A producer of validamycins, Streptomyces hygroscopicus subsp. linioneus, was found to produce additional pseudo-aminosugars besides previously reported valiolamine, valienamine, validamine, and hydroxyvalidamine. In this study, we report the isolation, structural elucidation, and α-glucosidase inhibitory effects of two new minor fermentation products, epivaliolamine and deoxyvalidamine. Epivaliolamine and deoxyvalidamine were isolated via column chromatography on Amberlite IRC-50, CM-Sephadex C-25, and Dowex-1 X2. Their structures were determined using 13C/1H NMR spectroscopy, chemical synthesis (epivaliolamine from valienamine), and chemical conversion (deoxyvalidamine from validamine): epivaliolamine is ID-(1(OH),3/1,2,4,5)-5-amino-1-C-(hydroxymethyl)-1,2,3,4-cyclohexanetetrol, and deoxyvalidamine is 1L-(1,3,4/6)-4-amino-6-C-(hydroxymethyl)-1,3-cyclohexanediol. Both compounds exhibited very weak inhibitory activities against porcine intestinal α-glucosidases; epivaliolamine showed only 1/1,000 the activity of valiolamine, demonstrating that the configuration of the hydroxymethyl group on C-1 is extremely important for α-glucosidase inhibitory activity.