寻找能够促进合成有用的有机反应并具有高水平的不对称诱导作用的新的对映选择性催化剂,应与对能够在化学过程中实现最佳效率的合适反应介质的关注相关联。我们已经研究了在非常规反应介质(例如离子液体和超分子凝胶)中环状内消旋化合物的对映选择性脱对称。为此,我们研究了反应体系中的几个变量:用作反应介质的离子液体的性质,胶凝溶剂,酸酐的结构,醇的结构,手性催化剂以及反应条件,即温度和时间。系统的不同组件会影响反应结果,进行1 H NMR研究。通常,非常规反应介质表现出比常规介质更好的性能,仅使用少量溶剂即可。在看起来在催化领域中很有希望的介质的离子液体凝胶中,已经在产率和对映体过量方面获得了良好的结果。此外,据我们所知,这是研究离子液体溶液和凝胶相中酸酐不对称醇解的第一个实例。
An alkaloid-mediated desymmetrization of meso-anhydrides via a nucleophilic ring opening with benzyl alcohol and its application in the synthesis of highly enantiomerically enriched β-amino acids
permits the isolation of the products in analytically pure form and the recovery of the alkaloids almost quantitatively. These hemiesters can be converted to N-protected β-amino esters by means of Curtius degradation of the corresponding acyl azides. Subsequent cleavage of both protecting groups by a single reaction step leads to the free β-amino acids in excellent yields. The efficiency of this procedure
possessing a NH functionality at C-1 position as monodentate hydrogen bond donor were developed and evaluated for enantioselective organocatalytic alcoholysis of meso-cyclic anhydrides. These structural diversified organocatalysts were found to induce high enantioselectivity in alcoholysis of anhydrides and was successfully applied to the asymmetric synthesis of (S)-GABOB.
enantioselective catalysts, able to promote synthetically useful organic reactions with high levels of asymmetric induction, should be associated with the attention to the suitable reaction medium able to achieve the best efficiency in chemical processes. We have investigated the enantioselective desymmetrization of cyclic meso-anhydrides in nonconventional reaction media such as ionic liquids and supramolecular
寻找能够促进合成有用的有机反应并具有高水平的不对称诱导作用的新的对映选择性催化剂,应与对能够在化学过程中实现最佳效率的合适反应介质的关注相关联。我们已经研究了在非常规反应介质(例如离子液体和超分子凝胶)中环状内消旋化合物的对映选择性脱对称。为此,我们研究了反应体系中的几个变量:用作反应介质的离子液体的性质,胶凝溶剂,酸酐的结构,醇的结构,手性催化剂以及反应条件,即温度和时间。系统的不同组件会影响反应结果,进行1 H NMR研究。通常,非常规反应介质表现出比常规介质更好的性能,仅使用少量溶剂即可。在看起来在催化领域中很有希望的介质的离子液体凝胶中,已经在产率和对映体过量方面获得了良好的结果。此外,据我们所知,这是研究离子液体溶液和凝胶相中酸酐不对称醇解的第一个实例。
Desymmetrization of acid anhydride with asymmetric esterification catalyzed by chiral phosphoric acid
Asymmetric desymmetrization of σ-symmetric acid anhydrides was achieved with chiralphosphoricacid as a Brønsted acid catalyst. The key of success was finding of benzhydrol and 2,2-diphenylethanol as the nucleophiles of choice. The corresponding half esters were obtained in good yields with high selectivity.
A novel asymmetric synthesis has been developed for the construction of the A-ring of a chiral precursor to calcifediol. The highlights of this synthesis include (i) the introduction of the stereochemistry at the C5-position of the A-ring through the organocatalytic enantioselective desymmetrization of a prochiral cyclicanhydride using a bifunctional urea catalyst and (ii) the introduction of the