Stereoselective glycosylation of d-galactals by diethyl phosphorochloridite- and AlCl3-assisted Ferrier rearrangement

Article abstract of DOI:10.1016/j.tet.2014.11.027

α-2,3-Unsaturated galactosides were synthesized in good to excellent yields by the initial activation of d-galactals with diethyl phosphorochloridite and the subsequent glycosyl addition via Ferrier rearrangement with various O-nucleophiles in the presenc

Full text of DOI:10.1016/j.tet.2014.11.027

Tetrahedron 71 (2015) 350e358
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Stereoselective glycosylation of
D-galactals by diethyl
phosphorochloridite- and AlCl3-assisted Ferrier rearrangement
,
,d
Yen-Bo Chen a b, Su-I. Wang b, Zi-Ping Lin b, Chun-Hung Lin c, Min-Tsang Hsieh a
,
Hui-Chang Lin a
,b,
*
a School of Pharmacy, China Medical University, No. 91, Hsueh-Shih Rd., Taichung 40402, Taiwan
b Graduate Institute of Pharmaceutical Chemistry, China Medical University, No. 91, Hsueh-Shih Rd., Taichung 40402, Taiwan
c Institute of Biological Chemistry, Academia Sinica, No. 128, Academia Road, Section 2, Nan-Kang, Taipei 11529, Taiwan
d Chinese Medicinal Research and Development Center, China Medical University Hospital, No. 2, Yude Rd., Taichung 40447, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
a-2,3-Unsaturated galactosides were synthesized in good to excellent yields by the initial activation of
Received 12 September 2014
Received in revised form 30 October 2014
Accepted 9 November 2014
Available online 24 November 2014
D
-galactals with diethyl phosphorochloridite and the subsequent glycosyl addition via Ferrier re-
arrangement with various O-nucleophiles in the presence of AlCl3. The two-step reactions were carried
out in one-pot and finished within 60 min in 81e95% yield to give the glycoside products with excellent
a
-stereoselectivity.
Ó 2014 Elsevier Ltd. All rights reserved.
Keywords:
2,3-Unsaturated glycopyranosides
Ferrier rearrangement
Diethyl phosphorochloridite
Glycal
Lewis acid
1. Introduction
DDQ,34 Bi(NO3)3$5H2O,35 NbCl5,36 DMF-DMA,37 Pd(PhCN)2Cl2,38
Fe(OTf)3,39 Er(OTf)3,40 ZnCl2/Al2O3,41 (S)-Camphorsulfonic acid,42
H3PO4,43 TfOH-SiO2,44 NaHSO4eSiO2,45 and t-BuOK.46
Successful Ferrier rearrangement can be carried out when endo-
glycals possessing a good leaving group at C-3 position, including
trichloroacetamidate,47 tert-butyloxycarbonyl ester,48 n-pentenoyl
ester,23 benzoyl ester,12a carbonate,49 propargyl ether,50 and benzyl
ether.51 To the best of our knowledge, there is no report to derive
2,3-Unsaturated-O-glycosides are useful building blocks for the
synthesis of various bioactive compounds, such as nucleosides,1
antibiotics,2 glycopeptides,3 oligosaccharides,4 uronic acids,5 and
other natural products.6 The double bond in C2 and C3 of the py-
ranose ring can be further transformed via several types of reactions
(e.g., dihydroxylation,8 hydrogenation,9 epoxidation,10 and amino-
hydroxylation11) to generate structural complexity and diversity.
Preparation of 2,3-unsaturated glycosides via Ferrier rearrangement
has drawn attention in the past several decades. This rearrangement
is believed to involve a cyclic allylic oxocarbonium intermediate that
is formed via displacement of the C-3 substituent in an endo-glycal,
followed by the attack of a nucleophile to the anomeric carbon
preferentially from the quasi-equatorial orientation.7 A wide range
of catalysts have been employed to facilitate the syntheses, such as
from 3-O-diethoxyphosphanyl-D-galactal. However, the diethox-
yphosphanyl group can be easily activated in the presence of acid or
Lewis acid.53 Herein we developed an efficient two-step, one-pot
synthesis to prepare 2,3-unsaturated-O-glycosides. 3-Hydroxy-D-
galactal was reacted with diethyl phosphorochloridite and trie-
thylamine to give in situ the intermediate 3-O-diethox-
yphosphanyl-D-galactal, followed by rearrangement and glycosyl
addition with various O-nucleophiles in the presence of AlCl3 to
give 2,3-unsaturated-O-glycosides.
BF3$OEt2,12 FeCl3,13 InCl3,14 Montmorillonite K-10,15 SnCl4,16
17
K5CoeW12O40
,
BiCl3,18 Dy(OTf)3,19 CeCl3$7H2O,20 ZnCl2,21
Sc(OTf)3,22 IDCP,23 TMSOTf,24 NIS,25 LiBF4,26 trichloroacetimidate,27
2. Result and discussion
Fe(NO3)3$9H2O,28 InBr3,29 ZrCl4,30 I2,31 CAN,32 HClO4eSiO2,33
4,6-Di-O-benzyl-3-hydroxy-
tri-O-acetyl-
-galactal according to previous procedure,52 was
reacted with diethyl phosphorochloridite in the presence of Lewis
bases (3.0 equiv) to produce the 3-O-diethoxyphosphanyl-
D
-galactal 1a, prepared from 3,4,6-
D
* Corresponding author. Tel.: þ886 4 22053366x5612; fax: þ886 4 22078083;
e-mail addresses: lhc550005@yahoo.com.tw, huichang@mail.cmu.edu.tw (H.-C. Lin).
D-
http://dx.doi.org/10.1016/j.tet.2014.11.027
0040-4020/Ó 2014 Elsevier Ltd. All rights reserved.

Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
351
galactal as the intermediate, and was then followed by C1-addition
of n-hexanol to give the glycosyl adduct. Five different Lewis bases
(3.0 equiv) were examined, including triethylamine (Et3N), 4-
dimethylaminopyridine (DMAP), 1,8-diazabicyclo-[5.4.0]undec-7-
ene (DBU), potassium carbonate (K2CO3), and potassium tert-but-
oxide (t-BuOK), as shown in entries iev of Table 1. The reactions
were all carried out in dichloromethane at 0 ꢀC for 1 h. Among these
reactions, Et3N was found to provide the desired 2,3-unsaturated-
O-glycoside (4) with the highest isolated yield (91%) and moderate
Lewis acid. A CH2Cl2 solution of 4,6-di-O-benzyl-3-diethyl phos-
phite-
D
-galactal 3a and n-hexanol was treated with 1.0 equiv of
various Lewis acids at 0 ꢀC for 30 min, including zinc chloride
(ZnCl2), calcium chloride (CaCl2), mercury(II) sulfate (HgSO4), iron
chloride (FeCl3), aluminum chloride (AlCl3), and tin(IV) chloride
(SnCl4). The use of AlCl3 was concluded to provide the highest
isolated yield (94%) and stereoselectivity (ratio of
8) (entry v in Table 2).
a/b-anomers: 92/
To our delight, high yields and stereoselectivity were also ob-
tained when the same condition was applied to the reactions with
stereoselectivity (ratio of a/b-anomers: 78/22).
Table 1
Application of different Lewis bases and solvents for synthesis of 2,3-unsaturated glycosides 4a
Entry
Lewis base
Solvent
Products (yield,
a
/b
ratio)
i
ii
Et3N
DMAP
DBU
K2CO3
t-BuOK
Et3N
Et3N
Et3N
Et3N
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
MeCN
DMF
Toluene
4 (91%, 78/22)
4 (13%)b
4 (5%)b
iii
iv
v
vi
vii
viii
ix
4 (36%)b
4 (11%)b
4 (0%)
4 (0%)
4 (0%)
4 (85%, 75/25)
a
All reactions were carried out in the presence of diethyl chlorophosphite (1.2 equiv), Lewis base (3.0 equiv) and n-hexanol (3.0 equiv).
b
The a-anomer is predominant with a/b
ratio of 2/1e3/1 on the basis of 1H NMR integration.
Table 2
Effect of Lewis acid on the glycosylations of endo-glycal 1a with n-hexanola
Entry
Lewis acid (cat)
Products (yield,
a
/b
ratio)b
i
ii
ZnCl2
CaCl2
HgSO4
FeCl3
AlCl3
AlCl3
SnCl4
4 (89%, 73/27)
4 (84%, 81/19)
4 (88%, 80/20)
4 (78%, 90/10)
4 (94%, 92/8)
No reactionc
iii
iv
v
vi
vii
4 (91%, 84/16)
a
All reactions were carried out in the presence of Lewis acid (1.0 equiv) and n-hexanol (3.0 equiv).
b
c
The
a-anomer is predominant with a/b
ratio on the basis of 1H NMR integration.
The reaction was carried out without diethyl phosphorochloridite/Et3N in a CH2Cl2 solution containing AlCl3 (1.0 equiv) and n-hexanol (3.0 equiv) at 0 ꢀC for 1 h.
