Synthesis and evaluation of sulfonium analogues of isofucofagomine as glycosidase inhibitors

Article abstract of DOI:10.1039/b202021c

A series of L-fucopyranose analogues having a sulfur substituent at the anomeric position were synthesised. A sulfide, a methylsulfonium ion, a sulfoxide and a sulfone analogue were made. The synthesised compounds were tested for inhibition of two α-fucos

Full text of DOI:10.1039/b202021c

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Synthesis and evaluation of sulfonium analogues of
isofucofagomine as glycosidase inhibitors
Víctor Ulgar,a,b José G. Fernández-Bolañosb and Mikael Bols*a
1
a Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark.
E-mail: mb@chem.au.dk; Fax: ϩ45 86196199; Tel: ϩ45 89423963
b Department of Organic Chemistry, Faculty of Chemistry, University of Seville, PO Box 553,
41071 Seville, Spain. E-mail: bolanos@us.es; Fax: ϩ34 954624960; Tel: ϩ34 954557150
Received (in Cambridge, UK) 26th February 2002, Accepted 28th March 2002
First published as an Advance Article on the web 17th April 2002
A series of -fucopyranose analogues having a sulfur substituent at the anomeric position were synthesised.
A sulfide, a methylsulfonium ion, a sulfoxide and a sulfone analogue were made. The synthesised compounds
were tested for inhibition of two α-fucosidases. The methylsulfonium ion was found to be a moderately strong
competitive inhibitor, and 700 times more potent than the corresponding sulfide.
Introduction
Glycosidases and related enzymes are crucial in many biological
processes. Potent and selective inhibitors of these enzymes are
important, because they can be used to interfere with such
processes. Thus glycosidase inhibitors may be potential agents
against diabetes,1 cancer,2 AIDS,3 hepatitis,4 Gaucher’s disease4
Fig. 2
and influenza.5 The search for new potent glycosidase inhibitors
has therefore been intense. An interesting recent finding is the
instance, longer C–S bonds and the larger S atom. In the
present paper we have investigated this idea. The piperidines
5 and 6 are potent α-fucosidase inhibitors and are possibly
binding to the enzyme in a protonated form.12,13 We report
herein the synthesis of two sulfonium ion analogues of 5 as well
as the synthesis of other sulfur analogues of 5, and report that
these compounds are indeed α-fucosidase inhibitors.
observation that the natural product sulfonium ions salacinol
(1) and kotalanol (2), are potent α-glucosidase inhibitors.6,7
The related synthetic glycosidase inhibitors, 3 and 4, have also
been reported (Fig. 1).8,9 Sulfonium ion analogues of castano-
Results and discussion
In order to synthesise various types of charged sulfur com-
pounds, a cyclic sulfide analogue of 5 appeared to be a good
synthetic intermediate. 6-Membered cyclic sulfides have
previously been obtained from 1,5-dihalides or 1,5-disulfonates
using Na2S as a reagent even on carbohydrate type sub-
strates.14,15 Therefore, the dimesylate (bis(methanesulfonate)) 8
was chosen as a starting material (Scheme 1). Mesylation of the
Fig. 1
spermine have also been made.10 It is reasonable that the inhibi-
tors 1–4 may owe their biological activity to a resemblance with
the oxocarbenium ion like transition state A (Fig. 2). Since
strong glycosidase inhibitors have also been found among
compounds with the ability to mimic charge at anomeric
carbon atoms (i.e. isofagomine),11 the idea was conceived that
introducing the sulfonium ion moiety at the C-1 position of a
monosaccharide might create potent glycosidase inhibitors by
analogy with transition state B (Fig. 2). A charged sulfur atom
has some interesting differences compared to nitrogen; for
Scheme 1
known diol 716 with mesyl chloride at 5 ЊC in pyridine contain-
ing DMAP as catalyst afforded 8 in 98% yield. This compound
was pure enough to be used in the next step without further
purification. Reaction of 8 with anhydrous Na2S in refluxing
1242
J. Chem. Soc., Perkin Trans. 1, 2002, 1242–1246
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b202021c

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MeOH gave a 57% yield of the cyclic sulfide 9 after 12 h. The
relatively low yield of this reaction is explained by the form-
ation of a less polar aromatic by-product whose exact identity
has not been determined. Deprotection of 9 was carried out
with TFA in MeOH–H2O which led to 10 in 85% yield after
chromatography.
shift of the methylene of the S-benzyl group (48.14 ppm) is
close to that observed for trans-1-benzyl-4-tert-butylthianium
tetrafluoroborate24 (47.59 ppm). This fact and the similarity
observed between the chemical shifts of carbons C-3 and C-5
(68.51 and 33.94 ppm respectively) and those of 11S (69.60 and
35.46 ppm) led us to identify 12 as the equatorial R (or β)
stereoisomer (as depicted in Scheme 2).
