An efficient microwave-assisted enzyme-catalyzed regioselective synthesis of long chain acylated derivatives of flavonoid glycosides

Article abstract of DOI:10.1016/j.tetlet.2013.01.103

This work describes a method of microwave-assisted regioselective enzymatic acylation, using Novozyme 435, of quercetin-3-O-glucoside (isoquercitrin) and phloretin-20-glucoside (phloridzin) with different long chain saturated, mono-, and poly-unsaturated fatty acids. The synthesized esters were analyzed by 1H NMR, and 13C NMR spectroscopy. In this investigation, microwave irradiation under solvent free condition has been found to be more efficient and economical than conventional conditions both, in terms of time and energy.

Full text of DOI:10.1016/j.tetlet.2013.01.103

Tetrahedron Letters 54 (2013) 1933–1937
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
An efficient microwave-assisted enzyme-catalyzed regioselective synthesis
of long chain acylated derivatives of flavonoid glycosides
⇑
Ziaullah, H. P. Vasantha Rupasinghe
Department of Environmental Sciences, Faculty of Agriculture, Dalhousie University, 50 Pictou Road, Truro, Nova Scotia, Canada B2N 5E3
a r t i c l e i n f o
a b s t r a c t
Article history:
This work describes a method of microwave-assisted regioselective enzymatic acylation, using Novo-
zyme 435Ò, of quercetin-3-O-glucoside (isoquercitrin) and phloretin-20-glucoside (phloridzin) with dif-
ferent long chain saturated, mono-, and poly-unsaturated fatty acids. The synthesized esters were
analyzed by 1H NMR, and 13C NMR spectroscopy. In this investigation, microwave irradiation under sol-
vent free condition has been found to be more efficient and economical than conventional conditions
both, in terms of time and energy.
Received 25 December 2012
Revised 21 January 2013
Accepted 24 January 2013
Available online 9 February 2013
Keywords:
Isoquercitrin
Ó 2013 Elsevier Ltd. All rights reserved.
Phloridzin
Acylation
Microwave irradiation
Candida antartica lipase B
1H NMR
13C NMR spectroscopy
Introduction
heating denatures the enzymes. With the emergence of modern
MW technology a safer and lower temperature can be achieved
Microwave irradiation (wavelength range: 1 mm–25
l
m) has
precisely under which enzymes are stable and can be used for
synthetic application effectively.10 The synergism between micro-
waves and immobilized enzyme catalysis, to increase reaction rate,
has been suggested in few reports.11–14 Studies have also demon-
strated the significance of microwave irradiation in organic synthe-
sis, especially in the preparation of heterocycles, organometallics,
and rearrangement reactions.15–21 The theory of microwave dielec-
tric heating, the relevant dielectric parameters, and microwave-
assisted organic reactions have been recently reviewed.22–26 Chen
and his coworkers used microwaves to accelerate the hydrolysis
of peptides and proteins.27 Bose and his coworkers have reported
the use of microwaves for the robust and selective enzymatic
digestion of several proteins in aqueous solutions.28 They also have
designed a microwave enhanced modification of the Akabori
reaction, used for the detection and identification of the car-
boxyl-terminal amino acid residue of peptides and the sequence
of some peptides with amino terminus.29 Thus, it was thought to
investigate some enzyme-catalyzed transformations of medici-
nally useful natural products like flavonoids, under microwave
irradiations.
