N-ALKYLATED NITROGEN-IN-THE-RING SUGARS - CONFORMATIONAL BASIS OF INHIBITION OF GLYCOSIDASES AND HIV-1 REPLICATION

The conformations of nitrogen-in-the-ring sugars and their N-alkyl der ivatives were studied from H-1 NMR analyses, mainly using (3)J(H,H) co upling constants and quantitative NOE experiments. No significant diff erence was seen in the ring conformation of 1-deoxynojirimycin (1), N- methyl-1-doexynojirimycin (2), and N-butyl-1-deoxynojirimycin (3). How ever, it was shown that the C6 OH group in 1 is predominantly equatori al to the piperidine ring, while that in 2 or 3 is predominantly axial , and its N-alkyl group is oriented equatorially. In the furanose anal ogues 1,4-dideoxy-1,4-imino-D-arabinitol (4) and its N-methyl (5) and N-butyl (6) derivatives, the five-membered ring conformation differed significantly by the presence or absence of the N-substituted group an d the length of the N-alkyl chain. Compound 3 reduced its inhibitory e ffect on almost all glycosidases, resulting in an extremely specific i nhibitor for processing alpha-glucosidase I since N-alkylation of 1 is known to enhance both the potency and specificity of this enzyme in v itro and in vivo. This preferred (C6 OH axial) conformation in 2 and 3 appears to be responsible for their strong alpha-glucosidase I activi ty. Compound 4 is a good inhibitor of intestinal alpha-glucohydrolases , alpha-glucosidase II, and Golgi alpha-mannosidases I and II, but its N-alkyl derivatives 5 and 6 markedly decreased inhibitory potential f or all enzymes tested. In the case of 2,5-dideoxy-2,5-imino-D-mannitol (DMDP, 7), which is a potent beta-galactosidase inhibitor, its N-meth yl (8) and N-butyl (9) derivatives completely lost potency toward beta -galactosidase as well. N-Alkylation of compounds 4 and 7, known well as potent yeast alpha-glucosidase inhibitors, resulted in a serious la ss of inhibitory activity toward yeast alpha-glucohydrolases. Activity of these nine sugar analogues against HIV-1 replication was determine d, based on the inhibition of virus-induced cytopathogenicity in MT-4 and MOLT-4 cells. Compounds 2 and 3, which are better inhibitors of al pha-glucosidase I than 1, proved active with EC(50) values of 69 and 4 9 mu g/mL in MT-4 cells and 100 and 37 mu g/mL in MOLT-4 cells, respec tively, while none of the furanose analogues exhibited any inhibitory effects on HIV-1. The change in potency and specificity of bioactivity by N-alkylation of nitrogen-in-the-ring sugars appears to be correlat ed with their conformational change.