Large scale synthesis and regioselective protection schemes of ethyl 2-azido-2-deoxy-1-thio-alpha-D-cellobioside for preparation of heparin thiodisaccharide building blocks

Crystalline acetylated ethyl 2-azido-2-deoxy-1-thio-a-D-cellobioside has been prepared on a multigram scale from cellobiose in an overall yield of 23% with no chromatography required and converted after deacetylation into the 40,60-O-benzylidene and 40,60-O-benzylidene-6-O-TBDMS protected derivatives. Applying a number of regioselective benzylation methods on these gave access to a variety of regioselectively protected derivatives, both mono-ols (20- and 3-OH), diols (20,6-, 20,3-, and 3,6-di-OH), and triols (20,3,6- and 20,30,3-tri-OH). A number of these derivatives were further processed by benzoylation followed by removal or opening of the benzylidene acetal and selective oxidation of the exposed primary alcohol to give heparin building block intermediates comprising a range of possible sulfation patterns.