Stereoselective synthesis of C-glycosides from carboxylic acids: The tandem Tebbe-Claisen approach

Article abstract of DOI:10.1039/b306675b

A variety of β- or α-C-glycosides may be readily accessed in an entirely stereoselective fashion from esters derived from the reaction of carboxylic acids and 3-hydroxy glycals, by way of a tandem reaction sequence of Tebbe methylenation and Claisen rearrangement. Though of wide scope, for example allowing the synthesis of 1-6 linked C-disaccharides, the methodology does not currently allow the synthesis of C-glycosyl α-amino acids.

Full text of DOI:10.1039/b306675b

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Stereoselective synthesis of C-glycosides from carboxylic acids:
the tandem Tebbe–Claisen approach†
H. Yasmin Godage,a David J. Chambers,a Graham R. Evansb and Antony J. Fairbanks*a
a Dyson Perrins Laboratory, Oxford University, South Parks Road, Oxford, UK OX1 3QY
b Celltech R & D, Granta Park, Great Abington, Cambridge, UK CB1 6GS
Received 11th June 2003, Accepted 11th August 2003
First published as an Advance Article on the web 28th August 2003
A variety of β- or α-C-glycosides may be readily accessed in an entirely stereoselective fashion from esters derived
from the reaction of carboxylic acids and 3-hydroxy glycals, by way of a tandem reaction sequence of Tebbe
methylenation and Claisen rearrangement. Though of wide scope, for example allowing the synthesis of 1–6 linked
C-disaccharides, the methodology does not currently allow the synthesis of C-glycosyl α-amino acids.
Introduction
Over recent years C-glycosides1 have become popular synthetic
targets,2,3 particularly as potential glycomimetics,4 which may
themselves have possible therapeutic applications in accordance
with the well-established importance of carbohydrates in a
plethora of biological process.5 However despite considerable
synthetic interest in this area, there is still currently some debate
as to the potential general ability of C-glycosides to act as non-
hydrolysable mimics of their natural O-linked counterparts.6,7
In order to address this question directly it would seem
appropriate to test the ability of a variety of C-glycosides to act
generally as glycomimetics by high-throughput biological
screening. Such a screening program would require synthetic
access to a wide variety of C-glycosides in a parallel synthetic
manner. However despite the large amount of previous work in
this field, no one single synthetic approach to C-glycosides
seems immediately amenable to parallel synthesis, suggesting
that the development of new synthetic methodology is
Fig. 1
desirable.
When we considered how best to develop a new parallel
C–C bond forming reaction: gluco derived glycals producing
solely the β-C-glycosides, and allo derived glycals giving rise
solely to the α-C-glycosides respectively.
synthetic approach to C-glycosides two important aspects
became apparent. These were firstly stereochemical control of
the C-glycosylation reaction, and secondly the potential gener-
ality of the overall reaction sequence. In order to avoid the
tedious and often difficult separation of mixtures of anomeric
products, it seemed that one could profitably use a thermal
sigmatropic rearrangement for the construction of the new
carbon–carbon bond at the anomeric centre with complete
control of stereochemistry.8 However rather than choosing to
adopt the classic Claisen–Ireland approach, which can result in
the formation of a mixture of diastereomers at the carbon atom
attached to the anomeric centre due to lack of stereocontrol
of enolate formation, it was envisaged that a tandem process
involving Tebbe methylenation9 and thermal sigmatropic
rearrangement should allow stereoselective access to a wide
range of C-glycosides. Thus esterification of a suitably pro-
tected glycal 1 with a chosen carboxylic acid would lead to the
formation of a glycal ester 2. Tebbe methylenation would then
produce an enol ether 3, which could in turn undergo a stereo-
specific sigmatropic rearrangement to yield the desired C-glyco-
side 4 (Fig. 1). The advantages of the approach were considered
to be the potential generality of the reaction sequence, since in
theory almost any carboxylic acid could be used for the esterifi-
cation step (vide infra), and the stereospecificity of the anomeric
Herein we report full details of this tandem Tebbe–Claisen
approach10,11 which allows synthetic access to a wide range of
either α- or β-C-glycosides in an entirely stereoselective fashion.
Results and discussion
Synthesis of ꢀ-C-Glycosides
The tandem Tebbe–Claisen approach to C-glycosides requires
access to selectively protected glycals in which the 3-hydroxy
group is free for esterification, with a wide range of carboxylic
acids to allow parallel synthesis. As an initial model system, the
4,6-O-silyl protected glucose-derived glycal 512 was synthesised
from glucose β-pentaacetate in 4 steps following literature
procedures (72% overall yield). Esterification of 5 with either
benzoic, octanoic, or palmitic acids was achieved by treatment
of the glycal with the corresponding carboxylic acid and
dicyclohexylcarbodiimide (DCC), with catalytic N,N-dimethyl-
aminopyridine (DMAP), yielding esters 6a–c in excellent yields.
The two-step sequence of Tebbe methylenation and Claisen
rearrangement was then undertaken. Tebbe reaction proceeded
smoothly in a THF–pyridine mixture at Ϫ40 ЊC, to yield the
corresponding enol ethers 7a–c, which although moderately
stable, were in general used for subsequent rearrangement after
minimal purification on a short column of basic alumina.
Thermal rearrangement of this set of enol ethers 7a–c occurred
upon heating to 180 ЊC, in either benzonitrile or tributyl-
amine,13 producing the corresponding β-C-glycosides 8a–c14 in
† This is one of a number of contributions from the current members
of the Dyson Perrins Laboratory to mark the end of almost 90 years of
organic chemistry research in that building, as all its current academic
staff move across South Parks Road to a new purpose-built laboratory.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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good to excellent yield (84–89%, Scheme 1, reaction yields
quoted over two steps of methylenation and rearrangement).
The structure of β-C-glycoside 8a was confirmed by X-ray
crystallography (Fig. 2)
glycal esters again yielded the desired intermediate enol ethers
11a and 11b. Thermal rearrangement proceeded rapidly upon
heating to 180 ЊC in tributylamine to yield the β-C-glycosides
12a and 12b (71% and 80% yields over two steps, Scheme 2).
The structure of C-glycoside 12b was also confirmed by X-ray
crystallography (Fig. 3).
Fig.
3
X-Ray crystal structure of β-C-glycoside 12b showing
crystallographic numbering scheme [thermal ellipsoid plot (ORTEP-34)
at 40% probability].
Synthesis of ꢁ-C-Glycosides
Scheme 1 Reagents and conditions: (i) RCO2H, DCC, DMAP, CH2Cl2,
RT; (ii) Tebbe reagent, THF, pyridine, Ϫ40 ЊC; (iii) 180 ЊC, PhCN or
Bu3N.
With the successful synthesis of a variety of β-C-glycosides in
hand, attention then turned to the synthesis of the corre-
sponding α-C-glycosides, which necessarily entailed the use of
glycal esters epimeric at the 3-position as starting materials. The
4,6-O-silyl protected allo-alcohol 14 was therefore synthesised
from allal 1318 by regioselective silylation with di-tert-butylsilyl
ditriflate in DMF at low temperature (77% yield, Scheme 3).
In addition as further substrates for investigation, the 4,6-O-
benzylidene protected allal 15 and the corresponding C-2
methyl substituted derivative 16 were also synthesised following
literature procedures.19 The silyl protected glycal 14 was con-
verted into the palmitic ester 17 by treatment with palmitic
acid, DCC, and catalytic DMAP. Treatment of benzylidene
protected glycal 15 with benzoyl chloride and catalytic DMAP
in pyridine furnished the benzoate ester 18a, whilst acetylation
of 15 with acetic anhydride in pyridine, yielded the acetate 18b,
and finally treatment of 15 with palmitic acid, DCC, and
catalytic DMAP, gave the palmitic ester 18c. Similarly methyl
substituted glycal 16 was converted into its benzoate ester 19 by
treatment with benzoyl chloride. Methylenation of this selec-
tion of esters 17, 18a–c, 19 proceeded smoothly under standard
reaction conditions (treatment with ∼2 equivalents of Tebbe
reagent at Ϫ40 ЊC, in a 4 : 1 mixture of THF and pyridine),
to yield the corresponding enol ethers 20–22 (Scheme 3) in
excellent yields. The structure of enol ether 21b was confirmed
by X-ray crystallography (Fig. 4).
Fig.
2
X-Ray crystal structure of β-C-glycoside 8a showing
crystallographic numbering scheme [thermal ellipsoid plot (ORTEP-34)
at 40% probability].
For further exemplification the corresponding 4,6-O-benzyl-
idene protected glycal 9 was also synthesised as a starting
material, by a synthetic route recently developed in our labor-
atory15 which was significantly more efficient than the low yield-
ing16 or protracted previously reported procedures.17 The corre-
sponding benzoate 10a and acetate 10b were accessed from 9 by
the use of benzoyl chloride or acetic anhydride respectively
(94% and 96% yields, Scheme 2). Tebbe methylenation of these
Scheme 2 Reagents and conditions: (i) BzCl, DMAP, pyridine, 0 ЊC; (ii)
Ac2O, pyridine, RT; (iii) Tebbe reagent, THF, pyridine, Ϫ40 ЊC; (iv) 180
ЊC, Bu3N.
Fig. 4 X-Ray crystal structure of enol ether 21b showing crystallo-
graphic numbering scheme [thermal ellipsoid plot (ORTEP-34) at 40%
probability].
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Scheme 3 Reagents and conditions: (i) tBu2Si(OTf )2, DMF, Ϫ40 ЊC to RT, 77%; (ii) RCO2H, DCC, DMAP, CH2Cl2, RT; (iii) Tebbe, THF, pyridine,
Ϫ40 ЊC; (iv) PhCOCl, DMAP, pyridine, 0 ЊC; (v) Ac2O, pyridine, RT.
With this selection of enol ethers in hand attention turned
to the subsequent Claisen rearrangement. Thermal rearrange-
ment of enol ether 21a was attempted following conditions that
had successfully yielded the corresponding β-C-glycosides, but
it was found that heating 21a to 180 ЊC in benzonitrile as
solvent produced a mixture of both α- and β-C–glycoside
products, 23a and 12a (Scheme 4), albeit in a favourable ratio of
α : β, 5 : 1. In addition small amounts of the open chain diene
24 were also observed, indicating the probable mechanism by
which the α-C-glycosides are inter-converted to their thermo-
dynamically more favoured β-counterparts.20,21 Although in the
β-series the formation of minor amounts of epimeric product
that was occasionally observed during thermal rearrangement
in benzonitrile could be suppressed by changing the solvent to
tributylamine, in the α-series this proved not to be the case;
once again anomeric mixtures of products were formed. In
an attempt to avoid this epimerisation process a selection of
Lewis acid catalysed reactions were investigated as an altern-
ative to thermal rearrangement. However, reactions undertaken
with a variety of different Lewis acid catalysts, including
NaBF4, AlCl3, BF3ؒOEt2, Yb(OTf )3, and TiCl4, under a variety
of reaction conditions, perhaps not unsurprisingly22 again
resulted in the formation of mixtures of epimeric products,
together with variable amounts of open chain diene 24.
Although in some cases the ratio of products was in favour of
the desired α-anomer (e.g. α : β ratio of 16 : 1, for BF3ؒOEt2),
the yields for these reactions were at best modest (∼60%).
Moreover since the original synthetic objective was the devel-
opment of methodology that allowed complete control of
anomeric stereochemistry, the search for alternative reaction
conditions continued.
in deuterated benzene as the solvent. When the thermal
rearrangement of 21a was performed in d6-benzene in a sealed
tube the reaction proceeded smoothly and no formation of the
undesired β-anomer was observed. This unexpected observation
pointed the way to the use of benzene as the solvent for the
rearrangement reaction. Indeed a series of thermal rearrange-
ments in benzene pleasingly produced pure α-C-glycosides.
However mindful of the toxicity of benzene, a selection of
alternative solvents were screened at a variety of temperatures.
Thermal rearrangement in xylene at 195 ЊC proved to be
optimum, and gratifyingly enol ethers 21a, 21b and 22 all
rearranged smoothly in excellent yield and most importantly
entirely stereoselectively to yield only the α-C-glycoside prod-
ucts 23a, 23b and 25 respectively. The anomeric stereochemistry
of α-C-glycoside 23a was confirmed by X-ray crystallography
as previously detailed,10 whilst the anomeric configurations of
the other α-C-glycosides were confirmed by NOE difference
experiments.23
During rearrangement of the two palmitic esters 21c and 20
in addition to the desired α-C-glycosides 23c and 27 two side
products were occasionally observed. These side products were
identified as the α-C-glycosides 26 and 28, and are presumably
formed via partial isomerisation of the glycal enol ethers 21c
and 20 to the thermodynamically preferred more substituted
tautomers before rearrangement. Frustratingly the relative
amounts of these products formed appeared to be quite vari-
able depending on the length of reaction and solvent. For
example in one instance the use of xylene as solvent for the
rearrangement of 20 completely suppressed the formation of
28, but a similar experiment with d6-benzene as solvent
resulted in the formation of 28 in an almost equal amount to
that of the desired product 27. However the formation of 26
from 21c was observed even in xylene as solvent. Unfortunately
complete suppression of the formation of these side-products
has not yet proved possible. Indeed it has subsequently been
discovered that sealed tube rearrangement of palmitic ester 6b
in xylene at 195 ЊC also leads to the formation of this type
of isomeric product, whereas none was previously observed
during thermal rearrangement at 180 ЊC in either benzonitrile,
or tributylamine.
In the face of the persistent anomerisation problem it was
thought prudent to monitor the rate of formation of the
undesired β-anomer relative to the Claisen rearrangement itself.
The most expedient way to do this appeared to be via in situ
reaction monitoring by NMR, importantly in a solvent where
the characteristic proton resonances for the starting material
and both the α- and β-C-glycoside products were well separ-
ated. Therefore a series of sealed tube reactions, which rather
fortuitously revealed some interesting results, were undertaken
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Scheme 4 Reagents and conditions: (i) Bu3N, 180 ЊC; (ii) PhCN, 180 ЊC; (iii) various Lewis acids at low temperature; (iv) xylene, sealed tube, 195 ЊC;
(v) xylene, sealed tube, 195 ЊC, ratio 23c : 26, 1.3 : 1, yield 85%; (vi) d6-benzene, 195 ЊC, sealed tube, ratio 23c : 26, 1 : 1, yield 84%; (vii) xylene, sealed
tube, 195 ЊC, 27 only, yield 85%; (viii) d6-benzene, 195 ЊC, sealed tube, ratio 27 : 28, 1.4 : 1, yield 94%.
Synthesis of C-disaccharides
One the most appealing features of this C-glycosylation strat-
egy is the potential range of carboxylic acids which may be used
for the esterification reaction. In particular the use of carb-
oxylic acids derived from carbohydrates as coupling partners
would allow the linking of one saccharide unit to the anomeric
position of another via a methylene bridge. In order to test out
the potential of this type of approach for the conjugation of
carbohydrates, the synthesis of a β-C-linked disaccharide was
undertaken. Thus the known galacturonic acid 29,24 (obtained
in high yield by ruthenium mediated25 oxidation of diacetone
galactose), was coupled with glycal 5, to yield the ester 30.
Tebbe methylenation of 30 was found to be much more sluggish
than the previous examples, but by the use of an extended reac-
tion time (24 h) and an excess of Tebbe reagent, a satisfactory
yield of the desired enol ether 31 was obtained (72% yield
based on recovered starting material; the reaction could not be
driven to completion). Claisen rearrangement of enol ether 31
occurred rapidly at 180 ЊC in benzonitrile to yield the desired
β-C-disaccharide 32 in a satisfactory 56% yield (Scheme 5).
This reaction demonstrates the feasibility of the approach
for the synthesis of (1–6) linked C-disaccharides. Moreover,
since it should in principle be relatively straightforward to
achieve access to the 6-hydroxy of compounds such as 32
one should be able to iterate such a process, by a sequence of
oxidation, esterification and Tebbe–Claisen, in order to access
C-trisaccharides and higher homologues.
Scheme 5 Reagents and conditions: (i) 5, DCC, DMAP, CH2Cl2, 91%;
(ii) Tebbe, THF, pyridine, Ϫ40 ЊC to RT, 72%; (iii) 180 ЊC, PhCN, 56%.
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Scheme 6 Reagents and conditions: (i) RCO2H, DCC, DMAP, CH2Cl2, RT; (ii) Tebbe, THF, pyridine, Ϫ40 ЊC; (iii) Bu3N, 180 ЊC.
cases reaction of ester 38 or 39 did occur, but the isolated
product was simply the alcohol 5. This inability of the Tebbe
reagent to methylenate esters of α-amino acids27 therefore
appears to currently preclude the synthesis of C-glycosyl amino
acids using this methodology.
Attempted synthesis of C-glycosyl amino acids
There has recently been much interest in the synthesis of
C-glycosyl amino acids, either as potential building blocks for
the synthesis of C-glycopeptides of for other purposes.26 In
principle the tandem Tebbe–Claisen approach could provide
facile access to a wide range of such materials directly from
suitably protected forms of the parent amino acids. Moreover
since any α-amino acid, or indeed the β- or γ-acid of aspartic or
glutamic acids, could be used for esterification, a wide range of
such materials could be accessed in a parallel manner through a
short reaction sequence. In order to firstly test compatibility
of a typical amino protecting group with the Tebbe–Claisen
reaction sequence Boc protected 4-aminobutyric acid was
investigated as a substrate. Thus both silyl protected glycal 5
and benzylidene protected glycal 15 were esterified by treatment
with 4-aminobutyric acid and DCC in the presence of DMAP,
to yield the two required esters 33 and 36 respectively (Scheme
6). Both esters underwent reaction with the Tebbe reagent to
provide the two enol ethers 34 and 37 respectively, this trans-
formation being notable in so far as that no side reaction of the
Boc protecting group was observed. Thermal rearrangement of
enol ether 34 was complete in 1 hour after heating at 180 ЊC in
tributylamine and yielded the desired β-C-glycoside 35 in a
respectable yield over two steps. However benzylidene protected
enol ether 37 only reacted extremely slowly under similar condi-
tions, and no appreciable amount of product was observed—
the starting material being recovered in this case.
Summary
It is clear that the combined use of Tebbe methylenation and
thermal Claisen rearrangement provides a powerful and poten-
tially rather general route to stereodefined α- or β-C-glycosides.
However, although access to the β-compounds is facile, in order
to obtain pure α-products careful control of reaction condi-
tions is required in order to avoid competing formation of the
thermodynamically more stable β-C-glycoside products. This is
currently best achieved by performing the thermal reactions in
either xylene or benzene in a sealed tube. By the use of carb-
ohydrate derived carboxylic acids as coupling partners this
methodology may be applied to the synthesis of (1–6) linked
C-disaccharides. However the failure of the Tebbe reagent to
methylenate glycal esters derived from α-amino acids currently
precludes the use of this methodology for the synthesis of
C-glycosyl amino acids. Further investigations into the use of
the tandem Tebbe–Claisen approach for the synthesis of a wide
variety of C-glycosides, and C-oligosaccharides, and into the
use of alternative methylenation conditions to allow the syn-
thesis of C-glycosyl amino acids, are currently in progress, and
results will be reported in due course.
Encouraged by these initial studies, which in particular
indicated the compatibility of Boc protection with the Tebbe
reaction, two further esters were synthesised as substrates
for methylenation and rearrangement in an attempt to access
C-glycosyl amino acids. Thus glycal 5 was esterified with both
N-Boc protected alanine, and α-azido acetic acid to yield esters
38 and 39 respectively. However unfortunately neither of these
esters could be methylenated using the Tebbe reagent—in both
Experimental
General methods
Melting points were recorded on a Kofler hot block and are
uncorrected. Proton nuclear magnetic resonance (δH) spectra
were recorded on a Bruker DRX 500 (500 MHz), a Bruker
DPX 400 (400 MHz) or on a Varian Gemini 200 (200 MHz)
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spectrometer. Carbon nuclear magnetic resonance (δC) spectra
were recorded on a Bruker DPX 400 (100.6 MHz) or on a
Bruker AC 200 (50.3 MHz) spectrometer. Spectra were assigned
using COSY, HMQC, APT or DEPT and/or HMBC and/or
edited HSQC, and/or NOESY experiments. All chemical shifts
are quoted on the δ-scale in parts per million (ppm). All NMR
experiments were performed at a probe temperature of 30 ЊC.
