL).
After refluxing for 4 h, the solution was concentrated to
100 mL and the product was precipitated in diethylether. The
precipitate was filtered off, washed with diethylether and dried.
Yield: 48.0 g (89%).
Mp: 174 ꢁC.
13C NMR (CDCl3, ppm): d¼171.0, 147.0, 143.1, 138.7,
137.6, 127.5, 127.4, 125.9, 116.9, 112.0, 61.7, 48.8, 45.3,
33.2, 31.9, 28.8, 26.7, 22.8, 22.7, 20.9, 14.0, 12.3.
MS: m/z¼427 (Mþ), 354 (MþꢀC3H5O2).
1H NMR (CDCl3, ppm): d¼7.66 (dd, 15H), 6.77 (s, 1H),
5.38 (d, J¼12.4 Hz, 2H), 2.36 (t, 2H), 1.90 (t, 2H), 1.48 (m,
2H), 1.35 (m, 2H), 1.21 (m, 2H), 1.00 (m, 2H), 0.94 (t, 3H),
0.77 (t, 3H).
C26H37NO2S calcd: C 73.02%, H 8.72%, N 3.28%; found:
C 72.89%, H 8.65%, N 3.17%.
13C NMR (CDCl3, ppm): d¼143.7, 142.4, 135.2, 134.2,
130.2, 121.0, 118.3, 117.2, 32.0, 28.6, 26.3, 25.7, 22.8, 22.4,
13.9, 13.8.
4.6. Synthesis of 2-[N-ethyl-N-[4-[2-[2-(3,4-dibutyl)thien-5-
al]ethenyl]phenyl]amino]ethylethanoate 7
MS: m/z¼552 (Mþ), 470 (MþꢀBr).
4.4. Synthesis of 2-[N-ethyl-N-[4-[2-[2-(3,4-dibutyl)-
thienyl]ethenyl]phenyl]amino]ethanol 5
OPCl3 (10.7 mmol, 1.0 mL) was dropwise added to a solu-
tion of 6 (8.90 mmol, 3.80 g) and DMF (23.2 mmol, 1.8 mL)
in dry dichloroethane (200 mL). The mixture was refluxed
for 18 h, cooled and poured into a NaOAc-solution (800 mL,
1 M). After the mixture was stirred vigorously for 2 h, the
layers were separated and the organic phase was dried over
MgSO4. The crude reaction product was purified with column
chromatography (silica gel; eluents: dichloromethane) and
isolated as a solid in a mixture of cis/trans isomers (10/90).
Yield: 2.50 g (62%).
A solution of NaOEt (150 mmol, 500 mL, 0.3 M) in etha-
nol was added dropwise to a solution of 4 (100 mmol,
19.3 g) and 3 (100 mmol, 55.3 g) in ethanol (1 L). After the
reaction mixture was refluxed for 5 h, it was cooled and the
solvent was removed in vacuo. The residue was dissolved in
dichloromethane, washed with water and dried over MgSO4.
The crude reaction product was purified with column chroma-
tography (silica gel; eluents: ethylacetate) and isolated as an
oil in a mixture of cis/trans isomers (30/70).
1H NMR (CDCl3, ppm): trans: d¼9.97 (s, 1H), 7.40 (d, 2H),
7.08 (d, J¼16.1 Hz, 1H), 6.99 (d, J¼16.1 Hz, 1H), 6.72 (d,
2H), 4.25 (t, 2H), 3.60 (t, 2H), 3.45 (q, 2H), 2.86 (t, 2H),
2.63 (t, 2H), 2.10 (s, 3H), 1.4 (m, 8H), 1.23 (t, 3H), 0.96 (t, 6H).
cis: d¼9.97 (s, 1H), 7.15 (d, 2H), 6.59 (d, 2H), 6.39 (d,
J¼8.8 Hz, 1H), 6.34 (d, J¼8.8 Hz, 1H), 4.25 (t, 2H), 3.60 (t,
2H), 3.45 (q, 2H), 2.86 (t, 2H), 2.63 (t, 2H), 2.10 (s, 3H),
1.4 (m, 8H), 1.23 (t, 3H), 0.96 (t, 6H).
Yield: 26.7 g (69%).
