Regioselective C-3-O-acylation and O-methylation of 4,6-O-benzylidene-β-D-gluco- and galactopyranosides displaying a range of anomeric substituents

Article abstract of DOI:10.1016/S0008-6215(01)00063-5

The regioselective C-3-O-acylation and O-methylation of a range of 4,6-O-benzylidene-β-D-gluco- and galactopyranosides has been studied. Regioselectivity is achieved by forming the copper chelate of the 2,3-diol using either sodium hydride and copper(II) chloride, or copper(II) acetylacetanoate, or copper(II) acetate, prior to introduction of the acylating or methylating agent.

Full text of DOI:10.1016/S0008-6215(01)00063-5

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Carbohydrate Research 332 (2001) 157–166
Regioselective C-3-O-acylation and O-methylation of
4,6-O-benzylidene-b-
D
-gluco- and galactopyranosides
displaying a range of anomeric substituents
Helen M.I. Osborn,* Victoria A. Brome, Laurence M. Harwood, William G. Suthers
Department of Chemistry, Uni6ersity of Reading, Whiteknights, Reading RG6 6AD, UK
Received 29 November 2000; accepted 20 February 2001
Abstract
The regioselective C-3-O-acylation and O-methylation of a range of 4,6-O-benzylidene-b-D-gluco- and galactopy-
ranosides has been studied. Regioselectivity is achieved by forming the copper chelate of the 2,3-diol using either
sodium hydride and copper(II) chloride, or copper(II) acetylacetanoate, or copper(II) acetate, prior to introduction
of the acylating or methylating agent. © 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Regioselective acylation; Copper chelate; Methylation; One-pot synthesis
copyranosides. For example, although it is
generally possible to access glucopyranoside
hermaphrodites with a free hydroxyl group at
C-3, access to the isomeric hermaphrodites
with a free hydroxyl group at C-2 is more
difficult. Thus, despite the ubiquitous nature
of glucopyranoside units within important
oligosaccharides, the selective activation of the
C-3 hydroxyl group remains a difficult chal-
lenge that still sanctions attention. This is in
contrast to results obtained with isomeric
monosaccharide counterparts, for which
largely successful strategies have now been
established.4
1. Introduction
As our understanding of the vital roles of
oligosaccharides as mediators of biological
events increases, so does our need for efficient
methods for their total syntheses.1 As a conse-
quence, a whole range of new oligosaccharide
assembly strategies have been developed
which allow efficient one-pot synthesis of
oligosaccharides.2 If access to individual iso-
mers of biologically important oligosacchar-
ides is to be possible, then orthogonally
protected hermaphrodites (molecules which
can act as donors or acceptors depending on
the reaction conditions) must be available.3
Such differentially protected hermaphrodites
are generally accessible for manno- and galac-
topyranosides,4 but are more elusive for glu-
Both chemical5 and enzymatic6 methods are
available for the regioselective protection of
the C-3 hydroxyl group of methyl 4,6-O-ben-
zylidene-b- -glycopyranosides, to afford C-2
D
acceptors in good yields. However, until re-
cently, the regioselective protection of the C-3
* Corresponding author. Tel.: +44-1189-875123; fax: +
44-1189-316331.
E-mail address: h.m.i.osborn@reading.ac.uk (H.M.I. Os-
born).
hydroxyl group of 4,6-O-benzylidene-b- -gly-
D
copyranosides displaying more versatile
anomeric substituents had been less widely
0008-6215/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(01)00063-5

158
H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
studied. Thus we have recently diverted our
attention to this area of research and have
developed two complimentary methods which
permit efficient, regioselective entry to the de-
sired targets.7,8 Regioselective protection of
the C-3 hydroxyl group is either achieved
using lipase enzymes7,9 or by performing cop-
per chelates of the benzylidene protected glu-
copyranoside diols.8 In the former case
Pseudomonas fluorescens lipase (PFL), Pseu-
domonas cepacia lipase (Lipase P) and Can-
dida cylindracea lipase (CCL) have been
utilised within an enzymatic regioselective
protection strategy. This has facilitated the
incorporation of acetyl, pivaloyl or formyl
esters in excellent yield and with excellent
regioselectivity at C-3 of some 4,6-O-benzyli-
2. Results and discussion
It has previously been reported5 that copper
chelates of methyl 4,6-O-benzylidene glycopy-
ranoside dianions can react regioselectively
with alkylating and acylating agents to afford
C-3 alkylated/acylated products in good
yields. It has been postulated that the carbo-
hydrate dianions are deactivated by the for-
mation of the copper(II) salt, and that as a
result a regioselective reaction occurs at the
C-3 hydroxyl group. Disubstitution is virtually
suppressed under these reaction conditions.
We have now demonstrated that dianions of
4,6-O-benzylidene glucopyranosides display-
ing a range of anomeric groups are also re-
gioselectively protected under these reaction
conditions. Hence access to orthogonally pro-
tected hermaphrodites has been achieved. This
method involves treating a solution of the
carbohydrate 2,3-diol in dry THF with two
equivalents of sodium hydride prior to the
addition of one equivalent of freshly prepared
and rigorously dried copper(II) chloride. A
range of acylating agents can then be added,
dene-b-
-glucopyranosides.7 In this paper we
D
wish to provide a full report of an alternative
copper mediated protection strategy,8 discuss
its applicability for the regioselective C-3 pro-
tection of 4,6-O-benzylidene-b- -galacto-
D
pyranosides and also outline the use of alter-
native copper species in the protection proto-
col.
Scheme 1.

H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
159
Scheme 2.
to afford a predominance of the C-3 protected
hermaphrodites as shown in Scheme 1.
For all of the acylated products, the signal
lation. In the majority of cases, the chemical
reactions are complete in much shorter reac-
tion times than for the enzyme-mediated
reactions.
1
for the H-3 proton in the H NMR spectrum
In our previous enzyme studies we had in-
vestigated the regioselective protection of the
is shifted downfield for the C-3 acylated re-
gioisomer, whilst the signal for the H-2 proton
is shifted downfield for the C-2 acylated re-
gioisomer. From these observations, and the
integration of the peaks representing the ben-
zylidene PhCH proton, it is possible to deter-
mine the ratio of regioisomers obtained in the
crude reaction mixtures. Whenever possible,
the isomeric products are separated by column
chromatography on silica gel to provide accu-
rate conversion yields. For alkylation experi-
ments, extensive NMR correlation experi-
ments are required to determine the isomeric
composition of the product mixtures. In our
hands, the alkylation reactions have proved
more capricious than the acylation reactions,
and at present, are restricted to regioselective
methylation reactions.
