Catalytic Site-Selective Acylation of Carbohydrates Directed by Cation–n Interaction
摘要:
Site-selective functionalization of hydroxyl groups in carbohydrates is one of the long-standing challenges in chemistry. Using a pair of chiral catalysts, we now can differentiate the most prevalent trans-1,2-diols in pyranoses systematically and predictably. Density functional theory (DFT) calculations indicate that the key determining factor for the selectivity is the presence or absence of a cation-n interaction between the cation in the acylated catalyst and an appropriate lone pair in the substrate. DFT calculations also provided a predictive model for site-selectivity and this model is validated by various substrates.
monoacylate an antitumor saponin OSW-1 was developed using an organotin reagent to rapidly access its derivatives that are useful as chemical probes. 4″-O-Acylated OSW-1 derivatives bearing a fluorophore, an alkyne tag, or biotin were prepared in good yields and were shown to maintain highlycytotoxic activity.