1H NMR (CDCl3, ppm): trans: d¼7.35 (d, 2H), 7.05 (d,
J¼16.8 Hz, 1H), 6.81 (d, J¼16.8 Hz, 1H), 6.73 (d, 2H), 6.71
(s, 1H), 3.82 (m, 2H), 3.47 (m, 4H), 2.62 (t, 1H), 2.50 (t,
4H), 1.60 (m, 4H), 1.44 (m, 4H), 1.19 (t, 3H), 0.99 (t, 6H).
cis: d¼7.18 (d, 2H), 6.65 (d, 2H), 6.48 (d, J¼8.8 Hz, 1H),
6.46 (d, J¼8.8 Hz, 1H), 6.71 (s, 1H), 3.82 (m, 2H), 3.47 (m,
4H), 2.62 (t, 1H), 2.50 (t, 4H), 1.60 (m, 4H), 1.44 (m, 4H),
1.19 (t, 3H), 0.99 (t, 6H).
13C NMR (CDCl3, ppm): d¼181.7, 171.0, 153.0, 148.3,
148.0, 140.3, 134.0, 132.6, 128.4, 124.5, 115.2, 111.9, 61.5,
48.7, 45.4, 34.4, 33.3, 26.7, 26.1, 22.8, 20.9, 13.9, 12.3.

3778
G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
MS: m/z¼455 (Mþ), 427 (MþꢀCO), 382 (MþꢀC3H5O2).
MS: m/z¼290 (Mþ).
C27H37NO3S calcd: C 71.17%, H 8.18%, N 3.07%; found:
C 70.78%, H 8.05%, N 2.99%.
C15H18N2O4 calcd: C 62.06%, H 6.25%, N 9.65%; found:
C 61.98%, H 6.18%, N 9.59%.
Compound 9d: Yield: 2.66 g (67%).
4.7. Synthesis of 2-[2-[4-[N-ethyl-N-(2-hydroxyethyl)amino]-
phenyl]ethenyl]-3,4-dibutyl-thien-5-al 8
Mp: 196 ꢁC.
1H NMR (CDCl3, ppm): d¼8.24 (s, 1H), 6.10 (s, 1H), 7.48
(m, 5H), 2.38 (s, 3H), 2.09 (s, 3H).
A NaOH-solution (16.5 mmol, 3.3 mL, 5 M in water) was
added to a solution of 7 (5.50 mmol, 2.50 g) in ethanol
(5 mL) and the mixture was stirred overnight at 40 ꢁC. The re-
action mixture was neutralized with an HCl-solution (5 M)
and extracted with dichloromethane. The combined organic
layers were washed with a saturated NaHCO3-solution and
dried over MgSO4. The crude reaction product was purified
with column chromatography (silica gel; eluents: dichloro-
methane) and isolated as an oil in a mixture of cis/trans
isomers (10/90).
13C NMR (CDCl3, ppm): d¼173.5, 165.7, 164.6, 162.7,
150.6, 131.6, 130.3, 129.3, 129.0, 108.0, 94.6, 20.8, 20.7.
MS: m/z¼268 (Mþ).
C16H13NO3 calcd: C 71.91%, H 4.90%, N 5.24%; found: C
71.81%, H 4.85%, N 5.19%.
4.9. Synthesis of the alcohol-functionalized chromophores
The general procedure is as follows: piperidine (0.3 mL) was
added to a solution of the pyranone derivative 9aed
(3.00 mmol) and aldehyde 8 (2.5 mmol) in toluene (15 mL).
The mixture was refluxed in a Dean Stark apparatus until the
calculated amount of water was azeotropically distilled off.
The reaction mixture was allowed to reach room temperature
and the solvents were evaporated in vacuo. The crude reaction
product was purified with column chromatography (silica gel;
the eluents is indicated for each chromophore individually)
and recrystallized from ethanol.
Yield: 2.10 g (97%).
