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 N
3
; X
1
is hydrogen, —CH
2
O—, —CH
2
NH—, —CH
3
, —CH
2
N
3
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 N
3
, and E is absent when X
1
is hydrogen, CH
3
or N
3
.