Asymmetric synthesis of the L-fuco-nojirimycin, a nanomolar α-L-fucosidase inhibitor

Article abstract of DOI:10.1016/j.bmcl.2005.11.100

We describe the asymmetric synthesis of the 5-amino-5-deoxy-l-fucose (l-fuco-nojirimycin) which appears as a very potent fucosidase inhibitor with a K_i value of 1 nM.

Full text of DOI:10.1016/j.bmcl.2005.11.100

Bioorganic & Medicinal Chemistry Letters 16 (2006) 1172–1174
Asymmetric synthesis of the L-fuco-nojirimycin, a nanomolar
a-L-fucosidase inhibitor
*
´
Mathieu Dubernet, Albert Defoin and Celine Tarnus
Laboratoire de Chimie Organique et Bioorganique, UMR 7015, Ecole Nationale Supe´rieure de Chimie de Mulhouse,
Universite´ de Haute-Alsace, 3, rue Alfred Werner, F-68093 Mulhouse Ce´dex, France
Received 2 November 2005; revised 23 November 2005; accepted 24 November 2005
Available online 20 December 2005
Abstract—We describe the asymmetric synthesis of the 5-amino-5-deoxy-L-fucose (L-fuco-nojirimycin) which appears as a very
potent fucosidase inhibitor with a Ki value of 1 nM.
Ó 2005 Elsevier Ltd. All rights reserved.
The L-fucose is a more lipophilic sugar and has unusual
HO
HO
HO
HO
NH
properties. It is implicated in polysaccharide motives, as
Sialyl Lewis X, which are important for inflammation
processes and tumour migration.1–3 The design of fucose
mimics or the synthesis of nonhydrolysable analogues
may be of biological importance.
NH
R
R
OH
L-1a R = H
2a R = H
b R = OH
b R = OH
c R = β-CH2OH
c R = α-CH2CH2OH
Potent fucosidase inhibitors have already been described
in L-fucose and L-lyxose series (Scheme 1). 1-Deoxy- or
homo-L-fuco-nojirimycin derivatives L-1a, L-1c are
nanomolar inhibitors of a-L-fucosidase from various
sources.4–8 Amino-L-lyxose sugar 2b9,10 and its 1-de-
oxy-derivative 2a9–11 are likewise potent inhibitors of
the a-L-fucosidase of bovine kidney; the a-homo deriva-
tive 2c has also a Ki value in the nanomolar range.12
Scheme 1.
O
MeO OMe
O
Cl
O
NO
O
O
3
4
We describe the asymmetric synthesis and the enzymatic
evaluation of the L-fuco-nojirimycin L-1b, which is a
new analogue of nojirimycin and which looks like a
promising fucosidase inhibitor. We had already de-
scribed the synthesis of its D-enantiomer D-1b via an
asymmetric hetero-Diels–Alder reaction between sorbal-
dehyde dimethylacetal (3) and the chloro-nitroso dieno-
phile 4 in the D-mannose series13,14 (Scheme 2). This
chiral dienophile had been developed by Kresze and
Vasella.15 Using the same methodology and the previ-
ously reported concurrent chloro-nitroso dienophiles
6a,b in the 5-O-trityl-16 and the 5-O-acetyl-D-ribose17
RO
RO
O
O
Cl
NO
NOH
tBuOCl
O
O
O
O
6a R = CPh3
b R = Ac
5a R = CPh3
b R = Ac
Scheme 2.
series, respectively, the enantiomeric adduct has been
prepared. An interesting comparison of these parent
dienophiles is now possible.
Keywords: fuco-Nojirimycin; Fucosidase inhibitors; Asymmetric
synthesis.
