(A) A combinatorial definition of the glycosidic linkage including four categorical features (2 × 3 × 4 × 2) = 48 subsets. (B) Synthesis of representative L-rhamnose-L-rhamnose disaccharides 26 (L-Rha-α-(1→4)-L-Rha-α-OMP) and 54 (L-Rha-β-(1→4)-L-Rha-α-OMP; see Table 1). Reaction conditions: (a) Tf2O, 2,6-di-tert-butyl-4-methylpyridine, 4-allyl-3,4-dimethoxybenzene, 4Å molecular sieves, CH2Cl2, -78°C, α-anomer: 89%, β-anomer: 6%; (b) H2, 10% Pd/C Degussa-type E101 NE/W, MeOH, 26: 59%, 54: 40%.