Bioorganic & Medicinal Chemistry Letters
Synthesis of N-alkylated noeurostegines and evaluation of their potential
as treatment for Gaucher’s disease
Tina S. Rasmussen a, Sarah Allman b, Gabriele Twigg b, Terry D. Butters b, , Henrik H. Jensen a,
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a Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
b Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The potent and selective inhibitor of b-glucosidases, noeurostegine, was evaluated as an inhibitor of
glucocerebrosidase (GCase) to give an IC50 value of 0.4 M, being 250- and 150-fold better than N-butyl
and N-nonyl noeurostegine, respectively. The parent noeurostegine and its N-butyl and N-nonyl alkylated
congeners were also tested as pharmacological chaperones against a N370S GCase mutant. Of these, only
noeurostegine, was found to increase enzyme activity, which in potency was comparable to that
previously reported for isofagomine.
Received 1 December 2010
Revised 21 December 2010
Accepted 22 December 2010
Available online 8 January 2011
l
Keywords:
Nortropane
Inhibition
Ó 2011 Elsevier Ltd. All rights reserved.
Glucocerebrosidase
Chaperone
Gaucher’s disease is a lysosomal storage disorder caused by
inherited genetic mutations in the GBA gene, which results in defi-
cient activity of glucocerebrosidase (GCase). Deficient GCase activ-
ity leads to progressive accumulation of glucosylceramide (GlcCer),
primarily in the lysosomes of Gaucher’s patients, causing hepato-
splenomegaly, anaemia, bone lesions, and, in more severe cases,
central nervous system impairment.1 Gaucher’s disease is the most
common of all lysosomal storage disorders with a prevalence of 1
in 40,000–60,000 in the general population and 1 in 800 among the
Ashkenazi Jewish population.2
The disease is clinically classified into three types based on the
age of onset and the degree of neurological involvement, the most
common and mild form being type 1.3 Although more than 200 dif-
ferent mutations in GCase have been reported, N370S is the most
prevalent disease-causing mutation and is associated with type 1
disease.4 There is no cure for Gaucher’s disease, but there are three
types of therapies available to patients.
course of the disease can be improved. However, several draw-
backs concerning this therapy have also been identified.9
A very promising therapeutic strategy uses small molecule
pharmacological chaperones, often competitive enzyme inhibitors,
to facilitate proper folding and trafficking of the lysosomal en-
zymes. The pharmacological chaperones act as a folding template
for mutant enzymes and stabilize the conformation of the enzyme
detected by the quality control system, thus avoiding the endo-
plasmic reticulum-associated degradation (ERAD) pathway.10
It is known that calystegines A3 (1), B1 (2), B2 (3) and C1 (4), nat-
urally occurring nor-tropane glycoside hydrolase inhibitors also act
as pharmacological chaperones increasing the GCase activity in
Gaucher fibroblasts up to two-fold over untreated cells.11 However,
the effective concentrations needed of the calystegines (1–4, Fig. 1)
are 2–20-fold larger than observed for isofagomine (5), this indi-
cates that isofagomine (5) is a more effective pharmacological
chaperone for GCase. It has also been indicated that the hydroxy-
methyl present in isofagomine (5) is important for interaction with
the protein.11 On the other hand, isofagomine (5) is lacking the
2-OH which in studies have been shown to contribute significantly
to enzyme binding.12,13
Enzyme replacement therapy (ERT)5 is available to type 1
Gaucher’s patients and involves intravenous infusion of recombi-
nant form of GCase (CerezymeÒ).6 This therapy is very expensive,
with an estimated annual cost upwards of $200,000 per patient.7
Another therapy is called substrate reduction therapy. This in-
volves inhibiting the enzyme responsible for GlcCer biosynthesis,
for example, by administrating N-butyl deoxynojirimicin (NB-DNJ,
Miglustat, ZavescaÒ).8 With a reduction in the amount of GlcCer
being synthesized, less is stored in the lysosome and the clinical
Recent results from our group have shown that noeurostegine (7,
Fig. 1) is a potent inhibitor of b-glucosidase from sweet almonds and
T. maritima.14 This (7) was designed as a hybrid of inherently unsta-
ble and unselective noeuromycin (6) and the stable and selective
calystegine B2 (3), and therefore contains both the hydroxymethyl
substituent and the important 2-OH.
Based on our initial promising results with noeurostegine we
set out to evaluate whether this nor-tropane and its N-butyl and
N-nonyl analogues too were inhibitors of GCase. Furthermore,
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Corresponding authors. Tel.: +45 89423963; fax: +45 86196199.
(H.H. Jensen).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.