C-Furyl glycosides, I: Synthesis and antimicrobial evaluation of C-furyl glycosides and chalcones derived therefrom

Article abstract of DOI:10.1007/s00706-008-0941-1

New C-furyl glycosides were synthesized in order to increase the number of compounds screened for antimicrobial activity. The antimicrobial activity showed that the bromo as well as the nitro derivatives were the most active compounds.

Full text of DOI:10.1007/s00706-008-0941-1

Monatsh Chem 139, 1499–1505 (2008)
DOI 10.1007/s00706-008-0941-1
Printed in The Netherlands
C-Furyl glycosides, I: Synthesis and antimicrobial evaluation
of C-furyl glycosides and chalcones derived therefrom
Wael A. El-Sayed1, Mahmoud M. M. Ramiz2, Adel A.-H. Abdel-Rahman3
1
Department of Photochemistry, National Research Centre, Cairo, Egypt
2
Faculty of Electronic Engineering, Menoufia University, Menouf, Egypt
3
Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt
Received 14 March 2008; Accepted 10 April 2008; Published online 9 June 2008
# Springer-Verlag 2008
Abstract New C-furyl glycosides were synthesized
in order to increase the number of compounds
screened for antimicrobial activity. The antimicro-
bial activity showed that the bromo as well as the
nitro derivatives were the most active compounds.
antibiotic, antitumoral, and antiplatelet aggregation
activities [3]. In addition, they are used as a model
in enzymatic and metabolic studies; indeed it has
been shown that the conformational differences be-
tween the O- or N-glycosides and the C-linked ana-
logues are minimal [4]. Moreover, C-glycosides
are essentially more inert to degradation and there-
fore possess high resistance to enzymatic hydro-
lysis [5]. A large number of C-glycosides [6] of
considerable biological and chemical interest have
been found to possess a substituted tetrahydrofuran
moiety. C-Furyl glycosides are useful precursors
for the synthesis of many C-glycosyl antibiotics
[7]. In addition to their enzyme-inhibitory activi-
ties, these compounds are potential drug candidates
for new therapeutics [8]. They have also been used
as peptidomimetics that adopt interesting secondary
structures because of the rigidity generated by the
presence of furan moiety [9]. On the other hand,
furan ring systems are potential drugs for new ther-
apeutic strategies and exhibit a wide spectrum of
biological activities [10–14].
Keywords C-Furyl glycosides; N-Glycosides; Chalcones;
Antimicrobial activity.
Introduction
The high throughput screening techniques are rapid
methods to screen combinatorial assemblies for lead
molecules, which become the main place for many
drug discovery programs. Considerable attention has
been devoted to the synthesis of C-glycosyl com-
pounds owing to their biological interest, their natural
occurrence, and synthetic utility [1]. Among naturally
occurring C-glycosyl compounds, aryl C-glycosyl
derivatives are useful as enzyme inhibitors [2] and
present in a variety of biologically important natural
products as papulacandins, pluramycins, vineomycin,
gilvocarcin V, and urdamycin A, which are recog-
nized for their various biological activities including
Results and discussion
Chemistry
Correspondence: Adel A.-H. Abdel-Rahman, Faculty of
Science, Department of Chemistry, Menoufia University,
Shebin El-Koam, Egypt. E-mail: adelnassar63@hotmail.com
The starting material 3-acetyl-5-C-(l,4-anhydro-
ꢀ-D-erythro-tetrofuranosyl)-2-methylfuran (1) [15]

1500
W. A. El-Sayed et al.
was synthesized by treatment of D-glucose with
pentane-2,4-dione in the presence of 10 mol%
indium(III) chloride in water at 80ꢀC. A solution
of 1 in acetone=2,2-dimethoxypropane=p-toluene
sulfonic acid afforded after stirring 3-acetyl-5-
C-(2,3-O-isopropylidene-l,4-anhydro-ꢀ-D-erythro-
tetrofuranosyl)-2-methylfuran (2) in 80% yield.
The 1H NMR spectrum showed four singlets at
ꢁ ¼ 1.28, 1.49, 2.20, and 2.56 ppm for the isopropy-
lidene, 2-Me, and 3-Ac groups. The two doublets of
doublets at ꢁ ¼ 3.80 and 4.10 ppm correspond to H-
40a and H-40b, while the signals of H-20 and H-l0
appeared as two doublets at ꢁ ¼ 4.60 and 4.80 ppm.
The singlet at ꢁ ¼ 6.50 ppm corresponds to H-4.
Chalcones 3a–3f were synthesized by a base cata-
lyzed Claisen-Schmidt condensation reaction [16]
of 2 and substituted aldehydes. The method is attrac-
tive since it specifically generates the (E)-isomer.
1
From H NMR spectra, all chalcones were geomet-
rically pure and with trans-configuration (JHꢂ–Hꢀ
¼
15.5 Hz). Saturation of the double bond results in
loss of the anti-inflammatory and antimicrobial ac-
tivity [17, 18]. So, bromination of chalcones was
carried out by adding bromine drop wise to the clear
solution of 3a–3f in CHCl3 to afford the correspond-
ing 2,3-dibromochalcones 4a–4f. Monobromo deri-
vatives could be obtained from the corresponding
dibromochalcones according to the method described
by Holla et al. [19]. So, treatment of 4a–4f with dry
benzene in the presence of Et3N afforded 5a–5f.
Deprotection of 3–5 with 70% AcOH at reflux tem-
perature afforded the corresponding deprotected
1
derivatives 6–8. Their H NMR spectra showed the
disappearance of the isopropylidene group in all
cases (Scheme 1).
