Two different approaches to diphenylphosphinoyl hydroxy aldehydes and 1,2-diols are compared. A lengthy chiral auxiliary approach using proline-derived aminals enables hydroxy aldehydes and 1,2-diols of known absolute stereochemistry and high enantiomeric excess to be synthesised. In contrast, a much shorter asymmetric dihydroxylation route generates 1,2-diols with lower enantiomeric excesses and unexpected (in view of Sharpless's mnemonic) absolute stereochemistry. The dihydroxylation results are thus of both mechanistic and synthetic value.
比较了
二苯基膦酰羟基醛和 1,2
-二醇的两种不同方法。使用脯
氨酸衍生的
缩醛胺的冗长的手性辅助方
法能够合成已知绝对立体
化学和高对映体过量的羟基醛和1,2
-二醇。相比之下,更短的不对称二羟基化路线产生的1,2
-二醇具有较低的对映体过量和意想不到的(鉴于夏普莱斯的助记符)绝对立体
化学。因此,二羟基化结果具有机械价值和合成价值。