Synthése totale d'α‐disaccharidyles de tridésoxy‐2,5,6‐streptamine apparentés aux aminosides à partir du maltose et du lactose

Total synthesis of α‐disaccharidyl‐2,5,6‐trideoxy‐streptamines related to aminoglycoside antibiotics derived from maltose and lactose The synthesis of the hitherto unknown 4‐O‐substituted α‐linked pseudo‐tri‐saccharides 1,2 and 3 is described. The key intermediates required in the reaction sequence are the glycals 12, 13 and 14, prepared from maltose, lactose and the chiral ditosyloxy‐cyclohexanol 15, readily accessible from quinic acid. The pivotal step in the reaction's scheme ‐ a stereospecific α‐glycosylution procedure ‐, is an acid‐catalyzed addition of the alcohol 15 to the glycals 12, 13 and 14 leading to the corresponding 2,3‐unsaturated trisaccharides. The latter compounds were transformed to the target α‐glycosides of 2,5,6‐trideoxystreptamine 1, 2 and 3 which were devoid of significant antibacterial activity. These results indicate that the presence of an ether linkage at the position 4′ is probably critical for antibacterial activity.