Novel organocatalysts derived from L-threonine and L-leucine have been synthesized for catalyzing directaldolreactions of hydroxycetone and unactivated aliphatic aldehydes with as low as 2 mol% loading of the catalyst, good to excellent yields and excellent enantioselectivities have been achieved for aliphatic aldehydes, whereas aromatic aldehydes yield only moderate enantioselectivities.
Asymmetric dihydroxylation of α,β-unsaturated ketones provided α,β-dihydroxyketones with up to 100% ee. The Cα-O bond of these intermediates or their bis-TMS ethers, acetonides, phenylborates or orthoformiates was cleaved with SmI2, affording β-hydroxyketones. The latter can be reduced to furnish syn- or anti-configured 1,3-diols of any desired configuration.
α,β-不饱和酮的不对称二羟基化提供了高达 100% ee 的 α,β-二羟基酮。这些中间体或其双TMS 醚、丙酮化合物、苯硼酸盐或原甲酸盐的Cα-O 键被SmI2 裂解,得到β-羟基酮。后者可被还原以提供任何所需构型的顺式或反式1,3-二醇。