become an effective tool in synthetic organic chemistry and green
chemistry during the last three decades due to its dramatic effects
in increasing reaction rates and yields.1–4 The reactions that re-
quire several hours under conventional conditions can often be
completed in few minutes with very high yields by this environ-
mentally benign, clean, efficient, and convenient technology. In
general, microwave irradiation enables reactions by coupling with
polar molecules and creates special vibrational effects which are
independent of the reaction temperature. This makes those reac-
tions possible which cannot proceed by thermal heating alone.4
Microwave irradiation, an electromagnetic field of high frequency
(2.45 GHz), in principle, induces molecular rotation resulting from
dipole alignment with the external, oscillating electric field, which
is accompanied by intermolecular friction and subsequent genera-
tion of heat energy.5–7 This results in a significant impact of micro-
waves on molecules with high dipole moments. Thus proteins and
peptides may be especially susceptible to microwave irradiation
due to their significant dipole moments.8,9
The application of microwave irradiation in enzyme catalysis is
relatively limited since high temperature generated by microwave
Flavonoids have been receiving attention in medicinal biochem-
istry not only due to their structural diversity, but also as natural
therapeutics and drug candidate molecules for treating chronic
diseases.30 These polyhydroxylated phenolic compounds have
been discovered to have a variety of biological activities, which
⇑
Corresponding author. Tel.: +1 902 893 6623; fax: +1 902 893 1404.
E-mail addresses: vrupasinghe@dal.ca, vrupasinghe@gmail.com (H.P. Vasantha
Rupasinghe).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.01.103

1934
Ziaullah, H. P. Vasantha Rupasinghe / Tetrahedron Letters 54 (2013) 1933–1937
include antibiotic, anti-viral, anti-diarrheic, anti-inflammatory,
anti-spasmolytic, anti-allergenic, vasodilatory, anti-tumor, and
anti-ulcer properties.30–35
OH
OH
OH
OH
HO
O
HO
O
It is these health benefits which have garnered their ever
increasing use in many cosmetics, food ingredients, and pharma-
ceuticals. However, these applications are significantly limited
due to the poor solubility of flavonoids in both hydrophobic and
hydrophilic media.36 It is therefore of utmost importance to design
new derivatives of flavonoids with amphipathic properties by sim-
ple, effective, and environmentally friendly method.
Previously, regioselective chemical and chemo-enzymatic acyl-
ation of phenolic compounds with various acyl donors (C2–C18
chain length) under conventional conditions has already been doc-
umented.37–45 However, our present investigation provides an effi-
cient approach for lipase-catalyzed acylation of the isoquercitrin
and phloridzin, using very long chain unsaturated and saturated
fatty acids (C18–C22), with Novozyme 435Ò as the catalytic en-
zyme by using the emerging technology of microwave irradiation.
Our current study has been supported by detailed NMR structural
assignments of all the synthesized compounds.
i or ii or iii
RCOOH
O
+ H2O
O
O
OH
O
OH
HO
HO
O
O
OH
OH
OR
HO
HO
OH
OH
2-7
1
OH
HO
OH
HO
OH
O
i or ii or iii
+ H2O
O
O
O
RCOOH
HO
HO
HO
HO
O
O
OH
OR
HO
HO
Results and discussion
8
9-14
Scheme 1. Reagents and conditions: (i) Acetone, 4 Å molecular sieves, Novozyme
435Ò, 45–60 °C, stirring, 18–24 h. (ii) Acetone, 4 Å molecular sieves, Novozyme
Acylation of isoquercitrin and phloridzin with fatty acids (C18–
C22) was carried out at 45–60 °C in extra dry acetone or acetonitrile
along with constant stirring. Enzymatic reactions were initiated by
the addition of lipase (Novozyme 435Ò; with an activity of 10,000
propyl laurate units; from Sigma-Aldrich (Mississauga, ON, Canada)
followed by the addition of defined quantities of flavonoids and
fatty acids in acetone in the conventional method as well as in
microwave-assisted solution phase microwave irradiation. While
under microwave-assisted solvent free conditions, no solvent was
used during the reaction. In the current study, the highest efficiency
was achieved under microwave irradiation in the solvent free
method (within the enzyme thermal optimum range (45–60 °C),
while using molecular sieves (4 Å) to remove in situ generated
water in the reaction mixture (Scheme 1; Table 1). All the reactions
were performed in microwave reactor (CEM Focused Microwave
Synthesis, Model Discover, CEM Co., Matthew, NC, USA).
