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 (Ki values of 32 nm and 3.3 μm for GBA1 and GBA2, respectively). The N‐nonyl analogue 35 b displayed a Ki value of ≪14 nm for GBA1 inhibition and a Ki of 43 nm for GBA2. The N‐(1‐(pentyloxy)methyl)adamantan‐1‐yl) derivative 35 f had Ki 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. β‐Glucosidase‐selective inhibitors: Aminocyclopentitols were prepared and assayed for inhibition of carbohydrate‐processing enzymes, including CGT, GBA1, and GBA2. N‐Butylaminocyclopentitol was found to be a potent and selective inhibitor of GBA1. The N‐nonyl and N‐1‐((pentyloxy)methyl)adamantan‐1‐yl analogues potently inhibited both GBA1 (Ki≪14 nm, and Ki≤16, respectively) and GBA2 (Ki≪43 nm, and Ki=14 nm, respectively). The butyl and nonyl analogues did not inhibit CGT at 1 mm, and the Ki value for the adamantyl analogue was 1 mm. The N‐alkylaminocyclopentitols hold promise for future inhibitor development.