The copper- and enzyme-mediated protec-
tion methods provide complimentary methods
for synthesising orthogonally protected glu-
copyranosides with a free hydroxyl group at
C-2. Thus, whilst the yields and regioselectivi-
ties of the enzyme-mediated reactions often
exceed those obtained chemically, a wider
range of acyl groups can be introduced using
the chemical method. Moreover, unlike the
chemical method, the enzyme-mediated reac-
tions provide no scope for regioselective alky-
C-3 hydroxyl group of 4,6-O-benzylidene-b- -
D
galactopyranosides. Although excellent re-
gioselectivity could be achieved, the overall
yields of conversion rendered the reaction of
little synthetic use.7 For example, ethyl 4,6-O-
benzylidene - 1 - thio - b -
D
- galactopyranoside
could be converted to the C-3 acetylated
derivative with no trace of the C-2 acetylated
isomer, but in only 10% yield, using PFL and
vinyl acetate. Hence, we were keen to establish
whether the copper-mediated protection pro-
tocol could be extended to encompass 4,6-O-
benzylidene-b- -galactopyranosides.Thegalac-
D
topyranoside diols required for the copper-
mediated protection strategy were prepared
according to literature procedures.10 The diols
were then treated with two equivalents of
sodium hydride in anhydrous THF to form
the di-alkoxide, according to our standard
protocol. One equivalent of freshly prepared
anhydrous copper(II) chloride was then
added, following by 1.2 equivalents of the
acylating agent. After work-up, analysis of the
1H NMR spectrum of the crude reaction mix-
ture allowed an estimation of the regioselectiv-
ity of the reaction. Whenever possible, the
results were further verified by isolating the
individual regioisomers by column chro-

160
H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
plexation of Cu2+, with a cationic radius of
72 pm, to benzylidene protected glucopyran-
osides. Interestingly, Cu(OAc)2 has been
shown to complex strongly to polyols,14 pre-
sumably via the Cu(OAc)+ cation, without
the need for prior polyol anion formation.
This is in contrast to Cu(NO3)2 and CuCl2, for
which the enthalpy of interaction with non-de-
protonated glycosides is small.15 Hence the
next stage of our research programme in-
volved a study of the efficiency of Cu(OAc)2
or Cu(AcAc)2 to effect regioselective protec-
matography. The results obtained in this way
are highlighted in Scheme 2.
Hence regioselective protection in favour of
the required C-3 protected regioisomer is pos-
sible for a range of galactopyranosides. The
regioselectivity is enhanced significantly com-
pared with the isomeric glucopyranoside
derivatives. Moreover, although the isolated
yields are generally lower than the glucopyran-
oside analogues, the process is still syntheti-
cally useful. For example, this method is cur-
rently being utilised in our laboratory for the
large-scale synthesis of 2%%-monoglycosylated-
b-galactosyl donors for the synthesis of non-
natural glycosylceramides (Scheme 3).
Preformation of the benzylidene di-alkoxide
using sodium hydride is currently a prerequi-
site for efficient copper chelation in our syn-
thetic protocol, and this may possibly hamper
the extension of this work to incorporate the
regioselective protection of fully deprotected
monosaccharide derivatives, or disaccharide
derivatives. Hence, to further extend the util-
ity of this approach we were keen to deter-
mine whether alternative copper compounds
could be utilised in the reaction, to effect
chelation of the diol. In particular, we wished
to establish a procedure that would allow
efficient chelation of the diol without the need
for alkoxide generation, using sodium hy-
dride. Comprehensive reviews11 have high-
lighted the necessary criteria for effective
complexation of metals with polyols and have
demonstrated that both the conformation of
the polyol12 and the ionic radius of the
cation13 influence the strength of the complex-
ation. In general, the optimum ionic radius of
the cation for complexing is 100–110 pm as
illustrated by Na+, Ca2+ and La3+. Both
larger and smaller cations complex somewhat
less strongly and often necessitate prior polyol
anion formation to allow effective complex
formation. This is indeed the case for com-
tion of ethyl 4,6-O-benzylidene-1-thio-b-
D
-
glucopyranoside without prior anion
formation. Good regioselectivity could be ob-
tained using either complexing agent, and the
selectivity could be further optimised by ele-
vating the temperature to 55 °C and adding
triethylamine as a base. In contrast, at a low
temperature (−15 °C), no appreciable reac-
tion took place. It also proved possible to
perform the reaction in either THF or DME
as the solvent, and to use acetyl chloride or
acetic anhydride as the acylating agent. The
optimum results obtained in this way with
ethyl 4,6-O-benzylidene-1-thio-b- -glucopyran-
D
oside are highlighted in Scheme 4.
The full scope of this reaction and its appli-
cation to the synthesis of oligosaccharides of
biological importance is currently being inves-
tigated in our laboratory.
3. Experimental
General methods.—TLC adsorption chro-
matography was carried out using silica gel
(E. Merck): (a) 60 F254 0.2 mm aluminium-
backed plates; (b) column chromatography us-
ing 70–230 mesh silica gel (E. Merck).
Visualisation of the TLC plates was by 254
nm UV light and by spray-head development
using a 25:1 EtOH–H2SO4 reagent or an am-
monium molybdate reagent (15 g ammonium
molybdate in 150 mL of 10% H2SO4). Anhy-
drous THF and DME were prepared by distil-
lation from a sodium wire. When denoted in
the general method preparations, reactions
were carried out under an inert atmosphere of
Ar or N2. Solvents were evaporated at aspira-
tor vacuum at about 35 °C unless otherwise
stated. Optical rotation measurements were
Scheme 3.

H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
161
Scheme 4.
anhyd THF (100 mg in 10 mL THF) and
NaH in mineral oil (60%) (2 equiv) was added.
