Carbohydrates are ubiquitous in nature, yet general and efficient synthetic methods for their formation are rare. Furthermore, the site-selective manipulation of hydroxyl groups adds another level of difficulty to their longstanding synthetic issues. Using a pair of chiral catalysts, we can predictably differentiate many trans-1,2-diols in pyranoses. Our model is supported by DFT calculations, which indicate that site-selectivity hinges upon the presence or absence of a cation-n interaction between the cation in the acylated catalyst and a suitable lone pair in the substrate. Initially using O-glycosides, but recently expanding to S-glycosides, we have further validated this model on a variety of substrates. The predictive power of this method makes great strides towards streamlining the chemical synthesis of carbohydrates and will be useful for the investigation of more complex targets in the future.

Using chiral catalysts and cation-n interactions to direct site-selective acylation of carbohydrates

255th National Meeting (2018)

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