Among enzymes, lipases are the widely utilized enzymes that
have broader substrate specificity. They catalyze esterification,
transesterification, thioesterification, hydrolysis, amidation etc.46
Previous studies have shown that enzymes in general do not deac-
tivate or denature under microwave irradiation within their opti-
mum temperature range.47 In our case the lipase (Novozyme
435Ò) also showed stability within the enzyme thermal optimum
range of 45–60 °C. We reused this enzyme two times after proper
washing and drying but neither it get deactivated nor denatured.
In the microwave-assisted solution phase method, the reactions
completed in just 120–160 s which took 18–24 h in the conven-
tional method of heating (Tables 1 and 2). This shorter reaction
time showed a significant increase in the rate of reaction. However,
no significant difference in the percentage yield was noticed. This
indicated some degree of synergism between the enzyme and
microwave irradiation.
435Ò, 45–60 °C, microwave irradiation, 120–160 s. (iii) Novozyme 435Ò
,
4 Å
molecular sieves, 45–60 °C, microwave irradiation, 75–105 s. R = Oleic, Stearic,
Linoleic,
esters.
a-Linolenic, Eicosapentaenoic (EPA), Docosahexaenoic Acids (DHA) or their
alternative method for enzyme-catalyzed regioselective acylation
of flavonoid glycosides with long chain fatty acids.
Most of the enzymes have highly compact structures and lim-
ited conformational flexibility but due to the presence of polar
groups they can be exploited by microwave irradiation. The ob-
served specific microwave effects are most likely derived from
molecular motion induced by a rapid dipole alignment of the pep-
tide bonds with the oscillating electric field. The strong induction
of molecular motion in the enzyme through microwave irradiation
is reflected by the observation that high microwave power (300 W)
at moderate temperatures led to an optimum activity of Novozyme
435Ò. However, during optimization of this method we noticed
that the enzyme activity decreases substantially and then dimin-
ishes when the temperature crosses certain threshold range (75–
95 °C) which probably lead to a loss of tertiary structure or resulted
in complete denaturation of the enzyme.
The results reported here illustrate that microwaves could be
used to trigger biocatalytic rates of Novozyme 435Ò within its ther-
mal optimum range (45–60 °C).
Effect on regioselectivity
In microwave-assisted synthesis of flavonoid esters of fatty
acids, the reaction follows the same course of regioselectivity as
is followed in the conventional method. The esters prepared by
all the above three methods were evaluated and confirmed by 1H
and 13C NMR assignments. The location of the acylated site re-
ported in the literature is in agreement with our studies.48–50 The
newly synthesized products were confirmed by comparing the
downfield or upfield shifts between their structural assignments
and the reported isoquercitrin and phloridzin.51 13C NMR spectra
showed that the acylation on the 600-OH position led to a downfield
shift of the C-600 signal by approximately 3 ppm (approximately
60.94 to 63.80 ppm) due to the resonance effect toward carbonyl
of the newly generated ester as well as an upfield shift of the
In case of microwave-irradiated solvent free reactions, the reac-
tion time decreased even further and completed in 75–105 s (Ta-
ble 2). Again, no significant difference in the percentage yield
was noticed. The secondary enzymatic hydrolysis of the product
was minimized by adding flame dried 4 Å molecular sieves.
