Stereo- and regioselective glycosylation with protection-less sugar derivatives: an alluring strategy to access glycans and natural products

In the pursuit of developing potent drug molecules, more efficient and straightforward procedures are in high demand. The evergrowing interest in carbohydrate-based therapeutics and vaccines particularly calls for such reliable and universal approaches that assemble oligosaccharides rapidly and stereoselectively. Hereby, we compiled remarkable efforts made in exploring the possibilities of protection-less glycosylation strategies. Pioneering works using organotin reagents or catalysts were introduced first, followed by the organoboron successors that were deemed less toxic and more versatile alternatives. In the meantime, more species such as copper or caesium were also included and supported by a mechanistic rationale. Lastly, we hope to bring further insights into the synthesis of intricate carbohydrate derivatives, achieved with the aid of glycosylation methods discussed herein. This review delivers insights for dedicated chemists into the development of efficient methods in accessing carbohydrates at a lower cost.