Ultrasonic assisted Fischer glycosylation: generating diversity for glycochemistry

In this study ultrasound has been utilised for the Fischer glycosylation using free sugars and sulphuric acid immobilized on silica as catalyst. N-acetyl-d-glucosamine, N-acetyl-d-galactosamine, d-glucose, d-galactose, d-mannose, l-fucose, and lactose were glycosylated with propargyl alcohol or 2-azidoethanol affording the corresponding glycosides, with the production of the α-glycopyranoside as the dominant product. Remarkable acceleration of the glycosylation reactions (15 min–2 h compared to several hours) over reported procedures together with good yields were always observed.