Regio- And stereo-selectivity issues in radical brominations of allylic units of vinylogous esters/carbonates bearing the 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl auxiliary and in nucleophilic displacements of the derived allylic bromides

Article abstract of DOI:10.1039/b000901f

Under radical conditions, N-bromosuccinimide effects bromination of the methyl group of the 1-oxyallyl unit of (E)-3-methyl-4-(2′,3′,4′,6′-tetra-O-acetyl-β-D- glucopyranosyloxy)but-3-en-2-one 1a, (E)-2-methyl-1-(2′,3′,4′,6′-tetra-O-acetyl-β-D- glucopyranosyloxy)pent-1-en-3-one 1b and methyl/ethyl (E)-2-methyl-3-(2′,3′,4′,6′-tetra-O-acetyl-β-D- glucopyranosyloxy)prop-2-enoate 1c/1d to give thie bromoethyl derivatives 14a-14d. Displacement of the bromine atom of compounds 14a-c occurs without allylic rearrangement (in Me₂CO under reflux and/or in MeCN at ambient temperature) with sodium azide (to give the azidomethyl derivatives 15a-c), potassium O-ethyl dithiocarbonate [to give the ethoxy(thiocarbonyl)thiomethyl derivatives 16a-c] and with potassium thiocyanate (to give the thiocyanatomethyl derivatives 17a-c). Silver(i) thiocyanate in acetonitrile also effects the 14a → 17a conversion. Compounds 14a, 14b and 14d react with sodium acetate in boiling acetonitrile to give largely the rearranged acetates 19a/20a, 19b/20b and 19d/20d with a moderate degree of stereoselection under kinetically controlled conditions. However, equilibration slowly occurs under the reaction conditions (requiring the presence of NaOAc) to give mainly the unrearranged acetates 18a, 18b and 18d. With silver(i) acetate in acetonitrile, the bromides 14a and 14d are transformed into the rearranged acetates 19a/20a and 19d/20d with a good degree of stereoselection and without appreciable equilibration. The reaction of the bromide 14a with silver(i) oxide and acetic acid parallels that observed with sodium acetate, the equilibration of the acetates 18a, 19a and 20a being induced by acetic acid. The bromide 14a reacts with alcohols at ambient temperature in the presence of silver(i) oxide to give, in kinetically controlled reactions, mixtures of rearranged alkoxy derivatives of types 24/25 and unrearranged alkoxy derivatives of type 23. Although the former'products predominate, their proportion in the mixture declines as the size of the . alcohol increases. Similar results are observed for the bromides 14b and 14d. The ambident reactivity of allylic bromides of type 14 towards nucleophiles is consistent with the principle of hard and soft acids and bases. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b000901f

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Regio- and stereo-selectivity issues in radical brominations of
allylic units of vinylogous esters/carbonates bearing the 2,3,4,6-
tetra-O-acetyl-ꢀ-D-glucopyranosyl auxiliary and in nucleophilic
displacements of the derived allylic bromides†
1
A. Paula Esteves,a Ana M. Freitas,a Clive M. Raynorb and Richard J. Stoodley*b
a Department of Chemistry, University of Minho, Campus de Gaultar, 4700-320 Braga, Portugal
b Department of Chemistry, UMIST, PO Box 88, Manchester, UK M60 1QD
Received (in Cambridge, UK) 1st February 2000, Accepted 5th April 2000
Under radical conditions, N-bromosuccinimide effects bromination of the methyl group of the 1-oxyallyl unit of (E)-
3-methyl-4-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)but-3-en-2-one 1a, (E)-2-methyl-1-(2Ј,3Ј,4Ј,6Ј-tetra-O-
acetyl-β--glucopyranosyloxy)pent-1-en-3-one 1b and methyl/ethyl (E)-2-methyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--
glucopyranosyloxy)prop-2-enoate 1c/1d to give the bromoethyl derivatives 14a–14d.
Displacement of the bromine atom of compounds 14a–c occurs without allylic rearrangement (in Me2CO under
reflux and/or in MeCN at ambient temperature) with sodium azide (to give the azidomethyl derivatives 15a–c),
potassium O-ethyl dithiocarbonate [to give the ethoxy(thiocarbonyl)thiomethyl derivatives 16a–c] and with
potassium thiocyanate (to give the thiocyanatomethyl derivatives 17a–c). Silver() thiocyanate in acetonitrile also
effects the 14a → 17a conversion.
Compounds 14a, 14b and 14d react with sodium acetate in boiling acetonitrile to give largely the rearranged
acetates 19a/20a, 19b/20b and 19d/20d with a moderate degree of stereoselection under kinetically controlled
conditions. However, equilibration slowly occurs under the reaction conditions (requiring the presence of NaOAc) to
give mainly the unrearranged acetates 18a, 18b and 18d. With silver() acetate in acetonitrile, the bromides 14a and
14d are transformed into the rearranged acetates 19a/20a and 19d/20d with a good degree of stereoselection and
without appreciable equilibration. The reaction of the bromide 14a with silver() oxide and acetic acid parallels
that observed with sodium acetate, the equilibration of the acetates 18a, 19a and 20a being induced by acetic acid.
The bromide 14a reacts with alcohols at ambient temperature in the presence of silver() oxide to give, in kinetically
controlled reactions, mixtures of rearranged alkoxy derivatives of types 24/25 and unrearranged alkoxy derivatives of
type 23. Although the former products predominate, their proportion in the mixture declines as the size of the
alcohol increases. Similar results are observed for the bromides 14b and 14d.
The ambident reactivity of allylic bromides of type 14 towards nucleophiles is consistent with the principle of hard
and soft acids and bases.
Introduction
Over the past few years, we have demonstrated that β-oxy α,β-
unsaturated carbonyl compounds incorporating the 2,3,4,6-
tetra-O-acetyl-β--glucopyranosyl auxiliary are versatile
intermediates in asymmetric synthesis.2 For example, com-
pounds of type 1 exhibit reasonable Re-face selectivity in
hydrogenation,3 bromopropoxylation4 and epoxidation reac-
tions,5 affording predominantly products of types 2–4; in the
case of compounds of types 3 and 4, it is possible to remove the
auxiliary and to generate chirons featuring tertiary carbon
stereogenic centres, e.g. of types 5 and 6 (Scheme 1).
Furthermore, the dienes 7a and 7b, obtained by enol silyl-
ation of the vinylogous esters 1a and 1b, display excellent Re-
face selectivity in Diels–Alder reactions6 affording, for instance,
the endo-cycloadducts 8a and 8b with N-phenylmaleimide
(Scheme 2).
In this paper, we describe our efforts to effect the allylic func-
tionalisation of systems of type 1. As outlined in Scheme 3,
such a process could, in principle, lead to products of types
9–12. Hopefully, compounds of type 9 would react similarly
to their methyl counterparts (cf. Schemes 1 and 2), permitting
† For preliminary communication, see ref. 1.
DOI: 10.1039/b000901f
Scheme 1
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
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This journal is © The Royal Society of Chemistry 2000

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Scheme 4
Scheme 2
groups adjacent to the vinylogous ester carbonyl functions
being detected).
With bromides of type 14 in hand, attention was directed at
defining the regio- and stereo-selectivities of their reactions
with representative heteroatomic nucleophiles. In principle,
attack may occur to give products of type 9 (and 10 if olefinic
isomerisation occurs) and products of types 11 and 12. Clearly,
several mechanisms are feasible for such substitution reactions.
Thus, products of type 9 may arise by SN2 or SN1 pathways,
products of type 10 by SN1 processes, and products of types
11 and 12 by SN2Ј, SN1Ј or conjugate addition–elimination
pathways.
The outcomes of the reactions of the bromides 14a–c
with sodium azide, potassium O-ethyl dithiocarbonate and
potassium thiocyanate are summarised in Scheme 5.
Scheme 3
access to related products with additional functionality. If
allylic rearrangements were to occur, the products of type 11 or
12 would be of interest in the synthesis of novel chirons.
Results and discussion
In the hope that we would be able to derive the bromide 14a and
subsequently replace its halogen atom by N-, S- and O-nucleo-
philes under SN2-like conditions, we decided to investigate the
reaction of the butenone 1a7 with N-bromosuccinimide (NBS).
Although the reagent (in CCl4 in the presence of a radical initi-
ator) has been widely used as an allylic brominating agent,8 we
are unaware of any studies involving its application to α-methyl
β-oxy α,β-unsaturated carbonyl compounds.‡
When heated with NBS in carbon tetrachloride in the pres-
ence of 2,2Ј-azoisobutyronitrile (AIBN), the butenone 1a was
converted into one main product (72% yield after crystallis-
ation) that was formulated as the bromide 14a. That the prod-
uct had been formed without (E) → (Z) isomerisation of the
double bond was suggested by its olefinic proton chemical shift
(δ 7.47) [which was very similar to that of the reactant 1a
(δ 7.36)] and corroborated by a nuclear Overhauser enhance-
ment difference (NOED) spectroscopic study (in which mutual
enhancements were observed between the olefinic proton and
the ketonic methyl protons). Similarly, the pentenone 1b6 was
transformed into the bromide 14b (79% yield after crystallis-
ation), the propenoate 1c3 into the bromide 14c (61% yield after
crystallisation) and the propenoate 1d3 into the bromide 14d
(63% yield after crystallisation).
Scheme 5
In boiling acetone, sodium azide reacted with the bromides
14a–c to give the azides 15a–c (in respective yields of 64, 74 and
50% after crystallisation); the reaction involving the bromide
14a was also conducted in acetonitrile at ambient temperature
to give the azide 15a (68% yield after crystallisation).
Potassium O-ethyl dithiocarbonate (in MeCN at ambient
temperature) effected the conversion of the bromides 14a–c into
the dithiocarbonates 16a–c (in respective yields of 54, 65 and
78% after chromatography and/or crystallisation).
In the presence of potassium thiocyanate (in MeCN at am-
bient temperature), the bromides 14a–c were transformed into
the thiocyanates 17a–c (in respective yields of 76, 72 and 60%
after crystallisation). In accord with the thiocyanate formu-
lation (rather than the isothiocyanate alternative), compounds
17a–c showed characteristic sharp but weak IR absorptions at
≈2150 cmϪ1 (alkyl isothiocyanates display broad intense
absorptions in the 2106–2084 cmϪ1 region).9 Furthermore, the
13C NMR spectrum of compound 17a displayed a signal at δC
112.2 typical of an alkyl thiocyanate carbon (alkyl isothiocy-
anate carbons resonate in the δC 128.6–132.3 region).10
Clearly, the foregoing bromination reactions were highly
regioselective, with attack occurring at the unsubstituted
primary carbon of the presumed allylic radical intermediates
13a–d (Scheme 4). It is also worth noting that high site selectiv-
ity was realised in the case of the reactants 1a and 1b (no
products arising from bromination of the methyl/methylene
Presumably, the reactions summarised in Scheme 5 take place
by SN2 pathways. The use of silver() thiocyanate in place of
potassium thiocyanate would be expected to increase the SN1-
character of such reactions; it was hoped therefore to produce
alkyl isothiocyanates in preference to alkyl thiocyanates.11
However, when treated with the reagent in acetonitrile at
ambient temperature, the bromide 14a was slowly transformed
into the thiocyanate 17a.
‡ Searches of databases (STN International, Beilstein Crossfire) using
the substructure A failed to provide any representative compounds.
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J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765

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The outcome of the reaction of the bromide 14a with sodium
acetate (in MeCN under reflux) is summarised in Scheme 6.
Related intermediates of type 22 may also be involved in the
equilibration reactions.
The bromides 14a and 14d were also subjected to the
action of silver() acetate in acetonitrile at ambient temperature.
After ca. 3 h (when the starting materials were depleted),
a 3:86:11 mixture of the acetoxy derivatives 18a, 19a and
20a was present in the former reaction and a 5:87:8 mixture
of the acetoxy derivatives 18d, 19d and 20d in the latter
reaction. From the reaction involving the bromide 14d, it was
possible to isolate compound 19d in 41% yield after crystallis-
ation. The proportion of the acetoxy derivatives 18a, 19a
and 20a changed with time and, after 48 h, it was 23:64:13.
Evidently, partial equilibration occurs under the reaction
conditions.
The reaction of the bromide 14a with silver() acetate in
acetic acid (generated by adding Ag2O to stirred HOAc) was
also examined.¶ Within 10 min, a 5:71:24 mixture of the
acetoxy derivatives 18a, 19a and 20a was produced; the propor-
tions altered to 26:52:22 after 3 h and to 72:12:16 after 18 h.
The product obtained from an 18 h reaction was fractionated
by HPLC to give a 50:50 mixture of compounds 19a and 20a in
23% yield and compound 18a in 51% yield. In parallel experi-
ments, the bromide 14a and a 3:90:7 mixture of the acetoxy
derivatives 18a, 19a and 20a were subjected, respectively, to the
actions of silver() oxide and acetic acid and of acetic acid for
96 h. The mixture of the acetoxy derivatives 18a, 19a and 20a
was produced in each case, the proportions being 78:8:14 and
81:8:11.
Scheme 6
Three substitution products, formulated as the unrearranged
acetoxy derivative 18a and the rearranged acetoxy derivatives
19a and 20a, resulted; their proportion varied with time. In the
early stages of the reaction, mainly a 6:79:15 mixture of com-
pounds 18a, 19a and 20a was produced;§ after 48 h, the propor-
tion of compounds 18a, 19a and 20a changed to 75:12:13.
From a preparative-scale experiment (which gave a 17:67:16
mixture of compounds 18a, 19a and 20a), two fractions were
isolated after HPLC. The first-eluted fraction, obtained in 59%
yield, was an 80:20 mixture of the acetoxy derivatives 19a and
20a; after two crystallisations, the product comprised an 86:14
mixture of compounds 19a and 20a. The second fraction,
obtained in 15% yield, was the acetoxy derivatives 18a.
A 74:12:14 mixture of compounds 18a, 19a and 20a was
produced when the acetoxy derivative 18a was subjected to the
action of sodium acetate in boiling acetonitrile, establishing the
equilibrium nature of the reaction. Equilibration did not occur
in boiling acetonitrile alone, revealing that the isomerisation
was not simply a thermal process.
Clearly, there is a close parallel in the reactions of the
bromides 14a and 14d with silver() acetate and sodium acetate.
However, with the former reagent in acetonitrile, it is possible to
largely avoid product equilibration and to generate the kinetic
acetoxy derivatives 19a/20a and 19d/20d with high stereo-
selection (≈10:1).
The bromides 14b and 14d reacted in an analogous manner
with sodium acetate (Scheme 6). Thus, the former reaction led
to the acetoxy derivatives 18b, 19b and 20b (initially as a
10:71:19 mixture and as a 73:12:15 mixture after 96 h) and the
latter reaction to the acetoxy derivatives 18d, 19d and 20d (the
proportions changing from 22:58:20 after 6 h to 56:26:18
after 180 h).§
A study was undertaken of the reaction of the bromide 14a
with alcohols in the presence of silver() oxide (Scheme 7). In
From a preparative-scale experiment involving the bromide
14b (which gave a 10:75:15 mixture of compounds 18b, 19b
and 20b together with ≈30% of starting material recovered),
one main fraction (50% yield) was isolated after chromato-
graphy; it was identified as an 84:16 mixture of the acetoxy
derivatives 19b and 20b. A similar experiment involving the
bromide 14d (which led to a 32:50:16 mixture of the acetoxy
derivatives 18d, 19d and 20d together with ≈25% unchanged
starting material) resulted in the isolation, after chromato-
graphy, of only one homogeneous fraction (8% yield); it was
identified as the acetoxy derivative 18d.
