Synthesis of the capsular polysaccharide of Streptococcus pneumoniae type 14

Synthesis of the regular branched polysaccharide -6(Gal beta 1-4)GlcNAc beta 1-3Gal beta 1-4Glc beta 1-]n structurally corresponding to capsular polysaccharide of Streptococcus pneumoniae type 14 involves blockwise synthesis of a tritylated 1,2-O-(1-cyano)ethylidene tetrasaccharide derivative from lactosamine and lactose precursors followed by stereospecific polycondensation of the tetrasaccharide monomer.