Sulfide 10 now served as a source for several compounds
(Scheme 2). A way to prepare positively charged potential
The polar nature of the S–O bond in sulfoxides and sulfones
agrees with the existence of a high positive charge density on
the sulfur atom in these types of compounds. Therefore, they
also resemble transition state B (Fig. 2). In this sense, we
synthesised the epimeric mixture of sulfoxides 14 and the
sulfone 16 by oxidation of 9 with either an equimolecular or an
excess amount of m-chloroperbenzoic acid and subsequent
deacetonation (Scheme 3). Treatment of 9 with 1 equivalent of
Scheme 2
glycosidase inhibitors derived from thiosugars having sulfur in
the ring is the introduction of a positive charge on the sulfur
atom by alkylation, that is, the preparation of sulfonium salts.
It is noteworthy that the alkylating agent should be carefully
selected because it is known that nucleophilic counterions (e.g.
halides) slowly decompose the sulfonium cation via nucleophilic
substitution reactions.10,17 For this reason alkyl perchlorates18
and triflates†19–22 have been used as alkylating reagents. Due
to the inherent risk of explosion in the handling of organic
perchlorates we decided to use triflates in these reactions. In fact
methyl triflate is commercially available and benzyl triflate can
be easily prepared by esterification of benzyl alcohol with triflic
anhydride in the presence of a base.20–22
Scheme 3
MCPBA at Ϫ78 ЊC in EtOAc gave the sulfoxide 13 as mixture
of isomers in 81% yield. The solvent was selected due to its
ability to dissolve both the peroxy acid and the sulfide at
low temperatures.25 The product was a chromatographically
irresolvable 4 : 1 mixture of epimeric stereoisomers as deter-
mined by digital integration of the 1H NMR spectrum.
Alkylation of 10 using methyl triflate in nitromethane at 0 ЊC
gave 11 in 97% yield (Scheme 2), obtained as a chromato-
graphically irresolvable 4 : 1 mixture of stereoisomers as
1H NMR studies on thiane oxides have revealed three effects
which allow the sulfoxide configuration in these compounds
to be assigned.26,27 The first is the syn-axial effect that implies
a deshielding of the axial β-hydrogens in axial sulfoxides.
Secondly, geminal coupling constants in α-methylene groups
are smaller for equatorial sulfoxides, and finally equatorial
α-hydrogens are shielded (ca. 0.3 ppm) in axial sulfoxides. A
comparison between the chemical shifts of H-3 and H-5 and
1
determined by digital integration of the H NMR spectrum.
Analytical TLC of the crude product of reaction showed the
absence of compounds less polar than 10, confirming that
no O-alkylation side reactions had occurred. The 13C NMR
spectrum of the sulfonium salt was used for assigning the
configuration of the stereoisomers. As is known, the steric
interaction between an axial methyl group and the syn axial
protons in a cyclohexane ring results in the shielding of the
carbons attached to these protons (γ effect).23 In this sense the
observation that the C-3 (66.53 ppm) and C-5 (32.34 ppm)
carbons of the minor isomer are shielded with respect to the
major isomer (69.90 and 35.46 ppm respectively) led us to
assign the major isomer as being the S equatorial isomer. The
observed chemical shift of the S-methyl group in the major
isomer (28.01 ppm) compared with the minor isomer (20.99
ppm) also supports our assignment. This result indicates that,
as expected, the alkylation process takes place preferentially
from the less hindered face of the thiane ring.
In order to test how an increase in the lipophilicity of the
sulfonium salt would affect its inhibitory activity, we decided
to prepare the S-benzyl sulfonium salt by benzylation of 10. In
this case benzyl triflate was made in situ in CH2Cl2 from benzyl
alcohol, Tf2O and 2,6-di-tert-butylpyridine, and then reacted
with sulfide 10 in dichloromethane. This gave the S-benzyl
derivative 12 in 90% yield after chromatography. In this case the
1H NMR spectrum indicated that the compound was composed
almost exclusively of only one stereoisomer. The 13C chemical
2
the J2ax,2eq coupling constant of the major isomer (4.63 ppm,
2.82 ppm and 14.1 Hz, respectively) and those observed for
the minor isomer (4.31 ppm, 2.05 ppm and 12.0 Hz) clearly
indicates that the major isomer is the axial R sulfoxide. This
conclusion is also supported by the observation that the H-2eq
and H-6eq protons of this stereoisomer appear shielded (ca.
0.37 ppm) with respect to the minor sulfoxide. Interestingly, we
noticed that the geminal coupling constant values (2J2ax,2eq and
2J6ax,6eq) of the α-methylenes of the sulfonium salt 11 are
appreciably higher in the axial isomer (14.3 and 14.8 Hz) than
in the equatorial isomer (11.1 and 11.8 Hz), as is also observed
in the isomers of the sulfoxide 14. Deacetonation of 13 with
trifluoroacetic acid in MeOH–H2O at room temperature
afforded 14 in 88% yield. Despite reports describing the acid
lability of the sulfoxide grouping,28 in our hands the hydrolysis
of the isopropylidene group did not alter the axial : equatorial
ratio.
Oxidation of 9 using two equivalents of MCPBA at 25 ЊC
gave the sulfone 15 in 86% yield. TFA treatment gave the
unprotected sulfone 16 in 80% yield.
The vicinal coupling constants data for compounds 9–16
agrees with preference for the 1C4 conformation in solution. The
† The IUPAC name for triflate is trifluoromethanesulfonate.