Clearly, in the early stages, the reactions of the bromides 14a,
14b and 14d with sodium acetate are under kinetic control, and
afford mainly the rearranged acetoxy derivatives 19a/20a,
19b/20b, and 19d/20d (with selectivities of ≈4:1). With time,
the products interconvert to give equilibrium mixtures (with a
preponderance of compounds 18a and 18b in the case of the
bromides 14a and 14b). Although the kinetic products are
formally the result of SN2Ј-like processes, intermediates of type
21 (formed by conjugate addition reactions) may intervene.
Scheme 7
the case of methanol,¶ a 7:67:26 mixture of the methoxy
derivatives 23a, 24a and 25a|| was produced within 2 h.
Although the proportions did not change, two new products,
¶ In acetic acid or methanol alone, the bromide 14a decomposed within
3 h with formation of the tetraacetate 27.
§ The evidence for the assignment of the stereostructures 19a, 19b and
19d to the major rearranged acetoxy derivatives, which is tentative, will
be discussed elsewhere.
|| The evidence for the assignment of the stereostructures 24a–e, 29a–c
and 32a–c to the major rearranged alkoxy derivatives will be discussed
elsewhere.
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
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Table 1 Outcome of the reaction of the bromides 14a, 14b and 14d with alcohols in the presence of silver() oxide
Ratio of
Ratio of
Substrate
Alcohol
Products
Composition
regioisomersa
stereoisomersb
14a
MeOH
EtOH
PrOH
23a, 24a, 25a
23b, 24b, 25b
23c, 24c, 25c
23d, 24d, 25d
23e, 24e, 25e
28a, 29a, 30a
28b, 29b, 30b
28c, 29c, 30c
31a, 32a, 33a
31b, 32b, 33b
31c, 32c, 33c
7:67:26
11:72:17
13:62:25
15:67:18
29:61:10
7:63:30
20:52:28
29:49:22
12:67:21
26:61:13
35:53:12
7:93
11:89
13:87
15:85
29:71
7:93
20:80
29:71
12:88
26:74
35:65
72:28
81:19
71:29
79:21
86:14
68:32
65:35
69:31
76:24
82:18
82:18
PriOH
ButOH
MeOH
PriOH
ButOH
MeOH
PriOH
ButOH
14b
14c
a Ratio of unrearranged alkoxy compounds to rearranged alkoxy compounds. b Ratio of rearranged (R)- to (S)-alkoxy compounds.
identified as the dimethoxy derivative 26a and the tetraacetate
27 (as a 2:1 mixture of α- and β-anomers), were in evidence
after 24 h. After 120 h, their relative concentrations had
doubled (≈20% of compound 26a was present in the mixture of
compounds 23a, 24a, 25a and 26a).
In a preparative-scale experiment, conducted for 24 h, the
product was separated into three fractions by HPLC. The first-
eluted fraction (66% yield) consisted of a 70:30 mixture of the
rearranged methoxy derivatives 24a and 25a; fractional crys-
tallisation provided compound 24a in a pure state (26% yield).
The second-eluted fraction (6% yield) was the unrearranged
methoxy derivative 23a. The third-eluted fraction (≈7% yield)
was mainly the dimethoxy derivative 26a. When resubjected to
the action of silver() oxide and methanol, compounds 23a and
24a were both partially converted (≈10%) into the dimethoxy
compound 26a (no change occurred in MeOH alone); there was
no evidence for the interconversion of the reactants.
Scheme 8
Evidently, the methoxy derivatives 23a, 24a and 25a are
formed from the bromide 14a in kinetically controlled
reactions; the products are then slowly transformed into
compounds 26a and 27.
Having established that the methanolysis of the bromide 14a
occurred with a high degree of regioselection and a modest
degree of stereoselection, it was of interest to extend the study
to other alcoholysis reactions (see Scheme 7). The results
involving ethanol, propan-1-ol, isopropyl alcohol and tert-butyl
alcohol are summarised in Table 1 (and compared with those
observed for MeOH). In all instances, mixtures of unrear-
ranged alkoxy derivatives of type 23 and rearranged alkoxy
derivatives of types 24 and 25|| were produced. Although the
rearranged products also predominated, their percentage com-
position of the mixture declined as the size of the alcohol
increased. The stereoisomeric ratios of the rearranged alkoxy
derivatives were modest and they were not substantially influ-
enced by the nature of the alcohol.
Scheme 9
atography). Similarly, the reaction of the bromide 14b with iso-
propyl alcohol gave rise to 66:34 mixture of the isopropoxy
derivatives 29b and 30b|| (43% yield after chromatography) and
with tert-butyl alcohol to a 69:31 mixture of the tert-butoxy
derivatives 29c and 30c|| (52% yield after chromatography).
From the reaction of the bromide 14c with methanol, it was
possible to isolate (after HPLC) a 74:26 mixture of the meth-
oxy derivatives 32a and 33a (64% yield) and the methoxy
derivative 31a (8% yield). The reaction with isopropyl alcohol
gave rise (after HPLC) to an 82:18 mixture of the isopropoxy
derivatives 32b and 33b (55% yield) and compound 31b (22%
yield). Finally, the bromide 14c underwent reaction with tert-
butyl alcohol in the presence of silver() oxide to afford (after
chromatography) an 82:18 mixture of the tert-butoxy deriv-
atives 32c and 33c (48% yield) and compound 31c (32% yield).
The contrasting behaviour of bromides of type 14 towards
azide/O-ethyl dithiocarbonate/thiocyanate anions and acetate
anions/alcohols is of interest. It remains to be established
The study (using MeOH, PriOH and ButOH) was extended
to the bromide 14b (Scheme 8) and to the bromide 14c (Scheme
9). As noted in Table 1, the substrates showed reactivities that
were similar to those observed for the bromide 14a. In the reac-
tion of the substrate 14b with methanol (in which there was 1H
NMR spectral evidence for the production of ≈10% of the
dimethoxy derivative 26b), a 69:31 mixture of the methoxy
derivatives 29a and 30a|| was isolated (59% yield after chrom-
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whether the unrearranged products arise by SN2 routes and the
rearranged products by SN2Ј processes (or conjugate addition–
elimination variants) or whether both products originate from
delocalised carbenium ion intermediates (paired with bromide
anions) formed by SN1 pathways. However, it is worth noting
that the outcomes are consistent with the principle of hard and
soft acids and bases.12 Thus, bromides of type 14 are attacked
only at the softer allylic site by two soft nucleophiles [EtOC-
(:S)SϪ and NCSϪ] and one borderline nucleophile (N3Ϫ) and
preferentially at the harder allylic site by two hard nucleophiles
(AcOϪ and ROH).
In conclusion, we consider our findings to be of synthetic
and mechanistic note. Compounds of type 14 appear to be the
first representatives of α-bromomethyl β-oxy α,β-unsaturated
compounds to be described and their formation provides an
opening insight into the regiochemical behaviour of 2-acyl/
alkoxycarbonyl 1-oxy allylic radicals. The substitution reac-
tions, involving a new class of allylic bromides, highlight the
contrasting behaviour of soft/borderline nucleophiles com-
pared with hard nucleophiles and contribute to an understand-
ing of ambident allylic reactivity.13 Finally, the methodology
makes compounds of types 14–17, of notable synthetic poten-
tial, accessible by practical routes.
H4CH2OH as matrix) were measured using a Kratos MS 50
spectrometer.
Allylic bromination studies
General procedure. Recrystallised NBS (0.890 g, 5 mmol) and
a catalytic quantity of AIBN were added to a stirred suspension
of the vinylogous ester/carbonate 1a–d (4 mmol) in dry carbon
tetrachloride (60 cm3) and the mixture was heated under reflux.
When the reaction was complete [it was best to monitor the
progress by 1H NMR spectroscopy (samples were removed and
worked up as described below); depletion of the allylic bromide
generally took 1–4 h], the mixture was concentrated and the
residue partitioned between methylene dichloride and aq.
sodium metabisulfite. After having been washed with water and
dried (MgSO4), the organic phase was concentrated and the
product was purified by crystallisation.
(E)-3-Bromomethyl-4-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-gluco-
pyranosyloxy)but-3-en-2-one 14a. The butenone 1a (6.71 g, 15.6
mmol) gave the title compound 14a (5.51 g, 72%) (after crystal-
lisation from EtOAc–hexanes); mp 137–138 ЊC; [α]D ϩ30 (c 0.4,
CHCl3) (Found: C, 44.8; H, 4.9; Br, 15.9. C19H25BrO11 requires
C, 44.8; H, 4.9; Br, 15.7%); λmax (EtOH)/nm 245 (ε 13 100); νmax
(KBr)/cmϪ1 1750 (ester C᎐O), 1675 (vinylogous ester C᎐O) and
᎐
᎐
Experimental
1645 (C᎐C); δ (300 MHz; CDCl3) 2.045, 2.051 and 2.10 (3, 3
᎐
H
and 6 H, each s, 4 × MeCO2), 2.31 (3 H, s, 1-H3), 3.87 (1 H,
ddd, J 2.5, 4.5 and 9.5, 5Ј-H), 4.16–4.21 (3 H, m, 6Ј-H and
3-CH2Br), 4.31 (1 H, dd, J 4.5 and 12.5, 6Ј-H), 5.02 (1 H, d,
J 7.5, 1Ј-H), 5.15–5.32 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.47
(1 H, s, 4-H) (in an NOED spectroscopic experiment, irradi-
ation at δ 2.31 enhanced the s at δ 7.47 at 7.9%; irradiation at
δ 4.18 caused a 0.7% enhancement of the s at δ 2.31; irradi-
ation at δ 7.47 caused a 3.7% enhancement of the d at δ 5.02
and a 1.3% enhancement of the s at δ 2.31); m/z (FAB) 841
and 839 [M(C14H19O9)ϩ, each 25%], 643 and 641 (65 and 55),
511 and 509 (MHϩ, 28 and 35), 331 (C14H19O9ϩ, 100) and 169
(40).
Dry solvents, referred to in the ensuing experiments, were pre-
pared as follows: carbon tetrachloride was refluxed over phos-
phorus pentaoxide and distilled from it; acetone was refluxed
over magnesium sulfate, decanted, stirred overnight with
calcium chloride, decanted, refluxed over fresh magnesium
sulfate, distilled from it and stored over 4 Å molecular sieves;
acetonitrile was refluxed over phosphorus pentaoxide, distilled
from it and stored over 4 Å molecular sieves. Light petroleum
refers to that fraction boiling in the range 40–60 ЊC; NBS was
recrystallised from ten times its weight of water, dried in vacuo
(over P2O5) and stored in the dark; sodium acetate was dried
in an oven at ≈150 ЊC.
The progress of reactions was monitored by TLC, using
Merck plastic or aluminium sheets coated with silica gel (60
F254); chromatograms were initially examined under UV light
(Mineralight UVG2-58 lamp) and visualised with a p-anis-
aldehyde stain [plates were sprayed with p-MeOC6H4CHO–
conc. H2SO4–EtOH (1:4:95) and heated]. Column chromato-
graphy was effected, under positive pressure from a compressed
air line, with Crossfield Sorbsil C60 flash silica or Merck
Kieselgel 60. Preparative HPLC was carried out using a column
(25 × 0.8 cm) of Spherisorb S10 silica, a Kontron 420 pump, a
Rheodyne 7125 injector and Kontron 742 UV and ERC-7515A
RI detectors.
(E)-2-Bromomethyl-1-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-gluco-
pyranosyloxy)pent-1-en-3-one 14b. The pentenone 1b (1.89 g,
4.1 mmol) gave the title compound 14b (1.70 g, 79%) (after crys-
tallisation from Et2O–light petroleum); mp 92–94 ЊC; [α]D ϩ29
(c 0.4, CHCl3) (Found: C, 45.6; H, 5.1; Br, 15.1. C20H27BrO11
requires C, 45.9; H, 5.2; Br, 15.3%); λmax (EtOH)/nm 245
(ε 13 800); νmax (KBr)/cmϪ1 1750 and 1740 (ester C᎐O), 1670
᎐
(vinylogous ester C᎐O) and 1645 (C᎐C); δH (300 MHz; CDCl3)
᎐
᎐
1.13 (3 H, J 7.5, 5-H3), 2.04, 2.05, 2.09 and 2.10 (each 3 H,
s, 4 × MeCO2), 2.59–2.67 (2 H, m, 4-H2), 3.86 (1 H, ddd, J 2.5,
4.5 and 9.5, 5Ј-H), 4.17 and 4.31 [each 1 H, dd (J 2.5 and 12.5)
and dd (J 4.5 and 12.5), 6Ј-H2], 4.19 (2 H, s, 2-CH2Br), 5.01
(1 H, d, J 7.5, 1Ј-H), 5.15–5.32 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and
7.48 (1 H, s, 1-H); m/z (FAB) 525 and 523 (MHϩ, each 1%), 331
(C14H19O9ϩ, 100) and 169 (35).
Evaporations were conducted under reduced pressure (using
a water-pump) at р40 ЊC with a Büchi rotary evaporator (fitted
with a water condenser). Mps were determined with a either an
Electrothermal Digital or a Büchi 512 melting point apparatus
and are uncorrected. Specific rotations, given in 10Ϫ1 deg cm2
g
Ϫ1, were measured at ≈20 ЊC using a Thorn Automation Type
Methyl (E)-2-bromomethyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-
glucopyranosyloxy)prop-2-enoate 14c. The propenoate 1c (1.70
g, 3.8 mmol) gave the title compound 14c (1.18 g, 61%) (after
crystallisation from EtOAc–hexanes); mp 108–109 ЊC; [α]D ϩ59
(c 0.4, CHCl3) (Found: C, 43.7; H, 4.7; Br, 15.5. C19H25BrO12
requires C, 43.4; H, 4.8; Br, 15.2%); λmax (EtOH)/nm 236 (ε
243 or an Optical Activity 1000 polarimeter with a cell of path
length 0.1 dm. Carbon, hydrogen, nitrogen and sulfur contents
were determined with a Carlo Erba Model 1108 analyser;
bromine content was measured by oxygen combustion followed
by automatic argentometric titration on a Mettler DL25
titrator. A Perkin-Elmer Lambda 15 or a JASCO 7800
spectrometer was used to determine UV spectra; extinction
coefficients (ε) are presented in cm2 mmolϪ1. IR spectra were
recorded using a Perkin-Elmer 783, a Perkin-Elmer FTIR-1600
or a Shimadzu IR-345 spectrometer. NMR spectra were
measured using a Bruker AC 300, a Varian Unity Plus 300
or a Bruker AM 400 [with distortionless enhancement by polar-
isation transfer (DEPT) editing for 13C spectra]; J-values and
separations are given in Hz. FAB mass spectra (m-NO2C6-
13 700); νmax (KBr)/cmϪ1 1755 (ester C᎐O), 1715 (vinylogous
᎐
carbonate C᎐O) and 1645 (C᎐C); δH (300 MHz; CDCl3) 2.038,
᎐
᎐
2.043, 2.09 and 2.10 (each 3 H, s, 4 × MeCO2), 3.79 (3 H, s,
MeO2C), 3.84 (1 H, ddd, J 2.5, 4.5 and 9.5, 5Ј-H), 4.17 and 4.30
[each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2],
4.18 (2 H, AB q, J 10, separation of inner lines 10, 2-CH2Br),
4.96 (1 H, d, J 7.5, 1Ј-H), 5.13–5.30 (3 H, m, 2Ј-, 3Ј- and 4Ј-H)
and 7.54 (1 H, s, 3-H); m/z (FAB) 527 and 525 (MHϩ, 9 and
10%), 331 (C14H19O9ϩ, 100) and 169 (70).