In all these three methods, yields are in the range of 82–98%
(Table 2). The microwave-assisted, biocatalytic, solvent-free reac-
tion route was found to be the most effective among these meth-
ods with a significant increase in the reaction rate. These results
showed that microwave irradiation is
a fast and efficient

Ziaullah, H. P. Vasantha Rupasinghe / Tetrahedron Letters 54 (2013) 1933–1937
1935
Table 1
Reaction time and yield for the two series of isoquercitrin and phloridzin esters
Compound
Conventional method
Time (h) Yield (%)
MW solution phase
MW dry media
Time (s)
Yield (%)
Time (s)
Yield (%)
2
3
4
5
6
7
9
10
11
12
13
14
18
20
20
24
24
24
20
20
22
24
24
24
97
92
94
91
81
81
98
96
93
94
85
82
120
120
120
150
150
160
130
130
150
160
160
160
98
92
94
93
84
85
98
97
93
94
85
84
75
75
75
90
90
90
75
75
90
90
105
105
98
94
95
93
87
88
98
98
94
95
88
85
Table 2
Compounds 2–7 and 9–14
OH
OH
OH
HO
OH
O
O
HO
O
O
O
OH
HO
HO
O
HO
O
HO
OH
OH
OR
OR
2-7
9-14
Compounds
R
2/9
O
3/10
4/11
O
O
5/12
6/13
7/14
O
O
O
OH
3'
OH
4'
2'
OH
4'
5'
3'
6'
2'
1'
5
HO
6 OH
4
5'
1
8
1'
2
β
O
HO
7
6'
α
3
1
3
2
6
O
O
4
O
5
O
OH
1''
2''
HO
3''
1''
HO 2''
O
O
5''
3''
HO
4''
HO
6''
5''
OH
4''
OH
2''' 4''' 6''' 8'''
10'''
16'''
12'''
14'''
2'''
6'''
4'''
8'''
10'''
16'''
12'''
18'''
14'''
O
O
O
O
2
9
Figure 1. Numbering of the esters of isoquercitrin (2) and phloridzin (9).

1936
Ziaullah, H. P. Vasantha Rupasinghe / Tetrahedron Letters 54 (2013) 1933–1937
C-1000 (OCO) signal by approximately 3–4 ppm from their corre-
sponding fatty acids (Fig. 1).51,52
30. (a) Rice-Evans, C. A.; Miller, N. J.; Paganga, G. Free Radical Biol. Med. 1996, 20,
933; (b) Thilakarathna, S. H.; Rupasinghe, H. P. V. Can. J. Plant Sci. 2012, 92, 407;
(c) Balasuriya, N.; Rupasinghe, H. P. V. Food Chem. 2012, 135, 2320.
31. Formica, J. V.; Regelson, W. Food Chem. Toxicol. 1995, 33, 1061.
32. Harborne, J. B.; Williams, C. A. Phytochemistry 2000, 55, 481.
33. Hossion, A. M. L.; Otsuka, N.; Kandahary, R. K.; Tsuchiya, T.; Ogawa, W.; Iwado,
A.; Zamami, Y.; Sasaki, K. Bioorg. Med. Chem. Lett. 2010, 20, 5349.
34. Lee, K. Med. Res. Rev. 1999, 19, 569.
35. Tijburg, L. B. M.; Mattern, T.; Folts, J. D.; Weisgerber, U. M.; Katan, M. B. Crit.
Rev. Food Sci. Nutr. 1997, 37, 771.
36. Mellou, F.; Loutrari, H.; Stamatis, H.; Roussos, C.; Kolisis, F. N. Process Biochem.
2006, 41, 2029.
37. (a) Hilt, P.; Schieber, A.; Yildrim, C.; Arnold, G.; Klaiber, I.; Conrad, J.; Beifuss, U.;
Carle, R. J. Agric. Food Chem. 2003, 51, 2896; (b) Salem, J. H.; Humeau, C.;
Chevalot, I.; Harscoat-Schiavo, C.; Vanderesse, R.; Blanchard, F.; Fick, M. Process
Biochem. 2010, 45, 382; (c) Aursand, M.; Grasdalen, H. Chem. Phys. Lipids 1992,
62, 239.
38. Stevenson, D. E.; Wibisono, R.; Jensen, D. J.; Stanley, R. A.; Cooney, J. M. Enzyme
Microb. Technol. 2006, 39, 1236.
39. Ardhaoui, M.; Falcimaigne, A.; Ognier, S.; Engasser, J. M.; Moussou, P.; Pauly, G.;
Ghoul, M. J. Biotechnol. 2004, 110, 265.