Infrared spectra were recorded on a Perkin-Elmer 150 Fourier
Transform spectrophotometer. Low resolution mass spectra
were recorded a VG Micromass Platform using either atmos-
pheric pressure chemical ionisation (APCI), or negative ion
electrospray (ESϪ) or positive ion electrospray (ESϩ), or on a
Micromass GCT TOF spectrometer, using solid probe temper-
ature programmed field ionisation (FI). High resolution mass
spectra (electrospray) were performed on a Waters 2790-
Micromass LCT electrospray ionisation mass spectrometer,
or by the EPSRC Mass Spectrometry Service Centre, Depart-
ment of Chemistry, University of Wales, Swansea on a
MAT900 XLT electrospray ionisation mass spectrometer.
Optical rotations were measured on a Perkin-Elmer 241 polar-
imeter with a path length of 1 dm. Concentrations are given in g
per 100 ml. Microanalyses were performed by the microanalyti-
cal services of the Inorganic Chemistry Laboratory, Oxford.
Thin layer chromatography (TLC) was carried out on Merck
Kieselgel 0.22–0.25 mm thickness glass-backed sheets, pre-
coated with 60F254 silica. Plates were developed using 5% w/v
ammonium molybdate in 2 M sulfuric acid. Flash column
chromatography was carried out using Sorbsil C60 40/60 silica.
Solvents and reagents were dried and purified before use accord-
ing to standard procedures under an atmosphere of argon;
methanol was distilled from sodium hydride, dichloromethane
and toluene were distilled from calcium hydride, pyridine was
distilled from calcium hydride and stored over potassium
hydroxide, and diethyl ether and tetrahydrofuran were distilled
from a solution of sodium benzophenone ketyl immediately
before use.
was then concentrated in vacuo and the residue purified by flash
column chromatography (petrol : ethyl acetate, 12 : 1)
General method B : Tebbe methylenation
Tebbe reagent (2–4 equiv.) was added drop-wise to a stirred
solution of glycal ester (1 equiv.) in tetrahydrofuran (2 ml) and
pyridine (0.5 ml) at Ϫ40 ЊC, under an atmosphere of argon.
After 1.5 h, TLC (petrol : diethyl ether, 8 : 1 ϩ 2% triethyl-
amine) indicated complete consumption of starting material
and the formation of a major product. The reaction mixture
was quenched by the drop-wise addition of sodium hydroxide
solution (0.1 M, ∼0.2 ml) until the effervescence ceased. The
reaction mixture was diluted with petrol (10 ml) and stirred for
a further 10 min. The mixture was then filtered through a short
column of basic alumina and eluted with petrol : diethyl ether,
6 : 1 with 2% triethylamine to obtain the glycal enol ether. This
unstable compound was typically used in the next step with out
further purification.
General method C: thermal rearrangement in benzonitrile or
tributylamine
The crude enol ether (∼50 mg) was heated in benzonitrile (1 ml)
or tributylamine (1 ml) at 180 ЊC for 25 min, after which time
TLC (petrol : diethyl ether, 8 : 1 ϩ 2% triethylamine) indicated
the complete consumption of starting material and the form-
ation of a major product. The reaction was concentrated in
vacuo and the residue purified by flash column chromatography
(petrol : diethyl ether, 6 : 1) to obtain the C-glycoside.
General method D: sealed tube thermal rearrangement
The enol ether (∼50 mg) was dissolved in anhydrous xylene
(1 ml) under an atmosphere of argon and heated in a sealed
pressure tube at 195 ЊC. After 2 h 15 min, TLC (petrol : ethyl
acetate, 3 : 1 ϩ2% triethylamine) indicated the complete con-
sumption of starting material and the formation of a major
product. The reaction mixture was then concentrated in vacuo
and the residue purified by flash column chromatography
(petrol : ethyl acetate, 3 : 1) to obtain the C-glycoside.
General crystallography
Single crystals were mounted on a glass fibre using perfluoro-
polyether oil and cooled rapidly to 150 K in a stream of cold N2
using an Oxford Cryosystems CRYOSTREAM unit. Diffrac-
tion data were measured using an Enraf-Nonius KappaCCD
diffractometer (graphite-monochromated MoKα radiation, λ =
0.71073 Å). Intensity data were processed using the DENZO-
SMN package. Examination of the systematic absences of
the intensity data indicated the space group. The structure was
solved using the direct-methods program SIR92, which located
all non-hydrogen atoms. Subsequent full-matrix least-squares
refinement was carried out using the CRYSTALS program
suite. Coordinates and anisotropic thermal parameters of all
non-hydrogen atoms were refined. Hydrogen atoms were posi-
tioned geometrically after each cycle of refinement. A 3-term
Chebychev polynomial weighting scheme was applied. Refine-
ment converged satisfactorily.‡
1,5-Anhydro-3-O-benzoyl-2-deoxy-4,6-O-di(tert-butyl)silane-
diyl-D-arabino-hex-1-enitol 6a
General method A: Alcohol 5 (1.5 g, 5.25 mmol), benzoic acid
(843 mg, 7.37 mmol), dicyclohexylcarbodiimide (2.17 g, 10.5
mmol) and 4-dimethylaminopyridine (129 mg, 1.06 mmol),
gave ester 6a (1.76 g, 86%) as a colourless oil; [α]2D3 Ϫ164.6 (c,
1 in CHCl3); νmax (thin film): 1723 (s, C᎐O), 1648 (m, C᎐C)
᎐
᎐
cmϪ1; δH (400 MHz, CDCl3) 0.99, 1.07 (18H, 2 × s, 2 ×
C(CH3)3), 4.00–4.07 (2H, m, H-5 and H-6), 4.23–4.25 (1H, m,
H-6Ј), 4.37 (1H, dd, J3,4 7.6 Hz, J4,5 9.9 Hz, H-4), 4.88 (1H, dd,
J1,2 6.1 Hz, J2,3 2.0 Hz, H-2), 5.60 (1H, double apparent triplet
(dat), J 1.8 and 7.6 Hz, H-3), 6.37 (1H, dd, J1,3 1.5 Hz, H-1),
7.45–7.49 (2H, m, Ar–Hmeta), 7.57–7.59 (1H, m, Ar–Hpara), 8.07–
8.09 (2H, m, Ar–Hortho); δC (100.6 MHz, CDCl3) 19.8, 22.7
(2 × s, 2 × C(CH3)3), 26.8, 27.4 (2 × q, 2 × C(CH3)3), 65.8
(t, C-6), 72.9, 73.0 (2 × d, C-3 and C-5), 73.6 (d, C-4), 100.6 (d,
General method A: DCC mediated esterification
Anhydrous dichloromethane was added to a mixture of
the glycal (1 equiv.), the carboxylic acid (1.5 equiv.), dicyclo-
hexylcarbodiimide (2 equiv.) and 4-dimethylaminopyridine
(0.2 equiv.) under an atmosphere of argon. The resulting reac-
tion mixture was stirred at room temperature for 15 h, after
which time TLC (petrol : ethyl acetate) indicated the complete
consumption of starting material and the formation of a major
product. The mixture was filtered through a pad of Celite and
the residue washed with dichloromethane. The resulting filtrate
C-2), 128.4, 129.6 (2 × d, Cmeta
Ar), 130.3 (s, Cipso Ar),
and ortho
133.0 (d, Cpara Ar), 145.1 (d, C-1), 166.5 (s, CO2Ph); m/z (FIϩ)
390 (Mϩ, 45%). (HRMS calcd. for C21H30O5Si (M) 390.1863.
Found 390.1868) (Found: C, 64.53; H, 8.05. C21H30O5Si
requires C, 64.58; H, 7.74%).
1,5-Anhydro-2-deoxy-3-O-octanoyl-4,6-O-di(tert-butyl)silane-
diyl-D-arabino-hex-1-enitol 6b
General method A: Octanoic acid (0.55 ml, 3.49 mmol), alcohol
5 (500 mg, 1.75 mmol), dicyclohexylcarbodiimide (720 mg, 3.49
mmol) and 4-dimethylaminopyridine (43 mg, 0.35 mmol), gave
ester 6b (658 mg, 91%) as a colourless oil; [α]2D3 Ϫ59.1 (c, 1 in
‡ CCDC reference numbers 212630–212632. See http://www.rsc.org/
suppdata/ob/b3/b306675b/ for crystallographic data in .cif or other
electronic format.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3777

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CHCl3); νmax (thin film): 1741 (s, C᎐O), 1647 (m, C᎐C) cmϪ1
;
pyridine (0.5 ml), gave enol ether 7b (56 mg) as a pale yellow oil.
This unstable compound was used in the next step with out
᎐
᎐
δH (400 MHz, CDCl3) 0.88 (3H, t, J 6.9 Hz, O2C(CH2)6CH3),
0.99, 1.06 (18H, 2 × s, 2 × C(CH3)3), 1.27–1.33 (8H, m, O2CCH2-
CH2(CH2)4CH3), 1.62–1.69 (2H, m, O2CCH2CH2(CH2)4CH3),
2.31–2.40 (2H, m, O2CCH2(CH2)5CH3), 3.92 (1H, ddd, J4,5 10.2
Hz, J5,6 10.3 Hz, J5,6Ј 4.6 Hz, H-5), 3.99 (1H, at, J 10.1 Hz, H-6),
4.16 (1H, dd, J3,4 7.6 Hz, H-4), 4.19 (1H, dd, J6,6Ј 9.7 Hz, H-6Ј),
4.71 (1H, dd, J1,2 6.0 Hz, J2,3 2.0 Hz H-2), 5.41 (1H, dat,
J 1.8 Hz and 7.6 Hz, H-3), 6.32 (1H, dd, J1,3 1.6 Hz, H-1);
δC (100.6 MHz, CDCl3) 13.9 (q, O2C(CH2)6CH3), 19.6, 22.5
(2 × s, 2 × C(CH3)3), 26.7, 27.2 (2 × q, 2 × C(CH3)3), 22.5, 25.0,
28.8, 28.8, 31.5 (5 × t, O2CCH2(CH2)5CH3), 34.5 (t, O2CCH2-
(CH2)5CH3), 65.7 (t, C-6), 71.8 (d, C-3), 72.9 (d, C-5), 73.7 (d,
C-4), 100.8 (d, C-2), 145.0 (d, C-1), 173.9 (s, O2C(CH2)6CH3);
m/z (FIϩ) 412 (Mϩ, 68%). (HRMS calcd. for C22H40O5Si
(Mϩ) 412.2645. Found 412.2645) (Found: C, 64.06; H, 9.72.
C22H40O5Si requires C, 64.04; H, 9.77%).
further purification; νmax (thin film): 1652, 1645 (2 × C᎐C);
᎐
δH (500 MHz, C6D6) 1.02 (3H, t, J 6.8 Hz, (CH2)6CH3), 1.14,
1.18 (18H, 2 × s, 2 × C(CH3)3), 1.38–1.47 (8H, m, (CH2)2(CH2)4-
CH3), 1.70–1.77 (2H, m, CH2CH2(CH2)4CH3), 2.25–2.33 (2H,
m, CH2(CH2)5CH3), 3.95 (1H, ddd, J4,5 10.4 Hz, J5,6 10.4 Hz,
J5,6Ј 5.0 Hz, H-5), 4.06 (1H, at, J 10.4 Hz, H-6), 4.15 (1H, s,
C᎐CHHЈ), 4.17 (1H, s, C᎐CHHЈ), 4.27 (1H, dd, J 10.3 Hz,
᎐
᎐
6,6Ј
H-6Ј), 4.45 (1H, dd, J3,4 7.3 Hz, H-4), 4.79 (1H, br d, J 7.3 Hz,
H-3), 5.03 (1H, dd, J1,2 6.1 Hz, J2,3 0.9 Hz, H-2), 6.22 (1H, d,
H-1); δC (100.6 MHz, C6D6) 14.5 (q, (CH2)6CH3)), 20.1, 23.0
(2 × s, 2 × C(CH3)3), 27.3, 27.8 (2 × q, 2 × C(CH3)3), 23.3, 27.8,
29.5, 29.8, 32.4 (5 × t, CH2(CH2)5CH3), 36.0 (t, CH2(CH2)5-
CH3), 66.5 (t, C-6), 73.3 (d, C-5), 75.1 (d, C-4), 75.3 (d,
C-3), 82.7 (t, C᎐CH ), 100.7 (d, C-2), 144.5 (d, C-1), 162.7 (s,
᎐
2
C᎐CH ); m/z (CIϩ) 411 (MHϩ, 35%).
᎐
2
1,5-Anhydro-2-deoxy-4,6-O-di-(tert-butyl)-3-O-(1-pentadecyl-
ethenyl)silanediyl-D-arabino-hex-1-enitol 7c
1,5-Anhydro-2-deoxy-3-O-hexadecanoyl-4,6-O-di(tert-butyl)-
silanediyl-D-arabino-hex-1-enitol 6c
General method B: Tebbe reagent (0.76 ml, 0.38 mmol), glycal
ester 6c (50 mg, 0.10 mmol), tetrahydrofuran (2 ml) and
pyridine (0.5 ml), gave enol ether 7c (58 mg) as a pale yellow oil.
This unstable compound was used in the next step with out
General method A: Alcohol 2 (250 mg, 0.87 mmol), palmitic
acid (448 mg, 1.75 mmol), dicyclohexylcarbodiimide (360 mg,
1.75 mmol) and 4-dimethylaminopyridine (21 mg, 0.17 mmol),
gave ester 6c (435 mg, 95%) as a colourless oil; [α]2D3 Ϫ49.3
(c, 1 in CHCl3); νmax (thin film) 1742 (C᎐O), 1647 (C᎐C) cmϪ1
;
further purification; νmax (thin film): 1651, 1647 (s, 2 × C᎐C);
᎐
᎐
᎐
δH (400 MHz, C6D6) 0.91 (3H, t, J 6.8 Hz, (CH2)14CH3), 1.02
(9H, s, C(CH3)3), 1.06 (9H, s, C(CH3)3), 1.22–1.37 (24H, m,
(CH2)2(CH2)12CH3), 1.59–1.66 (2H, m, CH2CH2(CH2)12-
CH3), 2.11–2.25 (2H, m, CH2(CH2)13CH3), 3.82 (1H, ddd,
J4,5 10.3 Hz, J5,6 10.3 Hz, J5,6Ј 4.9 Hz, H-5), 3.93 (1H, at, J 10.3
δH (400 MHz, CDCl3) 0.88 (3H, t, J 6.8 Hz, O2C(CH2)14CH3),
0.99 and 1.06 (18H, 2 × s, 2 × C(CH3)3), 1.21–1.30 (24H, m,
O2CCH2CH2(CH2)12CH3), 1.61–1.69 (2H, m, O2CCH2CH2-
(CH2)12CH3), 2.30–2.38 (2H, m, O2CCH2(CH2)13CH3), 3.93
(1H, ddd, J4,5 9.8 Hz, J5,6 10.2 Hz, J5,6Ј 4.6 Hz, H-5), 3.99 (1H,
at, J 10.0 Hz, H-6), 4.16 (1H, dd, J3,4 7.6 Hz, H-4), 4.19 (1H, dd,
J6,6Ј 9.7 Hz, H-6Ј), 4.71 (1H, dd, J1,2 6.0 Hz, J2,3 2.0 Hz, H-2),
5.41 (1H, dat, J 1.8 Hz, J 7.6 Hz, H-3), 6.31 (1H, dd, J1,3 1.5 Hz,
H-1); δC (100.6 MHz, CDCl3) 14.1 (q, O2C(CH2)14CH3), 19.8,
22.5 (2 × s, 2 × C(CH3)3), 26.8, 27.3 (2 × q, 2 × C(CH3)3), 22.7,
24.9, 25.1, 29.0, 29.1, 29.3, 29.3, 29.4, 29.6, 29.6, 29.7, 29.7, 31.9
(13 × t, O2CCH2(CH2)13CH3), 34.6 (t, O2CCH2(CH2)13CH3),
65.7 (t, C-6), 71.8 (d, C-3), 72.9 (d, C-5), 73.6 (d, C-4), 100.7 (d,
C-2), 144.8 (d, C-1), 173.7 (s, O2C(CH2)14CH3); m/z (FIϩ) 524
(Mϩ, 34%). (HRMS calcd. for C30H56O5Si (Mϩ) 524.3897.
Found 524.3892) (Found: C, 68.58; H, 10.71. C30H56O5Si
requires C, 68.65; H, 10.75%).
Hz, H-6), 4.03 (1H, d, Jgem 1.6 Hz, C᎐CHHЈ), 4.04 (1H, d,
᎐
C᎐CHHЈ), 4.14 (1H, dd, J 10.2 Hz, H-6Ј), 4.31 (1H, dd,
᎐
6,6Ј
J3,4 7.3 Hz, H-4), 4.65 (1H, br d, 7.3 Hz, H-3), 4.90 (1H,
dd, J1,2 6.1 Hz, J2,3 1.7 Hz, H-2), 6.06 (1H, dd, J1,3 1.3 Hz,
H-1); δC (100.6 MHz, C6D6) 14.6 (q, (CH2)14CH3), 20.2, 23.1
(2 × s, 2 × C(CH3)3), 27.4, 27.9 (2 × q, 2 × C(CH3)3), 23.4, 27.9,
29.6, 30.1, 30.3, 30.4, 30.5, 30.7, 30.7, 30.7, 32.6 (11 × t,
CH2(CH2)13CH3), 36.1 (t, CH2(CH2)13CH3), 66.6 (t, C-6), 73.4
(d, C-5), 75.2 (d, C-4), 75.3 (d, C-3), 82.7 (t, C᎐CH ), 100.8 (d,
᎐
2
C-2), 144.6 (d, C-1), 162.7 (s, C᎐CH ); m/z (APCIϩ) 524 (MHϩ,
᎐
2
15%).