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
1757

View Article Online
Ethyl (E)-2-bromomethyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-
glucopyranosyloxy)prop-2-enoate 14d. The propenoate 1d (1.38
g, 2.9 mmol) gave the title compound 14d (0.985 g, 63%) (after
crystallisation from Et2O–light petroleum); mp 98–99 ЊC; [α]D
ϩ45 (c 0.3, CHCl3) (Found: C, 44.8; H, 4.9; Br, 15.0. C20H27-
BrO12 requires C, 44.5; H, 5.0; Br, 14.8%); λmax (EtOH)/nm 236
ether–light petroleum to give the title compound 15c (0.122 g,
50%) as a pale yellow solid; mp 117–118 ЊC; [α]D ϩ8 (c 0.3,
CHCl3) (Found: C, 46.6; H, 5.1; N, 8.3. C19H25N3O12 requires
C, 46.8; H, 5.2; N, 8.6%); λmax (EtOH)/nm 229 (ε 14 000);
νmax (KBr)/cmϪ1 2140, 2100 and 2080 (N ), 1750 (ester C᎐O),
᎐
3
1710 (vinylogous carbonate C᎐O) and 1650 (C᎐C); δ (300
᎐
᎐
H
(ε 14 600); νmax (KBr)/cmϪ1 1760 (ester C᎐O), 1710 (vinylogous
MHz; CDCl3) 2.03, 2.04, 2.05 and 2.09 (each 3 H, s,
4 × MeCO2), 3.78 (3 H, s, MeO2C), 3.83 (1 H, ddd, J 2.5, 4.5
and 10, 5Ј-H), 3.90 and 4.10 (each 1 H, d, J 13, 2-CH2N), 4.15
and 4.29 [each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5),
6Ј-H2], 4.95 (1 H, d, J 7.5, 1Ј-H), 5.11–5.29 (3 H, m, 2Ј-, 3Ј- and
4Ј-H) and 7.66 (1 H, s, 3-H); m/z (FAB) 510 [M(Na)ϩ, 30%], 331
(C14H19O9ϩ, 95) and 169 (100).
᎐
carbonate C᎐O) and 1645 (C᎐C); δ (300 MHz; CDCl3) 1.31
᎐
᎐
H
(3 H, t, J 7, MeCH2), 2.03, 2.04, 2.09 and 2.10 (each 3 H, s,
4 × MeCO2), 3.85 (1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.13–4.33
(6 H, m, 2-CH2Br, 6Ј-H2 and OCH2Me), 4.97 (1 H, d, J 7.5, 1Ј-
H), 5.13–5.30 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.52 (1 H, s, 3-H);
m/z (FAB) 541 and 539 (MHϩ, each 6%), 331 (C14H19O9ϩ, 100)
and 169 (95).
Reactions of allylic bromides with potassium O-ethyl
dithiocarbonate
Reactions of allylic bromides with sodium azide
General procedure.
A
mixture of the allylic bromide
General procedure. A mixture of the allylic bromide (0.25
mmol) and potassium O-ethyl dithiocarbonate (0.040 g, 0.25
mmol) in dry acetonitrile (12.5 cm3) was stirred at room tem-
perature for 15 min and then concentrated. The residue was
partitioned between methylene dichloride and water and the
organic phase was washed sequentially with 1% aq. sodium
metabisulfite and water. Evaporation of the dried (MgSO4)
organic phase left a product that was purified in the matter
specified.
(0.5 mmol), sodium azide (0.033 g, 0.5 mmol) and dry acetone
(25 cm3) was heated under reflux. When the reaction was com-
plete (TLC), the mixture was partitioned between water and
methylene dichloride. Evaporation of the dried (MgSO4) organic
phase gave a material that was purified in the manner described.
(E)-3-Azidomethyl-4-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-gluco-
pyranosyloxy)but-3-en-2-one 15a. Method (a).—The material
obtained from the reaction of the allylic bromide 14a (0.102 g,
0.2 mmol) for 1.5 h was crystallised from ethyl acetate–light
petroleum to give the title compound 15a (0.060 g, 64%); mp
153–154 ЊC; [α]D ϩ14 (c 0.25, CH2Cl2) (Found: C, 48.5; H, 5.3.
C19H25N3O11 requires C, 48.4; H, 5.3%); λmax (EtOH)/nm 240
(ε 16 200); νmax (KBr)/cmϪ1 2140, 2100 and 2080 (N3), 1750
(E)-3-Ethoxy(thiocarbonyl)thiomethyl-4-(2Ј,3Ј,4Ј,6Ј-tetra-O-
acetyl-ꢀ-D-glucopyranosyloxy)but-3-en-2-one 16a. The reaction
of the allylic bromide 14a (0.127 g, 0.25 mmol) gave rise to a
product that was subjected to column chromatography [EtOAc–
hexanes (2:1) as eluent]. Crystallisation of the chromato-
graphed material (0.088 g, ≈64%) from diethyl ether–hexanes
gave the title compound 16a (0.074 g, 54%); mp 104–106 ЊC; [α]D
Ϫ6 (c 0.25, CH2Cl2) (Found: C, 47.7; H, 5.8; S, 11.4. C22H30-
O12S2 requires C, 48.0; H, 5.5; S, 11.6%); λmax (EtOH)/nm 207
(ε 12 300), 240 (14 400) and 282 (10 500); νmax (KBr)/cmϪ1 1755
(ester C᎐O), 1665 (vinylogous ester C᎐O) and 1650 (C᎐C);
᎐
᎐
᎐
δH (300 MHz; CDCl3) 2.03, 2.05, 2.06 and 2.09 (each 3 H, s,
4 × MeCO2), 2.30 (3 H, s, 1-H3), 3.86 (1 H, ddd, J 2.5, 4.5 and
9.5, 5Ј-H), 3.95 and 4.07 (each 1 H, d, J 13, 3-CH2N), 4.18 and
4.30 [each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5),
6Ј-H2], 5.01 (1 H, J 7.5, 1Ј-H), 5.13–5.31 (3 H, m, 2Ј-, 3Ј- and
4Ј-H) and 7.59 (1 H, s, 4-H); m/z (FAB) 331 (C14H19O9ϩ, 75%)
and 169 (100).
Method (b).—A mixture of the allylic bromide 14a (0.026 g,
0.05 mmol), sodium azide (0.003 g, 0.05 mmol) and dry
acetonitrile (2.5 cm3) was stirred for 6 h and then concentrated.
The residue was partitioned between water and methylene
dichloride. Evaporation of the dried (MgSO4) organic phase
left the azide 15a (0.022 g, 93%) [0.016 g, 68% (after crystallis-
ation from EtOAc–hexanes)].
and 1740 (ester C᎐O), 1670 (vinylogous ester C᎐O) and 1650
᎐
᎐
(C᎐C); δ (300 MHz; CDCl3) 1.42 (3 H, t, J 7, MeCH2), 2.03,
᎐
H
2.05, 2.08 and 2.10 (each 3 H, s, 4 × MeCO2), 2.28 (3 H, s,
1-H3), 3.85 (1 H, ddd, J 2.5, 4.5 and 9.5, 5Ј-H), 3.96 and 4.11
(each 1 H, d, J 12.5, 3-CH2S), 4.17 and 4.30 [each 1 H, dd (J 2
and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 4.65 (2 H, q, J 7,
OCH2Me), 4.99 (1 H, d, J 7.5, 1Ј-H), 5.13–5.30 (3 H, m, 2Ј-,
ϩ
,
3Ј- and 4Ј-H) and 7.49 (1 H, s, 4-H); m/z (FAB) 331 (C14H19O9
65%), 169 (100) and 109 (62) {(after addition of KI) 589
[M(K)ϩ, 35%]}.
(E)-2-Azidomethyl-1-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-gluco-
pyranosyloxy)pent-1-en-2-one 15b. The material obtained from
the reaction of the allylic bromide 14b (0.157 g, 0.3 mmol) for
1.5 h was crystallised from ethyl acetate–hexanes to give the
title azide 15b (0.108 g, 74%); mp 72–74 ЊC; [α]D ϩ 10 (c 0.25,
CH2Cl2) (Found: C, 49.6; H, 5.4; N, 8.4. C20H27N3O11 requires
C, 49.5; H, 5.6; N, 8.7%); λmax (EtOH)/nm 240 (ε 12 100); νmax
(KBr)/cmϪ1 2120, 2100 and 2080 (N ), 1755 (ester C᎐O), 1665
(E)-2-Ethoxy(thiocarbonyl)thiomethyl-1-(2Ј,3Ј,4Ј,6Ј-tetra-O-
acetyl-ꢀ-D-glucopyranosyloxy)pent-1-en-3-one 16b. The reaction
of the allylic bromide 14b (0.131 g, 0.25 mmol) gave rise to a
product that was subjected to column chromatography [EtOAc–
hexanes (2:1) as eluent]. The chromatographed material (0.092
g, 65%), isolated as a foam, was identified as the title compound
16b; [α]D Ϫ2 (c 0.5, CH2Cl2) (Found: C, 48.4; H, 6.2; S, 10.8.
C23H32O12S2 requires C, 48.9; H, 5.7; S, 11.3%); νmax (film)/cmϪ1
᎐
3
(vinylogous ester C᎐O) and 1650 (C᎐C); δH (300 MHz; CDCl3)
1755 (ester C᎐O), 1670 (vinylogous ester C᎐O) and 1645 (C᎐C);
᎐
᎐
᎐ ᎐ ᎐
1.13 (3 H, t, J 7.5, 5-H3), 2.03, 2.05, 2.06 and 2.09 (each 3 H, s,
4 × MeCO2), 2.57–2.67 (2 H, m, 4-H2), 3.85 (1 H, ddd, J 2.5,
4.5 and 10, 5Ј-H), 3.96 and 4.09 (each 1 H, d, J 13, 2-CH2N),
4.17 and 4.30 [each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and
δH (300 MHz; CDCl3) 1.11 (3 H, t, J 7.5, 5-H3), 1.42 (3 H, t, J 7,
MeCH2O), 2.03, 2.04, 2.08 and 2.10 (each 3 H, s, 4 × MeCO2),
2.55–2.65 (2 H, m, 4-H2), 3.84 (1 H, ddd, J 2.5, 4.5 and 9.5, 5Ј-
H), 3.99 and 4.12 (each 1 H, d, J 12.5, 2-CH2S), 4.17 and 4.30
[each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2],
4.65 (2 H, q, J 7, OCH2Me), 4.98 (1 H, d, J 7.5, 1Ј-H), 5.13–5.30
(3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.50 (1 H, s, 1-H); m/z (FAB) 331
(C14H19O9ϩ, 73%) and 169 (100) {(after addition of KI) 603
[M(K)ϩ, 100%]}.
12.5), 6Ј-H2], 4.99 (1 H, d, J 7.5, 1Ј-H), 5.13–5.31 (3 H, m, 2Ј-,
ϩ
3Ј- and 4Ј-H) and 7.60 (1 H, s, 1-H); m/z (FAB) 331 (C14H19O9
,
100%), 169 (69) and 43 (C2H3Oϩ, 72) {(after addition of KI)
524 [M(K)ϩ, 9%]}.
Methyl (E)-2-azidomethyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-
glucopyranosyloxy)prop-2-enoate 15c. The material obtained
from the reaction of the allylic bromide 14c (0.263 g, 0.5 mmol)
for 3.2 h was crystallised from methylene dichloride–diethyl
Methyl (E)-2-ethoxy(thiocarbonyl)thiomethyl-3-(2Ј,3Ј,4Ј,6Ј-
tetra-O-acetyl-ꢀ-D-glucopyranosyloxy)prop-2-enoate 16c. The
reaction of the allylic bromide 14c (0.131 g, 0.25 mmol) gave
1758
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765

View Article Online
rise to a product that was crystallised from methylene
dichloride–diethyl ether–light petroleum to give the title com-
pound 16c (0.110 g, 78%); mp 105.5–107 ЊC; [α]D Ϫ4 (c 0.46,
CH2Cl2) (Found: C, 46.6; H, 5.3; S, 10.9. C22H30O13S2 requires
C, 46.6; H, 5.3; S, 11.3%); νmax (KBr)/cmϪ1 1780, 1760 and 1745
and 12.5), 6Ј-H2], 5.04 (1 H, d, J 7.5, 1ЈH), 5.13–5.33 (3 H, m,
2Ј-, 3Ј- and 4Ј-H) and 7.65 (1 H, s, 1-H); m/z (FAB) 524
[M(Na)ϩ, 5%], 502 (MHϩ, 1) and 331 (C14H19O9ϩ, 100).
Methyl (E)-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-ꢀ-D-glucopyranosyl-
oxy)-2-(thiocyanatomethyl)prop-2-enoate 17c. The product
obtained from the reaction of the allylic bromide 14c (0.210 g,
0.4 mmol) for 15 h was predominantly the thiocyanate 17c.
Crystallisation of the material from ethyl acetate–light petrol-
eum gave the title compound 17c (0.121 g, 60%); mp 131–
132.5 ЊC; [α]D ϩ42 (c 0.35, CHCl3) (Found: C, 47.6; H, 5.3; N,
2.7; S, 6.8. C20H25NO12S requires C, 47.7; H, 5.0; N, 2.8; S,
(ester C᎐O), 1720 (vinylogous carbonate C᎐O) and 1645 (C᎐C);
᎐
᎐
᎐
δH (300 MHz; CDCl3) 1.43 (3 H, t, J 7, MeCH2), 2.03, 2.04, 2.08
and 2.11 (each 3 H, s, 4 × MeCO2), 3.76 (3 H, s, MeO2C), 3.83
(1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.04 (2 H, AB q, J 12.5,
separation of inner lines 13, 2-CH2S), 4.16 and 4.20 [each 1 H,
dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 4.66 (2 H, q,
J 7, OCH2Me), 4.94 (1 H, d, J 7.5, 1Ј-H), 5.12–5.29 (3 H, m, 2Ј-,
3Ј- and 4Ј-H) and 7.56 (1 H, s, 3-H); δC (75 MHz; CDCl3) 14.1
(CH3CH2), 20.9 and 21.0 (4 × CH3CO), 29.8 (2-CH2), 52.3
(CH3O), 61.8 (6Ј-CH2), 68.1, 70.8, 72.5 and 73.1 (2Ј-, 3Ј-,
4Ј- and 5Ј-CH), 70.2 (OCH2Me), 101.0 (1Ј-CH), 109.2 (2-C),
155.7 (3-CH), 166.9, 169.4, 169.6, 170.5 and 170.9 (CO2Me and
4 × MeCO) and 214.1 (CS); m/z (FAB) 567 (MHϩ, 2%), 331
(C14H19O9ϩ, 70), 169 (C9H13O3ϩ, 95), 109 (70) and 43 (100)
{(after addition of KI) 605 [M(K)ϩ, 15%]}.
6.4%); λmax (EtOH)/nm 234 (ε 15 600); νmax (Nujol)/cmϪ1 2149
᎐
(C᎐N), 1752 and 1733 (ester C᎐O), 1700 (vinylogous carbonate
᎐
᎐
C᎐O) and 1648 (C᎐C); δ (300 MHz; CDCl3) 2.03, 2.04 and
᎐
᎐
H
2.09 (3, 3 and 6 H, each s, 4 × MeCO2), 3.63 and 4.03 (each 1 H,
d, J 13, 2-CH2S), 3.80 (3 H, s, MeO2C), 3.83 (1 H, ddd, J 2.5, 4.5
and 9.5, 5Ј-H), 4.16 and 4.30 [each 1 H, dd (J 2.5 and 12.5) and
dd (J 4.5 and 12.5), 6Ј-H2], 4.99 (1 H, d, J 7.5, 1ЈH), 5.14 (1 H, t,
J 9.5, 4Ј-H), 5.18 (1 H, dd, J 7.5 and 9.5, 2Ј-H), 5.27 (1 H, t, J 9,
3Ј-H) and 7.69 (1 H, s, 3-H); m/z (FAB) 526 [M(Na)ϩ, 11%], 331
(C14H19O9ϩ, 75) and 169 (100).
