Structure–Activity Studies of N-Butyl-1-deoxynojirimycin (NB-DNJ) Analogues: Discovery of Potent and Selective Aminocyclopentitol Inhibitors of GBA1 and GBA2

Analogues of N-butyl-1-deoxynojirimycin (NB-DNJ) were prepared and assayed for inhibition of ceramide-specific glucosyltransferase (CGT), non-lysosomal β-glucosidase 2 (GBA2) and the lysosomal β-glucosidase 1 (GBA1). Compounds 5 a–6 f, which carry sterically demanding nitrogen substituents, and compound 13, devoid of the C3 and C5 hydroxy groups present in DNJ/NB-DGJ (N-butyldeoxygalactojirimycin) showed no inhibitory activity for CGT or GBA2. Inversion of stereochemistry at C4 of N-(n-butyl)- and N-(n-nonyl)-DGJ (compounds 24) also led to a loss of activity in these assays. The aminocyclopentitols N-(n-butyl)- (35 a), N-(n-nonyl)-4-amino-5-(hydroxymethyl)cyclopentane- (35 b), and N-(1-(pentyloxy)methyl)adamantan-1-yl)-1,2,3-triol (35 f), were found to be selective inhibitors of GBA1 and GBA2 that did not inhibit CGT (>1 mm), with the exception of 35 f, which inhibited CGT with an IC₅₀ value of 1 mm. The N-butyl analogue 35 a was 100-fold selective for inhibiting GBA1 over GBA2 (K_i values of 32 nm and 3.3 μm for GBA1 and GBA2, respectively). The N-nonyl analogue 35 b displayed a K_i value of ≪14 nm for GBA1 inhibition and a K_i of 43 nm for GBA2. The N-(1-(pentyloxy)methyl)adamantan-1-yl) derivative 35 f had K_i values of ≈16 and 14 nm for GBA1 and GBA2, respectively. The related N-bis-substituted aminocyclopentitols were found to be significantly less potent inhibitors than their mono-substituted analogues. The aminocyclopentitol scaffold should hold promise for further inhibitor development.