The formation of the disodium alcoholate was
complete in 1 h at rt to give a thick white
slurry. Anhydrous copper(II) (1 equiv) was
added to the alcoholate slurry, which went to
dissolution as a dark green solution. To the
green chelate solution was added an alkylating
reagent (5.0 equiv), the reaction was heated to
reflux temperature and left to stir under N2 for
24 h. The solution was cooled to rt, then
water (3 mL) and 50% aq NH3 solution (3
mL) were added to give a dark blue solution.
The organic layer was separated and the aq
layer extracted with EtOAc (5×5 mL). The
organic fractions were combined, dried
(MgSO4) and the excess solvent removed in
vacuo to yield a pale yellow oil which when
subjected to column chromatography (10:1
CH2Cl2–acetone, +1% Et3N) yielded the
protected benzylidene derivatives.
General method for copper acetylacetanoate
reactions.—The 4,6-O-benzylidene protected
glucose derivative (1 equiv) was dissolved in
anhyd THF (100 mg in 10 mL) and copper
acetoactanoate (1 equiv) added. The mixture
was stirred for 1 h at rt to give a blue solution.
To the blue chelate solution was added Ac2O
(1.2 equiv) and Et3N (1.2 equiv) and the reac-
tion was left to stir under N2 at rt for 5 h. To
the solution was added water (3 mL) and 50%
aq NH3 solution (3 mL) to give a dark blue
solution. The organic layer was separated and
carried out at the sodium D line (589.3 nm)
1
using a Perkin–Elmer 341 polarimeter. H
13
and C NMR spectra were recorded at 400 or
250 MHz and 100 or 60 MHz, respectively,
using Brucker AMX 400 and Brucker DPX
250 machines; mass spectroscopic analyses
were obtain in the chemical ionisation mode
using a Fisons VG Autospec.
General method for acylation reaction.—The
4,6-O-benzylidene derivative (1 equiv) was
dissolved in anhyd THF (100 mg in 10 mL
THF) and NaH in mineral oil (60%) (2 equiv)
was added. The formation of the disodium
alcoholate was complete in 1 h at rt to give a
thick white slurry. Anhydrous copper(II) chlor-
ide (1 equiv) was added to the alcoholate
slurry which went to dissolution as a dark
green solution. To the green chelate solution
was added an acylating reagent (1.2 equiv)
and the reaction left to stir under N2 at rt for
5 h. To the solution was added water (3 mL)
and 3% aq NH3 solution (3 mL) to give a dark
blue solution. The organic layer was separated
and the aq layer extracted with EtOAc (5×5
mL). The organic fractions were combined,
dried (MgSO4) and the excess solvent removed
in vacuo to yield a pale yellow oil which when
subjected to column chromatography (10:1
CH2Cl2–acetone, +1% Et3N) yielded the
protected benzylidene derivatives.
Alkylation reaction.—The 4,6-O-benzyli-
dene derivative (1 equiv) was dissolved in

162
H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
Ethyl
thio-i-
3-O-pi6aloyl-4,6-O-benzylidene-1-
-glucopyranoside (2b).—Brown vis-
the aq layer extracted with EtOAc (5×5 mL).
The organic fractions were combined, dried
(MgSO4) and the excess solvent removed in
vacuo to yield a pale yellow oil which when
subjected to column chromatography (10:1
CH2Cl2–acetone, +1% Et3N) yielded the
protected benzylidene glucose derivatives.
General method for copper acetate reac-
tions.—The 4,6-O-benzylidene protected glu-
cose (1 equiv) was dissolved in anhyd DME
(100 mg in 10 mL) and copper acetate (1
equiv) was added. The mixture was stirred for
1 h at rt to give a blue solution. To the blue
chelate solution was added acetyl chloride (1.2
equiv) and Et3N (1.2 equiv) and the reaction
left to stir under nitrogen at rt for 5 h. To the
solution was added water (3 mL) and 50% aq
NH3 solution (3 mL) to give a dark blue
solution. The organic layer was separated and
the aq layer extracted with EtOAc (5×5 mL).
The organic fractions were combined, dried
(MgSO4) and the excess solvent removed in
vacuo to yield a pale yellow oil which when
subjected to column chromatography (10:1
CH2Cl2–acetone, +1% Et3N) yielded the
protected benzylidene glucose derivatives.
D
cous oil (41%); [h]2D0 −66.9° (c 1.02 in
CHCl3), [lit7a [h]D20 −67.0 (c 1.02 in CHCl3)];
wmax 3492 br (OꢀH), 3067 w and 3037 w
(CꢀH), 2981 s (CꢀH), 1737 vs and 1715 vs
(CꢁO), 1481 s and 1397 s (CꢀH), 1282 s and
1079 s and 1019 s (CꢀO), 751 s and 698 s (Ar),
653 w (SꢀC) cm−1; lH (250 MHz, CDCl3) 1.16
(9 H, s, (CH3)3CO), 1.25 (3 H, t, J 7.5,
SCH2CH3), 2.68–2.71 (2 H, m, SCH2CH3),
2.73 (1 H, d, J 2.0, OH), 3.45–353 (2 H, m,
H-2, H-5), 3.61 (1 H, t, J 9.5, H-4), 3.70 (1 H,
t, J 10.5, H-6a), 4.29 (1 H, dd, J 5.0, 10.5,
H-6b), 4.44 (1 H, d, J 10.0, H-1), 5.12 (1 H, t,
J 9.0, H-3) 5.45 (1 H, s, PhꢀCH), 7.26–7.35 (5
H, m, ArH); lC (60 MHz, CDCl3); 15.25
(SCH2CH3),
25.00
(SCH2CH3),
27.08
(CH3)3C) 38.97 (CH3)3CCO) 68.56 (C-6),
70.64 (C-5), 72.32 (C-2), 74.87 (C-3), 78.43
(C-4), 87.23 (C-1), 101.07 (PhCH), 125.85,
128.18, 128.34, 128.93, 129.02, 136.92 (Ar{C-
1, C-2, C-3, C-4, C-5, C-6}), 178.78
(CH3)3CCO); m/z (CI) 415 (M+NH+4 , 24%),
397 (M+H, 80), 335 (72), 291 (100), 229 (64),
199 (48), 149 (61), 105 (63), 85 (48), 57 (53).
(Found [M+H] 397.1705. C20H29SO6 requires
397.1684.)