J. Chem. Soc., Perkin Trans. 1, 2002, 1242–1246
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values for 3J5,6ax are in the range 11.6–14.8 Hz indicating a trans
Products were concentrated on a rotary evaporator below
40 ЊC. All enzymes and substrates for the enzyme assays were
purchased from Sigma.
diaxial relationship between these protons. The coupling
3
constant J3,2ax is more sensitive to conformational distortions
due to the presence of the 1,3-dioxolane ring in 9, 13 and 15,
but nevertheless, the values for the O-unprotected derivatives
fall in the range 11.2–12.4 Hz supporting the 1C4 conformation.
This conformation is also confirmed by the observance of long
range 4JH,H coupling constants between H-2eq, H-4 and H-6eq.
Of the three possible “w” paths the path involving the sulfur
atom of the thiane ring (that is, the coupling between H-6eq
2-Deoxy-3,4-O-isopropylidene-2-C-methyl-1,5-bis(O-methyl-
sulfonyl)-L-ribitol (8)
To a solution of 2-deoxy-3,5-O-isopropylidene-2-C-methyl--
ribitol 7 (1.0 g, 5.68 mmol) and DMAP (5 mg) in dry pyridine
(10 mL) was added mesyl chloride (1.3 g, 11.36 mmol) at 0 ЊC.
The obtained mixture was left overnight at 5 ЊC, then concen-
trated in vacuo and taken up in 1 : 1 H2O–CH2Cl2 (100 mL).
After separation of both phases the aqueous layer was
extracted with CH2Cl2 (3 × 30 mL). The combined organic
phases were washed with 1 M HCl (5 × 50 mL), saturated aq.
NaHCO3 (50 mL) and H2O (50 mL), dried (Na2SO4) and con-
centrated to dryness to give 8 (1.8 g, 98%) which was pure
enough to be used without further purification in the next step.
1H NMR (CDCl3, 200 MHz) δ 4.34–3.90 (m, 6H, H-1, H-1Ј,
H-3, H-4, H-5, H-5Ј), 3.02, 2.96 (2s, 3H each, MeSO3), 2.02 (m,
1H, H-2), 1.42, 1.28 (2s, 3H each, Me2C), 1.10 (d, 3H, J2,2Ј 7.0
Hz, H-2Ј); m/z (ES) 332.0598 (M ϩ Naϩ). Calc. for C10H20O8S2
ϩ Naϩ: m/z 332.0600.
4
and H-2eq) results in JH,H values in the interval 1.5–3.9 Hz.
The cis fused 1,3-dioxolane ring introduces a torsional tension
in the thiane ring forcing it to adopt a distorted chair conform-
ation. This results in a decrease in the dihedral angles between
H-3 and the vicinal protons H-2eq, H-2ax and H-4. While 3J3,2ax
3
3
experiences a decrease, J3,2eq and J3,4 increase due to the fact
that the corresponding dihedral angles are closer to 0Њ.
The new fucose analogues 10, 11, 12, 14 and 16 were tested
for inhibition of two α-fucosidases. All were either competitive
inhibitors or they did not inhibit. The sulfide 10 was an
extremely poor inhibitor of both enzymes. This is not surpris-
ing since neither in terms of charge or geometry does it mimic
the transition state. However as soon as the sulfur atom
becomes charged, as in the methyl sulfonium analogue 11, the
inhibition is increased 700 times. This very clearly demonstrates
the advantage of having a positive charge in this position. The
increased binding may be a result of a salt bridge between the
catalytic nucleophile in the enzyme and the charged sulfur.
Compound 11 is a 25–50 times weaker fucosidase inhibitor
than 5. This may be explained to some part by the poor fit of
the methyl group in the enzyme active site. N-Methylated
analogues of isofagomines are generally much weaker inhib-
itors than the secondary amines themselves presumably because
of unfavourable interactions of the methyl group in that area.29
The S-benzyl sulfonium salt 12 has an inhibitory activity much
like 11. This suggests that the size of the S-alkyl group is of
minor importance. Interestingly the sulfoxide 14 is a consider-
ably weaker inhibitor than 11 although still a 100 times stronger
inhibitor than 10. This suggests that 14 can benefit from some
electrostatic interaction between the enzyme nucleophile and
the charged sulfur atom. However, the negative oxygen atom
appears to be unfavourable in the electronegative surroundings
around the anomeric carbon. This situation is intensified in the
sulfone 16, which is a weaker inhibitor. This may however also
be due to limited space in the active site to accommodate the
sulfone.
