L. L. Rossi, A. Basu / Bioorg. Med. Chem. Lett. 15 (2005) 3596–3599
Table 1. Percentage inhibition of glycosidases by triazolesa
3597
toluene (3·), was dissolved in dry toluene (0.1 M), fol-
lowed by the addition of phenylacetylene (1.3 equiv)
and copper(I) iodide (0.1 equiv). Diisopropylethylamine
(1 equiv) was then added to the solution. The reaction
was allowed to stir at room temperature until tlc analysis
(1:1; ethyl acetate/hexane) indicated completion. The
solution was concentrated in vacuo and purified by flash
chromatography (1:1 ethyl acetate:hexane or 3:1 tolu-
ene:ethyl acetate as the eluent). A slight yellow coloration
in the resultant product was removed by trituration with
cold methanol to provide the purified product.
Compoundb
Enzymes
ECG (%)
SAG (%)
BLG (%)
5
<20
<20
<20
30 11
<20
<20
6
48 11
<20
<20
DNJGal
DNJGlu
91
<20
1
50
8
a Values are the averages of at least three experiments, with the
exception of the screenings of 6 and DNJGal with ECG, which were
only carried out twice.
b All compounds were screened at a concentration of 0.24 mM.
2.1.1. 4-Phenyl-1-(20,30,40,60-tetra-O-acetyl-b-D-galacto-
pyranosyl)-1,2,3-triazole (3). 1H NMR (CDCl3,
300 MHz): d 8.05, 1H, s; 7.86, 2H, d, J = 8.2 Hz; 7.47–
7.33, 3H, m; 5.90, 1H, d, J = 9.3 Hz; 5.64, 1H, t,
J = 9.8 Hz; 5.58, 1H, d, J = 3.2 Hz; 5.28, 1H, dd,
J = 3.3, 10.3 Hz; 4.28–4.11, 3H, m; 2.26, 2.05, 2.02, 1.90,
12H, s. 13C NMR (CDCl3, 300 MHz): d 170.4, 170.0,
169.8, 169.2, 148.4, 129.9, 128.8, 128.5, 128.2, 125.9,
117.8, 86.3, 74.0, 70.8, 67.7, 66.9, 61.2, 20.7, 20.5, 20.3.
HRMS (FAB) Calcd for C22H25N3O9Na [M+Na]+
498.1489. Found 498.1470. Mp: 197–199 ꢁC.
inhibitor of BLG than the galactose derivative 5, an
observation which is consistent with the known ability
of BLG to bind glucosides.11
The inhibition of ECG by the triazole 5 was examined in
greater detail at various substrate and inhibitor concen-
trations. These experiments indicated that 5 inhibited
ECG with a Ki value of 330 110 lM. In a similar man-
ner, the Ki of 6 for BLG was determined to be
1.6 0.4 mM. The Ki value of 5 is comparable to that
reported for the inhibition of ECG by the N-phenyl deriv-
ative of B (171 lM).4b However, the isosteric 5-phenyl-
1,3,4-oxadiazole derivative of galactose is a better inhibi-
tor of ECG (15 lM), indicating that subtle changes to
heteroatom positioning within the five-membered ring
affect the inhibitory potencies.4c
2.1.2. 4-Phenyl-1-(20,30,40,60-tetra-O-acetyl-b-D-glucopyr-
anosyl)-1,2,3-triazole (4). 1H NMR (CDCl3, 300 MHz): d
8.00, 1H, s; 7.84, 2H, d, J = 7.3 Hz; 7.46–7.33, 3H, m;
5.93, 1H, d, J = 9.1 Hz; 5.53, t, 1H, J = 9.5 Hz; 5.44,
1H, J = 9.5 Hz; 5.27, 1H, t, J = 9.7 Hz; 4.34, 1H, dd,
J = 5.1, 12.6 Hz; 4.16, 1H, d, J = 12.8 Hz; 4.03, 1H, m;
2.09, 2.04, 1.89, 12H, s. 13C NMR (CDCl3, 300 MHz): d
170.5, 169.9, 169.4, 169.0, 148.5, 129.8, 128.9, 128.6,
125.9, 117.7, 85.8, 75.2, 72.7, 70.1, 67.7, 61.5, 20.7, 20.5,
20.2. HRMS (FAB) Calcd for C22H25N3O9Na [M+Na]+
498.1489. Found 498.1480. Mp: 213–215 ꢁC.
Anomeric triazoles can be converted into better nucleo-
fuges upon protonation. Bro¨der and Kunz have shown
that electron-deficient glycosyl triazoles are converted to
the corresponding glycosyl fluorides upon treatment with
HFÆpyridine.8h Thus, it is possible that glycosyl triazoles
also serve as substrates for these enzymes. To rule out this
possibility, we incubated the triazoles with the enzymes
and subsequently examined the solutions for the presence
of phenyl triazole and glucose/galactose, which were not
detected by thin-layer chromatography or by ESI mass
spectrometry. Furthermore, we have evaluated the inhib-
itory properties of the potential hydrolysis products phen-
yl triazole and the parent sugars, and they do not exhibit
any appreciable inhibitory activity against these enzymes.
2.2. Representative procedure for the deacetylation of
glycosyl triazoles
The 4-phenyl-1-(tetraacetyl glycopyranosyl)-triazole
(0.40 mmol) was dissolved in methanol (50 mM). Freshly
prepared sodium methoxide (5 equiv) was then added
portionwise and the reaction was monitored by tlc (1:1
ethyl acetate/hexanes or 5:10:1 ethyl acetate/acetone/
water). Upon completion, Amberlite resin (H+ form)
was added until the solution was at neutral pH, and the
solution was filtered and concentrated in vacuo. The
crude product was taken up in water and treated with acti-
vated charcoal. The product was recrystallized from
water to give a white solid.
Modular synthesis of glycosyl triazoles is well-suited for
rapid generation of combinatorial libraries.5c,12 We are
currently preparing libraries of glycosyl triazoles in an ef-
fort to identify higher affinity inhibitors, as well as those
that are highly selective for individual glycosidases.
2.2.1. 4-Phenyl-1-b-D-glucopyranosyl-1,2,3-triazole (5).
1H NMR (CD3OD, 300 MHz): d 8.57, 1H, s; 7.84, 2H,
d, J = 8.4 Hz, 7.48–7.36, 3H, m; 5.61, 1H, d, J = 9.3 Hz;
4.20, 1H, t, J = 9.3 Hz; 4.00, 1H, d, J = 2.4 Hz; 3.89–
3.70, 4H, m. 13C NMR (CD3OD, 300 MHz): d 131.3,
130.1, 129.7, 126.8, 121.2, 90.6, 80.1, 75.3, 71.6, 70.4,
62.5. HRMS (FAB) Calcd for C14H17O5N3Na [M+Na]+
330.1058. Found 330.1066. Mp: 201–203 ꢁC.
2. Experimental procedures
b-Azido-galactopyranoside tetraacetate 1 and b-azido-
glucopyranoside tetraacetate 2 were prepared according
to the method of Tropper et al.13
2.1. Representative procedure for the preparation of
glycosyl triazoles via 3 + 2 cycloaddition
2.2.2. 4-Phenyl-1-b-D-galactopyranosyl-1,2,3-triazole (6).
1H NMR (CD3OD, 300 MHz): d: 8.58, 1H, s; 7.86, 2H,
d, J = 7.8 Hz; 7.49–7.35, 3H, m; 5.67, 1H, d, J = 9.2 Hz;
b-Azido-glycopyranoside tetraacetate (0.5 mmol), which
had been azeotropically dried by rotary evaporation of