Thioethyl donors

Scheme 2.13 Synthesis of a branched trisaccharide via thioethyl donors.

Figure 2.25 SP glycal protocol thioethyl donors for the synthesis of 2.86.

Notes and discussion. The sulfoxide donor 33 is easily prepared, as a single dia-stereomer, by treatment of the analogous thioethyl donor [46] with oxone in aqueous methanol. The key mannosylation reaction is achieved by activation of the sulfoxide with triflic anhydride in dichloromethane at - 78 °C in the presence of DTBMP. 

The next plateau to be reached was seen to be that of the full hexasaccharide core (Scheme 26). In an effort to maintain the tempo of the synthesis, we proceeded on to another assembly iteration with minimal protecting group-based transformations. The use of a thioethyl donor was explored however, in the end the direct roll over route proved more reproducible. To this end, iodosulfonamidation of 154 afforded... 

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