Reactions of allylic bromides with potassium thiocyanate
General procedure. A mixture of the allylic bromide (0.5
mmol), potassium thiocyanate (0.049 g, 0.5 mmol) and dry
acetonitrile (25 cm3) was stirred until the reaction was complete
(TLC). Evaporation of the solvent left a residue, which was
partitioned between methylene dichloride and 1% aq. sodium
metabisulfite. After having been washed with water, the organic
phase was dried (MgSO4) and concentrated. The product was
Reaction of the allylic bromide 14a with silver(I) thiocyanate
A mixture of the allylic bromide 14a (0.051 g, 0.1 mmol),
silver() thiocyanate (0.0166 g, 0.1 mmol) and dry acetonitrile
(5 cm3) was stirred. At intervals, aliquots (≈1 cm3) were removed
and concentrated; the residue was then partitioned between
methylene dichloride and water. The material, obtained after
evaporation of the dried (MgSO4) organic phase, was analysed
by 300 MHz 1H NMR spectroscopy. After 3 h, mainly an 89:11
mixture of compounds 14a and 17a was present; the ratio
changed to 74:26 after 6 h, 25:75 after 24 h and 3:97 after 48 h.
1
analysed by 300 or 400 MHz H NMR spectroscopy and then
purified in the manner described.
(E)-4-(2Ј,3Ј,4Ј,6Ј-Tetra-O-acetyl-ꢀ-D-glucopyranosyloxy)-
3-(thiocyanatomethyl)but-3-en-2-one 17a. The product obtained
from the reaction of the allylic bromide 14a (0.255 g, 0.5 mmol)
for 6 h was predominantly the thiocyanate 17a. Crystallisation
of the material from ethyl acetate–light petroleum gave the title
compound 17a (0.185 g, 76%); mp 152–152.5 ЊC; [α]D ϩ33 (c
0.4, CHCl3) (Found: C, 49.4; H, 5.5; N, 2.7; S, 6.8. C20H25NO11S
requires C, 49.3; H, 5.2; N, 2.9; S, 6.6%); λmax (EtOH)/nm 242
Reactions of allylic bromides with sodium acetate
General procedure. A mixture of the allylic bromide (0.5
mmol), dry sodium acetate (0.369 g, 1.5 mmol) and dry
acetonitrile (25 cm3) was heated under reflux for the time speci-
fied. The solvent was then evaporated and the residue was par-
titioned between methylene dichloride and water. After having
been washed with water, the organic phase was dried (MgSO4)
and concentrated. The product was analysed by 300 or 400
(ε 12 400), νmax (Nujol)/cmϪ1 2153 (C᎐N), 1748 (ester C᎐O),
᎐
᎐
᎐
1668 (vinylogous ester C᎐O) and 1642 (C᎐C); δ (300 MHz;
᎐
᎐
H
1
CDCl3) 2.03, 2.04, 2.09 and 2.10 (each 3 H, s, 4 × MeCO2), 2.31
(3 H, s, 1-H3), 3.64 and 3.93 (each 1 H, d, J 12.5, 3-CH2S), 3.86
(1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.17 and 4.30 [each 1 H, dd
(J 2.5 and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 5.05 (1 H, d, J
7.5, 1Ј-H), 5.15 (1 H, t, J 10, 4Ј-H), 5.20 (1 H, dd, J 7.5 and 9,
2Ј-H), 5.29 (1 H, t, J 9.5, 3Ј-H) and 7.63 (1 H, s, 4-H); δC (75
MHz; CDCl3) 20.43, 20.58 and 20.61 (4 × CH3CO), 25.17 (1-
CH3), 26.09 (3-CH2S), 61.28 (6Ј-CH2), 67.61, 70.23, 71.84 and
72.73 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 100.2 (1Ј-CH), 112.2 (SCN),
119.2 (3-C), 156.4 (4-CH), 169.2, 169.4, 169.9 and 170.4
(4 × MeCO) and 194.0 (2-CO); m/z (FAB) 510 [M(Na)ϩ, 4%],
331 (C14H19O9ϩ, 100) and 169 (90).
MHz H NMR spectroscopy and then purified in the manner
described.
Reaction involving the allylic bromide 14a. Method (a).—A
mixture of the allylic bromide 14a (0.102 g, 0.2 mmol), dry
sodium acetate (0.016 g, 0.2 mmol) and dry acetonitrile (10
cm3) was heated under reflux. At intervals, aliquots (≈1 cm3)
were removed, worked up and analysed. After 3 h (when ≈60%
of unchanged 14a remained), the product comprised mainly a
6:79:15 mixture of compounds 18a, 19a and 20a [the propor-
tions were estimated from the integrals of the signals at δ 7.53
(attributed to the 4-H of 18a), 6.79 (assigned to the 1Љ-H of 19a)
and 6.85 (ascribed to the 1Љ-H of 20a)]. After 6 h (when ≈35%
of unchanged 14a was present), the proportions were unaltered.
After 24 h (when no 14a was detected), the proportions of
compounds 18a, 19a and 20a were 60:26:14. Finally, after
48 h, the product comprised mainly a 75:12:13 mixture of
compounds 18a, 19a and 20a.
Method (b).—(i) The reaction involving the allylic bromide
14a (0.255 g, 0.5 mmol) using the general procedure gave rise,
after 3 h, to a product that comprised mainly a 17:67:16 mix-
ture of the acetoxy derivatives 18a, 19a and 20a. Subjection of
the mixture to HPLC [EtOAc–hexanes (2:1) as eluent] gave two
fractions.
The first-eluted fraction (0.144 g, 59%), isolated as a colour-
less syrup, was identified as an 80:20 mixture of (1ЉS)-3-[1Љ-
acetoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)-
(E)-1-(2Ј,3Ј,4Ј,6Ј-Tetra-O-acetyl-ꢀ-D-glucopyranosyloxy)-2-
(thiocyanatomethyl)pent-1-en-3-one 17b. The product obtained
from the reaction of the allylic bromide 14b (0.262 g, 0.5 mmol)
for 7 h was predominantly the thiocyanate 17b. Crystallisation
of the material from ethyl acetate–light petroleum gave the title
compound 17b (0.180 g, 72%); mp 151–152 ЊC; [α]D ϩ33 (c 0.4,
CHCl3) (Found: C, 50.5; H, 5.7; N, 2.7; S, 6.8. C21H27NO11S
requires C, 50.3; H, 5.4; N, 2.8; S, 6.4%); λmax (EtOH)/nm 243
(ε 17 200); νmax (Nujol)/cmϪ1 2153 (C᎐N), 1756 (ester C᎐O),
᎐
᎐
᎐
1670 (vinylogous ester C᎐O) and 1645 (C᎐C); δ (300 MHz;
᎐
᎐
H
CDCl3) 1.15 (3 H, t, J 7.5, 5-H3), 2.04, 2.05, 2.10 and 2.11 (each
3 H, s, 4 × MeCO2), 2.64 (2 H, q, J 7.5, 4-H2), 3.66 and 3.96
(each 1 H, d, J 12.5, 2-CH2S), 3.86 (1 H, ddd, J 2.5, 4.5 and 10,
5Ј-H), 4.18 and 4.31 [each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
1759

View Article Online
methyl]but-3-en-2-one 19a and its (1ЉR)-isomer 20a. After two
crystallisations from diethyl ether–hexanes, the sample (0.104 g,
43%) (now as an 86:14 mixture of 19a and 20a) showed mp
123–124 ЊC; [α]D Ϫ50 (c 0.2, CHCl3) (Found: C, 51.3; H, 5.8.
C21H28O13 requires C, 51.6; H, 5.8%); λmax (EtOH)/nm 210 (ε
δH (300 MHz; CDCl3) 1.07 and 1.09 (0.48 and 2.52 H, each t,
J 7.5, 5-H3), 1.99, 2.00, 2.01, 2.020, 2.024, 2.04, 2.07, 2.09 and
2.11 (0.48, 2.52, 0.48, 2.52, 0.48, 2.52, 5.04, 0.48 and 0.48 H,
each s, 5 × MeCO2), 2.64–2.80 (2 H, m, 4-H2), 3.66 and 3.72
[0.16 and 0.84 H, dt (J 10 and 3) and ddd (J 2.5, 5 and 10),
5Ј-H], 4.08, 4.12–4.15 and 4.27 [0.84, 0.32 and 0.84 H, dd (J 2.5
and 12.5), m and dd (J 5 and 12.5), 6Ј-H2], 4.88 (0.84 H, d, J 8,
0.84 × 1Ј-H), 4.97–5.10 (2.16 H, m, 2Ј- and 4Ј-H and 0.16 ×
1Ј-H), 5.22 (1 H, t, J 9.5, 3Ј-H), 6.21, 6.27, 6.28 and 6.33 (0.16,
0.16, 0.84 and 0.84 H, each s, 1-H2) and 6.80 and 6.86 (0.84
and 0.16 H, each s, 1Љ-H); m/z (FAB) 525 [M(Na)ϩ, 5%), 331
(C14H19O9ϩ, 50) and 169 (100).
8900); νmax (Nujol)/cmϪ1 1750 and 1737 (ester C᎐O) and 1676
᎐
(enone C᎐O); δ (300 MHz; CDCl ) 2.00, 2.01, 2.02, 2.04, 2.08,
᎐
H
3
2.10 and 2.11 (0.4, 3, 3, 2.6, 5.2, 0.4 and 0.4 H, each s, 5 ×
MeCO2), 2.34 and 2.35 (0.4 and 2.6 H, each s, 1-H3), 3.66 and
3.72 [0.14 and 0.86 H, dt (J 10 and 3) and ddd (J 2.5, 5 and 10),
5Ј-H], 4.09, 4.13–4.15 and 4.27 [0.86, 0.28 and 0.86 H, dd (J 2.5
and 12.5), m and dd (J 5 and 12.5), 6Ј-H2], 4.89 and 4.96 (0.86
and 0.14 H, each d, J 8, 1Ј-H), 5.00–5.10 (2 H, m, 2Ј- and 4Ј-H),
5.22 (1 H, t, J 9.5, 3Ј-H), 6.23, 6.30, 6.33 and 6.38 (0.14, 0.86,
Reaction involving the allylic bromide 14d. Method (a).—A
mixture of the allylic bromide 14d (0.054 g, 0.1 mmol), sodium
acetate (0.0164 g, 0.2 mmol) and dry acetonitrile (5 cm3) was
heated under reflux. At intervals, aliquots (≈1 cm3) were
removed, worked up and analysed. After 6 h (when 22% of 14d
remained), the product comprised mainly a 22:58:20 mixture
of the acetoxy derivatives 18d, 19d and 20d [the composition
was estimated from the integrals of the signals at δ 7.60 (attrib-
uted to the 3-H of 18d), 6.20 (assigned to an olefinic H of 19d)
and 6.14 (ascribed to an olefinic H of 20d)]. After 180 h, the
proportions of compounds 18d, 19d and 20d were 56:26:18.
Method (b).—The reaction involving the allylic bromide 14d
(0.269 g, 0.5 mmol) using the general procedure gave rise, after
6.5 h, to a product comprising 25% unchanged 14d and a
32:52:16 mixture of compounds 18d, 19d and 20d. Subjection
of the mixture of column chromatography (Et2O as eluent) gave
three main fractions.
0.14 and 0.86 H, each s, 4-H2) and 6.79 and 6.85 (0.86 and 0.14
ϩ
H, each s, 1Љ-H); m/z (FAB) 511 [M(Na)ϩ, 7%], 331 (C14H19O9
,
60) and 169 (100).
The second-eluted fraction (0.036 g, 15%), isolated as a
colourless syrup, was identified as (E)-3-acetoxymethyl-4-(2Ј,3Ј,
4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)but-3-en-2-one 18a.
After crystallisation from ethyl acetate–hexanes, the sample
(0.026 g, 11%) showed mp 103–104 ЊC; [α]D Ϫ8 (c 0.5, CH2Cl2)
(Found: C, 51.4; H, 5.8. C21H28O13 requires C, 51.6; H, 5.8%);
λmax (EtOH)/nm 201 (ε 1900), 239 (20 200) and 311 (1500);
νmax (KBr)/cmϪ1 1755 and 1740 (ester C᎐O), 1670 (vinyl-
᎐
ogous ester C᎐O) and 1650 (C᎐C); δ (300 MHz; CDCl3)
᎐
᎐
H
2.02, 2.03, 2.04, 2.06 and 2.10 (each 3 H, s, 5 × MeCO2), 2.28
(3 H, s, 1-H3), 3.86 (1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.17
and 4.30 [each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5),
6Ј-H2], 4.73 and 4.87 (each 1 H, d, J 11.5, 3-CH2O), 5.00 (1 H,
d, J 7.5, 1Ј-H), 5.13–5.29 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.53
(1 H, s, 4-H); δC (75 MHz; CDCl3) 20.62, 20.68, 20.82, 20.97
and 21.19 (5 × CH3CO), 26.27 (1-CH3), 55.67 (3-CH2), 61.57
(6Ј-CH2), 67.79, 70.65, 72.20 and 72.93 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH),
100.7 (1Ј-CH), 119.2 (3-C), 157.0 (4-CH), 169.1, 169.4, 170.3,
170.6 and 170.8 (5 × MeCO) and 195.9 (2-CO); m/z (FAB) 527
[M(K)ϩ, 1%], 511 [M(Na)ϩ, 7], 489 (MHϩ, 1) and 331
(C14H19O9ϩ, 100).
The first-eluted fraction (0.090 g) comprised 23% unchanged
14d and an 80:20 mixture of the acetoxy derivatives 19d and
20d.
The second-eluted fraction (0.120 g) comprised 27%
unchanged 14d and a 32:49:19 mixture of the acetoxy deriv-
atives 18d, 19d and 20d.
The third-eluted fraction (0.020 g, 8%) was ethyl (E)-2-
acetoxymethyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranos-
yloxy)prop-2-enoate 18d; [α]D Ϫ16 (c 0.5, CH2Cl2); νmax
(film)/cmϪ1 1750 (ester C᎐O), 1720 (vinylogous carbonate C᎐O)
(ii) The aforecited reaction was repeated and the product was
subjected to column chromatography (Et2O as eluent). One
main fraction (0.105 g, 43%) was collected which was an 80:20
mixture of compounds 19a and 20a.
᎐
᎐
and 1660 (C᎐C); δ (300 MHz; CDCl3) 1.30 (3 H, t, J 7,
᎐
H
MeCH2), 2.04, 2.05, 2.08 and 2.12 (6, 3, 3 and 3 H, each s,
5 × MeCO2), 3.86 (1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.18 and
4.31 [each 1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5),
6Ј-H2], 4.24 (2 H, q, J 7, OCH2Me), 4.76 and 4.86 (each 1 H, d,
J 11.5, 2-CH2O), 4.97 (1 H, d, J 7.5, 1Ј-H), 5.13–5.30 (3 H, m,
2Ј-, 3Ј- and 4Ј-H) and 7.60 (1 H, s, 3-H); m/z (FAB) 331
(C14H19O9ϩ, 65%), 169 (85) and 109 (100) {(after addition of
KI) 557 [M(K)ϩ, 100%]}.
Reaction involving the allylic bromide 14b. Method (a).—A
mixture of the allylic bromide 14b (0.105 g, 0.2 mmol), dry
sodium acetate (0.033 g, 0.4 mmol) and dry acetonitrile (10
cm3) was heated under reflux. At intervals, aliquots (≈1 cm3)
were removed, worked up and analysed. After 3 h (when ≈30%
of 14b remained), the product comprised mainly a 10:71:19
mixture of the acetoxy derivatives 18b, 19b and 20b [the propor-
tions were estimated from the integrals of the signals at δ 7.53
(ascribed to the 1-H of 18b), 6.80 (attributed to the 1Љ-H of 19b)
and 6.86 (assigned to the 1Љ-H of 20b)]. After 6 h (when 14b was
absent), the proportions were 18:64:18. After 24 h, the propor-
tions were 49:35:16. Finally, after 96 h, the product comprised
mainly a 73:12:15 mixture of compounds 18b, 19b and 20b.