Ethyl
thio-i-
3-O-benzoyl-4,6-O-benzylidene-1-
-glucopyranoside (2a).—Colourless
D
Ethyl 3-O-acetyl-4,6-O-benzylidene-1-thio-
oil (48%); [h]2D0 −67.0° (c 1.02 in CHCl3),
[lit.16 [h]2D0 −122.9 (c 0.77 in CHCl3)]; wmax
3362 br (OꢀH), 2984 s (CꢀH), 2826 s (CꢀH),
1714 vs (CꢁO), 1446 s (CꢀH), 1374 vs (CꢀH),
1267 vs (CꢀO), 1082 s (CꢀO), 1024 s (CꢀO)
cm−1; lH (250 MHz, CDCl3) 1.25 (3 H, t, J
7.5, SCH2CH3), 2.68–2.71 (2 H, m,
SCH2CH3), 2.78 (1 H, d, J 2.0, OH), 3.34–
3.50 (2 H, m, H-2, H-5), 3.60–3.72 (2 H, m,
H-4, H-6a), 4.24 (1 H, dd, J 5.0, 10.5, H-6b),
4.72 (1 H, d, J 10.0, H-1), 5.39–5.46 (2 H, m,
H-3, PhꢀCH), 7.23–7.42 (5 H, m, ArH); lC
(60 MHz, CDCl3) 15.25 (SCH2CH3), 24.92
(SCH2CH3), 67.50 (C-6), 71.48 (C-5), 73.09
(C-2), 75.74 (C-3), 77.32 (C-4), 88.12 (C-1),
101.42 (PhCH), 126.11, 128.03, 128.21,
129.07, 130.45, 131.78 136.86 (Ar{C-1, C-2,
C-3, C-4, C-5, C-6}), 158.9 (PhO{C-1}),
170.01 (CH2CO2); m/z (CI) 417 (M+H,
25%), 355 (27), 311 (24), 249 (37), 219 (100),
43 (59). (Found [M+H] 417.1361. C22H25SO6
requires 417.1372.)
i-D
-glucopyranoside
(2c).—White
solid
(74%); m.p. 115–117 °C [lit.9 118–120 °C];
[h]2D0 −65.0° (c 1.0 in CHCl3), [lit.9 −67.3 (c
1.03 in CHCl3)]; wmax 3372 br (OꢀH), 2984 s
(CꢀH), 2826 s (CꢀH), 1714 vs (CꢁO), 1446 s
(CꢀH), 1374 vs (CꢀH), 1267 vs (CꢀO), 1082 s
(CꢀO), 1024 s (CꢀO) cm−1; lH (250 MHz,
CDCl3) 1.25 (3 H, t, J 7.5, SCH2CH3), 2.06 (3
H, s, CH3COO), 2.67–2.70 (2 H, m,
SCH2CH3), 3.45–3.52 (2 H, m, H-2, H-5),
3.58 (1 H, app. t, J 9.0, 9.5, H-4), 3.69 (1 H,
app. t, J 10.0, 10.5, H-6), 4.27 (1 H, dd, J 5.0,
10.5, H-6), 4.43 (1 H, d, J 10.0, H-1), 5.16 (1
H, app. t, J 9.0, 9.5, H-3) 5.42 (1 H, s,
PhꢀCH), 7.27–7.38 (5 H, m, ArH); lC (60
MHz; CDCl3) 15.25 (SCH2CH3), 21.01
(CH3COO), 24.92 (SCH2CH3), 68.50 (C-6),
70.48 (C-5), 72.09 (C-2), 74.74 (C-3), 78.32
(C-4), 87.12 (C-1), 101.42 (PhCH), 126.11,
128.21, 129.07, 136.86 (Ar{C-1, C-2, C-3, C-4,
C-5, C-6}), 171.01 (CH3CO2); m/z (CI) 355
(M+H, 24%), 293 (23), 249 (39), 187 (32),

H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
163
CDCl3) 1.22 (9 H, s, (CH3)3CCO), 3.39–3.52
(2 H, m, H-2, H-5), 3.68–3.73 (2 H, m, H-5,
H-6a), 4.28–4.33 (1 H, m, H-6b), 4.84 (1 H, d,
J 10.2, H-1), 5.09 (1 H, t, J 9.1, H-3), 5.44 (1
H, s, PhꢀCH), 7.24–7.59 (10 H, m, ArH); lC
(60 MHz, CDCl3) 27.29 ((CH3)3CCOO), 39.31
((CH3)3CCOO), 67.50 (C-6), 73.09 (C-2),
75.74 (C-3), 77.32 (C-4), 78.48 (C-5), 87.12
(C-1), 101.42 (PhCH), 126.11, 127.11, 127.76,
128.03, 128.21, 129.07, 130.45, 131.78 136.86
(SeAr, Ar{C-1, C-2, C-3, C-4, C-5, C-6}),
158.9 (PhO{C-1}, 170.01 (CCO2); m/z (CI)
493 (M+H, 24%), 386 (32), 335 (67), 292
(31), 275 (59), 148 (41), 127 (53), 105 (100), 78
(85), 43 (71). (Found [M+H] 493.1121.
C24H29O6Se requires 493.1129.)
105 (100), 43 (59). (Found [M+H] 355.1221.
C17H23O6 requires 355.1215.)
Ethyl 3-O-methyl-4,6-O-benzylidene-1-thio-
i- -glucopyranoside (2d).—Colourless oil
D
(6%); m.p. 117–120 °C, [lit.9 134 °C]; [h]D20
−32.1° (c 1.03 in CHCl3), [lit.9 −60 (c 1.46 in
CHCl3)]; wmax 3372 br (OꢀH), 2984 s (CꢀH),
2854 s (CꢀH), 1446 s (CꢀH), 1374 vs (CꢀH);
lH (250 MHz, CDCl3) 1.25 (3 H, t, J 7.5,
SCH2CH3), 2.67–2.70 (2 H, m, SCH2CH3),
3.48 (3 H, s, CH3O), 3.45–3.52 (2 H, m, H-2,
H-5), 3.58 (1 H, app. t, J 9.0, 9.5, H-4), 3.69 (1
H, app. t, J 10.0, 10.5, H-6a), 4.27 (1 H, dd, J
5.0, 10.5, H-6b), 4.43 (1 H, d, J 10.0, H-1),
5.16 (1 H, app. t, J 9.0, 9.5, H-3) 5.42 (1 H, s,
PhꢀCH), 7.27–7.38 (5 H, m, ArH); lC (60
MHz, CDCl3) 15.25 (SCH2CH3), 16.01
(CH3O), 24.92 (SCH2CH3), 68.50 (C-6), 70.48
(C-5), 72.09 (C-2), 74.74 (C-3), 78.32 (C-4),
87.12 (C-1), 101.42 (PhCH), 126.11, 128.21,
129.07, 136.86 (Ar{C-1, C-2, C-3, C-4, C-5,
C-6}); m/z (CI) 327 (M+H, 23%), 265 (24),
221 (37), 159 (33), 105 (100), 43 (43). (Found
[M+H] 327.1259. C16H23SO5 requires
327.1266.)
