Synthesis and Evaluation of Isourea-Type Glycomimetics Related to the Indolizidine and Trehazolin Glycosidase Inhibitor Families

Article abstract of DOI:10.1021/jo034673m

A practical synthesis of reducing isourea-derived azasugar glycomimetics related to the indolizidine and trehazolin glycosidase inhibitor families with different pK_a values is disclosed. The polyhydroxylated bicyclic system was built from readi

Full text of DOI:10.1021/jo034673m

Syn th esis a n d Eva lu a tion of Isou r ea -Typ e Glycom im etics Rela ted
to th e In d olizid in e a n d Tr eh a zolin Glycosid a se In h ibitor F a m ilies
M. Isabel Garc´ıa-Moreno,† Paula D´ıaz-Pe´rez,† Carmen Ortiz Mellet,*,† and
J ose´ M. Garc´ıa Ferna´ndez*,‡
Departamento de Quı´mica Orga´nica, Facultad de Quı´mica, Universidad de Sevilla,
E-41071 Sevilla, Spain, and Instituto de Investigaciones Quı´micas, CSIC, Ame´rico Vespucio s/ n,
Isla de la Cartuja, E-41092 Sevilla, Spain
jogarcia@cica.es; mellet@us.es
Received May 20, 2003
A practical synthesis of reducing isourea-derived azasugar glycomimetics related to the indolizidine
and trehazolin glycosidase inhibitor families with different pKa values is disclosed. The polyhy-
droxylated bicyclic system was built from readily accessible hexofuranose derivatives through a
synthetic scheme that involves the preparation of a 5-deoxy-5-carbodiimido adduct by tri-
phenylphosphine-mediated tandem Staudinger-aza-Wittig-type coupling of azide and isothiocyanate
precursors, intramolecular cyclization of a transient vic-hydroxycarbodiimide derivative, and
nucleophilic addition of the endocyclic nitrogen atom of the generated 2-amino-2-oxazoline
intermediate, with a pseudo-C-nucleoside structure, to the masked aldehyde group of the
monosaccharide. The last step is pH-dependent so that the final compounds can pivot between the
furanose and the 2-oxaindolizidine forms. Nevertheless, the indolizidine tautomer having the R
configuration at the aminoacetalic center, fitting the anomeric effect, was the only species detected
in solution at neutral or slightly acidic pH when starting from solutions at basic pH. Glycosidase
inhibition tests (Ki values down to 1.9 µM) showed a marked dependence of the selectivity and
potency toward R- and â-glucosidases upon the nature of the substituent at the exocyclic isourea
nitrogen, shifting from R- to â-selectivity when going from hydrophilic to hydrophobic substituents.
Enzyme inhibition is also pH dependent, supporting a dominant role for the uncharged form of the
polyhydroxyiminoindolizidine system in the inhibition of â-glucosidases.
In tr od u ction
members of this class of compounds, termed generically
iminosugars (“azasugars”).8 Their pronounced biological
activity has been ascribed to their ability to mimic the
transition state involved in enzymatic glycoside hydroly-
sis. Thus, 1 can be regarded as a stereochemical mimic
Naturally occurring and synthetic polyhydroxylated
alkaloids with glycosidase inhibitory properties1 have
been receiving a great deal of attention both as useful
biochemical tools for studies on glycoconjugate function,
targeting, and turnover2 and as potential chemothera-
peutic agents for the treatment of viral infections,3
cancer,4 autoimmune pathologies,5 and diabetes and
other metabolic disorders.6 Indolizidine alkaloids, of
which (+)-castanospermine (1) is one of the more promi-
nent derivatives,7 rank among the most interesting
(2) For leading reviews, see: (a) Vasella, A.; Davies, G. J .; Bo¨hm,
M. Curr. Opin. Chem. Biol. 2002, 6, 619. (b) Heightman, T. D.; Vasella,
A. Angew. Chem., Int. Ed. Engl. 1999, 38, 750. (c) Sears, P.; Wong,
C.-H. Chem. Commun. 1998, 1161. (d) Dwek, R. A. Chem. Rev. 1996,
96, 683. (e) Kaushal, G. P.; Elbein, A. D. Methods Enzymol. 1994, 230,
316. (f) Nishimura, Y. Glycosidase and Glycosyltransferase Inhibitors.
In Studies in Natural Products Chemistry; Atta-ur-Rahman, Ed.;
Elsevier: Amsterdam, 1992; Vol. 10, p 495. (g) Winchester, B.; Fleet,
G. W. J . Glycobiology 1992, 2, 199. (h) Legler, G. Adv. Carbohydr.
Chem. Biochem. 1990, 48, 319. (i) Sinnot, M. L. Chem. Rev. 1990, 9,
1171. (j) Elbein, A. D. Annu. Rev. Biochem. 1987, 56, 497.
(3) (a) Greimel, P.; Spreitz, J .; Stu¨tz, A. E.; Wrodnigg, T. M. Curr.
Top. Med. Chem. 2003, 3, 513. (b) Zitzmann, N.; Mehta, A. S.; Carroue´e,
S.; Butters, T. D.; Platt, F. M.; McCauley, J .; Blumberg, B. S.; Dwek,
R. A.; Block, T. M. Proc. Natl. Acad. Sci. U. S. A. 1999, 96, 11878. (c)
van den Broek, L. A. G. M. Azasugars: Chemistry and Their Biological
Activity as Potential Anti-HIV Drugs. In Carbohydrates in Drug
Design; Witczak, Z. J ., Nieforth, K. A., Eds.; Marcel Dekker: New York,
1997; p 471. (d) Carlson, G. B.; Butters, T. D.; Dwek, R. A.; Platt, F.
M. J . Biol. Chem. 1993, 268, 570. (e) Taylor, D. L.; Sunkara, P. S.;
Liu, P. S.; Kang, M. S.; Bowlin, T. L.; Tyms, A. S. AIDS 1991, 5, 693.
(f) Sunkara, P. S.; Taylor, D. L.; Kang, M. S.; Bowlin, T. L.; Liu, P. S.;
Tyms, A. S.; Sjoerdsma, A. Lancet 1989, 1206. (g) Karpas, A.; Fleet,
G. W. J .; Dwek, R. A.; Petursson, S.; Namgoong, S. K.; Ramsden, N.
G.; J acob, G. S.; Rademacher, T. W. Proc. Natl. Acad. Sci. U. S. A.
1988, 85, 9229.
† Universidad de Sevilla.
‡ Instituto de Investigaciones Qu´ımicas.
(1) For recent reviews on alkaloid glycosidase inhibitors, see: (a)
Asano, N. Curr. Top. Med. Chem. 2003, 3, 471. (b) Lillelund, V. H.;
J ensen, H. H.; Liang, X.; Bols, M. Chem. Rev. 2002, 102, 515. (c)
Watson, A. A.; Fleet, G. W. J .; Asano, N.; Molyneux, R. J .; Nash, R. J .
Phytochemistry 2001, 56, 265. (d) Asano, N.; Nash, R. J .; Molyneux,
R. J .; Fleet, G. W. J . Tetrahedron: Asymmetry 2000, 11, 1645. (e)
Elbein, A. D.; Molyneux, R. J . Alkaloid Glycosidase Inhibitors. In
Comprehensive Natural Products Chemistry; Barton, D., Nakanishi,
K., Meth-Cohn, O., Eds.; Elsevier: Oxford, 1999; Vol. 3, p 129. (f)
Simmonds, M. S. J .; Kite, G. C.; Porter, E. A. Taxonomic Distribution
of Iminosugars in Plants and Their Biological Activities. In Iminosug-
ars as Glycosidase Inhibitors; Stu¨tz, A., Ed.; Wiley-VCH: Weinheim,
Germany, 1999; p 8. (g) Ossor, A.; Elbein, A. D. Glycoprotein Processing
Inhibitors. In Carbohydrates in Chemistry and Biology; Ernst, B., Hart,
G. W., Sinay¨, P., Eds.; Wiley-VCH: Weinheim, Germany, 2000; Part
II, Vol. 3, p 513.
(4) For a review, see: Gross, P. E.; Baker, M. A.; Carver, J . P.;
Dennis, J . W. Clin. Cancer Res. 1995, 1, 935.
10.1021/jo034673m CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/21/2003
8890
J . Org. Chem. 2003, 68, 8890-8901

Isourea-Type Glycomimetics
of D-glucose, which is consistent with its behavior as a
potent and specific inhibitor of mammalian and plant R-
and â-glucosidases. The (6R) diastereomer, (+)-6-epi-
castanospermine (2), does not display the broad range
of biological activity inherent to (+)-castanospermine,
though it is a potent amyloglucosidase inhibitor.9
Structure-activity studies have suggested that the
rigid bicyclic structure of 1, which locks the homologous
bond to C-5-C-6 in hexopyranoses, is responsible for the
observed higher enzyme specificity as compared with the
monocyclic analogue 1-deoxynojirimycin (3).10 In connec-
tion with the design of more fine-tuned analogues,
numerous syntheses of 1 and their diastereomers have
been reported.11,12 Yet, neither 1, 2, nor any of the
plethora of synthetic analogues reported so far possess
a defined configuration at the pseudoanomeric center C-5.
It is therefore not surprising that they can inhibit
simultaneously several R- as well as â-glycosidases, which
may be particularly problematic for clinical applications.
Moreover, the bridgehead location of the nitrogen atom
in indolizidine glycomimetics prevents incorporation of
N substituents, a strategy that has led to potent and
specific glycosidase inhibitors already approved for clini-
cal trials in the piperidine series, such as N-butyl-1-
deoxynojirimycin (4)3c and the pseudodisaccharide de-
rivative MDL 73954 (5).6f
(5) (a) Walter, S.; Fassbender, K.; Gulbins, E.; Liu, Y.; Rieschel, M.;
Herten, M.; Bersch, T.; Engelhardt, B. J . Neuroimmunol. 2002, 132,
1. (b) Liu, J .; Shikman, A. R.; Lotz, M. K.; Wong, C.-H. Chem. Biol.
2001, 8, 701.
Recently we found that a subtle change in the structure
of azasugars, by replacing the amine sp3 nitrogen atom
by a pseudoamide-type (urea, thiourea, carbamate) ni-
trogen with substantial sp2 character, led to a new group
of glycosidase inhibitors with high anomer selectivity.13,14
This structural change increases the orbitalic contribu-
tion to the generalized anomeric effect in aminoacetal
centers, allowing the preparation of stable reducing sp2-
azasugar glycomimetics8 that exhibit conformational and
configurational integrity in water solution, which is
notably different than was found to be the case for
classical sp3 iminosugars.14,15 Interestingly, this electronic
feature is also present in the natural trehalase inhibitor
trahazolin (6), where the occurrence of a cyclic isourea
function allows interaction with the key bilateral groups
in the active site of the enzyme as well as additional
interactions with the aglyconic binding site, resulting in
a remarkable enzyme specificity.16 We envisioned that,
by combining the essential structural features of poly-
hydroxyindolizidines and trehazolin, i.e., a bicyclic oc-
tahydroindolizine framework and a fused 2-aminooxazo-
line ring, new sp2-azasugar systems endowed with the
advantages of both models could be generated. This
principle has been translated into a practical synthesis
of reducing 2-oxa-3-iminoindolizidine glycomimetics17
(Figure 1, structure I), a hitherto unknown class of
compounds, from 2-aminooxazoline carbohydrate precur-
sors. Like 1 or 2, structure I can be seen as a conforma-
(6) (a) Butters, T. M.; Dwek, R. A.; Platt, F. M. Curr. Top. Med.
Chem. 2003, 3, 561. (b) Platt, F. M.; Neises, G. R.; Reinkensmeier, G.;
Townsend, M. J .; Perry, V. H.; Proia, R. L.; Winchester, B. G.; Dwek,
R. A.; Butters, T. D. Science 1997, 276, 428. (c) Witczak, Z. J .
Carbohydrates as New and Old Targets for Future Drug Design. In
Carbohydrates in Drug Design; Witczak, Z. J ., Ed.; Marcel Dekker:
New York, 1997; p 1. (d) Balfour, J . A.; McTavish, D. Drugs 1993, 46,
1025. (e) Robinson, K. M.; Begovic, M. E.; Rhinehart, B. L.; Heineke,
E. W.; Ducep, J .-B.; Kastner, P. R.; Marshall, F. N.; Danzin, C. Diabetes
1991, 40, 825. (f) Anzeveno, P. B.; Creemer, L. J .; Daniel, J . K.; King,
C.-H.; Liu, P. S. J . Org. Chem. 1989, 54, 2539.
(7) For reviews, see: (a) Michael, J . P. Nat. Prod. Rep. 2002, 18,
719. (b) Tyler, P. C.; Winchester, B. G. Synthesis and Biological Activity
of Castanospermine and Close Analogs. In Iminosugars as Glycosidase
Inhibitors; Stu¨tz, A., Ed.; Wiley-VCH: Weinheim, Germany, 1999; p
125. (c) Michael, J . P. Nat. Prod. Reports 1997, 14, 21. (d) Cossy, J .;
Vogel, P. In Studies in Natural Products Chemistry; Atta-ur Rahman,
Ed.; Elsevier: New York, 1993; Vol. 12, p 275. (e) Burgess, K.;
Henderson, I. Tetrahedron 1992, 48, 4045.
(8) Although the term “azasugar” is widely used in the literature to
refer to glycomimetics where the endocyclic oxygen atom has been
replaced by nitrogen, the term is not strictly correct according to the
IUPAC-IUBM nomenclature recommendations for carbohydrates, the
accepted term being “iminosugar”. “Azahexose” would actually imply
that a carbon atom has been exchanged for a nitrogen atom. See:
McNaught, A. D. Pure Appl. Chem. 1996, 68, 1919. By analogy with
the trivial name “azasugar”, we are using here the term “sp2-azasugar”
to refer to glycomimetics where the endocyclic oxygen atom has been
replaced by a nitrogen atom with substantial sp2 character, typically
a pseudoamide-type nitrogen.
(9) Ekhart, C. W.; Fechter, M. H.; Hadwiger, P.; Mlaker, E.; Stu¨tz,
A. E.; Tauss, A.; Wrodnigg, T. M. Tables of Glycosidase Inhibitors with
Nitrogen in the Sugar Ring and Their Inhibitory Activities. In
Iminosugars as Glycosidase Inhibitors; Stu¨tz, A., Ed.; Wiley-VCH:
Weinheim, Germany, 1999; p 253.
(10) Winchester, B. G.; Cenci di Bello, I.; Richardson, A. C.; Nash,
R. J .; Fellows, L. E.; Ramsden, N. G.; Fleet, G. W. J . Biochem. J . 1990,
269, 227.
(13) (a) Garc´ıa-Moreno, M. I.; Benito, J . M.; Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J . M. J . Org. Chem. 2001, 66, 7604. (b) Garc´ıa Ferna´ndez,
J . M.; Ortiz Mellet, C.; Benito, J . M.; Fuentes, J . Synlett 1998, 316.
(14) (a) D´ıaz Pe´rez, V. M.; Garc´ıa-Moreno, M. I.; Ortiz Mellet, C.;
Fuentes, J .; Garc´ıa Ferna´ndez, J . M.; D´ıaz Arribas, J . C.; Can˜ada, F.
J . J . Org. Chem. 2000, 65, 136. (b) J ime´nez Blanco, J . L.; D´ıaz Pe´rez,
V. M.; Ortiz Mellet, C.; Fuentes, J .; Garc´ıa Ferna´ndez, J . M.; D´ıaz
Arribas, J . C.; Can˜ada, F. J . Chem. Commun. 1997, 1969.
(15) (a) D´ıaz Pe´rez, P.; Garc´ıa-Moreno, M. I.; Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J . M. Synlett 2003, 341. (b) Garc´ıa-Moreno, M. I.; Ortiz
Mellet, C.; Garc´ıa Ferna´ndez, J . M. Tetrahedron: Asymmetry 1999,
10, 4271. (d) J ime´nez Blanco, J . L.; Ortiz Mellet, C.; Fuentes, J .; Garc´ıa
Ferna´ndez, J . M. Tetrahedron 1998, 54, 14123.
(11) Selected recent syntheses of (+)-castanospermine and related
polyhydroxyindolizidines: (a) Ayad, T.; Ge´nisson, Y.; Baltas, M.;
Gorrichon, L. Chem. Commun. 2003, 582. (b) Zhang, H.-X.; Xia, P.;
Zhou, W.-S. Tetrahedron 2003, 59, 2015. Somfai, P.; Marchand, P.;
Torsell, S.; Lindstro¨m, U. M. Tetrahedron 2003, 59, 1293. (c) Zhao,
H.; Hans, S.; Cheng, X.; Mootoo, D. R. J . Org. Chem. 2001, 66, 1761.
(d) Paolucci, C.; Mattioli, L. J . Org. Chem. 2001, 66, 4787. (e) Socha,
D.; J urczac, J .; Chmielewski, M. Carbohydr. Res. 2001, 336, 315. (f)
Patil, N. T.; Tilekar, J . N.; Dhavale, D. D. Tetrahedron Lett. 2001, 42,
747. (g) Izquierdo, I.; Plaza, M. T.; Robles, R.; Mota, A. J . Eur. J . Org.
Chem. 2000, 2071. (h) Denmark, S. E.; Martinborough, E. A. J . Am.
Chem. Soc. 1999, 121, 3046. (i) Kang, S. H.; Kim, J . S. Chem. Commun.
1998, 1353.
(16) For reviews on trehazolin and close analogues, see: (a) Bere-
cibar, A.; Grandjean C.; Siriwardena, A. Chem. Rev. 1999, 99, 779. (b)
Kobayashi, Y. Carbohydr. Res. 1999, 315, 3.
(17) Garc´ıa-Moreno, M. I.; D´ıaz Pe´rez, P.; Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J . M. Chem. Commun. 2002, 848.
(12) Syntheses of ring-modified (+)-castanospermine analogues: (a)
Svansson, L.; J ohnston, B. D.; Gu, J .-G-; Patrick, B.; Pinto, B. M. J .
Am. Chem. Soc. 2000, 122, 10769. (b) Gradnig, G.; Berger, A.;
Grassberger, V.; Stu¨tz, G.; Legler, G. Tetrahedron Lett. 1991, 32, 4889.
J . Org. Chem, Vol. 68, No. 23, 2003 8891

