Iterative Methodology for the Stereocontrolled Synthesis of Polyol Chains Employing 2-Acetylthiazole as Lactaldehyde Equivalent
作者:Alessandro Dondoni、Pedro Merino
DOI:10.1055/s-1993-25967
日期:——
The anti-diastereoselective addition (ds 90-92%) of the lithium enolate of 2-acetylthiazole to chiral (poly)alkoxy aldehydes and the stereocontrolled ketone reduction of the resultant aldols using diisobutylaluminum hydride/tetramethylammonium triacetoxyborohydride followed by the aldehyde unmasking from the thiazolering, afford three-carbon higher homologue aldehydes bearing a syn-or anti-1,3-diol unit. The iterative repetition of the sequence provides a route to polyhydroxylated chains having 1,3- and 1,2-diol units. In this methodology 2-acetylthiazole serves as the surrogate of lactaldehyde and its lithium enolate as the equivalent of the α-hydroxypropanal β-anion synthon.
将 2-乙酰基噻唑的锂烯酸盐与手性(多)烷氧基醛进行反二向选择性加成(ds 90-92%),并使用二异丁基氢化铝/四甲基三乙酰氧基硼氢化铵对生成的醛进行立体控制的酮还原,然后从噻唑化中拆醛、得到含有同或反-1,3-二醇单元的三碳高同族醛。通过迭代重复该序列,可以得到具有 1,3- 和 1,2- 二醇单元的多羟基链。在这种方法中,2-乙酰基噻唑可作为乳醛的替代物,而其锂烯醇则相当于δ-羟基丙醛的δ-阴离子合物。