Meanwhile, we investigated the solvent effect by examining the
other alcohol nucleophiles (entries ievi in Table 3), as well as those
with a similar substrate (1b) (entries vii-ix).
Furthermore, various sugar nucleophiles were examined. Their
reactions gave the desirable 2,3-unsaturated glycoside products
reactions in THF, MeCN, DMF, CH2Cl2 and toluene (entries vi-ix of
Table 1). The reactions in toluene and dicholomethane were found
to afford higher yields and stereoselectivity than those in other
solvents. Among the reactions, the combined use of CH2Cl2 and
Et3N gave the desired product (4) in the highest isolated yield (91%)
17e22 in 81e86% yields with excellent a-stereoselectivity (Table 4).
It is realized that the nucleophile preferentially attacks from the
bottom face of the sugar ring, which is not only consistent with the
anomeric effect, but also favorable by the less steric hindrance
resulting from the C4-substituent. All the product structures, in-
cluding the new stereogenic configurations, were rigorously de-
termined by using the COSY and NOSY methods, in agreement with
previous reports.54 For example, the 1H NMR spectrum of com-
with moderate stereoselectivity (ratio of
a/
b-anomers: 78/22) (see
entry i in Table 1). Interestingly, 3-O-diethoxyphosphanyl-
D
-gal-
actal (3a) appeared to be more active than glycosyl diethyl phos-
phites (the phosphite is attached to the anomeric center)53 because
of different stability (3a could not be isolated but the latter could be
purified and characterized).
In order to improve the resulting
Lewis acid was considered in the Ferrier rearrangement-mediated
glycosylation. We generated 4,6-di-O-benzyl-3-diethyl phosphite-
-galactal (3a) in situ, followed by the addition of n-hexanol and
a
-stereoselectivity, addition of
pound 17 showed the characteristic signals of H1 (
5.90, dd), and H3 (
6.02, dd). In the corresponding 13C NMR
spectrum, the resonances at 96.30, 129.43, and 126.97 were
assigned to C1, C2 and C3 of 17, respectively.
d 5.43, d), H2 (d
d
d
D

352
Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
Table 3
The glycosylations of endo-glycal 1 with varies alcoholsa
b
Entry
Donor
Acceptor (R2OH)
Products (yield, a/b)
i
ii
1a
1a
1a
1a
1a
1a
1b
1b
1b
Methanol
5 (94%, 93/7)
6 (91%, 92/8)
7 (90%, 93/7)
8 (85%, 92/8)
9 (87%, 93/7)
33 (85%, 91/9)
10 (95%, 93/7)
11 (92%, 95/5)
12 (92%, 93/7)
Benzyl alcohol
Allyl alcohol
Isopropanol
Cyclohexanol
p-Methylphenol
Benzyl alcohol
Isopropanol
iii
iv
v
vi
vii
viii
ix
Cyclohexanol
a
All reactions were carried out in the presence of AlCl3 (1.0 equiv) and alcohols (3.0 equiv).
b
The a-anomer is predominant with a/b
ratio on the basis of 1H NMR integration.
Table 4
The glycosylations of endo-Glycals 1 with various sugar alcoholsa
b
Entry
i
Donor
Acceptor (ROH)a
Products (yield, a/b)
1a
17 (82%, 94/6)
ii
1a
1a
18 (83%, 95/5)
19 (86%, 93/7)
iii
iv
1a
20 (81%, 94/6)
v
1c
1c
21 (85%, 95/5)
22 (83%, 94/6)
vi
a
The glycosyl additions were all catalyzed by AlCl3 (1.0 equiv) with 3 equiv of the acceptor was dissolved in 0.5 mL CH2Cl2.
b
The a-anomer is predominant with a/b
ratio on the basis of 1H NMR integration.

Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
353
We previously applied microwave- and AlCl3-assisted glycosyl-
ation of C3-substituted endo-galactals (that contains a benzyloxy,
acetate or hydroxy group at C3) where these reactions were found
We proposed a plausible mechanism to interpret the observed
rearrangement and stereoselectivity. As shown in Scheme 1, the
first step reaction was expected to result in the formation of 3-O-
to proceed via protonation to produce
a
-2-deoxyglycosides.48b
diethoxyphosphanyl-D-galactal (3a). The subsequent addition of
Those results are different from what we observed here (e.g., for-
mation of 2,3-unsaturated O-glycosides), indicating that the sub-
stituent at C3 plays a role in affecting the reactivity and needs to be
labile enough to promote Ferrier rearrangement.
In addition, exo-glycal 2 was subjected to the similar 2-step
procedure. The glycosidations were successful with various alco-
hols, including methanol, n-butanol, n-hexanol, allyl alcohol, ben-
zyl alcohol, isopropanol, and cyclohexanol. The resulting glycoside
products 23e2951c were obtained in 74e86% yields with exclusive
AlCl3 not only led to the possible chelation of C3-, C4- and C6-
substituents with the Lewis acid, but also facilitated the rear-
rangement to form the conjugated oxocarbenium ion intermediate
31. At this stage, the blockade of the sugar top face (caused by the
chelation) is critical to dominate the nucleophilic attack from the
bottom face, which explains the
a-stereoselectivity. The final
product (4) was obtained by the addition of hexanol (serving as the
nucleophile) to the oxocarbenium intermediate.
In conclusion,
a-2,3-unsaturated glycopyranosides were suc-
a
-stereoselectivity (Table 5).
cessfully prepared by glycosyl addition of endo-galactals with
Table 5
The glycosylations of exo-glycal 2 with varies alcoholsa
Entry
Acceptor (ROH)
Products (yield)b
i
ii
Methanol
n-Butanol
n-Hexanol
Allyl alcohol
Benzyl alcohol
Isopropanol
Cyclohexanol
23 (85%)
24 (84%)
25 (86%)
26 (86%)
27 (81%)
28 (74%)
29 (77%)
iii
iv
v
vi
vii
a
All reactions were carried out in the presence of AlCl3 (1.0 equiv) and alcohols (3.0 equiv).
b
The a-anomer is predominant with a/b
ratio on the basis of 1H NMR integration.
Scheme 1. The possible mechanism proposed to explain the formation of rearranged products.

354
Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
several O-nucleophiles, including simple alcohols and sugar de-
rivatives. The two-step synthesis was operated in one pot via tan-
dem phosphanylation and Ferrier rearrangement-mediated
glycosylation. This developed method was also applicable to the
addition of exo-glycals.
3.4. Methyl 4,6-di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside 5
Pale yellow oil; IR (CHCl3) 2945, 1585, 1398, 1099 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.27e7.17 (10H, m, ArH), 6.03 (1H, dd,
d
J3,4¼5.0 Hz, J3,2¼10.0 Hz, H3), 5.91 (1H, dd, J2,1¼2.5 Hz, J2,3¼10.0 Hz,
H2), 4.88 (1H, d, J1,2¼2.5 Hz, H1), 4.56 (1H, d, J¼12.0 Hz, CH2Ph),
4.55 (1H, d, J¼12.0 Hz, CH2Ph), 4.50 (1H, d, J¼12.0 Hz, CH2Ph), 4.47
(1H, d, J¼12.0 Hz, CH2Ph), 4.17e4.16 (1H, m, H5), 3.75 (1H, dd,
J6a,5¼6.5 Hz, J6a,6b¼10.0 Hz, H6a), 3.69 (1H, dd, J6b,5¼7.0 Hz,
3. Experimental section
3.1. General procedure
All purchased chemicals were of reagent grade. All reactions
were carried out under a nitrogen atmosphere and monitored by
J6b,6a¼10.0 Hz, H6b), 3.65e3.64 (1H, m, H4), 3.36 (3H, s, OCH3); 13
C
NMR (CDCl3, 100 MHz)
d 138.40, 138.27, 129.46, 128.34, 128.33,
TLC analysis (layer thickness: 250
m
m). Column chromatography
128.32, 128.31, 127.75, 127.74, 127.63, 127.57, 127.56, 127.55, 127.04,
95.07, 73.40, 70.99, 69.54, 69.46, 67.21, 55.45; FABMS m/z (rel
intens) 341 (MþHþ,1), 91 (100); HRMS (FAB) m/z calcd for C21H25O4
(MþHþ) 341.1747, found 341.1756. Anal. Calcd for C21H24O4; C:
74.09; H: 7.11. Found: C: 74.11; H: 7.14.