Method (b).—The reaction involving the allylic bromide 14b
(0.262 g, 0.5 mmol) using the general procedure gave rise, after
3 h, to a product that contained mainly a 10:75:15 mixture of
compounds 18b, 19b and 20b (≈30% of 14b remained). Subjec-
tion of the mixture to column chromatography (Et2O as eluent)
led to the isolation of one main fraction (0.126 g, 50%), identi-
fied as an 84:16 mixture of (1ЉS)-2-[1Љ-acetoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-
tetra-O-acetyl-β--glucopyranosyloxy)-methyl]pent-1-en-3-one
19b and its (1ЉR)-isomer 20b. After crystallisation from diethyl
ether–light petroleum, the sample (0.080 g, 32%) (still as an
84:16 mixture of 19b and 20b) showed mp 104–106 ЊC; [α]D
Ϫ37 (c 0.25, CHCl3) (Found: C, 52.9; H, 5.9. C22H30O13 requires
C, 52.6; H, 6.0%); λmax (EtOH)/nm 211 (ε 8900); νmax (Nujol)/
cmϪ1 1744 (ester C᎐O), 1677 (enone C᎐O) and 1638 (C᎐C);
Equilibration of the allylic acetates 18a, 19a and 20a. Method
(a).—A mixture of the acetoxy compound 18a (0.005 g, 0.01
mmol), sodium acetate (0.0008 g, 0.01 mmol) and dry
acetonitrile (1 cm3) was heated under reflux for 18 h and then
the solvent was evaporated. The residue was partitioned
between water and methylene dichloride and the organic phase
was dried (MgSO4) and concentrated to leave mainly a
74:12:14 mixture of compounds 18a, 19a and 20a.
Method (b).—A solution of a 3:90:7 mixture of the allylic
acetates 18a, 19a and 20a (0.015 g, 0.03 mmol) in acetic acid
(1.5 cm3) was stirred in the dark. At intervals, aliquots (≈0.5
cm3) were removed, worked up [CH2Cl2 was added to the solu-
tion which, after having been washed successively with aq.
NaHCO3 and water, was dried (MgSO4) and concentrated] and
analysed. Compounds 18a, 19a and 20a were present in propor-
tions of 60:35:5 after 24 h, 77:16:7 after 48 h and 81:8:11
after 96 h.
The reaction of allylic bromide 14a (0.015 g, 0.03 mmol) with
silver() oxide and acetic acid was conducted simultaneously
under similar conditions. The products comprised compounds
᎐
᎐
᎐
1760
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765

View Article Online
18a, 19a and 20a in proportions of 55:28:17 after 24 h,
71:15:14 after 48 h and 78:8:14 after 96 h.
21.18 and 21.29 (5 × CH3CO), 26.24 and 26.29 (1-CH3), 61.78
and 61.83 (6Ј-CH2), 68.19, 68.42, 71.03, 71.08, 72.29, 72.38,
72.66 and 72.75 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 89.81 and 92.24 (1Љ-
CH), 98.44 and 102.5 (1Ј-CH), 127.5 and 128.9 (4-CH2), 143.6
and 143.7 (3-C), 169.51, 169.54, 169.63, 169.66, 169.8, 170.2,
170.3 and 170.8 (5 × MeCO), and 197.0 (2-CO). After crystal-
lisation from diethyl ether–hexanes, the sample (0.042 g, 17%)
(now as a 44:56 mixture of 19a and 20a) showed mp 99–100 ЊC;
[α]D Ϫ36 (c 0.25, CH2Cl2).
The second-eluted fraction (0.124 g, 51%), isolated as a
colourless syrup, was identified as the acetoxy derivative 18a.
After crystallisation from ethyl acetate–hexanes, the sample
(0.104 g, 43%) showed mp 103–104 ЊC; [α]D Ϫ8 (c 0.5, CH2Cl2).
Reactions of allylic bromides with silver(I) acetate
General procedure. A mixture of the allylic bromide (0.5
mmol), silver() acetate (0.084 g, 0.5 mmol) and dry acetonitrile
(25 cm3) was stirred for the time specified. The solvent was then
evaporated and the residue was partitioned between methylene
dichloride and water. After having been washed with water, the
organic phase was dried (MgSO4) and concentrated. The prod-
1
uct was analysed by 300 or 400 MHz H NMR spectroscopy
and then purified in the manner described.
Reaction involving the allylic bromide 14a. (i) From the
reaction involving the allylic bromide 14a (0.051 g, 0.1 mmol),
aliquots (≈1 cm3) were removed, worked up and analysed at
intervals. After 3 h (when no 14a remained), mainly a 3:86:11
mixture of compounds 18a, 19a and 20a was present. After 6 h,
the proportions of compounds 18a, 19a and 20a were 6:83:11.
After 24 h, a 14:75:11 mixture of compounds 18a, 19a and
20a was present. Finally, after 48 h, the proportions of com-
pounds 18a, 19a and 20a were 23:64:13.
(ii) The reaction involving the allylic bromide 14a (0.255 g,
0.5 mmol) for 3 h gave rise to a product that, after crystallis-
ation from diethyl ether–hexanes, comprised a 5:91:4 mixture
of compounds 18a, 19a and 20a (0.098 g, 40%).
Reactions of allylic bromides with alcohols in the presence of
silver(I) oxide
General procedure. A suspension of silver() oxide (0.255 g,
1.1 mmol) in the alcohol (50 cm3) was stirred in the dark for 1.5
h and then the allylic bromide (1 mmol) was added. After 24 h,
the mixture was diluted with methylene dichloride and filtered
through a pad of Celite. The filtrate was washed successively
with brine and water, dried (MgSO4) and concentrated. Follow-
1
ing analysis by 300 or 400 MHz H NMR spectroscopy, the
product was purified in the manner described.
Reaction involving the allylic bromide 14a and methanol.
(i) From the reaction involving the allylic bromide 14a (0.102 g,
0.2 mmol), aliquots (≈1 cm3) were removed, worked up and
analysed at intervals. After 2 h, compound 14a was essentially
depleted and mainly a 7:67:26 mixture of compounds 23a, 24a
and 25a was present [the proportions were estimated from the
integrals of the signals at δ 7.50 (attributed to the 4-H of 23a),
5.42 (assigned to the 1Љ-H of 24a) and 5.70 (ascribed to the 1Љ-H
of 25a)]. Although the proportions remained unaltered over
120 h, new signals attributable to the dimethoxy derivative 26a
[δ 7.39 (4-H)] and to the tetraacetate 27 {as a 2:1 mixture of
α- and β-anomers [δ 5.23 (3-H of α-anomer) and 5.53 (3-H of
β-anomer)]} grew in intensity (the ratio of 23a and 26a was
≈1:1 after 24 h and ≈1:3 after 120 h).
Reaction involving the allylic bromide 14d. (With A.
Schofield.)—The reaction involving the allylic bromide 14d
(0.270 g, 0.5 mmol) for 2.5 h gave rise to a product that com-
prised mainly a 5:87:8 mixture of the acetoxy derivatives 18d,
19d and 20d. Crystallisation of the mixture from diethyl ether
gave ethyl (1ЉS)-2-[1Љ-acetoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β-
-glucopyranosyloxy)methyl]prop-2-enoate 19d (0.107 g, 41%);
mp 96–98 ЊC; [α]D Ϫ48 (c 0.77, CH2Cl2) (Found: C, 50.7; H, 5.7.
C22H30O14 requires C, 51.0; H, 5.8%); νmax (KBr)/cmϪ1 1765 and
1750 (ester C᎐O) and 1715 (unsat. ester C᎐O); δ (400 MHz;
᎐
᎐
H
CDCl3) 1.28 (3 H, t, J 7, MeCH2), 2.01, 2.02, 2.03, 2.08 and 2.09
(each 3 H, s, 5 × MeCO2), 3.73 (1 H, ddd, J 2, 4.5 and 10, 5Ј-H),
4.11 (1 H, dd, J 2 and 12, 6Ј-H), 4.15–4.31 (3 H, m, 6Ј-H and
OCH2Me), 4.86 (1 H, d, J 8, 1Ј-H), 5.05 (1 H, dd, J 8 and 9.5,
2Ј-H), 5.09 (1 H, t, J 10, 4Ј-H), 5.22 (1 H, t, J 9.5, 3Ј-H), 6.20
and 6.46 (each 1 H, s, 3-H2) and 6.78 (1 H, s, 1Љ-H); δC (100
MHz; CDCl3) 14.4 (CH3CH2), 20.9, 21.0 and 21.2 (4 ×
CH3CO), 61.3 and 62.0 (OCH2Me and 6Ј-CH2), 68.6, 71.3, 72.5
and 73.0 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 90.0 (1Љ-CH), 98.3 (1Ј-CH),
129.4 (3-CH2), 136.3 (2-C), 164.6 (1-CO) and 169.6, 169.8, 170.5
and 171.0 (5 × MeCO); m/z (FAB) 331 (C14H19O9ϩ, 55), 169
(100) and 109 (70) {(after addition of KI) 557 [M(K)ϩ, 85%]}.
(ii) The product obtained from the reaction of the allylic
bromide 14a (0.509 g, 1.0 mmol) was subjected to HPLC
[EtOAc–hexanes (2:1) as eluent] to give three fractions.
The first-eluted fraction (0.302 g, 66%), isolated as a colour-
less syrup, was identified as a 70:30 mixture of compounds 24a
and 25a; δH (300 MHz; CDCl3 (inter alia for 25a) 2.35 (3 H, s,
1-H3), 3.25 (3 H, s, MeO), 4.82 (1 H, d, J 8, 1Ј-H), 5.70 (1 H, s,
1Љ-H) and 6.24 and 6.29 (each 1 H, s, 4-H2). Crystallisation of
the mixture from diethyl ether–hexanes gave (1ЉR)-1Љ-methoxy-
3-[1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)methyl]-
but-3-en-2-one 24a (0.118 g, 26%); mp 113–114 ЊC; [α]D Ϫ68 (c
0.5, CH2Cl2) (Found: C, 52.5; H, 5.8. C20H28O12 requires C,
52.2; H, 6.1%); λmax (EtOH)/nm 211 (ε 6800); νmax (KBr)/cmϪ1
Reaction of the allylic bromide 14a with acetic acid in the
presence of silver(I) oxide
(i) Silver() oxide (0.025 g, 0.11 mmol) was added to stirred
acetic acid (5 cm3) in the dark followed, after 1.5 h, by the allylic
bromide 14a (0.051 g, 0.1 mmol). At intervals, aliquots (≈1 cm3)
were removed, worked up [the sample was diluted with CH2Cl2
and filtered through a pad of Celite; the filtrate was then
washed successively with saturated aq. NaHCO3 and water,
dried (MgSO4) and concentrated] and analysed. After 10 min, a
5:71:24 mixture of compounds 18a, 19a and 20a was present.
The proportions changed to 9:67:24 after 30 min, 26:52:22
after 3 h and 72:12:16 after 18 h.
1740 (ester C᎐O) and 1670 (enone C᎐O); δ (300 MHz; CDCl )
᎐ ᎐
H 3
1.992, 1.993, 2.02 and 2.07 (each 3 H, s, 4 × MeCO2), 2.34 (3 H,
s, 1-H3), 3.46 (3 H, s, MeO), 3.68 (1 H, ddd, J 3, 5 and 9.5,
5Ј-H), 4.14 and 4.19 [each 1 H, dd (J 3 and 12) and dd (J 5 and
12), 6Ј-H2], 4.69 (1 H, d, J 8, 1Ј-H), 4.99–5.09 (2 H, m, 2Ј- and
4Ј-H), 5.19 (1 H, t, J 9.5, 3Ј-H), 5.42 (1 H, s, 1Љ-H) and 6.16 and
6.19 (each 1 H, s, 4-H2); δC (75 MHz; CDCl3) 20.72 and 20.82
(4 × CH3CO), 26.51 (1-CH3), 56.17 (CH3O), 62.17 (6Ј-CH2),
68.55, 71.35, 72.09 and 73.06 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 97.62
and 100.0 (1Ј- and 1Љ-CH), 126.4 (4-CH2), 145.4 (3-C), 169.2,
(ii) The aforecited reaction of the allylic bromide 14a (0.255
g, 0.5 mmol) was repeated and the product, obtained after 18 h,
was subjected to HPLC [EtOAc–hexanes (2:1) as eluent] to give
two fractions.
The first-eluted fraction (0.056 g, 23%), isolated as a colour-
less syrup, was identified as a 50:50 mixture of compounds 19a
and 20a; δC (75 MHz; CDCl3) 20.69, 20.72, 20.83, 20.90, 21.01,
169.6, 170.4 and 170.7 (4 × MeCO) and 197.9 (2-CO); m/z
ϩ
(FAB) 483 [M(Na)ϩ, 5%], 385 (C17H21O10ϩ, 5), 331 (C14H19O9
,
100) and 169 (25).
The second-eluted fraction (0.026 g, 6%), isolated as a colour-
less syrup, was identified as (E)-3-methoxymethyl-4-(2Ј,3Ј,4Ј,
6Ј-tetra-O-acetyl-β--glucopyranosyloxy)-but-3-en-2-one 23a.
After crystallisation from ethyl acetate–hexanes, the sample
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
1761

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(0.020 g, 4%) showed mp 121–122 ЊC; [α]D Ϫ16 (c 0.25, CH2Cl2)
(Found: C, 52.1; H, 5.8%); λmax (EtOH)/nm 239 nm (ε 15 300);
(KBr)/cmϪ1 1760 and 1740 (ester C᎐O), 1690 (vinylogous ester
᎐
C᎐O) and 1610 (C᎐C); δH (300 MHz; CDCl3) 1.17 (3 H, t, J 7,
᎐
᎐
νmax (Nujol)/cmϪ1 1755 and 1742 (ester C᎐O), 1662 (vinylogous
MeCH2), 2.03, 2.040, 2.042 and 2.09 (each 3 H, s, 4 × MeCO2),
2.29 (3 H, s, 1-H3), 3.45 (2 H, q, J 7, OCH2Me), 3.83 (1 H, ddd,
J 2, 4.5 and 10, 5Ј-H), 4.14 and 4.29 [each 1 H, dd (J 2.5 and
12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 4.19 (2 H, s, 3-CH2O), 4.94
(1 H, d, J 7.5, 1Ј-H), 5.11–5.29 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and
7.47 (1 H, s, 4-H); δC (75 MHz; CDCl3) 15.28 (CH3CH2), 20.59,
20.65 and 20.78 (4 × CH3CO), 26.75 (1-CH3), 61.30, 61.57 and
65.79 (6Ј-CH2, 3-CH2 and OCH2Me), 67.82, 70.63, 72.23 and
72.77 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 100.9 (1Ј-CH), 120.6 (3-C), 156.0
(4-CH), 169.1, 169.4, 170.2 and 170.6 (4 × MeCO) and 197.4
(2-CO); m/z (FAB) 497 [M(Na)ϩ, 6%], 475 (MHϩ, 18), 331
(C14H19O9ϩ, 100), 169 (53), 109 (22) and 43 (C2H3Oϩ, 53).
(ii) The product obtained from the reaction of the allylic
bromide 14a (0.255 g, 0.5 mmol) was subjected to column
chromatography [EtOAc–light petroleum (2:1) as eluent]. One
main fraction (0.142 g, 60%) was obtained; it comprised largely
a 67:33 mixture of the ethoxy derivatives 24b and 25b.
