Synthesis and biological evaluation of guanidine-type iminosugars

Article abstract of DOI:10.1021/jo702374f

(Chemical Equation Presented) The preparation of carbohydrate mimics in which the endocyclic oxygen has been replaced by a guanidine-type nitrogen atom is reported. The synthetic strategy involves the furanose → piperidine rearrangement of 5-deoxy-5-guanidino-L-idose precursors. The reaction proceeds through elimination of water to give 3-oxopiperidines, which were isolated as the corresponding hydrates. Biological evaluation of the new glycomimetics evidenced a strong influence of the nature of the substituents at the nitrogen atoms on the glycosidase inhibitory properties.

Full text of DOI:10.1021/jo702374f

We have recently reported a new family of iminosugars in
which the endocyclic sp3 amine-type nitrogen atom has been
replaced by a neutral or very weakly basic pseudoamide-type
nitrogen (urea, thiourea, carbamate) with substantial sp2 char-
acter (“sp2-azasugars”).8 This subtle structural change substan-
tially modifies the reactivity and the stereoelectronic properties
at the pseudoanomeric region, with a dramatic increase in the
anomeric effect, which has been exploited in the design of
conformationally and configurationally stable reducing glyco-
mimetics in the indolizidine series (see structures 1 and 2 for
castanospermine and swainsonine analogues, respectively), some
of which behaved as highly selective and potent R-glucosidase
inhibitors.9
Synthesis and Biological Evaluation of
Guanidine-Type Iminosugars
Matilde Aguilar,† Paula D´ıaz-Pe´rez,†
M. Isabel Garc´ıa-Moreno,† Carmen Ortiz Mellet,*,† and
Jose´ M. Garc´ıa Ferna´ndez*,‡
Departamento de Qu´ımica Orga´nica, Facultad de Qu´ımica,
UniVersidad de SeVilla, Profesor Garc´ıa Gonza´lez 1, E-41012
SeVilla, Spain, and Instituto de InVestigaciones Qu´ımicas, CSIC
- UniVersidad de SeVilla, Ame´rico Vespucio 49, Isla de la
Cartuja, E-41092 SeVilla, Spain
mellet@us.es; jogarcia@iiq.csic.es
ReceiVed NoVember 7, 2007
Our general synthetic strategy to access sp2-azasugars is based
on the ability of the masked carbonyl group of an hexose
The preparation of carbohydrate mimics in which the
endocyclic oxygen has been replaced by a guanidine-type
nitrogen atom is reported. The synthetic strategy involves
the furanose f piperidine rearrangement of 5-deoxy-5-
guanidino-L-idose precursors. The reaction proceeds through
elimination of water to give 3-oxopiperidines, which were
isolated as the corresponding hydrates. Biological evaluation
of the new glycomimetics evidenced a strong influence of
the nature of the substituents at the nitrogen atoms on the
glycosidase inhibitory properties.
(3) (a) Sun, J.-Y.; Zhu, M.-Z.; Wang, S.-W.; Miao, S.; Xie, Y.-H.; Wang,
J.-B. Phytomedicine 2007, 14, 353. (b) Paulsen, H.; Brockhausen, I.
Glycoconjugate J. 2001, 18, 867. (c) Gross, P. E.; Baker, M. A.; Carver, J.
P.; Dennis, J. W. Clin. Cancer Res. 1995, 1, 935.
(4) (a) Anzeveno, P. B.; Creemer, L. J.; Daniel, J. K.; King, C.-H. R.;
Liu, P. S. J. Org. Chem. 1989, 54, 2539-2542. (b) Balfour, J. A.; McTavish,
D. Drugs 1993, 46, 1025.
(5) (a) Cren, S.; Gurcha, S. S.; Blake, A. J.; Besra, G. S.; Thomas, N. R.
Org. Biomol. Chem. 2004, 2, 2418. (b) Wrodnigg, T. M.; Sprenger, F. K.
Mini-ReV. Med. Chem. 2004, 4, 437.