1H NMR (CDCl3, ppm): trans: d¼9.97 (s, 1H), 7.39 (d,
2H), 7.08 (d, J¼16.1 Hz, 1H), 7.00 (d, J¼16.1 Hz, 1H), 6.75
(d, 2H), 3.83 (m, 2H), 3.51 (m, 4H), 2.86 (t, 2H), 2.63 (t,
2H), 1.66 (t, 1H), 1.4 (m, 8H), 1.21 (t, 3H), 0.97 (t, 6H).
cis: d¼9.97 (s, 1H), 7.13 (d, 2H), 6.64 (d, 2H), 6.43 (d,
J¼8.8 Hz, 1H), 6.38 (d, J¼8.8 Hz, 1H), 3.83 (m, 2H), 3.51
(m, 4H), 2.86 (t, 2H), 2.63 (t, 2H), 1.66 (t, 1H), 1.4 (m,
8H), 1.21 (t, 3H), 0.97 (t, 6H).
Compounds a1e2: Eluents: dichloromethane/acetonitrile
90/10.
Compound a1: Yield: 200 mg (14%).
13C NMR (CDCl3, ppm): d¼182.1, 153.5, 148.8, 140.7,
134.2, 133.0, 128.8, 124.9, 115.6, 112.7, 60.6, 52.8, 46.0,
34.8, 33.7, 27.3, 26.5, 23.2, 14.4, 14.3, 12.4.
Mp: 193 ꢁC.
MS: m/z¼413 (Mþ), 382 (MþꢀCH3O).
1H NMR (CDCl3, ppm): d¼7.53 (d, J¼15.4 Hz, 1H), 7.36
(d, 2H), 7.00 (d, J¼16.1 Hz, 1H), 6.89 (d, J¼16.1 Hz, 1H),
6.75 (d, 2H), 6.56 (s, 1H), 6.47 (s, 1H), 6.32 (d, J¼15.4 Hz,
1H), 3.82 (q, 2H), 3.5 (m, 4H), 2.6 (m, 4H), 2.37 (s, 3H),
1.70 (t, 1H), 1.46 (m, 8H), 1.19 (t, 3H), 0.98 (m, 6H).
13C NMR (CDCl3, ppm): d¼161.5, 159.6, 156.1, 148.3,
147.6, 141.8, 140.5, 131.3, 130.9, 129.1, 128.1, 125.1,
115.5, 115.4, 115.3, 114.5, 112.5, 106.1, 60.3, 58.1, 52.4,
45.6, 33.7, 33.3, 26.8, 26.7, 22.8, 22.6, 19.9, 14.0, 13.8, 12.0.
MS: m/z¼576 (Mþ).
C25H35NO2S calcd: C 72.60%, H 8.53%, N 3.39%; found:
C 72.49%, H 8.42%, N 3.27%.
4.8. Synthesis of the pyranone derivatives 9bed
The general procedure is as follows: a solution of 10
(15.0 mmol, 1.86 g) and 12e14 (15.0 mmol) in acetic acid an-
hydride (100 mL) was refluxed overnight under argon atmo-
sphere. The reaction mixture was allowed to reach room
temperature and then poured into ice water. The precipitate
was filtered off and washed with a NaHCO3-solution. Finally,
the crude reaction product was recrystallized from ethanol.
Compound 9b: Yield: 3.10 g (67%).
C35H41N3O2S calcd: C 74.04%, H 7.28%, N 7.40%; found:
C 73.81%, H 7.14%, N 7.31%.
Compound a2: Yield: 349 mg (15%).
Mp: 264 ꢁC.
Mp: 196 ꢁC.
1H NMR (CDCl3, ppm): d¼7.60 (d, J¼15.4 Hz, 2H), 7.39
(d, 4H), 7.03 (d, J¼15.4 Hz, 2H), 6.92 (d, J¼15.4 Hz, 2H),
6.76 (d, 4H), 6.57 (s, 2H), 6.42 (d, J¼15.4 Hz, 2H), 3.84 (q,
2H), 3.5 (m, 8H), 2.7 (m, 8H), 1.64 (t, 2H), 1.48 (m, 16H),
1.18 (t, 6H), 0.97 (m, 12H).
1H NMR (CDCl3, ppm): d¼8.84 (s, 2H), 4.58 (q, 4H), 2.48
(s, 6H), 1.32 (t, 6H).
13C NMR (CDCl3, ppm): d¼178.2, 166.1, 162.2, 158.7,
112.1, 97.0, 43.7, 21.1, 12.9.
