Enantioselective functionalization of prochiral diols via chiral spiroketals: preparation of optically pure 2-substituted 1,3-propanediol derivatives and asymmetric synthesis of chroman ring and side chain of .alpha.-tocopherol
Enantioselective functionalization of prochiral diols via chiral spiroketals: preparation of optically pure 2-substituted 1,3-propanediol derivatives and asymmetric synthesis of chroman ring and side chain of .alpha.-tocopherol