Synthesis of an Inositol Phosphoglycan Fragment found in Leishmania Parasites

Abstract Synthesis of 1 and 2a is described using a block synthetic strategy. Compound 4 was used as precursor for the two mannose derivatives which, coupled together, forms the dimannoside building block. Thioglycoside 7 was coupled to 8 yielding inositol phosphoglycan 9a , which was selectively deprotected and reacted with 2,3,4,6-tetra- O -benzyl-α- d -glucopyranos-1-yl H-phosphonate to form the protected target molecule 12 . Deprotection of 12 by acidic deacetalisation/desilylation and subsequent catalytic hydrogenolysis resulted in cleavage of the anomeric phosphodiester to produce 1 . Debenzylation with sodium in liquid ammonia followed by acidic deacetalisation/desilylation gave the target compound 2a .