(6) (a) Butters, T. D.; Dwek, R. A.; Platt, F. M. Chem. ReV. 2000, 100,
4683. (b) Cox, T. M.; Aerts, J. M. F. G.; Andria, G.; Beck, M.; Belmatoug,
N.; Bembi, B.; Chertkoff, R.; Vom Dahl, S.; Elstein, D.; Erickson, A.; Giralt,
M.; Heitner, R.; Hollak, C.; Hrebicek, M.; Lewis, S.; Mehta, A.; Pastores,
G. M.; Rolfs, A.; Miranda, M. C. S.; Zimran, A. J. Inherit. Metab. Dis.
2003, 26, 513. (c) Matsuda, J.; Suzuki, O.; Oshima, A.; Yamamoto, Y.;
Noguchi, A.; Takimoto, K.; Itoh, M.; Matsuzaki, Y.; Yasuda, Y.; Ogawa,
S.; Sakata, Y.; Nanba, E.; Higaki, K.; Ogawa, Y.; Tominaga, L.; Ohno, K.;
Iwasaki, H.; Watanabe, H.; Brady, R O.; Suzuki, Y. Proc. Nat. Acad. Sci.
U.S.A. 2003, 100, 15912.
(7) For reviews, see: (a) Broges de Melo, E.; da Silveira Gome, A.;
Carvalho, I. Tetrahedron 2006, 62, 10277. (b) Pearson, M. S. M.; Mathe´-
Allainmat, M.; Fargeas, V.; Lebreton, J. Eur. J. Org. Chem. 2005, 2159.
(c) Afarinkia, K.; Bahar, A. Tetrahedron: Asymmetry 2005, 16, 1239. (d)
Germain, D. P. Clin. Genet. 2004, 65, 77-86. (e) Cipolla, L.; La Ferla, B.;
Nicotra, F. Curr. Top. Med. Chem. 2003, 3, 1349. (f) Compain, P.; Martin,
O. R. Curr. Top. Med. Chem. 2003, 3, 541. (g) Asano, N. Curr. Top. Med.
Chem. 2003, 3, 471. (h) Lillelund, V. H.; Jensen, H. H.; Liang, X.; Bols,
M. Chem. ReV. 2002, 102, 515. (i) Asano, N.; Nash, R. J.; Molyneux, R.
J.; Fleet, G. W. J. Tetrahedron: Asymmetry 2000, 11, 1645. (j) Simmonds,
M. S. J.; Kite, G. C.; Porter, E. A. Taxonomic Distribution of Iminosugars
in Plants and Their Biological Activities. In Iminosugars as Glycosidase
Inhibitors; Stu¨tz, A., Ed.; Wiley-VCH: Weinheim, Germany 1999; p 8.
(8) (a) Garc´ıa-Moreno, M. I.; Ortiz Mellet, C.; Garc´ıa Ferna´ndez, J. M.
Tetrahedron 2007, 63, 7879. (b) Garc´ıa-Moreno, M. I.; D´ıaz-Pe´rez, P.; Ortiz
Mellet, C.; Garc´ıa Ferna´ndez, J. M. Eur. J. Org. Chem. 2005, 2903. (c)
Garc´ıa-Moreno, M. I.; Rodr´ıguez-Lucena, D.; Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J. M. J. Org. Chem. 2004, 69, 3578.
(9) (a) D´ıaz-Pe´rez, P.; Garc´ıa-Moreno, M. I.; Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J. M. J. Org. Chem. 2003, 68, 8890. (b) Garc´ıa-Moreno, M. I.;
D´ıaz-Pe´rez, P.; Ortiz Mellet, C.; Garc´ıa Ferna´ndez, J. M. Synlett 2003, 341.
(c) Garc´ıa-Moreno, M. I.; D´ıaz-Pe´rez, P.; Ortiz Mellet, C.; Garc´ıa Ferna´ndez,
J. M. Chem. Commun. 2002, 848. (d) 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. (e) Jime´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.
