En Route to Novel Furanoside Mimics through Stereoselective Zinc-Mediated Propargylation of N-Benzyl Glycofuranosylamines Using Ultrasound Activation

Preliminary results on a novel zinc-mediated, ultrasound-promoted chain extension of glycofuranosylamines with a propargyl group are reported. The procedure was applied to d-arabino and d-xylo substrates to give, via Cram-chelate transition states, 1-C-1-(3-trimethylsilyl-2-propynyl)-1-benzylamino pentionols in moderate to good yields and acceptable stereoselectivities (syn/anti ≥4:1). To apply the reaction to the synthesis of galactofuranoside mimics, the d-xylo intermediate was cyclized to afford a 1-C-1-(2-propynyl)-1,4-dideoxy-1,4-imino-l-arabinitol derivative in excellent yield. This building block was used in three examples of CuAAC click reactions with azide compounds to provide the corresponding galactofuranoside mimics.