Garc´ıa-Moreno et al.
group and trimethylsilylation of the primary alcohol
function led to the selectively protected azide inter-
mediate 8. Attempts to generate the corresponding
triphenylphosphinimine (iminophosphorane, λ5-phos-
phazene, RsNdPPh3) by the Staudinger reaction21 of
8 with triphenylphosphine required long reaction times
and temperatures, leading to the formation of several
byproducts. Nevertheless, when the reaction was effected
in the presence of n-butyl, n-octyl, or phenyl isothio-
cyanate, the tandem Staudinger-aza-Wittig type trans-
formation21 proceeded smoothly to give the carbodi-
imide adducts 11-13. Probably the reaction occurs in this
case through a transient phosphazide (triazaphospha-
zene, RsNdNsNdPPh3), a known intermediate in the
Staudinger reaction,22 instead of the phosphinimine.
Similar trends have previously been observed in the
preparation of other sugar carbodiimides.23 Analogously,
reaction of azide 8 with triphenylphosphine and in situ
coupling with 2,3,4,6-tetra-O-acetyl-â-D-glucopyranosyl
isothiocyanate24 (9, rt) or methyl 2,3,4-tri-O-acetyl-6-
deoxy-6-isothiocyanato-R-D-glucopyranoside25 (10, 80 °C)
yielded the (1 f 5) and (6 f 5) carbodiimide-bridged
pseudodisaccharides 14 and 15, respectively (Scheme 1).
The isolated yields varied from 70 to 75% for isothiocy-
anate reagents bearing electron-withdrawing groups (i.e.,
phenyl and glucopyranosyl) to 40-60% for alkyl-type
isothiocyanates.
F IGURE 1. Retrosynthesis of reducing 2-oxa-3-iminoindolizi-
dine derivatives (I) from aldohexofuranose-derived 2-aminoox-
azoline precursors (II).
tionally restricted monosaccharide analogue that retains
the hydroxylation profile of the parent hexose. It also
incorporates an aminoacetalic hydroxy group, anchored
in the axial orientation, like the natural aglycons in
R-glycopyranosides. In addition, incorporation of different
substituents at the exocyclic nitrogen could be used to
modulate the enzyme specificity, as is the case for
trehazolin-type glycomimetics. Herein, we report a full
account on the preparation of indolizidine-trehazolin
hybrids structurally related to (+)-castanospermine (1)
and (+)-6-epicastanospermine 2 as well as of the key
intermediates. The scope and limitations of the methods
and the structure, glycosidase inhibitory selectivities and
potency relationships, are also discussed.
Resu lts
Retr osyn th esis. Assembly of the bicyclic skeleton of
isourea-type indolizidine glycomimetics from carbohy-
drate precursors represents a very interesting challenge.
A retrosynthetic analysis revealed that the 2-oxa-3-
iminoindolizidine framework can be constructed by in-
tramolecular nucleophilic addition of the endocyclic
nitrogen atom of 2-aminooxazoline intermediates to a
suitably located carbonyl group with simultaneous gen-
eration of the aminoacetal function (Figure 1). A key
feature in the synthetic planning will be to introduce the
five-membered cyclic isourea segment onto an aldohexo-
furanose template. Our synthetic strategy relies on the
ability of the masked aldehyde group of the monosac-
charide to act as the electrophilic target for the nitrogen
atom of azole heterocycles with a pseudo-C-nucleoside
structure through the open-chain tautomeric form. Hy-
droxylation profiles analogous to those of 1 and 2 in the
final compounds (Figure 1, structure I) imply D-gluco and
D-manno configurations, respectively, of the 2-aminoox-
azoline precursors (Figure 1, structure II).
Isou r ea -Typ e (+)-Ca sta n osp er m in e-Rela ted Gly-
com im etics. The initial synthetic objective of this re-
search was the preparation of reducing 2-oxa-3-imino-
(+)-castanospermine analogues, that is, 2-amino-2-
oxazoline-piperidine bicyclic derivatives with an orienta-
tional pattern for the hydroxy groups at the six-
membered ring analogous to that of R-D-glucopyranose.
A new methodology has been developed for the construc-
tion of the cyclic isourea ring that exploits the reactivity
of sugar carbodiimides, avoiding the use of hazardous
reagents, such as mercury salts or isocyanates, generally
employed in the reported syntheses of trehazolin ana-
logues from thiourea18 or urea19 intermediates. Conven-
tional acetylation of 5-azido-5-deoxy-1,2-isopropylidene-
6-O-tetrahydropyranyl-R-D-glucofuranose 7,20 available in
multigram scale from commercial D-glucurono-6,3-lac-
tone, followed by hydrolysis of the tetrahydropyranyl
Further removal of the silyl ether group in 11-15 with
tetra-n-butylammonium fluoride proceeded with sponta-
neous intramolecular nucleophilic addition of the gener-
ated hydroxyl group to the vicinal heterocumulene func-
tionality, to give the required (4R)-4-(L-threofuranos-4′-
yl)-2-amino-2-oxazoline pseudo-C-nucleoside derivatives
16-20. In the case of the glucosyl derivative 14, buffering
the reaction mixture with acetic acid was necessary to
avoid partial epimerization of the resulting glucosylami-
nooxazoline at the anomeric position26 (Scheme 2, a and
b).
(18) Syntheses of cyclic isourea (“trahazoloid”) glycomimetics from
thiourea precursors: (a) Boiron, A.; Zilling, P.; Faber, D.; Giese, B. J .
Org. Chem. 1998, 63, 5877. (b) Li, J .; Lang, F.; Ganem, B. J . Org. Chem.
1998, 63, 3403. (c) Ledford, B. E.; Carreira, E. M. J . Am. Chem. Soc.
1995, 117, 11811. (d) Knapp, S.; Purandare, A.; Rupitz, K.; Withers,
S. G. J . Am. Chem. Soc. 1994, 116, 7461. (e) Uchida, C.; Kitahashi,
H.; Yamagishi, T.; Iwasaki, Y.; Ogawa, S. J . Chem. Soc., Perkin Trans.
1 1994, 2775. (f) Uchida, C.; Yamagishi, T.; Ogawa, S. J . Chem. Soc.,
Perkin Trans. 1 1994, 589. (g) Shiozaki, M.; Arai, M.; Kobayashi, Y.;
Kasuya, A.; Miyamoto, S. J . Org. Chem. 1994, 59, 4450. (h) Kobayashi,
Y.; Miyazaki, H.; Shiozaki, M. J . Org. Chem. 1994, 59, 813. (i)
Kobayashi, Y.; Miyazaki, H.; Shiozaki, M. J . Am. Chem. Soc. 1992,
114, 10065.
(19) Syntheses from urea precursors: (a) de Gracia, I. S.; Bobo, S.;
Mart´ın-Ortega M. D.; Chiara, J . L. Org. Lett. 1999, 11, 1795. (b) Garc´ıa
Ferna´ndez, J . M.; Ortiz Mellet, C.; Pradera Adria´n, M. A.; Fuentes
Mota, J . Carbohydr. Res. 1991, 216, 21.
(20) Dax, K.; Caigg, B.; Grassberger, V.; Ko¨lblinger, B.; Stu¨tz, A. E.
J . Carbohydr. Chem. 1990, 9, 479.
(21) For reviews, see: (a) Molina, P.; Vilaplana, M. J . Synthesis
1994, 1197. (b) Eguchi, S.; Matsushita, Y.; Yamashita, K. Org. Prep.
Proced. Int. 1992, 24, 209. (c) Gololobov, Y. G.; Kaskhin, L. F.
Tetrahedron 1992, 48, 1353. (d) Barluenga, J .; Palacios, F. Org. Prep.
Proced. Int. 1991, 23, 1.
(22) Alajar´ın, M.; Molina, P.; Lo´pez-La´zaro, A.; Foces-Foces, C.
Angew. Chem., Int. Ed. 1997, 36, 67.
(23) Garc´ıa Ferna´ndez, J . M.; Ortiz Mellet, C.; D´ıaz Pe´rez, V. M.;
Fuentes, J .; Kova´cs, J .; Pinte´r, I. Carbohydr. Res. 1997, 304, 261.
(24) Camarasa, M. J .; Ferna´ndez-Resa, P.; Garc´ıa-Lo´pez, M. T.; de
las Heras, F. G.; Me´ndez-Castrillo´n, P. P.; San Fe´lix, A. Synthesis 1984,
509.
(25) Garc´ıa Ferna´ndez, J . M.; Ortiz Mellet, C.; Fuentes, J . J . Org.
Chem. 1993, 58, 5192.
8892 J . Org. Chem., Vol. 68, No. 23, 2003