was carried out with silica gel 60 (70e230 mesh for gravity column,
or 230e400 mesh for flash column). Commercially available re-
agents were directly used without further purification unless oth-
erwise noted. Dichloromethane, ethyl acetate, hexanes, and
methanol were purchased from Mallinckrodt Chemical Co. The
following compounds were purchased from Acros Chemical Co,
including methanol, benzyl alcohol, n-hexanol, cyclohexanol, iso-
3.5. Benzyl 4,6-di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside 6
propanol, allyl alcohol, iodomethane, tri-O-acetyl-D-galactal, ben-
zyl chloride, potassium carbonate, sodium hydride, diethyl
chlorophosphite, triethylamine, 1,8-diazabicyclo[5.4.0]undec-7-
ene, 4-dimethylaminopyridine, potassium tert-butoxide, alumi-
num chloride, iron chloride, tin(IV) chloride, calcium chloride, zinc
chloride, mercury(II) sulfate, 1,2:3,4-di-O-isopropylidene-a-D-gal-
actopyranose. Proton NMR spectra were recorded at a Bruker
Pale yellow oil; IR (CHCl3) 2960, 1496, 1100 cmꢂ1
;
1H NMR
(CDCl3, 400 MHz) 7.27e7.15 (15H, m, ArH), 6.04 (1H, dd,
d
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.91 (1H, dd, J2,1¼3.2 Hz, J2,3¼10.0 Hz,
H2), 5.08 (1H, d, J1,2¼3.2 Hz, H1), 4.73 (1H, d, Ja,b¼11.6 Hz, CH2Ph),
4.56e4.45 (5H, m, CH2Ph), 4.27e4.23 (1H, m, H5), 3.75 (1H, dd,
J6a,5¼6.4 Hz, J6a,6b¼10.0 Hz, H6a), 3.67e3.63 (2H, m, H4, H6b); 13C
spectrometer (200 or 400 MHz) with CDCl3 (dH 7.24) and DMSO-d6
NMR (CDCl3, 100 MHz) d 138.45, 138.33, 137.87, 129.62, 128.35,
(
dH 2.50) as the internal standard; Carbon-13 NMR spectra were
128.34, 128.32, 128.31, 128.30, 128.29, 128.20, 128.19, 127.74, 127.73,
127.66, 127.65, 127.56, 127.54, 127.53, 127.12, 93.23, 73.41, 70.98,
69.68, 69.58, 69.55, 67.33; FABMS m/z (rel intens) 417 (MþHþ, 1), 91
(100); HRMS (FAB) m/z calcd for C27H29O4 (MþHþ) 417.2060, found
417.2064. Anal. Calcd for C27H28O4; C: 77.86; H: 6.78. Found: C:
77.88; H: 6.82.
recorded at 50 or 100 MHz with CDCl3 dC 77.0 (central line of
a triplet)]. Splitting patterns are shown by the abbreviations, such
as s (singlet), d (doublet), t (triplet), q (quartet), and m (multiplet).
[
3.2. Typical procedure of glycosylation for preparing 2,3-
unsaturated glycopyranoside derivatives 4e12, 33
3.6. Allyl 4,6-di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
To a solution of endo-galactal 1 (1.0 equiv) in anhydrous CH2Cl2
(1.5 mL) was added diethyl phosphorochloridite (1.2 equiv) and
Et3N (3.0 equiv). The reaction mixture was stirred at 0 ꢀC under N2
for 30 min. After the phosphanylation was completed, one equiv-
alent of AlCl3 and three equivalents of an alcohol substrate were
added into the reaction mixture and stirred at 0 ꢀC for 30 min. Once
the reaction was completed, the resulting solution was added to
CH2Cl2 (50 mL), washed with H2O (20 mLꢁ2), and brine (20 mLꢁ2).
The organic layer was collected, concentrated under reduced
pressure and purified by silica gel column chromatography with
33% EtOAc in hexanes to give the desired product (2,3-unsaturated
glycopyranosides 4e12 and 33) in 85e94 % yields.
enopyranoside 7
Pale yellow oil; IR (CHCl3) 2985, 1585, 1454, 1101 cmꢂ1; 1H NMR
(CDCl3, 400 MHz)
d 7.27e7.17 (10H, m, ArH), 6.05 (1H, dd,
J3,4¼5.6 Hz, J3,2¼10.0 Hz, H3), 5.93e5.81 (2H, m, H2, H20), 5.19 (1H,
0
0
0
0
0
0
0
dd, J3a ,3b ¼1.6 Hz, J3a ,2 ¼17.2 Hz, H3a ), 5.09 (1H, dd, J3b ,3a ¼1.6 Hz,
0
0
0
J3b ,3a ¼10.4 Hz, H3b ), 5.03 (1H, d, J1,2¼3.2 Hz, H1), 4.55 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.54 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.49 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.47 (1H, d, J¼11.6 Hz, CH2Ph), 4.23e4.17 (1H,
m, H10), 4.02e3.97 (1H, m, H5), 3.75 (1H, dd, J6a,5¼6.0 Hz,
J6a,6b¼10.0 Hz, H6a), 3.70e3.65 (2H, m, H4, H6b); 13C NMR (CDCl3,
100 MHz)
d 138.46, 138.33, 134.42, 129.60, 128.33, 128.32, 128.31,
128.30, 127.75, 127.74, 127.73, 127.55, 127.54, 127.53, 127.11, 117.37,
93.31, 73.39, 71.00, 69.54, 69.53, 68.71, 67.31; FABMS m/z (rel
intens) 367 (MþHþ, 5), 91 (100); HRMS (FAB) m/z calcd for
3.3. Hexyl 4,6-di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside 4
C
C
23H27O4 (MþHþ) 367.1904, found 367.1910. Anal. Calcd for
Pale yellow oil; IR (CHCl3) 2966, 1585, 1398, 1099 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.30e7.21 (10H, m, ArH), 6.07 (1H, dd,
23H26O4; C: 75.38; H: 7.15. Found: C: 75.39; H: 7.17.
d
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.95 (1H, dd, J2,1¼3.2 Hz, J2,3¼10.0 Hz,
H2), 5.01 (1H, d, J1,2¼3.2 Hz, H1), 4.61e4.50 (4H, m, CH2Ph),
4.26e4.22 (1H, m, H5), 3.81e3.68 (4H, m, H4, H6a, H6b, H1b0),
3.46e3.41 (1H, m, H1a0), 1.57e1.53 (2H, m, H20), 1.31e1.22 (6H, m,
H30, H40, H50), 0.83 (3H, t, J¼6.8 Hz, H60); 13C NMR (CDCl3, 100 MHz)
3.7. Isopropyl 4,6-di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside 8
Pale yellow oil; IR (CHCl3) 2972, 1642, 1493, 1094 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.26e7.17 (10H, m, ArH), 6.03 (1H, dd,
d
d
138.52, 138.36, 129.80, 128.32, 128.31, 128.30, 128.29, 127.74,
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.87 (1H, dd, J2,1¼3.2 Hz, J2,3¼10.0 Hz,
H2), 5.13 (1H, d, J1,2¼3.2 Hz, H1), 4.57e4.46 (4H, m, CH2Ph),
4.25e4.21 (1H, m, H5), 3.97e3.91 (1H, m, H10), 3.75 (1H, dd,
J6a,5¼6.0 Hz, J6a,6b¼10.0 Hz, H6a), 3.69e3.64 (2H, m, H4, H6b), 1.15
(3H, d, J¼6.4 Hz, H20), 1.09 (3H, d, J¼6.4 Hz, H30); 13C NMR (CDCl3,
127.73, 127.60, 127.54, 127.53, 127.52, 126.87, 90.05, 73.39, 70.98,
69.59, 69.45, 68.36, 67.37, 31.61, 29.72, 25.86, 22.58, 14.01; FABMS
m/z (rel intens) 411 (MþHþ, 1), 253 (6), 181 (22), 105 (22), 91 (100),
57 (73); HRMS (FAB) m/z calcd for C26H35O4 (MþHþ) 411.2530,
found 411.2538. Anal. Calcd for C26H34O4; C: 76.06; H: 8.35. Found:
C: 76.10; H: 8.37.
100 MHz)
d 138.53, 138.36, 130.19, 128.29, 128.28, 128.27, 128.26,
127.72, 127.71, 127.57, 127.49, 127.48, 127.47, 126.77, 92.32, 73.37,

Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
355
70.96, 69.69, 69.58, 69.27, 67.43, 23.58, 21.84; FABMS m/z (rel
intens) 369 (MþHþ, 6), 91 (100); HRMS (FAB) m/z calcd for
71.79, 69.11, 68.90, 59.18, 56.71, 33.77, 32.10, 25.64, 24.44, 24.24;
FABMS m/z (rel intens) 257 (MþHþ, 6), 91 (100); HRMS (FAB) m/z
calcd for C14H25O4 (MþHþ) 257.1747, found 257.1749. Anal. Calcd for
C
C
23H29O4 (MþHþ) 369.2060, found 369.2069. Anal. Calcd for
23H28O4; C: 74.97; H: 7.66. Found: C: 74.95; H: 7.62.
C14H24O4; C: 65.60; H: 9.44. Found: C: 65.64; H: 9.45.
