Common protection–deprotection strategies in carbohydrate synthesis

Chemical synthesis offers access to homogeneous complex glycans, which rely on protecting group (PG) chemistry. However, the overall efficiency of chemical glycan assembly is still far below when compared to oligonucleotide or oligopeptide synthesis as it is not template driven and requires regio- and stereocontrol. Over the past several years, significant efforts have been invested to improve the carbohydrate synthesis that includes PG manipulation and stereoselective glycoside formation and some of the advances have been relayed to the solid phase or programmable one-pot synthesis approaches. The protecting groups must be removed in the final stage of total synthesis to obtain the desired target oligosaccharide. Structural complexity and the nature of glycans make the removal of diverse protecting groups complicated. This aspect must be kept in mind while designing a suitable protecting group strategy for the synthesis.