Conclusion
Microwave is an emerging technology which provides an alter-
native energy to accomplish enzymatic reactions. In enzymes,
where polar groups such as OH and NH2 are present and can absorb
the microwave energy. Consequently, enzyme activity, selectivity,
and stability can be modified by microwave heating. In previous
reports some authors have envisioned the existence of a specific ef-
fect of the microwave irradiation on the structure and activities of
enzymes. The microwave energy directly transfers between the
electromagnetic field and the polar structural profile which could
induce flexibility in the enzyme, and results in the change of the
enzymatic properties.53,54 In addition, a direct absorption of the
microwave irradiation by the polar substrates of the enzyme could
lead to a higher reactivity of the functional groups involved in the
enzymatic reaction.55 Thus, our present investigation revealed that
the microwave heating appeared to be a promising technology to
improve the biocatalytic sector.
40. Lue, B.-M.; Guo, Z.; Xu, X. Process Biochem. 2010, 45, 1375.
41. Gao, C.; Mayon, P.; MacManus, D. A.; Vulfson, E. N. Biotechnol. Bioeng. 2000–
2001, 71, 235.
42. Kontogianni, A.; Skouridou, V.; Sereti, V.; Stamatis, H.; Kolisis, F. N. Eur. J. Lipid
Sci. Technol. 2001, 103, 655.
43. Mellou, F.; Lazari, D.; Skaltsa, H.; Tselepis, A. D.; Kolisis, F. N.; Stamatis, H. J.
Biotechnol. 2005, 116, 295.
44. Yang, Z.; Pan, W. Enzyme Microb. Technol. 2005, 37, 19.
45. Rantwijk, F. V.; Sheldon, R. A. Chem. Rev. 2007, 107, 2757.
46. Kidwai, M.; Poddar, R. Catal. Lett. 2008, 124, 311.
Acknowledgements
47. Réjasse, B.; BessonEn, T.; Legoy, M.-D.; Lamare, S. Org. Biomol. Chem. 2006, 4,
3703.
We would like to thank the Discovery Grant of the Natural
Sciences and Engineering Council (NSERC) of Canada and the
Atlantic Innovation Funds (AIF) program of the Atlantic Canada
Opportunities Agency for financial support.
48. (a) Hilt, P.; Schieber, A.; Yildrim, C.; Arnold, G.; Klaiber, I.; Conrad, J.; Beifuss, U.;
Carle, R. J. Agric. Food Chem. 2003, 51, 2896; (b) Salem, J. H.; Humeau, C.;
Chevalot, I.; Harscoat-Schiavo, C.; Vanderesse, R.; Blanchard, F.; Fick, M. Process
Biochem. 2010, 45, 382; (c) Aursand, M.; Grasdalen, H. Chem. Phys. Lipids 1992,
62, 239.
49. Enaud, E.; Humeau, C.; Piffaut, B.; Girardin, M. J. Mol. Catal. B: Enzym. 2004,
27, 1.
References and notes
50. Chebil, L.; Anthoni, J.; Humeau, C.; Gerardin, C.; Engasser, J.-M.; Ghoul, M. J.
Agric. Food Chem. 2007, 55, 9496.
51. (a) Ziaullah; Bhullar, K. S.; Warnakulasuriya, S. N.; Rupasinghe, H. P. V. Bioorg.
Med. Chem. 2013, 21, 684; (b) Vatèle, J.-M.; Fenet, B.; Eynard, T. Chem. Phys.
Lipids 1998, 94, 239.
1. Kappe, C. O.; Dallinger, D. Mol. Diversity 2009, 13, 71.
2. Loupy, A. Microwaves in Organic Synthesis, 2nd ed.; Wiley-VCH: Weinheim,
Germany, 2006.
3. (a) Kappe, C. O. Angew. Chem., Int. Ed. 2004, 43, 6250; (b) Kappe, C. O.
Microwaves in Organic and Medicinal Chemistry; Wiley-VCH: Weinheim,
Germany, 2005; (c) Larhed, M.; Moberg, C.; Hallberg, A. Acc. Chem. Res. 2002,
35, 717.
