Oxidative Cyclization of Diols Derived from 1,5-Dienes: Formation of Enantiopure cis-Tetrahydrofurans by Using Catalytic Osmium Tetroxide; Formal Synthesis of (+)-cis-Solamin

High yields and high levels of stereocontrol are observed in the oxidative cyclization of vicinal diols using catalytic amounts of a transition metal (see scheme; TFA=trifluoroacetic acid). The product stereochemistry is controlled completely by the starting material, and, importantly, single enantiomers can be accessed readily. The reaction sequence is demonstrated in a very short formal synthesis of the natural product (+)‐cis‐solamin.