Isourea-Type Glycomimetics
SCHEME 1a
SCHEME 2a
a
Reagents and conditions: (i) TBAF in THF, 0 °C, 25 min; (ii)
a
Reagents and conditions: (i) (a) Ac2O-pyridine, (b) p-tolu-
TBAF in THF, AcOH (pH 7), 0 °C, 25 min
enesulfonic acid, (c) Me3SiCl, hexamethyldisilazane, pyridine; (ii)
PPh3, RNCS (R ) n-Bu, n-octyl, Ph), toluene, 80 °C (R ) n-Bu,
n-octyl) or rt (R ) Ph), 2.5-24 h; (iii) toluene, rt (24 h) or 80 °C (8
h)
SCHEME 3
Conventional deacetylation and hydrolysis of the acetal
protecting group in 16-20 with TFA-water led, initially,
to R,â-anomeric mixtures of the corresponding D-gluco-
furanose oxazolinium trifluoroacetate salt derivatives, as
seen from the 13C NMR and FABMS spectra of the crude
reaction mixtures.27 In the case of 16-19, the equilibrium
was spontaneously shifted toward the target 2-oxa-3-
iminoindolizidines 21-24 upon neutralization with Am-
berlite IRA 68 (OH-) ion-exchange resin (Scheme 3). The
fused bicyclic form (charged and neutral species) was the
only one detected by NMR under several pD conditions.
However, the (C-6)-linked methyl R-D-glucopyranoside
derivative 25 existed in water solution as either the
hemiacetal or the hemiaminal isomer depending not only
on the final pH but also on the starting pH value. Thus,
the product arising from the treatment of the aminoox-
azoline precursor 20 with trifluoroacetic acid and further
neutralization contained exclusively the mixture of glu-
cofuranose anomers. Only the indolizidine form was,
however, observed at pH 9, while reversion to the
furanose form occurred at pHs below 4.28
To better understand this pH-dependent behavior, the
pKa values of the 2-oxa-3-iminoindolizidines 21-25 were
potentiometrically determined. The obtained values, 4.9
(23) and 5.2 (24) for derivatives with electron-withdraw-
ing substituents and 6.9 (21), 7.0 (22), and 6.8 (25) for
derivatives with alkyl-type substituents, indicated that
the basicity of the isourea group for the isourea-type
castanospermine related glycomimetics is lower as com-
pared with trehazolin analogues (a pKa value in the range
(26) Partial anomerization of the N-â-D-glucopyranosyl substituent
in the presence of fluoride anion has also been observed during the
preparation of the â-anomer of trehazolin. See: Kobayashi, Y.;
Shiozaki, M. J . Antibiot. 1994, 47, 243.
(27) The 13C NMR spectra of the crude reaction mixtures in D2O
showed signals at 102.1-101.8 and 96.1-95.9 ppm, with similar
intensities, for the C-1 resonances of the R- and â-hexofuranose
anomers, respectively. See: Bock, K.; Pedersen, C. Adv. Carbohydr.
Chem. Biochem. 1983, 41, 27. Upon addition of 0.1 M NaOD to the
solution in the NMR tube until a neutral to slightly basic pH was
achieved, an instantaneous, virtually quantitative transformation into
the final bicyclic compound was observed. The pseudomolecular peaks
in the FABMS spectra of the crude reaction mixtures before neutral-
ization showed an 18 m/z unit increase compared to those of the final
compounds, in agreement with the proposed reaction pathway.
(28) A similar hemiacetal-hemiaminal equilibrium has been previ-
ously reported for cyclic guanidine-type glycomimetics. For these
systems, it was observed that the interconversion rate between the
two forms was slow enough to allow assuming that the species present
in solution during determination of glycosidase inhibiton constants was
that dictated by the initial pH. See: J eong, J .-H.; Murray, B. W.;
Takayama, S.; Wong, C.-H. J . Am. Chem. Soc. 1996, 118, 4227. In our
case, the interconversion rate seems to be extremely slow in a wide
range of pHs (pH 9-4 in the case of 25) and virtually instantaneous
when the limit pH values are reached.
J . Org. Chem, Vol. 68, No. 23, 2003 8893

Garc´ıa-Moreno et al.
SCHEME 4
SCHEME 5a
of 7.59-9.74 has been reported29 for 6). In the furanose
form, protonation probably takes place at the endocyclic
imino nitrogen,30 thus preventing its participation in
nucleophilic addition to the carbonyl group. At a critical
pH value (between pH 5.5 and 6.5), the proportion of the
neutral form is sufficient to promote rearrangement to
the indolizidine system, probably protonated at the imino
exocyclic nitrogen. We believe that the driving force for
this process is the gain in stabilization due to the
anomeric effect in the O-5-C-5-N fragment. Notewor-
thy, further lowering of the pH did not cause reversion
to the furanose form in compounds 21-24, probably
because the positive charge is rather localized at the
imino nitrogen atom in the iminoindolizidine species. The
different behavior observed for the N-saccharidyl deriva-
tive 25, with a pKa value virtually identical to those
measured for the N-butyl and N-octyl derivatives, may
arise from differences in charge distribution within the
amidine segment due to steric and/or solvation reasons.
Thus, a higher positive charge density at the endocyclic
nitrogen would result in the loss of the anomeric effect
at the aminoacetal center, destabilizing the six-mem-
bered ring. Under the basic conditions, the noncharged
iminoindolizidine form 25a is favored, while under strong
acidic conditions, the protonated 2-aminooxazoline-fura-
nose form 25b is the only species present in the solution
(Scheme 4). It is noteworthy that the tautomeric form of
25 at a given pH between 4 and 9 is dictated by the initial
pH of the preparation. In the evaluation of the glycosi-
dase inhibitory properties of these compounds (see here-
inafter), we have in all cases started from preparations
at basic or neutral pH, containing exclusively the imi-
noindolizidine form. Since the determination of inhibition
constants has been effected at pH 7.3-4.5, we can
assume that we have only the ratio of neutral and
uncharged isourea-type indolizidine glycomimetics dic-
tated for the corresponding pKa value and the new pH.
In the indolizine form, compounds 21-25 existed in
D2O solutions as single diastereomers. The high field
shift of the C-5 resonance, as compared with the corre-
sponding values for the anomeric carbon C-1 in the
furanose form, confirmed the aminoacetal structure,
a
Reagents and conditions: (i) DIBAL, toluene, -78 °C f rt, 2
h; (ii) Ac2O, pyridine; (iii) 50% aq AcOH, 40 °C, 2 h; (iv) TrCl,
pyridine, rt, 36 h; (v) (a) Tf2O, pyridine, CH2Cl2, -25 °C f 25 °C,
1 h, (b) NaN3, DMF, rt, 18 h; (vi) BF3‚Et2O, CH2Cl2, 0 °C f rt, 2
h; (vii) TMSCl, hexamethyldisilazane, pyridine, rt, 2 h.
ring unambiguously pointed to the 5R configuration for
the new stereocenter, with the pseudoanomeric hydroxy
group in axial position, fitting the anomeric effect.
Isou r ea -Typ e (+)-6-Ep ica sta n osp er m in e-Rela ted
Glycom im etics. To implement the above strategy of
accessing reducing 2-oxa-3-iminoindolizidines in order to
synthesize (+)-6-epicastanospermine analogues, the prepa-
ration of D-mannofuranose-derived 2-amino-2-oxazolines
was required. Our approach started from 2,3,5,6-di--
O-isopropylidene-L-gulono-γ-lactone (26),31 prepared by
acetonation of commercial L-gulono-γ-lactone. Reduction
of the carbonyl group with DIBAL and acetylation of the
resulting lactol 27 afforded the corresponding 1-O-acetyl-
â-L-gulofuranose diacetonide 28. Removal of the 5,6-
isopropylidene protecting group (f29), selective protec-
tion of the primary alcohol function as the corresponding
triphenylmethyl ether (f30), and inversion of the con-
figuration at C-5 by azide anion, via trifluromethane-
sulfonate ester, led to the 5-azido-5-deoxy-R-D-manno-
furanose derivative 31. The trityl group was then replaced
by trimethylsilyl through a two-step reaction sequence
involving selective removal by treatment with boron
trifluoride-diethyl ether complex (f32) and further
reaction with trimethylsilyl chloride-hexamethyldisila-
zane to give the key selectively protected azide precursor
33 (Scheme 5).
The reaction pathway followed for preparation of the
fused piperidine, oxazolidine derivatives 40-42, mimick-
ing the topography of (+)-6-epicastanospermine, paral-
leled that above commented for the synthesis of (+)-
castanospermine related compounds. Thus, tandem
Staudinger-aza-Wittig-type reaction of the selectively
protected azide 33 with triphenylphosphine and phenyl
isothiocyanate or the sugar isothiocyanates 9 or 10
3
whereas the vicinal J HH values around the piperidine
(29) Nakayama, T.; Amachi, T.; Murao, S.; Sakai, T.; Shin, T.;
Kenny, P. T. M.; Iwashita, T.; Zagorski, M.; Komura, H.; Nomoto, K.
J . Chem. Soc., Chem. Commun. 1991, 919.
(30) Ha¨feliger, G.; Kuske, F. K. H. General and Theoretical Aspects
of Amidines and Related Compounds. In The Chemistry of Amidines
and Imidates; Patai, S., Rappoport, Z., Eds.; Chichester, U.K., 1991;
Vol. 2, p 1.
(31) Fleet, G. W. J .; Ramsden, G.; Witty, D. R. Tetrahedron 1989,
45, 319.
8894 J . Org. Chem., Vol. 68, No. 23, 2003

Isourea-Type Glycomimetics
SCHEME 6a
Indolizidines 40-42 existed in D2O solution as single
diastereomers. The absence of NOE contacts between the
pseudoanomeric proton H-5 and the R-oriented piperidine
protons H-6 and H-8a is indicative of the axial disposition
of the aminoacetalic hydroxy group, in agreement with
the existence of a very strong and stabilizing interaction
between the π-type lone pair of the endocyclic nitrogen
of the isourea grouping and the σ* antibonding orbital
of the contiguous C-O bond. To the best of our knowl-
edge, compounds 21-25 and 40-42 represent the first
examples of ring-modified indolizidine glycomimetics
bearing exocyclic substituents.
Biologica l Activity. The inhibitory activities of the
isourea type indolizidine glycomimetics 21-25 and 40-
42 for R-glucosidase (yeast), â-glucosidase (almonds),
â-glucosidase (bovine liver, cytosolic), trehalase (pig
kidney), R-galactosidase (green coffee beans), amyloglu-
cosidase (Aspegillus niger), R-mannosidase (jack beans),
and R-fucosidase (bovine kidney) are summarized in
Table 1. The presence of a pseudoanomeric hydroxy group
anchored in the axial position was expected to be
translated into an increased selectivity toward R-glycosi-
dases. Actually, the (+)-castanospermine pseudodisac-
charide analogue 24 showed inhibition constants (Ki)
against yeast R-glucosidase (17 µM) and almond â-glu-
cosidase (212 µM) at their optimal pH (6.8 and 5.5,
respectively), indicative of a reverse selectivity as com-
pared to 1 (>1500 and 1.5 µM, respectively).9 Yet, a
strong influence of the nature of the exocyclic substituent
on the inhibition constant was observed. Thus, the C-6-
linked methyl R-D-glucopyranoside derivative 25 was a
weak inhibitor for both enzymes (Ki ) 463 and 336 µM,
respectively), whereas compounds 21-23, bearing lipo-
philic substituents, inhibited â-glucosidase more potently
than R-glucosidase. The N-octyl derivative 22 (Ki ) 3.2
µM) was about 10-fold a more potent inhibitor of this
enzyme than the N-phenyl 23 and N-butyl 21 counter-
parts (Ki ) 23 and 30 µM, respectively). Interestingly,
the inhibitory potency of 22 doubled on going from pH
5.5 to pH 7.3 (Ki ) 1.9 µM), and it additionally behaved
as a strong competitive inhibitor of the mammalian
â-glucosidase (Ki ) 2.7 µM) at the latter pH value, the
optimal for this particular enzyme. Compounds 21-23
also were weak inhibitors of trehalase. In all cases, the
enzyme inhibition mode was found to be of the competi-
tive type.
The stereochemical complementarity of the polyhy-
droxylated pyperidine ring and the putative substrate
seems to be a major requirement for glycosidase inhibi-
tion by this family of glycomimetics. Thus, in the dia-
stereoisomeric (+)-6-epicastanospermine series, the glu-
cosidase inhibitory activity was drastically diminished.
No inhibition of R-mannosidase was observed for 40-
42, despite the apparent structural similarity with
R-mannosides, as is the case for the natural compound
2.9 Neither 21-25 nor 40-42 inhibited R-galactosidase,
in agreement with the configurational specificity of the
parent indolizidine alkaloids.
The higher selectivity of 1 toward some R-glucosidases
as compared with the piperidine analogue 3 has been
ascribed to the rigidity of the bicyclic structure, which
locks the homologous bond to C-5-C-6 in hexopyrano-
sides, thereby fixing the orientation of the oxygen sub-
stituent at the position equivalent to C-6 to fully interact
a
Reagents and conditions: (i) PPh3, toluene, rt, 24 h; (ii) PPh3,
toluene, 40 °C, 24 h; (iii) (a) NaOMe, MeOH, (b) 90% aq TFA, (c)
OH-.
yielded the carbodiimide adducts 34-36, respectively.
The coupling yields (20-70%) were significantly lower
as compared with the D-gluco series, probably due to the
steric hindrance imposed by the cis-oriented isopropy-
lidene group. Removal of the silyl ether functionality
using tetra-n-bytulammonium fluoride provided the re-
quested L-erythrofuranose-derived 2-amino-2-oxazolines
37-39. Partial deacetylation was observed at this step
in the case of compound 39. Nevertheless, upon full
deacetylation, acid treatment, and neutralization (or base
treatment in the case of 39), the furanose intermediates
rearranged into the target 2-oxa-3-iminoindolizidines
40-42 (Scheme 6). As previously observed in the (+)-
castanospermine series, the C-6-linked methyl R-D-glu-
copyranoside derivative 42 exhibited a distinct pH-
dependent reversibility between the hemiaminal indolizi-
dine form and the hemiacetal furanose form. Neverthe-
less, once generated from the furanose precursor (pH 9),
the indolizidine species, in either neutral or charged form,
remains stable in water solution at basic or moderately
acidic pH (up to pH 4).
J . Org. Chem, Vol. 68, No. 23, 2003 8895