Antimicrobial activity
The newly synthesized compounds were tested
for their antimicrobial action [20] against four
different bacterial species namely, Pseudomonas
sp. (Gram negative bacterium), Bacillus subtilis
(Gram positive bacterium), Bacillus cereus (Gram
positive bacterium), and Streptomyces sp. (one of
the important actinomycetes). All the tested com-
pounds exhibited different degrees of antibacterial
activities or inhibitory actions. The most suscepti-
ble organisms were the two Gram positive bacteria
(Bacillus subtilis and Bacillus cereus) followed by
Streptomyces sp., while the lowest inhibitory effect
was encountered in the case of Pseudomonas sp.
The highest degrees of inhibition were recorded
for compounds 6c, 6d, 6f, 8c, 8d, and 8f follow-
ed by 1, 6a, 6b, 6e, 8a, 8b, and 8e, while the
lowest degree of inhibition was recorded for the
dibromochalcones 7a–7f (Table 1). The results
were compared to amoxicillin (penicillin) as a ref-
erence drug.
Scheme 1

C-Furyl glycosides, I
1501
Table 1 Antimicrobial activity of the newly synthesized com-
pounds 6–8
the combined ether extracts were dried over Na2SO4.
Evaporation under reduced pressure yielded 2.83 g (80%) as a
1
white foam. H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.28 (s, CH3),
Compd
no.
Pseudomonas Bacillus Bacillus Strepto-
sp.
1.49 (s, CH3), 2.20 (s, CH3), 2.56 (s, COCH3), 3.80 (dd, J ¼ 3.2,
10.4Hz, H-40a), 4.10 (dd, J ¼ 4.8, 10.4 Hz, H-40b), 4.30 (m, H-
30), 4.60 (d, J ¼ 6.4 Hz, H-20), 4.80 (d, J ¼ 6.4 Hz, H-l0), 6.50
(s, H-4) ppm; MS (ESI): m=z ¼ 289 [Mþ þ Na].
subtilis cereus
myces sp.
Amoxicillin
(Penicillin)
ꢁ
þþ
þ þþ
þ
1
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þþ
þþ
þþ
þ þþ
þþ
þ
þ
þ
þ
General procedure for the preparation of chalcones 3a–3f
To a solution of 2.66 g 2 (10 mmol) in 20 cm EtOH, an
aqueous solution of 10 cm3 10% NaOH was added. The
resulting solution was heated to 80ꢀC and substituted ben-
zaldehydes (10 mmol) were added with constant stirring.
The reaction mixture was kept stirring at this temperature
for 3–4 h, cooled to room temperature, and was allowed to
stand overnight. The solid product separated was collected
by filtration, dried, and recrystallized from ethanol to give
3a–3f in 78–82% yields.
6a
6b
6c
6d
6e
6f
7a
7b
7c
7d
7e
7f
8a
8b
8c
8d
8e
8f
þ þþþ
þ þþþ þ þþþ
þ þþþ þ þþþ þþ
þþ
þ þþ
þ
þ þþþ þ þþþ
þ
þ
þ
þ
þþ
þþ
þþ
þþ
þþ
þþ
þþ
þ
þ
þ
þþ
þþ
þ
þ
þ
(E)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-3-phenylprop-2-en-1-one
(3a, C21H22O5)
þ
þþ
þ
þþ
þ þþ
þþ
þ
White foam (80%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.25 (s,
CH3), 1.52 (s, CH3), 2.21 (s, CH3), 3.77 (dd, J ¼ 3.2, 10.4Hz,
H-40a), 4.08 (dd, J ¼ 4.8, 10.4Hz, H-40b), 4.25 (m, H-30), 4.55
(d, J ¼ 6.4Hz, H-20), 4.77 (d, J ¼ 6.4 Hz, H-l0), 6.45 (s, H-4),
7.60 (d, J ¼ 15.5Hz, COCH¼CH), 7.74–7.89 (m, Ar–H), 7.92
(d, J ¼ 15.5Hz, COCH¼CH) ppm; MS (ESI): m=z ¼ 377
[Mþ þ Na].
þ þþþ þ þþþ
þ þþþ þ þþþ
þ
þþ
þ þþ
þ
þ þþþ þ þþþ þþ
ꢁ No antimicrobial effect; þ Low antimicrobial effect
(4 mm); þþ Moderate antimicrobial effect (8–10 mm);
þ þþ High antimicrobial effect (15–18 mm); þ þþþ Com-
plete antimicrobial effect (20–22 mm)
(E)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-3-(2-bromophenyl)prop-2-en-1-
one (3b, C21H21BrO5)
Experimental
Yellow foam (81%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.26 (s,
CH3), 1.54 (s,CH3), 2.23 (s, CH3), 3.79 (dd, J ¼ 3.2, 10.4Hz,
H-40a), 4.12 (dd, J ¼ 4.8, 10.4Hz, H-40b), 4.26 (m, H-30), 4.59
(d, J ¼ 6.4Hz, H-20), 4.81 (d, J ¼ 6.4 Hz, H-l0), 6.49 (s, H-4),
7.62 (d, J ¼ 15.5Hz, COCH¼CH), 7.70–7.80 (m, Ar–H), 7.94
(d, J ¼ 15.5Hz, COCH¼CH) ppm; MS (ESI): m=z ¼ 455=457
[Mþ þ Na].
General
Melting points were determined using a Kofler block instru-
ment. TLC was performed on plastic plates Silica Gel 60 F254
(E. Merck, layer thickness 0.2mm). NMR spectra were re-
corded on a Bruker AC 250 FT NMR spectrometer at
1
250 MHz for H NMR with TMS as an internal standard. ES
mass spectra were obtained from an Esquire 3000plus iontrap
mass spectrometer from Bruker Daltonics. The microanalyses
were performed at the microanalytical unit, Cairo University,
Egypt, and were found to agree favorably with the calculated
values. Antimicrobial activity of the synthesized compounds
was conducted at the Botany Department, Faculty of Science,
Menoufia University, Shebin El-Koam, Egypt.