᎐
ester C᎐O) and 1645 (C᎐C); δH (300 MHz; CDCl3) 2.03, 2.041,
᎐
᎐
2.043 and 2.09 (each 3 H, s, 4 × MeCO2), 2.28 (3 H, s, 1-H3),
3.28 (3 H, s, MeO), 3.84 (1 H, ddd, J 2, 4.5 and 10, 5Ј-H),
4.14 (2 H, s, 3-CH2O), 4.15 and 4.29 [each 1 H, dd (J 2.5 and
12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 4.94 (1 H, d, J 7.5,
1Ј-H), 5.12–5.30 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.50 (1 H, s,
4-H); m/z (FAB) 791 [M(C14H19O9)ϩ, 12%], 483 [M(Na)ϩ, 78],
462 (MH2ϩ, 24), 461 (MHϩ, 95), 331 (C14H19O9ϩ, 100), 169 (90)
and 109 (64).
The third-eluted fraction (0.010 g, ≈7%), isolated as a col-
ourless syrup, was mainly (E)-4-methoxy-3-(methoxymethyl)-
but-3-en-2-one 26a; λmax (EtOH)/nm 249 (ε 11 400); δH (300
MHz; CDCl3) inter alia 2.26 (3 H, s, 1-H3), 3.33 (3 H, s,
MeOCH2), 3.92 (3 H, s, 4-MeO), 4.17 (2 H, s, 3-CH2O) and 7.39
(1 H, s, 4-H); m/z (FAB) 146 (MH2ϩ, 46%), 129 [(M Ϫ CH3)ϩ,
100] and 113 [(M Ϫ CH3O)ϩ, 94].
(iii) The product obtained from the reaction of the allylic
bromide 14a (0.509 g, 1.0 mmol) was subjected to column
chromatography [EtOAc–light petroleum (2:1) as eluent] to
give two fractions.
The first-eluted fraction (0.253 g, 55%), isolated as a colour-
less syrup, was a 65:35 mixture of the methoxy derivatives 24a
and 25a. Crystallisation of the mixture from diethyl ether–light
petroleum gave compound 24a (0.115 g, 25%).
Reaction involving the allylic bromide 14a and propan-1-ol. (i)
The reaction involving the allylic bromide 14a (0.509 g, 1.0
mmol) gave rise to a product that comprised mainly a 13:62:25
mixture of the propoxy derivatives 23c, 24c and 25c [the pro-
portions were estimated from the integrals of the signals at
δ 7.47 (attributed to the 4-H of 23c), 5.50 (assigned to the 1Љ-H
of 24c) and 5.73 (ascribed to the 1Љ-H of 25c)]. Subjection of
the mixture to HPLC [EtOAc–hexanes (2:1) as eluent] led to
the isolation of two fractions.
The second-eluted fraction (0.032 g, 7%) [0.019 g, 4% (after
crystallisation from EtOAc–light petroleum)] was compound
23a.
The first-eluted fraction (0.322 g, 66%), isolated as a colour-
less syrup, was identified as a 72:28 mixture of (1ЉR)-3-[1Љ-
propoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)-
methyl]but-3-en-2-one 24c and its (1ЉS)-isomer 25c. After crys-
tallisation from diethyl ether–hexanes, the sample (0.176 g, 36%)
(still as a 72:28 mixture of 24c and 25c) showed mp 98–100 ЊC;
[α]D Ϫ46 (c 0.5, CH2Cl2) (Found: C, 54.3; H, 6.9. C22H32O12
requires C, 54.1; H, 6.6%); λmax (EtOH)/nm 211 (ε 6600); νmax
(KBr)/cmϪ1 1745 (ester C᎐O) and 1675 (enone C᎐O); δ (300
Reaction involving the allylic bromide 14a and ethanol. (i) The
reaction involving the allylic bromide 14a (0.509 g, 1.0 mmol)
gave rise to a product that comprised mainly an 11:72:17 mix-
ture of the ethoxy derivatives 23b, 24b and 25b [the proportions
were estimated from the integrals of the signals at δ 7.47
(attributed to the 4-H of 23b), 5.51 (assigned to the 1Љ-H of
24b) and 5.72 (ascribed to the 1Љ-H of 25b)]. Subjection of the
mixture to HPLC [EtOAc–hexanes (2:1) as eluent] led to the
isolation of two fractions.
᎐
᎐
H
MHz; CDCl3) 0.89 and 0.91 (0.84 and 2.16 H, each t, J 7.5,
MeCH2), 1.52–1.66 (2 H, m, MeCH2), 1.99, 2.01, 2.02, 2.03,
2.07 and 2.08 (4.32, 0.84, 3.00, 0.84, 0.84 and 2.16 H, each s,
4 × MeCO2), 2.33 and 2.34 (2.16 and 0.84 H, each s, 1-H3),
3.36–3.48 and 3.73–3.81 [each 1 H, m and dt (J 9.5 and 6.5),
OCH2Et], 3.63–3.71 (1 H, m, 5Ј-H), 4.08, 4.14–4.16 and 4.21
[0.28, 1.44 and 0.28 H, dd (J 2 and 12), m and dd (J 5 and 12),
6Ј-H2], 4.70 and 4.83 (0.72 and 0.28 H, each d, J 8, 1Ј-H), 4.98–
5.10 (2 H, m, 2Ј- and 4Ј-H), 5.19 and 5.23 (0.72 and 0.28 H,
each t, J 9.5, 3Ј-H), 5.50 and 5.73 (0.72 and 0.28 H, each s, 1Љ-H)
and 6.14, 6.20, 6.23 and 6.25 (0.72, 0.72, 0.28 and 0.28 H, each
s, 4-H2); δC (75 MHz; CDCl3) 10.66 and 10.71 (CH3CH2 of 24c
and 25c), 20.73 and 20.83 (4 × CH3CO), 22.80 and 22.90
(CH3CH2 of 24c and 25c), 26.56 and 26.59 (1-CH3 of 25c and
24c), 61.99 and 62.22 (6Ј-CH2 of 25c and 24c), 67.80 and 70.55
(OCH2Et of 25c and 24c), 68.51, 68.55, 71.24, 71.35, 72.06,
72.98 and 73.11 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 95.83, 96.32, 97.48
and 98.76 (1Ј- and 1Љ-CH), 126.1 and 128.2 (4-CH2 of 24c and
25c), 144.5 and 145.7 (3-C of 25c and 24c), 169.2, 169.3, 169.6,
170.4, 170.7 and 170.8 (4 × MeCO) and 197.7 and 198.0 (2-CO
The first-eluted fraction (0.334 g, 70%), isolated as a colour-
less syrup, was identified as an 81:19 mixture of compounds
24b and 25b; δH (300 MHz; CDCl3) (inter alia for 25b) 2.34 (3 H,
s, 1-H3), 4.82 (1 H, d, J 8, 1Ј-H), 5.72 (1 H, s, 1Љ-H) and 6.24 and
6.25 (each 1 H, s, 4-H2). Crystallisation of the mixture from
diethyl ether–hexanes gave (1ЉR)-1Љ-ethoxy-3-[1Љ-(2Ј,3Ј,4Ј,6Ј-
tetra-O-acetyl-β--glucopyranosyloxy)methyl]but-3-en-2-one
24b (0.104 g, 22%); mp 105–106 ЊC; [α]D Ϫ56 (c 0.25, CH2Cl2)
(Found: C, 52.9; H, 6.3. C21H30O12 requires C, 53.2; H, 6.4%);
λmax (EtOH)/nm 211 (ε 6900); νmax (KBr)/cmϪ1 1745 (ester C᎐O)
᎐
and 1675 (enone C᎐O); δH (300 MHz; CDCl3) 1.21 (3 H, t, J 7,
᎐
MeCH2), 1.987, 1.990, 2.02 and 2.08 (each 3 H, s, 4 × MeCO2),
2.34 (3 H, s, 1-H3), 3.56 and 3.87 (each 1 H, dq, J 9.5 and 7,
OCH2Me), 3.67 (1 H, dt, J 10 and 3.5, 5Ј-H), 4.14–4.16 (2 H, m,
6Ј-H2), 4.69 (1 H, d, J 8, 1Ј-H), 4.98–5.08 (2 H, m, 2Ј- and 4Ј-H),
5.19 (1 H, t, J 9.5, 3Ј-H), 5.51 (1 H, s, 1Љ-H) and 6.15 and 6.21
(each 1 H, s, 4-H2); δC (75 MHz; CDCl3) 15.02 (CH3CH2),
20.67, 20.69 and 20.79 (4 × CH3CO), 26.53 (1-CH3), 62.22
(6Ј-CH2), 64.34 (OCH2Me), 68.56, 71.34, 72.05 and 73.07 (2Ј-,
3Ј-, 4Ј- and 5Ј-CH), 97.51 and 98.53 (1Ј- and 1Љ-CH), 126.2
(4-CH2), 145.7 (3-C), 169.2, 169.5, 170.3 and 170.6 (4 × MeCO)
and 198.0 (2-CO); m/z (FAB) 601 [M(C7H11O2)ϩ, 2%], 497
[M(Na)ϩ, 2], 331 (C14H19O9ϩ, 34), 169 (66), 127 (C7H11O2ϩ, 89),
109 (50), 99 (C5H7O2ϩ, 79) and 43 (C2H3Oϩ, 100).
The second-eluted fraction (0.046 g, 10%), isolated as a col-
ourless syrup, was identified as (E)-3-ethoxymethyl-4-(2Ј,3Ј,
4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)but-3-en-2-one 23b.
After crystallisation from ethyl acetate–hexanes, the sample
(0.032 g, 7%) showed mp 102–104 ЊC; [α]D Ϫ12 (c 0.25, CH2Cl2)
(Found: C, 53.2; H, 6.4%); λmax (EtOH)/nm 239 (ε 17 100); νmax
of 25c and 24c); m/z (FAB) 628 [M(C8H12O2)ϩ, 8%], 527
ϩ
[M(K)ϩ, 3], 511 [M(Na)ϩ, 8], 489 (MHϩ, 1), 331 (C14H19O9
23), 169 (37), 141 (C8H13O2ϩ, 46), 109 (25) and 99 (C5H7O2
100).
,
,
ϩ
The second-eluted material (0.054 g, 11%), isolated as a
colourlesssyrup,wasidentifiedas(E)-3-propoxymethyl-4-(2Ј,3Ј,
4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)but-3-en-2-one 23c.
After crystallisation from ethyl acetate–hexanes, the sample
(0.038 g, 8%) showed mp 81–82 ЊC; [α]D ϩ4 (c 0.25, CH2Cl2)
(Found: C, 53.8; H, 6.5%); λmax (EtOH)/nm 239 (ε 17 200); νmax
(KBr)/cmϪ1 1760 and 1735 (ester C᎐O), 1690 (vinylogous ester
᎐
C᎐O) and 1610 (C᎐C); δ (300 MHz; CDCl ) 0.89 (3 H, t, J 7.5,
᎐
᎐
H
3
1762
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765

View Article Online
MeCH2), 1.50–1.60 (2 H, m, MeCH2), 2.03, 2.04 and 2.09 (3, 6
and 3 H, each s, 4 × MeCO2), 2.29 (3 H, s, 1-H3), 3.34 (2 H, t,
J 6.5, OCH2Et), 3.82 (1 H, ddd, J 2.5, 5 and 10, 5Ј-H), 4.08–4.23
(3 H, m, 6Ј-H and 3-CH2O), 4.29 (1 H, dd, J 5 and 12.5, 6Ј-H),
4.93 (1 H, d, J 7.5, 1Ј-H), 5.11–5.29 (3 H, m, 2Ј-, 3Ј- and 4Ј-H)
and 7.47 (1 H, s, 4-H); δC (75 MHz; CDCl3) 10.74 (CH3CH2),
20.64, 20.68 and 20.81 (4 × CH3CO), 22.98 (CH3CH2), 26.91
(1-CH3), 61.59 and 61.63 (6Ј-CH2 and 3-CH2), 67.89, 70.71,
72.20 and 72.83 (2Ј-, 3Ј-, 4Ј- and 5Ј-CH), 72.31 (OCH2Et), 101.0
(1Ј-CH), 120.5 (3-C), 155.8 (4-CH), 169.1, 169.4, 170.2 and
170.7 (4 × MeCO) and 197.6 (2-CO); m/z (FAB) 511 [M(Na)ϩ,
7%], 489 (MHϩ, 7), 331 (C14H19O9ϩ, 62), 169 (100), 109 (68) and
43 (88).
(2-CO); m/z (FAB) 511 [M(Na)ϩ, 6%], 489 (MHϩ, 17), 331
(C14H19O9ϩ, 93), 169 (100) and 109 (71).
(ii) The product from the reaction of the allylic bromide 14a
(0.382 g, 0.75 mmol) was subjected to column chromatography
[EtOAc–light petroleum (2:1) as eluent] to give three fractions.
The first-eluted fraction (0.070 g, 19%) was identified as a
58:42 mixture of the isopropoxy derivatives 24d and 25d.
The second-eluted fraction (0.025 g, ≈7%) was mainly a
70:30 mixture of the isopropoxy derivatives 24d and 25d. Crys-
tallisation of the mixture from diethyl ether–light petroleum
gave compound 24d (0.011 g, 3%) {mp 114–115 ЊC; [α]D Ϫ78
(c 0.2, CHCl3)}.
The third-elution fraction (0.020 g, 5%) was mainly com-
pound 23d.
(ii) The product obtained from the reaction of the allylic
bromide 14a (0.153 g, 0.3 mmol) was subjected to column
chromatography [EtOAc–light petroleum (2:1) as eluent]. One
main fraction (0.083 g, 56%) was obtained; it comprised largely
a 55:45 mixture of the propoxy derivatives 24c and 25c.
Reaction involving the allylic bromide 14a and tert-butyl alco-
hol. (i) The reaction involving the allylic bromide 14a (0.102 g,
0.2 mmol) [in the presence of CH2Cl2 (2 cm3)] gave rise to a
product that comprised mainly a 29:61:10 mixture of the tert-
butoxy derivatives 23e, 24e and 25e [the proportions were esti-
mated from the integrals of the signals at δ 7.40 (attributed to
the 4-H of 23e), 5.84 (assigned to the 1Љ-H of 24e) and 5.79
(ascribed to the 1Љ-H of 25e)]. Subjection of the mixture to
HPLC [EtOAc–hexanes (2:1) as eluent] led to the isolation of
two fractions.
The first-eluted fraction (0.050 g, 50%), isolated as a colour-
less syrup, was identified as a 84:16 mixture of the tert-butoxy
derivatives 24e and 25e. Crystallisation of the mixture from
diethyl ether–hexanes gave (1ЉR)-3-[1Љ-(tert-butoxy)-1Љ-(2Ј,3Ј,
4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)methyl]but-3-en-2-
one 24e (0.016 g, 16%); mp 137–138 ЊC; [α]D Ϫ79 (c 0.3, CHCl3)
(Found: C, 54.7; H, 6.7. C23H34O12 requires C, 55.0; H, 6.8%);
λmax (EtOH)/nm 207 (ε 7100); νmax (Nujol)/cmϪ1 1755 (ester
Reaction involving the allylic bromide 14a and isopropyl alco-
hol. (i) The reaction involving the allylic bromide 14a (0.509 g,
1.0 mmol) gave rise to a product that comprised mainly a
15:67:18 mixture of the isopropoxy derivatives 23d, 24d and
25d [the proportions were estimated from the integrals of the
signals at δ 7.44 (attributed to the 4-H of 23d), 5.61 (assigned to
the 1Љ-H of 24d) and 5.72 (ascribed to the 1Љ-H of 25d)]. Subjec-
tion of the mixture to HPLC [EtOAc–hexanes (2:1) as eluent]
led to the isolation of two fractions.