Phenyl 3-O-acetyl-4,6-O-benzylidene-1-se-
leno-i- -glucopyranoside (6c).—White solid
D
(81%); m.p. 156–159 °C; [h]2D7−18.7° (c 0.15
in CHCl3); wmax 3465 br (OꢀH), 2954 w, 2885
s (CꢀH), 1740 s (CꢁO), 1600 s (CꢁC), 1591 w
(CꢁC), 1495 s (CꢁC) cm−1; lH (250 MHz,
CDCl3) 2.11 (3 H, s, CH3COO) 3.51–3.58 (3
H, m, H-2, H-4, H-5), 3.76 (1 H, app. t, J
10.5, 9.5, H-6a), 4.40 (1 H, app. t, J 4.5, 10.5,
H-6b), 4.87 (1 H, d, J 10.0, H-1), 5.20 (1 H, t,
J 9.0, H-3), 5.48 (1 H, s, PhꢀCH), 7.31–7.66
(10 H, m, ArH); lC (60 MHz, CDCl3) 20.98
(CH3COO), 68.51 (C-6), 71.89, 72.24, 74.60,
78.20 (C-5, C-2, C-3, C-4), 85.43 (C-1), 101.50
(PhCH), 126.12, 128.24, 128.73, 129.13,
129.26, 131.49, 135.41, 136.80 (Ar ArSe{C-1,
C-2, C-3, C-4, C-5, C-6}), 171.07 (CH3CO2);
m/z (CI) 451 (M+H, 18%), 390 (5), 344 (36),
293 (71), 250 (36), 233 (55), 187 (30), 148 (44),
127 (51), 105 (100), 78 (82), 43 (72). (Found
[M+H] 451.0649. C21H23O6Se requires
451.0659.)
Phenyl 3-O-benzoyl-4,6-O-benzylidene-1-se-
leno-i- -glucopyranoside (6a).—Clear gum
D
(65%); [h]2D0 −73.5° (c 1.02 in CHCl3); wmax
3424 br (OꢀH), 2930 w, 2880 s (CꢀH), 1740 vs
(CꢁO), 1600 s (CꢁC), 1590 w (CꢁC) cm−1; lH
(250 MHz, CDCl3) 3.44–3.79 (4 H, m, H-2,
H-4, H-5, H-6a), 4.39 (1 H, dd, J 4.5, 9.0,
H-6b), 4.85 (1 H, d, J 9.0, H-1), 5.39 (1 H, t,
J 9.0, H-3), 5.43 (1 H, s, PhꢀCH), 7.19–7.60
(15 H, m, ArH);); lC (60 MHz; CDCl3) 67.50
(C-6), 73.09 (C-2), 75.74 (C-3), 77.32 (C-4),
78.48 (C-5), 87.12 (C-1), 101.42 (PhCH),
117.46, 118.67, 119.36, 120.68, 126.11, 126.89,
127.56, 128.43, 128.45, 129.12, 130.56, 131.28
136.79 (SeAr, Ar{C-1, C-2, C-3, C-4, C-5,
C-6}), 158.5 (PhO{C-1}, 170.89 (CH3CO2).
m/z (CI) 513 (M+H, 23%), 406 (29), 355
(69), 312 (32), 148 (35), 127 (49), 105 (100), 71
(87), 43 (75). (Found [M+H] 513.0809.
C26H25O6Se requires 513.0816.)
Phenyl 3-O-methyl-4,6-O-benzylidene-1-se-
leno-i-
D
-glucopyranoside
(6d).—Colourless
oil (75%); [h]2D0 −24.0° (c 1.01 in CHCl3),
[lit.17 [h]2D0 −38° (c 1.0 in CHCl3)]; wmax 3334
br (OꢀH), 2980 s (CꢀH), 2854 s (CꢀH), 1445 s
(CꢀH), 1372 vs (CꢀH) cm−1; lH (250 MHz,
CDCl3) 2.68 (1 H, d, J 2.0 Hz, OH), 3.40 (3
H, s, C-3OCH3), 3.47–3.49 (2 H, m, H-2,
H-5), 3.57–3.59 (1 H, m, H-4), 3.62 (3 H, s,
C-1), 3.66 (1 H, t, J 9.8 Hz, H-6), 3.72–3.78 (1
H, m, H-3), 4.19–4.23 (1 H, dd, J 5.0, 9.8 Hz,
H-6), 4.94 (1 H, d, J 2.5 Hz, H-1), 5.47 (1 H,
s, PhꢀCH), 7.28–7.44 (10 H, m, ArH); lC (60
Phenyl
seleno-i-
3-O-pi6aloyl-4,6-O-benzylidene-1-
-glucopyranoside (6b).—Clear gum
D
(39%); [h]2D0 −64.0° (c 1.02 in CHCl3); wmax
3424 br (OꢀH), 3057 w, 3042 w, 2930 w, 2880
s (CꢀH), 1745 vs (CꢁO), 1600 s (CꢁC), 1590 w
(CꢁC), 1497 s (CꢁC) cm−1; lH (250 MHz,

164
H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
(11), 162 (7), 149 (28), 129 (9), 105 (37), 94
(20), 91 (12), 77 (8), 66 (8), 65 (8), 57 (27), 43
(8), 39 (6). (Found [M+H] 429.1564.
C23H28O6 requires 429.1913.)