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-di(tert-butyl)silanediyl-2Ј,3Ј-dideoxy-
ꢀ-D-erythro-hex-2Ј-enopyranosyl)acetophenone 8a
1,5-Anhydro-2-deoxy-3-O-(1-phenylethenyl)-4,6-O-di(tert-butyl)-
silanediyl-D-arabino-hex-1-enitol 7a
General method C: Crude enol ether 7a (52 mg), in benzonitrile
(1 ml), gave the β-C-glycoside 8a (42 mg, 84% over two steps)
as a white crystalline solid; mp 130–131 ЊC (petrol); [α]2D2 ϩ46.6
General method B: Tebbe reagent (1.02 ml, 0.51 mmol), glycal
ester 6a (50 mg, 0.13 mmol), tetrahydrofuran (2 ml) and pyrid-
ine (0.5 ml), gave enol ether 7a (52 mg) as a colourless oil. This
unstable compound was carried through to the next step with-
(c, 1 in CHCl3); νmax (KBr disc): 1682 (s, C᎐O) cmϪ1; δH (400
᎐
MHz, C6D6) 1.20, 1.21 (18H, 2 × s, 2 × C(CH3)3), 2.68 (1H,
dd, J1Ј,C(O)CHHЈ 6.5 Hz, Jgem 16.7 Hz, C(O)CHHЈ), 3.17 (1H, dd,
J1Ј,C(O)CHHЈ 6.8 Hz, C(O)CHHЈ), 3.74 (1H, ddd, J4Ј,5Ј 8.5 Hz,
J5Ј,6Ј 10.4 Hz, J5Ј,6Љ 5.1 Hz, H-5Ј), 4.02 (1H, at, J 10.2 Hz, H-6Ј),
4.30 (1H, dd, J6Ј,6Љ 10.0 Hz, H-6Љ), 4.64–4.68 (1H, m, H-4Ј),
4.99–5.01 (1H, m, H-1Ј), 5.68 (1H, dat, J2Ј,3Ј 10.4 Hz, J 1.9 Hz,
H-2Ј), 6.05 (1H, br d, J 10.4 Hz, H-3Ј), 7.06–7.12 (2H, m,
Ar–H), 7.17–7.21 (1H, m, Ar–H), 7.87–7.90 (2H, m, Ar–H);
δC (100.6 MHz, C6D6) 20.5, 23.1 (2 × s, 2 × C(CH3)3), 27.6,
27.8 (2 × q, 2 × C(CH3)3), 44.2 (t, CH2COPh), 67.7 (t,
C-6Ј), 71.0 (d, C-4Ј), 72.6 (d, C-1Ј), 75.4 (d, C-5Ј), 128.5, 128.8
(4 × d, Cortho and meta Ar), 129.9 (d, C-2Ј), 130.5 (d, C-3Ј), 133.1 (d,
out further purification; νmax (thin film): 1645 (m, C᎐C), 1615
᎐
(w, C᎐C) cmϪ1; δH (400 MHz, C6D6) 1.11, 1.16 (18H, 2 × s, 2 ×
᎐
C(CH3)3), 3.97 (1H, ddd, J4,5 10.4 Hz, J5,6 10.4 Hz, J5,6Ј 5.0 Hz,
H-5), 4.08 (1H, at, J 10.4 Hz, H-6), 4.28 (1H, dd, J6,6Ј 10.3 Hz,
H-6Ј), 4.52 (1H, d, Jgem 2.5 Hz, C᎐CHHЈ), 4.55 (1H, dd, J3,4 7.3
᎐
Hz, H-4), 4.85 (1H, d, C᎐CHHЈ), 4.91 (1H, dat, J 1.5 Hz, 7.2
᎐
Hz, H-3), 5.00 (1H, dd, J1,2 6.1 Hz, J2,3 1.8 Hz, H-2), 6.19 (1H,
dd, J1,3 1.4 Hz, H-1), 7.20–7.30 (3H, m, Ar–H), 7.86–7.88 (2H,
m, Ar–H); δC (100.6 MHz, C6D6) 20.1, 23.0 (2 × s, 2 ×
C(CH3)3), 27.3, 27.7 (2 × q, 2 × C(CH3)3), 66.5 (t, C-6), 73.3 (d,
C-5), 75.4 (d, C-4), 76.5 (d, C-3), 85.7 (t, C᎐CH ), 100.7 (d, C-
᎐
2
Cpara Ar), 137.7 (s, Cipso Ar), 196.5 (s, C᎐O); NOE experi-
᎐
2), 126.0, 128.5, 128.9 (5 × d, Ar), 136.2 (s, Cipso Ar), 144.7 (d,
C-1), 160.1 (s, C᎐CH ); m/z (APCIϩ) 389 (MHϩ, 39%) (HRMS
ment (500 MHz, C6D6): Irradiate δ 5.00 (H-1Ј), enhancements:
2.68 (C(O)CHHЈ, 2.7%), 3.17 (C(O)CHHЈ, 2.7%), 3.74
(H-5Ј, 10.9%), 5.68 (H-2Ј, 5.3%). Irradiate δ 3.74 (H-5Ј),
enhancements: 4.30 (H-6Љ, 4.6%), 4.66 (H-4Ј, 1.8%), 5.00
(H-1Ј, 12.2%); m/z (APCIϩ) 389 (MHϩ, 21), 411 (MNaϩ,
7.5%). (HRMS calcd. for C22H33O4Si (MHϩ) 389.2148. Found:
389.2139) (Found: C, 67.85; H, 8.33. C22H32O4Si requires: C,
68.00: H, 8.30%).
᎐
2
calcd. for C22H33O4Si (MHϩ) 389.2148. Found 389.2142).
1,5-Anhydro-2-deoxy-4,6-O-di(tert-butyl)-3-O-(1-heptylethenyl)-
silanediyl-D-arabino-hex-1-enitol 7b
General method B: Tebbe reagent (0.97 ml, 0.48 mmol), glycal
ester 6b (50 mg, 0.12 mmol), tetrahydrofuran (2 ml) and
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3778

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Crystal data for 8a
methylaminopyridine (21 mg, 0.17 mmol) in pyridine (6 ml) at
0 ЊC in an atmosphere of argon. The reaction mixture was
stirred for 15 min, after which time TLC (petrol : ethyl acetate,
4 : 1) indicated the complete consumption of starting material
(Rf 0.2) and the formation of a single product (Rf 0.6). Meth-
anol (1 ml) was then added to the reaction mixture and the
solvent was removed in vacuo. The resulting residue was dissol-
ved in dichloromethane (30 ml), washed with water (2 × 30 ml),
dried (magnesium sulfate), filtered and concentrated in vacuo.
Purification of the product by recrystallisation (petrol–ethyl
acetate) afforded the ester 10a (272 mg, 94%) as white crystals;
mp 147–149 ЊC [Lit.28 146–147 ЊC (ethanol)]; [α]2D2 Ϫ245 (c, 1 in
CHCl3) [Lit.27 [α]2D3 Ϫ40.2 (c, 1 in CHC13)]; δH (400 MHz,
CDCl3) 3.92 (1H, at, J 10.4 Hz, H-6), 4.10 (1H, ddd, J4,5
10.3 Hz, J5,6 10.2 Hz, J5,6Ј 5.1 Hz, H-5), 4.24 (1H, dd, J3,4 7.8 Hz,
H-4), 4.45 (1H, dd, J6,6Ј 10.6 Hz, H-6Ј), 4.94 (1H, dd, J1,2 6.1 Hz,
J2,3 2.1 Hz, H-2), 5.66 (1H, s, CHPh), 5.83 (1H, dat, H-3), 6.46
(1H, dd, J1,3 1.3 Hz, H-1), 7.34–7.39 (3H, m, Ar–H), 7.43–7.51
(4H, m, Ar–H), 7.55–7.60 (1H, m, Ar–H), 8.06–8.09 (2H, m,
Ar–H).
C22H33O4Si, M = 388.58, monoclinic, a = 8.4698(2), b =
6.4952(2), c = 20.0695(4) Å, U = 1101.4 Å3, T = 150 K, space
group P21, Z = 2, µ(Mo–Kα) 0.129 mmϪ1, 10755 reflections
measured, 2712 unique (Rint = 0.039, R = 0.0319. The final wR
was 0.0373 (all data).
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-di(tert-butyl)silanediyl-2Ј,3Ј-dideoxy-
ꢀ-D-erythro-hex-2Ј-enopyranosyl)nonan-2-one 8b
General method C: Crude enol ether 7b (56 mg), in benzonitrile
(1 ml), gave the β-C-glycoside 8b (44.5 mg, 89% over two steps)
as a colourless oil; [α]2D2 ϩ25.8 (c, 1 in CHCl3); νmax (thin film)
1715 (s, C᎐O) cmϪ1; δH (500 MHz, C6D6) 0.88 (3H, t, J 7.1 Hz,
᎐
C(O)(CH2)6CH3), 1.09, 1.10 (18H, 2 × s, 2 × C(CH3)3), 1.14–
1.26 (8H, m, C(O)CH2CH2(CH2)4CH3), 1.48–1.51 (2H, m,
C(O)CH2CH2(CH2)4CH3), 2.01–2.08 (3H, m, C(O)CHHЈ and
CH2C(O)CH2(CH2)5CH3), 2.41 (1H, dd, J1Ј,C(O)CHHЈ 7.6 Hz, Jgem
16.0 Hz, C(O)CHHЈ), 3.59 (1H, ddd, J4Ј,5Ј 8.5 Hz, J5Ј,6Ј 10.3 Hz,
J5Ј,6Љ 5.1 Hz, H-5Ј), 3.94 (1H, at, J 10.2 Hz, H-6Ј), 4.21 (1H, dd,
J6Ј,6Љ 10.0 Hz, H-6Љ), 4.52–4.55 (1H, m, H-4Ј), 4.65–4.67 (1H, m,
H-1Ј), 5.43 (1H, dat, J2Ј,3Ј 10.4 Hz, J 1.8 Hz, H-2Ј), 5.91 (1H, br
d, J 10.3 Hz, H-3Ј); δC (100.6 MHz, C6D6) 14.6 (q, C(O)-
(CH2)6CH3), 20.5, 23.2 (2 × s, 2 × C(CH3)3), 27.6, 27.9 (2 × q,
2 × C(CH3)3), 23.3, 24.0, 29.7, 29.8, 32.3 (5 × t, C(O)CH2-
(CH2)5CH3), 43.9 (t, C(O)CH2(CH2)5CH3), 48.1 (t, CH2CO-
(CH2)6CH3), 67.8 (t, C-6Ј), 71.1 (d, C-4Ј), 72.6 (d, C-1Ј), 75.5 (d,
3-O-Acetyl-1,5-anhydro-4,6-O-benzylidene-2-deoxy-D-arabino-
hex-1-enitol 10b
A mixture of alcohol 9 (100 mg, 0.43 mmol) and acetic
anhydride (0.40 ml, 4.27 mmol) in pyridine (0.35 ml, 4.27
mmol) was stirred at room temperature for 1 h, after which time
TLC (petrol : ethyl acetate, 4 : 1) indicated the complete con-
sumption of starting material (Rf 0.2) and the formation of a
single product (Rf 0.6). Water (1 ml) was then added to the
reaction mixture and the solvent was concentrated in vacuo.
The resulting residue was dissolved in dichloromethane (20 ml),
washed with water (2 × 20 ml), dried (magnesium sulfate), fil-
tered and concentrated in vacuo. The product was purified by
flash column chromatography (petrol : ethyl acetate, 8 : 1) to
afford acetate 10b (113 mg, 96%) as a white crystalline solid;
mp 140–141 ЊC (petrol–ethyl acetate) [Lit.15 mp 136–137 ЊC
(acetone–hexane)]; [α]2D2 Ϫ102 (c, 1 in CHCl3) [Lit.15 [α]2D7 Ϫ85 (c,
1 in CHC13)]; δH (200 MHz, CDCl3) 2.10 (3H, s, CH3), 3.81–
4.11 (3H, m, H-4, H-5 and H-6), 4.38–4.45 (1H, m, H-6Ј), 4.83
(1H, dd, J1,2 6.1 Hz, J2,3 2.0 Hz, H-2), 5.55 (1H, dd, J3,4 7.8 Hz,
H-3), 5.62 (1H, s, CHPh), 6.41 (1H, dd, J1,3 1.4 Hz, H-1), 7.32–
7.41 (3H, m, Ar–H), 7.45–7.54 (2H, m, Ar–H).
C-5Ј), 129.8 (d, C-2Ј), 130.6 (d, C-3Ј), 206.6 (s, C᎐O); NOE
᎐
experiment (500 MHz, C6D6): Irradiate δ 4.66 (H-1Ј), enhance-
ments: 2.05 (CH2CO(CH2)5CH3, 3.3%), 3.59 (H-5Ј, 10.0%),
5.43 (H-2Ј, 4.9%). Irradiate δ 3.59 (H-5Ј), enhancements: 4.21
(H-6Ј, 3.9%), 4.66 (H-1Ј, 10.3%); m/z (APCIϩ) 411 (MHϩ, 34%)
(HRMS calcd. for C23H43O4Si (MHϩ) 411.2931. Found:
411.2940).
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-di(tert-butyl)silanediyl-2Ј,3Ј-dideoxy-
ꢀ-D-erythro-hex-2Ј-enopyranosyl)heptadecan-2-one 8c
General method C: Crude enol ether 7c (58 mg), in tributyl-
amine (1 ml), gave the β-C-glycoside 8c (44 mg, 88% over two
steps) as a white foam; [α]2D5 ϩ 8.0 (c, 0.5 in CHCl3); νmax (thin
film) 1716 (s, C᎐O) cmϪ1; δH (400 MHz, C6D6) 0.91 (3H, t, J 6.8
᎐
Hz, C(O)(CH2)14CH3), 1.09, 1.10 (18H, 2 × s, 2 × C(CH3)3),
1.17–1.32 (24H, m, C(O)CH2CH2(CH2)12CH3), 1.49–1.56 (2H,
m, C(O)CH2CH2(CH2)12CH3), 2.02–2.08 (3H, m, C(O)CHHЈ
and CH2C(O)CH2(CH2)13CH3), 2.41 (1H, dd, J1Ј,C(O)CHHЈ 7.7 Hz,
Jgem 16.0 Hz, C(O)CHHЈ), 3.59 (1H, ddd, J4Ј,5Ј 8.5 Hz, J5Ј,6Ј 10.4
Hz, J5Ј,6Љ 5.1 Hz, H-5Ј), 3.94 (1H, at, J 10.2 Hz, H-6Ј), 4.22 (1H,
dd, J6Ј,6Љ 9.9 Hz, H-6Љ), 4.52–4.56 (1H, m, H-4Ј), 4.64–4.67 (1H,
m, H-1Ј), 5.42 (1H, dat, J2Ј,3Ј 10.4 Hz, J 1.9 Hz, H-2Ј), 5.91 (1H,
br d, J 10.3 Hz, H-3Ј); δC (100.6 MHz, C6D6) 14.7 (q,
C(O)(CH2)14CH3), 20.6, 23.2 (2 × s, 2 × C(CH3)3), 27.6, 27.9
(2 × q, 2 × C(CH3)3), 23.4, 24.0, 29.8, 30.1, 30.2, 30.2, 30.4, 30.4,
30.4, 30.5, 30.5, 30.5, 32.6 (13 × t, C(O)CH2(CH2)13CH3), 43.9
(t, C(O)CH2(CH2)13CH3), 48.1 (t, CH2CO(CH2)14CH3), 67.8
(t, C-6Ј), 71.1 (d, C-4Ј), 72.6 (d, C-1Ј), 75.5 (d, C-5Ј), 129.8
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-(1-phenylethenyl)-
D-arabino-hex-1-enitol 11a
General method B: Tebbe reagent (2.36 ml, 1.18 mmol), glycal
ester 10a (100 mg, 0.30 mmol) in tetrahydrofuran (4 ml) and
pyridine (1 ml), gave enol ether 11a (106 mg) as a white foam.
This unstable compound was used in the next step with out
further purification; νmax (thin film): 1640 (C᎐C), 1594 (w, C᎐C)
᎐
᎐
cmϪ1; δH (400 MHz, C6D6) 3.49 (1H, at, J 10.4 Hz, H-6), 3.76
(1H, ddd, J4,5 10.3 Hz, J5,6 10.3 Hz, J5,6Ј 5.2 Hz, H-5), 4.05 (1H,
dd, J3,4 7.6 Hz, H-4), 4.14 (1H, dd, J6,6Ј 10.5 Hz, H-6Ј), 4.32 (1H,
d, Jgem 2.8 Hz, C᎐CHHЈ), 4.72 (1H, d, C᎐CHHЈ), 4.86 (1H, dd,
᎐
᎐
J1,2 6.2 Hz, J2,3 1.7 Hz, H-2), 4.94 (1H, br d, J 7.6 Hz, H-3), 5.29
(1H, s, CHPh), 6.05 (1H, d, H-1), 7.04–7.15 (6H, m, Ar–H),
7.54–7.57 (2H, m, Ar–H), 7.72–7.75 (2H, m, Ar–H); δC (100.6
MHz,C6D6) 68.6 (t, C-6), 69.4 (d, C-5), 72.5 (d, C-3), 78.5 (d,
(d, C-2Ј), 130.6 (d, C-3Ј), 206.6 (s, C᎐O); NOE experiment (500
᎐
MHz, C6D6): Irradiate δ 4.66 (H-1Ј), enhancements: 2.05
(CH2C(O)(CH2)14CH3, 3.5%), 2.41 (C(O)CHHЈ, 1.9%), 3.59
(H-5Ј, 9.0%), 5.42 (H-2Ј, 5.0%). Irradiate δ 3.59 (H-5Ј), enhance-
ments: 4.22 (H-6Љ, 4.1%), 4.54 (H-4Ј, 1.8%), 4.66 (H-1Ј, 9.7%),
5.91 (H-3Ј, 0.7%); m/z (ESϩ) 523 (MHϩ, 100), 540 (MNH4ϩ, 48),
545 (MNaϩ, 30), 561 (MKϩ, 12%). (HRMS calcd. for C31H62O4-
SiN (MNH4ϩ) 540.4448. Found: 540.4447) (Found: C, 71.07; H,
11.15. C31H58O4Si requires: C, 71.21: H, 11.18%).
C-4), 85.5 (t, C᎐CH ), 100.6 (d, C-2), 101.9 (d, CHPh), 126.4,
᎐
2
126.9, 128.6, 128.7, 129.1, 129.3 (10 × d, Cortho,
Ar),
meta and para
137.4, 138.3 (2 × s, Cipso Ar), 145.2 (d, C-1), 159.4 (s, C᎐CH );
᎐
2
m/z (CIϩ) 337 (MHϩ, 10%).
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-(2-propenyl)-D-
arabino-hex-1-enitol 11b
1,5-Anhydro-3-O-benzoyl-4,6-O-benzylidene-2-deoxy-D-arabino-
hex-1-enitol 10a
General method B: Tebbe reagent (1.74 ml, 0.87 mmol), glycal
ester 10b (120 mg, 0.43 mmol) in tetrahydrofuran (4 ml) and
pyridine (1 ml), gave enol ether 11b (130 mg) as a pale yellow
crystalline solid. This unstable compound was used in the next
Benzoyl chloride (0.20 ml, 1.71 mmol) was added drop-wise to
a stirred solution of alcohol 9 (200 mg, 0.85 mmol) and 4-di-
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3779

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step with out further purification; νmax (thin film): 1661, 1635
group P212121, Z = 4, µ(Mo–Kα) 0.093 mmϪ1, 14624 reflections
measured, 1883 unique (Rint = 0.051), R = 0.0315. The final wR
(m, 2 × C᎐C) cmϪ1; δH (400 MHz, C6D6) 1.75 (3H, s, CH3), 3.44
᎐
(1H, at, J 10.4 Hz, H-6), 3.74 (1H, ddd, J4,5 10.3 Hz, J5,6 10.3
was 0.0355 (all data).
Hz, J5,6Ј 5.2 Hz, H-5), 3.95 (1H, br s, C᎐CHHЈ), 3.96 (1H, d,
᎐
Jgem 1.3 Hz, C᎐CHHЈ), 3.98 (1H, dd, J3,4 7.6 Hz, H-4), 4.11 (1H,
᎐
1,5-Anhydro-2-deoxy-4,6-O-di(tert-butyl)silanediyl-D-ribo-hex-
dd, J6,6Ј 10.5 Hz, H-6Ј), 4.82 (1H, d, J2,3 1.7 Hz, H-3), 4.87 (1H,
dd, J1,2 6.2 Hz, H-2), 5.28 (1H, s, CHPh), 6.03 (1H, dd, H-1),
7.06–7.15 (3H, m, Ar–H), 7.53–7.56 (3H, m, Ar–H); δC (100.6
MHz, C6D6) 21.6 (q, CH3), 68.6 (t, C-6), 69.4 (d, C-5), 71.6 (d,
1-enitol 14
Di-tert-butylsilyl bistrifluoromethanesulfonate (0.96 ml, 2.63
mmol) was added drop-wise over 15 min to a stirred solution of
allal 13 (350 mg, 2.39 mmol) in dimethylformamide (10 ml) at
Ϫ40 ЊC in an atmosphere of argon. The resulting reaction mix-
ture was stirred for 1 h, after which time TLC (ethyl acetate :
methanol, 19 : 1) indicated the complete consumption of start-
ing material (Rf 0.4) and the formation of a major product (Rf
0.9). Pyridine (0.23 ml, 2.87 mmol) was then added to the reac-
tion mixture and stirred for a further 10 min. The mixture was
diluted with diethyl ether (50 ml), washed with a solution of
saturated sodium hydrogen carbonate (25 ml) and then with
water (2 × 25 ml). The organic layer was dried (magnesium
sulfate), filtered and concentrated in vacuo. The resultant resi-
due was purified by flash column chromatography (petrol : ethyl
acetate, 6 : 1) to afford the alcohol 14 (528 mg, 77%) as a white
crystalline solid; mp 67–68 ЊC (petrol); [α]2D4 ϩ117 (c, 1 in
C-3), 78.4 (d, C-4), 83.6 (t, C᎐CH ), 100.6 (d, C-2), 102.1 (d,
᎐
2
CHPh), 127.1, 128.5, 129.3 (5 × d, Cortho, meta and para Ar), 138.3 (s,
Cipso Ar) 145.0 (d, C-1), 158.5 (s, C᎐CH ); m/z (CIϩ) 275 (MHϩ,
᎐
2
6%).