The first-eluted fraction (0.316 g, 65%), isolated as a colour-
less syrup, was identified as a 79:21 mixture of compounds 24d
and 25d; δH (300 MHz; CDCl3) (inter alia for 25d) 2.34 (3 H, s,
1-H3), 4.80 (1 H, d, J 8, 1Ј-H), 5.72 (1 H, s, 1Љ-H) and 6.22 and
6.25 (each 1 H, s, 4-H2). Crystallisation of the mixture from
diethyl ether–hexanes gave (1ЉR)-3-[1Љ-isopropoxy-1Љ-(2Ј,3Ј,4Ј,
6Ј-tetra-O-acetyl-β--glucopyranosyloxy)methyl]but-3-en-2-one
24d (0.104 g, 21%); mp 113–114 ЊC; [α]D Ϫ76 (c 0.25, CH2Cl2)
(Found: C, 53.9; H, 6.6. C22H32O12 requires C, 54.1; H, 6.6%);
C᎐O) and 1670 (enone C᎐O); δH (300 MHz; CDCl3) 1.25 (9 H,
᎐
᎐
s, Me3C), 1.99, 2.02 and 2.08 (3, 6 and 3 H, each s, 4 × MeCO2),
2.33 (3 H, s, 1-H3), 3.59 (1 H, dt, J 10 and 4, 5Ј-H), 4.13 (2 H, d,
separation 4, 6Ј-H2), 4.69 (1 H, d, J 8, 1Ј-H), 4.96–5.06 (2 H, m,
2Ј- and 4Ј-H), 5.17 (1 H, t, J 9.5, 3Ј-H), 5.84 (1 H, s, 1Љ-H) and
6.11 and 6.16 (each 1 H, s, CH2C); m/z (FAB) 525 [M(Na)ϩ,
10%], 503 (MHϩ, 4), 331 (C14H19O9ϩ, 100) and 169 (45).
λmax (EtOH)/nm 212 (ε 6900); νmax (KBr)/cmϪ1 1740 (ester C᎐O)
᎐
and 1670 (enone C᎐O); δ (300 MHz; CDCl3) 1.14 and 1.22
᎐
H
(each 3 H, d, J 6, Me2CH), 1.988, 1.992, 2.02 and 2.08 (each
3 H, s, 4 × MeCO2), 2.33 (3 H, s, 1-H3), 3.66 (1 H, dt, J 10 and 4,
5Ј-H), 4.04 (1 H, sept, J 6, OCHMe2), 4.15 (2 H, d, separation 4,
6Ј-H2), 4.68 (1 H, d, J 8, 1Ј-H), 4.98–5.07 (2 H, m, 2Ј- and 4Ј-H),
5.18 (1 H t, J 9.5, 3Ј-H), 5.61 (1 H, s, 1Љ-H) and 6.13 and 6.20
(each 1 H, s, 4-H2); δC (75 MHz; CDCl3) 20.71, 20.73 and
20.83 (4 × CH3CO), 21.37 and 23.23 [(CH3)2CH], 26.66
(1-CH3), 62.30 (6Ј-CH2), 68.63, 70.22, 71.39, 72.05 and 73.18
(2Ј-, 3Ј-, 4Ј- and 5Ј-CH and OCHMe2), 96.24 and 97.17 (1Ј- and
1Љ-CH), 126.1 (4-CH2), 146.3 (3-C), 169.2, 169.6, 170.4 and 170.7
(4 × MeCO) and 198.2 (2-CO); m/z (FAB) 489 (MHϩ, 1%), 331
(C14H19O9ϩ, 45), 169 (100) and 141 (C8H13O2ϩ, 60).
The second-eluted fraction (0.016 g, 16%), isolated as a
colourless syrup, was identified as (E)-3-(tert-butoxymethyl)-
4-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)but-3-en-2-
one 23e. After crystallisation from ethyl acetate–hexanes, the
sample (0.012 g, 12%) showed mp 92–93 ЊC; [α]D ϩ14 (c 0.25,
CH2Cl2) (Found: C, 54.8; H, 6.8%); λmax (EtOH)/nm 240 (ε
15 300); νmax (Nujol)/cmϪ1 1756 (ester C᎐O), 1687 (vinylogous
᎐
ester C᎐O) and 1605 (C᎐C); δH (300 MHz; CDCl3) 1.19 (9 H, s,
᎐
᎐
Me3C), 2.00, 2.01, 2.02 and 2.06 (each 3 H, s, 4 × MeCO2), 2.26
(3 H, s, 1-H3), 3.81 (1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.05
and 4.15 (each 1 H, d, J 9.5, CH2OCMe3), 4.11 and 4.26 [each
1 H, dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 4.92
(1 H, d, J 7.5, 1Ј-H), 5.09–5.26 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and
7.40 (1 H, s, 4-H); m/z (FAB) 525 [M(Na)ϩ, 9%], 503 (MHϩ, 8),
331 (C14H19O9ϩ, 60) and 169 (100).
(ii) The product obtained from the reaction of the allylic
bromide 14a (0.255 g, 0.5 mmol) [in the presence of CH2Cl2
(5 cm3)] was subjected to column chromatography [EtOAc–
light petroleum (2:1) as eluent] to give two fractions.
The first-eluted fraction (0.099 g, 39%) was a 73:27 mixture
of the tert-butoxy derivatives 24e and 25e. Crystallisation of
the mixture from diethyl ether–hexanes gave compound 24e
(0.065 g, 26%).
The second-eluted fraction (0.064 g, 13%), isolated as a col-
ourlesssyrup,wasidentifiedas(E)-3-isopropoxymethyl-4-(2Ј,3Ј,
4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyloxy)but-3-en-2-one 23d.
After crystallisation from ethyl acetate–hexanes, the sample
(0.044 g, 9%) showed mp 99–100 ЊC; [α]D ϩ8 (c 0.25, CH2Cl2)
(Found: C, 54.1; H, 6.6%); λmax (EtOH)/nm 239 (ε 15 600); νmax
(KBr)/cmϪ1 1760 and 1735 (ester C᎐O), 1690 (vinylogous ester
᎐
C᎐O) and 1610 (C᎐C); δ (300 MHz; CDCl3) 1.14 and 1.15
᎐
᎐
H
(each 3 H, d, J 6, Me2CH), 2.02, 2.038, 2.043 and 2.09 (each
3 H, s, 4 × MeCO2), 2.29 (3 H, s, 1-H3), 3.58 (1 H, sept, J 6,
OCHMe2), 3.82 (1 H, ddd, J 2.5, 4.5 and 9.5, 5Ј-H), 4.11–4.16
and 4.29 [each 1 H, m and dd (J 4.5 and 12.5), 6Ј-H2], 4.14 and
4.22 (each 1 H, d, J 10.5, 3-CH2O), 4.93 (1 H, d, J 7.5, 1Ј-H),
5.11–5.29 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.44 (1 H, s, 4-H);
δC (75 MHz; CDCl3) 20.61 and 20.75 (4 × CH3CO), 22.08
and 22.16 [(CH3)2CH], 26.86 (1-CH3), 59.05 and 61.56 (3-CH2
and 6Ј-CH2), 67.80, 70.66, 71.16, 72.29 and 72.72 (2Ј-, 3Ј-,
4Ј- and 5Ј-CH and OCHMe2), 100.8 (1Ј-CH), 120.8 (3-C), 155.6
(4-CH), 169.0, 169.4, 170.2 and 170.6 (4 × MeCO) and 197.5
The second-eluted fraction (0.049 g, 20%) [0.025 g, 10%
(after crystallisation from EtOAc–light petroleum)] was com-
pound 23e.
Reaction involving the allylic bromide 14b and methanol. The
reaction involving the allylic bromide 14b (0.314 g, 0.6 mmol)
gave rise to a product that comprised mainly a 7:63:30 mixture
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
1763

View Article Online
of the methoxy derivatives 28a, 29a and 30a [the proportions
were estimated from the integrals of the signals at δ 7.50
(attributed to the 1-H of 28a), 5.44 (ascribed to the 1Љ-H of 29a)
and 5.72 (assigned to 1Љ-H of 30a)]. There was also evidence for
the presence of the dimethoxy derivative 26b [δ 7.40 (1-H), 3.93
(1-MeO) and 3.35 (MeOCH2)] (the ratio of 28a and 26b was
≈1:2) and the tetraacetate 27. Subjection of the mixture to col-
umn chromatography [EtOAc–light petroleum (2:1) as eluent]
led to the isolation of one major fraction (0.167 g, 59%) identi-
fied as a 69:31 mixture of (1ЉR)-2-[1Љ-methoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-
tetra-O-acetyl-β--glucopyranosyloxy)methyl]pent-1-en-3-one
29a and its (1ЉS)-isomer 30a. After crystallisation from diethyl
ether–light petroleum, the sample (0.117 g, 41%) (still as a
69:31 mixture of 29a and 30a) showed mp 57–58 ЊC; [α]D Ϫ3
(c 0.4, CHCl3) (Found: C, 53.3; H, 6.2. C21H30O12 requires C,
53.2; H, 6.4%); λmax (EtOH)/nm 212 (ε 7100); νmax (KBr)/cmϪ1
its (1ЉS)-isomer 30c. After two crystallisations from diethyl
ether–light petroleum, the sample (0.038 g, 15%) (now as an
86:14 mixture of 29c and 30c) showed mp 123–125 ЊC; [α]D
Ϫ70 (c 0.35, CHCl3) (Found: C, 55.8; H, 6.9. C24H36O12 requires
C, 55.8; H, 7.0%); λmax (EtOH)/nm 209 (ε 5900); νmax (Nujol)/
cmϪ1 1748 (ester C᎐O) and 1678 (enone C᎐O); δ (300 MHz;
᎐
᎐
H
CDCl3) 1.08 (3 H, t, J 7.5, 5-H3), 1.24 and 1.26 (1.3 and 7.7 H,
each s, Me3C), 1.99, 2.00, 2.01, 2.02, 2.03, 2.06 and 2.09 (2.58,
0.42, 0.42, 3.00, 2.58, 0.42 and 2.58 H, each s, 4 × MeCO2),
2.57–2.85 (2 H, m, 4-H2), 3.62 (1 H, ddd, J 3, 4.5 and 10, 5Ј-H),
4.09–4.19 (2 H, m, 6Ј-H2), 4.69 and 4.76 (0.86 and 0.14 H, each
d, J 8, 1Ј-H), 4.96–5.08 (2 H, m, 2Ј- and 4Ј-H), 5.17 and 5.19
(0.86 and 0.14 H, each t, J 9.5, 3Ј-H), 5.80 and 5.86 (0.14 and
0.86 H, each s, 1Љ-H) and 6.10, 6.125, 6.133 and 6.15 (0.86, 0.86,
0.14 and 0.14 H, each s, 1-H2); m/z (FAB) 539 [M(Na)ϩ, 35%],
517 (MHϩ, 5), 331 (C14H19O9ϩ, 100) and 169 (15).
1750 (ester C᎐O) and 1680 (enone C᎐O); δ (300 MHz; CDCl )
᎐
᎐
H
3
1.09 and 1.10 (2.07 and 0.93 H, each t, J 7, 5-H3), 1.99, 2.01,
2.02, 2.04 and 2.07 (4.14, 0.93, 4.14, 0.93 and 1.86 H, each s,
4 × MeCO2), 2.61–2.80 (2 H, m, 4-H2), 3.25 and 3.46 (0.93 and
2.07 H, each s, MeO), 3.67–3.71 (1 H, m, 5Ј-H), 4.06–4.26 (2 H,
m, 6Ј-H2), 4.69 and 4.84 (0.69 and 0.31 H, each d, J 8, 1Ј-H),
5.00–5.12 (2 H, m, 2Ј- and 4Ј-H), 5.19 and 5.24 (0.69 and 0.31
H, each t, J 9.5, 3Ј-H), 5.44 and 5.72 (0.69 and 0.31 H, each s,
1Љ-H), and 6.14, 6.18 and 6.26 (1.38, 0.31 and 0.31 H, each s,
1-H2); m/z (FAB) 497 [M(Na)ϩ, 1%], 331 (C14H19O9ϩ, 65) and
169 (100).
Reaction involving the allylic bromide 14c and methanol. (i)
The reaction involving the allylic bromide 14c (0.210 g, 0.4
mmol) gave rise to a product that comprised mainly a 12:67:21
mixture of the methoxy derivatives 31a, 32a and 33a [the ratio
was estimated from the integrals of the signals at δ 7.60 (attrib-
uted to the 3-H of 31a), 5.40 (assigned to the 1Љ-H of 32a) and
5.70 (ascribed to the 1Љ-H of 33a)]. Subjection of the mixture to
HPLC [EtOAc–hexanes (2:1) as eluent] led to the isolation of
two fractions.
The first-eluted fraction (0.122 g, 64%) was identified as a
74:26 mixture of methyl (1ЉR)-2-[1Љ-methoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-
tetra-O-acetyl-β--glucopyranosyloxy)methyl]propenoate 32a
and its (1ЉS)-isomer 33a. After crystallisation from diethyl
ether–hexanes, the sample (0.064 g, 35%) (now as an 84:16
mixture of 32a and 33a) showed mp 87–89 ЊC; [α]D Ϫ60 (c 0.4,
CHCl3) (Found: C, 50.1; H, 5.8. C20H28O13 requires C, 50.4; H,
Reaction involving the allylic bromide 14b and isopropyl alco-
hol. The reaction involving the allylic bromide 14b (0.314 g, 0.6
mmol) gave rise to a product that comprised mainly a 20:52:28
mixture of the isopropoxy derivatives 28b, 29b and 30b [the
proportions were estimated from the integrals of the signals at
δ 7.44 (attributed to the 1-H of 28b), 5.62 (ascribed to the 1Љ-H
of 29b) and 5.72 (assigned to the 1Љ-H of 30b)]. Subjection of
the mixture to column chromatography [EtOAc–light petrol-
eum (2:1) as eluent] led to the isolation of one major fraction
(0.131 g, 43%), identified as a 66:34 mixture of (1ЉR)-2-[1Љ-
isopropoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyranosyl-
oxy)methyl]pent-1-en-3-one 29b and its (1ЉS)-isomer 30b. After
crystallisation from diethyl ether–light petroleum, the sample
(0.095 g, 31%) (now as a 69:31 mixture of 29b and 30b) showed
mp 84–85 ЊC; [α]D Ϫ61 (c 0.5, CHCl3) (Found: C, 54.7; H, 7.0.
C23H34O12 requires C, 55.0; H, 6.8%); λmax (EtOH)/nm 210
5.9%); νmax (KBr)/cmϪ1 1760 (ester C᎐O), 1725 (unsat. ester
᎐
C᎐O) and 1650 (C᎐C); δ (300 MHz; CDCl3) 2.00, 2.01, 2.02,
᎐
᎐
H
2.024, 2.03, 2.04, 2.08 and 2.09 (2.68, 2.68, 0.32, 2.68, 0.32, 0.32,
0.32 and 2.68 H, each s, 4 × MeCO2), 3.25 and 3.46 (0.32 and
2.68 H, each s, MeO), 3.64 (1 H, ddd, J 2.5, 5 and 10, 5Ј-H),
3.78 and 3.79 (2.68 and 0.32 H, each s, MeO2C), 4.10, 4.11, 4.20
and 4.26 [0.84, 0.16, 0.84 and 0.16 H, dd (J 2.5 and 12.5), dd
(J 2.5 and 12.5), dd (J 5 and 12.5) and dd (J 5 and 12.5), 6Ј-H2],
4.71 and 4.85 (0.84 and 0.16 H, each d, J 8, 1Ј-H), 5.03–5.11
(2 H, m, 2Ј- and 4Ј-H), 5.20 and 5.23 (0.84 and 0.16 H, each t,
J 9.5, 3Ј-H), 5.40 and 5.70 (0.84 and 0.16 H, each s, 1Љ-H)
and 6.08, 6.10, 6.32 and 6.46 [0.84, 0.16, 0.84 and 0.16 H, t
(J 1), t (J 1), d (J 1) and d (J 1), 3-H2]; m/z (FAB) 807
[M(C14H19O9)ϩ, 2%], 499 [M(Na)ϩ, 12], 477 (MHϩ, 2), 331
(C14H19O9ϩ, 50), 169 (70) and 129 (C6H9O3ϩ, 100).