MS: m/z¼306 (Mþ).
13C NMR (CDCl3, ppm): d¼160.3, 158.4, 155.0, 146.2,
140.7, 139.4, 130.1, 129.3, 128.0, 127.5, 123.3, 114.4, 114.3,
113.2, 110.4, 105.3, 105.0, 60.1, 57.0, 47.8, 44.3, 32.1, 32.2,
30.8, 28.6, 25.7, 25.6, 21.7, 21.6, 19.8, 18.9, 12.3, 12.8, 11.3.
MS: m/z¼964 (Mþ).
C15H18N2O3S calcd: C 58.80%, H 5.92%, N 9.14%; found:
C 58.71%, H 5.81%, N 9.08%.
Compound 9c: Yield: 2.74 g (64%).
Mp: 202 ꢁC.
1H NMR (CDCl3, ppm): d¼8.80 (s, 2H), 3.98 (q, 4H), 2.43
C60H74N4O3S2 calcd: C 74.80%, H 7.74%, N 5.82%;
found: C 74.69%, H 7.71%, N 5.75%.
(s, 6H), 1.24 (t, 6H).
13C NMR (CDCl3, ppm): d¼165.1, 164.1, 157.7, 151.0,
111.1, 95.7, 36.8, 21.0, 13.8.
Compound b1: Eluents:dichloromethane/ethylacetate90/10.
Yield: 119 mg (11%).

G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
3779
Mp: 204 ꢁC.
125.2, 117.4, 115.6, 112.5, 112.2, 95.3, 60.3, 52.4, 45.6,
36.4, 33.7, 33.4, 27.2, 26.7, 22.8, 22.7, 14.1, 14.0, 13.6, 12.0.
MS: m/z¼1080 (Mþ).
1H NMR (CDCl3, ppm): d¼8.89 (s, 1H), 8.70 (s, 1H), 7.63
(d, J¼15.4 Hz, 1H), 7.37 (d, 2H), 7.00 (d, J¼16.1 Hz, 1H),
6.88 (d, J¼16.1 Hz, 1H), 6.75 (d, 2H), 6.54 (d, 15.4 Hz,
1H), 4.61 (q, 4H), 3.83 (t, 2H), 3.49 (m, 4H), 2.62 (m, 4H),
2.50 (s, 3H), 1.79 (s, 1H), 1.48 (m, 8H), 1.33 (t, 6H), 1.19
(t, 3H), 1.00 (m, 6H).
C65H84N4O6S2 calcd: C 72.22%, H 7.78%, N 5.19%;
found: C 72.15%, H 7.71%, N 5.09%.
Compoundd2: Eluents:dichloromethane/ethylacetate80/20.
Compound d2: Yield: 515 mg (15%).
Mp: 226 ꢁC.
13C NMR (CDCl3, ppm): d¼176.6, 162.7, 161.6, 160.8,
156.3, 147.3, 146.7, 141.0, 139.6, 130.8, 130.0, 128.1,
127.1, 124.1, 115.1, 114.5, 111.6, 111.4, 110.2, 95.7, 59.3,
51.4, 44.6, 42.3, 32.7, 32.3, 25.8, 25.7, 21.8, 21.7, 19.7,
12.9, 12.8, 11.5, 11.0.
1H NMR (CDCl3, ppm): d¼8.26 (d, J¼1.47 Hz, 1H), 7.60 (d,
J¼16.0 Hz, 1H), 7.55 (m, 4H), 7.35 (m, 5H), 7.02 (d,
J¼15.4 Hz, 1H), 6.98 (d, J¼15.4 Hz, 1H), 6.96 (d, J¼16.0 Hz,
1H), 6.86 (d, J¼15.4 Hz, 1H), 6.85 (d, J¼15.4 Hz, 1H), 6.75
(d, 2H), 6.74 (d, 2H), 6.55 (d, J¼15.4 Hz, 1H), 6.20 (d,
J¼1.44 Hz, 1H), 6.02 (d, 15.4 Hz, 1H), 3.83 (t, 4H), 3.48 (m,
8H), 2.64 (m, 8H), 1.94 (s, 2H), 1.48 (m, 16H), 1.19 (t, 6H),
0.97 (t, 12H).