Diels–Alder reaction of hexadienal dimethylacetal (3)18
with chloro-nitroso dienophiles 6a,b was carried out as
*
Corresponding author. Tel.: +33 03 89 33 68 64; fax +33 03 89 33 68
75; e-mail: A.Defoin@uha.fr
0960-894X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2005.11.100

M. Dubernet et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1172–1174
1173
MeO OMe
1. Ba(OH)2
2. H2-Pd/C
MeO OMe
HO
HO
NH
6(S)
O
RO
RO
L-12
6a or 6b
c
O
N
3
NR
a
CO2Bn
OH
L-1a
3(S)
Ba(OH)2
L-8a R,R = H,H
b R,R = SO2
L-7a R = H, HCl
b R = CO2Bn
d
b
HO
HO
HO
HO
HO
HO
MeO OMe
MeO OMe
NH
NH
OH
N
+
+
AcO
O
HO
OH
e
O
N
L-8b
+
OH
OH
OH
N
HO
CO2Bn AcO
CO2Bn
L-1b (imine)
L-1b (α)
L-1b (β)
L-10
L-9
MeO OMe
Scheme 4.
one 5b.17 Determined enantiomeric excess (ee)19 of L-8a
was good (ca. 95%) and independent of the 5-substitu-
tion of the dienophile. This ee was similar to the one ob-
served when hexadienoic acid was reacted with the
dienophile 6b.17 Regarding the overall yields and the ee
values which are given in Table 1, the mannose derivative
4 gave the best results among these dienophiles.
HO
HO
HO
HO
g
f
NH
O
N
L-9 +L-10
SO3H
CO2Bn
OH
L-12
L-11
Scheme 3. Reagents and conditions: (a) HC(OMe)3, MeOH, ꢀ10 °C,
16–24 h; (b) aq Na2CO3, ClCO2Bn, 0 °C, 16 h; (c) cat. OsO4, N-
methyl-morpholine N-oxide, acetone/H2O, 40 °C, 16 h, yield 10% or
17% from 3; (d) 1—SOCl2, CH2Cl2, NEt3, 2—RuCl3, NaIO4, yield
90%; (e) 1—AcONH4, DMF, 70 °C; 2—cat. H2SO4, dioxane; (f) 1—
Tf2O, CH2Cl2, pyridine; 2—NaNO2, DMF, 30 °C; 3—Na2CO3,
MeOH, yield 65% from L-8b; (g) 1—H2-Pd/C, EtOH, 50 °C; 2—SO2,
H2O, 6 days, 40 °C, yield 60%.
The inversion of the two hydroxyl groups in positions 4
and 5 of diol L-8a was carried out as for the D-enantio-
mer14 (Scheme 3). The cyclic sulphate L-8b was obtained
in 90% yield by reaction with SOCl2 and oxidation of
the resulting cyclic sulfite isomers with perruthenate
ion. Opening of the sulphate L-8b with acetate anion
following by acidolysis furnished two isomeric acetate
alcohols L-9 and L-10 which were not separated. Their
hydroxyl group was inverted by action of nitrite anion
on the triflate and a subsequent methanolysis of the ace-
tate group afforded the inverted diol L-11 in 65% yield
from sulphate L-8b (60% from diol L-8a).
Table 1. Comparison of data ([a]D, overall yield, enantiomeric excess
(ee) value) for the obtained chiral diol L-8a with those of the known
enantiomer D-8a13 depending on the used dienophiles 4, 6a,b
Starting nitroso derivative
413
6a
6b
Obtained chiral diol
25
D-8a
ꢀ33
35%
>99
L-8a
+28
10%
96
L-8a
+30
17%
95
½aꢁD value (c 1, CHCl3)
Yield of diol 8a from 3
ee % value
Hydrogenolysis over Pd/C of the N-CO2Bn group and
of the N–O bond of the diol L-11 followed by hydrolysis
of the acetal group with SO2 in water at 40 °C gave the
crystalline L-fuco-nojirimycin sulfite adduct L-12, which
was isolated after dilution with EtOH in 60% yield from
diol L-11.
previously described with the mannose-derived dieno-
phile 413 (Schemes 2 and 3): diene 3 (1–1.5 equiv) was
reacted with dienophiles 6a,b (1 equiv) in a mixture of
MeOH/methyl orthoformate at ꢀ 10 °C for 24 h. Com-
pounds 6a,b were prepared just before use by oxidation
of the corresponding oximes 5a,b with t-butyl hypochlo-
rite. The adduct was recovered as hydrochloride L-7a in
the aqueous phase after dilution with ether and extrac-
tion with an aqueous NaCl solution. Addition of excess
Na2CO3 to this aqueous solution of L-7a and acylation
with benzyl chloroformate (1 equiv) under good stirring
for 5 h furnished, after extraction with CH2Cl2, the
crude N-protected adduct L-7b (crude yield ca. 50%).