The second-eluted fraction (0.016 g, 8%) was methyl (E)-2-
methoxymethyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β--glucopyrano-
syloxy)propenoate 31a; δH (300 MHz; CDCl3) 2.02, 2.04 and
2.09 (3, 6 and 3 H, each s, 4 × MeCO2), 3.28 (3 H, s, MeO), 3.75
(3 H, s, MeO2C), 3.82 (1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.12
(2 H, s, 2-CH2O), 4.14 and 4.29 [each 1 H, dd (J 2.5 and 12.5)
and dd (J 4.5 and 12.5), 6Ј-H2], 4.92 (1 H, d, J 7.5, 1Ј-H), 5.11–
5.28 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.60 (1 H, s, 3-H).
(ii) The product from the reaction of the allylic bromide 14c
(0.368 g, 0.7 mmol) was subjected to column chromato-
graphy [EtOAc–light petroleum (2:1) as eluent] to give two
fractions.
(ε 8500); νmax (Nujol)/cmϪ1 1744 (ester C᎐O) and 1680 (enone
᎐
C᎐O); δ (300 MHz; CDCl3) 1.06–1.25 (9 H, m, 5-H3 and
᎐
H
Me2CH), 1.976, 1.988, 1.992, 2.005, 2.02, 2.03, 2.06 and 2.08
(0.93, 2.07, 2.07, 0.93, 2.07, 0.93, 0.93 and 2.07 H, each s,
4 × MeCO2), 2.58–2.84 (2 H, m, 4-H2), 3.66 (1 H, ddd, J 3, 4.5
and 10, 5Ј-H), 3.88 (0.31 H, sept, J 6, 0.31 × CHMe2), 3.98–4.22
(2.69 H, m, 0.69 × CHMe2 and 6Ј-H2), 4.68 and 4.81 (0.69 and
0.31 H, each d, J 8, 1Ј-H), 4.98–5.09 (2 H, m, 2Ј- and 4Ј-H), 5.18
and 5.22 (0.69 and 0.31 H, each t, J 9.5, 3Ј-H), 5.62 and 5.72
(0.69 and 0.31 H, each s, 1Љ-H) and 6.12, 6.16, 6.20 and 6.21
(0.69, 0.69, 0.31 and 0.31 H, each s, CH2C); m/z (FAB) 525
[M(Na)ϩ, 12%], 503 (MHϩ, 3), 331 (C14H19O9ϩ, 65), 169 (40)
and 113 (100).
Reaction involving the allylic bromide 14b and tert-butyl alco-
hol. The reaction involving the allylic bromide 14b (0.262 g, 0.5
mmol) [in the presence of CH2Cl2 (5 cm3)] gave rise to a product
that comprised mainly a 29:49:22 mixture of the tert-butoxy
derivatives 28c, 29c and 30c [the proportions were estimated
from the integrals of the signals at δ 7.41 (attributed to the 1-H
of 28c), 5.86 (ascribed to the 1Љ-H of 29c) and 5.80 (assigned to
the 1Љ-H of 30c)]. Subjection of the mixture to column chromato-
graphy [EtOAc–light petroleum (2:1) as eluent] led to the iso-
lation of one main fraction (0.132 g, 52%), identified as a 69:31
mixture of (1ЉR)-2-[1Љ-(tert-butoxy)-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-
acetyl-β--glucopyranosyloxy)methyl]pent-1-en-3-one 29c and
The first-eluted fraction (0.182 g, 52%) was a 75:25 mixture
of the methoxy derivatives 32a and 33a.
The second-eluted fraction (0.029 g, ≈9%) was mainly com-
pound 31a.
Reaction involving the allylic bromide 14c and isopropyl alco-
hol. (i) The reaction involving the allylic bromide 14c (0.210 g,
0.4 mmol) gave rise to a product that comprised mainly a
26:61:13 mixture of the isopropoxy derivatives 31b, 32b and
1764
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765

View Article Online
33b [the proportions were estimated from the integrals of the
signals at δ 7.54 (attributed to the 3-H of 31b), 5.58 (ascribed to
the 1Љ-H of 32b) and 5.70 (assigned to the 1Љ-H of 33b)]. Subjec-
tion of the mixture to HPLC [EtOAc–hexanes (1:1) as eluent]
gave two fractions.
[each 1 H, dd (J 2.5 and 12) and dd (J 5 and 12), 6Ј-H2], 4.73
(1 H, d, J 8, 1Ј-H), 5.00–5.08 (2 H, m, 2Ј- and 4Ј-H), 5.17 (1 H,
t, J 9.5, 3Ј-H), 5.79 (1 H, s, 1Љ-H) and 6.09 and 6.27 (each 1 H, s,
3-H2); m/z (FAB) 541 [M(Na)ϩ, 10%], 519 (MHϩ, 2) and 331
(C14H19O9ϩ, 100).
The first-eluted fraction (0.110 g, 55%) was identified as an
82:18 mixture of the isopropoxy derivatives 32b and 33b. Crys-
tallisation of the mixture from diethyl ether–hexanes gave
methyl (1ЉR)-2-[1Љ-isopropoxy-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β-
-glucopyranosyloxy)methyl]propenoate 32b (0.034 g, 17%); mp
108–109 ЊC; [α]D Ϫ58 (c 1.54, CHCl3) (Found: C, 52.2; H, 6.2.
C22H32O13 requires C, 52.4; H, 6.4%); λmax (EtOH)/nm 206 (ε
6200); δH (300 MHz; CDCl3) 1.16 and 1.23 [each 3 H, d (J 6)
and d (J 6.5), Me2CH], 2.00, 2.01, 2.02 and 2.09 (each 3 H, s,
4 × MeCO2), 3.62 (1 H, ddd, J 2.5, 5 and 10, 5Ј-H), 3.77 (3 H, s,
MeO2C), 4.00–4.10 (2 H, m, OCHMe2 and 6Ј-H), 4.18 (1 H, dd,
J 5 and 12, 6Ј-H), 4.71 (1 H, d, J 8, 1Ј-H), 5.02–5.09 (2 H, m, 2Ј-
and 4Ј-H), 5.19 (1 H, t, J 9.5, 3Ј-H), 5.58 (1 H, s, 1Љ-H) and 6.11
and 6.29 (each 1 H, s, 3-H2); m/z (FAB) 661 (5%), 505 (MHϩ,
2), 331 (C14H19O9ϩ, 20), 169 (35) and 115 (100).
The second-eluted fraction (0.115 g, 32%) was identified as
methyl (E)-2-(tert-butoxymethyl)-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-
β--glucopyranosyloxy)propenoate 31c. After crystallisation
from ethyl acetate–light petroleum, the sample (0.047 g, 13%)
showed mp 106–107 ЊC; [α]D Ϫ19 (c 0.22, CHCl3) (Found: C,
53.5; H, 6.6%); λmax (EtOH)/nm 227 (ε 16 300); νmax (Nujol)/
cmϪ1 1758 and 1736 (ester C᎐O), 1709 (vinylogous carbonate
᎐
C᎐O) and 1643 (C᎐C); δ (300 MHz; CDCl3) 1.21 (9 H, s,
᎐
᎐
H
Me3C), 2.02, 2.03, 2.04 and 2.09 (each 3 H, s, 4 × MeCO2), 3.73
(3 H, s, MeO2C), 3.80 (1 H, ddd, J 2.5, 4.5 and 10, 5Ј-H), 4.03
and 4.10 (each 1 H, d, J 9.5, 2-CH2O), 4.13 and 4.28 [each 1 H,
dd (J 2.5 and 12.5) and dd (J 4.5 and 12.5), 6Ј-H2], 4.90 (1 H, d,
J 7, 1Ј-H), 5.11–5.27 (3 H, m, 2Ј-, 3Ј- and 4Ј-H) and 7.51 (1 H,
s, 3-H); m/z (FAB) 541 [M(Na)ϩ, 2%], 519 (MHϩ, 1) 331
(C14H19O9ϩ, 100) and 169 (65).
The second-eluted fraction (0.044 g, 22%) was compound
31b.
Stability studies involving the methoxy compounds 23a and 24a
with methanol in the presence of silver(I) oxide
(ii) The product from the reaction of the allylic bromide 14c
(0.525 g, 1.0 mmol) was subjected to column chromatography
[EtOAc–light petroleum (1:1) as eluent] to give two fractions.
The first-eluted fraction (0.341 g, 67%) was an 83:17 mixture
of the isopropoxy derivatives 32b and 33b. Crystallisation of
the mixture from diethyl ether–light petroleum gave compound
32b (0.213 g, 42%).
The second-eluted fraction (0.020 g, 5%) [0.013 g, 3% (after
crystallisation from EtOAc–light petroleum)] was identified as
methyl (E)-2-isopropoxymethyl-3-(2Ј,3Ј,4Ј,6Ј-tetra-O-acetyl-β-
-glucopyranosyloxy)propenoate 31b; mp 88–89.5 ЊC; [α]D Ϫ19
(c 0.22, CHCl3) (Found: C, 52.4; H, 6.5. C22H32O13 requires C,
52.4; H, 6.4%); λmax (EtOH)/nm 227 (ε 16 300); δH (300 MHz;
CDCl3) 1.14 and 1.16 (each 3 H, d, J 6, Me2CH), 2.03, 2.04,
2.05 and 2.10 (each 3 H, s, 4 × MeCO2), 3.60 (1 H, sept, J 6,
OCHMe2), 3.75 (3 H, s MeO2C), 3.82 (1 H, ddd, J 2.5, 4.5 and
9.5, 5Ј-H), 4.12–4.18 and 4.30 [each 1 H, m, and dd (J 4.5 and
12.5), 6Ј-H2], 4.15 (2 H, AB q, J 10.5, separation of inner lines
12.5, 2-CH2O), 4.92 (1 H, d, J 7, 1Ј-H), 5.12–5.21 (2 H, m,
The methoxy compounds 23a and 24a (0.009 g, 0.02 mmol)
were each added to suspensions of silver() oxide (0.005 g, 0.02
mmol) in methanol (2 cm3) that had been stirred in the dark for
1.5 h. Work-up after 24 h yielded residues that contained 90%
unchanged compounds 23a and 24a and 10% of the dimethoxy
compound 26a.
Acknowledgements
We thank the Instituto de Biotecnologia e Quimica Fina
(IBQF-Minho) for financial support, the EPSRC for research
grant GR/L52246 (to assist in the purchase of the 400 MHz 1H
NMR spectrometer) and the Royal Society for research grant
10606 (to assist in the purchase of the HPLC equipment). We
are also grateful to Dr R. Perry for the elemental analyses, Mr
K. Walkling for recording some of the UV and IR spectra, and
Mr R. Perkins for the mass spectral determinations.
2Ј- and 4Ј-H), 5.26 (1 H, t, J 9, 3Ј-H) and 7.54 (1 H, s, 3-H);
ϩ
m/z (FAB) 527 [M(Na)ϩ, 30%], 505 (MHϩ, 5), 331 (C14H19O9
,
84), 169 (100) and 109 (77).
References
Reaction involving the allylic bromide 14c and tert-butyl alco-
hol. The reaction involving the allylic bromide 14c (0.368 g, 0.7
mmol) [in the presence of CH2Cl2 (5 cm3)] gave rise to a product
that comprised mainly a 35:53:12 mixture of the tert-butoxy
derivatives 31c, 32c and 33c [the proportions were estimated
from the integrals of the signals at δ 7.51 (attributed to the 3-H
of 31c), 5.79 (ascribed to the 1Љ-H of 32c) and 5.77 (assigned to
the 1Љ-H of 33c)]. Subjection of the mixture of column chromato-
graphy [EtOAc–light petroleum (1:1) as eluent] led to the isol-
ation of two fractions.
1 A. P. Esteves, A. M. Freitas, C. M. Raynor and R. J. Stoodley,
Tetrahedron Lett., 1998, 39, 8353.
2 R. J. Stoodley, Carbohydr. Polym., 1998, 37, 249.
3 D. S. Larsen, A. Schofield, R. J. Stoodley and P. D. Tiffin, J. Chem.
Soc., Perkin Trans. 1, 1996, 2487.
4 M. S. Idris, D. S. Larsen, A. Schofield, R. J. Stoodley and P. D.
Tiffin, Tetrahedron Lett., 1995, 36, 3251.
5 G. S. Bhatia, R. F. Lowe, R. G. Pritchard and R. J. Stoodley, Chem.
Commun., 1997, 1981; G. S. Bhatia, R. F. Lowe and R. J. Stoodley,
Tetrahedron Lett., 1998, 39, 9245.
6 D. S. Larsen and R. J. Stoodley, J. Chem. Soc., Perkin Trans. 1, 1989,
1841.
The first-eluted fraction (0.171 g, 48%) was identified as an
82:18 mixture of the tert-butoxy derivatives 32c and 33c;
δH (300 MHz; CDCl3) (inter alia for 33c) 4.77 (1 H, d, J 8, 1Ј-H),
5.77 (1 H, s, 1Љ-H) and 6.14 and 6.35 (each 1 H, s, 3-H2).
Crystallisation of the mixture from diethyl ether–light petrol-
eum gave methyl (1ЉR)-2-[1Љ-(tert-butoxy)-1Љ-(2Ј,3Ј,4Ј,6Ј-tetra-
O-acetyl-β--glucopyranosyloxy)propenoate 32c (0.122 g, 34%);
mp 135–136 ЊC; [α]D Ϫ53 (c 0.4, CHCl3) (Found: 53.5; H, 6.3.
C23H34O13 requires C, 53.3; H, 6.6%); λmax (EtOH)/nm 205
(ε 7200); νmax (Nujol)/cmϪ1 1748 (ester C᎐O), 1714 (enone C᎐O)
7 R. C. Gupta, D. S. Larsen, R. J. Stoodley, A. M. Z. Slawin and
D. J. Williams, J. Chem. Soc., Perkin Trans. 1, 1989, 739.
8 J. S. Pizey, Synthetic Reagents, Ellis Horwood, Chichester, 1974,
vol. 2, p. 1; Encyclopaedia of Reagents for Organic Synthesis,
ed. L. A. Paquette, John Wiley, Chichester, 1995, vol. 1, p. 768.
9 L. J. Bellamy, Advances in Infrared Group Frequencies, Methuen,
London, 1968, p. 57.
10 G. C. Levy and G. L. Nelson, Carbon-13 Nuclear Magnetic
Resonance for Organic Chemists, Wiley Interscience, New York,
1972, p. 133.
11 I. Fleming, Frontier Orbitals and Organic Chemical Reactions,
Wiley Interscience, London, 1976, pp. 41–42.
12 T.-L. Ho, Chem. Rev., 1975, 75, 1.
13 R. N. Magid, Tetrahedron, 1980, 36, 1901.
᎐
᎐
and 1633 (C᎐C); δ (300 MHz; CDCl3) 1.26 (9 H, s, Me3C),
᎐
H
1.99, 2.01, 2.03 and 2.08 (each 3 H, s, 4 × MeCO2), 3.56 (1 H,
ddd, J 2.5, 5 and 10, 5Ј-H), 3.75 (3 H, s, MeO), 4.05 and 4.16
J. Chem. Soc., Perkin Trans. 1, 2000, 1753–1765
1765