Garc´ıa-Moreno et al.
TABLE 1. Glycosid a se In h ibitor y Activities (Ki, µM) for In d olizid in e-Tr eh a zolin Hybr id s 21-25 a n d 40-42
enzyme
21
22
23
24
25
40
41
42
R-glucosidase (yeast)a
57
168
3.2
57
23
17
212
463
336
179
188
282
213
378
222
â-glucosidase (almonds)b
30
15c
27
1.9c
2.7
â-glucosidase (bovine liver)c
trehalase (pig kidney)e
244
244
n.i.
n.i.
n.i.
n.i.
157
n.i.
n.i.
n.i.
n.i.
n.i.
n.i.d
n.i.
n.i.
n.i.
n.i.
n.i.
1380
n.i.
n.i.
n.i.
n.i.
n.i.
565
n.i.
n.i.
n.i.
n.i.
n.i.
349
n.i.
n.i.
n.i.
n.i.
n.i.
189
n.i.
n.i.
240
n.i.
182
n.i.
n.i.
n.i.
n.i.
R-galactosidase (coffee beans)a
R-mannosidase (jack beans)b
R-fucosidase (bovine kidney)b
amyloglucosidase (Aspergillus niger)f
a
b
d
pH 6.8. pH 5.5. c pH 7.3. No inhibition detected. e pH 6.0. f pH 4.5.
mercial D-glucofuranurono-6,3-lactone in four steps as reported
by Dax et al.20 2,3,4,6-Tetra-O-acetyl-â-D-glucopyranosyl isothio-
cyanate (9) was synthesized from the corresponding per-O-
acetyl glucopyranosyl bromide by treatment with potassium
thiocyanate and tetra-n-butylammonium hydrogensulfate in
acetonitrile, following the procedure of Camarasa et al.24
Methyl 2,3,4-tri-O-acetyl-6-deoxy-6-isothiocyanato-R-D-glu-
copyranoside (10) was obtained by isothiocyanation of the
corresponding 6-amino-6-deoxysugar using thiophosgene as
reported.25 2,3,5,6-Di-O-isopropylidene-L-gulonolactone was
obtained by isopropylination of commercial L-gulonolactone.31
Reagents and solvents were commercial grade and were used
as supplied, with the following exceptions: Potassium thio-
cyanate was dried with heating under vacuum at 80 °C. DMF
was distilled from BaO, methanol was distilled from methyl-
magnesium iodide, pyridine was distilled from KOH, and acetic
anhydride was distilled from freshly melted sodium acetate.
with the binding site of the enzyme. We had previously
observed that replacing the 1-hydroxyindolizidine struc-
ture into a 2-oxaindolizidine skeleton, which is formally
equivalent to a rotation of 120° about the above bond,
results in a shift of the R-glucosidase selectivity.14 Thus,
1 and 2 do not inhibit yeast R-glucosidase and are good
inhibitors of amyloglucosidase (Ki ) 8 µM for 1, IC50
)
7.4 µM for 2),9 while 2-oxacastanospermine analogues
exhibited the reverse selectivity.14 Similar trends are
observed for the new castanospermine-trehazolin hy-
brids when considering this pair of enzymes.
The competitive inhibition of â-glucosidases by com-
pounds 21-23, bearing lipophilic substituents, is note-
worthy. These results underline the importance of sec-
ondary interactions in glycosidase binding, even over-
powering other effects related to the glyconic binding site.
Moreover, the increase in the inhibition potency toward
â-glucosidase upon shifting from pH 5.5 to pH 7.3 points
to the neutral iminoindolizidine form (see, e.g., 25a ) as
the active species, which is probably protonated from one
of the catalytic carboxylic groups of the enzyme to form
a tight complex. A similar observation has been reported
for the inhibition of green coffee bean R-galactosidase by
cyclic guanidine glycomimetics.28
3-O-Acetyl-5-a zid o-5-d eoxy-1,2-O-isop r op ylid en e-6-O-
tr im eth ylsilyl-r-D-glu cofu r an ose (8). To a solution of 5-azido-
5-deoxy-1,2-O-isopropylidene-6-O-tetrahydropyranyl-R-D-glu-
cofuranose20 7 (1.71 g, 5.2 mmol) in pyridine (8.5 mL) at rt,
Ac2O (8.5 mL) was added and the reaction mixture was stirred
for 2 h. After conventional workup, the crude acetate product
was dissolved in CH2Cl2-MeOH (1:1, 60 mL) and p-toluene-
sulfonic acid (168 mg) was added. The reaction mixture was
stirred at rt for 2 h, and then diluted with CH2Cl2 (60 mL),
washed with saturated aqueous NaHCO3 (2 × 100 mL), dried
(MgSO4), filtered, and concentrated. The resulting residue was
purified by column chromatography using 1:6 f 1:1 EtOAc-
petroleum ether as eluent. Trimethylsilylation of the generated
primary hydroxyl group was effected by treatment with
trimethylsilyl chloride (5.3 mL) and hexamethyldisilazane
(10.6 mL) in pyridine (22 mL) at rt for 2 h. The solvents were
eliminated, and the residue was extracted with petroleum
ether and concentrated to give 3 (1.17 g, 63% overall) as an
amorphous solid. [R]D -35.3 (c 1.1, CH2Cl2). Rf 0.38 (1:6
EtOAc-petroleum ether). IR (KBr): νmax 2988, 2101, 1751,
Con clu sion s
We have described here an effective synthetic route to
a new family of sp2-azasugar glycomimetics that combine
the essential structural features of indolizidines and
trehazolins. Starting from D-glucose and L-gulose precur-
sors, reducing analogues of (+)-castanospermine and its
6-epi diastereoisomer, respectively, were prepared by a
reaction sequence that involves (i) tandem Staudiger-
aza-Wittig-type coupling reaction of an azido sugar with
an isothiocyanate, (ii) transformation of the resulting
carbodiimide adduct into a 2-amino-1,3-oxazoline pseudo-
C-nucleoside derivative, and (iii) rearrangement of the
furanose intermediate through the open chain aldehydo
form to give the bicyclic 3-imino-2-oxaindolizidine skel-
eton. The glycosidase inhibition studies evidenced a
remarkable influence of the nature of the exocyclic
substituent in the inhibitory properties, as well as a pH
dependence of the inhibition constant. Although the
inhibition potency described in this study is moderate (Ki
values in the micromolar range), the prepared indolizi-
dine-trehazolin hybrids provide a new direction to the
synthesis of highly specific inhibitors and new insights
into the mechanism of inhibition of glycosidases.
1651, 1454, 1377, 1258, 1094 cm-1 1H NMR (500 MHz,
.
CDCl3): δ 5.88 (d, 1 H, J ) 3.7 Hz), 5.25 (d, 1 H, J ) 3.0 Hz),
4.50 (d, 1 H, J ) 3.7 Hz), 4.13 (dd, 1 H, J ) 3.0, 9.8 Hz), 4.02
(dd, 1 H, J ) 2.7, 10.8 Hz), 3.73 (dd, 1 H, J ) 7.2, 10.8 Hz),
3.63 (ddd, 1 H, J ) 2.7, 7.2, 9.8 Hz), 2.12 (s, 3 H), 1.49, 1.30 (2
s, 6 H), 0.14 (s, 9 H). 13C NMR (125.7 MHz, CDCl3): δ 169.4,
112.3, 104.9, 82.9, 76.8, 76.1, 63.6, 60.7, 26.5, 26.1, 20.7, -0.80.
FABMS: m/z 360 (30, [M + H]+). Anal. Calcd for C14H25N3O6-
Si: C, 76.78; H, 7.01; N, 11.69. Found: C, 76.68; H, 6.99; N,
11.66.
Gen er a l P r oced u r e for th e P r ep a r a tion of 5-Ca r bod i-
im id o-5-d eoxy-D-glu cofu r a n oses (11-15). To a solution of
azide 8 (500 mg, 1.39 mmol) and the corresponding isothio-
cyanate (n-butyl, n-octyl, phenyl, 9, or 10) in toluene (8 mL)
under Ar, a solution of triphenylphosphine (400 mg, 1.53 mmol,
1.1 equiv) in toluene (4 mL) was dropwise added at rt. The
reaction mixture was stirred at rt (13 and 14) or at 80 °C (11,
12, and 15) for 2.5-24 h (TLC) and concentrated. The resulting
residue was purified by column chromatography using the
solvent indicated in each case to afford the carbodiimide
adducts as amorphous solids.
Exp er im en ta l Section
Ma ter ia ls. 5-Azido-5-deoxy-1,2-O-isopropylidene-6-O-tet-
rahydropyranyl-R-D-glucofuranose (7) was prepared from com-
8896 J . Org. Chem., Vol. 68, No. 23, 2003