MS: m/z¼701 (Mþ).
C40H51N3O4S2 calcd: C 68.47%, H 7.28%, N 5.99%;
found: C 68.36%, H 7.19%, N 5.91%.
Compound b2: Yield: 552 mg (22%).
Mp: 266 ꢁC.
13C NMR (CDCl3, ppm): d¼173.6, 162.3, 160.5, 159.6,
148.7, 148.3, 148.2, 147.0, 141.8, 141.6, 140.6, 140.5,
132.0, 131.8, 131.5, 131.0, 129.9, 128.9, 128.1, 128.0,
125.1, 124.9, 116.4, 115.8, 115.5, 115.4, 112.5, 112.4,
108.2, 107.0, 94.2, 60.3, 52.4, 45.6, 33.7, 33.6, 33.4, 27.1,
26.7, 22.9, 22.8, 22.7, 14.1, 14.0, 12.0.
1H NMR (CDCl3, ppm): d¼8.84 (s, 2H), 7.66 (d,
J¼15.4 Hz, 2H), 7.38 (d, 4H), 7.02 (d, J¼15.7 Hz, 2H), 6.90
(d, 15.7 Hz, 2H), 6.75 (d, 4H), 6.60 (d, J¼15.4 Hz, 2H),
4.60 (q, 4H), 3.82 (t, 4H), 3.48 (m, 8H), 2.67 (m, 8H), 1.75
(s, 2H), 1.50 (m, 16H), 1.35 (t, 6H), 1.19 (t, 6H), 0.99 (m,
12H).
MS: m/z¼1057 (Mþ).
13C NMR (CDCl3, ppm): d¼177.5, 161.8, 160.9, 156.3,
148.3, 147.1, 141.7, 140.6, 132.2, 130.9, 128.3, 128.2,
125.2, 117.0, 115.5, 112.9, 112.5, 96.6, 60.3, 52.4, 45.6,
43.4, 33.7, 33.4, 27.2, 26.7, 22.8, 22.7, 14.1, 14.0, 12.6, 12.0.
MS: m/z¼1096 (Mþ).
C66H79N3O5S2 calcd: C 74.93%, H 7.47%, N 3.97%;
found: C 74.82%, H 7.40%, N 3.94%.
4.10. Synthesis of the acetate-functionalized chromophores
C65H84N4O5S3 calcd: C 71.13%, H 7.71%, N 5.10%;
found: C 71.08%, H 7.62%, N 5.07%.
The general procedure is as follows: a solution of the alco-
hol-functionalized chromophore xi (90.0 mmol) in acetic anhy-
dride (10 mL) was stirred for 14 h at room temperature. Then,
the solvent was evaporated in vacuo and the crude reaction
product was redissolved in dichloromethane and washed
with a saturated NaHCO3-solution, a saturated NaCl-solution
and dried over MgSO4. Finally, the product was purified
with column chromatography (silica gel; eluents: dichloro-
methane/ethylacetate (9/1)) and isolated as a solid.
Compounds a1eOAc: Yield: 34.6 mg (63%).
Compounds c1e2: Eluents: dichloromethane/ethylacetate
60/40.
Compound c1: Yield: 418 mg (25%).
Mp: 207 ꢁC.
1H NMR (CDCl3, ppm): d¼8.88 (d, J¼1.47 Hz, 1H), 8.69
(d, J¼1.47 Hz, 1H), 7.58 (d, J¼15.4 Hz, 1H), 7.37 (d, 2H),
7.00 (d, J¼15.7 Hz, 1H), 6.87 (d, J¼15.7 Hz, 1H), 6.75 (d,
2H), 6.53 (d, J¼15.4 Hz, 1H), 4.02 (m, 4H), 3.82 (m, 2H),
3.47 (m, 4H), 2.60 (m, 4H), 2.49 (s, 3H), 1.88 (s, 1H), 1.47
(m, 8H), 1.25 (t, 6H), 1.19 (t, 3H), 0.99 (m, 6H).