MHz; CDCl3) 67.50 (C-5), 69.75 (C-6), 80.10
(C-2), 80.85 (C-3), 85.35 (C-2), 94.26 (C-1),
100.15 (PhCH), 124.45, 124.65, 127.32,
127.43, 127.55, 127.85, 128.25 (Ar, PhO{C-2,
C-3, C-4, C-5, C-6}), 134.78 (Ar{C-1}), 168.15
(PhO{C-1); m/z (CI) 423 (M+H, 21%), 362
(7), 317 (29), 265 (65), 222 (39), 205 (57), 190
(44), 159 (34), 127 (46), 105 (100), 78 (74), 43
(67). (Found [M+H] 423.0701. C20H23O5Se
requires 423.0711.)
Phenyl 3-O-acetyl-4,6-O-benzylidene-i- -
D
glucopyranoside (10c).—White solid (62%);
m.p. 205–209 °C; [h]2D0 −66.5° (c 1.02 in
CHCl3); wmax 3424 br (OꢀH), 3057 w, 3042 w,
2930 w, 2880 s (CꢀH), 1745 vs (CꢁO), 1600 s
(CꢁC), 1590 w (CꢁC), 1497 s (CꢁC) cm−1; lH
(250 MHz, CDCl3) 2.16 (3 H, s, CH3COO),
3.55–3.91 (4 H, m, H-2, H-5, H-4, H-6a),
4.36–4.43 (1 H, m, H-6b), 5.11 (1 H, d, J 7.5,
H-1), 5.31 (1 H, t, J 9.5, H-3), 5.52 (1 H, s,
PhꢀCH), 6.99–7.51 (10 H, m, Ar); lC (60
MHz, CDCl3) 25.29 (CH3COO), 66.30 (C-6),
71.75 (C-5), 73.25 (C-2), 75.82 (C-3), 81.93
(C-4), 95.92 (C-1), 101.35 (PhCH), 117.63,
123.82, 127.28, 128.55, 129.25, 130.88, 137.28
(ArC), 161.68 (CH3COO); m/z (CI) 387 (M+
H, 21%), 293 (MꢀOPh, 97), 233 (14), 187 (30),
149 (38), 127 (25), 105 (23), 94 (28), 92 (68), 91
(81), 77 (19), 58 (21), 43 (100), 39 (14). (Found
Phenyl 3-O-benzoyl-4,6-O-benzylidene-i- -
D
glucopyranoside (10a).—White solid (61%).
m.p. 201–204 °C; [lit.18 207 °C]; [h]D27 −67.6°
(c 1.02 in CHCl3), [lit.18 [h]D20 −72° (c 1 in
CHCl3)]; wmax 3362 br (OꢀH), 2984 s (CꢀH),
2826 s (CꢀH), 1714 vs (CꢁO), 1446 s (CꢀH),
1374 vs (CꢀH), 1267 vs (CꢀO), 1082 s (CꢀO),
1024 s (CꢀO) cm−1; lH (250 MHz, CDCl3)
3.45–3.57 (3 H, m, H-2, H-4, H-6a), 3.89–4.01
(1 H, m, H-5), 4.34–4.56 (1 H, app. dd, J 4.5,
9.5, H-6b), 5.16 (1 H, d, J 7.5, H-1), 5.38 (1 H,
t, J 9.5, H-3), 5.51 (1 H, s, PhꢀCH), 6.78–7.32
(15 H, m, Ar); lC (60 MHz, CDCl3) 64.40
(C-5), 69.06 (C-6), 72.28 (C-2), 74.18 (C-3),
82.19 (C-4), 96.69 (C-1), 102.36 (PhCH),
117.83, 123.59, 127.29, 128.75, 129.59, 130.47
(Ar, PhO{C-2, C-3, C-4, C-5, C-6}), 138.92
(Ar{C-1}), 157.90 (PhO{C-1); m/z (CI) 449
(M+H, 35%), 355 (100), 347 (15), 249 (21),
149 (22), 129 (9), 105 (35), 94 (19), 57 (29), 39
(5).
[M+H]
387.1444.
C21H22O7
requires
387.1443.)
Phenyl 3-O-methyl-4,6-O-benzylidene-i-
glucopyranoside
D
-
(10d).—Colourless solid
(64%); m.p. 203–206 °C [lit.19 211 °C]; [h]D20
−43.2° (c 1.04 in CHCl3), [lit.19 [h]D20 −46.2°
(c 1 in CHCl3)]; wmax 3369 br (OꢀH), 2982 s
(CꢀH), 2854 s (CꢀH), 1445 s (CꢀH), 1372 vs
(CꢀH) cm−1; lH (250 MHz, CDCl3) 2.73 (1 H,
d, J 2.0, OH), 3.38 (2 H, s, C-3ꢀOCH3),
3.47–3.49 (2 H, m, H-2, H-5), 3.55–3.57 (1 H,
m, H-4), 3.58 (3 H, s, C-1ꢀOꢀCH3), 3.66 (1 H,
t, J 9.8, H-6), 3.72–3.78 (1 H, m, H-3), 4.19–
4.23 (1 H, dd, J 5.0, 9.8, H-6), 4.72 (1 H, d, J
2.5, H-1), 5.47 (1 H, s, PhꢀCH), 7.28–7.44 (10
H, m, ArH); lC (60 MHz, CDCl3) 67.50 (C-5),
69.75 (C-6), 80.20 (C-2), 80.95 (C-3), 85.45
(C-2), 96.56 (C-1), 100.15 (PhCH), 124.85,
124.95, 127.25, 127.35, 127.4, 127.95, 128.80
(Ar, PhO{C-2, C-3, C-4, C-5, C-6}), 136.20
(Ar{C-1}), 164.75 (PhO{C-1}); m/z (CI) 359
(M+H, 24%), 265 (92), 205 (17), 159 (29),
149 (34), 127 (29), 105 (21), 94 (23), 92 (71), 91
(78), 43 (100). (Found [M+H] 359.1487.
C20H23O6 requires 359.1495.)