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-ꢀ-D-
erythro-hex-2Ј-enopyranosyl)acetophenone 12a
General method C: Crude enol ether 11a (106 mg), in tributyl-
amine (2 ml), gave β-C-glycoside 12a (70 mg, 71% over two
steps) as a white crystalline solid, mp 99–100 ЊC (petrol–diethyl
ether); [α]2D5 ϩ57 (c, 0.5 in CHCl ); ν (KBr disc): 1683 (s, C᎐O)
᎐
3
max
cmϪ1; δH (400 MHz, C6D6) 2.67 (1H, dd, J1Ј,C(O)CHHЈ 6.5 Hz, Jgem
16.6 Hz, C(O)CHHЈ), 3.11 (1H, dd, J1Ј,C(O)CHHЈ 6.7 Hz,
C(O)CHHЈ), 3.57 (1H, at, J 10.0 Hz, H-6Ј), 3.61–3.67 (1H, m,
H-5Ј), 4.04–4.07 (1H, m, H-4Ј), 4.19 (1H, dd, J5Ј,6Љ 4.1 Hz, J6Ј,6Љ
9.6 Hz, H-6Љ), 4.90–4.94 (1H, m, H-1Ј), 5.43 (1H, s, CHPh),
5.63 (1H, dat, J2Ј,3Ј 10.4 Hz, J 2.1 Hz, H-2Ј), 5.99 (1H, br d,
J 10.4 Hz, H-3Ј), 7.06–7.10 (2H, m, Ar–H), 7.14–7.20 (4H, m,
Ar–H), 7.62–7.64 (2H, m, Ar–H), 7.76–7.79 (2H, m, Ar–H);
δC (100.6 MHz, C6D6) 43.6 (t, CH2COPh), 69.3 (t, C-6Ј), 71.1
(d, C-5Ј), 72.5 (d, C-1Ј), 75.2 (d, C-4Ј), 101.9 (d, CHPh), 126.6,
127.0, 127.5, 127.7, 127.8, 128.0, 128.0, 128.1, 128.3, 128.7,
130.7, 132.7 (12 × d, C-2Ј, C-3Ј and Cortho, meta and para Ar), 137.2,
CHCl3); νmax (KBr disc): 3580 (br, OH), 1643 (s, C᎐C) cmϪ1
;
᎐
δH (400 MHz, CDCl3) 1.04, 1.08 (18H, 2 × s, 2 × C(CH3)3), 2.69
(1H, s, OH), 3.94–4.06 (3H, m, H-4, H-5 and H-6), 4.15–4.17
(1H, m, H-3), 4.28 (1H, dd, J5,6Ј 3.5 Hz, J6,6Ј 9.3 Hz, H-6Ј), 5.00
(1H, at, J 5.9 Hz, H-2), 6.41 (1H, d, J1,2 6.0 Hz, H-1); δC (100.6
MHz, CDCl3) 20.2, 22.8 (2 × s, 2 × C(CH3)3), 27.1, 27.4 (2 × q,
2 × C(CH3)3), 61.6 (d, C-3), 65.9 (t, C-6), 67.8 (d, C-5), 74.4 (d,
C-4), 100.5 (d, C-2), 145.8 (d, C-1); m/z (FIϩ) 286 (Mϩ, 100%).
(HRMS calcd. for C14H26O4Si (Mϩ) 286.1600. Found 286.1613)
(Found: C, 58.74; H, 9.13. C14H26O4Si requires C, 58.70; H,
9.15%).
138.3 (2 × s, Cipso Ar), 195.8 (s, C᎐O); NOE experiment (500
᎐
MHz, C6D6): Irradiate δ 4.92 (H-1Ј), enhancements: 2.67
(C(O)CHHЈ, 1.9%), 3.11 (C(O)CHHЈ, 1.8%), 3.64 (H-5Ј,
11.3%), 5.63 (H-2Ј, 4.2%). Irradiate δ 3.64 (H-5Ј), enhance-
ments: 4.06 (H-4Ј, 1.2%), 4.19 (H-6Љ, 3.9%), 4.92 (H-1Ј, 10.6%),
5.99 (H-3Ј, 0.9%); m/z (CIϩ) 337 (MHϩ, 25%). (HRMS calcd.
for C21H21O4 (MHϩ) 337.1439. Found: 337.1434) (Found: C,
74.92; H, 6.01. C21H20O4 requires: C, 74.98: H, 5.99%).
1,5-Anhydro-2-deoxy-4,6-O-di(tert-butyl)silanediyl-3-O-hexa-
decanoyl-D-ribo-hex-1-enitol 17
General method A: Alcohol 14 (250 mg, 0.87 mmol), palmitic
acid (448 mg, 1.75 mmol), dicyclohexylcarbodiimide (360 mg,
1.75 mmol) and 4-dimethylaminopyridine (21 mg, 0.17 mmol),
in dichloromethane (8 ml), gave the ester 17 (447 mg, 98%) as a
colourless oil; [α]2D5 ϩ186 (c, 1 in CHCl3); νmax (thin film) 1738 (s,
C᎐O), 1643 (m, C᎐C) cmϪ1; δH (400 MHz, CDCl3) 0.88 (3H, t,
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-ꢀ-D-
erythro-hex-2Ј-enopyranosyl)propan-2-one 12b
᎐
᎐
J 6.8 Hz, O2C(CH2)14CH3), 1.02 and 1.05 (18H, 2 × s, 2 ×
C(CH3)3), 1.26–1.29 (24H, m, O2C.CH2CH2(CH2)12CH3), 1.62–
1.65 (2H, m, O2C.CH2CH2(CH2)12CH3), 2.30–2.34 (2H, m,
O2C.CH2(CH2)13CH3), 3.96 (1H, at, J 10.2 Hz, H-6), 4.09 (1H,
ddd, J4,5 10.5 Hz, J5,6 10.3 Hz, J5,6Ј 4.7 Hz, H-5), 4.19 (1H, dd,
J3,4 3.9 Hz, H-4), 4.26 (1H, dd, J6,6Ј 10.1 Hz, H-6Ј), 4.97 (1H, at,
J 6.0 Hz, H-2), 5.30 (1H, dd, J2,3 5.9 Hz, H-3), 6.40 (1H, d, J1,2
5.9 Hz, H-1); δC (100.6 MHz, CDCl3) 14.1 (q, O2C(CH2)14CH3),
20.1, 22.7 (2 × s, 2 × C(CH3)3), 26.8, 27.3 (2 × q, 2 × C(CH3)3),
22.7, 24.8, 29.1, 29.2, 29.3, 29.4, 29.6, 29.6, 29.7, 29.7, 31.9
(11 × t, O2CCH2(CH2)13CH3), 34.4 (t, O2CCH2(CH2)13CH3),
64.1 (d, C-3), 65.9 (t, C-6), 68.9 (d, C-5), 72.7 (d, C-4), 98.4 (d,
General method C: Crude enol ether 11b (130 mg), in tributyl-
amine (2 ml), gave β-C-glycoside 12b (94 mg, 80% over two
steps) as a white crystalline solid; mp 67 ЊC (petrol); [α]2D5 ϩ80 (c,
1 in CHCl3); νmax (KBr disc): 1708 (s, C᎐O) cmϪ1; δH (500 MHz,
᎐
C6D6) 1.71 (3H, s, CH3), 2.02 (1H, dd, J1Ј,C(O)CHHЈ 5.7 Hz,
Jgem 16.1 Hz, C(O)CHHЈ), 2.35 (1H, dd, J1Ј,C(O)CHHЈ 7.6 Hz,
C(O)CHHЈ), 3.53–3.59 (2H, m, H-5Ј and H-6Ј), 3.98–4.00 (1H,
m, H-4Ј), 4.18 (1H, m, H-6Љ), 4.54–4.58 (1H, m, H-1Ј), 5.39
(1H, dat, J2Ј,3Ј 10.4 Hz, J 2.1 Hz, H-2Ј), 5.41 (1H, s, CHPh), 5.93
(1H, br d, J 10.4 Hz, H-3Ј), 7.15–7.25 (3H, m, Ar–H), 7.67–7.69
(2H, m, Ar–H); δC (125.7 MHz, C6D6) 28.8 (q, CH3), 46.9 (t,
CH2COCH3), 68.1 (t, C-6Ј), 70.0 (d, C-5Ј), 71.2 (d, C-1Ј), 73.9
(d, C-4Ј), 100.7 (d, CHPh), 125.5 (2 × d, Ar), 125.9 (d, C-3Ј),
126.9 (2 × d, Ar), 127.6 (d, Cpara Ar), 129.2 (d, C-2Ј), 137.2 (s,
C-2), 146.6 (d, C-1), 173.3 (s, C᎐O); m/z (FIϩ) 524 (Mϩ, 69%).
᎐
(HRMS calcd. for C30H56O5Si (Mϩ) 524.3897. Found 524.3876)
(Found: C, 68.83; H, 10.77. C30H56O5Si requires C, 68.65; H,
10.75%).
Cipso Ar), 204.0 (s, C᎐O); NOE experiment (500 MHz, C D ):
᎐
6
6
Irradiate δ 4.56 (H-1Ј), enhancements: 2.02 (C(O)CHHЈ, 2.8%),
2.35 (C(O)CHHЈ, 2.8%), 3.56 (H-5Ј and H-6Љ, 9.0%), 5.39
(H-2Ј, 4.4%). Irradiate δ 3.56 (H-5Ј and H-6Ј), enhancements:
3.99 (H-4Ј, 1.9%), 4.18 (H-6Љ, 14.2%), 4.56 (H-1Ј, 6.3%), 5.41
(CHPh, 3.8%); m/z (CIϩ) 275 (MHϩ, 15%), 292 (MNH4ϩ, 12%).
(Found: C, 70.05; H, 6.65. C16H18O4 requires: C, 70.06; H,
6.61%).
1,5-Anhydro-3-O-benzoyl-4,6-O-benzylidene-2-deoxy-D-ribo-
hex-1-enitol 18a
Benzoyl chloride (0.8 ml, 6.8 mmol) was added drop-wise to a
stirred solution of the alcohol 15 (400 mg, 1.71 mmol) and
4-dimethylaminopyridine (42 mg, 0.34 mmol) in pyridine (3 ml)
at 0 ЊC in an atmosphere of argon. The reaction mixture was
stirred for 15 min, after which time TLC (petrol : ethyl acetate;
3 : 1) indicated the complete consumption of starting material
(Rf 0.3) and the formation of a single product (Rf 0.5).
Crystal data for 12b
C16H18O4, M = 274.32, orthorhombic, a = 5.1126(5), b =
14.2991(2), c = 19.1347(8) Å, U = 1398.9 Å3, T = 150 K, space
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3780

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Methanol (1.5 ml) was then added to quench the reaction mix-
ture and the solvent was evaporated in vacuo. The resulting
residue was dissolved in dichloromethane (50 ml), washed with
water (2 × 50 ml), dried (magnesium sulfate), filtered and con-
centrated in vacuo. The purification of the product by flash
column chromatography (petrol : ethyl acetate, 4 : 1) afforded
the ester 18a (537 mg, 93%) as colourless crystals; mp 77–78 ЊC
(petrol–ethyl acetate); [α]2D5 ϩ383.5 (c, 1 in CHCl3); νmax (KBr
disc) 1717 (s, C᎐O), 1636 (m, C᎐C) cmϪ1; δH (400 MHz, CDCl3)
76.1 (d, C-4), 98.5 (d, C-2), 101.5 (d, CHPh), 126.1, 128.2
(2 × d, Cortho
Ar), 129.0 (d, Cpara Ar), 137.1 (s, Cipso Ar),
and meta
147.2 (d, C-1), 173.4 (s, C᎐O); m/z (FIϩ) 472 (Mϩ, 100%).
᎐
(HRMS calcd. for C29H44O5 (Mϩ) 472.3189. Found 472.3188)
(Found: C, 73.75; H, 9.41. C29H44O5 requires C, 73.69; H,
9.38%).
1,5-Anhydro-3-O-benzoyl-4,6-O-benzylidene-2-deoxy-2-methyl-
D-ribo-hex-1-enitol 19
᎐
᎐
3.91 (1H, at, J 10.4 Hz, H-6), 4.11 (1H, dd, J3,4 3.8 Hz, J4,5 10.4
Hz, H-4), 4.37 (1H, ddd, J5,6 10.3 Hz, J5,6Ј 5.2 Hz, H-5), 4.52
(1H, dd, J6,6Ј 10.6 Hz, H-6Ј), 5.19 (1H, at, J 6.0 Hz, H-2), 5.64–
5.66 (1H, m, H-3), 5.66 (1H, s, CHPh), 6.56 (1H, d, J1,2 6.0 Hz,
H-1), 7.28–7.32 (3H, m, Ar–H), 7.41–7.48 (4H, m, Ar–H),
7.56–7.60 (1H, m, Ar–H), 8.10–8.13 (2H, m, Ar–H); δC (100.6
MHz, CDCl3) 62.8 (d, C-3), 65.2 (d, C-5), 68.7 (t, C-6), 76.1 (d,
C-4), 98.5 (d, C-2), 101.7 (d, CHPh), 126.1, 128.2, 128.3, 129.7
Benzoyl chloride (0.19 ml, 1.61 mmol) was added drop-wise to
a stirred solution of the alcohol 16 (100 mg, 0.40 mmol) and
4-dimethylaminopyridine (9.8 mg, 0.08 mmol) in pyridine
(1 ml) at 0 ЊC, under an atmosphere of argon. The reaction
mixture was stirred for 15 min, after which time TLC (petrol :
ethyl acetate; 3 : 1) indicated the complete consumption of
starting material (Rf 0.4) and the formation of a single product
(Rf 0.6). Methanol (1.0 ml) was then added to quench the reac-
tion mixture and the solvent evaporated in vacuo. The resulting
residue was dissolved in dichloromethane (15 ml), washed with
water (2 × 15 ml), dried (magnesium sulfate), filtered and con-
centrated in vacuo. The purification of the product by flash
column chromatography (petrol : ethyl acetate, 3 : 1) afforded
the ester 19 (134 mg, 94%) as a white crystalline solid; mp 75–76
ЊC (petrol–diethyl ether); [α]2D5 ϩ299 (c, 1 in CHCl3); νmax (KBr
disc) 1721 (s, C᎐O), 1662 (w, C᎐C) cmϪ1; δH (400 MHz, CDCl3)
1.73 (3H, s, CH3), 3.88 (1H, at, J 10.4 Hz, H-6), 4.07 (1H, dd,
J3,4 4.0 Hz, J4,5 10.5 Hz, H-4), 4.20 (1H, ddd, J5,6 10.3 Hz, J5,6Ј
5.2 Hz, H-5), 4.49 (1H, dd, J6,6Ј 10.6 Hz, H-6Ј), 5.63 (1H, s,
CHPh), 5.80 (1H, d, H-3), 6.41 (1H, s, H-1), 7.21–7.29 (3H, m,
Ar–H), 7.31–7.33 (2H, m, Ar–H), 7.45–7.49 (2H, m, Ar–H),
7.57–7.60 (1H, m, Ar–H), 8.12–8.14 (2H, m, Ar–H); δC (100.6
MHz, CDCl3) 15.7 (q, CH3), 64.6 (d, C-5), 66.0 (d, C-3), 68.7 (t,
C-6), 76.2 (d, C-4), 101.3 (d, CHPh), 106.6 (s, C-2), 126.0,
(4 × d, Cortho
Ar), 129.1 (d, Cpara Ar), 130.3 (s, Cipso Ar),
and meta
133.0 (d, Cpara Ar), 137.0 (s, Cipso Ar), 147.5 (d, C-1), 166.1 (s, C᎐
᎐
O); m/z (CIϩ) 339 (MHϩ, 8%), 356 (MNH4ϩ, 11%). (Found C,
71.02; H, 5.36. C20H18O5 requires C, 71.00; H, 5.36%).
3-O-Acetyl-1,5-anhydro-4,6-O-benzylidene-2-deoxy-D-ribo-hex-
1-enitol 18b
᎐
᎐
A mixture of the alcohol 15 (400 mg, 1.71 mmol) and acetic
anhydride (0.8 ml, 8.5 mmol) in pyridine (0.7 ml, 8.5 mmol) was
stirred at room temperature for 4 h, after which time TLC (pet-
rol : ethyl acetate; 3 : 1) indicated the complete consumption of
starting material (Rf 0.3) and the formation of a single product
(Rf 0.5). Water (5 ml) was then added to the reaction mixture
and the solvent was evaporated in vacuo. The resulting residue
was dissolved in dichloromethane (50 ml), washed with water
(3 × 50 ml), dried (magnesium sulfate), filtered and concen-
trated in vacuo. The product was purified by recrystallisation
from petrol–ethyl acetate to afford the acetate 18b (457 mg,
97%) as a colourless crystalline solid; mp 123 ЊC; [α]2D5 ϩ271 (c, 1
128.1, 128.3, 129.8 (4 × d, Cortho
Ar), 128.9 (d, Cpara Ar),
and meta
130.2 (s, Cipso Ar), 133.0 (d, Cpara Ar), 137.0 (d, Cipso Ar), 142.3
(d, C-1), 166.6 (s, C᎐O); m/z (EIϩ) 352 (Mϩ, 9), 353 (MHϩ, 1%).
᎐
in CHCl3); νmax (KBr disc) 1732 (s, C᎐O), 1633 (w, C᎐C) cmϪ1
;
(HRMS calcd. for C21H20O5 (M) 352.1311. Found: 352.1293)
(Found: C, 71.75; H, 5.76. C21H20O5 requires C, 71.58; H,
5.72%).
᎐
᎐
δH (400 MHz, CDCl3) 2.11 (3H, s, CH3), 3.85 (1H, at, J 10.4 Hz,
H-6), 3.99 (1H, dd, J3,4 3.9 Hz, J4,5 10.5 Hz, H-4), 4.20 (1H, ddd,
J5,6 10.4 Hz, J5,6Ј 5.2 Hz, H-5), 4.48 (1H, dd, J6,6Ј 10.6 Hz, H-6Ј),
5.02 (1H, at, J 6.0 Hz, H-2), 5.45 (1H, dd, J2,3 5.9 Hz, H-3), 5.62
(1H, s, CHPh), 6.51 (1H, d, J1,2 6.0 Hz, H-1), 7.37–7.41 (3H, m,
Ar–H), 7.46–7.49 (2H, m, Ar–H); δC (100.6 MHz, CDCl3) 21.2
(q, CH3), 62.0 (d, C-3), 64.9 (d, C-5), 68.6 (t, C-6), 76.0 (d, C-4),
98.4 (d, C-2), 101.5 (d, CHPh), 126.0, 128.3 (2 × d, Cortho and meta
Ar), 129.1 (d, Cpara Ar), 137.0 (s, Cipso Ar), 147.3 (d, C-1), 170.6
(s, C᎐O); m/z (CIϩ) 277 (MHϩ, 11), 294 (MNH ϩ, 5%). (Found:
1,5-Anhydro-2-deoxy-4,6-O-di(tert-butyl)silanediyl-3-O-(hepta-
dec-1-en-2-yl)-D-ribo-hex-1-enitol 20
General method B: Tebbe reagent (3.1 ml, 1.5 mmol), ester 17
(200 mg, 0.38 mmol) in tetrahydrofuran (8 ml) and pyridine
(2 ml), gave the enol ether 20 (192 mg, 96%) as a colourless oil;
[α]2D5 ϩ166 (c, 1 in diethyl ether); νmax (thin film): 1646, 1640
᎐
4
(w, 2 × C᎐C); δ (400 MHz, C6D6) 0.91 (3H, t, J 6.8 Hz,
᎐
H
C, 65.39; H, 5.86. C15H16O5 requires C, 65.21; H, 5.84%).