4. Hayes, B. L. Microwave Synthesis: Chemistry at the Speed of Light; CEM
Publishing: Matthews, NC, 2003.
5. Mingos, D. M. P.; Baghurst, D. R. Chem. Soc. Rev. 1991, 20, 1.
6. Herrero, M. A.; Kremsner, J. M.; Kappe, C. O. J. Org. Chem. 2008, 73, 36.
7. Hayes, B. L. Aldrichim. Acta 2004, 37, 66.
8. Collins, J. M.; Leadbeater, N. E. Org. Biomol. Chem. 2007, 5, 1141.
9. Rejasse, B.; Lamare, S.; Legoy, M. D.; Besson, T. J. Enzyme Inhib. 2007, 22, 518.
10. Rejasse, B.; Lamare, S.; Legoy, M. D.; Besson, T. J. Enzyme Inhib. Med. Chem. 2007,
22, 518.
11. Parker, M. C.; Besson, T.; Lamare, S.; Legoy, M. D. Tetrahedron Lett. 1996, 37,
8383.
12. Yadav, G. D.; Lathi, P. Synth. Commun. 2005, 35, 1699.
13. Yadav, G. D.; Sajgure, A. D.; Dhoot, S. B. In Enzyme Mixtures and Complex
Biosynthesis; Bhattacharya, S. K., Ed.; Landes Biosciences: Austin, TX, 2007.
14. Austin, Y. D.; Tian, L.; Ma, D.; Wu, H.; Wang, Z.; Wang, L.; Fang, X. Green Chem.
2010, 12, 844.
15. Lidstrom, P.; Tierney, J.; Wathey, B.; Westman, J. Tetrahedron 2001, 57, 9225.
16. Larhed, M.; Hallberg, A. Drug Discovery Today 2001, 6, 406.
17. Elander, N.; Jones, J. R.; Lu, S. Y.; Stone-Elander, S. Chem. Soc. Rev. 2000, 29, 239.
18. Suarez, M.; Loupy, A.; Salfran, E.; Moran, L.; Rolando, E. Heterocycles 1999, 51,
21.
52. Typical procedure for the synthesis of saturated/unsaturated fatty acid esters
of isoquercitrin (2–7) and phloridzin (9–14): Conventional method: To a flame
dried round bottomed flask with flame dried 4 Å molecular sieves were added
isoquercitrin (100 mg; 0.22 mmol), stearic acid (310 mg, 1.08 mmol),
Novozyme 435Ò (300 mg) followed by the addition of dry acetone (5 ml).
The mixture was heated for 24 h at 45 °C. The reaction was monitored by thin
layer chromatography under UV light followed by staining with anisaldehyde
spray reagent and then heating at 110 °C. After completion of reaction, it was
filtered, evaporated, and passed through column chromatography (acetone/
toluene; 35:75 to 45:55) to get the pure esters of isoquercitrin or phloridzin
(compounds 2–7 or 9–14) with yields in the range of 82–98%. The pure
compounds were then analyzed by 1H NMR and 13C NMR spectroscopy.51 All
other compounds were prepared by the same method.
Microwave-assisted solution phase method: To a flame dried round bottomed
flask with flame dried 4 Å molecular sieves, were added isoquercitrin (100 mg;
0.22 mmol), stearic acid (310 mg, 1.08 mmol), Novozyme 435Ò (300 mg)
followed by the addition of dry acetone (4 ml). The mixture was irradiated
for 120–160 s in 12–16 intervals (10–20 s each interval) in a CEM monomode
microwave reactor, with an operating frequency of 2.5 GHz and a maximum
power of 300 W, having
a noncontact infrared temperature sensor. The
temperature of the reaction was maintained at 45–60 °C and was monitored
by thin layer chromatography (TLC). After completion of reaction, it was
filtered, evaporated, and passed through column chromatography to get the
pure esters of isoquercitrin or phloridzin (Table 2). The purified compounds
were analyzed by 1H NMR and 13C NMR spectroscopy. All other compounds
were prepared by the same method.