(E)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-3-(4-bromophenyl)prop-2-en-1-
one (3c, C21H21BrO5)
Yellow foam (82%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.28 (s,
CH3), 1.52 (s, CH3), 2.20 (s, CH3), 3.75 (dd, J ¼ 3.2, 10.4Hz,
H-40a), 4.10 (dd, J ¼ 4.8, 10.4Hz, H-40b), 4.29 (m, H-30), 4.66
(d, J ¼ 6.4Hz, H-20), 4.87 (d, J ¼ 6.4 Hz, H-l0), 6.53 (s, H-4),
7.70 (d, J ¼ 15.5Hz, COCH¼CH), 7.75–7.84 (m, Ar–H), 7.97
(d, J ¼ 15.5Hz, COCH¼CH) ppm; MS (ESI): m=z ¼ 455=457
[Mþ þ Na].
3-Acetyl-5-C-(2,3-O-isopropylidene-1,4-anhydro-ꢀ-D-
erythrofuranosyl)-2-methylfuran (2, C11H18O5)
A solution of 3.0 g 1 (13.3 mmol) in 40cm3 dry acetone, 4 cm3
2,2-dimethoxypropane, and 0.2 g p-toluene sulfonic acid was
stirred for 1 h at 0ꢀC. The reaction mixture was stirred at
25ꢀC for overnight. The resulting solution was neutralized
with pyridine and evaporated to a yellow oil. This oil was
partitioned between 20 cm3 H2O and 20cm3 of ether. The water
layer was extracted twice with 20cm3 portions of ether, and
(E)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-3-(2,4-dibromophenyl)prop-2-en-
1-one (3d, C21H20Br2O5)
Yellow foam (80%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.25 (s,
CH3), 1.50 (s, CH3), 2.25 (s, CH3), 3.83 (dd, J ¼ 3.2, 10.4Hz,

1502
W. A. El-Sayed et al.
H-40a), 4.17 (dd, J ¼ 4.8, 10.4Hz, H-40b), 4.33 (m, H-30), 4.62
(d, J ¼ 6.4Hz, H-20), 4.87 (d, J ¼ 6.4 Hz, H-l0), 6.55 (s, H-4),
7.72 (d, J ¼ 15.5 Hz, COCH¼CH), 7.79–7.88 (m, Ar–H), 7.99
(d, J ¼ 15.5Hz, COCH¼CH) ppm; MS (ESI): m=z ¼ 533=
535 [Mþ þ Na].
1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2,3-dibromo-3-(4-bromo-
phenyl)propan-1-one (4c, C21H21Br3O5)
Yellow foam (82%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.24 (s,
CH3), 1.59 (s, CH3), 2.25 (s, CH3), 3.68 (m, H-40a), 4.08 (m,
H-40b), 4.22 (m, H-30), 4.55 (d, J ¼ 6.4 Hz, H-20), 4.70 (d, J ¼
6.4 Hz, H-l0), 5.53 (d, J ¼ 2.5 Hz, CH), 5.67 (d, J ¼ 2.5 Hz,
CH), 6.45 (s, H-4), 7.38–7.59 (m, Ar–H) ppm; MS (ESI):
m=z ¼ 615=617 [Mþ þ Na].
(E)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-3-(2-fluorophenyl)prop-2-en-1-
one (3e, C21H21FO5)
1
White foam (78%); H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.23
(s, CH3), 1.50 (s, CH3), 2.19 (s, CH3), 3.78 (dd, J ¼ 3.2,
10.4 Hz, H-40a), 4.10 (dd, J ¼ 4.8, 10.4 Hz, H-40b), 4.27 (m,
H-30), 4.56 (d, J ¼ 6.4 Hz, H-20), 4.79 (d, J ¼ 6.4 Hz, H-l0),
6.52 (s, H-4), 7.60 (d, J ¼ 15.5 Hz, COCH¼CH), 7.76–7.87
(m, Ar–H), 7.95 (d, J ¼ 15.5 Hz, COCH¼CH) ppm; MS
(ESI): m=z ¼ 395 [Mþ þ Na].
1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2,3-dibromo-3-(2,4-dibromo-
phenyl)propan-1-one (4d, C21H20Br4O5)
Yellow foam (81%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.23 (s,
CH3), 1.54 (s, CH3), 2.22 (s, CH3), 3.65 (m, H-40a), 4.03 (m,
H-40b), 4.27 (m, H-30), 4.54 (d, J ¼ 6.4 Hz, H-20), 4.70 (d, J ¼
6.4 Hz, H-l0), 5.55 (d, J ¼ 2.5 Hz, CH), 5.68 (d, J ¼ 2.5 Hz,
CH), 6.43 (s, H-4), 7.55–7.70 (m, Ar–H) ppm; MS (ESI):
m=z ¼ 693=695 [Mþ þ Na].
(E)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-3-(3-nitrophenyl)prop-2-en-1-one
(3f, C21H21NO7)
Pale yellow foam (79%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.28
(s, CH3), 1.54 (s, CH3), 2.24 (s, CH3), 3.78 (dd, J ¼ 3.2, 10.4Hz,
H-40a), 4.09 (dd, J ¼ 4.8, 10.4Hz, H-40b), 4.33 (m, H-30), 4.63
(d, J ¼ 6.4Hz, H-20), 4.84 (d, J ¼ 6.4 Hz, H-l0), 6.51 (s, H-4),
7.72 (d, J ¼ 15.5 Hz, COCH¼CH), 7.80–8.35 (m, Ar–H,
COCH¼CH) ppm; MS (ESI): m=z ¼ 422 [Mþ þ Na].
