The direct and catalytic kineticresolution of racemiccarboxylicacids bearing a Bronsted base such as O-protected alpha-hydroxy carboxylicacids and N-protected alpha-amino acids has been accomplished through an L-histidine-derived sulfonamide-induced enantioselective esterification reaction with tert-butyl alcohol for the first time. Highly asymmetric induction [S( k fast/ k slow) = up to 56] has
带有布朗斯台德碱的外消旋羧酸如O-保护的α-羟基羧酸和N-保护的α-氨基酸的直接和催化动力学拆分已通过叔胺的L-组氨酸衍生的磺酰胺诱导的对映选择性酯化反应完成。首次使用丁醇。通过分子内氢键相互作用,在手性催化剂和两种非对映体酰基铵盐之间的平衡下,实现了高度不对称诱导[S(k fast / k slow)=高达56]。
Access to Enantioenriched α-Amino Esters via Rhodium-Catalyzed 1,4-Addition/Enantioselective Protonation
Conjugate addition of potassiumtrifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected alpha-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol)
The asymmetric conjugateaddition of arylboronic acids to N-phthalimidodehydroalanine 1i catalyzed by Rh(I)/L1a enables the facile preparation of chiral functionalized phenylalanines. The reaction proceeds by a conjugateaddition and enantioselective protonation cascade, affording a rhodium enolate that undergoes re-face protonation. The reaction tolerates various arylboronic acids and can be used
Abstract The scope and limitations of guanidiniumylide mediated aziridinations from arylaldehydes yielding unactivated 3-arylaziridine-2-carboxylates, applicable to asymmetric synthesis, are discussed. The scope and limitations of guanidiniumylide mediated aziridinations from arylaldehydes yielding unactivated 3-arylaziridine-2-carboxylates, applicable to asymmetric synthesis, are discussed.