Polyhydroxylated alkaloids with iminosugar structure, usually
referred to as azasugars,1 display a broad range of interesting
biological activities potentially useful in the treatment of
ailments as varied as viral infections,2 including human immu-
nodeficiency virus (HIV),2a-e human hepatitis C (HCV),2f,g or
dengue virus,2i cancer,3 diabetes,4 tuberculosis,5 and lysosomal
storage diseases.6 The tremendous therapeutic potential of this
class of compounds has been ascribed to their ability to interact
with carbohydrate-processing enzymes, acting as competitive
inhibitors of glycosidases and/or glycosyltransferases, and has
strongly stimulated research in this area of glycobiology.7
† Universidad de Sevilla.
‡ Instituto de Investigaciones Qu´ımicas, CSIC - Universidad de Sevilla.
(1) 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-IUMB
nomenclature recommendations for carbohydrates, the accepted term being
“iminosugar”. See: McNaught, A. D. Pure Appl. Chem. 1996, 68, 1919.
(2) (a) Ratner, L.; Heyden, N. V.; Dedera, D. Virology 1991, 181, 180.
(b) Rudd, P. M.; Elliott, T.; Cresswell, P.; Wilson, I. A.; Dwek, R. A. Science
2001, 291, 2370. (c) Chery, F.; Cronin, L.; O’Brien, J. L.; Murphy, P. V.
Tetrahedron 2004, 60, 6597. (d) Lee, D.-S.; Jung, K.-E.; Yoon, C.-H.; Lim,
H.; Bae, Y.-S. Antimicrob. Agents Chemother. 2005, 49, 4110. (e) Greimel,
P.; Spreitz, J.; Stu¨tz, A. E.; Wrodnigg, T. M. Curr. Top. Med. Chem. 2003,
3, 513. (f) Alper, J. Science 2001, 291, 2338. (g) Pavlovic, D.; Neville, D.
C. A.; Argaud, O.; Blumberg, B.; Dwek, R. A.; Fischer, W. B.; Zitzmann,
N. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 6104. (h) Durantel, D.; Carrouee´-
Durantel, S.; Branza-Nichita, N.; Dwek, R. A.; Zitzmann, N. Antimicrob.
Agents Chemother. 2004, 48, 497. (i) Wu, S.-F.; Lee, C.-J.; Liao, C.-L.;
Dwek, R. A.; Zitzmann, N.; Lin, Y.-L. J. Virol. 2002, 76, 3596.
10.1021/jo702374f CCC: $40.75 © 2008 American Chemical Society
Published on Web 01/24/2008
J. Org. Chem. 2008, 73, 1995-1998
1995

SCHEME 1. Synthesis and Reactivity of sp2-Azasugars
SCHEME 2. Synthesis of 5-Guanidinosugars via
Carbodiimides
substituents, providing opportunity for the introduction of
molecular diversity in the glycomimetic structure. In order to
implement the general synthetic route shown in Scheme 1 for
accessing the target compounds, the preparation of structurally
diverse 5-deoxy-5-guanidino-L-idofuranose precursors, via car-
bodiimide intermediates, was first envisioned. On one hand, sp2-
azasugar with this hydroxylation profile exhibited the strongest
â-glycosidase inhibitory activity in the nortropane series. On
the other hand, since intramolecular glycosylation is particularly
favored for this sugar configuration, it is ideally suited to test
the validity of our approach.8b,10
Tandem Staudinger-aza-Wittig-type condensation14 of the
5-azido-5-deoxysugar 1015 with triphenylphosphine and phenyl
isothiocyanate proceeded smoothly in toluene at room temper-
ature to afford the phenylcarbodiimide derivative 11 in 80%
yield.10 Compound 11 was used as a pivotal synthetic interme-
diate in the preparation of the N′-phenyl- and N′-benzyl-N′′-
phenylguanidine derivatives 12 and 13 by reaction with
ammonium chloride or benzylamine hydrochloride, respectively.
Final de-O-acetylation provided the requested precursors 14 and
15 (Scheme 2).