13C NMR (CDCl3, ppm): d¼163.7, 163.1, 161.7, 156.5,
150.7, 148.2, 147.1, 141.3, 140.5, 131.8, 130.7, 128.3,
128.0, 125.2, 116.6, 115.6, 112.5, 111.8, 110.4, 95.4, 60.3,
52.4, 45.6, 36.4, 33.7, 33.3, 26.8, 26.7, 22.8, 22.7, 20.6,
14.0, 13.8, 13.5, 12.0.
Mp: 116 ꢁC.
1H NMR (CDCl3, ppm): d¼7.54 (d, J¼15.4 Hz, 1H), 7.37
(d, 2H), 7.01 (d, J¼16.1 Hz, 1H), 6.89 (d, J¼16.1 Hz, 1H),
6.72 (d, 2H), 6.55 (d, J¼2.2 Hz, 1H), 6.48 (d, J¼2.2 Hz,
1H), 6.33 (d, J¼15.4 Hz, 1H), 4.22 (t, 2H), 3.59 (t, 2H),
3.45 (q, 2H), 2.61 (m, 4H), 2.37 (s, 3H), 2.06 (s, 3H), 1.45
(m, 8H), 1.20 (t, 3H), 0.97 (t, 6H).
MS: m/z¼685 (Mþ).
13C NMR (CDCl3, ppm): d¼169.9, 160.5, 158.6, 155.1,
146.6, 140.8, 139.5, 130.3, 129.9, 128.1, 127.1, 123.9,
114.5, 114.4, 113.5, 110.9, 105.1, 105.0, 60.5, 57.1, 47.7,
44.4, 32.7, 32.3, 30.9, 28.7, 25.8, 25.7, 21.8, 21.6, 19.9,
18.9, 12.9, 12.8, 11.3.
C40H51N3O5S calcd: C 70.07%, H 7.45%, N 6.13%; found:
C 70.02%, H 7.38%, N 6.05%.
Compound c2: Yield: 352 mg (14%).
Mp: 269 ꢁC.
1H NMR (CDCl3, ppm): d¼8.84 (s, 2H), 7.62 (d,
J¼15.4 Hz, 2H), 7.38 (d, 4H), 7.01 (d, J¼15.8 Hz, 2H), 6.89
(d, J¼15.8 Hz, 2H), 6.74 (d, 4H), 6.58 (d, J¼15.4 Hz, 2H),
4.05 (m, 4H), 3.83 (m, 4H), 3.49 (m, 8H), 2.65 (m, 8H), 1.84
(s, 2H), 1.50 (m, 16H), 1.27 (t, 6H), 1.19 (t, 6H), 0.99 (m, 12H).
13C NMR (CDCl3, ppm): d¼163.7, 160.2, 155.6, 150.8,
148.2, 146.5, 141.2, 140.5, 132.2, 130.6, 128.1, 127.7,
MS: m/z¼609 (Mþ).
C37H43N3O3S calcd: C 72.87%, H 7.11%, N 6.89%; found:
C 72.75%, H 7.05%, N 6.76%.
Compounds a2eOAc: Yield: 23.3 mg (37%).
Mp: 214 ꢁC.
1H NMR (CDCl3, ppm): d¼7.59 (d, J¼15.4 Hz, 2H), 7.38
(d, 4H), 7.03 (d, J¼16.1 Hz, 2H), 6.90 (d, J¼16.1 Hz, 2H),

3780
G. Koeckelberghs et al. / Tetrahedron 64 (2008) 3772e3781
6.72 (d, 4H,), 6.54 (s, 2H), 6.40 (d, J¼15.4 Hz, 2H), 4.25 (t,
4H), 3.59 (t, 4H), 3.45 (q, 4H), 2.66 (m, 8H), 2.06 (s, 6H),
1.49 (m, 16H), 1.23 (t, 6H), 0.99 (q, 12H).
Compounds c2eOAc: Yield: 32.0 mg (59%).
Mp: 218 ꢁC.
1H NMR (CDCl3, ppm): d¼8.85 (s, 2H), 7.62 (d,
J¼15.4 Hz, 2H), 7.39 (d, 4 Hz), 7.03 (d, J¼16.1 Hz, 2H),
6.90 (d, J¼16.1 Hz, 2H), 6.72 (d, 4H), 6.60 (d, J¼15.4 Hz,
2H), 4.25 (t, 4H), 4.04 (q, 4H), 3.59 (t, 4H), 3.44 (q, 4H),
2.65 (m, 8H), 2.06 (s, 6H), 1.45 (m, 16H), 1.27 (t, 6H), 1.20
(t, 6H), 0.96 (m, 12H).