(3R,4R,5R)-3,4-Isopropylidenedioxy-5-methylthiane (9)
To a solution of the dimesylate 8 (808 mg, 2.33 mmol) in
MeOH (75 mL) was added anhydrous Na2S (364 mg, 4.66
mmol). The mixture was stirred under reflux for 12 h. The
resulting solution was then concentrated to give a yellowish oil
which was dissolved in CH2Cl2 (20 mL) and extracted with H2O
(2 × 20 mL). The organic phase was dried (Na2SO4) and evap-
orated to dryness. The resulting oil was purified by column
chromatography on silica gel using pentane–Et2O (20 : 1) as
eluent (Rf 0.25). The yield was 251 mg (57%) of 9 as a white
solid. [a]2D2 ϩ24.8 (c 0.9, CHCl3); 1H NMR (CDCl3, 500 MHz) δ
4.11 (ddd, 1H, J3,4 4.8 Hz, J3,2ax 9.4 Hz, J3,2eq 6.4 Hz, H-3), 4.05
(br t, 1H, J4,5 3.5 Hz, H-4), 2.59 (dd, 1H, J2ax,2eq 13.4 Hz, H-
2ax), 2.55 (dddd, 1H, J2eq,6eq 1.8 Hz, J4,2eq 0.4 Hz, H-2eq), 2.49
(dd, 1H, J5,6ax 12.0 Hz, J6ax,6eq 13.0 Hz, H-6ax), 2.20 (dddd, 1H,
J5,6eq 4.0 Hz, J4,6eq 0.6 Hz, H-6eq), 2.14 (m, 1H, H-5), 1.47, 1.31
(2s, 3H each, Me2C), 1.10 (d, 3H, J5,5Ј 7.0 Hz, H-5Ј); 13C NMR
(CDCl3, 75 MHz) δ 107.86 (Me2C), 76.59 (C-4), 73.36 (C-3),
35.95 (C-5), 29.26 (C-6), 29.17 (C-2), 28.56, 26.29 (Me2C), 18.64
(C-5Ј); m/z (ES) 211.0771 (M ϩ Naϩ). Calc. for C9H16O2S ϩ
Naϩ: m/z 211.0769.
In conclusion the results show that monosaccharide deriv-
atives having positively charged sulfur atoms at anomeric
positions are indeed glycosidase inhibitors. They are however in
this case much weaker than the corresponding amines.
(3R,4R,5S)-3,4-Dihydroxy-5-methylthiane (10)
A solution of 9 (200 mg, 1.06 mmol) and TFA (0.5 mL) in 5 : 1
MeOH–H2O (6 mL) was left at room temperature for 1 h. The
solution was concentrated and the residue was purified by
column chromatography on silica gel using pentane–EtOAc
(1 : 1) as eluent (Rf 0.38). The yield was 134 mg (85%) of 10 as a
white solid. [a]2D2 ϩ16.9 (c 0.9, CHCl3); 1H NMR (CD3OD, 500
MHz) δ 3.67 (br t, 1H, J3,4 2.4 Hz, J4,2eq 1.5 Hz, H-4), 3.63 (ddd,
1H, J3,2ax 11.2 Hz, J3,2eq 4.2 Hz, H-3), 2.82 (dd, J2ax,2eq 12.6 Hz,
H-2ax), 2.55 (dd, 1H, J5.6ax 11.9 Hz, J6ax,6eq 13.2 Hz, H-6ax),
2.18 (ddt, 1H, J2eq,6eq 1.5 Hz, H-2eq), 1.93 (ddd, 1H, J5,6eq 3.6
Hz, H-6eq), 1.86 (m, 1H, H-5), 1.00 (d, 3H, J5,5Ј 6.9 Hz, H-5Ј);
13C NMR (CD3OD, 75 MHz) δ 74.16 (C-4), 73.56 (C-3), 40.75
(C-5), 27.88 (C-6), 27.72 (C-2), 19.26 (C-5Ј); m/z (CI) 148.0557
(Mϩ). Calc. for C6H12O2Sϩ: m/z 148.0558.
Experimental
General
Solvents were distilled under an inert atmosphere. Nitro-
methane was dried over anhydrous CaCl2 and then distilled
over 4 Å molecular sieves. Similarly, dichloromethane was dried
over anhydrous CaCl2 and then distilled over CaH2. All
reagents were used as purchased without further purification.
Columns were packed with silica gel 60 (230–400 mesh) as the
stationary phase. TLC-plates (Merck, 60F254) were visualised
using CEMOL (1% ceric sulfate and 1.5% ammonium
molybdate in 10% aqueous H2SO4) or 10% ethanolic H2SO4
(3R,4R,5S)-3,4-Dihydroxy-1,5-dimethylthianium triflate (11)
1
and heating until coloured spots appeared. 13C and H NMR
To a solution of 10 (79 mg, 0.53 mmol) in MeNO2 (1 mL)
cooled at 0 ЊC was slowly added methyl triflate (60 µL, 0.53
mmol) under N2. After 2 h the solution was concentrated to
give pure 11 (161 mg, 97%) as mixture of stereoisomers. [α]2D2
ϩ2.0 (c 0.9, H2O); S stereoisomer (equatorial): 1H NMR (D2O,
500 MHz) δ 4.07 (ddd, 1H, J3,4 2.4 Hz, J3,2ax 12.0 Hz, J3,2eq 3.7
spectra were recorded on Varian Gemini 200, Bruker AMX300
and Bruker AMX500 instruments. Mass spectra were obtained
on Micromass LCT-QTOF and Micromass AutoSpec
instruments. Specific optical rotations were measured on a
Perkin-Elmer 241 Polarimeter and are given in 10Ϫ1 deg cm2 gϪ1
.