The above methodology was much less efficient in the case
of compounds bearing exclusively alkyl substituents at the
nitrogen atoms. An alternative three-step synthetic strategy via
thiourea adducts was devised.16 Nucleophilic addition of
5-amino-5-deoxy-1,2-O-isopropylidene-L-idofuranose 1615 to
benzyl isothiocyanate yielded the corresponding thiourea 17,10
which was further O-acetylated (f18)17 and subjected to
desulfuration with mercuric oxide to give carbodiimide 19 (51%
overall yield). Subsequent addition of benzylamine hydrochlo-
ride to the heteroallene group afforded the N′,N′′-dibenzylguani-
dine derivative 20, which was finally deacetylated to the
corresponding diol 21. An analogous reaction sequence using
methyl 2,3,4-tri-O-acetyl-6-deoxy-6-isothiocyanato-R-D-glu-
copyranoside (22)18 provided the guanidine-linked pseudodis-
precursor (3) to act as the electrophilic target for the nitrogen
atom of a pseudoamide group located at the C-5 position through
the open-chain aldehyde form (4). Interestingly, monocyclic
analogues with N-(thio)carbamoylpiperidine structure (5) ex-
hibited a strong tendency to undergo further intramolecular
glycosylation involving the primary OH-6, leading to nortro-
pane-type (calystegine-type) glycomimetics (6) that exhibited
instead â-glucosidase inhibitory activity.10 Concomitant â-
elimination of water was observed as a minor side reaction
(f7).11 Attempts to isolate the resulting polyhydroxylated
N-(thio)carbamoyloxopiperidine (8) or the corresponding in-
tramolecular hemiacetal (9) for biological evaluation failed,
however (Scheme 1). We reasoned that replacing the neutral
(thio)urea or (thio)carbamate group into a strongly basic
guanidine functionality should prevent the formation of the
piperidine ring under the acidic conditions that promote the
intramolecular glycosylation step (route a). Under more basic
conditions, the elimination pathway leading to the 3-oxo
derivative would be favored (route b). This hypothesis has now
been translated into a practical synthesis of guanidine-type
iminosugars in the piperidine series. The synthesis of the key
guanidinosugar precursors, the scope of the approach, and the
preliminary biological evaluation of the new glycomimetics
against a panel of glycosidases are reported.
To the best of our knowledge, azasugar analogues in which
the endocyclic nitrogen atom is part of a guanidine functionality,
that is N-amidinoyliminosugars, have not been reported so far.12
Since the guanidinium group can establish, simultaneously,
strong electrostatic and bidentate hydrogen bond interactions
with complementary groups,13 it may interact favorably with
the two putative carboxylic residues in the active site of
glycosidases. Moreover, both the pKa values and additional
interactions with the enzyme may be modulated with appropriate
(14) For an example of the application of this transformation to access
sugar carbodiimides, see: (a) 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.
(10) Garc´ıa-Moreno, M. I.; Benito, J. M.; Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J. M. J. Org. Chem. 2001, 66, 7604.
(11) Garc´ıa Ferna´ndez, J. M.; Ortiz Mellet, C.; Benito, J. M.; Fuentes,
J. Synlett 1998, 316.
(15) Dax, K.; Graigg, B.; Grassberger, V.; Ko¨lblinger, B.; Stu¨tz, A. E.
J. Carbohydr. Chem. 1990, 9, 479.
(12) Previous examples of guanidine-type glycomimetics are restricted
to polyhydroxylated sugar-like cyclic guanidines. For selected examples,
see: (a) Jeong, J. H.; Murray, B. W.; Takayama, S.; Wong, C. H. J. Am.
Chem. Soc. 1996, 118, 4227. (b) Chan, A. W. Y.; Ganem, B. Tetrahedron
Lett. 1995, 36, 811. (c) Le Merrer, Y.; Gauzy, L.; Gravier-Pelletier, C.;
Depezay, J. C. Bioorg. Med. Chem. 2000, 307, 320.
(16) For a review on sugar thioureas, see: Ortiz Mellet, C.; Garc´ıa
Ferna´ndez, J. M. AdV. Carbohydr. Chem. Biochem. 1999, 55, 35.