1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2,3-dibromo-3-(2-fluoro-
phenyl)propan-1-one (4e, C21H21Br2FO5)
1
Yellow foam (80%); H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.22
(s, CH3), 1.52 (s, CH3), 2.20 (s, CH3), 3.60 (m, H-40a), 4.09
(m, H-40b), 4.23 (m, H-30), 4.52 (d, J ¼ 6.4 Hz, H-20), 4.66 (d,
J ¼ 6.4Hz, H-l0), 5.50 (d, J ¼ 2.5 Hz, CH), 5.67 (d, J ¼
2.5 Hz, CH), 6.49 (s, H-4), 6.92–7.10 (m, Ar–H), 7.52–7.65
(m, Ar–H) ppm; MS (ESI): m=z ¼ 553=555 [Mþ þ Na].
General procedure for the preparation of 2,3-
dibromochalcones 4a–4f
Bromine (1.6g, 10mmol) was added dropwise with vigorous
stirring to a solution of 3a–3f (10 mmol) in 10cm3 CHCl3
over 30min. After complete addition of Br2, the reaction mix-
ture was allowed to stand for 1 h. The dibromo derivatives
were precipitated, filtered off, and washed with 3ꢂ10cm3
ether to remove the excess of Br2. Recrystallization from
ethanol afforded 4a–4f in 80–82% yields.
1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2,3-dibromo-3-(3-nitro-
phenyl)propan-1-one (4f, C21H21Br2NO7)
1
Yellow foam (80%); H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.26
(s, CH3), 1.56 (s, CH3), 2.21 (s, CH3), 3.55 (m, H-40a), 4.00
(m, H-40b), 4.22 (m, H-30), 4.51 (d, J ¼ 6.4 Hz, H-20), 4.68 (d,
J ¼ 6.4Hz, H-l0), 5.61 (d, J ¼ 2.5 Hz, CH), 5.70 (d, J ¼ 2.5 Hz,
CH), 6.45 (s, H-4), 7.47–7.59 (m, Ar–H), 8.10 (s, Ar–H) ppm;
MS (ESI): m=z ¼ 580=582 [Mþ þ Na].
1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2,3-dibromo-3-phenylpropan-1-one
(4a, C21H22Br2O5)
1
Yellow foam (81%); H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.29
General procedure for the preparation of 2-bromochalcones
5a–5f
(s, CH3), 1.55 (s, CH3), 2.24 (s, CH3), 3.70 (dd, J ¼ 3.2,
10.4 Hz, H-40a), 4.04 (dd, J ¼ 4.8, 10.4 Hz, H-40b), 4.33 (m,
H-30), 4.63 (d, J ¼ 6.4 Hz, H-20), 4.78 (d, J ¼ 6.4 Hz, H-l0),
5.66 (d, J ¼ 2.5 Hz, CH), 5.79 (d, J ¼ 2.5 Hz, CH), 6.53 (s,
H-4), 7.72–7.84 (m, Ar–H) ppm; MS (ESI): m=z ¼ 535=537
[Mþ þ Na].
Triethylamine (4.04 g, 40mmol) in 30cm3 dry benzene was
added to a solution of 4a–4f (10 mmol) in 100cm3 dry ben-
zene with stirring. The reaction mixture was stirred at room
temperature for 24h. After removal of the separated triethy-
lamine hydrobromide, the filtrate was concentrated under re-
duced pressure. The residue was recrystallized from ethanol to
give 5a–5f in 80–84% yields.
1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2,3-dibromo-3-(2-bromo-
phenyl)propan-1-one (4b, C21H21Br3O5)
Yellow foam (80%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.26 (s,
CH3), 1.61 (s, CH3), 2.26 (s, CH3), 3.66 (m, H-40a), 4.09 (m,
H-40b), 4.29 (m, H-30), 4.60 (d, J ¼ 6.4 Hz, H-20), 4.74 (d, J ¼
6.4 Hz, H-l0), 5.58 (d, J ¼ 2.5 Hz, CH), 5.72 (d, J ¼ 2.5 Hz,
CH), 6.48 (s, H-4), 7.42–7.69 (m, Ar–H) ppm; MS (ESI):
m=z ¼ 615=617 [Mþ þ Na].
(Z)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2-bromo-3-phenylprop-2-en-1-
one (5a, C21H21BrO5)
Yellow foam (80%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.26 (s,
CH3), 1.59 (s, CH3), 2.24 (s, CH3), 3.60 (m, H-40a), 4.11 (m,
H-40b), 4.25 (m, H-30), 4.56 (d, J ¼ 6.4 Hz, H-20), 4.69 (d, J ¼

C-Furyl glycosides, I
1503
(E)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
6.4 Hz, H-l0), 6.46 (s, H-4), 7.39–7.59 (m, Ar–H), 8.45 (s, CH)
ppm; MS (ESI): m=z ¼ 455=457 [Mþ þ Na].
furan]-3-phenylprop-2-en-1-one (6a, C18H18O5)
White powder (82%); mp 111–113ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.25 (s, CH3), 3.65 (m, H-30), 3.78 (m, H-
40a), 4.03 (m, H-40b), 4.15 (m, H-20), 4.85 (br, s, 2ꢂOH),
5.30 (d, J ¼ 6.4 Hz, H-l0), 6.45 (s, H-4), 7.50 (d, J ¼ 15.5Hz,
COCH¼CH), 7.70–7.80 (m, Ar–H), 7.90 (d, J ¼ 15.5 Hz,
COCH¼CH) ppm; MS (ESI): m=z ¼ 337 [Mþ þ Na].