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J. Chem. Soc., Perkin Trans. 1, 2002, 1242–1246

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Hz, H-3), 3.91 (br m, 1H, H-4), 3.47 (ddd, 1H, J2ax,2eq 11.1 Hz,
J2eq,6eq 2.5 Hz, H-2eq), 3.28 (ddd, 1H, J5,6eq 3.1 Hz, J6ax,6eq 11.8
Hz, H-6eq), 3.22 (t, 1H, H-2ax), 3.02 (dd, 1H, J5,6ax 13.1 Hz,
H-6ax), 2.98 (s, 3H, SMe), 2.21 (m, 1H, H-5), 1.17 (d, 3H, J5,5Ј
7.0 Hz, H-5Ј). 13C NMR (D2O, 125 MHz) δ 122.24 (q, 1C, JC,F
315 Hz, TfOϪ), 72.50 (C-4), 69.60 (C-3), 39.83 (C-6), 38.67
(C-2), 35.45 (C-5), 28.01 (SMe), 19.70 (C-5Ј). R stereoisomer
(axial): 1H NMR (D2O, 500 MHz) δ 4.25 (ddd, 1H, J3,4 2.2 Hz,
J3,2ax 11.3 Hz, J3,2eq 4.4 Hz, H-3), 3.91 (br m, 1H, H-4), 3.31 (dd,
1H, J2ax,2eq 14.3 Hz, H-2ax), 3.20 (ddd, 1H, J2eq,6eq 2.4 Hz,
H-2eq), 3.17 (dd, 1H, J5,6ax 12.3 Hz, J6ax,6eq 14.8 Hz, H-6ax),
3.01 (ddd, 1H, J5,6eq 3.9 Hz, H-6eq), 2.93 (s, 3H, SMe), 2.49 (m,
1H, H-5), 1.15 (d, 3H, J5,5Ј 7.1 Hz, H-5Ј). 13C NMR (D2O, 125
MHz) δ 122.24 (q, 1C, JC,F 315 Hz, TfOϪ), 72.50 (C-4), 66.53
(C-3), 34.87 (C-6), 32.90 (C-2), 32.34 (C-5), 20.99 (SMe), 19.40
(C-5Ј); m/z (ES) 475.1103 [2 (C7H15O2S)ϩ ϩ TfOϪ]. Calc. for
C15H30F3O7S3ϩ: m/z 475.1106.
2.05 (m, 1H, H-5), 1.53, 1.34 (2s, 3H each, Me2C), 1.24 (d, 3H,
J5,5Ј 7.0 Hz, H-5Ј). 13C NMR (CDCl3, 125 MHz) δ 109.44
(Me2C), 74.92 (C-4), 71.85 (C-3), 52.53 (C-2), 51.36 (C-6),
28.19, 25.41 (Me2C), 27.12 (C-5), 17.79 (C-5Ј); m/z (ES)
227.0722 (M ϩ Naϩ). Calc. for C9H16O3S ϩ Naϩ: m/z 227.0718.
(3R,4R,5S)-3,4-Dihydroxy-5-methylthiane S-oxide (14)
To a solution of 13 (30 mg, 0.15 mmol) in 4 : 1 MeOH–H2O
(1.25 mL) was added TFA (0.5 mL) at room temperature. After
30 min the solution was evaporated and the crude product was
purified by column chromatography on silica gel using CH2Cl2–
MeOH (10 : 1) as eluent to give 14 (21 mg, 88%, Rf 0.19) as a
mixture of stereoisomers. [α]2D1 Ϫ24.9 (c 2.1, H2O); R sulfoxide
(axial): 1H NMR (D2O, 500 MHz) δ 4.27 (ddd, 1H, J3,4 2.4 Hz,
J3,2ax 12.0 Hz, J3,2eq 3.8 Hz, H-3), 3.92 (br s, 1H, H-4), 3.08
(dddd, 1H, J2eq,6eq 2.9 Hz, J2ax,2eq 14.1 Hz, J4,2eq 1.0 Hz, H-2eq),
2.81 (ddd, 1H, J5,6eq 2.6 Hz, J6ax,6eq 14.1 Hz, H-6eq), 2.77 (dd,
1H, H-2ax), 2.60 (dd, 1H, J5,6ax 12.9 Hz, H-6ax), 2.53 (m, 1H,
H-5), 1.11 (d, 3H, J5,5Ј 6.8 Hz, H-5Ј). 13C NMR (D2O, 125
MHz) δ 69.86 (C-4), 62.03 (C-3), 41.92, (C-6), 40.87 (C-2),
(1R,3R,4R,5S)-1-Benzyl-3,4-dihydroxy-5-methylthianium
triflate (12)
1
To a stirred solution of triflic anhydride (36 µL, 0.22 mmol) in
CH2Cl2 (2 mL) cooled at Ϫ78 ЊC was slowly added under N2 a
solution of benzyl alcohol (22 µL, 0.22 mmol) and 2,6-di-tert-
butylpyridine (48 µL, 0.22 mmol) in CH2Cl2 (1 mL). After 10
min a solution of thiane 10 (32 mg, 0.22 mmol) in CH2Cl2 (1
mL) was added and the resulting solution was left at Ϫ20 ЊC