3.8. Cyclohexyl 4,6-di-O-benzyl-2,3-dideoxy-
D
-threo-hex-2-
3.12. p-Methylphenyl-4,6-di-O-benzyl-2,3-dideoxy-D-threo-
enopyranoside 9
hex-2-enopyranoside 33
Pale yellow oil; IR (CHCl3) 2970, 1510, 1105 cmꢂ1
;
1H NMR
Pale yellow oil; IR (CHCl3) 2945, 1605, 1408, 1099 cmꢂ1; 1H NMR
(CDCl3, 500 MHz) 7.25e7.14 (10H, m, ArH), 6.99e6.93 (4H, m,
(CDCl3, 400 MHz) 7.26e7.17 (10H, m, ArH), 6.03 (1H, dd,
d
d
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.89 (1H, dd, J2,1¼2.8 Hz, J2,3¼10.0 Hz,
H2), 5.13 (1H, d, J1,2¼2.8 Hz, H1), 4.57e4.46 (4H, m, CH2Ph),
4.28e4.24 (1H, m, H5), 3.77e3.57 (4H, m, H4, H6, H10), 1.96e1.83
(2H, m, H20), 1.65e1.61 (2H, m, H60), 1.30e1.09 (6H, m, H30, H40,
ArH), 6.18e6.15 (1H, m, H3), 6.04 (1H, dd, J2,1¼3.0 Hz, J2,3¼10.0 Hz,
H2), 5.63 (1H, d, J1,2¼3.0 Hz, H1), 4.58 (1H, d, J¼12.0 Hz, CH2Ph),
4.52 (1H, d, J¼12.0 Hz, CH2Ph), 4.45 (1H, d, J¼11.5 Hz, CH2Ph), 4.41
(1H, d, J¼11.5 Hz, CH2Ph), 4.36e4.33 (1H, m, H5), 3.79 (1H, dd,
J6a,5¼6.5 Hz, J6a,6b¼10.0 Hz, H6a), 3.74 (1H, dd, J4,5¼2.5 Hz,
J4,3¼5.5 Hz, H4), 3.65 (1H, dd, J6b,5¼6.5 Hz, J6b,6a¼10.0 Hz, H6b), 2.21
H50); 13C NMR (CDCl3, 100 MHz)
d 138.55, 138.40, 130.35, 128.29,
128.28, 128.27, 128.26, 128.25, 127.70, 127.69, 127.57, 127.44, 127.43,
126.69, 92.24, 75.75, 73.33, 70.88, 69.71, 69.32, 67.50, 33.80, 32.09,
25.63, 24.42, 24.27; FABMS m/z (rel intens) 409 (MþHþ, 4), 91
(100); HRMS (FAB) m/z calcd for C26H33O4 (MþHþ) 409.2373, found
409.2382. Anal. Calcd for C26H32O4; C: 76.44; H: 7.90. Found: C:
76.48; H: 7.94.
(3H, s, CH3); 13C NMR (CDCl3, 125 MHz)
d 155.19, 138.35, 138.22,
131.56, 129.88, 129.87, 128.77, 128.38, 128.37, 128.26, 128.25, 127.85,
127.83, 127.82, 127.72, 127.63, 127.62, 127.49, 127.23, 127.22, 93.22,
73.35, 71.28, 70.28, 69.25, 67.06, 20.56.
3.13. Typical procedure of glycosylation for preparing 2,3-
3.9. Benzyl 4,6-di-O-methyl-2,3-dideoxy-
D
-threo-hex-2-
unsaturated glycopyranoside derivatives 17e23
enopyranoside 10
To a solution of endo-galactal 1 (1.0 equiv) in anhydrous CH2Cl2
(1.5 mL) was added diethyl phosphorochloridite (1.2 equiv) and
Et3N (3.0 equiv). The reaction mixture was stirred at 0 ꢀC under N2
for 30 min. After the phosphanylation was completed, one equiv-
alent of AlCl3 and three equivalents of a sugar alcohol substrate
were added into the reaction mixture and stirred at 0 ꢀC for 30 min.
Once the reaction was completed, the resulting solution was added
to CH2Cl2 (50 mL), washed with H2O (20 mLꢁ2), and brine
(20 mLꢁ2). The organic layer was concentrated under reduced
pressure and purified by column chromatography on silica gel (33%
EtOAc in hexanes as eluant) to give 2,3-unsaturated glycopyrano-
sides 17e23 in 81e86 % yields.
Pale yellow oil; IR (CHCl3) 2989, 1450, 1105 cmꢂ1
;
1H NMR
7.30e7.18 (5H, m, ArH), 6.13 (1H, dd, J3,4¼5.0 Hz,
(CDCl3, 500 MHz)
d
J3,2¼10.0 Hz, H3), 5.95 (1H, dd, J2,1¼3.0 Hz, J2,3¼10.0 Hz, H2), 5.06
(1H, d, J1,2¼3.0 Hz, H1), 4.74 (1H, d, J¼11.5 Hz, CH2Ph), 4.50 (1H, d,
J¼11.5 Hz, CH2Ph), 4.20e4.17 (1H, m, H5), 3.60 (1H, dd, J6a,5¼5.5 Hz,
J6a,6b¼10.0 Hz, H6a), 3.51 (1H, dd, J6b,5¼7.0 Hz, J6b,6a¼10.0 Hz, H6b),
3.44 (1H, dd, J4,5¼2.5 Hz, J4,3¼5.0 Hz, H4), 3.36 (3H, s, OCH3), 3.32
(1H, s, OCH3); 13C NMR (CDCl3, 125 MHz)
d 137.88, 129.84, 128.39,
128.38, 128.20, 128.19, 127.69, 126.62, 93.24, 71.79, 69.63, 69.36,
69.04, 59.24, 56.71; FABMS m/z (rel intens) 265 (MþHþ, 5), 91
(100); HRMS (FAB) m/z calcd for C15H21O4 (MþHþ) 265.1434, found
265.1441. Anal. Calcd for C15H20O4; C: 68.16; H: 7.63. Found: C:
68.18; H: 7.66.
3.14. 4,6-Di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside-(1/6)-1,2:3,4-di-O-isopropylidene-D-gal-
3.10. Isopropyl 4,6-di-O-methyl-2,3-dideoxy-D-threo-hex-2-
actopyranoside 17
enopyranoside 11
Pale yellow oil; IR (CHCl3) 2922, 1643, 1463, 1168 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.26e7.18 (10H, m, ArH), 6.02 (1H, dd,
Pale yellow oil; IR (CHCl3) 2968, 1490, 1105 cmꢂ1
;
1H NMR
6.11 (1H, dd, J3,4¼5.0 Hz, J3,2¼10.0 Hz, H3), 5.90
d
(CDCl3, 500 MHz)
d
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.90 0(1H, dd, J2,1¼2.8 Hz, J2,3¼10.0 Hz,
0
0
(1H, dd, J2,1¼3.0 Hz, J2,3¼10.0 Hz, H2), 5.07 (1H, d, J1,2¼3.0 Hz, H1),
4.17e4.14 (1H, m, H5), 3.96e3.91 (1H, m, H1), 3.58 (1H, dd,
J6a,5¼5.5 Hz, J6a,6b¼10.0 Hz, H6a), 3.52 (1H, dd, J6b,5¼7.0 Hz,
J6b,6a¼10.0 Hz, H6b), 3.43 (1H, dd, J4,5¼2.5 Hz, J4,3¼5.0 Hz, H4), 3.34
(3H, s, OCH3), 3.32 (3H, s, OCH3), 1.17 (3H, d, J¼6.5 Hz, CH3), 1.10 (3H,
H2), 5.43 (1H, d, J1 ,2 ¼5.2 Hz, H1 ), 5.04 (1H, d, J1,2¼2.8 Hz, H1),
4.57e4.45 (5H, m, H30, CH2Ph), 4.23e4.18 (3H, m, H5, H20, H40),
3.99e3.95 (1H, m, H50), 3.80e3.61 (5H, m, H4, H6, H60), 1.44 (3H, s,
CH3), 1.35 (3H, s, CH3), 1.26 (3H, s, CH3), 1.24 (3H, s, CH3); 13C NMR
(CDCl3, 100 MHz)
d 138.46, 138.26, 129.43, 128.29, 128.28, 128.26,
d, J¼6.5 Hz, CH3); 13C NMR (CDCl3,125 MHz)
d
130.38,126.28, 92.30,
128.25, 127.72, 127.71, 127.61, 127.60, 127.55, 127.47, 126.97, 109.18,
108.48, 96.30, 94.48, 73.35, 71.11, 70.83, 70.63, 70.60, 69.45, 69.14,
67.11, 66.60, 65.91, 26.04, 25.93, 24.89, 24.49; FABMS m/z (rel
intens) 569 (MþHþ, 1), 253 (6), 181 (22), 91 (100); HRMS (FAB) m/z
calcd for C32H41O9 (MþHþ) 569.2745, found 569.2755. Anal. Calcd
for C32H40O9; C: 67.59; H: 7.09. Found: C: 67.63; H: 7.12.