(CH2)14CH3), 1.06, 1.16 (18H, 2 × s, 2 × C(CH3)3), 1.31–1.37
(24H, m, (CH2)2(CH2)12CH3), 1.61–1.66 (2H, m, CH2CH2-
(CH2)12CH3), 2.15 (1H, m, J 7.3 Hz, CHHЈ(CH2)13CH3), 2.26
(1H, m, CHHЈ(CH2)13CH3), 3.93 (1H, at, J 10.4 Hz, H-6), 3.96
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-hexadecanoyl-D-
ribo-hex-1-enitol 18c
(1H, d, Jgem 1.8 Hz, C᎐CHHЈ), 4.03 (1H, d, C᎐CHHЈ), 4.08 (1H,
᎐
᎐
General method A: Alcohol 15 (200 mg, 0.85 mmol), palmitic
acid (438 mg, 1.71 mmol), dicyclohexylcarbodiimide (352 mg,
1.71 mmol) and 4-dimethylaminopyridine (21 mg, 0.17 mmol),
in anhydrous dichloromethane (8 ml), gave the ester 18c (401
mg, 99%) as a white crystalline solid; mp 62–63 ЊC (petrol);
dd, J3,4 3.8 Hz, J4,5 10.4 Hz, H-4), 4.24 (1H, dd, J5,6Ј 4.9 Hz, J6,6Ј
10.1 Hz, H-6Ј), 4.31 (1H, ddd, J5,6 10.4 Hz, H-5), 4.34 (1H, dd,
J2,3 5.6 Hz, H-3), 4.91 (1H, at, J 5.8 Hz, H-2), 6.11 (1H, d, J1,2
6.0 Hz, H-1); δC (100.6 MHz, C6D6) 14.6 (q, (CH2)14CH3), 20.8,
23.2 (2 × s, 2 × C(CH3)3), 27.5, 27.9 (2 × q, 2 × C(CH3)3), 23.4,
28.2, 29.9, 30.1, 30.2, 30.4, 30.4, 30.5, 30.5, 30.5, 32.6 (11 × t,
CH2(CH2)13CH3), 36.2 (t, CH2(CH2)13CH3), 66.7 (t, C-6), 67.3
[α]D25 ϩ175 (c, 1 in CHCl3); νmax (KBr disc) 1742 (s, C᎐O), 1634
᎐
(m, C᎐C) cmϪ1; δH (400 MHz, CDCl3) 0.90 (3H, t, J 6.7 Hz,
᎐
O2C(CH2)14CH3), 1.24–1.30 (24H, m, O2C.CH2CH2(CH2)12-
CH3), 1.58–1.67 (2H, m, O2C.CH2CH2(CH2)12CH3), 2.35 (2H,
t, J 7.5 Hz, O2C.CH2(CH2)13CH3), 3.85 (1H, at, J 10.4 Hz, H-6),
3.99 (1H, dd, J3,4 4.0 Hz, J4,5 10.5 Hz, H-4), 4.19 (1H, ddd, J5,6
10.4 Hz, J5,6Ј 5.2 Hz, H-5), 4.47 (1H, dd, J6,6Ј 10.6 Hz, H-6Ј),
5.02 (1H, at, J 6.0 Hz, H-2), 5.47 (1H, dd, J2,3 5.8 Hz, H-3), 5.62
(1H, s, CHPh), 6.50 (1H, d, J1,2 6.0 Hz, H-1), 7.34–7.38 (3H, m,
Ar–H), 7.45–7.48 (2H, m, Ar–H); δC (100.6 MHz, CDCl3) 14.1
(q, O2C(CH2)14CH3), 22.7, 25.0, 29.1, 29.2, 29.3, 29.4, 29.6,
29.6, 29.7, 29.7, 31.9 (11 × t, O2CCH2(CH2)13CH3), 34.5 (t,
O2CCH2(CH2)13CH3), 61.7 (d, C-3), 64.9 (d, C-5), 68.6 (t, C-6),
(d, C-3), 69.4 (d, C-5), 74.8 (d, C-4), 82.3 (t, C᎐CH ), 99.2 (d,
᎐
2
C-2), 146.0 (d, C-1), 162.6 (s, C᎐CH ); m/z (FIϩ) 522 (Mϩ,
᎐
2
100%), (CIϩ). (HRMS calcd. for C31H58O4Si (Mϩ) 522.4104.
Found: 522.4103) (Found: C, 71.39; H, 11.19. C31H58O4Si
requires: C, 71.21: H, 11.18%).
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-(1-phenylethenyl)-
D-ribo-hex-1-enitol 21a
General method B: Tebbe reagent (14.2 ml, 7.1 mmol), ester 18a
(600 mg, 1.77 mmol) in tetrahydrofuran (24 ml) and pyridine
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3781

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(6 ml), gave the enol ether 21a (568 mg, 95%) as a white
crystalline solid; mp 75–76 ЊC; [α]2D6 ϩ334 (c, 1 in diethyl ether);
Found: 470.3387) (Found: C, 76.54; H, 9.88. C30H46O4 requires:
C, 76.55; H, 9.85%).
νmax (KBr disc): 1635 (C᎐C) cmϪ1; δH (400 MHz, C6D6) 3.32
᎐
(1H, at, J 10.4 Hz, H-6), 3.38 (1H, dd, J3,4 3.7 Hz, J4,5 10.5 Hz,
H-4), 4.04 (1H, dd, J5,6Ј 5.3 Hz, J6,6Ј 10.5 Hz, H-6Ј), 4.11 (1H, d,
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-2-methyl-3-O-
(1-phenylethenyl)-D-ribo-hex-1-enitol 22
Jgem 2.1 Hz, C᎐CHHЈ), 4.23 (1H, ddd, J5,6 10.4 Hz, H-5), 4.31–
᎐
General method B: Tebbe reagent (3.4 ml, 1.70 mmol), the ester
19 (150 mg, 0.43 mmol) in tetrahydrofuran (6 ml) and pyridine
(1.5 ml), gave the enol ether 22 (144 mg, 96%) as a colourless
oil; [α]2D5 ϩ181 (c, 1 in CHCl3); νmax (KBr disc): 1663, 1643
4.33 (1H, m, H-3), 4.56 (1H, d, C᎐CHHЈ), 4.69 (1H, at, J 5.9
᎐
Hz, H-2), 5.13 (1H, s, CHPh), 5.94 (1H, d, J1,2 6.1 Hz, H-1),
6.85–6.97 (6H, m, Ar–H), 7.40–7.42 (2H, m, Ar–H), 7.60–7.62
(2H, m, Ar–H); δC (100.6 MHz, C6D6) 65.4 (d, C-5), 66.7 (d,
(w, 2 × C᎐C) cmϪ1; δH (500 MHz, C6D6) 1.52 (3H, s, CH3),
᎐
C-3), 69.0 (t, C-6), 77.6 (d, C-4), 84.6 (t, C᎐CH ), 99.2 (d, C-2),
᎐
2
3.52–3.58 (2H, m, H-4 and H-6), 4.24–4.31 (2H, m, H-5 and
H-6Ј), 4.50 (1H, d, J3,4 3.7 Hz, H-3), 4.59 (1H, d, Jgem 2.6 Hz,
102.1 (d, CHPh), 126.3, 126.9, 128.4, 128.6 (4 × d, Cortho and meta
Ar), 128.8, 129.2 (2 × d, Cpara Ar), 137.5, 138.3 (2 × s, Cipso Ar),
146.5 (d, C-1), 160.1 (s, C᎐CH ); m/z (FIϩ) 336 (Mϩ, 100%).
C᎐CHHЈ), 4.81 (1H, d, C᎐CHHЈ), 5.33 (1H, s, CHPh), 6.04
᎐
᎐
᎐
2
(HRMS calcd. for C21H20O4 (Mϩ) 336.1362. Found: 336.1354)
(Found: C, 75.07; H, 6.03. C21H20O4 requires: C, 74.98: H,
5.99%).
(1H, s, H-1), 7.03–7.15 (6H, m, Ar–H), 7.55–7.57 (2H, m, Ar–
H), 7.77–7.79 (2H, m, Ar–H); δC (125.7 MHz, C6D6) 16.5 (q,
CH3), 64.7 (d, C-5), 69.3 (t, C-6), 72.0 (d, C-3), 78.5 (d, C-4),
86.1 (t, C᎐CH ), 102.1 (d, CHPh), 108.2 (s, C-2), 126.6, 127.0,
᎐
2
128.5, 128.6 (4 × d, Cortho
Ar), 128.9, 129.3 (2 × d,
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-(2-propenyl)-D-
ribo-hex-1-enitol 21b
and meta
Cpara Ar), 137.8, 138.5 (2 × s, Cipso Ar), 141.5 (d, C-1), 162.4 (s,
C᎐CH ); m/z (FIϩ) 350 (Mϩ, 100%). (HRMS calcd. for
᎐
2
C22H22O4 (Mϩ) 350.1518. Found: 350.1511) (Found: C, 75.42;
H, 6.32. C22H22O4 requires: C, 75.41: H, 6.33%).
General method B: Tebbe reagent (4.3 ml, 2.17 mmol), ester 18b
(150 mg, 0.54 mmol) in tetrahydrofuran (6 ml) and pyridine
(1.5 ml), gave the enol ether 21b (139 mg, 93%) as a white
crystalline solid; mp 93–94 ЊC; [α]2D6 ϩ241 (c, 1 in diethyl ether);
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-ꢁ-D-
erythro-hex-2Ј-enopyranosyl)acetophenone 23a
νmax (KBr disc): 1659, 1632 (2 × C᎐C) cmϪ1; δH (500 MHz,
᎐
C6D6) 1.75 (3H, s, CH3), 3.49 (1H, at, J 10.3 Hz, H-6), 3.53 (1H,
dd, J3,4 3.9 Hz, J4,5 10.4 Hz, H-4), 3.97 (2H, s, C᎐CH ), 4.23
General method D: Enol ether 21a (40 mg, 0.12 mmol) in
anhydrous xylene (1 ml), gave α-C-glycoside 23a (38.4 mg, 96%)
as a white crystalline solid; mp 130–131 ЊC (petrol–diethyl
᎐
2
(1H, dd, J5,6Ј 5.4 Hz, J6,6Ј 10.5 Hz, H-6Ј), 4.37 (1H, ddd, J5,6 10.4
Hz, H-5), 4.41 (1H, dd, J2,3 5.6 Hz, H-3), 4.89 (1H, at, J 5.9 Hz,
H-2), 5.29 (1H, s, CHPh), 6.11 (1H, d, J1,2 6.1 Hz, H-1), 7.07–
7.11 (1H, m, Ar–H), 7.14–7.17 (2H, m, Ar–H), 7.59–7.60 (2H,
m, Ar–H); δC (125.7 MHz, C6D6) 21.8 (q, CH3), 65.2, 65.4 (2 ×
ether); [α]2D5 ϩ32.5 (c, 1 in CHCl ); ν (KBr disc): 1679 (s, C᎐O)
᎐
3
max
cmϪ1; δH (400 MHz, C6D6) 2.52 (1H, dd, J1Ј,C(O)CHHЈ 6.0 Hz,
Jgem 16.3 Hz, C(O)CHHЈ), 3.07 (1H, dd, J1Ј,C(O)CHHЈ 7.6 Hz,
C(O)CHHЈ), 3.51 (1H, at, J 10.1 Hz, H-6Ј), 3.60 (1H, ddd,
J4Ј,5Ј 8.0 Hz, J5Ј,6Ј 10.2 Hz, J5,Ј6Љ 4.3 Hz, H-5Ј), 3.90–3.93 (1H, m,
H-4Ј), 4.07 (1H, dd, J6Ј,6Љ 10.0 Hz, H-6Љ), 4.99–5.04 (1H, m,
H-1Ј), 5.33 (1H, s, CHPh), 5.53 (1H, dat, J2Ј,3Ј 10.4 Hz, J 2.5 Hz,
H-2Ј), 5.94 (1H, br d, J 10.4 Hz, H-3Ј), 7.00–7.04 (2H, m,
Ar–H), 7.09–7.20 (4H, m, Ar–H), 7.63–7.65 (2H, m, Ar–H),
7.71–7.73 (2H, m, Ar–H); δC (100.6 MHz, C6D6) 42.2 (t,
CH2COPh), 66.6 (d, C-5Ј), 70.0 (t, C-6Ј), 71.3 (d, C-1Ј), 75.7 (d,
C-4Ј), 102.2 (d, CHPh), 127.1, 127.8 (d, C-3Ј), 128.5, 128.7,
128.9 (4 × d, Cortho and meta Ar), 129.2 (d, Cpara Ar), 130.7 (d, C-2Ј)
d, C-3 and C-5), 69.2 (t, C-6), 77.7 (d, C-4), 83.1 (t, C᎐CH ),
᎐
2
99.4 (d, C-2), 102.2 (d, CHPh), 127.1, 129.3 (2 × d, Cortho and meta
Ar), 128.5, (d, Cpara Ar), 138.5 (s, Cipso Ar), 146.4 (d, C-1), 159.4
(s, C᎐CH ); m/z (FIϩ) 274 (Mϩ, 100%). (HRMS calcd. for
᎐
2
C16H18O4 (Mϩ) 274.1205. Found: 274.1208) (Found: C, 70.15;
H, 6.62. C16H18O4 requires: C, 70.06: H, 6.61%).
Crystal data for 21b
C16H18O4, M = 274.32, orthorhombic, a = 5.8009(2), b =
13.1214(4), c = 18.5666(5) Å, U = 1413.2 Å3, T = 150 K, space
group P212121, Z = 4, µ(Mo–Kα) 0.092 mmϪ1, 8918 reflections
measured, 1887 unique (Rint = 0.031), R = 0.0289. The final wR
was 0.0319 (all data).
133.3 (d, Cpara Ar), 137.8, 138.9 (2 × s, Cipso Ar), 196.7 (s, C᎐O);
᎐
NOE experiment (500 MHz, C6D6): Irradiate δ 5.01 (H-1Ј),
enhancements: 2.52 (C(O)CHHЈ, 1.8%), 3.07 (C(O)CHHЈ,
1.4%), 3.60 (H-5Ј, 0.5%), 3.92 (H-4Ј, 0.9%), 5.53 (H-2Ј, 4.8%).
Irradiate δ 3.60 (H-5Ј), enhancements: 2.52 (C(O)CHHЈ, 2.6%),
3.07 (C(O)CHHЈ, 4.9%), 3.92 (H-4Ј, 1.2%), 4.07 (H-6Љ, 4.8%),
5.01 (H-1Ј, 0.6%), 5.33 (CHPh, 0.8%), 5.53 (H-2Ј, 0.3%), 5.94
(H-3Ј, 0.7%); m/z (FIϩ) 336 (Mϩ, 100%). (HRMS calcd. for
C21H20O4 (Mϩ) 336.1362. Found: 336.1358) (Found: C, 74.69;
H, 5.89. C21H20O4 requires: C, 74.98: H, 5.99%).
1,5-Anhydro-4,6-O-benzylidene-2-deoxy-3-O-(heptadec-1-en-2-
yl)-D-ribo-hex-1-enitol 21c
General method B: Tebbe reagent (4.2 ml, 2.12 mmol), ester 18c
(250 mg, 0.53 mmol) in tetrahydrofuran (10 ml) and pyridine
(2.5 ml), gave the enol ether 21c (234 mg, 94%) as a white crys-
talline solid; mp 61 ЊC; [α]2D5 ϩ158 (c, 1 in diethyl ether); νmax
(thin film): 1646, 1625 (w, 2 × C᎐C); δH (400 MHz, C6D6) 0.91
᎐
Data for diene 24
(3H, t, J 6.7 Hz, (CH2)14CH3), 1.24–1.30 (24H, m, (CH2)2-
(CH2)12CH3), 1.58–1.65 (2H, m, CH2CH2(CH2)12CH3), 2.13–
2.21 (2H, m, CH2(CH2)13CH3), 3.49 (1H, at, J 10.4 Hz, H-6),
3.52 (1H, dd, J3,4 3.8 Hz, J4,5 10.1 Hz, H-4), 4.00 (1H, d, Jgem 1.4
A white crystalline solid; mp 146–147 ЊC (diethyl ether); [α]2D5
Ϫ32 (c, 0.5 in CHCl3); νmax (KBr disc): 3410 (br, OH), 1659
(C᎐C), 1628, 1590 (2 × C᎐C) cmϪ1; δH (400 MHz, CDCl3) 2.51
᎐
᎐
Hz, C᎐CHHЈ), 4.06 (1H, d, C᎐CHHЈ), 4.24 (1H, dd, J 5.4
(1H, br s, OH), 3.67–3.74 (2H, m, H-7 and H-8), 4.26–4.30 (1H,
m, H-6), 4.32–4.39 (1H, m, H-8Ј), 5.59 (1H, s, CHPh), 6.45 (1H,
dd, J4,5 15.3 Hz, J5,6 5.5 Hz, H-5), 6.71 (1H, dd, J3,4 11.2 Hz,
H-4), 7.04 (1H, d, J2,3 15.1 Hz, H-2), 7.33–7.60 (4H, m, H-3 and
Ar–H), 7.89–7.95 (2H, m, Ar–H); δC (100.6 MHz, CDCl3) 65.6
(d, C-7), 71.1 (t, C-8), 81.6 (d, C-6), 101.0 (d, CHPh), 126.4 (d,
C-2), 126.2, 128.3, 128.4, 128.6 (4 × d, Cortho and meta Ar), 129.1 (d,
Cpara Ar), 130.6 (d, C-4) 132.9 (d, Cpara Ar), 137.4, 137.8 (2 × s,
Cipso Ar), 139.2 (d, C-5), 143.6 (d, C-3), 190.8 (s, C-1); m/z (FIϩ)
336 (Mϩ, 100%). (HRMS calcd. for C21H20O4 (Mϩ) 336.1362.
Found: 336.1369) (Found: C, 74.97; H, 5.75. C21H20O4 requires:
C, 74.98: H, 5.99%).