19. Loupy, A.; Regnier, S. Tetrahedron Lett. 1999, 40, 6221.
20. Olofsson, K.; Kim, S. Y.; Larhed, M.; Curran, D. P.; Hallberg, A. J. Org. Chem. 1999,
64, 4539.
Microwave-assisted solvent free method: In a flame dried vial, isoquercitrin
(100 mg; 0.22 mmol) and stearic acid (310 mg, 1.08 mmol) were dissolved in
minimum amount of acetone and impregnated on immobilized Novozyme
435Ò (300 mg) followed by evaporation of the solvent under vacuum. Flame
dried molecular sieves (4 Å) were added to this loaded dry mixture and was
irradiated under microwave wave for sufficient interval of time (approximately
75–105 s in 5–7 intervals (15 s each) and temperature was maintained at 45–
60 °C (Table 2). The progress of reaction was monitored by TLC. After
completion of the reaction, dry acetone was added and it was filtered,
evaporated, and purified by column chromatography in the same way as
mentioned above. All other compounds were prepared by the same procedure.
Spectroscopic data-compound (2): Yield: 97–98%. Brownish green solid. Rf: 0.42
(acetone/toluene; 1:1: few drops of AcOH). IR (KBr) cmꢀ1: 3447, 3273, 3069,
3004, 2931, 2851, 2556, 2252, 2124, 1998, 1832, 1765, 1657, 1456, 1368, 1306,
1205, 1173, 1058, 931, 823, 757, 733, 623. 1H NMR (DMSO-d6, 300 MHz): d
21. Orru, R. V. A.; de Greef, M. Synth. Stuttg. 2003, 1471.
22. Nuchter, M.; Ondruschka, B.; Bonrath, W.; Gum, A. Green Chem. 2004, 6, 128.
23. Gabriel, C.; Gabriel, S.; Grant, E. H.; Halstead, B. S. J.; Mingos, D. M. P. Chem. Soc.
Rev. 1998, 27, 213.
24. Gedye, R. N.; Wei, J. B. Can. J. Chem. 1998, 76, 525.
25. Langa, F.; DelaCruz, P.; DelaHoz, A.; DiazOrtiz, A.; DiezBarra, E. Contemp. Org.
Synth. 1997, 4, 373.
26. Loupy, A.; Petit, A.; Hamelin, J.; Texier-Boullet, F.; Jacquault, P.; Mathe, D. Synth.
Stuttg. 1998, 1213.
27. Chen, S.-T.; Chiou, S.-H.; Wang, K.-T. J. Chin. Chem. Soc. 1991, 38, 85.
28. Bose, A. K.; Ing, Y. H.; Lavlinskaia, N.; Sareen, C.; Pramanik, B. N.; Bartner, P. L.;
Liu, Y. H.; Heimark, L. J. Am. Soc. Mass Spectrom. 2002, 13, 839.
29. Pramanik, B. N.; Mirza, U. A.; Ing, Y. H.; Liu, Y. H.; Bartner, P. L.; Weber, P. C.;
Bose, M. K. Protein Sci. 2002, 11, 2676.