71.85, 69.75, 69.11, 68.91, 59.19, 56.71, 23.56, 21.87; FABMS m/z (rel
intens) 217 (MþHþ, 3), 91 (100); HRMS (FAB) m/z calcd for C11H21O4
(MþHþ) 217.1434, found 217.1440. Anal. Calcd for C11H20O4; C:
61.09; H: 9.32. Found: C: 61.12; H: 9.35.
3.11. Cyclohexyl 4,6-di-O-methyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside 12
3.15. 4,6-Di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside-(1/6)-1,2,3,4-tetra-O-methyl-D-glucopyrano-
side 18
Pale yellow oil; IR (CHCl3) 2959, 1550, 1105 cmꢂ1
;
1H NMR
6.10 (1H, dd, J3,4¼5.0 Hz, J3,2¼10.0 Hz, H3), 5.90
(CDCl3, 500 MHz)
d
(1H, dd, J2,1¼3.0 Hz, J2,3¼10.0 Hz, H2), 5.11 (1H, d, J1,2¼3.0 Hz, H1),
4.19e4.16 (1H, m, H5), 3.61e3.57 (2H, m, H6a, H10), 3.52 (1H, dd,
J6b,5¼7.0 Hz, J6b,6a¼10.0 Hz, H6b), 3.43 (1H, dd, J4,5¼2.5 Hz,
J4,3¼5.0 Hz, H4), 3.34 (3H, s, OCH3), 3.32 (3H, s, OCH3), 1.90e1.82
(2H, m, H20), 1.68e1.66 (2H, m, H60), 1.33e1.09 (6H, m, H30, H40,
Pale yellow oil; IR (CHCl3) 2918, 1641, 1453, 1100 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.26e7.18 (10H, m, ArH), 6.03 (1H, dd,
d
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.90 (1H, dd, J2,1¼2.8 Hz, J2,3¼10.0 Hz,
0
0
0
H2), 5.07 (1H, d, J1,2¼2.8 Hz, H1), 4.70 (1H, d, J1 ,2 ¼3.6 Hz, H1 ),
4.57e4.47 (4H, m, CH2Ph), 4.20e40.16 (1H, m, H5), 3.92 (1H, dd,
H50); 13C NMR (CDCl3, 125 MHz)
d
130.48, 126.22, 92.21, 75.74,
J6a ,5 ¼4.0 Hz, J6a ,6b ¼11.2 Hz, H6a ), 3.75 (1H, dd, J6a,5¼6.4 Hz,
0
0
0
0

356
Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
J6a,6b¼10.0 Hz, H6a), 3.67e3.60 (3H, m, H4, H6b, H6b0), 3.54e3.50
(4H, m, H50, OCH3), 3.44e3.39 (7H, m, H30, 2ꢁOCH3), 3.31 (3H, s,
OCH3), 3.12e3.07 (2H, m, H20, H40); 13C NMR (CDCl3, 50 MHz)
ArH), 6.79 (2H, d, J¼7.5 Hz, ArH), 6.75 (2H, d, J¼7.5 Hz, ArH), 5.98 (1H,
dd, J3,4¼5.5 Hz, J3,2¼10.0 Hz, H3), 5.88 (1H, dd, J2,1¼4.0 Hz,
J2,3¼10.0 Hz, H2), 5.43 (1H, d, J1,2¼4.0 Hz, H1), 5.03 (1H, brs, H10),
4.50e4.39 (5H, m, CH2Ph, H40), 4.23e4.16 (3H, m, H20, H30, H5),
3.97e3.95 (1H, m, H50), 3.79e3.68 (9H, m, H60, H6a, OCH3), 3.60e3.57
(2H, m, H4, H6b), 1.44 (3H, s, CH3), 1.36 (3H, s, CH3), 1.26 (3H, s, CH3),
d
138.46, 138.25, 129.43, 128.29, 128.28, 128.26, 128.25, 127.72,
127.71, 127.61, 127.60, 127.55, 127.47, 126.97, 109.18, 108.48, 96.30,
94.48, 73.35, 71.11, 70.83, 70.63, 70.60, 69.45, 69.14, 67.11, 66.60,
65.91, 26.04, 25.93, 24.89, 24.49; LRMS (EI) m/z (rel intens) 544
(Mþ, 1), 394 (11), 91 (100); HRMS (EI) m/z calcd for C30H40O9 (Mþ)
544.2672, found 544.2676. Anal. Calcd for C30H40O9; C: 66.16; H:
7.40. Found: C: 66.19; H: 7.45.
1.24 (3H, s, CH3); 13C NMR (CDCl3, 125 MHz)
d 159.19, 159.15, 130.59,
130.38, 129.40, 129.39, 129.33, 129.32, 129.21, 127.19, 113.77, 113.76,
113.71, 113.70,109.21, 108.53, 96.33, 94.53, 73.03, 70.88, 70.84, 70.65,
70.61, 69.46, 68.82, 66.75, 66.60, 65.92, 55.23, 55.22, 26.08, 25.97,
24.93, 24.51; FABMS m/z (rel intens) 629 (MþHþ, 3), 91 (100); HRMS
(FAB) m/z calcd for C34H45O11 (MþHþ) 629.2956, found 629.2961.
Anal. Calcd for C34H44O11; C: 64.95; H: 7.05. Found: C: 64.98; H: 7.07.
3.16. 4,6-Di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside-(1/6)-1-methyl-2,3,4-tri-O-benzyl-D-gluco-
pyranoside 19
3.19. 4,6-Di-O-p-mthoxybenzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside-(1/6)-1-methyl-2,3,4-tri-O-benzyl-D-gluco-
pyranoside 22
Pale yellow oil; IR (CHCl3) 2920, 1643, 1454, 1099 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.28e7.14 (25H, m, ArH), 6.01 (1H, dd,
d
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.91 (1H, dd, J2,1¼2.8 Hz, J2,3¼10.0 Hz,
H2), 5.06 (1H, d, J1,2¼2.8 Hz, H1), 4.88 (1H, d, Ja,b¼10.8 Hz, CH2Ph),
4.76 (1H, d, Ja,b¼10.8 Hz, CH2Ph), 4.71 (1H, d, Ja,b¼10.8 Hz, CH2Ph),
4.69 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.58 (1H, d, Ja,b¼10.8 Hz, CH2Ph),
Pale yellow oil; IR (CHCl3) 2920, 1640, 1501, 1109 cmꢂ1; 1H NMR
(CDCl3, 500 MHz) 7.26e7.17 (15H, m, ArH), 7.11e7.09 (2H, m, ArH),
d
7.07e7.05 (2H, m, ArH), 6.75e6.72 (4H, m, ArH), 5.98e5.96 (1H, m,
H3), 5.90e5.87 (1H, m, H2), 5.04 (1H, brs, H1), 4.87 (1H, d,
Ja,b¼11.0 Hz, CH2Ph), 4.75 (1H, d, Ja,b¼11.0 Hz, CH2Ph), 4.71 (1H, d,
Ja,b¼11.0 Hz, CH2Ph), 4.69 (1H, d, Ja,b¼11.0 Hz, CH2Ph), 4.59e4.56
(2H, m, CH2Ph), 4.53 (1H, brs, H10), 4.44 (1H, d, Ja,b¼11.0 Hz, CH2Ph),
4.38 (1H, d, Ja,b¼11.0 Hz, CH2Ph), 4.30 (1H, d, Ja,b¼12.0 Hz, CH2Ph),
4.24 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.11 (1H, brs, H5), 3.98e3.96 (1H,
m, H50), 3.91e3.88 (1H, m, H30), 3.70e3.64 (9H, m, H60, H6a, OCH3),
3.58 (1H, brs, H4), 3.51e3.42 (3H, m, H40, H20, H6b), 3.28 (3H, s,
0
0
0
4.57 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.53 (1H, d, J1 ,2 ¼3.6 Hz, H1 ), 4.51
(1H, d, Ja,b¼10.8 Hz, CH2Ph), 4.45 (1H, d, Ja,b¼10.8 Hz, CH2Ph), 4.37
(1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.31 (1H, d, Ja,b¼12.0 Hz, CH2Ph),
0
0
0
0
4.17e4.14 (1H, m, H5), 3.98 (1H, dd, J6a ,5 ¼3.60Hz, J6a ,6b ¼11.2 Hz,
H6a0), 3.90 (1H, dd, J3 ,4 ¼9.6 Hz, J3 ,2 ¼9.6 Hz, H3 ), 3.72e3.62 (4H, m,
0
0
0
0
H4, H6a, H50, H6b0), 3.57e3.48 (2H, m, H40, H6b), 3.43 (1H, dd,
J2 ,1 ¼3.6 Hz, J2 ,3 ¼9.6 Hz, H2 ), 3.28 (3H, s, OCH3); 13C NMR (CDCl3,
0
0
0
0
0
50 MHz)
d 138.39, 138.34, 138.15, 138.14, 129.45, 128.41, 128.40,
128.39,128.36,128.35,128.34,128.33,128.29,128.28,128.27,128.02,
128.01, 127.89, 127.88, 127.87, 127.74, 127.73, 127.72, 127.71, 127.59,
127.52, 127.51, 127.50, 126.87, 98.01, 94.53, 81.97, 79.86, 77.77, 75.69,
74.94, 73.28, 73.27, 71.07, 70.00, 69.57, 69.08, 66.97, 66.64, 55.11;
FABMS m/z (rel intens) 795 (MþNaþ, 2), 105 (32), 191 (100); HRMS
(FAB) m/z calcd for C48H52NaO9 (MþNaþ) 795.3504, found 795.3507.