᎐
᎐
5,6Ј
Hz, J6,6Ј 10.4 Hz, H-6Ј), 4.39 (1H, ddd, J5,6 10.4 Hz, H-5), 4.42
(1H, dd, J2,3 5.8 Hz, H-3), 4.91 (1H, at, J 5.9 Hz, H-2), 5.28 (1H,
s, CHPh), 6.12 (1H, d, J1,2 6.1 Hz, H-1), 7.10–7.15 (1H, m,
Ar–H), 7.18–7.22 (2H, m, Ar–H), 7.61–7.63 (2H, m, Ar–H);
δC (100.6 MHz, C6D6) 14.7 (q, (CH2)14CH3), 23.4, 28.1, 29.7,
30.1, 30.2, 30.3, 30.4, 30.4, 30.5, 32.6 (10 × t, CH2(CH2)13CH3),
36.2 (t, CH2(CH2)13CH3), 65.3, 65.4 (2 × d, C-3 and C-5), 69.2
(t, C-6), 77.7 (d, C-4), 82.2 (t, C᎐CH ), 99.5 (d, C-2), 102.2 (d,
᎐
2
CHPh), 127.1, 128.5 (2 × d, Cortho and meta Ar), 129.3 (d, Cpara Ar),
138.6 (s, Cipso Ar), 146.4 (d, C-1), 163.0 (s, C᎐CH ); m/z (FIϩ)
᎐
2
470 (Mϩ, 100%). (HRMS calcd. for C30H46O4 (Mϩ) 470.3396.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3782

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1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-ꢁ-D-
erythro-hex-2Ј-enopyranosyl)propan-2-one 23b
diethyl ether, 4 : 1 ϩ1% triethylamine) indicated the complete
consumption of starting material (Rf 0.7) and the formation of
a mixture of products (Rf 0.28 and 0.34). The reaction mixture
was then concentrated in vacuo and the residue purified by flash
column chromatography (petrol : diethyl ether, 4 : 1) to obtain
two compounds (total yield 34 mg, 85%; ratio 23c : 26 = 1.3 : 1);
α-C-glycoside 23c as a white crystalline solid; mp 88–89 ЊC
(petrol); [α]2D5 ϩ21 (c, 0.5 in CHCl3); νmax (KBr disc): 1709 (s,
General method D: Enol ether 21b (40 mg, 0.15 mmol), in
anhydrous xylene (1 ml), gave α-C-glycoside 23b (39.4 mg, 99%)
as a white crystalline solid; mp 91–92 ЊC (petrol); [α]2D6 ϩ58 (c, 1
in CHCl3); νmax (KBr disc) 1704 (s, C᎐O) cmϪ1; δH (400 MHz,
᎐
C6D6) 1.60 (3H, s, CH3), 1.86 (1H, dd, J1Ј,C(O)CHHЈ 5.6 Hz, Jgem
16.3 Hz, C(O)CHHЈ), 2.30 (1H, dd, J1Ј,C(O)CHHЈ 8.2 Hz,
C(O)CHHЈ), 3.46 (1H, ddd, J4Ј,5Ј 7.8 Hz, J5Ј,6Ј 10.2 Hz, J5Ј,6Љ 4.1
Hz, H-5Ј), 3.53 (1H, at, J 10.0 Hz, H-6Ј), 3.87–3.90 (1H, m,
H-4Ј), 4.14 (1H, dd, J6Ј,6Љ 9.8 Hz, H-6Љ), 4.65–4.70 (1H, m,
H-1Ј), 5.33 (1H, s, CHPh), 5.35 (1H, dat, J2Ј,3Ј 10.4 Hz, J 2.6 Hz,
H-2Ј), 5.90 (1H, br d, J 10.4 Hz, H-3Ј), 7.10–7.21 (3H, m,
Ar–H), 7.63–7.66 (2H, m, Ar–H); δC (100.6 MHz, C6D6) 30.4
(q, CH3), 46.8 (t, CH2COCH3), 66.3 (d, C-5Ј), 70.0 (t, C-6Ј),
70.8 (d, C-1Ј), 75.6 (d, C-4Ј), 102.3 (d, CHPh), 127.1 (2 × d,
Cortho and meta Ar), 127.7 (d, C-3Ј), 128.5 (2 × d, Cortho and meta Ar),
129.3 (d, Cpara Ar), 130.4 (d, C-2Ј), 138.9 (s, Cipso Ar), 204.7 (s,
C᎐O) cmϪ1; δH (400 MHz, C6D6) 1.02 (3H, t, J 6.8 Hz, C(O)-
᎐
(CH2)14CH3), 1.30–1.52 (24H, m, C(O)CH2CH2(CH2)12CH3),
1.63 (2H, m, J 7.3 Hz, C(O)CH2CH2(CH2)12CH3), 2.07 (1H, dd,
J1Ј,
5.7 Hz, Jgem 16.2 Hz, CHHЈC(O)(CH2)14CH3), 2.10
CHHЈC(O)
(2H, t, J 7.4 Hz, CH2C(O)CH2(CH2)13CH3), 2.54 (1H, dd,
J1Ј, 8.3 Hz, CHHЈC(O)(CH2)14CH3), 3.62–3.70 (2H, m,
CHHЈC(O)
H-5Ј and H-6Ј), 4.01–4.04 (1H, m, H-4Ј), 4.26–4.34 (1H, m,
H-6Љ), 4.89–4.94 (1H, m, H-1Ј), 5.46 (1H, s, CHPh), 5.52 (1H,
dat, J2Ј,3Ј 10.4 Hz, J 2.6 Hz, H-2Ј), 6.04 (1H, br d, J 10.4 Hz,
H-3Ј), 7.21–7.32 (3H, m, Ar–H), 7.76–7.78 (2H, m, Ar–H);
δC (100.6 MHz, C6D6) 14.5 (q, C(O)(CH2)14CH3), 23.3, 24.0,
29.7, 30.0, 30.1, 30.1, 30.3, 30.4, 30.4, 30.4, 32.5 (11 × t, C(O)-
CH2(CH2)13CH3), 43.8(t, C(O)CH2(CH2)13CH3), 46.0(t, CH2C-
(O)(CH2)14CH3), 66.3 (d, C-5Ј), 70.0 (t, C-6Ј), 70.9 (d, C-1Ј),
C᎐O); NOE experiment (500 MHz, C D ): Irradiate δ 4.68
᎐
6
6
(H-1Ј), enhancements: 1.86 (C(O)CHHЈ, 1.4%), 2.30
(C(O)CHHЈ, 0.8%), 5.35 (H-2Ј, 3.1%). Irradiate δ 3.46 (H-5Ј),
enhancements: 1.86 (C(O)CHHЈ, 0.4%), 2.30 (C(O)CHHЈ,
1.2%), 4.14 (H-6Љ, 1.0%). Irradiate δ 2.30 (C(O)CHHЈ), enhance-
ments: 1.60 (CH3, 2.0%), 1.86 (C(O)CHHЈ, 21.1%), 3.46 (H-5Ј,
7.7%), 4.68 (H-1Ј, 1.9%). Irradiate δ 1.86 (C(O)CHHЈ),
enhancements: 2.30 (C(O)CHHЈ, 20.3%), 3.46 (H-5Ј, 2.0%),
4.68 (H-1Ј, 2.8%), 5.35 (H-2Ј, 1.6%); m/z (FIϩ) 274 (Mϩ, 100%).
(HRMS calcd. for C16H18O4 (M) 274.1205. Found: 274.1205)
(Found: C, 69.93; H, 6.60. C16H18O4 requires: C, 70.06: H,
6.61%).
75.5 (d, C-4Ј), 102.2 (d, CHPh), 127.0 (Cortho
Ar), 127.6
and meta
(d, C-3Ј), 128.5 (Cortho
Ar), 129.2 (d, Cpara Ar), 130.5 (d,
and meta
C-2Ј), 138.8 (s, Cipso Ar), 206.5 (s, C᎐O); NOE experiment (500
᎐
MHz, C6D6): Irradiate δ 4.92 (H-1Ј), enhancements: 2.07
(C(O)CHHЈ, 1.3%), 2.54 (C(O)CHHЈ, 0.4%), 5.52 (H-2Ј, 5.2%).
Irradiate δ 4.02 (H-4Ј), enhancements: 3.66 (H-5Ј and H-6Ј,
5.1%), 4.92 (H-1Ј, 1.3%), 5.46 (CHPh, 15.9%), 6.04 (H-3Ј,
4.1%). Irradiate δ 2.54 (CHHЈC(O)(CH2)14CH3), enhance-
ments: 2.08 (CH2C(O)CH2(CH2)13CH3 and C(O)CHHЈ,
26.6%), 3.66 (H-5Ј and H-6Ј, 6.5%), 4.92 (H-1Ј, 2.1%); m/z
(FIϩ) 470 (Mϩ, 100%). (HRMS calcd. for C30H46O4 (Mϩ)
470.3396. Found: 470.3416).
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-2Ј-methyl-
ꢁ-D-erythro-hex-2Ј-enopyranosyl)acetophenone 25
Together with methyl ketone 26 as a white foam; [α]2D5 ϩ5.8 (c,
General method D: Enol ether 22 (40 mg, 0.11 mmol) in
anhydrous xylene (1 ml), gave α-C-glycoside 25 (39 mg, 98%) as
a white crystalline solid; mp 117–118 ЊC (petrol–diethyl ether);
0.5 in CHCl3); νmax (thin film): 1697 (s, C᎐O) cmϪ1; δH (400
᎐
MHz, C6D6) 0.91 (3H, t, J 6.7 Hz, (CH2)13CH3), 1.06–1.31
(24H, m, CHCH2(CH2)12CH3), 1.56–1.64 (1H, m, CHHЈ-
(CH2)12CH3), 1.68–1.75 (1H, m, CHHЈ(CH2)12CH3), 1.78 (3H,
s, CHC(O)CH3), 2.57 (1H, m, CHC(O)CH3), 3.52–3.59 (2H, m,
H-5Ј and H-6Ј), 3.88–3.90 (1H, m, H-4Ј), 4.18–4.24 (1H, m,
H-6Љ), 4.45–4.49 (1H, m, H-1Ј), 5.34 (1H, s, CHPh), 5.50 (1H,
dat, J2Ј,3Ј 10.5 Hz, J 2.5 Hz, H-2Ј), 5.93 (1H, br d, J 10.4 Hz,
H-3Ј), 7.10–7.21 (3H, m, Ar–H), 7.64–7.66 (2H, m, Ar–H);
δC (100.6 MHz, C6D6) 14.7 (q, (CH2)13CH3), 23.4, 27.4, 30.0,
30.1, 30.3, 30.4, 30.5, 30.5, 30.7, 30.7 (10 × t, CH2(CH2)12CH3),
31.2 (q, CHC(O)CH3), 32.6 (t, C(H)CH2(CH2)12CH3), 56.0 (d,
CHC(O)CH3), 66.8 (d, C-5Ј), 70.0 (t, C-6Ј), 74.7 (d, C-1Ј), 75.8
[α]2D5 ϩ43.8 (c, 0.5 in CHCl3); νmax (KBr disc): 1676 (s, C᎐O),
᎐
1598 (w, C᎐C) cmϪ1; δH (400 MHz, C6D6) 1.39 (3H, s, CH3),
᎐
2.58 (1H, dd, J1Ј,C(O)CHHЈ 3.5 Hz, Jgem 15.7 Hz, C(O)CHHЈ), 3.25
(1H, dd, J1Ј,C(O)CHHЈ 9.4 Hz, C(O)CHHЈ), 3.58 (1H, at, J 10.2 Hz,
H-6Ј), 3.76 (1H, ddd, J4Ј,5Ј 8.2 Hz, J5Ј,6Ј 10.1 Hz, J5Ј,6Љ 4.1 Hz,
H-5Ј), 4.05–4.09 (1H, m, H-4Ј and H-6Љ), 5.01–5.03 (1H, m,
H-1Ј), 5.45 (1H, s, CHPh), 5.79 (1H, br s, H-3Ј), 7.12–7.16 (2H,
m, Ar–H), 7.20–7.32 (4H, m, Ar–H), 7.77–7.78 (2H, m, Ar–H),
7.88–7.90 (2H, m, Ar–H); δC (100.6 MHz, C6D6) 19.3 (q, CH3),
40.2 (t, CH2COPh), 66.6 (d, C-5Ј), 69.8 (t, C-6Ј), 74.8 (d, C-1Ј),
76.2 (d, C-4Ј), 102.0 (d, CHPh), 123.5 (d, C-3Ј), 127.0, 128.5,
(d, C-4Ј), 102.4 (d, CHPh), 127.1 (Cortho
Ar), 128.1 (d,
and meta
128.7, 128.9 (4 × d, Cortho
Ar), 129.1, 133.1 (2 × d, Cpara
and meta
C-3Ј), 128.6 (Cortho and meta Ar), 129.3 (d, Cpara Ar), 129.3 (d, C-2Ј),
138.8 (s, Cipso Ar), 208.9 (s, C᎐O); NOE experiment (500 MHz,
Ar), 137.6 (d, C-2Ј), 138.0, 139.0 (2 × s, Cipso Ar), 197.1 (s, C᎐O);
᎐
᎐
NOE experiment (500 MHz, C6D6): Irradiate δ 5.02 (H-1Ј),
enhancements: 1.39 (CH3, 3.5%), 2.58 (C(O)CHHЈ, 3.1%), 3.76
(H-5Ј, 0.8%), 4.07 (H-4Ј and H-6Љ, 0.9%), 5.79 (H-3Ј, 0.5%).
Irradiate δ 3.76 (H-5Ј), enhancements: 3.25 (C(O)CHHЈ, 8.1%),
4.07 (H-4Ј and H-6Љ, 5.1%), 5.02 (H-1Ј, 0.4%), 5.45 (CHPh,
0.2%), 5.79 (H-3Ј, 0.4%). Irradiate δ 3.25 (C(O)CHHЈ),
enhancements: 2.58 (C(O)CHHЈ, 26.0%), 3.76 (H-5Ј, 13.8%),
5.02 (H-1Ј, 1.1%). Irradiate δ 2.58 (C(O)CHHЈ), enhancements:
1.39 (CH3, 4.1%), 3.25 (C(O)CHHЈ, 23.7%), 5.02 (H-1Ј, 6.5%);
m/z (FIϩ) 350 (Mϩ, 100%). (HRMS calcd. for C22H22O4 (Mϩ)
350.1518. Found: 350.1512) (Found: C, 75.25; H, 6.47.
C22H22O4 requires: C, 75.41: H, 6.33%).
CDCl3): Irradiate
δ
4.47 (H-1Ј), enhancements: 2.57
(CHC(O)CH3, 1.2%), 5.50 (H-2Ј, 6.5%). Irradiate δ 3.89 (H-4Ј),
enhancements: 3.55 (H-5Ј and H-6Ј, 5.4%), 4.47 (H-1Ј, 1.0%),
5.34 (CHPh, 15.4%), 5.93 (H-3Ј, 5.0%). Irradiate δ 2.57
(CHC(O)CH3), enhancements: 3.55 (H-5Ј and H-6Ј, 6.7%), 4.47
(H-1Ј, 1.8%); m/z (FIϩ) 470 (Mϩ, 100%). (HRMS calcd. for
C30H46O4 (Mϩ) 470.3396. Found: 470.3386) (Found: C, 76.43;
H, 9.85. C30H46O4 requires: C, 76.55: H, 9.85%).
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-di(tert-butyl)silanediyl-2Ј,3Ј-dideoxy-
ꢁ-D-erythro-hex-2Ј-enopyranosyl)heptadecan-2-one 27
General method D: Enol ether 20 (40 mg, 0.08 mmol) in
anhydrous xylene (1 ml), after 4 h, gave α-C-glycoside 27 (39.2
mg, 98%) as a white foam; [α]2D5 ϩ8 (c, 1.0 in CHCl3); νmax (thin
1-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-ꢁ-D-
erythro-hex-2Ј-enopyranosyl)heptadecan-2-one 23c and 3-(1Ј,5Ј-
anhydro-4Ј,6Ј-O-benzylidene-2Ј,3Ј-dideoxy-ꢁ-D-erythro-hex-2Ј-
enopyranosyl)heptadecan-2-one 26
film) 1717 (s, C᎐O) cmϪ1; δH (400 MHz, C6D6) 0.91 (3H, t, J 6.7
᎐
Hz, C(O)(CH2)14CH3), 1.09, 1.13 (18H, 2 × s, 2 × C(CH3)3),
1.20–1.33 (24H, m, C(O)CH2CH2(CH2)12CH3), 1.50 (2H, m,
C(O)CH2CH2(CH2)12CH3), 1.98 (2H, t, J 7.3 Hz, C(O)CH2-
Enol ether 21c (40 mg, 0.08 mmol) was heated in anhydrous
xylene (1 ml), or benzene (1 ml), for 10 h, when TLC (petrol :
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3783

View Article Online
(CH2)13CH3), 2.07 (1H, dd, J1Ј,
5.9 Hz, Jgem 15.9 Hz,
mg, 3.49 mmol) and 4-dimethylaminopyridine (43 mg, 0.35
CHHЈC(O)
CHHЈC(O)(CH2)14CH3), 2.50 (1H, dd, J1Ј,
8.0 Hz,
mmol), in anhydrous dichloromethane (15 ml), gave ester 30
(947 mg, 91%) as a colourless oil; [α]2D3 Ϫ133 (c, 1 in CHCl3); νmax
(thin film) 1730 (s, C᎐O), 1648 (w, C᎐C) cmϪ1; δH (400 MHz,
CHHЈC(O)
CHHЈC(O)(CH2)14CH3), 3.62 (1H, ddd, J4Ј,5Ј 8.5 Hz, J5Ј,6Ј 10.2
Hz, J5Ј,6Љ 4.9 Hz, H-5Ј), 3.97 (1H, at, J 10.2 Hz, H-6Ј), 4.27 (1H,
dd, J6Ј,6Љ 10.0 Hz, H-6Љ), 4.44 (1H, dd, J3Ј,4Ј 1.6 Hz, H-4Ј), 4.74–
4.78 (1H, m, H-1Ј), 5.45 (1H, dat, J2,Ј3Ј 10.4 Hz, J 2.4 Hz, H-2Ј),
5.92 (1H, br d, J 10.4 Hz, H-3Ј); δC (100.6 MHz, C6D6) 14.7 (q,
C(O)(CH2)14CH3), 20.5, 23.2 (2 × s, 2 × C(CH3)3), 27.6, 28.0
(2 × q, 2 × C(CH3)3), 23.4, 24.1, 29.8, 30.1, 30.2, 30.2, 30.4, 30.4,
30.5, 30.5, 30.5, 32.6 (12 × t, C(O)CH2(CH2)13CH3), 43.6 (t,
C(O)CH2(CH2)13CH3), 46.3 (t, CH2C(O)(CH2)14CH3), 68.1 (t,
C-6Ј), 70.0 (d, C-5Ј), 70.6 (d, C-1Ј), 71.1 (d, C-4Ј), 129.2 (d, C-2Ј),
᎐
᎐
CDCl3) 0.99, 1.04 (18H, 2 × s, 2 × C(CH3)3), 1.33, 1.35, 1.45,
1.53 (12 H, 4 × s, 2 × C(CH3)2), 3.92 (1H, ddd, J4Ј,5Ј 9.9 Hz, J5Ј,6Ј
10.3 Hz, J5Ј,6Љ 4.6 Hz, H-5Ј), 3.98 (1H, at, J 10.0 Hz, H-6Ј), 4.19
(1H, dd, J6Ј,6Љ 9.7 Hz, H-6Љ), 4.21 (1H, dd, J3Ј,4Ј 8.0 Hz, H-4Ј),
4.39 (1H, dd, J1,2 5.0 Hz, J2,3 2.7 Hz, H-2), 4.48 (1H, d, J4,5 2.2
Hz, H-5), 4.58 (1H, dd, J3,4 7.7 Hz, H-4), 4.67 (1H, dd, H-3),
4.77 (1H, dd, J1Ј,2Ј 6.0 Hz, J2Ј,3Ј 2.1 Hz, H-2Ј), 5.53 (1H, dat, J 1.7
and 7.6 Hz, H-3Ј), 5.68 (1H, d, H-1), 6.32 (1H, dd, H-1Ј); δC
(100.6 MHz, CDCl3) 19.8, 22.6 (2 × s, 2 × C(CH3)3), 24.8, 24.9,
25.8, 26.0 (4 × q, 2 × C(CH3)2), 26.8, 27.3 (2 × q, 2 × C(CH3)3),
65.7 (t, C-6Ј), 68.5 (d, C-5), 70.2 (d, C-2), 70.7 (d, C-3), 72.1 (d,
C-4), 72.8 (d, C-5Ј), 73.0 (d, C-3Ј), 73.4 (d, C-4Ј), 96.5 (d, C-1),
100.3 (d, C-2Ј), 109.0, 110.1 (2 × s, 2 × C(CH3)2), 144.9 (d, C-
130.9 (d, C-3Ј), 206.6 (s, C᎐O); NOE experiment (500 MHz,
᎐
C6D6): Irradiate δ 4.76 (H-1Ј), enhancements: 1.98 (CH2C(O)-
CH2(CH2)13CH3, 1.3%), 2.07 (CHHЈC(O)(CH2)14CH3, 2.1%),
2.50 (CHHЈC(O)(CH2)14CH3, 1.6%), 3.62 (H-5Ј, 0.7%), 3.97
(H-6Ј, 0.3%), 4.44 (H-4Ј, 0.6%), 5.45 (H-2Ј, 5.9%). Irradiate δ 3.62
(H-5Ј), enhancements: 1.98 (CH2C(O)CH2(CH2)13CH3, 0.5%),
2.07 (CHHЈC(O)(CH2)14CH3, 2.3%), 2.50 (CHHЈC(O)(CH2)14-
CH3, 4.4%), 4.27 (H-6Љ, 4.2%), 4.44 (H-4Ј, 2.2%), 4.76 (H-1Ј,
0.9%), 5.45 (H-2Ј, 0.5%), 5.92 (H-3Ј, 1.1%). Irradiate δ 2.50
(CHHЈC(O)(CH2)14CH3), enhancements: 1.98 (CH2C(O)CH2-
(CH2)13CH3, 2.7%), 2.07 (CHHЈC(O)(CH2)14CH3, 23.1%), 3.62
(H-5Ј, 6.4%), 4.76 (H-1Ј, 2.9%), 5.45 (H-2Ј, 0.3%), 5.92 (H-3Ј,
0.3%). Irradiate δ 2.07 (CHHЈC(O)(CH2)14CH3), enhancements:
2.50 (CHHЈC(O)(CH2)14CH3, 22.6%), 3.62 (H-5Ј, 3.3%), 4.76
(H-1Ј, 4.6%), 5.45 (H-2Ј, 4.0%); m/z (FIϩ) 522 (Mϩ, 100%).