Subsequent bis hydroxylation as previously reported in
D-series13 gave the stable diol L-8a after chromatograph-
ic purification (AcOEt/cyclohexane, 1/1) in 10% or 17%
yield according to the used nitroso dienophile (Table 1).
Hydrolysis of this sulfite adduct L-12 with baryte gave
the L-fuco-nojirimycin L-1b in aqueous solution as a
mixture of the imine form and of both the a- and b-ano-
mers in 11%, 46% and 43% proportion, respectively, at
295 K as in D-series14 (Scheme 4). Hydrogenolysis over
Pd/C of this mixture led to the known deoxy-derivative
L-1a.4–7,20–22
Analytical data23 of compounds L-1b, L-8a, L-8b, L-11
and L-12 were in agreement with those of the corre-
sponding D-enantiomers13,14 as well as data of the L-1a
with those of the literature.4,20–22
Table 2. Inhibition of a-L-fucosidase from bovine kidney (Ki in lM)24
with compounds L-1a, L-1b and L-12 as well as with their D-
enantiomers14 D-1a, D-1b and D-12
Table 1 compiles some data for the diol L-8a in compar-
ison with those obtained for its enantiomer D-8a already
prepared from the nitroso-D-mannose-derivative 4.13
Lower overall yield was observed when the trityl deri-
vative 6a was used as a dienophile. This is probably
due to the difficulty in purifying the amorphous initial
oxime 5a, compared to the nicely crystallised acetylated
Compound
1a
0.003a
660
1b
12
0.001
13
L-Series
D-Series
0.001
3
a IC50 = 5 nM.

1174
M. Dubernet et al. / Bioorg. Med. Chem. Lett. 16 (2006) 1172–1174
14. Defoin, A.; Sarazin, H.; Streith, J. Tetrahedron 1997, 53,
13783.
15. Felber, H.; Kresze, G.; Prewo, R.; Vasella, A. Helv. Chim.
Acta 1986, 69, 1137; corrigendum: Braun, H.; Charles, R.;
Kresze, G.; Sabuni, M.; Winkler, J. Liebigs Ann. Chem.
1987, 1129.
Inhibition properties of the L-fuco-nojirimycin L-1b, its
deoxy-derivative L-1a and its sulfite adduct L-12 were
determined against a-L-fucosidase activity24 as well as
those of their corresponding D-enantiomers14 (Table 2).
All these compounds proved to be competitive inhibi-
tors. L-fuco-Nojirimycin L-1b and its sulfite adduct L-
12 appear to be very potent a-L-fucosidase inhibitors
with a Ki value of 1 nM. The deoxy-derivative L-1a is
a less potent inhibitor and its potency is in agreement
with the literature data against a-L-fucosidase of bovine
epididymis.4–7 Their D-enantiomers are comparatively
poor inhibitors, particularly the 1-deoxy-derivative D-1a.
16. Braun, H.; Felber, H.; Kresze, G.; Schmidtchen, Fr. P.;
Prewo, R.; Vasella, A. Liebigs Ann. Chem. 1993, 261.
17. Defoin, A.; Joubert, M.; Heuchel, J.-M.; Streith, J.
Synthesis 2000, 1719.
18. Defoin, A.; Fritz, H.; Geffroy, G.; Streith, J. Helv. Chim.
Acta 1988, 71, 1642.