Ziaullah, H. P. Vasantha Rupasinghe / Tetrahedron Letters 54 (2013) 1933–1937
1937
10.62-8.97 (br.s, 2H, ArOH), 7.56 (br s, 2H, H-20, H-60), 6.86 (br s, 1H, H-50), 6.41
(s, 1H, H-8), 6.22 (s, 1H, H-6), 5.47–5.26 (m, 3H, H-100, 2OH), 4.20 (br d, 1H,
J = 10.5 Hz, H-6a00), 4.00 (br s, 1H, H-6b00), 3.55–3.20 (m, 5H, H-200, H-300, H-400,
H-500, OH), 2.00 (br s, 2H, H-2000, OH), 1.24-1.09 (m, 31H, 15ꢁCH2, OH), 0.83 (br
s, 3H, CH3). 13C NMR (DMSO-d6, 75 MHz): d 178.14 (CO), 173.09 (OCO), 165.09
(C-7), 162.09 (C-5), 157.16 (C-2, C-9), 149.25 (C-40), 145.59 (C-30), 133.97 (C-3),
122.010 9 (C-10), 121.95 (C-60), 116.98 (C-50), 115.90 (C-20), 104.66 (C-10), 101.73
(C-1 ), 99.47 (C-6), 94.21 (C-8), 77.26 (C-300), 75.01 (C-500), 74.79 (C-200), 71.01
(C-400), 63.78 (C-600), 34.00 (C-2000), 31.99 (C-16000), 29.73 29.37, 29.23, 29.06 (C-
4000, C-5000, C-6000, C-7000, C-8000, C-9000, C-10000, C-11000, C-12000, C-13000, C-14000, C-15000),
24.95 (C-3000), 22.74 (C-17000), 14.51 (C-18000).
2OH), 5.05 (d, 1H, H-100), 4.35 (br d, 1H, J = 11.6 Hz, H-6a00), 4.14 (dd, 1H,
J = 11.6 Hz, 6.9 Hz, H-6b00), 3.65 (br t, J = 7.2 Hz, H-400), 3.46–3.20 (m, 6H,
2 ꢁ Ha, H-200, H-300, H-500, OH), 2.81 (br t, 2H, J = 7.5 Hz, 2 ꢁ Hb), 2.30 (t, 2H,
J = 7.2 Hz, 2 ꢁ H-2000), 1.49 (m, 2H, 2 ꢁ H-3000), 1.25–1.19 (m, 28H, 2(CH2)), 0.87
(br t, 3H, J = 6.9 Hz, CH3). 13C NMR (DMSO-d6, 75 MHz): d 205.32 (CO), 173.43
(OCO), 166.06 (C-40), 165.13 (C-60), 161.30 (C-20), 156.03 (C-4), 132.25 (C-1),
129.72 (C-2, C-6), 115.74 (C-3, C-5), 106.18 (C-10), 101.55 (C-100), 97.79 (C-300),
95.44 (C-500), 77.30 (C-300), 74.77 (C-500), 73.94 (C-200), 70.68 (C-400), 63.81 (C-600),
45.61 (Ca), 34.17 (C-2000), 31.96 (Cb), 29.84, 29.34, 29.13 (C-4000, C-5000, C-6000, C-
7000, C-8000, C-9000, C-10000, C-11000, C-12000, C-13000, C-14000, C-15000, C-16000), 25.08 (C-
3000), 22.73 (C-17000), 14.53 (C-18000).
Spectroscopic data-compound (9): Yield: 98%. Light yellow solid; Rf: 0.53
(acetone/toluene; 4/6: few drops of AcOH). IR (KBr) cmꢀ1: 3383, 2944, 2832,
2523, 2247, 2043, 1719, 1631, 1591, 1512, 1450, 1269, 1113, 1028, 913, 737,
652. 1H NMR (DMSO-d6, 300 MHz): d 10.61 (s, 1H, ArOH), 9.17 (br s, 1H, ArOH),
7.05 (d, 2H, J = 8.4 Hz, H-2, H-6), 6.66 (d, 2H, J = 8.4 Hz, H-3, H-5), 6.12 (d, 1H,
J = 1.8 Hz, H-30), 5.97 (d, 1H, J = 1.8 Hz, H-50), 5.44 (br s, 1H, OH), 5.38 (br s, 2H,
53. La Cara, F.; d’Auria, S.; Scarfi, M. R.; Zeni, O.; Massa, R.; d’Ambrioso, G.;
Franceschetti, G.; De Rosa, M.; Rossi, M. Protein Pept. Lett. 1999, 6, 155.
54. Ponne, C. T.; Bartels, P. V. Radiat. Phys. Chem. 1995, 45, 591.
55. Mazumder, S.; Laskar, D. D.; Prajapati, D.; Roy, M. K. Chem. Biodivers. 2004, 1,
925.