Phenyl 3-O-pi6aloyl-4,6-O-benzylidene-i- -
D
glucopyranoside (10b).—Brown viscous oil
(59%); [h]2D7 −64.1° (c 1.01 in CHCl3); wmax
3362 br (OꢀH), 2984 s (CꢀH), 2826 s (CꢀH),
1714 vs (CꢁO), 1446 s (CꢀH), 1374 vs (CꢀH),
1267 vs (CꢀO), 1082 s (CꢀO), 1024 s (CꢀO)
cm−1; lH (250 MHz, CDCl3) 1.14 (9 H, s,
(CH3)3CCOO), 3.58–3.69 (3 H, m, H-2, H-4,
H-6a), 3.94–4.00 (1 H, m, H-5), 4.15–4.19 (1
H, app. dd, J 4.5, 9.5, H-6b), 5.07 (1 H, d, J
7.5, H-1), 5.35 (1 H, t, J 9.5, H-3), 5.50 (1 H,
s, PhꢀCH), 6.95–7.42 (10 H, m, Ar); lC (60
MHz, C3D6O) 27.29 ((CH3)3CCOO), 39.31
((CH3)3CCOO), 64.40 (C-5), 69.06 (C-6),
72.28 (C-2), 74.18 (C-3), 82.19 (C-2), 96.69
(C-1), 102.36 (PhCH), 117.83, 123.59, 127.29,
128.75, 129.59, 130.47 (Ar, PhO{C-2, C-3,
C-4, C-5, C-6}), 138.92 (Ar{C-1}), 157.90
(PhO{C-1); m/z (CI) 429 (M+H, 37%), 335
(MꢀOPh, 100), 327 (17), 317 (7), 229 (21), 211
Ethyl
thio-i-
3-O-benzoyl-4,6-O-benzylidene-1-
D
-galactopyranoside (14a).—Colour-
less solid (50%); m.p. 127–128.5 °C, [lit.16

H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
165
129.5–130.5 °C]; [h]2D0 +52.1° (c 1.0, CHCl3),
[lit.16 +57.9°, c 1.0, CHCl3)]; wmax (CHCl3)
MHz, CDCl3) 15.3 (SCH2CH3), 21.5
(COOCH3), 23.4 (SCH2CH3), 66.8 (C-2), 69.6
(C-6), 70.3 (C-5), 72.9 (C-4), 75.3 (C-3), 82.9
(C-1), 126.7, 128.6, 129.5, 137.8 (ArC), 170.9
(CꢁO); m/z (CI) 355 (M+H, 23%), 293 (100),
249 (31), 187 (20), 149 (15), 105 (12).
3480 (OꢀH), 1720 (CꢁO), 1450 (CꢀH) cm−1
;
lH (250 MHz, CDCl3) 1.38 (3 H, t, J 7.5,
SCH2CH3) 2.78–2.91 (2 H, m, SCH2CH3),
3.66 (1 H, d, J 1.4, H-5), 4.07 (1 H, dd, J 1.4,
J% 12.5, H-6), 4.26 (1 H, app. t, J 9.6, H-2),
4.39 (1 H, dd, J 1.4, J% 12.5, H-6), 4.52 (1 H,
d, J 9.6, H-1), 4.55 (1 H, dd, J 1.4, J% 3.5,
H-4), 5.19 (1 H, dd, J 3.5, J% 9.6, H-3), 5.53 (1
H, s, PhCH), 7.36–7.59 (8 H, m, PhꢀH),
8.09–8.13 (2 H, m, PhꢀH); lC (60 MHz,
CDCl3) 15.7 (SCH2CH3), 23.8 (SCH2CH3),
67.1 (C-2), 69.6 (C-6), 70.4 (C-5), 74.4 (C-4),
75.7 (C-3), 86.4 (C-1), 101.3 (PhCH), 126.6,
128.5, 128.8, 129.3, 130.1, 130.4, 133.7, 138.2,
(ArꢀC), 166.8 (CꢁO); m/z (CI) 417 (M+H,
8%), 355 (63), 311 (30), 149 (27), 105 (100).
(Found [M+H] 417.1389. C22H25O6S requires
417.1389.)
Phenyl 3-O-benzoyl-4,6-O-benzylidene-1-se-
leno-i- -galactopyranoside (18a).—Colour-
D
less solid (34%); m.p. 60.5–62.0 °C; [h]D20
+3.8° (c 1.0, CHCl3); wmax (CHCl3) 3480
(OꢀH), 3060 (PhꢀH), 2860 (CꢀH), 1720 (CꢁO)
cm−1; lH (250 MHz, CDCl3) 3.55 (1 H, d, J
1.0, H-5), 3.93 (1 H, dd, J 1.7, 12.5, H-6), 4.08
(1 H, dt, J 2.3, J% 9.7, H-2), 4.30 (1 H, dd, J
1.0, J% 12.4, H-6), 4.40 (1 H, dd, J 1.0, J% 3.4,
H-4), 4.80 (1 H, d, J 9.7, H-1), 5.08 (1 H, dd,
J 3.4, J% 9.7, H-3), 5.39 (1 H, s, PhCH),
7.10–7.32 (11 H, m, PhꢀH), 7.66–7.70 (2 H,
m, PhꢀH), 7.91–7.96 (2 H, m, PhꢀH); lC (60
MHz, CDCl3) 67.0 (C-2), 69.5 (C-6), 71.3
(C-5), 74.4 (C-4), 75.3 (C-3), 84.9 (C-1), 101.1
(PhCH), 126.6, 126.8, 127.0, 128.5, 128.6,
128.8, 129.4, 129.6, 130.0, 130.1, 130.6, 133.3,
133.7, 135.6, 138.2 (ArꢀC), 166.8 (CꢁO); m/z
(CI) (M+H, 4%), 407 (45), 355 (100), 248
(19), 148 (38), 105 (96). (Found [M+H]