overnight. The crude product was evaporated to give an oily
residue which was purified by column chromatography on silica
gel using CH2Cl2–MeOH (10 : 1) as eluent (Rf 0.12). The yield
was 76 mg (90%) of 12 as a colourless oil. [α]2D2 ϩ12.0 (c 1.2,
H2O); 1H NMR (D2O, 500 MHz) δ 7.52–7.44 (m, 5H, Ph), 4.70
(d, 1H, J 13.1 Hz, SCH2Ph), 4.66 (d, 1H, SCH2Ph), 4.03 (ddd,
1H, J3,4 2.4 Hz, J3,2ax 12.0 Hz, J3,2eq 3.8 Hz, H-3), 3.83 (br t, 1H,
H-4), 3.29 (ddd, 1H, J2ax,2eq 10.9 Hz, J2eq,6eq 3.0 Hz, H-2eq), 3.14
(dd, 1H, H-2ax), 3.04 (dt, 1H, J5,6eq 3.0 Hz, J6ax,6eq 11.6 Hz,
H-6eq), 2.90 (dd, 1H, J5,6ax 13.0 Hz, H-6ax), 2.14 (m, 1H, H-5),
1.10 (d, 3H, J5,5Ј 6.9 Hz, H-5Ј); 13C NMR (D2O, 125 MHz)
δ 130.28, 129.97, 129.24, 125.71 (Ph), 120.90 (q, 1C, JC,F 316
Hz, TfOϪ), 71.21 (C-4), 68.51 (C-3), 48.14 (SCH2Ph), 35.54
(C-6), 34.53 (C-2), 33.94 (C-5), 18.45 (C-5Ј); m/z (ES)
627.1734 [2 (C13H19O2S)ϩ ϩ TfOϪ]. Calc. for C27H38F3O7S3ϩ: m/z
627.1732.
25.40 (C-5), 15.35 (C-5Ј). S sulfoxide (equatorial): H NMR
(D2O, 500 MHz) δ 3.85 (ddd, 1H, J3,4 2.6 Hz, J3,2ax 12.4 Hz, J3,2eq
3.3 Hz, H-3), 3.76 (br t, 1H, H-4), 3.45 (dt, 1H, J2ax,2eq 10.9 Hz,
J2eq,6eq 3.1 Hz, H-2eq), 3.16 (ddd, 1H, J6ax,6eq 11.8 Hz, J5,6eq 2.5
Hz, H-6eq), 2.91 (dd, 1H, H-2ax), 2.69 (dd, 1H, J5,6ax 13.1 Hz,
H-6ax), 1.89 (m, 1H, H-5), 1.12 (d, 3H, J5,5Ј 6.8 Hz, H-5Ј). 13
C
NMR (D2O, 125 MHz) δ 68.59 (C-4), 64.75 (C-3), 47.00 (C-2),
46.94 (C-6), 27.26 (C-5), 15.14 (C-5Ј); m/z (ES) 187.0404 (M ϩ
Naϩ). Calc. for C6H12O3S ϩ Naϩ: m/z 187.0405.
(3R,4R,5R)-3,4-Isopropylidenedioxy-5-methylthiane S,S-dioxide
(15)
To a stirred solution of 9 (60 mg, 0.32 mmol) in EtOAc (2 mL)
was slowly added at room temperature a solution of 77%
m-chloroperbenzoic acid (143 mg, 0.64 mmol) in EtOAc (2 mL).
After 10 min the reaction was stopped by adding saturated aq.
Na2S2O3 (20 mL). The organic layer was then washed with
saturated aq. NaHCO3 (1 × 20 mL) and water (1 × 20 mL),
dried (Na2SO4) and concentrated to dryness. The residue was
purified by column chromatography on silica gel using pentane-
EtOAc (1 : 1) as eluent to give 15 (60 mg, 86%, Rf 0.56) as a
white solid. [α]2D1 ϩ3.6 (c 1.2, CHCl3); H NMR (CDCl3, 500
1
MHz) δ 4.51 (ddd, 1H, J3,4 4.7, J3,2ax 8.9 Hz, J3,2eq 5.9 Hz, H-3),
4.13 (dd, 1H, J4,5 3.0 Hz, H-4), 3.25 (ddd, 1H, J2eq,6eq 3.5 Hz,
J2ax,2eq 14.3 Hz, H-2eq), 3.01 (dd, 1H, J5,6ax 12.7 Hz, J6ax,6eq 14.0
Hz, H-6ax), 3.00 (dd, 1H, H-2ax), 2.77 (dt, 1H, J5,6eq 3.6 Hz,
H-6eq), 2.58 (m, 1H, H-5), 1.50, 1.37 (2s, 3H each, Me2C), 1.25
(d, 3H, J5,5Ј 7.0 Hz, H-5Ј); 13C NMR (CDCl3, 125 MHz)
δ 109.09 (Me2C), 74.72 (C-4), 72.39 (C-3), 51.03 (C-2),
50.83 (C-6), 30.04 (C-5), 27.91, 25.63 (Me2C), 17.22 (C-5Ј);
m/z (ES) 243.0663 (M ϩ Naϩ). Calc. for C9H16O4S ϩ Naϩ:
m/z 243.0667.
