Catalyst-Controlled, Site-Selective Sulfamoylation of Carbohydrate Derivatives.

Methods for site-selective sulfamoylation of secondary hydroxyl groups in pyranosides are described. Using a boronic acid catalyst, selective installation of a Boc-protected sulfamoyl group at the equatorial position of -diols in manno- and galacto-configured substrates has been achieved. Activation of -diol groups in gluco- and galacto-configured substrates is also possible by employing an organotin catalyst.

Photocatalytic, site-selective oxidations of carbohydrates.

Site-selective oxidations of carbohydrates, employing acridinium photocatalysis and quinuclidine hydrogen atom transfer catalysis, are presented. Protocols have been developed for oxidations of all-equatorial carbohydrates as well as those containing -1,2-diols. Site-selectivity reflects the relative rates of hydrogen atom transfer from the carbohydrate C-H bonds, and can be enhanced using a phosphate hydrogen-bonding or boronic acid catalyst.

Site- and Stereoselective C-H Alkylations of Carbohydrates Enabled by Cooperative Photoredox, Hydrogen Atom Transfer, and Organotin Catalysis.

Diorganotin dihalides act as cocatalysts for site-selective and stereoselective couplings of diol-containing carbohydrates with electron-deficient alkenes in the presence of an Ir(III) photoredox catalyst and quinuclidine, a hydrogen atom transfer mediator. Quantum-chemical calculations support a proposed mechanism involving the formation of a cyclic stannylene acetal intermediate that shows enhanced reactivity toward hydrogen atom abstraction by the quinuclidinium radical cation. Addition of the carbon-centered radical to the alkene partner results in -alkylation of the carbohydrate substrate.