(HRMS calcd. for C31H58O4Si (Mϩ) 522.4104. Found: 522.4107)
(Found: C, 71.32; H, 11.16. C31H58O4Si requires: C, 71.21: H,
11.18%).
1Ј), 167.8 (s, C᎐O); m/z (FIϩ) 542 (Mϩ, 100%). (HRMS calcd.
᎐
for C26H42O10Si (Mϩ) 542.2547. Found 542.2568) (Found: C,
57.68; H, 7.73. C26H42O10Si requires C, 57.54; H, 7.80%).
6-O-(1Ј,5Ј-Anhydro-2Ј-deoxy-4Ј,6Ј-O-di(tert-butyl)silanediyl-D-
arabino-hex-1Ј-en-3Ј-yl)-7-deoxy-l,2:3,4-di-O-isopropylidene-ꢁ-
D-galacto-hept-6-enopyranose 31
General method B: Tebbe reagent (1.48 ml, 0.74 mmol), ester 30
(50 mg, 0.09 mmol) in tetrahydrofuran (2 ml) and pyridine
(0.5 ml), after 48 h, gave enol ether 31 (27 mg, 54%, 72% yield
over recovered starting material) as a colourless oil; [α]2D4 Ϫ105
(c, 1 in CHCl3); νmax (thin film): 1646 (m, C᎐C) cmϪ1; δH (400
᎐
MHz, C6D6) 0.98, 1.02 (18H, 2 × s, 2 × C(CH3)3), 1.01, 1.20,
1.32, 1.52 (12H, 4 × s, 2 × C(CH3)2), 3.79 (1H, ddd, J4Ј,5Ј 10.3
Hz, J5Ј,6Ј 10.4 Hz, J5Ј,6Љ 5.0 Hz, H-5Ј), 3.93 (1H, at, J 10.3 Hz,
H-6Ј), 4.13 (1H, dd, J6Ј,6Љ 10.3 Hz, H-6Љ), 4.19 (1H, dd, J1,2
5.0 Hz, J2,3 2.3 Hz, H-2), 4.34 (1H, dd, J3Ј,4Ј 7.3 Hz, H-4Ј), 4.55
(1H, d, J4,5 2.0 Hz, H-5), 4.56 (1H, dd, J3,4 7.7 Hz, H-3), 4.60
3-(1Ј,5Ј-anhydro-4Ј,6Ј-O-di(tert-butyl)silanediyl-2Ј,3Ј-dideoxy-
ꢁ-D-erythro-hex-2Ј-enopyranosyl)heptadecan-2-one 28
General method D: Enol ether 20 (40 mg, 0.08 mmol), in deuter-
ated benzene (1 ml), after 7 h at 195 ЊC, gave a mixture of two
products (Rf 0.51 and 0.46, 37.5 mg, 94%; 27 : 28 = 1.4 : 1);
α-C-glycoside 27 as a white foam identical to the compound pre-
viously above, and methyl ketone 28 as a colourless oil; [α]2D5 Ϫ11
(1H, dd, H-4), 4.62 (1H, d, Jgem 1.0 Hz, C᎐CHHЈ) 4.78 (1H, dat,
᎐
J 2.0 and 7.3 Hz, H-3Ј), 4.97 (1H, d, C᎐CHHЈ) 5.02 (1H, dd,
᎐
J1Ј,2Ј 6.1 Hz, J2Ј,3Ј 1.8 Hz, H-2Ј), 5.59 (1H, d, H-1), 6.06 (1H, dd,
J1Ј,3Ј 1.4 Hz, H-1Ј); δC (100.6 MHz, C6D6) 20.2, 23.1 (2 × s, 2 ×
C(CH3)3), 25.1, 25.2, 26.2, 26.7 (4 × q, 2 × C(CH3)2), 27.4, 27.8
(2 × q, 2 × C(CH3)3), 66.6 (t, C-6Ј), 68.3 (d, C-4), 71.6 (d, C-2),
71.8 (d, C-5), 72.3 (d, C-3), 73.5 (d, C-5Ј), 75.5 (d, C-4Ј), 76.7 (d,
(c, 1.0 in CHCl3); νmax (thin film): 1713 (s, C᎐O) cmϪ1; δH (400
᎐
MHz, C6D6) 1.03 (3H, t, J 6.8 Hz, (CH2)13CH3), 1.20, 1.24 (18H,
2 × s, 2 × C(CH3)3), 1.26–1.43 (24H, m, CHCH2(CH2)12CH3),
1.71–1.79 (1H, m, CHHЈ(CH2)12CH3), 1.84 (3H, s, CHC(O)CH3),
1.83–1.98 (1H, m, CHHЈ(CH2)12CH3), 2.84 (1H, ddd, J 3.8 and
8.8 Hz, CHC(O)CH3), 3.75 (1H, ddd, J4Ј,5Ј 8.2 Hz, J5Ј,6Ј 10.2 Hz,
J5Ј,6Љ 4.9 Hz, H-5Ј), 4.09 (1H, at, J 10.2 Hz, H-6Ј), 4.42 (1H, dd,
J6Ј,6Љ 10.0 Hz, H-6Љ), 4.54–4.58 (2H, m, H-1Ј and H-4Ј), 5.63 (1H,
dat, J2Ј,3Ј 10.5 Hz, J 2.0 Hz, H-2Ј), 6.05 (1H, br d, J 10.4 Hz,
H-3Ј); δC (100.6 MHz, C6D6) 14.5 (q, (CH2)13CH3), 20.4, 23.0 (2 ×
s, 2 × C(CH3)3), 27.5, 27.9 (2 × q, 2 × C(CH3)3), 23.3, 27.4, 29.7,
29.9, 30.0, 30.2, 30.3, 30.3 (8 × t, CH2(CH2)12CH3), 30.8 (q,
CHC(O)CH3), 32.5 (t, C(H)CH2(CH2)12CH3), 56.3 (d, CHC(O)-
CH3), 68.0 (t, C-6Ј), 70.4 (d, C-5Ј), 71.1 (d, C-4Ј), 74.2 (d, C-1Ј),
C-3Ј), 85.4 (t, C᎐CH ), 97.5 (d, C-1), 101.6 (d, C-2Ј), 108.9,
᎐
2
109.7 (2 × s, 2 × C(CH ) ), 144.4 (d, C-1Ј), 158.4 (s, C᎐CH );
᎐
3
2
2
m/z (CIϩ) 541 (MHϩ, 42%), (FIϩ) 540 (Mϩ, 100%). (HRMS
calcd. for C27H44O9Si (Mϩ) 540.2755. Found 540.2747) (Found
C, 59.84; H, 8.31. C27H44O9Si requires C, 59.97; H, 8.20%).
7-(1Ј,5Ј-Anhydro-4Ј,6Ј-O-di(tert-butyl)silanediyl-2Ј,3Ј-dideoxy-
ꢀ-D-erythro-hex-2Ј-enopyranosyl)-7-deoxy-l,2:3,4-di-O-isopro-
pylidene-ꢁ-D-galacto-heptanopyranos-6-ulose 32
General method C: Enol ether 31 (25 mg, 0.05 mmol), in tri-
butylamine (0.5 ml), gave β-C-glycoside 32 (14 mg, 56%) as a
white foam; [α]2D3 Ϫ46 (c, 1 in CHCl3); νmax (thin film): 1722 (m,
127.8 (d, C-2Ј), 131.3 (d, C-3Ј), 208.4 (s, C᎐O); NOE experiment
᎐
(500 MHz, CDCl3): Irradiate δ 4.40 (H-4Ј), enhancements: 2.25
(CHC(O)CH3, 2.0%), 2.89 (CHC(O)CH3, 0.9%), 3.45 (H-5Ј,
2.0%), 3.89 (H-6Ј, 3.9%), 5.97 (H-3Ј, 5.3%). Irradiate δ 4.35
(H-1Ј), enhancements: 2.25 (CHC(O)CH3, 0.6%), 2.89 (CHC(O)-
CH3, 2.0%), 5.63 (H-2Ј, 8.4%). Irradiate δ 3.45 (H-5Ј), enhance-
ments: 2.25 (CHC(O)CH3, 0.7%), 2.89 (CHC(O)CH3, 9.0%), 4.17
(H-6Љ, 4.8%), 4.40 (H-4Ј, 3.6%). Irradiate δ 2.89 (CHC(O)CH3),
enhancements: 2.25 (CHC(O)CH3, 4.7%), 3.45 (H-5Ј, 10.6%),
5.63 (H-2Ј, 2.4%); m/z (FIϩ) 522 (Mϩ, 100%). (HRMS calcd. for
C31H58O4Si (Mϩ) 522.4104. Found: 522.4113).
C᎐O) cmϪ1; δH (400 MHz, C6D6) 0.95, 1.02 (6H, 2 × s,
᎐
C(CH3)2), 1.07, 1.07 (18H, 2 × s, 2 × C(CH3)3), 1.21, 1.37 (6H, 2
× s, C(CH3)2), 2.81 (1H, dd, J1Ј,CHHЈC(O) 6.7 Hz, Jgem 18.3 Hz,
CHHЈC(O)), 3.31 (1H, dd, J1Ј, CHHЈC(O) 6.6 Hz, CHHЈC(O)), 3.60
(1H, ddd, J4Ј,5Ј 8.5 Hz, J5Ј,6Ј 10.5 Hz, J5Ј,6Љ 5.1 Hz, H-5Ј), 3.89
(1H, at, J 10.2 Hz, H-6Ј), 4.06 (1H, dd, J1,2 5.0 Hz, J2,3 2.4 Hz,
H-2), 4.19 (1H, dd, J6Ј,6Љ 10.0 Hz, H-6Љ), 4.35 (1H, dd, J3,4 7.9
Hz, H-3), 4.35 (1H, d, J4,5 2.0 Hz, H-5), 4.46 (1H, dd, H-4), 4.48
(1H, m, J 1.9 Hz and 8.4 Hz, H-4Ј), 4.84–4.89 (1H, m, H-1Ј),
5.45 (1H, d, H-1) 5.62 (1H, dat, J 1.9 Hz, J2Ј,3Ј 10.4 Hz, H-2Ј),
5.87 (1H, dat, J 1.9 and 10.4 Hz, H-3Ј); δC (100.6 MHz, C6D6)
20.5, 23.1 (2 × s, 2 × C(CH3)3), 24.3, 24.9, 26.2, 26.3 (4 × q, 2 ×
C(CH3)2), 27.7, 28.0 (2 × q, 2 × C(CH3)3), 46.1 (t, CHHЈC(O)),
67.9 (t, C-6Ј), 71.1 (d, C-2), 71.1 (d, C-4Ј), 71.2 (d, C-3), 71.6 (d,
C-1Ј), 73.2 (d, C-4), 74.5 (d, C-5), 75.5 (d, C-5Ј), 97.1 (d, C-1),
6-O-(1Ј,5Ј-Anhydro-2Ј-deoxy-4Ј,6Ј-O-di(tert-butyl)silanediyl-D-
arabino-hex-1Ј-en-3Ј-yl)-l,2:3,4-di-O-isopropylidene-ꢁ-D-galac-
turonic ester 30
General method A: Glycal 5 (500 mg, 1.74 mmol), galacturonic
acid 29 (957 mg, 3.49 mmol), dicyclohexylcarbodiimide (720
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3784

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109.0, 109.7 (2 × s, 2 × C(CH3)2), 130.1 (d, C-2Ј), 130.3 (d,
C-3Ј), 206.0 (s, C᎐O); NOE experiment (500 MHz, C D ):
(CH2)2NHBoc), 2.00 (1H, dd, J1Ј,CHHЈC(O) 5.5 Hz, Jgem 16.0 Hz,
CHHЈC(O)), 2.33 (1H, dd, J1Ј,CHHC(O)Ј 7.8 Hz, CHHЈC(O)),
2.82–2.93 (2H, m, (CH2)2CH2NHBoc), 3.56 (1H, ddd, J4Ј,5Ј
8.5 Hz, J5,Ј6Ј 10.4 Hz, J5Ј,6Љ 5.0 Hz, H-5Ј), 3.92 (1H, at, J6Ј,6Љ
10.2 Hz, H-6Ј), 4.10 (1H, br s, NH), 4.20 (1H, dd, J6Ј,6Љ 9.9 Hz,
H-6Љ), 4.51 (1H, dd, J3Ј,4Ј 1.2 Hz, H-4Ј), 4.57–4.60 (1H, m,
H-1Ј), 5.37 (1H, dat, J 1.8 Hz, J2Ј,3Ј 10.4 Hz, H-2Ј), 5.89 (1H, br
d, J 10.3 Hz, H-3Ј); δC (100.6 MHz, C6D6) 20.6, 23.2 (2 × s, 2 ×
C(CH3)3), 24.3 (t, CH2CH2CH2NHBoc), 27.6, 28.0, 28.8 (3 × q,
3 × C(CH3)3), 40.2 (t, (CH2)2CH2NHBoc), 40.7 (t, CH2(CH2)2-
NHBoc), 48.1 (t, CH2C(O)), 67.8 (t, C-6Ј), 71.1 (d, C-4Ј), 72.6
(d, C-1Ј), 75.5 (d, C-5Ј), 78.8 (s, OC(CH3)3), 129.7 (d, C-2Ј),
᎐
6
6
Irradiate δ 4.87 (H-1Ј), enhancements: 2.81 (CHHЈC(O), 2.7%),
3.31 (CHHЈC(O), 2.8%), 3.60 (H-5Ј, 9.6%), 5.62 (H-2Ј, 5.9%).
Irradiate δ 3.60 (H-5Ј), enhancement 4.19 (H-6Љ, 4.5%), 4.48
(H-4Ј, 2.1%), 4.87 (H-1Ј, 10.8%); m/z (APCIϩ) 541 (MHϩ,
100%). (HRMS calcd. for C27H45O9Si (MHϩ) 541.2831. Found
541.2832) (Found C, 60.20; H, 8.08. C27H44O9Si requires C,
59.97; H, 8.20%).
3-O-(4-tert-Butoxycarbonylaminobutanoyl)-1,5-anhydro-2-
deoxy-4,6-O-di(tert-butyl)silanediyl-D-arabino-hex-1-enitol 33
130.6 (d, C-3Ј), 156.2 (s, CO C(CH ) ), 206.4 (s, C᎐O); NOE
᎐
2
3 3
General method A: Glycal 5 (250 mg, 0.87 mmol), 4-tert-butoxy-
carbonylaminobutyric acid (355 mg, 1.75 mmol), dicyclo-
hexylcarbodiimide (360 mg, 1.75 mmol) and 4-dimethylamino-
pyridine (21 mg, 0.17 mmol), in anhydrous dichloromethane
(8 ml), gave ester 33 (388 mg, 94%) as a colourless oil; [α]2D2 Ϫ64 (c,
1 in CHCl3); νmax (thin film) 3374 (br, N–H), 1739, 1717 (s, 2 ×
C᎐O), 1648 (m, C᎐C) cmϪ1; δH (400 MHz, CDCl3) 0.92, 1.00, 1.38
(27H, 3 × s, 3 × C(CH3)3), 1.76–1.83 (2H, m, O2CCH2CH2CH2-
NHBoc), 2.29–2.41 (2H, m, O2CCH2(CH2)2NHBoc), 3.05–3.15
(2H, m, O2C(CH2)2CH2NHBoc), 3.86 (1H, ddd, J4,5 9.8 Hz, J5,6
10.3 Hz, J5,6Ј 4.6 Hz, H-5), 3.92 (1H, at, J 10.0 Hz, H-6), 4.10 (1H,
dd, J3,4 7.8 Hz, H-4), 4.13 (1H, dd, J6,6Ј 9.7 Hz, H-6Ј), 4.67 (1H,
dd, J1,2 6.1 Hz, J2,3 1.8 Hz, H-2), 4.80 (1H, br s, NH), 5.33 (1H, br
d, J 7.6 Hz, H-3), 6.26 (1H, dd, J1,3 1.4 Hz, H-1); δC (100.6 MHz,
CDCl3) 19.7, 22.6 (2 × s, 2 × C(CH3)3), 25.3 (t, O2CCH2-
CH2CH2NHBoc), 26.7, 27.3, 28.3 (3 × q, 3 × C(CH3)3), 31.7 (t,
O2CCH2(CH2)2NHBoc), 39.6 (t, O2C(CH2)2CH2NHBoc), 65.6
(t, C-6), 72.1, 72.7, 73.6 (3 × d, C-3, C-4 and C-5), 79.0 (s,
OC(CH3)3), 100.4 (d, C-2), 144.9 (d, C-1), 155.8 (s, NCO2), 173.1
(s, O2C(CH2)3); m/z (CIϩ) 472 (MHϩ, 4%). (Found C, 58.80; H,
8.66; N, 2.95. C23H41N1O7Si1 requires C, 58.57; H, 8.76; N,
2.97%).
experiment (500 MHz, C6D6): Irradiate δ 4.59 (H-1Ј), enhance-
ments: 2.00 (CHHЈC(O), 2.9%), 2.33 (CHHЈC(O), 2.0%), 3.56
(H-5Ј, 9.9%), 5.37 (H-2Ј, 5.2%). Irradiate δ 4.51 (H-4Ј),
enhancements: 3.56 (H-5Ј, 1.9%), 3.92 (H-6Ј, 3.4%), 5.89
(H-3Ј, 4.2%). Irradiate δ 3.56 (H-5Ј), enhancements: 4.20 (H-6Љ,
4.1%), 4.51 (H-4Ј, 2.0%), 4.59 (H-1Ј, 10.1%). Irradiate 2.33
(CHHЈC(O)), enhancements: 2.00 (CHHЈC(O), 28.2%), 4.59
(H-1Ј, 3.1%); m/z (ESϩ) 470 (MHϩ, 90), 487 (MNH4ϩ, 77), 492
(MNaϩ, 100), 508 (MKϩ, 30%). (HRMS calcd. for C24H44-
O6NSi (MHϩ) 470.2938. Found 470.2938) (Found C, 61.37;
H, 9.26; N, 3.00. C24H43O6NSi requires C, 61.37; H, 9.24; N,
2.98%).
