Unanticipated Silyl Transfer in Enantioselective α,β-Unsaturated Acyl Ammonium Catalysis Using Silyl Nitronates
作者:Anastassia Matviitsuk、Mark D. Greenhalgh、James E. Taylor、Xuan B. Nguyen、David B. Cordes、Alexandra M. Z. Slawin、David W. Lupton、Andrew D. Smith
DOI:10.1021/acs.orglett.9b04404
日期:2020.1.3
The use of silyl nitronates is reported for the isothiourea-catalyzed synthesis of γ-nitro-substituted silyl esters containing up to two contiguous stereocenters in good yields with excellent enantioselectivities (up to 93% yield and 99:1 er). The serendipitously discovered formation of silyl ester products in this reaction demonstrates a novel platform for catalyst turnover in α,β-unsaturated acyl
Chiral Brønsted Base-Promoted Nitroalkane Alkylation: Enantioselective Synthesis of <i>sec</i>-Alkyl-3-Substituted Indoles
作者:Mark C. Dobish、Jeffrey N. Johnston
DOI:10.1021/ol1025712
日期:2010.12.17
A Brønsted base-catalyzed reaction of nitroalkanes with alkyl electrophiles provides indole heterocycles substituted at C3 bearing a sec-alkyl group with good enantioselectivity (up to 90% ee). Denitration by hydrogenolysis provides a product with equally high ee. An indolenine intermediate is implicated in the addition step, and surprisingly, water cosolvent was found to have a beneficial effect in
硝基烷烃与烷基亲电试剂的布朗斯台德碱催化反应提供了在 C3 处取代的吲哚杂环,带有一个具有良好对映选择性(高达 90% ee)的仲烷基。通过氢解脱硝提供具有同样高 ee 的产品。在添加步骤中涉及吲哚中间体,令人惊讶的是,发现水共溶剂在该步骤中具有有益作用,导致使用 PBAM(一种双(脒)手性非外消旋碱)消除/对映选择性添加的一锅法。
Brønsted Acid-Promoted Cyclodimerization of Indolyl Ketones: Construction of Indole Fused-Oxabicyclo[3.3.1]nonane and -Cyclooctatetraene Ring Systems
A Brønsted acid-promoted cyclodimerization of C(3)-, C(2)-, or N(1)-substituted indole ketone derivatives is described. A wide range of structurally diverse bisindole fused-9-oxabicyclo[3.3.1]nonane and bisindole fused-cyclooctatetraene (COT) derivatives can be prepared in good to high yields with high efficiency.
Variant G74C of arylmalonatedecarboxylase (AMDase) from Bordatella bronchoseptica has a unique racemising activity towards profens. By protein engineering, variant G74C/V43A with a 20‐fold shift towards promiscuous racemisation was obtained, based on a reduced activity in the decarboxylation reaction and a two‐fold increase in the racemisation activity. The mutant showed an extended substrate range