Isourea-Type Glycomimetics
3-O-Acetyl-5-(3-bu tylca r bod iim id o)-5-d eoxy-1,2-O-iso-
p r op ylid en e-6-O-tr im eth ylsilyl-r-D-glu cofu r a n ose (11).
Column chromatography, eluent toluene and then 1:10 f 1:8
EtOAc-toluene; yield 298 mg (52%). [R]D -34.0 (c 1.0, CH2-
Cl2). Rf 0.45 (1:7 EtOAc-toluene). IR (KBr): νmax 2957, 2131,
Column chromatography, eluent toluene and then 1:5 f 1:3
EtOAc-petroleum ether; yield 404 mg (44%). [R]D +55.8 (c 0.8,
CH2Cl2). Rf 0.25 (1:2 EtOAc-petroleum ether). IR (KBr): νmax
1
2953, 2876, 2137, 1751, 1373, 1225, 1045 cm-1. H NMR (500
MHz, CDCl3): δ 5.76 (d, 1 H, J ) 3.7 Hz), 5.34 (dd, 1 H, J )
9.4, 10.0 Hz), 5.16 (d, 1 H, J ) 2.8 Hz), 4.86 (t, 1 H, J ) 9.4
Hz), 4.85 (d, 1 H, J ) 3.6 Hz), 4.76 (dd, 1 H, J ) 3.6 Hz), 4.38
(d, 1 H, J ) 3.7 Hz), 4.05 (dd, 1 H, J ) 2.8, 9.6 Hz), 3.79 (dd,
1 H, J ) 2.5, 10.1 Hz), 3.74 (dt, 1 H, J ) 4.8, 9.4 Hz), 3.55 (dd,
1 H, J ) 4.8, 10.0 Hz), 3.51 (dd, 1 H, J ) 4.8, 10.0 Hz), 3.50
(m, 2 H), 3.30 (s, 3 H), 2.02, 1.96, 1.92, 1.90 (4 s, 12 H), 1.40,
1.20 (2 s, 6 H), 0.05 (s, 9 H). 13C NMR (125.7 MHz, CDCl3): δ
169.8, 169.7, 169.4, 169.3, 139.9, 112.1, 104.9, 96.4, 82.8, 77.8,
75.9, 70.7, 70.0, 69.8, 68.2, 63.4, 56.8, 55.4, 46.9, 26.5, 26.1,
20.8, 20.6, 20.4, 20.3, -0.67. CIMS: m/z 661 (100, [M + H]+).
HRCIMS: m/z 661.264475 (calcd 661.264008). Anal. Calcd for
1
1751, 1375, 1223, 1101 cm-1. H NMR (500 MHz, CDCl3): δ
5.85 (d, 1 H, J ) 3.7 Hz), 5.25 (d, 1 H, J ) 3.0 Hz), 4.47 (d, 1
H, J ) 3.7 Hz), 4.13 (dd, 1 H, J ) 3.0, 9.7 Hz), 3.91 (dd, 1 H,
J ) 2.6, 10.3 Hz), 3.63 (dd, 1 H, J ) 6.8, 10.3 Hz), 3.56 (ddd,
1 H, J ) 2.6, 6.8, 9.7 Hz), 3.19 (t, 2 H, J ) 7.0 Hz), 2.09 (s, 3
H), 1.52 (m, 2 H), 1.48, 1.29 (2 s, 6 H), 1.36 (m, 2 H), 0.90 (t,
3 H, J ) 7.0 Hz), 0.14-0.12 (s, 9 H). 13C NMR (125.7 MHz,
CDCl3): δ 169.6, 139.9, 112.1, 105.0, 82.9, 78.1, 76.2, 63.7, 57.0,
46.2, 33.0, 26.6, 26.2, 20.8, 19.9, 13.5, -0.60. FABMS: m/z 415
(100, [M + H]+). Anal. Calcd for C19H34N2O6Si: C, 55.04; H,
8.26; N, 6.75. Found: C, 54.87; H, 8.21; N, 6.95.
C
28H44N2O14Si: C, 50.89; H, 6.71; N, 4.24. Found: C, 50.85;
3-O-Acetyl-5-d eoxy-1,2-O-isop r op ylid en e-5-(3-octylca r -
bodiim ido)-6-O-tr im eth ylsilyl-r-D-glu cofu r an ose (12). Col-
umn chromatography, eluent toluene and then 1:10 EtOAc-
toluene; yield 293 mg (45%). [R]D -24.0 (c 1.0, CH2Cl2). Rf 0.57
(1:7 EtOAc-toluene). IR (KBr): νmax 2930, 2131, 1759, 1381,
H, 6.64; N, 4.20.
Gen er a l P r oced u r e for th e P r ep a r a tion of 4-(L-Th r eo-
fu r a n os-4′-yl)-2-a m in o-2-oxa zolin es (16-20). To a solution
of the corresponding carbodiimide 11-15 (0.5 mmol) in THF
(10 mL) at 0 °C under Ar, TBAF (1 M in THF, 0.55 mL, 1.1
equiv) was added. In the case of 14, the reaction mixture was
adjusted at pH 7 using glacial AcOH. The solution was stirred
at 0 °C until the dissappearance of the starting material (25
min), then diluted with Et2O (5 mL), washed with water (2 ×
3 mL), dried (MgSO4), filtered, and concentrated. The residue
was purified by column chromatography using the eluent
indicated in each case.
1
1223, 1101 cm-1. H NMR (500 MHz, CDCl3): δ 5.87 (d, 1 H,
J ) 3.7 Hz), 5.27 (d, 1 H, J ) 3.0 Hz), 4.48 (d, 1 H, J ) 3.7
Hz), 4.14 (dd, 1 H, J ) 3.0, 9.5 Hz), 3.92 (dd, 1 H, J ) 2.4, 9.9
Hz), 3.64 (dd, 1 H, J ) 6.8, 9.9 Hz), 3.57 (ddd, 1 H, J ) 2.4,
6.8, 9.5 Hz), 3.19 (t, 2 H, J ) 7.0 Hz), 2.10 (s, 3 H), 1.56 (q, 2
H, J ) 7.0 Hz), 1.49, 1.29 (2 s, 6 H), 1.26 (m, 10 H), 0.87 (t, 3
H, J ) 7.0 Hz), 0.14-0.12 (s, 9 H). 13C NMR (125.7 MHz,
CDCl3): δ 169.5, 139.9, 112.0, 104.9, 82.8, 78.0, 76.1, 63.7, 56.9,
46.5, 31.6, 30.9, 26.7, 26.1, 29.0, 26.5, 22.5, 20.7, 13.9, -0.60.
FABMS: m/z 493 (70, [M + Na]+), 471 (100, [M + H]+). Anal.
Calcd for C23H42N2O6Si: C, 58.69; H, 8.99; N, 5.95. Found: C,
58.45; H, 8.93; N, 5.84.
(4R)-4-[(4′R)-3′-O-Acetyl-1′,2′-O-isopr opyliden e-â-L-th r e-
ofu r an os-4′-yl]-2-bu tylam in o-2-oxazolin e (16). Column chro-
matography, eluent EtOAc and then 45:5:3 EtOAc-EtOH-
H2O; yield 159 mg (95%). [R]D -24.4 (c 0.98, CH2Cl2). Rf 0.30
(45:5:3 EtOAc-EtOH-H2O). IR (KBr): νmax 3389, 2959, 1748,
3-O-Acetyl-5-d eoxy-1,2-O-isop r op ylid en e-5-(3-p h en yl-
ca r bod iim id o)-6-O-tr im eth ylsilyl-r-D-glu cofu r a n ose (13).
Column chromatography, eluent toluene and then 1:7 EtOAc-
toluene; yield 452 mg (75%). [R]D -38.2 (c 1.0, CH2Cl2). Rf 0.56
(1:7 EtOAc-toluene). IR (KBr): νmax 2999, 2959, 2133, 1752,
1543, 1456, 1375, 1225, 1074 cm-1 1H NMR (500 MHz,
.
CDCl3): δ 5.87 (d, 1 H, J ) 3.7 Hz), 5.18 (d, 1 H, J ) 2.6 Hz),
4.51 (d, 1 H, J ) 3.7 Hz), 4.50 (dd, 1 H, J ) 5.5, 8.4 Hz), 4.42
(t, 1 H, J ) 8.4 Hz), 4.26 (ddd, 1 H, J ) 5.5, 7.4, 8.4 Hz), 4.25
(dd, 1 H, J ) 2.6, 7.4 Hz), 3.19 (td, 3 H, J ) 3.0, 7.1 Hz), 2.10
(s, 3 H), 1.50 (q, 2 H, J ) 7.0 Hz), 1.49, 1.28 (2 s, 6 H), 1.33
(m, 2 H, J ) 7.0 Hz), 0.90 (t, 3 H). 13C NMR (125.7 MHz,
CDCl3): δ 169.7, 162.1, 112.4, 104.9, 83.3, 80.8, 73.5, 71.6, 59.7,
42.6, 31.7, 26.7, 26.2, 21.0, 19.8, 13.6. FABMS: m/z 343 (100,
[M + H]+). Anal. Calcd for C16H26N2O6: C, 56.13; H, 7.65; N,
8.18. Found: C, 55.96; H, 7.47; N, 8.06.
1379, 1228, 1100, 1021, 846 cm-1 1H NMR (300 MHz,
.
CDCl3): δ 7.27-7.09 (m, 5 H), 5.89 (d, 1 H, J ) 3.7 Hz), 5.32
(d, 1 H, J ) 3.0 Hz), 4.51 (d, 1 H, J ) 3.7 Hz), 4.25 (dd, 1 H,
J ) 3.0, 9.4 Hz), 3.99 (dd, 1 H, J ) 2.1, 9.9 Hz), 3.82 (ddd, 1
H, J ) 2.1, 6.8, 9.4 Hz), 3.74 (dd, 1 H, J ) 6.8, 9.9 Hz), 2.09 (s,
3 H), 1.51, 1.31 (2 s, 6 H), 0.06 (s, 9 H). 13C NMR (75.5 MHz,
CDCl3): δ 169.5, 139.6, 138.2-123.8, 112.2, 105.0, 82.8, 77.7,
76.1, 63.4, 57.7, 26.5, 26.1, 20.7, -0.87. FABMS: m/z 435 (100,
[M + H]+). Anal. Calcd for C21H30N2O6Si: C, 58.04; H, 6.96;
N, 6.45. Found: C, 57.85; H, 6.85; N, 6.44.
3-O-Acetyl-5-d eoxy-1,2-O-isop r op ylid en e-5-[3-(2,3,4,6-
tetr a -O-a cetyl-â-D-glu cop yr a n osyl)ca r bod iim id o]-6-O-tr i-
m eth ylsilyl-r-D-glu cofu r a n ose (14). Column chromatogra-
phy, eluent toluene and then 1:4 f 1:2 EtOAc-petroleum
ether; yield 669 mg (70%). [R]D -24.1 (c 1.0, CH2Cl2). Rf 0.28
(1:3 EtOAc-petroleum ether, two elutions). IR (KBr): νmax
2986, 2955, 2143, 1751, 1454, 1373, 1227, 1094 cm-1. 1H NMR
(300 MHz, CDCl3): δ 5.83 (d, 1 H, J ) 3.7 Hz), 5.25 (d, 1 H, J
) 3.0 Hz), 5.15 (t, 1 H, J ) 9.5 Hz), 5.06 (t, 1 H, J ) 9.5 Hz),
4.87 (t, 1 H, J ) 9.5 Hz), 4.68 (d, 1 H, J ) 9.5 Hz), 4.44 (d, 1
H, J ) 3.7 Hz), 4.22 (dd, 1 H, J ) 4.8, 12.4 Hz), 4.16 (dd, 1 H,
J ) 3.0, 9.5 Hz), 4.10 (dd, 1 H, J ) 2.5, 12.4 Hz), 3.88 (dd, 1
H, J ) 2.1, 9.8 Hz), 3.73 (ddd, 1 H, J ) 2.5, 4.8, 9.5 Hz), 3.66
(dd, 1 H, J ) 6.1, 9.8 Hz), 3.63 (ddd, 1 H, J ) 2.1, 6.1, 9.5 Hz),
2.08, 2.07, 2.04, 2.01, 2.00 (5 s, 15 H), 1.47, 1.26 (2 s, 6 H),
0.12 (s, 9 H). 13C NMR (75.5 MHz, CDCl3): δ 170.5, 170.1,
169.7, 169.1, 168.9, 138.2, 112.2, 104.9, 84.7, 82.7, 77.5, 75.8,
73.7, 72.9, 72.4, 67.9, 63.0, 61.7, 56.9, 26.4, 26.0, 21.1, 20.8,
20.5, 20.4, 20.3, -0.80. CIMS: m/z 689 (95%, [M + H]+). Anal.
Calcd for C29H44N2O15Si: C, 50.57; H, 6.44; N, 4.07. Found:
C, 50.30; H, 6.33; N, 3.85.
(4R)-4-[(4′R)-3′-O-Acetyl-1′,2′-O-isopr opyliden e-â-L-th r e-
ofu r an os-4′-yl]-2-octylam in o-2-oxazolin e (17). Column chro-
matography, eluent EtOAc and then 45:5:3 EtOAc-EtOH-
H2O; yield 139 mg (70%). [R]D -33.3 (c 1.0, CH2Cl2). Rf 0.36
(45:5:3 EtOAc-EtOH-H2O). IR (KBr): νmax 3350, 2930, 1757,
1589, 1375, 1223, 1101 cm-1. H NMR (500 MHz, CDCl3): δ
1
5.86 (d, 1 H, J ) 3.7 Hz), 5.07 (d, 1 H, J ) 3.0 Hz), 4.59 (dd,
1 H, J ) 5.0, 8.8 Hz), 4.53 (t, 1 H, J ) 7.0 Hz), 4.52 (d, 1 H, J
) 3.7 Hz), 4.28 (dt, 1 H, J ) 5.0, 7.0 Hz), 4.25 (dd, 1 H, J )
3.4, 7.0 Hz), 3.15 (td, 2 H, J ) 1.4, 7.0 Hz), 2.10 (s, 3 H), 1.53
(q, 2 H, J ) 7.0 Hz), 1.49, 1.28 (2 s, 6 H), 1.24 (m, 2 H), 0.87
(t, 3 H, J ) 7.0 Hz). 13C NMR (75.5 MHz, CDCl3): δ 169.6,
162.7, 112.3, 104.9, 83.1, 79.9, 76.4, 71.8, 55.8, 42.1, 31.6, 29.5,
26.5, 25.9, 22.4, 20.8, 13.9. FABMS: m/z 421 (30, [M + Na]+),
399 (100, [M + H]+). Anal. Calcd for C22H38N2O8: C, 60.28; H,
8.60; N, 7.03. Found: C, 60.17; H, 8.32; N, 6.93.
(4R)-4-[(4′R)-3′-O-Acetyl-1′,2′-O-isopr opyliden e-â-L-th r e-
ofu r a n os-4′-yl]-2-p h en yla m in o-2-oxa zolin e (18). Column
chromatography, eluent 100:1 CH2Cl2-MeOH; yield 136 mg
(75%). [R]D -6.5 (c 1.0, CH2Cl2). Rf 0.30 (20:1 CH2Cl2-MeOH).
IR (KBr): νmax 3349, 2991, 1752, 1553, 1379, 1236, 1077 cm-1
.
1H NMR (300 MHz, CDCl3): δ 7.36-7.25 (m, 5 H), 7.00 (m, 1
H), 5.91 (d, 1 H, J ) 3.7 Hz), 5.34 (d, 1 H, J ) 2.9 Hz), 4.53 (d,
1 H, J ) 3.7 Hz), 4.40 (m, 2 H), 4.31 (m, 1 H), 4.23 (dd, 1 H,
J ) 2.9, 7.6 Hz), 2.11 (s, 3 H), 1.51, 1.31 (2 s, 6 H). 13C NMR
(75.5 MHz, CDCl3): δ 169.7, 157.3, 129.1-118.5, 112.1, 104.8,
83.2, 81.4, 76.1, 69.6, 56.0, 26.5, 26.0, 20.8; FABMS: m/z 363
3-O-Acet yl-5-d eoxy-1,2-O-isop r op ylid en e-5-[3-(m et h -
yl 2,3,4-t r i-O-a cet yl-6-d eoxy-r-D-glu cop yr a n osyd -6-yl)-
ca r bod iim id o]-6-O-tr im eth ylsilyl-r-D-glu cofu r a n ose (15).
J . Org. Chem, Vol. 68, No. 23, 2003 8897