(Z)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2-bromo-3-(2-bromophenyl)-
prop-2-en-1-one (5b, C21H20Br2O5)
Yellow foam (82%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.23 (s,
CH3), 1.52 (s, CH3), 2.22 (s, CH3), 3.61 (m, H-40a), 4.10 (m,
H-40b), 4.22 (m, H-30), 4.54 (d, J ¼ 6.4 Hz, H-20), 4.65 (d, J ¼
6.4 Hz, H-l0), 6.49 (s, H-4), 7.38–7.49 (m, Ar–H), 8.40 (s, CH)
ppm; MS (ESI): m=z ¼ 533=535 [Mþ þ Na].
(E)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-3-(2-bromophenyl)prop-2-en-1-one
(6b, C18H17BrO5)
Pale yellow powder (81%); mp 117–119ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.19 (s, CH3), 3.69 (m, H-30), 3.79 (m, H-40a),
4.07 (m, H-40b), 4.17 (m, H-20), 4.81 (br, s, 2ꢂOH), 5.36
(d, J ¼ 6.4 Hz, H-l0), 6.49 (s, H-4), 7.51 (d, J ¼ 15.5Hz,
COCH¼CH), 7.66–7.73 (m, Ar–H), 7.88 (d, J ¼ 15.5 Hz,
COCH¼CH) ppm; MS (ESI): m=z ¼ 415=417 [Mþ þ Na].
(Z)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2-bromo-3-(4-bromophenyl)-
prop-2-en-1-one (5c, C21H20Br2O5)
Yellow foam (84%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.26 (s,
CH3), 1.56 (s, CH3), 2.23 (s, CH3), 3.54 (m, H-40a), 4.10 (m,
H-40b), 4.22 (m, H-30), 4.59 (d, J ¼ 6.4Hz, H-20), 4.53 (d,
J ¼ 6.4 Hz, H-l0), 6.49 (s, H-4), 7.59–7.77 (m, Ar–H), 8.35
(s, CH) ppm; MS (ESI): m=z ¼ 533=535 [Mþ þ Na].
(E)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-3-(4-bromophenyl)prop-2-en-1-one
(Z)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2-bromo-3-(2,4-dibromo-
phenyl)prop-2-en-1-one (5d, C21H19Br3O5)
(6c, C18H17BrO5)
Pale yellow powder (82%); mp 133–135ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.17 (s, CH3), 3.60 (m, H-30), 3.69 (m, H-40a),
4.04 (m, H-40b), 4.18 (m, H-20), 4.77 (br, s, 2ꢂOH), 5.34
(d, J ¼ 6.4 Hz, H-l0), 6.47 (s, H-4), 7.50 (d, J ¼ 15.5Hz,
COCH¼CH), 7.76–7.80 (m, Ar–H), 7.93 (d, J ¼ 15.5Hz,
COCH¼CH) ppm; MS (ESI): m=z ¼ 415=417 [Mþ þ Na].
1
Yellow foam (83%); H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.25
(s, CH3), 1.52 (s, CH3), 2.26 (s, CH3), 3.56 (m, H-40a), 4.11
(m, H-40b), 4.29 (m, H-30), 4.63 (d, J ¼ 6.4 Hz, H-20), 4.58
(d, J ¼ 6.4Hz, H-l0), 6.51 (s, H-4), 7.49–7.57 (m, Ar–H),
7.62 (s, Ar–H), 8.47 (s, CH) ppm; MS (ESI): m=z ¼ 613=615
[Mþ þ Na].
(E)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-3-(2,4-dibromophenyl)prop-2-en-1-one
(Z)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2-bromo-3-(2-fluorophenyl)-prop-
2-en-1-one (5e, C21H20BrFO5)
Yellow foam (81%); 1H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.22 (s,
CH3), 1.48 (s, CH3), 2.20 (s, CH3), 3.50 (m, H-40a), 4.10 (m,
H-40b), 4.20 (m, H-30), 4.57 (d, J ¼ 6.4Hz, H-20), 4.48 (d,
J ¼ 6.4 Hz, H-l0), 6.47 (s, H-4), 7.29–7.36 (m, Ar–H), 8.33
(s, CH) ppm; MS (ESI): m=z ¼ 473=475 [Mþ þ Na].
(6d, C18H16Br2O5)
Yellow powder (80%); mp 149–151ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.15 (s, CH3), 3.57 (m, H-30), 3.70 (m, H-40a),
4.02 (m, H-40b), 4.16 (m, H-20), 4.79 (br, s, 2ꢂOH), 5.30 (d,
J ¼ 6.4 Hz, H-l0), 6.48 (s, H-4), 7.36–7.44 (m, Ar–H), 7.48 (d,
J ¼ 15.5Hz, COCH¼CH), 7.58 (s, Ar–H), 7.88 (d, J ¼ 15.5Hz,
COCH¼CH) ppm; MS (ESI): m=z ¼ 493=495 [Mþ þ Na].
(E)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-3-(2-fluorophenyl)prop-2-en-1-one
(Z)-1-[5-C-(2,3-O-Isopropylidene-1,4-anhydro-ꢀ-D-erythro-
furanosyl)-2-methylfuran]-2-bromo-3-(3-nitrophenyl)-prop-
2-en-1-one (5f, C21H20BrNO7)
(6e, C18H17FO5)
White powder (77%); mp 121–123ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.17 (s, CH3), 3.59 (m, H-30), 3.76 (m, H-
40a), 4.07 (m, H-40b), 4.18 (m, H-20), 4.87 (br, s, 2ꢂOH),
5.38 (d, J ¼ 6.4 Hz, H-l0), 6.52 (s, H-4), 7.22–7.33 (m, Ar–
H), 7.45 (d, J ¼ 15.5Hz, COCH¼CH), 7.82 (d, J ¼ 15.5Hz,
COCH¼CH) ppm; MS (ESI): m=z ¼ 355 [Mþ þ Na].