(17) O-Acetylation must be effected at 0 °C to avoid concomitant N- or
S-acetylation. See: Garc´ıa-Moreno, M. I.; Benito, J. M.; Ortiz Mellet, C.;
Garc´ıa Ferna´ndez, J. M. Tetrahedron: Asymmetry 2000, 11, 1331.
(18) Garc´ıa Ferna´ndez, J. M.; Ortiz Mellet, C.; Fuentes, J. J. Org. Chem.
1993, 58, 5192.
(13) Beer, P. D.; Gale, P. A. Angew. Chem., Int. Ed. 2001, 40, 486.
1996 J. Org. Chem., Vol. 73, No. 5, 2008

SCHEME 3. Synthesis of 5-Guanidinosugars via Thioureas
SCHEME 4. Synthesis of the 5-Imidazolin-2-ylaminosugar
30
SCHEME 5. Synthesis of Guanidine-Type Iminosugars
accharide 27 through the corresponding thiourea (23, 24),
carbodiimide (25)19 and penta-O-acetylated guanidinosugar (26)
intermediates (Scheme 3).20
the acid with water nor after neutralization with Amberlite
IRA-68 (OH-) ion-exchange resin. At pH 11, spontaneous
rearrangement to the corresponding amidinoylpiperidine was
accompanied by concomitant dehydration reaction. The re-
sulting 3-oxopiperidines (see structure 8 in Scheme 1) were
isolated in quantitative yield as the corresponding hydrates 34-
36, 38, and 40. No formation of intramolecular hemiacetals
occurred even after acidification of the reaction products
(Scheme 5).
The 1H NMR spectra of the final compounds were in
agreement with the presence of two methylene groups in the
molecule, one of them coupled to the piperidine ring spin
system and the other one showing exclusively the geminal
coupling constant, corresponding to the hydroxymethyl
substituent at C-2 and the pseudoanomeric protons (H-6a, H-6b),
respectively. The coupling constant values between vicinal
protons at the piperidine ring (J2,3 and J3,4 g 9.0 Hz) were
indicative of either anti (180°) or eclipsed (0°) relative disposi-
tions, suggesting that the 1,4B boat conformation (H-2/H-3
eclipsed; H-3/H-4 anti) largely predominates over the 4C1 chair
conformation (H-2/H-3 gauche; H-3/H-4 anti) typical of L-ido-
configured N-(thio)carbamoylpiperidine-derived intramo-
lecular glycosides (see, as an example, the structures of the N′-
phenylamidinoyl, phenylcarbamoyl, and phenylthiocarbamoyl
derivatives 34, 41, and 42).
The preparation of compound 30, incorporating an aminoimi-
dazoline moiety, was next considered. This fragment has been
previously used in the rational design of artificial receptors for
phosphodiester and carboxylates.21 Coupling reaction of amine
16 with 2-(N-tert-butoxycarbonylamino)ethyl isothiocyanate
gave the corresponding thiourea adduct 28, which was trans-
formed into the required cyclic guanidine through a two-step
reaction sequence involving S-alkylation with methyl iodide and
aqueous TFA-promoted hydrolysis of the carbamate group
(Scheme 4).
Trifluoroacetic acid-promoted deisopropylidination of the 1,2-
O-isopropylidene-5-deoxy-5-guanidino-L-idofuranose derivatives
14, 15, 21, 27, and 30 afforded the fully unprotected furanose
compounds 31-33, 37, and 39 as mixtures of the corresponding
R- and â-anomers. Contrary to that previously observed for the
urea and thiourea counterparts,10 no formation of nitrogen-in-
the-ring isomers was observed neither during coevaporation of
(19) Compound 25 has been previously prepared by the Staudiger-aza-
Wittig-type condensation of azide 10 and isothiocyanate 22 in a much lower
(30%) yield. See ref 10.