Garc´ıa-Moreno et al.
(100%, [M + H]+). Anal. Calcd for C18H22N2O6: C, 59.66; H,
6.12; N, 7.73. Found: C, 59.69; H, 6.07; N, 7.75.
Calcd for C11H20N2O5: C, 50.78; H, 7.69; N, 10.77. Found: C,
50.73; H, 7.80; N, 10.60.
(5R,6S,7R,8R,8a R)-5,6,7,8-Tetr a h yd r oxy-3-octylim in o-
2-oxa in d olizid in e (22). Column chromatography, eluent 15:1
MeCN-H2O; yield 122 mg (90%). [R]D -5.0 (c 1.0, H2O). Rf
0.39 (10:1:1 MeCN-H2O-NH4OH). 1H NMR (500 MHz,
D2O): δ 5.74 (d, 1 H, J ) 3.8 Hz), 5.22 (t, 1 H, J ) 8.9 Hz),
4.90 (t, 1 H, J ) 8.9 Hz), 4.45 (dt, 1 H, J ) 8.8, 9.5 Hz), 3.95
(t, 1 H, J ) 9.5 Hz), 3.83 (dd, 1 H, J ) 3.8, 9.5 Hz), 3.80 (t, 1
H, J ) 9.5 Hz), 3.57 (td, 2 H, J ) 4.2, 7.1 Hz), 1.53 (m, 2 H),
1.24 (m, 10 H), 0.87 (t, 3 H, J ) 7.1 Hz). 13C NMR (75.5 MHz,
D2O): δ 158.7, 74.9, 73.9, 73.0, 71.9, 70.9, 56.2, 43.2, 31.2, 28.4,
28.2, 25.8, 28.3, 22.1, 13.5. FABMS: m/z 317 (100, [M + H]+).
Anal. Calcd for C15H28N2O5: C, 56.94; H, 8.92; N, 8.85.
Found: C, 56.67; H, 8.88; N, 8.74.
(5R,6S,7R,8R,8a R)-5,6,7,8-Tet r a h yd r oxy-2-oxa -3-p h e-
n ylim in oin d olizid in e (23). Column chromatography, eluent
20:1 CH2Cl2-MeOH; yield 76 mg (63%). [R]D -26.7 (c 0.75,
pyridine). Rf 0.15 (9:1 CH2Cl2-MeOH). 1H NMR (500 MHz,
D2O): δ 7.44-7.27 (m, 5 H), 5.73 (bs, 1 H), 4.96 (t, 1 H, J )
8.8 Hz), 4.69 (t, 1 H, J ) 8.8 Hz), 4.28 (dt, 1 H, J ) 8.8, 9.4
Hz), 3.81 (t, 1 H, J ) 9.4 Hz), 3.73 (dd, 1 H, J ) 3.7, 9.4 Hz),
3.66 (t, 1 H, J ) 9.4 Hz). 13C NMR (75.5 MHz, D2O): δ 157.4,
129.7-123.9, 75.3, 74.1, 73.0, 71.9, 70.9, 56.1. FABMS: m/z
281 (100, [M + H]+). Anal. Calcd for C13H16N2O5: C, 55.71; H,
5.75; N, 9.99. Found: C, 55.70; H, 5.81; N, 9.97.
(4R)-4-[(4′R)-3′-O-Acetyl-1′,2′-O-isopr opyliden e-â-L-th r e-
ofu r a n os-4′-yl]-2-(2,3,4,6-tetr a -O-a cetyl-â-D-glu cop yr a n o-
syl)a m in o-2-oxa zolin iu m Aceta te (19). Column chroma-
tography, eluent 100:1 f 20:1 CH2Cl2-MeOH; yield 310 mg
(92%). [R]D -20.0 (c 1.0, CH2Cl2). Rf 0.53 (20:1 CH2Cl2-MeOH).
IR (KBr): νmax 3443, 2961, 1750, 1559, 1514, 1377, 1258, 1094
cm-1. 1H NMR (300 MHz, CDCl3): δ 5.86 (d, 1 H, J ) 3.7 Hz),
5.65 (bs, 1 H, NH), 5.22 (t, 1 H, J ) 9.3 Hz), 5.13 (d, 1 H, J )
3.0 Hz), 5.06 (t, 1 H, J ) 9.3 Hz), 4.98 (t, 1 H, J ) 9.3 Hz),
4.89 (d, 1 H, J ) 9.3 Hz), 4.51 (d, 1 H, J ) 3.7 Hz), 4.45 (m, 2
H), 4.26 (m, 1 H), 4.25 (dd, 1 H, J ) 4.8, 12.4 Hz), 4.17 (dd, 1
H, J ) 3.0, 7.8 Hz), 4.10 (dd, 1 H, J ) 2.2, 12.4 Hz), 3.77 (ddd,
1 H, J ) 2.2, 4.8, 9.3 Hz), 2.09, 2.05, 2.01, 2.00, 1.99, 1.92 (6
s, 18 H), 1.50, 1.29 (2 s, 6 H). 13C NMR (75.5 MHz, CDCl3): δ
178.0, 170.6, 169.9, 169.6, 169.3, 168.9, 161.2, 112.1, 104.7,
83.1, 82.2, 80.7, 76.2, 73.1, 72.8, 71.5, 70.4, 68.0, 61.6, 59.9,
26.5, 25.9, 22.8, 21.1, 20.8, 20.6, 20.5, 20.4. FABMS: m/z 639
(100, [M - AcOH + Na]+), 617 (50%, [M - AcO-]+). Anal. Calcd
for C28H40N2O17: C, 49.70; H, 5.96; N, 4.14. Found: C, 49.83;
H, 5.90; N, 3.92.
(4R)-4-[(4′R)-3′-O-Acetyl-1′,2′-O-isopr opyliden e-â-L-th r e-
ofu r a n os-4′-yl]-2-(m eth yl 2,3,4-tr i-O-a cetyl-r-D-glu cop y-
r a n osyd -6-yl)a m in o-2-oxa zolin e (20). Column chromatog-
raphy, eluent 100:1 f 20:1 CH2Cl2-MeOH; yield 191 mg
(65%). [R]D +38.5 (c 1.0, CH2Cl2). Rf 0.43 (45:5:3 EtOAc-
EtOH-H2O). IR (KBr): νmax 3443, 2984, 1751, 1565, 1373,
(5R,6S,7R,8R,8a R)- 3-â-D-Glu cop yr a n osylim in o-5,6,7,8-
tetr a h yd r oxy-2-oxa in d olizid in e (24). Column chromatog-
raphy, eluent 4:1 MeCN-H2O; yield 135 mg (86%). [R]D +5.9
(c 1.0, H2O). Rf 0.26 (6:3:1 MeCN-H2O-NH4OH). 1H NMR
(500 MHz, D2O): δ 5.34 (d, 1 H, J ) 4.0 Hz), 4.65 (d, 1 H, J )
8.7 Hz), 4.52 (t, 1 H, J ) 8.0 Hz), 4.18 (t, 1 H, J ) 8.0 Hz),
3.99 (dt, 1 H, J ) 8.0, 9.5 Hz), 3.73 (dd, 1 H, J ) 4.7, 12.2 Hz),
3.61 (dd, 1 H, J ) 1.7, 12.2 Hz), 3.60 (t, 1 H, J ) 9.5 Hz), 3.51
(dd, 1 H, J ) 4.0, 9.5 Hz), 3.39 (t, 1 H, J ) 9.5 Hz), 3.55 (m, 2
H), 3.38 (t, 1 H, J ) 8.7 Hz), 3.09 (t, 1 H, J ) 8.7 Hz). 13C
NMR (125.7 MHz, D2O): δ 156.9, 86.6, 77.4, 76.3, 74.6, 74.5,
73.1, 72.6, 71.1, 69.9, 69.6, 60.7, 54.4. FABMS: m/z 389 (25,
1
1225, 1101 cm-1. H NMR (500 MHz, CDCl3): δ 5.82 (d, 1 H,
J ) 3.7 Hz), 5.40 (dd, 1 H, J ) 9.5, 10.1 Hz), 5.15 (d, 1 H, J )
2.9 Hz), 4.87 (d, 1 H, J ) 3.6 Hz), 4.80 (dd, 1 H, J ) 3.6 Hz),
4.44 (d, 1 H, J ) 3.7 Hz), 4.40 (t, 1 H, J ) 9.5 Hz), 4.29 (m, 3
H), 4.09 (dd, 1 H, J ) 2.9, 7.9 Hz), 3.82 (ddd, 1 H, J ) 2.9, 5.4,
9.5 Hz), 3.36 (dd, 1 H, J ) 2.9, 11.9 Hz), 3.30 (dd, 1 H, J )
5.4, 11.9 Hz), 3.34 (s, 3 H), 2.10, 2.02, 2.01, 1.99 (4 s, 12 H),
1.48, 1.26 (2 s, 6 H). 13C NMR (125.7 MHz, CDCl3): δ 170.1,
169.9, 169.8, 168.7, 161.8, 112.1, 104.8, 96.6, 83.3, 81.4, 76.2,
70.8, 69.9, 69.1, 67.6, 61.5, 55.3, 42.7, 26.5, 26.1, 20.9, 20.8,
20.6, 20.5. FABMS: m/z 589 (100, [M + H]+). Anal. Calcd for
[M + Na]+), 367 (10, [M + H]+). Anal. Calcd for C13H22N2O10
:
C
25H36N2O14: C, 51.02; H, 6.16; N, 4.76. Found: C, 50.97; H,
C, 42.62; H, 6.05; N, 7.65. Found: C, 42.75; H, 6.13; N, 7.69.
5.98; N, 4.80.
(5R,6S,7R,8R,8a R)-5,6,7,8-Tetr a h yd r oxy-3-(m eth yl r-D-
glu cop yr a n osyd -6-yl)im in o-2-oxa -in d olizid in e (25). Col-
umn chromatography, eluent 7:1 MeCN-H2O; yield 55 mg
(83%). [R]D +99.0 (c 1.0, H2O). Rf 0.71 (6:3:1 MeCN-H2O-
Gen er a l P r oced u r e for th e P r ep a r a tion of Isou r ea -
Typ e (+)-Ca sta n osp er m in e An a logu es (21-25). To a solu-
tion of the corresponding 2-amino-2-oxazoline precursor 16-
20 (0.43 mmol) in dry MeOH (4 mL), methanolic NaMeO (1
M, 0.1 equiv per mol of acetate) was added. The reaction
mixture was stirred at rt for 30 min, then neutralized with
solid CO2, and concentrated. The residue was treated with
TFA-H2O (9:1, 2 mL) for 15 min, concentrated under reduced
pressure, coevaporated several times with water, neutralized
with Amberlite IRA-68 (OH-) ion-exchange resin, and sub-
jected to column chromatography with the eluent indicated
in each case. The bicyclic 2-iminoindolizidine derivatives 21-
24 were thus obtained from 16-19 as white lyophilyzates.
However, the methyl R-D-glucopyranosid-6-ylimino derivative
25 was shown to exist under such conditions as an anomeric
mixture of the furanose form 25a (NMR). Shifts at pH 9 (0.1
M NaOH) and further neutralization (0.1 M HCl) provided the
indolizidine tautomer 25b as the only detectable form (NMR).
In all cases, the fully deprotected compounds were further
purified by GPC (Sephadex G-10, 1:1 MeOH-H2O).
(5R,6S,7R,8R,8a R)-3-Bu tylim in o-5,6,7,8-tetr a h yd r oxy-
2-oxa in d olizid in e (21). Column chromatography, eluent 15:1
MeCN-H2O; yield 101 mg (90%). [R]D -2.0 (c 1.0, H2O). Rf
0.38 (10:1:1 MeCN-H2O-NH4OH). 1H NMR (300 MHz,
D2O): δ 5.53 (d, 1 H, J ) 3.9 Hz), 5.01 (t, 1 H, J ) 8.8 Hz),
4.67 (t, 1 H, J ) 8.8 Hz), 4.24 (dt, 1 H, J ) 8.8, 9.4 Hz), 3.74
(t, 1 H, J ) 9.4 Hz), 3.62 (dd, 1 H, J ) 3.9, 9.4 Hz), 3.61 (t, 1
H, J ) 9.4 Hz), 3.36 (td, 2 H, J ) 2.1, 7.1 Hz), 1.55 (q, 2 H, J
) 7.1 Hz), 1.30 (m, 2 H), 0.87 (t, 3 H, J ) 7.1 Hz). 13C NMR
(75.5 MHz, D2O): δ 158.7, 74.9, 73.9, 73.0, 71.9, 70.9, 56.2,
42.9, 30.4, 19.2, 12.9. FABMS: m/z 261 (100, [M + H]+). Anal.
1
NH4OH). H NMR (500 MHz, D2O): δ 5.58 (bs, 1 H), 4.78 (d,
1 H, J ) 3.8 Hz), 4.70 (m, 1 H), 4.67 (t, 1 H, J ) 9.5 Hz), 4.48
(d, 1 H, J ) 9.5 Hz), 4.21 (m, 1 H), 3.98 (t, 1 H, J ) 7.8 Hz),
3.82 (d, 1 H, J ) 9.5 Hz), 3.63 (t, 1 H, J ) 9.5 Hz), 3.57 (dd, 1
H, J ) 3.0, 13.8 Hz), 3.56 (dd, 1 H, J ) 3.8, 9.5 Hz), 3.52 (m,
1 H), 3.37 (s, 3 H), 3.29 (dd, 1 H, J ) 7.0, 13.8 Hz), 3.28 (t, 1
H, J ) 9.5 Hz). 13C NMR (125.7 MHz, D2O): δ 161.4, 100.5,
74.3, 72.6, 72.4, 71.8, 56.2, 53.8, 42.0. FABMS: m/z 403 (100,
[M + Na]+). Anal. Calcd for C14H24N2O10: C, 44.21; H, 6.36;
N, 7.36. Found: C, 44.29; H, 6.32; N, 7.29.
2,3,5,6-Di-O-isop r op ylid en e-â-L-gu lofu r a n ose (27). To a
solution of 2,3,5,6-di-O-isopropylidene-L-gulonolactone31 (26)
(2 g, 7.74 mmol) in toluene (70 mL) at -78 °C under Ar, DIBAL
(1 M in hexanes, 19 mL, 2.5 equiv) was added and the reaction
mixture was allowed to reach rt. After 2 h, the reaction was
quenched by addition of MeOH until gas evolution ceased, and
saturated aqueous sodium potassium tartrate (20 mL) was
added. The mixture was partitioned between H2O and EtOAc
(50 mL each), the aqueous phase was washed with EtOAc (3
× 20 mL), and the combined organic extracts were dried
(MgSO4) and concentrated under reduced pressure. The re-
sulting residue was purified by column chromatography using
1:3 f 1:1 EtOAc-petroleum ether as the eluent to give 27
(1.50 g, 75%) as an amorphous solid. [R]D +3.6 (c 1.0, CH2Cl2).
Rf 0.43 (1:1 EtOAc-toluene). IR (KBr): νmax 3459, 2986, 1454,
1379, 1260, 1092 cm-1. 1H NMR (300 MHz, CDCl3): δ 5.44 (s,
1 H), 4.68 (dd, 1 H, J ) 3.8, 5.9 Hz), 4.60 (d, 1 H, J ) 5.9 Hz),
4.33 (dt, 1 H, J ) 6.8, 8.4 Hz), 4.19 (dd, 1 H, J ) 6.8, 8.4 Hz),
8898 J . Org. Chem., Vol. 68, No. 23, 2003