13C NMR (CDCl3, ppm): d¼169.9, 157.4, 154.4, 146.6,
145.9, 140.6, 139.5, 130.1, 129.9, 127.4, 127.1, 123.9,
114.9, 114.4, 110.9, 105.2, 60.5, 56.5, 47.7, 44.4, 32.6, 32.4,
28.7, 26.1, 25.7, 21.9, 21.7, 19.9, 13.1, 12.9, 11.3.
MS: m/z¼1046 (Mþ).
C64H78N4O5S2 calcd: C 73.39%, H 7.51%, N 5.35%;
found: C 73.28%, H 7.46%, N 5.25%.
Compounds b1eOAc: Yield: 41.9 mg (70%).
13C NMR (CDCl3, ppm): d¼169.9, 162.7, 159.2, 154.6,
149.8, 146.6, 145.5, 140.2, 139.5, 131.2, 129.6, 127.1,
126.6, 124.1, 123.6, 116.4, 114.5, 111.1, 110.9, 94.3, 60.5,
47.8, 44.3, 35.4, 32.6, 32.3, 28.2, 26.2, 25.7, 21.8, 19.9,
13.1, 13.0, 12.6, 11.3.
Mp: 176 ꢁC.
1H NMR (CDCl3, ppm): d¼8.89 (d, J¼1.8 Hz, 1H), 8.70
(d, J¼1.8 Hz, 1H), 7.60 (d, 1H), 7.36 (d, 2H), 7.00 (d,
J¼15.4 Hz, 1H), 6.88 (d, J¼15.4 Hz, 1H), 6.71 (d, 2H), 6.53
(d, J¼15.4 Hz, 1H), 4.57 (q, 4H), 4.24 (t, 2H), 3.58 (t, 2H),
3.43 (q, 2H), 2.61 (m, 4H), 2.49 (s, 3H), 2.05 (s, 3H), 1.44
(m, 8H), 1.32 (t, 6H), 0.98 (m, 6H).
MS: m/z¼1164 (Mþ).
C69H88N4O8S2 calcd: C 71.10%, H 7.61%, N 4.81%;
found: C 70.99%, H 7.50%, N 4.69%.
Compounds d2eOAc: Yield: 22.0 mg (38%).
Mp: 168 ꢁC.
13C NMR (CDCl3, ppm): d¼169.9, 157.4, 154.4, 146.6,
145.9, 140.6, 139.5, 130.1, 129.9, 127.4, 127.1, 123.9,
114.9, 114.4, 110.9, 105.2, 60.5, 56.5, 47.7, 44.4, 32.6, 32.4,
28.7, 26.1, 25.7, 21.9, 21.7, 19.9, 13.1, 12.9, 11.3.
MS: m/z¼1046 (Mþ).
1H NMR (CDCl3, ppm): d¼8.30 (d, J¼2.2 Hz, 1H), 7.59 (d,
J¼15.4 Hz, 1H), 7.54 (m, 4H), 7.37 (m, 5H), 7.03 (d,
J¼16.1 Hz, 1H), 7.00 (d, J¼16.1 Hz, 1H), 6.99 (d, J¼15.4 Hz,
1H), 6.93 (d, J¼16.1 Hz, 1H), 6.88 (d, J¼16.1 Hz, 1H), 6.72
(d, 4H), 6.57 (d, J¼15.4 Hz, 1H), 6.20 (d, J¼2.2 Hz, 1H), 6.03
(d, J¼15.4 Hz, 1H), 4.25 (t, 4H), 3.59 (t, 4H), 3.45 (q, 4H),
2.65 (m, 8H), 2.06 (s, 6H), 1.47 (m, 16H), 1.20 (t, 6H), 0.96
(m, 12H).
C42H53N3O5S2 calcd: C 67.80%, H 7.18%, N 5.65%;
found: C 67.71%, H 7.11%, N 5.54%.
Compounds b2eOAc: Yield: 26.0 mg (44%).