Anal. Calcd for C48H52O9; C: 74.59; H: 6.78. Found: C: 74.66; H: 6.84.
OCH3); 13C NMR (CDCl3, 125 MHz)
d 159.18, 159.09, 138.81, 138.39,
138.19, 130.56, 130.31, 129.38, 129.37, 129.25, 129.20, 129.19, 128.42,
128.41,128.40,128.37,128.36,128.34,128.33,128.32,128.04,128.03,
127.90, 127.89, 127.85, 127.77, 127.76, 127.63, 127.51, 127.05, 113.70,
113.69, 98.04, 94.57, 82.00, 79.92, 77.81, 75.70, 74.96, 73.31, 72.97,
70.82, 70.03, 69.61, 68.81, 66.66, 66.65, 55.23, 55.22, 55.13; FABMS
m/z (rel intens) 833 (MþHþ, 4), 91 (100); HRMS (FAB) m/z calcd for
C
C
50H57O11 (MþHþ) 833.3895, found 8.33.3897. Anal. Calcd for
3.17. 4,6-Di-O-benzyl-2,3-dideoxy-D-threo-hex-2-
50H56O11; C: 72.10; H: 6.78. Found: C: 72.15; H: 6.84.
enopyranoside-(1/3)-1,2:5,6-di-O-isopropylidene-D-gluco-
furanoside 20
3.20. Typical glycosylation procedure (synthesis of 23)
Pale yellow oil; IR (CHCl3) 2926, 1646, 1463, 1095 cmꢂ1; 1H NMR
(CDCl3, 400 MHz) 7.27e7.17 (10H, m, ArH), 6.05 (1H, dd,
J3,4¼5.2 Hz, J3,2¼10.0 Hz, H3), 5.89 (1H, dd, J2,1¼2.4 Hz, J2,3¼10.0 Hz,
To a solution of exo-galactal 2 (1.0 equiv) in anhydrous CH2Cl2
(1.5 mL) was added diethyl phosphorochloridite (1.2 equiv) and
Et3N (3.0 equiv). The reaction mixture was stirred at 0 ꢀC under N2
for 30 min. After the phosphanylation was completed, one equiv-
alent of AlCl3 and three equivalents of methanol were added into
the reaction mixture and stirred at 0 ꢀC for 30 min. Once the re-
action was completed, the resulting solution was added to CH2Cl2
(50 mL), washed with H2O (20 mLꢁ2), and brine (20 mLꢁ2). The
organic layer was concentrated under reduced pressure and puri-
fied by column chromatography on silica gel (15% EtOAc in hexanes
as eluant) to give 23 in 85% yields.
d
0
0
0
H2), 5.76 (1H, d, J1 ,2 ¼3.6 Hz, H1 ), 5.23 (1H, d, J1,2¼2.4 Hz, H1), 4.73
0
0
0
(1H, d, J2 ,1 ¼3.6 Hz, H2 ), 4.56 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.54 (1H,
d, Ja,b¼12.0 Hz, CH2Ph), 4.48 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.44 (1H, d,
0
0
0
Ja,b¼12.0 Hz, CH2Ph), 4.23 (1H, d, J3 ,4 ¼2.8 Hz, H3 ), 4.18e4.12 (2H,
m, H5, H50), 4.04e3.99 (2H,0 m, H40, H6b0), 3.89 (1H, dd,
0
0
0
0
J6a ,5 ¼5.6 Hz, J6a ,6b ¼8.4 Hz, H6a ), 3.71 (1H, d, J6,5¼6.0 Hz, H6), 3.63
(1H, dd, J4,5¼2.4 Hz, J4,3¼5.2 Hz, H4), 1.39 (3H, s, CH3), 1.33 (3H, s,
CH3), 1.25 (3H, s, CH3), 1.09 (3H, s, CH3); 13C NMR (CDCl3, 50 MHz)
d
138.23, 138.22, 129.16, 128.38, 128.37, 128.36, 128.35, 127.75,
127.74, 127.73, 127.60, 127.59, 127.58, 127.04, 111.76, 109.03, 105.38,
95.71, 83.92, 81.41, 81.23, 73.66, 72.70, 70.90, 70.37, 69.96, 67.70,
67.29, 26.88, 26.82, 26.09, 25.39; FABMS m/z (rel intens) 569
(MþHþ, 3), 91 (100); HRMS (FAB) m/z calcd for C32H41O9 (MþHþ)
569.2745, found 569.2746. Anal. Calcd for C32H40O9; C: 67.59; H:
7.09. Found: C: 67.61; H: 7.12.
3.21. Methyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-a-D-galacto-
oct-3-ulo-1-enopyranoside 23
IR (CHCl3) 2960, 1642, 1493, 1094 cmꢂ1
;
1H NMR (CDCl3,
0
0
400 MHz)
d
7.28e7.17 (20H, m, ArH), 5.77 (1H, dd, J1 ,2b ¼10.8 Hz,
0
0
0
0
0
0
0
J1 ,2a ¼17.6 Hz, H1 ), 5.43 (1H, dd, J2a ,2b ¼2.0 Hz, J2a ,1 ¼17.6 Hz,
H2a0), 5.21 (1H, dd, J2b ,2a ¼2.0 Hz, J2b ,1 ¼10.8 Hz, H2b ), 4.88 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.77 (1H, d, Ja,b¼10.8 Hz, CH2Ph), 4.69 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.64 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.54 (1H, d,
Ja,b¼10.8 Hz, CH2Ph), 4.53 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.43 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.37 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 3.97 (1H, dd,
J3,4¼2.8 Hz, J3,2¼10.0 Hz, H3), 3.90 (1H, dd, J4,5¼0.8 Hz, J4,3¼2.8 Hz,
H4), 4.06e4.03 (1H, m, H5), 3.94 (1H, brs, H4), 3.72 (1H, d,
0
0
0
0
0
3.18. 4,6-Di-O-p-mthoxybenzyl-2,3-dideoxy-D-threo-hex-2-
enopyranoside-(1/6)-1,2:3,4-di-O-isopropylidene-D-gal-
actopyranoside 21
Pale yellow oil; IR (CHCl3) 2952, 1645, 1464, 1170 cmꢂ1; 1H NMR
(CDCl3, 500 MHz)
7.18 (2H, d, J¼7.5 Hz, ArH), 7.12 (2H, d, J¼7.5 Hz,
d

Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
357
0
0
0
0
0
00 00
J2,3¼9.6 Hz, H2), 3.79e3.72 (2H, m, H2, H5), 3.56 (1H, dd,
J6a,5¼6.8 Hz, J6a,6b¼9.6 Hz, H6a), 3.51 (1H, dd, J6b,5¼6.0 Hz,
J6b,6a¼9.6 Hz, H6b), 3.07 (3H, s, OCH3); 13C NMR (CDCl3, 100 MHz)
J2a ,1 ¼17.6 Hz, J2a ,2b ¼1.6 Hz, H2a ), 5.25 (1H, dd, J3a ,2 ¼11.6 Hz,
00
0
00
00
0
0
0
0
J3a ,3b ¼1.6 Hz, H3a ),5.22(1H,dd, J2b ,1 ¼17.6Hz, J2b ,2a ¼1.6Hz,H2b ),
00
00 00
5.08 (1H, dd, J3b ,2 ¼10.4 Hz, H3b ), 4.95 (1H, d, Ja,b¼11.6 Hz, CH2Ph),
4.87 (1H, d, Ja,b¼11.2 Hz, CH2Ph), 4.75 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.72
(1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.63 (1H, d, Ja,b¼11.2 Hz, CH2Ph), 4.60 (1H,
d, Ja,b¼11.6 Hz, CH2Ph), 4.49 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.45 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 3.99e3.83 (5H, m, H2, H4, H5, H6a, H6b),
d
138.93, 138.71, 138.18, 138.09, 134.64, 128.64, 128.63, 128.62,
128.35, 128.34, 128.33, 128.32, 128.14, 128.13, 128.12, 128.11, 127.98,
127.97, 127.96, 127.69, 127.68, 127.67, 127.64, 127.63, 127.55, 127.48,
127.47, 127.46, 127.45, 118.99, 100.01, 80.49, 80.31, 76.05, 75.09,
74.47, 73.46, 73.01, 70.36, 69.12, 49.07; FABMS m/z (rel intens) 581
(MþHþ, 4), 91 (100); HRMS (FAB) m/z calcd for C37H41O6 (MþHþ)
581.2898, found 581.2902. Anal. Calcd for C37H40O6; C: 76.53; H:
6.94. Found: C: 76.59; H: 6.97.
3.64e3.55 (2H, m, H1a00, H1b00); 13C NMR (CDCl3, 100 MHz)
d 138.99,
138.77, 138.45, 138.17, 135.26, 135.11, 128.40, 128,39, 128.38, 128.37,
128.36, 128.19, 128.18, 128.17, 128.16, 128.15, 128.02, 128.01, 127.69,
127.68, 127.67, 127.49, 127.48, 127.47, 127.46, 127.45, 118.65, 116.30,
100.25, 80.39, 75.76, 75.04, 74.51, 73.41, 72.91, 70.45, 69.02, 63.06;
FABMS m/z (rel intens) 607 (MþHþ, 7), 91 (100); HRMS (FAB) m/z
calcd for C39H43O6 (MþHþ) 607.3054, found 607.3061. Anal. Calcd for
3.22. n-Butyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-a-D-galacto-
oct-3-ulo-1-enopyranoside 24
C
39H42O6; C: 77.20; H: 6.98. Found: C: 77.24; H: 6.73.