19. Determination conditions of the enantiomeric excess:
column Chiralpak AD Daicel, eluent: 2-propanol/heptane
20/80, flow rate: 1 ml/min, 25 °C, k = 260 nm. Analytical
parameters: retention time for L(+)-8a Rt1 = 9.4 min, for
We have described the asymmetric synthesis of the most
potent nanomolar a-L-fucosidase inhibitor, the L-fuco-
nojirimycin (L-1b, L-fucose analogue of nojirimycin), in
a 7% overall yield from hexadienal acetal (3) or in a 36%
yield from the chiral diol L-8a. The increase of the inhibi-
tion potency for the amino-sugars L-1b, D-1b compared
to their deoxy-derivatives L-1a, D-1a points out the
importance of the anomeric hydroxyl group in the enzyme
recognition as reported for other amino-sugars.25
D(ꢀ)-8a
Rt2 = 11.2 min;
k02=k01 ¼ 1:24, Resolution = 1.33.
k01 ¼ 2:26,
k02 ¼ 2:81,
20. Takahashi, Sh.; Kuzuhara, H. J. Chem. Soc., Perkin
Trans. 1 1997, 607.
21. Paulsen, H.; Matzke, M. Liebigs Ann. Chem. 1988, 1121.
22. Polt, R.; Sames, D.; Chruma, J. J. Org. Chem. 1999, 64,
6147.
1
23. L-1a. Same H NMR data as in20,21 and for D-1a14;
20
20
½aꢁD ¼ ꢀ52 (c 1, H2O) {lit.4 ½aꢁD ¼ ꢀ48:8 (c 0.64, H2O);
20
20
lit.20 ½aꢁD ¼ ꢀ48 (c 0.2, H2O); lit.21 ½aꢁD ¼ ꢀ46:9 (c 0.61,
H2O); lit.22 [a]D = ꢀ 50 (c 1, D2O); lit.14 +49 (c 1, H2O) for
D-1a}.
Acknowledgments
1
L-1b. Same H NMR data of the imine form, a- and b-
anomers as for D-1a.14
25
20
L-8a. ½aꢁD ¼ þ30 (c 1, CHCl3) {lit.13 ½aꢁD ¼ ꢀ33 (c 1,
CHCl3) for the D-enantiomer}. Same IR and 1H NMR
data as for D-8a;13 13C NMR (CDCl3, 100 MHz, 295 K):
156.4 (CO); 136.1 (Car-s); 128.6 (2 Car-m, Car-p); 128.2 (2
Car-o); 104.3 (CH(OMe)2); 75.8 (C(6)); 68.8 (C(4)); 67.9
(CH2Ph); 64.8 (C(5)); 56.4 (OMe); 55.4 (C(3); 53.3 (OMe);
14.4 (Me-3). HR-MS (Q-Tof), calcd for C16H23NO7:
341.1475; found: 341.1431. Anal. calcd for C16H23NO7
(341.36): C, 56.29; H, 6.79; N, 4.10. Found: C, 56.1; H,
7.1; N, 4.1.
The support of the Centre National de la Recherche
Scientifique (UMR 7015) is gratefully acknowledged.
We thank Prof Jacques Streith for his interest in this
work, Mme Christiane Strehler for the determination
of the enantiomeric excess, Mr. Emmanuel Salomon
ˆ
and Dr. Isabelle Dosbaa for the determination of the
inhibition data and the student Delphine Thomas for
her participation in this work.
20
20
L-8b. ½aꢁD ¼ þ63 (c 1, CHCl3) {lit.14 ½aꢁD ¼ ꢀ68 (c 2,
1
References and notes
CHCl3) for D-8b}. Same IR and H NMR data as for D-
8b;14 13C NMR (CDCl3, 100 MHz, 295 K): 154.5 (CO);
135.2 (Car-s); 128.7 (2 Car-m); 128.6 (Car-p); 128.3
(2 Car-o); 101.8 (CH(OMe)2); 79.7 (C(4)); 76.9 (C(6));
74.7 (C(5)); 68.6 (CH2Ph); 55.8, 55.3 (OMe, C(3));
51.1(OMe); 14.2 (Me-3). HR-MS (Q-Tof), calcd for
C16H21NO9S: 403.0937; found: 403.0909. Anal. calcd for
C16H21NO9S (403.41): C, 47.64; H, 5.25; N, 3.47. Found:
C, 47.6; H, 5.5; N, 3.4.
