Mechanistic Insights into the Chaperoning of Human Lysosomal-Galactosidase Activity: Highly Functionalized Aminocyclopentanes and C-5a-Substituted Derivatives of 4-epi-Isofagomine

Abstract

Glycosidase inhibitors have shown great potential as pharmacological chaperones for lysosomal storage diseases. In light of this, a series of new cyclopentanoid β-galactosidase inhibitors were prepared and their inhibitory and pharmacological chaperoning activities determined and compared with those of lipophilic analogs of the potent β-d-galactosidase inhibitor 4-epi-isofagomine. Structure-activity relationships were investigated by X-ray crystallography as well as by alterations in the cyclopentane moiety such as deoxygenation and replacement by fluorine of a “strategic” hydroxyl group. New compounds have revealed highly promising activities with a range of β-galactosidase-compromised human cell lines and may serve as leads towards new pharmacological chaperones for GM1-gangliosidosis and Morquio B disease.

Pharmacological Chaperones for β‐Galactosidase Related to GM1‐Gangliosidosis and Morquio B: Recent Advances

“…[94] Additionally, the (5aR) configurated 5a-Cdansylaminohexyl derivative 25 was found as most active inhibitor in this series with an IC 50 value of 0.094 μM against human β-galactosidase and maximum chaperoning effect of 10.7-fold increased activity in the R201C cell line at 0.5 μM. [66] In keeping with the trend in this series of compounds, the corresponding (5aS)-derivative 20 did not match the pronounced biological activity of its (5aR)-epimer. (Table 1, Scheme 6, Supporting Information).…”

“…(Figure 8) A reasonably simple synthetic route based on Vasella's (2+3)‐cycloaddition method [96] paired with high expectations of potent inhibitors and – hopefully – powerful chaperones prompted this most recent field of interest. Known amino(hydroxymethyl)cyclopentanetriol 27 [97] could easily be prepared and its amino group chemoselectively addressed employing conventional N‐alkylation or reductive amination conditions to give compounds 26 , 28 – 30 [66,99] . (Figure 8) (Scheme 8, Supporting Information )…”

“…With R201H/H281Y (adult G M1 ‐gangliosidosis), both structural types, 24 as well as 30 , show β‐galactosidase activity increases of 6‐ to 7‐fold at 0.1 μM and 9.1‐ to 10‐fold at 1 μM with slight advantages for the isofagomine derivative [66] . Interestingly, with Y333H/Y333H (juvenile G M1 ‐gangliosidosis), carbacycle 30 is the most potent chaperone with a maximum activity of 8.7‐fold at 10 μM, followed by NOEV ( 4 , 7.5‐fold at 25 μM) and 24 (5.0‐fold at 25 μM) [66] . (Table 1, Supporting Information )…”

“…[65] Additionally, a bacterial GH35 β-galactosidase model featuring sufficient homology and similarity of the active site has recently been shown highly useful. [66]…”

“…(structure of compounds 4 – 7 in Figure 3) Furthermore, crystal structures of the enzyme mutant I51T (which is frequent amongst G M1 ‐gangliosidosis patients in Japan) in complex with compound 5 (PDB 3WF4) and with d ‐galactose (PDB 3WF3) have been reported [65] . Additionally, a bacterial GH35 β‐galactosidase model featuring sufficient homology and similarity of the active site has recently been shown highly useful [66] …”