IR (CHCl3) 2950,1641,1453,1090 cmꢂ1; 1H NMR (CDCl3, 400 MHz)
0
0
0
0
d
7.27e7.18 (20H, m, ArH), 5.82 (1H, dd, J1 ,2b ¼10.8 Hz, J1 ,2a ¼17.6 Hz,
3.25. Benzyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-a-D-galacto-
oct-3-ulo-1-enopyranoside 27
H10), 5.41 (1H, dd, J2a ,2b ¼2.0 Hz,0J2a ,1 ¼17.6 Hz, H2a ), 5.14 (1H, dd,
0
0
0
0
0
0
0
0
0
J2b ,2a ¼2.0 Hz, J2b ,1 ¼10.8 Hz, H2b ), 4.87 (1H, d, Ja,b¼11.6 Hz, CH2Ph),
4.79(1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.68 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.64
(1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.55 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.53 (1H,
d, Ja,b¼11.6 Hz, CH2Ph), 4.43 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.38 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.00 (1H, dd, J3,4¼2.8 Hz, J3,2¼10.0 Hz, H3), 3.92
(1H, dd, J4,5¼1.2 Hz, J4,3¼2.8 Hz, H4), 3.82e3.79 (1H, m, H5), 3.75 (1H,
d, J2,3¼10.0 Hz, H2), 3.56 (1H, dd, J6a,5¼7.2 Hz, J6a,6b¼9.6 Hz, H6a), 3.50
(1H, dd, J6b,5¼6.0 Hz, J6b,6a¼9.6 Hz, H6b), 3.33e3.19 (2H, m, H100),
1.50e1.45 (2H,00 m, H200), 1.26e1.18 (2H, m, H300), 0.81 (3H, t,
IR (CHCl3) 2950,1651,1503,1102 cmꢂ1; 1H NMR (CDCl3, 400 MHz)
0
0
0
0
d
7.25e7.16 (25H, m, ArH), 5.91 (1H, dd, J1 ,2b ¼10.8 Hz, J1 ,2a ¼17.6 Hz,
H10), 5.51 (1H, dd, J2a ,2b ¼2.0 Hz,0J2a ,1 ¼17.6 Hz, H2a ), 5.21 (1H, dd,
0
0
0
0
0
0
0
0
0
J2b ,2a ¼2.0 Hz, J2b ,1 ¼10.8 Hz, H2b ), 4.86 (1H, d, Ja,b¼11.6 Hz, CH2Ph),
4.82 (1H, d, Ja,b¼11.2 Hz, CH2Ph), 4.66 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.63
(1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.57 (1H, d, Ja,b¼11.2 Hz, CH2Ph), 4.52 (1H,
d, Ja,b¼11.6 Hz, CH2Ph), 4.44 (1H, d, Ja,b¼12.8 Hz, CH2Ph), 4.38e4.32
(3H, m, CH2Ph), 4.04 (1H, dd, J3,4¼2.8 Hz, J3,2¼10.0 Hz, H3), 3.90 (1H,
dd, J4,5¼1.2 Hz, J4,3¼2.8 Hz, H4), 3.81 (1H, d, J2,3¼10.0 Hz, H2),
3.79e3.76 (1H, m, H5), 3.53 (1H, dd, J6a,5¼7.2 Hz, J6a,6b¼9.6 Hz, H6a),
3.43 (1H, dd, J6b,5¼6.0 Hz, J6b,6a¼9.6 Hz, H6b); 13C NMR (CDCl3,
J4 ,3 ¼7.2 Hz, H4 ); 13C NMR (CDCl3,100 MHz)
d
139.02,138.80,138.57,
00
0
138.19, 135.71, 128.37, 128.36, 128.35, 128.31, 128.30, 128.29, 128.17,
128.16, 128.15, 128.11, 128.10, 127.99, 127.98, 127.74, 127.73, 127.72,
127.47,127.46,127.44,127.43,118.30, 99.87, 80.64, 80.35, 75.65, 75.06,
74.47, 73.44, 72.86, 70.30, 69.15, 61.60, 31.83,19.57,13.97; FABMS m/z
(rel intens) 623 (MþHþ, 3), 91 (100); HRMS (FAB) m/z calcd for
100 MHz)
d 139.02, 138.89, 138.74, 138.68, 138.18, 135.41, 128.35,
128,34, 128.29, 128.28, 128.17, 128.16, 128.15, 128.14, 128.13, 128.12,
128.11, 128.10, 127.98, 127.97, 127.69, 127.68, 127.61, 127.49, 127.48,
127.47, 127.46, 127.42, 127.41, 127.40, 127.01, 118.84, 100.54, 80.62,
80.20, 75.56, 74.98, 74.48, 73.36, 72.80, 70.53, 68.99, 63.78; FABMS m/
z (rel intens) 657 (MþHþ, 3), 91 (100); HRMS (FAB) m/z calcd for
C
C
40H47O6 (MþHþ) 623.3367, found 623.3373. Anal. Calcd for
40H46O6; C: 77.14; H: 7.44. Found: C: 77.19; H: 7.48.
3.23. n-Hexyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-
a
-
D
-galacto-
C
43H45O6 (MþHþ)657.3211, found657.3214.Anal. CalcdforC43H44O6;
oct-3-ulo-1-enopyranoside 25
C: 78.63; H: 6.75. Found: C: 78.65; H: 6.78.
IR (CHCl3) 2958, 1640, 1498, 1100 cmꢂ1
;
1H NMR (CDCl3,
3.26. Isopropyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-a-D-gal-
acto-oct-3-ulo-1-enopyranoside 28
0
0
400 MHz)
d
7.26e7.17 (20H, m, ArH), 5.77 (1H, dd, J1 ,2b ¼10.8 Hz,
0
0
0
0
0
0
0
0
J1 ,2a ¼17.6 Hz, H1 ), 5.41 (1H, dd, J2a ,2b ¼2.0 Hz, J2a ,1 ¼17.6 Hz, H2a ),
5.14 (1H, dd, J2b ,2a ¼2.0 Hz, J2b ,1 ¼10.8 Hz, H2b ), 4.87 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.79 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.68 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.64 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.55 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.53 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.43 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.37 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.00 (1H, dd,
J3,4¼2.8 Hz, J3,2¼10.0 Hz, H3), 3.92 (1H, dd, J4,5¼1.6 Hz, J4,3¼2.8 Hz,
H4), 3.82e3.79 (1H, m, H5), 3.75 (1H, d, J2,3¼10.0 Hz, H2), 3.56 (1H,
dd, J6a,5¼7.2 Hz, J6a,6b¼9.6 Hz, H6a), 3.50 (1H, dd, J6b,5¼6.0 Hz,
J6b,6a¼9.6 Hz, H6b), 3.32e3.18 (2H, m, H100), 1.51e1.46 (2H, m, H200),
IR (CHCl3) 2935, 1635, 1498, 1090 cmꢂ1
;
1H NMR (CDCl3,
0
0
0
0
0
0
0
400 MHz)
d
7.26e7.17 (20H, m, ArH), 5.95 (1H, dd, J1 ,2b ¼10.8 Hz,
0
0
0
0
0
0
0
0
J1 ,2a ¼17.6 Hz, H1 ), 5.44 (1H, dd, J2a ,2b ¼2.0 Hz, J2a ,1 ¼17.6 Hz, H2a ),
0
0
0
0
0
5.11 (1H, dd, J2b ,2a ¼2.0 Hz, J2b ,1 ¼10.8 Hz, H2b ), 4.86 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.83 (1H, d, Ja,b¼11.2 Hz, CH2Ph), 4.68 (2H, brs,
CH2Ph), 4.54 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.52 (1H, d, Ja,b¼11.6 Hz,
CH2Ph), 4.43 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.39 (1H, d, Ja,b¼12.0 Hz,
CH2Ph), 4.02e3.95 (3H, m, H3, H4, H5), 3.93e3.85 (1H, m, H100), 3.71
(1H, d, J2,3¼10.0 Hz, H2), 3.58 (1H, dd, J6a,5¼7.6 Hz, J6a,6b¼9.6 Hz,
H6a), 3.50 (1H, dd, J6b,5¼6.0 Hz, J6b,6a¼9.6 Hz, H6b), 1.09 (1H, d,
J¼2.4 Hz, H200),1.07 (1H, d, J¼2.4 Hz, H300); 13C NMR (CDCl3,100 MHz)
1.25e1.17 (6H, m, H300, H400, H500), 0.79 (3H, t, J6 ,5 ¼7.2 Hz, H6 ); 13C
00
00
0
NMR (CDCl3, 100 MHz)
d 139.02, 138.81, 138.77, 138.20, 135.74,
128.28, 128,27, 128.26, 128.25, 128.14, 128.13, 128.12, 128.11, 128.10,
128.09, 127.99, 127.98, 127.97, 127.66, 127.65, 127.43, 127.42, 127.41,
127.40, 127.39, 118.28, 99.90, 80.64, 80.35, 75.62, 75.09, 74.46,
73.44, 72.85, 70.32, 69.18, 61.91, 31.66, 29.68, 25.98, 22.61, 14.04;
FABMS m/z (rel intens) 651 (MþHþ, 5), 91 (100); HRMS (FAB) m/z
calcd for C42H51O6 (MþHþ) 651.3680, found 651.3682. Anal. Calcd
for C42H50O6; C: 77.51; H: 7.74. Found: C: 77.54; H: 7.79.