Mp: 188 ꢁC.
13C NMR (CDCl3, ppm): d¼173.5, 171.0, 162.3, 160.4,
159.5, 148.6, 147.7, 146.9, 141.7, 141.5, 140.6, 140.5, 132.0,
131.5, 130.9, 130.8, 129.8, 128.9, 128.8, 128.2, 128.1, 125.0,
124.9, 116.4, 115.9, 115.4, 111.9, 108.2, 107.0, 94.4, 61.5,
61.4, 48.8, 45.4, 33.6, 33.4, 29.7, 29.4, 27.1, 26.7, 22.8, 22.7,
20.9, 14.0, 12.3.
1H NMR (CDCl3, ppm): d¼8.84 (s, 2H), 7.68 (d,
J¼15.4 Hz, 2H), 7.39 (d, 4H), 7.03 (d, J¼15.7 Hz, 2H), 6.96
(d, J¼15.7 Hz, 2H), 6.72 (d, 4H), 6.60 (d, J¼15.4 Hz, 2H),
4.60 (q, 4H), 4.25 (t, 4H), 3.59 (t, 4H), 3.44 (q, 4H), 2.65
(m, 8H), 2.06 (s, 6H), 1.44 (m, 16H), 1.36 (t, 6H), 1.20 (t,
6H), 0.96 (t, 6H).
MS: m/z¼1142 (Mþ).
13C NMR (CDCl3, ppm): d¼176.5, 169.9, 160.8, 159.9,
155.3, 146.6, 146.0, 140.7, 139.6, 131.1, 129.9, 127.3,
127.2, 124.0, 116.0, 114.4, 112.0, 110.9, 95.6, 60.5, 47.7,
44.4, 42.3, 32.7, 32.3, 30.9, 28.7, 28.6, 28.3, 26.2, 25.7,
21.8, 21.7, 19.9, 13.0, 12.9, 11.6, 11.3.
C70H83N3O7S2 calcd: C 73.59%, H 7.32%, N 3.68%;
found: C 73.45%, H 7.25%, N 3.58%.
Acknowledgements
MS: m/z¼1180 (Mþ).
This work was supported by the Fund for Scientific Re-
search-Flanders (FWO-Vlaanderen), the Katholieke Universi-
teit Leuven (GOA) and the Belgian Government (IUAP). G.K.
and I.A. are postdoctoral fellows of the Fund for Scientific
Research (FWO-Vlaanderen).
C69H88N4O7S3 calcd: C 70.14%, H 7.51%, N 4.74%;
found: C 69.98%, H 7.37%, N 4.66%.
Compounds c1eOAc: Yield: 32.0 mg (54%).
Mp: 119 ꢁC.
1H NMR (CDCl3, ppm): d¼8.89 (d, J¼2.2 Hz, 1H), 8.70
(d, J¼2.2 Hz, 1H), 7.58 (d, J¼15.4 Hz, 1H), 7.38 (d, 2H),
7.01 (d, J¼15.4 Hz, 1H), 6.88 (d, J¼15.4 Hz, 1H), 6.72 (d,
2H), 6.53 (d, J¼15.4 Hz, 1H), 4.25 (t, 2H), 4.02 (m, 2H),
3.59 (t, 2H), 3.44 (q, 2H), 2.60 (m, 4H), 2.47 (s, 3H), 2.06
(s, 3H), 1.45 (m, 8H), 1.25 (t, 6H), 1.20 (t, 3H), 0.99 (m, 6H).
13C NMR (CDCl3, ppm): d¼169.9, 162.7, 162.1, 160.7,
155.5, 149.7, 146.6, 146.1, 140.3, 139.4, 130.8, 129.6,
127.3, 127.1, 124.0, 115.6, 114.5, 110.9, 110.8, 109.3, 94.4,
60.5, 47.8, 44.3, 35.4, 32.7, 32.3, 28.7, 25.8, 25.7, 21.8,
21.7, 19.9, 19.6, 12.9, 12.8, 12.5, 11.3.
References and notes
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C42H53N3O6S calcd: C 69.30%, H 7.34%, N 5.77%; found:
C 69.18%, H 7.28%, N 5.62%.

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