(20) For a recent report on the synthesis of guanidine-linked pseudo-
oligosaccharides from thiourea precursors, see: Jime´nez Blanco, J. L.;
Bootello, P.; Benito, J. M.; Ortiz Mellet, C.; Garc´ıa Ferna´ndez, J. M. J.
Org. Chem. 2006, 71, 5136.
(21) Kneeland, D. M.; Ariga, K.; Lynch, V. M.; Huang, C.-Y.; Anslyn,
E. V. J. Am. Chem. Soc. 1993, 115, 10042.
J. Org. Chem, Vol. 73, No. 5, 2008 1997

Experimental Section
General Procedure for the Preparation of 5-Deoxy-5-guani-
dinium-L-idofuranose Salts (31-33, 37, and 39). A solution of
14, 15, 21, 27, or 30 (0.47 mmol) in a mixture of TFA/H2O (9:1,
2.6 mL) was stirred at 0 °C for 30 min until disappearance of the
starting material (TLC). The solvent was removed under vacuum
and the residue coevaporated several times with water. Finally, HCl
0.1 M was added to an aqueous solution of the residue until pH
5.0, and the resulting solution was freeze-dried.
Data for 5-deoxy-5-(N′-phenylguanidino)-L-idofuranose hy-
drochloride (31) as an example: yield 150 mg (94%); Rf 0.56
(6:3:1 MeCN-H2O-NH4OH); [R]D ) -3 (c 1.0, H2O); 1H NMR
(300 MHz, D2O, 323 K) δ 7.47-7.26 (m, 10 H, Ph), 5.42 (d, 1 H,
J1,2 ) 4.1 Hz, H-1R), 5.21 (d, 1 H, J1,2 ) 0.9 Hz, H-1â), 4.29 (m,
2 H, H-3R, H-4R), 4.23 (dd, 1 H, J4,5 ) 7.2 Hz, J3,4 ) 4.7 Hz,
H-4â), 4.18 (dd, 1 H, J2,3 ) 1. 9 Hz, H-3â), 4.05 (m, 3 H, H-2R,
H-2â, H-5â), 3.92 (m, 1 H, H-5R), 3.80 (dd, 1 H, J6a,6b ) 11.8 Hz,
J5,6a ) 4.0 Hz, H-6aâ), 3.75 (dd, 1 H, J6a,6b ) 11.7 Hz, J5,6a ) 4.4
Hz, H-6aR), 3.65 (dd, 1 H, J5,6a ) 6.9 Hz, H-6bâ), 3.63 (dd, 1 H,
J5,6b ) 7.5 Hz, H-6bR); 13C NMR (75.5 MHz, D2O, 323 K) δ 156.2
(CN), 134.5-125.8 (Ph), 102.0 (C-1â), 96.1 (C-1R), 80.8 (C-2â),
80.7 (C-4â), 77.2 (C-4R), 76.3 (C-2R), 74.7 (C-3R), 74.5 (C-3â),
61.5 (C-6R), 61.3 (C-6â), 54.8 (C-5â), 54.0 (C-5R); FABMS m/z
298 (100, [M - Cl]+). Anal. Calcd for C13H20N3O5Cl: C, 46.78;
H, 6.04; N, 12.60. Found: C, 46.67; H, 5.94; N, 12.41.
The inhibitory activities of the N-amidinoylpiperidine aza-
sugars 34-36, 38, and 40 for R-glucosidase (yeast), â-glucosi-
dase (almonds), â-glucosidase (bovine liver, cytosolic), and
R-galactosidase (green coffee beans), in comparison with data
for the related bicyclic compounds 41 and 42,10 are summarized
in Table 1. The N′-phenylamidinoyl derivative 34 behaved as a
selective but weak inhibitor of both â-glucosidases, in stark
contrast with the very selective and strong inhibition of the
bovine â-glucosidase by the calystegine-type N′-phenyl(thio)-
carbamoyl glycomimetics 41 and 42. The selectivity toward the
mammalian enzyme is recovered in the case of the N′,N′′-
disubstituted derivatives 35 and 36, though the inhibition
potency remains over 1 order of magnitude weaker. Interest-
ingly, the presence of the hydrophilic sugar substituent in 38
results in a full reversion of the â-glucosidase selectivity. The
inhibition was totally abolished for the N-imidazolinylpiperidine
40. None of these compounds inhibited R-glucosidase, in
agreement with the linkage specificity previously encountered
in the L-idose-derived sp2-azasugars 41 and 42. Inhibition of
R-galactosidase, a typical feature of calystegine-type glycomi-
metics, does not occur for the monocyclic piperidine derivatives
34-36, 38, and 40.