(3R,4R,5R)-3,4-Isopropylidenedioxy-5-methylthiane S-oxide
(13)
To a stirred solution of 9 (106 mg, 0.56 mmol) in EtOAc (3 mL)
cooled at Ϫ78 ЊC under N2 was slowly added a solution of
77% m-chloroperbenzoic acid (126 mg, 0.56 mmol) in EtOAc
(3 mL). After 10 min the reaction was stopped by adding
saturated aq. Na2S2O3 (20 mL). The organic layer was then
washed with saturated aq. NaHCO3 (1 × 20 mL) and water
(1 × 20 mL), dried (Na2SO4) and concentrated to dryness. The
residue was purified by column chromatography on silica gel
using CH2Cl2–MeOH (30 : 1) as eluent to give 13 (93 mg, 81%,
Rf 0.25) as a mixture of stereoisomers. A small quantity of
sulfone 15 could also be isolated (5 mg, 4%, Rf 0.63). [α]2D1 ϩ54.4
(c 1.2, CHCl3); R sulfoxide (axial): 1H NMR (CDCl3, 500 MHz)
δ 4.63 (ddd, 1H, J3,4 5.6 Hz, J3,2ax 7.9 Hz, J3,2eq 4.7 Hz, H-3), 4.17
(dd, 1H, J4,5 2.8 Hz, H-4), 3.01 (ddd, 1H, J2eq,6eq 1.9 Hz, J2ax,2eq
14.1 Hz, H-2eq), 2.82 [m, 1H, ½(J5,6ax ϩ J5,6eq) 8.7 Hz, H-5),
2.77 (dd, 1H, H-2ax), 2.66 (d, 2H, H-6eq, H-6ax), 1.43, 1.34 (2s,
3H each, Me2C), 1.20 (d, 3H, J5,5Ј 7.0 Hz, H-5Ј). 13C NMR
(CDCl3, 125 MHz) δ 108.54 (Me2C), 75.22 (C-4), 70.12 (C-3),
46.28 (C-6), 45.91 (C-2), 27.45, 25.41 (Me2C), 23.61 (C-5), 17.39
(3R,4R,5S)-3,4-Dihydroxy-5-methylthiane S,S-dioxide (16)
To a solution of 15 (42 mg, 0.38 mmol) in 4 : 1 MeOH–H2O
(1.25 mL) was added TFA (0.5 mL) at room temperature. After
30 min the solution was evaporated and the crude was purified
by column chromatography on silica gel using EtOAc as eluent
to give 16 (27 mg, 80%, Rf 0.38) as a white solid. [α]2D1 Ϫ6.6
(c 1.8, H2O); 1H NMR (D2O, 500 MHz) δ 4.15 (ddd, 1H, J3,4 2.4
Hz, J3,2ax 11.7 Hz, J3,2eq 4.8 Hz, H-3), 3.91 (m, 1H, H-4), 3.35
(dd, J2ax,2eq 13.6 Hz, H-2ax), 3.28 (ddd, J2eq,6eq 3.9 Hz, H-2eq),
3.09 (dd, 1H, J5,6ax 13.0 Hz, J6ax,6eq 14.3 Hz, H-6ax), 2.99 (dt,
1H, J5,6eq 3.5 Hz, H-6eq), 2.27 (m, 1H, H-5), 1.13 (d, 3H, J5,5Ј 6.9
Hz, H-5Ј); 13C NMR (D2O, 125 MHz) δ 71.91 (C-4), 69.50
(C-3), 51.40 (C-2), 51.16 (C-6), 32.55 (C-5), 17.46 (C-5Ј); m/z
(ES) 187.0404 (M ϩ Naϩ). Calc. for C6H12O3S ϩ Naϩ: m/z
187.0405.
1
(C-5Ј). S sulfoxide (equatorial): H NMR (CDCl3, 500 MHz)
δ 4.31 (ddd, 1H, J3,4 4.8 Hz, J3,2ax 10.4 Hz, J3,2eq 5.6 Hz, H-3),
3.97 (dd, 1H, J4,5 2.9 Hz, H-4), 3.38 (ddd, 1H, J2eq,6eq 2.9 Hz,
J2ax,2eq 12.0 Hz, H-2eq), 3.03 (dt, J5,6eq 2.9 Hz, J6ax,6eq 11.9 Hz,
H-6eq), 2.83 (dd, J5,6ax 11.5 Hz, H-6ax), 2.75 (dd, 1H, H-2ax),
J. Chem. Soc., Perkin Trans. 1, 2002, 1242–1246
1245

View Article Online
Table 1 Inhibition constants (Ki) in µM
Enzyme
10
11
12
14
16
α--Fucosidase (bovine kidney)
α--Fucosidase (human placenta)
73000
>100000
102
303
161
309
740
>1000
2000
>100000
8 H. Yuasa, J. Takada and H. Hashimoto, Bioorg. Med. Chem. Lett.,
2001, 11, 1137.