1. Giannis, A. Angew. Chem., Int. Ed. Engl. 1994, 33, 178.
2. Sears, P.; Wong, Ch.-H. J. Chem. Soc., Chem. Commun.
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3. Fukuda, M. Bioorg. Med. Chem. 1995, 3, 207.
4. Fleet, G. W. J.; Shaw, A. N.; Evans, St. V.; Fellows, L. E.
J. Chem. Soc., Chem. Commun. 1985, 841.
5. Winchester, B.; Barker, Ch.; Baines, S.; Jacob, G. S.;
Namgoong, S. K.; Fleet, G. Biochem. J. 1990, 265, 277.
6. Paulsen, H.; Matzke, M.; Orthen, B.; Nuck, R.; Reutter,
W. Liebigs Ann. Chem. 1990, 953.
7. Takayama, S.; Martin, R.; Wu, J.; Laslo, K.; Siusdak, G.;
Wong, C.-H. J. Am. Chem. Soc. 1997, 119, 8146.
8. Fleet, G. W. J.; Namgoong, S. K.; Barker, Ch.; Baines, S.;
Jacob,G.S.;Winchester,B.TetrahedronLett.1989,30,4439.
9. Joubert, M.; Defoin, A.; Tarnus, C.; Streith, J. Synlett
2000, 1366.
10. Wong, Ch.-H.; Provencher, L.; Porco, J. A., Jr.; Jung,
S.-H.; Wang, Y.-F.; Chen, L.; Wang, R.; Steensma, D.
H. J. Org. Chem. 1995, 60, 1492.
11. Bierer, Lars, Ph.D Thesis, Stuttgart University, Germany,
1999 (Ki = 0.7 lM for 2a against L-fucosidase of bovine
epididymis).;
12. Chevrier, C.; Le Noue¨n, D.; Neuburger, M.; Defoin, A.;
Tarnus, C. Tetrahedron Lett. 2004, 45, 5363.
13. Defoin, A.; Sarazin, H.; Streith, J. Tetrahedron 1997, 53,
13769.
20
20
L-11. ½aꢁD ¼ þ24 (c 1, CHCl3) {lit.14 ½aꢁD ¼ ꢀ19 (c 1,
1
CHCl3) for D-11}. Same IR and H NMR data as for D-
1114; 13C NMR (CDCl3, 100 MHz, 295 K): 154.9 (CO);
135.8 (Car-s); 128.5 (2 Car-m); 128.3 (Car-p); 128.1
(2 Car-o); 101.9 (CH(OMe)2); 81.3 (C(6)); 67.9, 67.5,
67.3 (CH2Ph, C(4), C(5)); 55.8 (OMe); 54.1, 53.3 (C(3),
OMe); 12.0 (Me-3). HR-MS (Q-Tof), calcd for
C16H23NO7: 341.1475; found: 341.1436.
L-12. Mp = 242–250 °C (dec.), (lit.14 240–250 °C, dec. for
20
20
D-12). ½aꢁD ¼ ꢀ8:2 (c 1, H2O) {lit.14 ½aꢁD ¼ þ9 (c 1, H2O)
for D-12}. Same IR, H NMR and 13C NMR data as for
1
D-12.14 Anal. calcd for C6H13NO6S (227.23): C, 31.71; H,
5.77; N, 6.16; S, 14.11. Found: C, 31.8; H, 5.8; N, 6.0;
S, 14.2.
24. Inhibition determination conditions: acetate buffer, pH
5.5, Km = 0.15 mM, 30 °C; all measured compounds were
stable under these conditions.
25. Behr, J.-B.; Chevrier, C.; Defoin, A.; Tarnus, C.; Streith,
J. Tetrahedron 2003, 59, 543.