The invention provides collections of orthogonally-protected monosaccharides as universal building blocks for the synthesis of glycoconjugates of non-carbohydrate molecules, neo-glycoconjugates and oligosaccharides. This orthogonal protection strategy allows for the specific deprotection of any substituent ono the saccharide ring, and greatly facilitates targeted or library-focused carbohydrate-related syntheses. In particular, the invention provides a universal monosaccharide building block of General Formula (I) or General Formula (II) in which A is a leaving group; X is hydrogen, O, N or N₃; X₁ is hydrogen, —CH₂O—, —CH₂NH—, —CH₃, —CH₂N₃ or —COO—; and B, C, D and E are protecting groups that can be cleaved orthogonally, and in which B, C, D and E are absent when X is hydrogen or N₃, and E is absent when X₁ is hydrogen, CH₃ or N₃. ##STR1##