9 A. H. Siriwardena, A. Chiaroni, C. Riche, S. El-Daher,
B. Winchester and D. S. Grierson, J. Chem. Soc., Chem. Commun.,
1992, 1531.
10 L. Svansson, B. D. Johnston, J.-H. Gu, B. Patrick and M. B. Pinto,
J. Am. Chem. Soc., 2000, 122, 10769.
11 M. Bols, Acc. Chem. Res., 1998, 31, 1.
12 A. Hansen, T. M. Tagmose and M. Bols, Tetrahedron, 1997, 53, 697.
13 H. Liu, X. Liang, H. Søhoel, A. Bülow and M. Bols, J. Am. Chem.
Soc., 2001, 123, 5116.
14 G. Gottarelli, P. Mariani, G. P. Spada, P. Palmieri and B. Samori,
J. Chem. Soc., Perkin Trans. 2, 1981, 1529.
15 H.-J. Altenbach and G. F. Merhof, Tetrahedron: Asymmetry, 1996,
7, 3087.
16 A. Hansen, T. M. Tagmose and M. Bols, Chem. Commun., 1996,
2649.
Enzyme kinetics
The enzyme assays were carried out as described previously.30
All assays were performed at pH 6.8 and 25 ЊC. Steady state
kinetics was performed and reaction rates were measured after
possible slow-onset inhibition was essentially complete. The
inhibition constants (Ki) were obtained from the formula
Ki = [I]/(KMЈ/KM Ϫ 1), where KMЈ and KM are Michaelis–Menten
constants with and without inhibitor present (Table 1). KMЈ and
KM were obtained from a Hanes plot, which was also used
to ensure that inhibition was competitive. The following KM
values (without inhibitor) were obtained using 4-nitrophenyl
glycosides as substrates and the above conditions: α-fucosidase
(human placenta), 0.23 mM; α-fucosidase (bovine kidney), 0.24
mM.
17 A. J. H. Labuschagne, J. S. Malherbe, C. J. Meyer and D. F.
Schneider, Tetrahedron Lett., 1976, 3571.
18 M. Hori, T. Kataoka, H. Shimizu, O. Komatsu and H. Hamada,
J. Org. Chem., 1987, 52, 3668.
19 M. Oki, Y. Yamada and S. Murata, Bull. Chem. Soc. Jpn., 1988, 61,
707.
20 I. Fleming and C. P. Leslie, J. Chem. Soc., Perkin Trans. 1, 1996,
1197.
Acknowledgements
We thank the Danish National Research Council (THOR
program), the Lundbeck foundation and the Dirección General
de Enseñanza Superior e Investigación Científica of Spain
(BQU 2001–3740) for financial support. V. Ulgar thanks the
European Commission for a Marie Curie fellowship.
21 R. C. Roemmele and H. Rapoport, J. Org. Chem., 1989, 54,
1866.
22 P. N. Guivisdalsky and R. Bittman, J. Org. Chem., 1989, 54,
4643.
References
23 E. Breitmaier and G. Bauer, 13C NMR Spectroscopy, a Working
Manual with Exercises, Harwood Academic Publishers, London,
1984, pp. 54–57.
1 L. J. Scott and C. M. Spencer, Drugs, 2000, 59, 521.
2 P. E. Goss, C. L. Reid, D. Bailey and J. W. Dennis, Clin. Cancer Res.,
1997, 3, 1077.
3 G. S. Jacob, P. Scudder, T. D. Butters, I. Jones and D. C. Tiemeier,
in Natural Products as Antiviral Agents, eds. C. K. Chu and H. G.
Cutler, Plenum Press, New York, 1992, pp. 137–151.
4 J. Alper, Science, 2001, 291, 2338.
24 R. L. Willer and E. L. Eliel, Org. Magn. Reson., 1977, 5, 285.
25 G. C. Barret, in Comprehensive Organic Chemistry. The Synthesis
and Reactions of Organic Compounds, ed. D. N. Jones, Pergamon
Press, Oxford, 1979, Vol. 3, pp. 105–119.
26 C. J. Clayton and N. A. Hughes, Carbohydr. Res., 1975, 45, 55.
27 H. Yuasa, A. Takenaka and H. Hashimoto, Bull. Chem. Soc. Jpn.,
1990, 63, 3473.
5 W. G. Laver, N. Bischofberger and R. G. Webster, Sci. Am., 1999,
280(1), 78.
6 M. Yoshikawa, T. Murakami, H. Shimada, H. Matsuda,
J. Yamahara, G. Tanabe and O. Muraoka, Tetrahedron Lett., 1997,
38, 8367.
7 M. Yoshikawa, T. Murakami, K. Yashiro and H. Matsuda, Chem.
Pharm. Bull., 1998, 46, 1339.
28 C. R. Johnson and D. McCants Jr., J. Am. Chem. Soc., 1965, 87,
1109.
29 S. U. Hansen and M. Bols, J. Chem. Soc., Perkin Trans 1, 2000, 911.
30 M. Bols, R. G. Hazell and I. B. Thomsen, Chem. Eur. J., 1997, 3,
940.
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J. Chem. Soc., Perkin Trans. 1, 2002, 1242–1246