Isourea-Type Glycomimetics
4.10 (dd, 1 H, J ) 3.8, 8.4 Hz), 3.71 (dd, 1 H, J ) 6.8, 8.4 Hz),
3.60 (bs, 1 H), 1.42, 1.36, 1.27 (3 s, 12 H). 13C NMR (75.5 MHz,
CDCl3): δ 112.7, 109.7, 101.1, 85.5, 81.9, 79.7, 75.3, 65.8, 26.5,
25.8, 25.2, 24.6. FABMS: m/z 261 (40, [M + H]+). Anal. Calcd
for C12H20O6: C, 55.37; H, 7.75. Found: C, 55.31; H, 7.83.
chromatography (1:5 EtOAc-petroleum ether) to afford 31
(1.87 g, 78%) as an amorphous solid. [R]D +2.5 (c 1.0, CH2Cl2).
Rf 0.54 (1:2 EtOAc-petroleum ether). IR (KBr): νmax 2986,
1
2099, 1750, 1381, 1260, 1211, 1111 cm-1. H NMR (500 MHz,
CDCl3): δ 7.46-7.18 (m, 15 H), 6.15 (s, 1 H), 4.88 (dd, 1 H, J
) 3.5, 5.8 Hz), 4.69 (d, 1 H, J ) 5.8 Hz), 4.23 (dd, 1 H, J ) 3.5,
9.8 Hz), 3.76 (ddd, 1 H, J ) 2.8, 5.6, 9.8 Hz), 3.46 (dd, 1 H, J
) 2.8, 10.1 Hz), 3.43 (dd, 1 H, J ) 5.6, 10.1 Hz), 1.98 (s, 3 H),
1.45, 1.30 (2 s, 6 H). 13C NMR (125.7 MHz, CDCl3): δ 169.1,
143.7-126.8, 113.3, 100.4, 86.9, 84.6, 79.7, 79.4, 63.2, 59.4,
26.0, 24.9, 20.8. FABMS: m/z 552 (100, [M + Na]+). Anal. Calcd
for C30H31N3O6: C, 68.04; H, 5.90; N, 7.94. Found: C, 68.02;
H, 5.95; N, 7.82.
1-O-Acet yl-2,3,5,6-d i-O-isop r op ylid en e-â-L-gu lofu r a -
n ose (28). Conventional acetylation of 27 (2 g, 7.70 mmol) with
Ac2O-pyridine (1:1, 15 mL) yielded 28 (2.15 g, 75%). [R]D +44.0
(c 1.0, CH2Cl2). Rf 0.53 (1:3 EtOAc-petroleum ether). IR
(KBr): νmax 2988, 1746, 1454, 1377, 1213, 1094 cm-1. 1H NMR
(500 MHz, CDCl3): δ 6.93 (s, 1 H), 5.14 (dd, 1 H, J ) 4.7, 7.0
Hz), 5.09 (d, 1 H, J ) 7.0 Hz), 4.73 (td, 1 H, J ) 7.7, 9.5 Hz),
4.56 (dd, 1 H, J ) 7.7, 9.6 Hz), 4.41 (dd, 1 H, J ) 4.7, 9.5 Hz),
3.96 (t, 1 H, J ) 9.6 Hz), 2.02 (s, 3 H), 1.33, 1.32, 1.24, 1.13 (4
s, 12 H). 13C NMR (125.7 MHz, CDCl3): δ 169.3, 113.3, 109.8,
101.1, 85.1, 81.9, 79.7, 75.3, 65.2, 26.5, 25.8, 25.2, 24.6, 20.9.
FABMS: m/z 325 (30, [M + Na]+), 303 (20, [M + H]+). Anal.
Calcd for C14H22O7: C, 55.62; H, 7.34. Found: C, 55.48; H,
7.24.
1-O-Acet yl-5-a zid o-5-d eoxy-2,3-O-isop r op ylid en e-r-D-
m a n n ofu r a n ose (32). To a solution of the tritylated azido
derivative 31 (1.5 g, 2.8 mmol) in CH2Cl2 (19 mL) at 0 °C under
Ar, BF3-Et2O (391 µL) and MeOH (1 mL) were added. The
reaction mixture was allowed to reach rt and was stirred for
2 h, then washed with saturated aqueous NaHCO3 (2 × 10
mL), dried (MgSO4), and concentrated. The resulting residue
was purified by column chromatography (1:4 f 1:1 EtOAc-
petroleum ether) to give 32 (603 mg, 75%) as an amorphous
solid. [R]D +30.5 (c 0.99, CH2Cl2). Rf 0.24 (1:2 EtOAc-
petroleum ether). IR (KBr): νmax 2957, 2097, 1742, 1379, 1262,
1-O-Acetyl-2,3-O-isop r op ylid en e-â-L-gu lofu r a n ose (29).
The diacetonide derivative 28 (2.0 g, 6.62 mmol) was sus-
pended in 50% aqueous AcOH (6 mL) and heated at 40 °C for
2 h. The resulting solution was concentrated and coevaporated
several times with water and toluene, and the residue was
purified by column chromatography (2:1 EtOAc-petroleum
ether f EtOAc) to give 29 (1.40 g, 80%) as an amorphous solid.
[R]D +61.8 (c 1.0, CH2Cl2). Rf 0.34 (3:1 EtOAc-petroleum
1094 cm-1 1H NMR (500 MHz, CDCl3): δ 6.13 (d, 1 H, J )
.
1.9 Hz), 4.86 (dd, 1 H, J ) 3.6, 5.8 Hz), 4.69 (dd, 1 H, J ) 1.9,
5.8 Hz), 4.03 (dd, 1 H, J ) 3.6, 9.5 Hz), 3.85 (ddd, 1 H, J )
3.2, 5.6, 9.5 Hz), 3.94 (dd, 1 H, J ) 3.2, 11.5 Hz), 3.75 (dd, 1
H, J ) 5.6, 11.5 Hz), 2.04 (s, 3 H), 1.48, 1.35 (2 s, 6 H). 13C
NMR (125.7 MHz, CDCl3): δ 169.1, 113.4, 100.6, 84.7, 80.5,
79.4, 63.0, 61.4, 25.9, 24.8, 20.8. FABMS: m/z 310 (100, [M +
Na]+). Anal. Calcd for C11H17N3O6: C, 45.99; H, 5.96; N, 14.63.
Found: C, 45.92; H, 5.91; N, 14.43.
ether). IR (KBr): νmax 3352, 2984, 1748, 1375, 1238, 1103 cm-1
.
1H NMR (500 MHz, CDCl3): δ 6.18 (s, 1 H), 4.83 (dd, 1 H, J )
3.6, 5.9 Hz), 4.72 (d, 1 H, J ) 5.9 Hz), 4.14 (dd, 1 H, J ) 3.6
6.8 Hz), 4.10 (ddd, 1 H, J ) 3.7, 4.7, 6.8 Hz), 3.82 (dd, 1 H, J
) 3.7, 11.6 Hz), 3.75 (dd, 1 H, J ) 4.7, 11.6 Hz), 2.78, 2.08 (2
bs, 2 H), 2.06 (s, 3 H), 1.48, 1.32 (2 s, 6 H). 13C NMR (75.5
MHz, CDCl3): δ 169.4, 113.2, 100.1, 85.3, 82.1, 79.2, 70.6, 62.9,
25.8, 24.5, 20.9. FABMS: m/z 285 (100, [M + Na]+). Anal. Calcd
for C11H18O7: C, 50.38; H, 6.92. Found: C, 50.47; H, 6.84.
1-O-Acetyl-5-a zid o-5-d eoxy-2,3-O-isop r op ylid en e-6-O-
tr im eth ylsilyl-r-D-m a n n ofu r a n ose (33). To a solution of 32
(212 mg, 0.74 mmol) in pyridine (5.4 mL), a mixture of
trimethylsilyl chloride and hexamethyldisilazane (1:2, 3.76
mL) was added and the reaction mixture was stirred at rt for
2 h. The solvents were concentrated under reduced pressure,
and the resulting residue was extracted with petroleum ether,
concentrated, and purified by column chromatography (1:6
EtOAc-petroleum ether) to give 33 (213 mg, 80%) as an
amorphous solid. [R]D +29.0 (c 1.0, CH2Cl2). Rf 0.41 (1:6
EtOAc-petroleum ether). IR (KBr): νmax 2951, 2101, 1752,
1-O-Acetyl-2,3-O-isopr opyliden e-6-O-tr ityl-â-L-gu lofu r a-
n ose (30). Trityl chloride (1.9 g, 6.8 mmol, 1.5 equiv) was
added to a solution of 29 (1.25 g, 4.59 mmol) in pyridine (8
mL), and the resulting mixture was stirred at rt for 36 h. The
reaction mixture was poured into ice-water (80 mL) to give a
solid that was dissolved in toluene (40 mL), which was washed
successively with iced 10% aqueous AcOH (10 mL) and
saturated aqueous NaHCO3 (10 mL), dried (MgSO4), and
concentrated. The resulting residue was purified by column
chromatography using 1:3 EtOAc-petroleum ether as eluent
to give 30 (1.70 g, 72%) as an amorphous solid. [R]D +24.7 (c
1.0, CH2Cl2). Rf 0.58 (1:1 EtOAc-petroleum ether). IR (KBr):
1625, 1458, 1386, 1236, 1100 cm-1 1H NMR (500 MHz,
.
CDCl3): δ 6.12 (s, 1 H), 4.84 (dd, 1 H, J ) 3.6, 5.9 Hz), 4.68 (d,
1 H, J ) 5.9 Hz), 3.99 (dd, 1 H, J ) 3.6, 9.1 Hz), 3.97 (dd, 1 H,
J ) 2.2, 9.1 Hz), 3.75 (dd, 1 H, J ) 6.2, 9.1 Hz), 3.71 (ddd, 1
H, J ) 2.2, 6.2, 9.1 Hz), 2.05 (s, 3 H), 1.47, 1.35 (s, 3 H), 0.13,
0.12 (2 s, 9 H). 13C NMR (75.5 MHz, CDCl3): δ 169.1, 113.1,
100.4, 84.4, 79.4, 79.3, 63.0, 60.5, 25.9, 24.7, 20.8, -0.59.
FABMS: m/z 382 (95, [M + Na]+). Anal. Calcd for C14H25N3O6-
Si: C, 46.78; H, 7.01; N, 11.69. Found: C, 46.78; H, 6.90; N,
11.69.
Gen er a l P r oced u r e for th e P r ep a r a tion of 5-Ca r bod i-
im id o-5-d eoxy-D-m a n n ofu r a n oses (34-36). To a solution
of azide 33 (500 mg, 1.39 mmol) and the corresponding
isothiocyanate (phenyl, 9 or 10) in toluene (8 mL) under Ar, a
solution of triphenylphosphine (400 mg, 1.53 mmol, 1.1 equiv)
in toluene (4 mL) was dropwise added at rt. The reaction
mixture was stirred at rt (34 and 35) or at 40 °C (36) for 24 h
(TLC) and was concentrated. The resulting residue was
purified by column chromatography using the solvent indicated
in each case to afford the carbodiimide adducts as amorphous
solids.
1
νmax 3492, 2943, 1752, 1450, 1379, 1236, 1013 cm-1. H NMR
(300 MHz, CDCl3): δ 7.48-7.24 (m, 15 H), 6.20 (s, 1 H), 4.67
(d, 1 H, J ) 5.9 Hz), 4.61 (dd, 1 H, J ) 3.3, 5.9 Hz), 4.28 (dd,
1 H, J ) 3.3, 6.2 Hz), 4.18 (ddd, 1 H, J ) 2.3, 4.8, 5.2 Hz), 3.94
(dd, 1 H, J ) 5.2, 9.5 Hz), 3.26 (dd, 1 H, J ) 4.8, 9.5 Hz), 2.81
(d, 1 H), 2.05 (s, 3 H), 1.44, 1.25 (2 s, 6 H). 13C NMR (75.5
MHz, CDCl3): δ 169.2, 146.7-126.9, 112.9, 100.3, 86.6, 85.3,
82.0, 79.8, 69.6, 63.8, 25.8, 24.4, 20.9. FABMS: m/z 527 (50,
[M + Na]+). Anal. Calcd for C30H32O7: C, 71.41; H, 6.39.
Found: C, 71.43; H, 6.47.
1-O-Acetyl-5-a zid o-5-d eoxy-2,3-O-isop r op ylid en e-6-O-
tr ityl-r-D-m a n n ofu r a n ose (31). To a solution of 30 (2.3 g,
4.59 mmol) in CH2Cl2 (20 mL) at -25 °C under Ar, pyridine
(0.72 mL) and trifluoromethanesulfonic anhydride (1.05 mL,
6.36 mmol) were added. The reaction mixture was allowed to
reach rt, stirred for 1 h, then diluted with CH2Cl2 (15 mL),
washed with saturated aqueous NaHCO3 (15 mL), dried
(MgSO4), and concentrated. The resulting triflate ester was
dissolved in DMF (18 mL), NaN3 (3.04 g, 32.13 mmol, 7 equiv)
was added, and the reaction mixture was stirred at rt for 18
h. The solvent was removed under reduced pressure, and the
resulting residue was dissolved in CH2Cl2 (50 mL) and washed
with water. The organic phase was dried (MgSO4) and
concentrated to give a solid, which was purified by column
1-O-Acetyl-5-d eoxy-2,3-O-isop r op ylid en e-5-(3-p h en yl-
car bodiim ido)-6-O-tr im eth ylsilyl-r-D-m an n ofu r an ose (34).
Column chromatography, eluent toluene and then 1:7 EtOAc-
toluene; yield 422 mg (70%). [R]D -23.7 (c 1.0, CH2Cl2). Rf 0.37
(1:5 EtOAc-petroleum ether). IR (KBr): νmax 2959, 2133, 1752,
1
1386, 1267, 1093 cm-1. H NMR (500 MHz, CDCl3): δ 7.29-
7.09 (m, 5 H), 6.14 (d, 1 H, J ) 2.0 Hz), 4.92 (dd, 1 H, J ) 3.5,
J . Org. Chem, Vol. 68, No. 23, 2003 8899

