Dansyl-modifled β-cyclodextrin decreases its fluorescence intensity upon guest binding, and this phenomenon was used to detect steroidal compounds. This system exhibited remarkable molecular recognition, showing high sensitivities for ursodeoxycholic acid and chenodeoxycholic acid.

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We report a new catalytic method for alcohol sulfamoylation that deploys electron-deficient aryl sulfamates as activated group transfer reagents. The reaction utilizes the simple organic base N-methylimidazole, proceeds under mild conditions, and provides intrinsic selectivity for 1° over 2° alcohols (up to >40:1 for certain nucleosides). The requisite aryl sulfamate donors are stable crystalline solids that can be readily prepared on a large scale. Mechanistic considerations support the intermediacy of HNSO2 “aza-sulfene” in the transfer reaction.

A novel radical-based strategy for accessing the unique tetracyclic skeleton of resiniferatoxin is described. The synthetic route is characterized by a stereoselective synthesis of the C-ring which has a bridgehead O,Se-acetal, a three component radical coupling of the A-and C-rings and a branched allyl stannane, and a 7-endo radical cyclization to construct the fused B-ring from the coupling adduct. The present approach attests to the power of radical reactions to realize the congested C-C bond formations required for synthesizing highly functionalized compounds.Scheme 1 Structures and retrosynthetic analysis of resiniferatoxin and daphnetoxin.