1
Yellow foam (82%); H NMR (CDCl3, 250 MHz): ꢁ ¼ 1.26
(s, CH3), 1.54 (s, CH3), 2.24 (s, CH3), 3.57 (m, H-40a), 4.14
(m, H-40b), 4.27 (m, H-30), 4.61 (d, J ¼ 6.4 Hz, H-20), 4.57
(d, J ¼ 6.4Hz, H-l0), 6.52 (s, H-4), 7.79–7.89 (m, Ar–H),
8.31 (s, Ar–H), 8.45 (s, CH) ppm; MS (ESI): m=z ¼ 500=502
[Mþ þ Na].
(E)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-3-(3-nitrophenyl)prop-2-en-1-one
General procedure for the preparation of 6–8
Compounds 3–5 (0.25 g) were refluxed in 10 cm3 70% aque-
ous AcOH for 2 h. The solvents were removed under reduced
pressure. Water (4ꢂ5 cm3) and then EtOH (3ꢂ5 cm3) were
coevaporated from the remaining residue. The residue was
purified by column chromatography using 5% MeOH in
CHCl3 to give 6a–6f (75–82%), 7a–7f (68–75%), and 8a–
8f (72–78%) yields.
(6f, C18H17NO5)
Pale yellow powder (75%); mp 170–172ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.17 (s, CH3), 3.68 (m, H-30), 3.79 (m, H-40a),
4.09 (m, H-40b), 4.13 (m, H-20), 4.80 (br, s, 2ꢂOH), 5.34
(d, J ¼ 6.4 Hz, H-l0), 6.47 (s, H-4), 7.47 (d, J ¼ 15.5Hz,
COCH¼CH), 7.62–7.78 (m, Ar–H), 7.82–7.95 (m, COCH¼
CH, Ar–H) ppm; MS (ESI): m=z ¼ 382 [Mþ þ Na].

1504
W. A. El-Sayed et al.
5.71 (d, J ¼ 2.5 Hz, CH), 6.51 (s, H-4), 7.72–7.85 (m,
Ar–H), 8.06 (s, Ar–H) ppm; MS (ESI): m=z ¼ 540=542
[Mþ þ Na].
1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2,3-dibromo-3-phenylpropan-1-one (7a, C18H18Br2O5)
Yellow powder (75%); mp 166–168ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.13 (s, CH3), 3.55 (m, H-30), 3.70 (m, H-
40a), 4.03 (m, H-40b), 4.14 (m, H-20), 4.80 (br, s, 2ꢂOH),
5.35 (d, J ¼ 6.4 Hz, H-l0), 5.60 (d, J ¼ 2.5Hz, CH), 5.70 (d,
J ¼ 2.5 Hz, CH), 6.50 (s, H-4), 7.22–7.37 (m, Ar–H) ppm; MS
(ESI): m=z ¼ 495=497 [Mþ þ Na].
(Z)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2-bromo-3-phenylprop-2-en-1-one (8a, C18H17BrO5)
Yellow powder (78%); mp 201–203ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.19 (s, CH3), 3.69 (m, H-30), 3.79 (m, H-
40a), 4.00 (m, H-40b), 4.16 (m, H-20), 4.82 (br, s, 2ꢂOH),
5.49 (d, J ¼ 6.4 Hz, H-l0), 6.46 (s, H-4), 7.39–7.50 (m, Ar–
H), 8.40 (s, CH) ppm; MS (ESI): m=z ¼ 415=417 [Mþ þ Na].
1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2,3-dibromo-3-(2-bromophenyl)propan-1-one
(7b, C18H17Br3O5)
Yellow powder (75%); mp 173–175ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.16 (s, CH3), 3.60 (m, H-30), 3.74 (m, H-
40a), 4.03 (m, H-40b), 4.19 (m, H-20), 4.79 (br, s, 2ꢂOH),
5.40 (d, J ¼ 6.4 Hz, H-l0), 5.65 (d, J ¼ 2.5Hz, CH), 5.72 (d,
J ¼ 2.5 Hz, CH), 6.54 (s, H-4), 7.12–7.35 (m, Ar–H) ppm; MS
(ESI): m=z ¼ 575=577 [Mþ þ Na].
(Z)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2-bromo-3-(2-bromophenyl)prop-2-en-1-one
(8b, C18H16Br2O5)
Yellow powder (76%); mp 188–190ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.15 (s, CH3), 3.65 (m, H-30), 3.75 (m, H-
40a), 4.06 (m, H-40b), 4.14 (m, H-20), 4.80 (br, s, 2ꢂOH),
5.51 (d, J ¼ 6.4 Hz, H-l0), 6.44 (s, H-4), 7.19–7.39 (m, Ar–
H), 8.37 (s, CH) ppm; MS (ESI): m=z ¼ 493=495 [Mþ þ Na].
1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2,3-dibromo-3-(4-bromophenyl)propan-1-one
(7c, C18H17Br3O5)
(Z)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-2-bromo-3-(4-bromophenyl)prop-2-en-1-one
(8c, C18H16Br2O5)
Yellow powder (77%); mp 199–201ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.18 (s, CH3), 3.60 (m, H-30), 3.70 (m, H-
40a), 4.03 (m, H-40b), 4.12 (m, H-20), 4.81 (br, s, 2ꢂOH),
5.50 (d, J ¼ 6.4 Hz, H-l0), 6.40 (s, H-4), 7.42–7.69 (m, Ar–
H), 8.17 (s, CH) ppm; MS (ESI): m=z ¼ 493=495 [Mþ þ Na].