Garc´ıa-Moreno et al.
5.9 Hz), 4.70 (dd, 1 H, J ) 2.0, 5.9 Hz), 4.14 (dd, 1 H, J ) 3.5,
9.5 Hz), 3.93 (dd, 1 H, J ) 2.3, 10.2 Hz), 3.85 (ddd, 1 H, J )
5.0, 9.5, 10.2 Hz), 3.80 (dd, 1 H, J ) 5.0, 10.2 Hz), 2.05 (s, 3
H), 1.48, 1.34 (2 s, 6 H), 0.41 (s, 9 H). 13C NMR (125.7 MHz,
CDCl3): δ 169.2, 140.0, 138.3-123.9, 113.2, 100.6, 84.6, 80.3,
79.4, 62.5, 57.6, 26.0, 24.8, 20.9, -0.80. FABMS: m/z 457 (75,
[M + Na]+). Anal. Calcd for C21H30N2O6Si: C, 58.04; H, 6.96;
N, 6.45. Found: C, 58.01; H, 6.69; N, 6.47.
7.31-7.23 (m, 5 H), 6.97 (bs, 1 H), 6.17 (s, 1 H), 4.86 (dd, 1 H,
J ) 5.9 Hz, J ) 3.7 Hz), 4.69 (d, 1 H, J ) 5.9 Hz), 4.29 (m, 3
H), 4.19 (dd, J ) 3.7, 5.6 Hz), 2.00 (s, 3 H), 1.47, 1.30 (2 s, 6
H). 13C NMR (125.7 MHz, CDCl3): δ 169.3, 128.8-119.1, 157.8,
113.0, 100.7, 84.9, 83.9, 79.4, 77.0, 69.4, 25.8, 24.4, 20.9.
FABMS: m/z 385 (95, [M + Na]+), 363 (100, [M + H]+). Anal.
Calcd for C18H22N2O6: C, 59.66; H, 6.12; N, 7.73. Found: C,
59.61; H, 6.13; N, 7.74.
1-O-Acetyl-5-d eoxy-2,3-O-isop r op ylid en e-5-[3-(2,3,4,6-
tetr a -O-a cetyl-â-D-glu cop yr a n osyl)ca r bod iim id o]-6-O-tr i-
m eth ylsilyl-r-D-m a n n ofu r a n ose (35). Column chromatog-
raphy, eluent toluene and then 1:5 f 1:2 EtOAc-petroleum
ether; yield 430 mg (45%). [R]D +3.0 (c 1.0, CH2Cl2). Rf 0.22
(1:3 EtOAc-petroleum ether, two elutions). IR (KBr): νmax
(4R)-4-[(4′R)-1′-O-Acetyl-2′,3′-O-isop r op ylid en e-L-er yth -
r ofu r a n os-4′-yl]-2-(2,3,4,6-t et r a -O-a cet yl-â-D-glu cop yr a -
n osyl)a m in o-2-oxa zolin iu m Aceta te (38). Column chroma-
tography, eluent CH2Cl2 and then 100:1 f 9:1 CH2Cl2-MeOH;
yield 305 mg (99%). [R]D +24.3 (c 1.0, CH2Cl2). Rf 0.35 (20:1
CH2Cl2-MeOH). IR (KBr): νmax 3452, 2973, 1752, 1612, 1386,
1
1
2959, 2880, 2149, 1760, 1379, 1236, 1108 cm-1. H NMR (500
1236, 1093 cm-1. H NMR (500 MHz, CDCl3): δ 6.11 (s, 1 H,
MHz, CDCl3): δ 6.08 (s, 1 H), 5.16 (t, 1 H, J ) 9.4 Hz), 5.07 (t,
1 H, J ) 9.4 Hz), 4.93 (dd, 1 H, J ) 8.7, 9.4 Hz), 4.82 (dd, 1 H,
J ) 3.5, 5.8 Hz), 4.72 (d, 1 H, J ) 8.7 Hz), 4.64 (d, 1 H, J ) 5.8
Hz), 4.21 (dd, 1 H, J ) 4.7, 12.3 Hz), 4.12 (dd, 1 H, J ) 2.1,
12.3 Hz), 3.98 (dd, 1 H, J ) 3.5, 9.4 Hz), 3.84 (dd, 1 H, J )
1.8, 10.0 Hz), 3.68 (ddd, 1 H, J ) 2.1, 4.7, 9.4 Hz), 3.67 (m, 2
H), 2.05, 2.02, 2.00, 1.99, 1.97, 1.92 (6 s, 18 H), 1.43, 1.31 (2 s,
6 H), 0.11 (s, 9 H). 13C NMR (125.7 MHz, CDCl3): δ 170.4,
170.3, 170.2, 169.5, 169.0, 138.1, 113.1, 100.7, 84.9, 84.7, 80.3,
79.4, 73.7, 73.1, 72.8, 68.1, 62.6, 61.9, 57.1, 26.0, 24.9, 22.8,
20.8, 20.7, 20.6, 20.4, 20.2, -0.65. FABMS: m/z 711 (80, [M +
Na]+). Anal. Calcd for C29H44N2O15Si: C, 50.57; H, 6.44; N,
4.07. Found: C, 50.56; H, 6.35; N, 3.93.
H-1), 5.23 (t, 1 H, J ) 9.5 Hz), 5.05 (t, 1 H, J ) 9.5 Hz), 4.96
(d, 1 H, J ) 9.5 Hz), 4.91 (t, 1 H, J ) 9.5 Hz), 4.79 (dd, 1 H,
J ) 3.5, 6.0 Hz), 4.65 (d, 1 H, J ) 6.0 Hz), 4.38 (dd, 1 H, J )
4.5, 10.5 Hz), 4.37 (m, 1 H), 4.36 (dd, 1 H, J ) 5.0, 10.5 Hz),
4.24 (dd, 1 H, J ) 12.5 Hz, J ) 4.5 Hz), 4.09 (dd, 1 H, J ) 3.5,
9.4 Hz), 4.08 (dd, 1 H, J ) 2.5, 12.5 Hz), 3.77 (ddd, 1 H, J )
2.5, 4.5, 12.5 Hz), 2.06, 2.04, 2.02, 2.00, 1.98, 1.92 (6 s, 18 H),
1.41, 1.27 (2 s, 6 H). 13C NMR (125.7 MHz, CDCl3): δ 178.2,
170.6, 170.4, 169.9, 169.5, 169.4, 160.2, 113.2, 100.5, 84.9, 83.5,
82.4, 79.3, 73.1, 72.9, 70.7, 70.6, 68.2, 61.8, 61.4, 25.8, 24.4,
21.0, 20.7, 20.6, 20.5. FABMS: m/z 639 (40, [M - AcOH +
Na]+), 617 (100, [M - AcO-]+. Anal. Calcd for C28H40N2O17
:
C, 49.70; H, 5.96; N, 4.14. Found: C, 49.63; H, 5.73; N, 4.10.
1-O-Acet yl-5-d eoxy-2,3-O-isop r op ylid en e-5-[3-(m et h -
yl 2,3,4-t r i-O-a cet yl-6-d eoxy-r-D-glu cop yr a n osyd -6-yl)-
car bodiim ido]-6-O-tr im eth ylsilyl-â-L-m an n ofu r an ose (36).
Column chromatography, eluent toluene and then 1:3 EtOAc-
petroleum ether; yield 183 mg (20%). [R]D +72.4 (c 1.0, CH2-
Cl2). Rf 0.20 (1:3 EtOAc-petroleum ether, two elutions). IR
(KBr): νmax 2951, 2133, 1752, 1371, 1228, 1100 cm-1. 1H NMR
(500 MHz, CDCl3): δ 6.07 (s, 1 H), 5.41 (t, 1 H, J ) 9.7 Hz),
4.93 (t, 1 H, J ) 9.7 Hz), 4.89 (d, 1 H, J ) 3.6 Hz), 4.82 (dd, 1
H, J ) 3.6, 6.9 Hz), 4.80 (dd, 1 H, J ) 3.6, 9.7 Hz), 4.63 (d, 1
H, J ) 6.9 Hz), 3.99 (dd, 1 H, J ) 3.6, 9.5 Hz), 3.81 (m, 1 H),
3.80 (dd, 1 H, J ) 2.5, 10.4 Hz,), 3.67 (dd, 1 H, J ) 5.1, 10.4
Hz), 3.63 (ddd, 1 H, J ) 2.5, 5.1, 9.5 Hz), 3.34 (d, 2 H, J ) 4.9
Hz), 3.38 (s, 3 H), 2.02, 2.00, 1.98, 195 (4 s, 12 H), 1.41, 1.30
(2 s, 6 H), 0.08, 0.07 (2 s, 9 H). 13C NMR (125.7 MHz, CDCl3):
δ 170.1, 170.0, 169.6, 169.3, 141.1, 113.1, 100.8, 96.6, 84.7, 80.5,
79.5, 70.9, 70.1, 70.0, 63.4, 62.8, 56.9, 55.5, 47.1, 26.1, 25.0,
21.0, 20.7, 20.6, 20.5, -0.50. FABMS: m/z 683 (30, [M + Na]+),
661 (100, [M + H]+). Anal. Calcd for C28H44N2O13Si: C, 50.89;
H, 6.71; N, 4.24. Found: C, 50.80; H, 6.81; N, 4.26.
Gen er a l P r oced u r e for th e P r ep a r a tion of 4-(L-Er yth -
r ofu r a n os-4′-yl)-2-a m in o-2-oxa zolin es (37-39). To a solu-
tion of the corresponding carbodiimide 34-36 (0.5 mmol) in
THF (10 mL) at 0 °C under Ar, TBAF (1 M in THF, 0.55 mL,
1.1 equiv) was added. In the case of 35, the reaction mixture
was adjusted at pH 7 using glacial AcOH. The solution was
stirred at 0 °C until the dissappearance of the starting material
(25 min), then diluted with Et2O (5 mL), washed with water
(2 × 3 mL), dried (MgSO4), filtered, and concentrated. For the
phenyl and â-D-glucopyranosyl derivatives 34 and 35, column
chromatography of the residue using the eluent indicated in
each case afforded the corresponding 2-amino-2-oxazoline
derivatives 37 and 38, respectively, as amorphous solids. In
the case of the (6 f 5)-carbodiimide linked pseudodisaccharide
36, partial deacetylation of the reaction product 39 was
observed under the stated reaction conditions. The mixture
was directly used in the next reaction step without further
purification.
Gen er a l P r oced u r e for th e P r ep a r a tion of Isou r ea -
Typ e (+)-6-Ep ica sta n osp er m in e An a logu es (40-42). To
a solution of the corresponding 2-amino-2-oxazoline precursor
37, 38 (0.43 mmol), or of the partially deacetylayted product
39 (see above) in dry MeOH (4 mL), methanolic NaMeO (1 M,
0.1 equiv per mol of acetate) was added. The reaction mixture
was stirred at rt for 30 min, then neutralized with solid CO2
and concentrated. The residue was treated with TFA-H2O (9:
1, 2 mL) for 15 min, concentrated under reduced pressure,
coevaporated several times with water, neutralized with
Amberlite IRA-68 (OH-) ion-exchange resin, and subjected to
column chromatography with the eluent indicated in each case.
The bicyclic 2-iminoindolizidine derivatives 40 and 41 were
thus obtained from 37 and 38, respectively, as white lyophi-
lyzates. The methyl R-D-glucopyranosid-6-ylimino derivative
42 was obtained after adjusting an aqueous solution of the
crude reaction product at pH 9 (0.1 M NaOH) and further
neutralization (0.1 m NaOH), as reported for the preparation
of the C-6 epimer 25. In all cases, the fully deprotected
compounds were further purified by GPC (Sephadex G-10, 1:1
MeOH-H2O).
(5R,6R,7R,8R,8a R)-5,6,7,8-Tet r a h yd r oxy-2-oxa -3-p h e-
n ylim in oin d olizid in e (40). Column chromatography, eluent
CH2Cl2 and then 50:1 f 9:1 CH2Cl2-MeOH; yield 104 mg
(86%). Rf 0.28 (9:1 CH2Cl2-MeOH). [R]D -19.1 (c 2.2, MeOH).
1H NMR (500 MHz, D2O): δ 7.36-7.05 (m, 5 H), 5.47 (bs, 1 H,
H-1), 4.64 (t, 1 H, J ) 8.3 Hz), 4.27 (t, 1 H, J ) 8.3 Hz), 4.12
(d, 1 H, J ) 2.8 Hz), 3.94 (dt, 1 H, J ) 8.3, 9.6 Hz), 3.90 (dd,
1 H, J ) 2.8. 9.6 Hz), 3.78 (t, 1 H, J ) 9.6 Hz). 13C NMR (125.7
MHz, D2O): δ 155.2, 146.6, 130.3, 124.9, 124.6, 78.1, 72.2, 71.5,
71.4, 56.2. FABMS: m/z 303 (30, [M + Na]+), 281 (80, [M +
H]+). Anal. Calcd for C13H16N2O5: C, 55.71; H, 5.75; N, 9.99.
Found: C, 55.53; H, 5.75; N, 9.81.
(5R,6R,7R,8R,8a R)-3-â-D-Glu cop yr a n osylim in o-5,6,7,8-
tetr a h yd r oxy-2-oxa in d olizid in e (41). Column chromatog-
raphy, eluent 3:1 MeCN-H2O; yield 142 mg (90%). [R]D -26.8
(c 1.0, H2O). Rf 0.31 (6:3:1 MeCN-H2O-NH4OH). 1H NMR
(500 MHz, D2O): δ 5.49 (d, 1 H, J ) 2.5 Hz), 5.00 (t, 1 H, J )
9.0 Hz), 4.87 (d, 1 H, J ) 9.0 Hz), 4.76 (t, 1 H, J ) 6.5 Hz),
4.25 (dt, 1 H, J ) 6.5, 9.0 Hz), 4.05 (t, 1 H, J ) 2.5 Hz), 3.78
(m, 2 H), 3.76 (dd, 1 H, J ) 2.0, 12.4 Hz), 3.62 (dd, 1 H, J )
5.2, 12.4 Hz), 3.43 (t, 1 H, J ) 9.0 Hz), 3.42 (ddd, 1 H, J ) 2.0,
5.2, 12.4 Hz), 3.37 (t, 1 H, J ) 9.0 Hz), 3.32 (t, 1 H, J ) 9.0
Hz). 13C NMR (125.7 MHz, D2O): δ 160.2, 82.7, 78.2, 77.9, 76.0,
(4R)-4-[(4′R)-1′-O-Acetyl-2′,3′-O-isop r op ylid en e-L-er yth -
r ofu r a n os-4′-yl]-2-p h en yla m in o-2-oxa zolin e (37). Column
chromatography, eluent CH2Cl2 and then 100:1 CH2Cl2-
MeOH; yield 130 mg (72%). [R]D +85.1 (c 0.7, CH2Cl2). Rf 0.30
(20:1 CH2Cl2-MeOH). IR (KBr): νmax 3428, 2975, 1752, 1680,
1
1553, 1386, 1243, 1013 cm-1. H NMR (500 MHz, CDCl3): δ
8900 J . Org. Chem., Vol. 68, No. 23, 2003

Isourea-Type Glycomimetics
74.0, 71.8, 70.7, 69.7, 69.4, 68.9, 60.3, 57.1. FABMS: m/z 389
403 (40, [M + Na]+), 381 (100, [M + H]+). Anal. Calcd for
14H24O10N2: C, 44.21; H, 6.36; N, 7.36. Found: C, 44.05; H,
6.22; N, 7.21.
(20, [M + Na]+), 367 (10, [M + H]+). Anal.Calcd for C13H22
-
C
N2O10: C, 42.62; H, 6.05; N, 7.65. Found: C, 42.46; H, 5.89;
N, 7.49.
(5R,6R,7R,8R,8aR)-5,6,7,8-Tetr ah ydr oxy-3-(m eth yl 6-de-
oxy-â-D-glu cop yr a n osyd -6-yl)im in o-2-oxa in d olizid in e
(42). Column chromatography, eluent 7:1 MeCN-H2O; yield
67 mg (70% over two steps). [R]D -22.0 (c 1.0, H2O). Rf 0.42
(6:3:1 MeCN-H2O-NH4OH). 1H NMR (500 MHz, D2O): δ 5.67
(d, 1 H, J ) 2.8 Hz), 5.07 (t, 1 H, J ) 8.4 Hz), 5.02 (d, 1 H, J
) 3.8 Hz), 4.74 (bt, 1 H, J ) 8.4 Hz), 4.36 (t, 1 H, J ) 2.8 Hz),
4.26 (m, 1 H), 4.12 (dd, 1 H, J ) 2.8, 9.6 Hz), 4.04 (t, 1 H, J )
9.6 Hz), 3.93 (ddd, 1 H, J ) 3.0, 7.5, 9.5 Hz), 3.91 (dd, 1 H, J
) 3.0, 13.8 Hz), 3.90 (t, 1 H, J ) 9.5 Hz), 3.63 (s, 3 H), 3.62
(dd, 1 H, J ) 7.5, 13.8 Hz), 3.59 (t, 1 H, J ) 9.5 Hz), 3.37 (t,
1 H, J ) 9.5 Hz). 13C NMR (75.5 MHz, D2O): δ 157.2, 99.1,
77.2, 73.0, 70.6, 70.0, 71.1, 70.9, 55.9, 55.0, 45.0. FABMS: m/z
Ack n ow led gm en t. We thank the Ministerio de
Ciencia y Tecnolog´ıa for financial support (Grant No.
BMC2001-2366-CO3-03) and the Fundacio´n Ca´mara for
a doctoral fellowship (M.I.G.-M.).
Su p p or tin g In for m a tion Ava ila ble: General methods
and experimental procedure for determination of glycosidase
1
inhibition constants (Ki), as well as fully assigned H and 13C
NMR data for all new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
J O034673M
J . Org. Chem, Vol. 68, No. 23, 2003 8901