d 139.03,138.78,138.70,138.15,136.47,128.37,128,36,128.29,128.28,
128.15, 128.14, 128.13, 128.12, 127.94, 127.93, 127.90, 127.89, 127.64,
127.63, 127.62, 127.39, 127.38, 127.37, 127.36, 127.33, 117.45, 100.17,
81.08, 80.45, 75.56, 74.65, 74.34, 73.41, 72.59, 70.22, 69.00, 65.27,
24.17, 23.06; FABMS m/z (rel intens) 609 (MþHþ, 4), 91 (100); HRMS
(FAB) m/z calcd for C39H45O6 (MþHþ) 609.3211, found 609.3215.
Anal. Calcd for C39H44O6; C: 76.95; H: 7.29. Found: C: 76.98; H: 7.31.
3.24. Allyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-
a-
D-galacto-oct-
3.27. Cyclohexyl 4,5,6,8-tetra-O-benzyl-1,2-dideoxy-a-D-gal-
3-ulo-1-enopyranoside 26
acto-oct-3-ulo-1-enopyranoside 29
IR (CHCl3) 2960,1642,1493,1094 cmꢂ1; 1H NMR (CDCl3, 400 MHz)
IR (CHCl3) 2945, 1632, 1499, 1104 cmꢂ1
;
1H NMR (CDCl3,
d
7.36e7.25 (20H, m, ArH), 5.98e5.87 (2H, m, H10, H200), 4.52 (1H, dd,
400 MHz)
d
7.28e7.16 (20H, m, ArH), 6.96 (1H, dd, J1 ,2b ¼11.2 Hz,
0
0

358
Y.-B. Chen et al. / Tetrahedron 71 (2015) 350e358
0
0
13. Masson, C.; Soto, J.; Bessodes, M. Synlett 2000, 1281e1282.
14. (a) Babu, B. S.; Balasubramanian, K. K. Tetrahedron Lett. 2000, 41, 1271e1274; (b)
Yadav, J. S.; Reddy, B. V. S.; Raman, J. V.; Niranjan, N.; Kumar, S. K.; Kunwar, A. C.
Tetrahedron Lett. 2002, 43, 2095e2098; (c) Das, S. K.; Reddy, K. A.; Abbineni, C.;
Roy, J.; Rao, K. V. L. N.; Sachwani, R. H.; Iqbal, J. Tetrahedron Lett. 2003, 44,
4507e4509; (d) Das, S. K.; Reddy, K. A.; Roy, J. Synlett 2003, 1607e1610.
15. (a) Toshima, K.; Miyamoto, N.; Matsuo, G.; Nakata, M.; Matsumura, S. Chem.
Commun. 1996, 1379e1380; (b) Shanmugasundaram, B.; Bose, A. K.; Balasu-
bramanian, K. K. Tetrahedron Lett. 2002, 43, 6795e6798; (c) de Oliveira, R. N.; de
Freitas Filho, J. R.; Srivastava, R. M. Tetrahedron Lett. 2002, 43, 2141e2143.
16. (a) Grynkiewiez, G.; Priebe, W.; Zamojski, A. Carbohydr. Res. 1979, 68, 33e41;
(b) Bhate, P.; Horton, D.; Priebe, W. Carbohydr. Res. 1985, 144, 331e337.
17. Rafiee, E.; Tangestaninejad, S.; Habibi, M. H.; Mirkhani, V. Bioorg. Med. Chem.
Lett. 2004, 14, 3611e3614.
0
0
0
0
0
0
0
J1 ,2a ¼17.6 Hz, H1 ), 5.46 (1H, dd, J2a ,2b ¼2.4 Hz, J2a ,1 ¼17.6 Hz, H2a ),
0
0
0
0
5.10 (1H, dd, J2b ,2a ¼2.4 Hz, J2b ,1 ¼11.2 Hz, H2b ), 4.87 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.84 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.67 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.64 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.54 (1H, d,
Ja,b¼11.6 Hz, CH2Ph), 4.53 (1H, d, Ja,b¼11.6 Hz, CH2Ph), 4.44 (1H, d,
Ja,b¼12.0 Hz, CH2Ph), 4.39 (1H, d, Ja,b¼12.0 Hz, CH2Ph), 4.05e4.02
(1H, m, H5), 3.98 (1H, dd, J3,4¼1.6 Hz, J3,2¼9.6 Hz, H3), 3.94 (1H, dd,
J4,5¼0.8 Hz, J4,3¼2.4 Hz, H4), 3.70 (1H, d, J2,3¼9.6 Hz, H2), 3.58 (1H,
dd, J6a,5¼7.2 Hz, J6a,6b¼9.6 Hz, H6a), 3.55e3.47 (2H, m, H6b, H100),
1.78e1.71 (2H, m, H200), 1.63e1.59 (2H, m, H600), 1.35e1.05 (6H, m,
H6b, H300, H400, H500); 13C NMR (CDCl3, 50 MHz)
d 139.14, 138.85,
18. Swamy, R. N.; Venkateshwarlu, A. Synthesis 2002, 598e600.
19. Yadav, J. S.; Reddy, B. V. S.; Reddy, J. S. S. J. Chem. Soc., Perkin Trans. 1 2002,
2390e2394.
138.28, 136.70, 128.29, 128.28, 128.27, 128.14, 128.13, 128.12, 128.11,
128.10, 127.87, 127.81, 127.80, 127.61, 127.60, 127.59, 127.58, 127.39,
127.38, 127.37, 127.36, 127.35, 117.39, 100.30, 81.31, 80.37, 75.37,
74.90, 74.37, 73.41, 72.63, 71.48, 70.34, 69.14, 34.18, 33.88, 25.56,
24.87, 24.65; FABMS m/z (rel intens) 649 (MþHþ, 3), 91 (100); HRMS
(FAB) m/z calcd for C42H49O6 (MþHþ) 649.3524, found 649.3527.
Anal. Calcd for C42H48O6; C: 77.75; H: 7.46. Found: C: 77.78; H: 7.48.
20. Yadav, J. S.; Reddy, B. V. S.; Reddy, K. B.; Satyanarayana, M. Tetrahedron Lett.
2002, 43, 7009e7012.
21. Bettadaiah, B. K.; Srinivas, P. Tetrahedron Lett. 2003, 44, 7257e7259.
22. (a) Yadav, J. S.; Reddy, B. V. S.; Murthy, C. V. S. R.; Kumar, G. M. Synlett 2000,
1450e1451; (b) Yadav, J. S.; Reddy, B. V. S.; Chand, P. K. Tetrahedron Lett. 2001,
42, 4057e4059; (c) Yadav, J. S.; Reddy, B. V. S.; Geetha, V. Synth. Commun. 2003,
33, 717e722.
23. Lopez, J. C.; Fraser-Reid, B. J. Chem. Soc., Chem. Commun. 1992, 94e96.
24. (a) Dawe, R. D.; Fraser-Reid, B. J. Chem. Soc., Chem. Commun. 1981, 1180e1181;
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Acknowledgements
The authors thank the Ministry of Science and Technology of
Taiwan (MOST 103-2113-M-039-004) and China Medical Univer-
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