General Procedure for the Preparation of N-Amidinoylpip-
eridine Salts (34-36, 38, and 40). An aqueous solution of the
corresponding guanidinium salt 31-33, 37, or 39 (0.15 mmol) was
treated with Amberlite IRA 68 (OH-) ion-exchange resin until pH
11. The resin was filtered and the aqueous solution neutralized and
freeze-dried.
Data for (2R,3R,4S)-1-(N′-phenylamidinoyl)-3,4,5,5-tetrahy-
droxy-2-hydroxymethylpiperidine hydrochloride (34) as an
example: yield 50 mg (100%); Rf 0.39 (6:3:1 CH3CN-H2O-NH4-
1
OH); [R]D ) -6 (c 1.0, H2O); H NMR (500 MHz, D2O, 313 K)
TABLE 1. Inhibition Constants (Ki, µM) for the
N-Amidinoylpiperidine Derivatives 34-36, 38, and 40 in
Comparison with Data for the Calystegine-Type N-(Thio)carbamoyl
Derivatives 41 and 42
δ 7.59-7.39 (m, 5 H, Ph), 3.85 (m, 5 H, H-3, H-2, H-6a, H-6b,
CHaOH), 3.66 (d, 1 H, J3,4 ) 9.2 Hz, H-4), 3.57 (m, 1 H, CHb-
OH); 13C NMR (125.7 MHz, D2O, 313 K) δ 156.2 (CN), 135.1-
125.9 (Ph), 98.1 (C-5), 72.3 (C-3), 71.1 (C-4), 63.6 (CH2OH), 60.0
(C-6), 54.0 (C-2). FABMS m/z 298 (80, [M - Cl]+). Anal. Calcd
for C13H20N3O5Cl‚H2O: C, 44.38; H, 6.30; N, 11.94. Found: C,
44.43; H, 6.43; N, 11.54.
enzyme
34
35
36
38
40
41
42
R-glucosidase (yeast)
â-glucosidase (almonds)
â-glucosidase (bovine liver)
926 n.i.a n.i. n.i. n.i. n.i.
n.i.
217 n.i.
n.i. 323 n.i. 1500 970
367 732 303 n.i. n.i. 30
2.5
172
R-galactosidase (green coffee) n.i. n.i.
n.i. n.i. n.i. 137
Acknowledgment. We thank the Spanish Ministerio de
Educacio´n y Ciencia (contract nos. CTQ2007-61180/PPQ and
CTQ2006-15515-C02-01/BQU) and the Junta de Andaluc´ıa for
financial support. The M.E.C. is also acknowledged for a
doctoral fellowship (to M.A.)
a No inhibition detected at 2 mM.
In summary, we have described an efficient synthetic route
to guanidine-type iminosugars based on the ability of the
carbonyl group of an l-idose precursor to act as the electrophilic
target for the nitrogen atom of a guanidine substituent located
at the C-5 position. The approach is compatible, in principle,
with the introduction of molecular diversity both at the level of
the piperidine ring configurational pattern and at the number
and nature of the N-substituents, being ideally suited for
structure-activity studies and inhibitor optimization. Research
in that direction is currently underway in our laboratories.
Supporting Information Available: General experimental
details, full purification and characterization data for the prepared
compounds, and experimental procedures for determination of
glycosidase inhibition constants (Ki). This material is available free
of charge via the Internet at http://pubs.acs.org.
JO702374F
1998 J. Org. Chem., Vol. 73, No. 5, 2008