Yellow powder (73%); mp 190–192ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.18 (s, CH3), 3.60 (m, H-30), 3.70 (m, H-
40a), 4.06 (m, H-40b), 4.23 (m, H-20), 4.88 (br, s, 2ꢂOH),
5.47 (d, J ¼ 6.4 Hz, H-l0), 5.64 (d, J ¼ 2.5Hz, CH), 5.79 (d,
J ¼ 2.5 Hz, CH), 6.59 (s, H-4), 7.19–7.38 (m, Ar–H) ppm; MS
(ESI): m=z ¼ 575=577 [Mþ þ Na].
1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2,3-dibromo-3-(2,4-dibromophenyl)propan-1-one
(7d, C18H16Br4O5)
Yellow powder (71%); mp 201–203ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.15 (s, CH3), 3.57 (m, H-30), 3.78 (m, H-
40a), 4.09 (m, H-40b), 4.22 (m, H-20), 4.85 (br, s, 2ꢂOH),
5.45 (d, J ¼ 6.4 Hz, H-l0), 5.66 (d, J ¼ 2.5Hz, CH), 5.76 (d,
J ¼ 2.5 Hz, CH), 6.50 (s, H-4), 7.19–7.30 (m, Ar–H), 7.60 (s,
Ar–H) ppm; MS (ESI): m=z ¼ 653=655 [Mþ þ Na].
(Z)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-2-bromo-3-(2,4-dibromophenyl)prop-2-en-1-one
(8d, C18H15Br3O5)
Yellow powder (74%); mp 215–217ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.19 (s, CH3), 3.67 (m, H-30), 3.79 (m, H-
40a), 4.08 (m, H-40b), 4.17 (m, H-20), 4.83 (br, s, 2ꢂOH),
5.54 (d, J ¼ 6.4 Hz, H-l0), 6.43 (s, H-4), 7.39–7.44 (m, Ar–
H), 7.60 (s, Ar–H), 8.35 (s, CH) ppm; MS (ESI): m=z ¼
573=575 [Mþ þ Na].
1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2,3-dibromo-3-(2-fluorophenyl)propan-1-one
(Z)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-2-bromo-3-(2-fluorophenyl)prop-2-en-1-one
(8e, C18H16BrFO5)
Yellow powder (72%); mp 210–212ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.13 (s, CH3), 3.62 (m, H-30), 3.69 (m, H-
40a), 4.01 (m, H-40b), 4.12 (m, H-20), 4.77 (br, s, 2ꢂOH),
5.50 (d, J ¼ 6.4 Hz, H-l0), 6.40 (s, H-4), 7.10–7.29 (m, Ar–
H), 8.39 (s, CH) ppm; MS (ESI): m=z ¼ 433=435 [Mþ þ Na].
(7e, C18H17Br2FO5)
Yellow powder (69%); mp 216–218ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.17 (s, CH3), 3.60 (m, H-30), 3.70 (m, H-
40a), 4.03 (m, H-40b), 4.17 (m, H-20), 4.78 (br, s, 2ꢂOH),
5.41 (d, J ¼ 6.4 Hz, H-l0), 5.64 (d, J ¼ 2.5Hz, CH), 5.70 (d,
J ¼ 2.5 Hz, CH), 6.50 (s, H-4), 7.10–7.29 (m, Ar–H) ppm; MS
(ESI): m=z ¼ 513=515 [Mþ þ Na].
1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methylfuran]-
2,3-dibromo-3-(3-nitrophenyl)propan-l-one
(7f, C18H17Br2NO7)
(Z)-1-[5-C-(1,4-Anhydro-ꢀ-D-erythrofuranosyl)-2-methyl-
furan]-2-bromo-3-(3-nitrophenyl)prop-2-en-1-one
(8f, C18H16BrNO7)
Yellow powder (72%); mp 233–235ꢀC; 1H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.19 (s, CH3), 3.69 (m, H-30), 3.79 (m, H-
40a), 4.07 (m, H-40b), 4.19 (m, H-20), 4.84 (br, s, 2ꢂOH),
5.57 (d, J ¼ 6.4 Hz, H-l0), 6.48 (s, H-4), 7.69–7.89 (m, Ar–
1
Yellow powder (68%); mp 207–209ꢀC; H NMR (CDCl3,
250 MHz): ꢁ ¼ 2.19 (s, CH3), 3.63 (m, H-30), 3.76 (m,
H-40a), 4.05 (m, H-40b), 4.17 (m, H-20), 4.75 (br, s, 2ꢂ
OH), 5.42 (d, J ¼ 6.4 Hz, H-l0), 5.62 (d, J ¼ 2.5 Hz, CH),

C-Furyl glycosides, I
1505
H), 8.31 (s, Ar–H), 8.43 (s, CH) ppm; MS (ESI): m=z ¼
460=462 [Mþ þ Na].
