Regioselective and Stereospecific Amination of Iridoids:  Conversion of Aucubin into Aminoside Antibiotic Analogues

Treatment of aucubin (1) with tert-butyldimethylsilyl chloride under alkaline conditions permitted regioselective silylation of either the primary hydroxyl groups at C-9 and C-6' or both primary hydroxyl groups and the secondary allylic hydroxyl group at C-6. Acetylation with acetic anhydride, followed by selective removal of the silyl groups and Mitsunobu reaction involving phthalimide as nitrogen donor, gave a stereospecific entry to aminoside antibiotic analogues: 10,6'-diamino-10,6'-dideoxyaucubin (16) and (6R)-6,10,6'-triamino-6,10,6'-trideoxyaucubin (17).