Dihydroxylation of Polyenes Using Narasaka's Modification of the Upjohn Procedure.

Dihydroxylation of a variety of commercially available polyenes has been investigated using phenylboronic acid, N-methylmorpholine N-oxide (NMO), and osmium tetroxide in anhydrous solvent. The diastereoselectivity of multiple oxidation steps is in some cases affected by the in situ protection of the intermediate ene-diols as phenyboronic esters, affording polyols not available from the standard Upjohn dihydroxylation procedure. A convenient oxidative deprotection of the phenylboronic esters is also described.