᎐
᎐
3-O-(4-Butoxycarbonylaminobutanoyl)-1,5-anhydro-4,6-O-
benzylidene-2-deoxy-D-ribo-hex-1-enitol 36
General method A: Glycal 15 (500 mg, 2.13 mmol), 4-tert-
butoxycarbonylaminobutyric acid (868 mg, 4.27 mmol), dicyclo-
hexylcarbodiimide (881 mg, 4.27 mmol) and 4-dimethyl-
aminopyridine (52 mg, 0.43 mmol), in anhydrous dichloro-
methane (15 ml), gave ester 36 (826 mg, 92%) as a white crystal-
line solid; mp 106–107 ЊC (petrol–diethyl ether); [α]2D4 ϩ201 (c, 1
in CHCl3); νmax (thin film) 3379 (br, N–H), 1733, 1711 (s, 2 ×
C᎐O), 1637 (m, C᎐C) cmϪ1; δH (400 MHz, CDCl3) 1.43 (9H, s,
᎐
᎐
3-O-(5-tert-Butoxycarbonylaminopent-1-en-2-yl)-1,5-anhydro-2-
deoxy-4,6-O-di(tert-butyl)silanediyl-D-arabino-hex-1-enitol 34
C(CH3)3), 1.75–1.81 (2H, m, CH2CH2CH2NHBoc), 2.36–2.40
(2H, m, CH2(CH2)2NHBoc), 3.06–3.11 (2H, m, O2C(CH2)2-
CH2NHBoc), 3.85 (1H, at, J 10.4 Hz, H-6), 4.00 (1H, dd, J3,4
4.0 Hz, J4,5 10.5 Hz, H-4), 4.17 (1H, ddd, J5,6 10.4 Hz, J5,6Ј
5.2 Hz, H-5), 4.48 (1H, dd, J6,6Ј 10.6 Hz, H-6Ј), 4.52 (1H, br s,
NH), 5.01 (1H, at, J 6.0 Hz, H-2), 5.46 (1H, dd, J2,3 5.8 Hz,
H-3), 5.62 (1H, s, CHPh), 6.51 (1H, d, J1,2 6.0 Hz, H-1), 7.36–
7.39 (3H, m, Ar–H), 7.45–7.47 (2H, m, Ar–H); δC (100.6 MHz,
CDCl3) 25.3 (t, CH2CH2CH2NHBoc), 28.0 (q, C(CH3)3), 31.8
(t, CH2(CH2)2NHBoc), 39.7 (t, (CH2)2CH2NHBoc), 61.9 (d,
C-3), 64.9 (d, C-5), 68.5 (t, C-6), 76.0 (d, C-4), 79.0 (s,
OC(CH3)3), 98.3 (d, C-2), 101.4 (d, CHPh), 126.0, 128.3 (2 × d,
Cortho and meta Ar), 129.2 (d, Cpara Ar), 136.9 (s, Cipso Ar), 147.5 (d,
C-1), 155.9 (s, NCO2), 172.8 (s, O2C(CH2)3); m/z (CIϩ) 420
(MHϩ, 21%), 437 (MNH4ϩ, 6%). (Found C, 63.10; H, 6.98; N,
3.35. C22H29O7N requires C, 62.99; H, 6.97; N, 3.34%).
General method B: Tebbe reagent (0.85 ml, 0.42 mmol), ester 33
(50 mg, 0.11 mmol) in tetrahydrofuran (2 ml) and pyridine
(0.5 ml), gave enol ether 34 (54 mg) as a yellow oil. This
unstable compound was used in the next step with out further
purification; νmax (thin film) 3367 (br, N–H), 1716 (s, C᎐O),
᎐
1652, 1645 (w, 2 × C᎐C) cmϪ1; δH (400 MHz, C6D6) 0.99, 1.04,
᎐
1.45 (27H, 3 × s, 3 × C(CH3)3), 1.48–1.66 (2H, m, CH2CH2-
CH2NHBoc), 2.00 (2H, t, J 7.1 Hz, CH2(CH2)2NHBoc), 3.08–
3.13 (2H, m, (CH2)2CH2NHBoc), 3.79 (1H, ddd, J4,5 10.3 Hz,
J5,6 10.4 Hz, J5,6Ј 5.0 Hz, H-5), 3.86–3.91 (1H, m, H-6), 3.92
(1H, s, C᎐CHHЈ), 3.94 (1H, s, C᎐CHHЈ), 4.12 (1H, dd, J6,6Ј 10.3
᎐
᎐
Hz, H-6Ј), 4.24 (1H, dd, J3,4 7.4 Hz, H-4), 4.37 (1H, br s, N–H),
4.57 (1H, br d, J 7.3 Hz, H-3), 4.83 (1H, dd, J1,2 6.1 Hz, J2,3 1.6
Hz, H-2), 6.03 (1H, dd, J1,3 0.9 Hz, H-1); δC (100.6 MHz, C6D6)
20.2, 23.1 (2 × s, 2 × C(CH3)3), 27.4, 27.9, (2 × q, 2 × C(CH3)3),
28.2 (t, CH2CH2CH2NHBoc), 28.8 (q, C(CH3)3), 32.9 (t,
CH2(CH2)2NHBoc), 40.2 (t, (CH2)2CH2NHBoc), 66.5 (t, C-6),
73.3, 75.1, 75.4 (3 × d, C-3, C-4 and C-5), 78.5 (s, OC(CH3)3),
3-O-(5-tert-Butoxycarbonylaminopent-1-en-2-yl)-1,5-anhydro-
4,6-O-benzylidene-2-deoxy-D-ribo-hex-1-enitol 37
General method B: Tebbe reagent (0.95 ml, 0.95 mmol), ester 36
(100 mg, 0.24 mmol), in tetrahydrofuran (4 ml) and pyridine (1
ml), gave enol ether 37 (93 mg, 93%) as a white crystalline solid;
mp 88 ЊC; [α]2D5 ϩ187.5 (c, 1 in CHCl3); νmax (thin film): 3380 (br,
NH), 1711 (s, C᎐O), 1634 (m, C᎐C) cmϪ1; δH (400 MHz, C6D6)
83.3 (t, C᎐CH ), 100.5 (d, C-2), 144.6 (d, C-1), 156.0 (s, NCO ),
᎐
᎐
2
2
161.8 (s, C᎐CH ); m/z (ESϩ) 470 (MHϩ, 2), 492 (MNaϩ, 30), 508
2
(MKϩ, 3%).
᎐
᎐
1-(1Ј,5Ј-Anhydro-2Ј,3Ј-dideoxy-4Ј,6Ј-O-di(tert-butyl)silanediyl-
ꢀ-D-erythro-hex-2Ј-enopyranosyl)-5-tert-butoxycarbonylamino-
pentan-2-one 35
1.41 (9H, s, C(CH3)3), 1.48–1.61 (2H, m, CH2CH2CH2NHBoc),
1.92–2.01 (2H, m, CH2(CH2)2NHBoc), 2.97–3.02 (2H, m,
(CH2)2CH2NHBoc), 3.46–3.53 (2H, m, H-4 and H-6), 3.90 (2H,
General method C: Crude enol ether 34 (54 mg), in tributyl-
amine (1 ml), gave β-C-glycoside 35 (34 mg, 69% over two steps)
as a colourless oil; [α]2D5 ϩ7.8 (c, 0.5 in CHCl3); νmax (thin film):
d, J 5.7 Hz, C᎐CH ), 4.21–4.33 (3H, m, H-3, H-5 and H-6Ј),
᎐
2
4.40 (1H, br s, NH), 4.86 (1H, at, J 5.8 Hz, H-2), 5.28 (1H, s,
CHPh), 6.13 (1H, d, J1,2 6.1 Hz, H-1), 7.10–7.15 (1H, m, Ar–H),
7.18–7.22 (2H, m, Ar–H), 7.54–7.56 (2H, m, Ar–H); δC (100.6
MHz, C6D6) 28.1 (t, CH2CH2CH2NHBoc), 28.8 (q, C(CH3)3),
33.2 (t, CH2(CH2)2NHBoc), 40.3 (t, (CH2)2CH2NHBoc), 65.3,
3370 (br, NH), 1715 (s, br, 2 × C᎐O) cmϪ1; δH (400 MHz, C6D6)
᎐
1.09 (18H, s, 2 × C(CH3)3), 1.34–1.49 (2H, m, CH2CH2CH2-
NHBoc), 1.43 (9H, s, C(CH3)3), 1.92 (2H, t, J 7.2 Hz, CH2-
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3785

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4 For a recent review see: P. Sears and C.-H. Wong, Angew. Chem.,
Int. Ed., 1999, 38, 2300–2324.
5 (a) A. Varki, Glycobiology, 1993, 3, 97–130; (b) R. A. Dwek, Chem.
Rev., 1996, 96, 683–720.
6 For leading references on conformational comparisons between
O- and C-glycosides see: (a) J. Jimenez-Barbero, J. F. Espinosa,
J. L. Asensio, F. J. Canada and A. Poveda, Adv. Carbohydr. Chem.
Biochem., 2001, 56, 235–284; (b) D. J. O’Leary and Y. Kishi, J. Org.
Chem., 1994, 59, 6629–6636 and references contained therein.
7 W. B. Motherwell, M. J. Tozer and B. C. Ross, J. Chem. Soc., Chem.
Commun., 1989, 1437–1439.
65.3 (2 × d, C-3 and C-5), 69.1 (t, C-6), 77.5 (d, C-4), 78.3 (s,
OC(CH ) ), 82.8 (t, C᎐CH ), 99.3 (d, C-2), 102.1 (d, CHPh),
127.0, 128.6 (2 × d, Cortho and meta Ar), 129.4 (d, Cpara Ar), 138.4 (s,
᎐
3
3
2
Cipso Ar), 146.5 (d, C-1), 156.1 (s, NCO ), 162.0 (s, C᎐CH ); m/z
᎐
2
2
(FIϩ) 417 (Mϩ, 100%). (HRMS calcd. for C23H31O6N (Mϩ)
417.2151. Found 417.2157) (Found C, 65.99; H, 7.49; N, 3.35.
C23H31O6N requires C, 66.17; H, 7.48; N, 3.35%).
3-O-(N-tert-Butoxycarbonyl-L-alanyl)-4,6-O-di-tert-butyl-
silanediyl-D-arabino-hex-1-enitol 38
8 For alternative approaches to C-glycosides by Claisen rearrange-
ment see: (a) R. E. Ireland, C. S. Wilcox, S. Thaisrivongs and
R. Vanier, Can. J. Chem., 1979, 57, 1743–1745; (b) B. Fraser-Reid,
R. D. Dawe and D. B. Tulshian, Can. J. Chem., 1979, 57, 1746–1749;
(c) R. E. Ireland, P. G. M. Wuts and B. Ernst, J. Am. Chem. Soc.,
1981, 103, 3205–3207; (d ) R. E. Ireland, R. C. Anderson,
R. Badoub, B. J. Fitzsimmons, G. McGarvey, S. Thaisrivongs and
C. S. Wilcox, J. Am. Chem. Soc., 1983, 105, 1988–2006; (e) D. B.
Tulshian and B. Fraser-Reid, J. Org. Chem., 1984, 49, 518–522;
( f ) D. P. Curran and Y. G. Suh, Carbohydr. Res., 1987, 111, 161–191;
(g) L. Colombo, G. Casiraghi, A. Pittalis and G. Rassu, J. Org.
Chem., 1991, 56, 3897–3900; (h) T. Vidal, A. Haudrechy and
Y. Langlois, Tetrahedron Lett., 1999, 40, 5677–5680; (i) G. A.
Wallace, R. W. Scott and C. H. Heathcock, J. Org. Chem., 2000, 65,
4145–4152.
General method A: Glycal 5 (1.011 g, 3.53 mmol), N-tert-
butoxycarbonyl--alanine (0.868 g, 4.59 mmol), dimethyl-
aminopyridine (86 mg, 0.71 mmol) and dicyclohexylcarbo-
diimide (1.46 g, 7.06 mmol), in dichloromethane (40 ml), gave
ester 38 (1.6479 g, quant.) as a colourless oil; [α]2D5 Ϫ65.4 (c, 0.93
in CHCl3); νmax (thin film): 3371 (b, NH), 1721 (s, C᎐O), 1649 (s,
᎐
C᎐C), 1504 (s, C᎐O) cmϪ1; δH (400 MHz, CDCl3) 0.97, 1.05
᎐
᎐
(18H, 2 × s, 2 × C(CH3)3), 1.39 (3H, d, JCH ,CH 7.0 Hz, CH3),
1.44 (9H, s, OC(CH3)3), 3.88–4.01 (2H, m, H-35, H-6), 4.10–4.21
(2H, m, H-4, H-6Ј), 4.36–4.40 (1H, m, CHCH3), 4.67 (1H, dd,
J1,2 6.1 Hz, J2,3 2.1 Hz, H-2), 5.07–5.10 (1H, m, NH), 5.41–5.43
(1H, m, H-3), 6.32 (1H, dd, J1,3 1.4 Hz, H-1); δC (100.6 MHz,
CDCl3) 18.8 (q, CH3), 19.8, 22.6 (2 × s, 3 × C(CH3)3), 26.8, 27.3
(2 × q, 6 × C(CH3)3), 28.3 (q, 3 × OC(CH3)3), 49.4 (d,
CHCH3), 65.6 (t, C-6), 72.8, 73.0, 73.5 (3 × d, C-3, C-4, C-5),
99.9 (d, C-2), 145.3 (d, C-1), 154.9 (s, CHC(O)O), 173.1 (s,
OC(O)N); m/z (ESϩ) 516 (MNH4ϩ ϩ MeCN, 11), 480 (MNaϩ,
5), 475 (MNH4ϩ, 7), 458 (MHϩ, 9%) (HRMS calcd. for
C22H40O7NSi (MHϩ) 458.2574. Found 458.2574).
9 F. N. Tebbe, G. W. Parshall and G. S. Reddy, J. Am. Chem. Soc.,
1978, 100, 3611–3613.
10 H. Y. Godage and A. J. Fairbanks, Tetrahedron Lett., 2000, 41,
7589–7593.
11 H. Y. Godage and A. J. Fairbanks, Tetrahedron Lett., 2003, 44,
3631–3635.
12 J. O. Hoberg, Carbohydr. Res., 1997, 300, 365–367.
13 In certain cases in the β-series some epimerisation at the anomeric
centre was observed during the thermal rearrangement step when
benzonitrile was used as the solvent; this undesirable side reaction
could be completely avoided by switching to tributylamine as the
solvent employed for the Claisen rearrangement step.
14 The stereochemistry of the newly formed β-anomeric linkage was
demonstrated by NOE difference experiments, which in all cases
revealed enhancements between H-1 and H-5 (original carbohydrate
numbering).
15 D. J. Chambers, G. R. Evans and A. J. Fairbanks, Tetrahedron:
Asymmetry, 2003, 14, 1767–1769.
16 M. Sharma and R. K. Brown, Can. J. Chem., 1966, 44, 2825–
2835.
3-O-(Azidoacetyl)-4,6-O-di-tert-butylsilanediyl-D-arabino-hex-
1-enitol 39
General method A: Glycal 5 (1.346 g, 4.70 mmol), azidoacetic
acid (605.7 mg, 5.99 mmol), dicyclohexylcarbodiimide (1.90 g,
9.22 mmol) and dimethylaminopyridine (113 mg, 0.922 mmol),
in dichloromethane (20 ml), gave ester 39 (1.47 g, 85%) as a
colourless oil; [α]1D9 Ϫ55.6 (c, 1.08 in CHCl3); νmax (thin film):
2109 (s, N ), 1752 (s, C᎐O), 1648 (w, C᎐C) cmϪ1; δH (400 MHz,
᎐
᎐
3
CDCl3) 1.00, 1.06 (18H, 2 × s, 2 × C(CH3)3), 3.93 (2H, s,
N3CH2), 3.94–4.03 (2H, m, H-5, H-6), 4.18–4.23 (2H, m, H-4,
H-6Ј), 4.76 (1H, dd, J1,2 6.1 Hz, J2,3 1.9 Hz, H-2), 5.48–5.51 (1H,
m, H-3), 6.36 (1H, dd, J1,3 1.7 Hz, H-1); δC (100.7 MHz, CDCl3)
19.8, 22.7 (2 × s, 2 × C(CH3)3), 26.8, 27.3 (2 × q, 2 × C(CH3)3),
50.5 (t, N3CH2), 65.6 (t, C-6), 72.9, 73.5, 74.0 (3 × d, C-3, C-4,
17 V. Pedretti, J.-M. Mallet and P. Sinaÿ, Carbohydr. Res., 1993, 244,
247–257.
18 Allal (see reference 19(b)) was itself synthesised from diacetone
glucose, by a sequence of oxidation and stereoselective reduction.
Full details will be published separately.
19 (a) M. Sharma and R. K. Brown, Can. J. Chem., 1968, 46, 757–766;
(b) For data see: R. D. Guthrie and R. W. Irvine, Carbohydr. Res.,
1979, 72, 285–288 . See also reference 15.
20 R. D. Dawe and B. Fraser-Reid, J. Org. Chem., 1984, 49, 522–528.
21 P. Allevi, M. Anastasia, P. Cuiffreda, A. Fiecchi and A. Scala,
J. Chem. Soc., Perkin Trans. 1, 1989, 1275–1280.
C-5), 99.7 (d, C-2), 145.6 (d, C-1), 181.3 (s, C᎐O); m/z (FIϩ) 369
᎐
(100, Mϩ). (HRMS calcd. for C16H27N3O5Si (Mϩ) 369.1720.
Found, 369.1734).
22 H. Shao, Z. Wang, E. Lacroix, S.-H. Wu, H. J. Jennings and W. Zou,
J. Am. Chem. Soc., 2002, 124, 2130–2131.
Acknowledgements
23 The stereochemistry of the newly formed α-anomeric linkage was
demonstrated by NOE difference experiments, which in all cases
revealed no enhancements between H-1 and H-5 (original carbo-
hydrate numbering), whilst enhancements were observed between
H-5 and the two protons attached to the anomeric methylene carbon
atom.
24 (a) S. Torii, T. Inokuchi and T. Sugiura, J. Org. Chem., 1986, 51,
155–161; (b) H. M. Sell and K. P. Link, J. Am. Chem. Soc., 1938, 60,
1813–1814.
We gratefully acknowledge financial support from the EPSRC
(Project Studentships to H. Y. G. and D. J. C.) and from Cell-
tech (CASE award to D. J. C). We thank Dr Andrew R. Cowley
for the crystal structure determinations, and also acknowledge
the use of the EPSRC Mass Spectrometry Service (Swansea,
UK) and the Chemical Database Service (CDS) at Daresbury,
UK.
25 H. J. Carlsen Per, T. Katsuki, V. S. Martin and K. B. Sharpless,
J. Org. Chem., 1981, 46, 3936–3938.
References
26 See for example: (a) L. Colombo, G. Casiraghi, A. Pittalis and
G. Rassu, J. Org. Chem., 1991, 56, 3897–3900; (b) D. Urban,
T. Skrydstrup and J.-M. Beau, Chem. Commun., 1998, 955–956;
(c) B. Westermann, A. Walter and N. Diedrichs, Angew. Chem.,
Int. Ed., 1999, 38, 3384–3386; (d ) A. D. Campbell, D. E. Paterson,
R. J. K. Taylor and A. M. Raynham, Chem. Commun., 1999, 1599–
1600; (e) T. Nishikawa, Mi. Ishikawa and M. Isobe, Synlett, 1999,
123–125.
27 R. C. Hartley and G. J. McKiernan, J. Chem. Soc., Perkin Trans. 1,
2002, 2763–2793.
28 R. D. Guthrie, R. W. Irvine, B. E. Davison, K. Henrick and
J. Trotter, J. Chem. Soc., Perkin Trans. 2, 1981, 468–472.
1 See ‘The Chemistry of C-Glycosides’, D. E. Levy and C. Tang,
Tetrahedron Organic Chemistry Series, Pergamon Press, Oxford,
UK, 1995, vol. 13.
2 For a recent review see: Y. Du, R. J. Linhardt and I. R. Vlahov,
Tetrahedron, 1998, 54, 9913–9959.
3 For some recent references see: (a) Q. Wang and R. Linhardt, J. Org.
Chem., 2003, 68, 2668–2672; (b) J. L. Chiara and E. Sesmilo,
Angew. Chem., Int. Ed. Engl., 2002, 41, 3242–3246; (c) D. E.
Paterson, F. K. Griffin, M.-L. Alcaraz and R. J. K. Taylor, Eur. J.
Org. Chem., 2002, 1323–1336; (d ) H. Abe, S. Shuto and A. Matsuda,
J. Am. Chem. Soc., 2001, 123, 11870–11882.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 7 2 – 3 7 8 6
3786