(1984) Carbohydr Res 131:273; e) Lipshutz BH (1986)
Chem Rev 86:795
7. Chakraborty TK, Ghosh S, Jayaprakash S, Sharma JARP,
Ravikanth V, Diwan PV, Nagaraj R, Kunwar AC (2000) J
Org Chem 65:6441
Antimicrobial testing
8. a) Long DD, Smith MD, Martin A, Wheatley JR, Watkin
DG, Muller M, Fleet GWJ (2002) J Chem Soc Perkin
Trans 1:1982; b) Hungerford NL, Claridge TDW,
Watterson MP, Aplin RT, Moreno A, Fleet GWJ (2000)
J Chem Soc Perkin Trans 1:3666
9. a) Misra AK, Agnihotri G (2004) Carbohydr Res
339:1381; b) Hungerford NL, Fleet GWJ (2000) J Chem
Soc Perkin Trans 1:3680; c) Smith MD, Fleet GWJ
(1999) J Peptide Sci 5:425
The hole plate method was used to investigate the antibacterial
activities of the different compounds. Nutritive agar plates
seeded with the test organisms (three plates for each organism)
were allowed to solidify, and then 5 mm diameter holes were
formed in the plates using a cork borer. Each hole was filled
with one drop of the ethanolic solution of the tested com-
pound, while the hole in the center of the plate was filled with
one drop of ethanol. Plates were separately incubated at 30ꢀC
for 24 h. Inhibition zones (zones with no growth) around the
holes were measured.
10. Poeta DM, Schell WA, Christine C, Jones SK, Tidwell R,
Kumar A, Baykin DW, Perfect JR (1998) Antimicrob
Agents Chemother 42:2503
11. Lercetto H, Maio DR, Gonzalez M, Rissao M, Gabriel S,
Seoane G, Denicola A, Feluffo G, Quijano C, Stoppani
AOM (2000) Eur J Med Chem 35:343
12. a) Setsuyo S, Obase H, Ichikawa S, Kitazawa T, Nonaka
H, Yoshizaki R, Ishii A, Shuto K (1993) J Med Chem
36:572; b) Daniel JA, Dave J, Douglas K, Gerry S, Larsen
J, Ganiel D, Hongding E, Cohen J, Lee J, Warner R
(1999) Bioorg Med Chem Lett 9:1069
References
1. a) Du Y, Linhardt RJ (1998) Tetrahedron 54:9913;
b) Beau JM, Gallagher T (1997) Top Curr Chem
187:1; c) Xie J (1999) Recent Res Dev Org Chem
3:505; d) Hacksell U, Daves GD Jr (1985) Progress
Med Chem 22:1; e) Nicotra F (1997) Top Curr Chem
187:55
13. Han Y, Giroux A, Lepine C, Laliberte F, Haung Z,
Perrier H, Bayly CI, Young RN (1999) Tetrahedron
55:11669
14. a) Moreno-Vargas AJ, Jimenez-Barbiro J, Robina I
(2003) J Org Chem 68:4128; b) Moreno-Vargas AJ,
Demange R, Fuentes J, Robina I, Vogel P (2002)
Biorg Med Chem Lett 12:2335; c) Moreno-Vargas AJ,
Fernandez-Bolanos JG, Fuentes J, Robina I (2001) Tetra-
heron Lett 42:1283
15. Yadav JS, Reddy BVS, Sreenivas M, Satheesh G (2007)
Synthesis 11:1712
16. a) Schmidt JG (1880) Ber Dtsch Chem Ges 13:2342; b)
Claisen L, Claparede A (1981) Ber Dtsch Chem Ges
14:349; c) Kohler EP, Chadwell HM (1922) Org Synth
2:1
17. Nargund LVG, Hariprasad V, Reddy GRN (1992) J Pharm
Sci 81:892
18. Abdel-Rahman AAH, Abdel-Megied AES, Hawata
MAM, Kasem ER, Shabaan MT (2007) Monatsh Chem
138:889
19. a) Holla BS, Akberali PM, Shivananda MK (2001) I
Farmaco 56:919; b) Bhat BA, Dhar KL, Puri SC, Saxena
AK, Shanmugavel M, Qazib GN (2005) Bioorg Med
Chem Lett 15:3177
20. a) Janssen AM, Scheffer JJ, Svendsen AB (1986) Planta
Medica:395; b) Shaaban MT, El-Sharif ME (2001) Afr J
Mycol Biotechnol 9(2):15
2. a) Hanessian S (1983) Total synthesis of natural products:
the Chiron approach. Pregamon, Oxford; b) BeMiller JN,
Yadav MP, Kalabokis VN, Myers RW (1990) Carbohydr
Res 200:111; c) Schmidt RR, Dietrich H (1991) Angew
Chem Int Ed 30:1328
3. a) Jay M, Viricel MR, Gonnet JF (2006) In: Andersen
OM, Markham KR (eds) Flavonoids: Chemistry, Bio-
chemistry and Applications. CRC Press, Boca Raton,
p 857; b) Hansen MR, Hurley LH (1996) Acc Chem
Res 29:249; c) Qian-Cutrone J, Kolb JM, McBrien K,
Huang S, Gustavson D, Lowe SE, Manly SP (1998) J Nat
Prod 61:1379; d) Ford PW, Gadepalli M, Davidson BS
(1998) J Nat Prod 61:1232; e) Bililign T, Griffth BR,
Thorson JS (2005) Nat Prod Pep 22:742
4. a) Wu TC, Goekjian PG, Kishi Y (1987) J Org Chem
52:4819; b) Wei A, Haudrechy A, Audin C, Jun HS,
Haudrechy-Bretel N, Kishi Y (1995) J Org Chem
60:2160
5. a) Jaramillo C, Knapp S (1993) Synthesis:1; b) Levy DE,
Tang C (1995) In: The Chemistry of C-Glycosides, Else-
vier Science, Tarrytown, NY; c) Postema MHD (1995) In:
Rees CW (ed) C-Glycoside Synthesis. CRC Press, Boca
Raton, FL
6. a) Postema MHD (1992) Tetrahedron 48:8545; b)
Schmidt RR, Effenberger G (1998) Liebigs Ann Chem
825; c) Maeba I, Iwata K, Usami F, Furukawa H (1983) J
Org Chem 48:2998; d) Grynkiewcz G, BeMiller JN