513.0826. C26H25O6Se requires 513.0816.)
Ethyl
thio-i-
3-O-pi6aloyl-4,6-O-benzylidene-1-
-galactopyranoside (14b).—Colour-
D
less solid (40%), m.p. 106.5–108 °C; [h]2D0 48.5°
(c 1.0, CHCl3); wmax (CHCl3) 3480 (OꢀH), 2970
(CꢀH), 1730 (CꢁO) cm−1; lH (250 MHz,
CDCl3) 1.17 (9 H, s, C(CH3)3) 1.24 (3 H, t, J
7.4, SCH2CH3), 2.63–2.76 (SCH2CH3), 3.48 (1
H, d, J 1.6, H-5), 3.92 (1 H, dd, J 1.6, J% 12.5,
H-6), 4.00 (1 H, d, J 9.6, H-2), 4.25 (1 H, dd,
J 1.6, J% 12.5, H-6), 4.32–4.36 (2 H, m, H-1,
H-4), 4.77 (1 H. dd, J 3.6, J% 9.6, H-3), 5.41 (1
H, s, PhCH), 7.25–7.30 (3 H, m, PhꢀH),
7.37–7.41 (2 H, m, PhꢀH); lC (60 MHz,
CDCl3) 15.7 (SCH2CH3) 23.9 (SCH2CH3),
27.5 (C(CH3)), 39.4 (C(CH3)), 67.0 (C-2), 69.6
(C-6), 70.3 (C-5), 74.1 (C-4), 75.1 (C-3), 86.3
(C-1), 101.0 (PhCH), 126.4, 126.8, 128.5,
128.7, 129.2, 138.2 (ArꢀC), 178.8 (CꢁO); m/z
(CI) 397 (M+H, 17%), 335 (100), 291 (54),
247 (65), 149 (70), 57 (66). (Found [M+H]
397.1691. C20H29O6S requires 397.1702.)
Phenyl
seleno-i-
3-O-pi6aolyl-4,6-O-benzylidene-1-
-galactopyranoside (18b).—Colour-
D
less solid (35%); m.p. 146–148 °C; [h]D20
+12.7 (c 1.0, CHCl3); wmax (CHCl3) 3480
(OꢀH), 2970 (CꢀH), 1730 (CꢁO) cm−1; lH
(400 MHz, CDCl3) 1.18 (9 H, s, (C(CH3)3)),
2.47 (1 H, br s, OH), 3.58 (1 H, app. d, J 1.2,
H-5), 4.00 (1 H, dd, J 1.7, 12.5, H-6), 4.05 (1
H, app. t, J 9.7, H-2), 4.37 (1 H, dd, J 1.7,
12.5, H-6), 4.39 (1 H, dd, J 0.9, 3.5, H-4), 4.83
(1 H, d, J 9.7, H-1), 4.84 (1 H, dd, J 3.5, 9.7,
H-3), 5.48 (1 H, s, PhCH), 7.13–7.42 (8 H, m,
ArH), 7.72–7.74 (2 H, m, ArH); lC (60 MH,
CDCl3) 27.4 (C(CH3)) 39.4 (C(CH3)), 67.0
(C-2), 69.6, 71.2, 74.0, 74.6 (C-6), 85.2 (C-1),
100.8 (PhCH), 126.5, 126.9, 128.5, 129.3,
129.5, 135.2, 138.3 (ArꢀC), 178.8 (CꢁO); m/z
(CI) 493 (M+H, 4%), 387 (32), 335 (100), 229
(20), 149 (70), 85 (17), 57 (29). (Found [M+
H] 493.1125. C24H29O6Se requires 493.1129.)
Phenyl 3-O-acetyl-4,6-O-benzylidene-1-se-
Ethyl 3-O-acetyl-4,6-O-benzylidene-1-thio-
i- -galactopyranoside (14c).—lH (250 MHz,
D
CDCl3) 1.23 (3 H, t, J 7.5, SCH2CH3), 2.07 (3
H, s, COOCH3), 2.55–2.79 (2 H, m,
SCH2CH3), 3.45–3.47 (1 H, m, H-5), 3.94 (1
H, dd, J 1.8, 12.5, H-6), 3.96 (1 H, dd, J 1.8,
12.5, H-6), 3.99 (1 H, app. t, J 9.6, H-2), 4.33
(1 H, dd, J 1.0, 3.5, H-4), 4.34 (1 H, d, J 9.6,
H-1), 4.81 (1 H, dd, J 3.5, 9.6, H-3), 5.42 (1 H,
s, PhCH), 7.28–7.43 (5 H, m, PhꢀH); lC (60
leno-i- -galactopyranoside (18c).—Colour-
D
less solid (45%); m.p. 66–67 °C; [h]2D0+9.2° (c
1.0, CHCl3); wmax (CHCl3) 3460 (OꢀH), 2880

166
H.M.I. Osborn et al. / Carbohydrate Research 332 (2001) 157–166
(CꢀH), 1735 (CꢁO) cm−1; lH (250 MHz,
CDCl3) 2.01 (3 H, s, OCH3), 3.52 (1 H, J 1.7,
H-5), 3.91 (1 H, t, J 9.7, H-2), 3.94 (1 H, dd,
J 1.7, J% 12.5, H-6), 4.27–4.33 (2 H, m, H-4,
H-6), 4.75 (1 H, d, J 9.7, H-1), 4.82 (1 H, dd,
J 3.4, J% 9.7, H-3), 5.39 (1 H, s, PhCH),
7.09–7.29 (8 H, m, PhꢀH), 7.66–7.70 (2 H, m,
PhꢀH); lC (60 MHz, CDCl3) 66.7 (C-5), 69.6
(C-6), 71.1 (C-2), 74.1 (C-4), 74.8 (C-3), 84.7
(C-1), 101.3 (PhCH), 126.0, 126.8, 128.6,
128.7, 129.5, 129.6, 135.8, 138.1 (ArꢀC), 171.4
(CꢁO); m/z (CI) 451 (M+H, 7%), 344 (34),
293 (100), 187 (28), 149 (25). (Found [M+H]
451.0660. C21H23O6Se requires 451.0660.)
(b) Haines, A. H. Ad6. Carbohydr. Chem. Biochem. 1976,
33, 11.
[5] (a) Eby, R.; Schuerch, C. Carbohydr. Res. 1982, 100, C41;
(b) Eby, R.; Webster, K. T.; Schuerch, C. Carbohydr.
Res. 1984, 129, 111;
(c) Avela, E.; Holmbom, B. Acta Acad. Abstract Ser. B
1971, 14, 31;
(d) Avela, E.; Melander, B.; Holmbom, B. Acta. Acad.
Abstracts Ser. B 1971, 15, 31.
[6] (a) Chinn, M. J.; Iacazio, G.; Spackman, D. G.; Turner,
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We are grateful to the EPSRC (Fast track
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Research Endowment Trust Fund (stu-
dentship to VAB) and the Royal Society
(Equipment grant) for financial support of
this work.
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