화학공학소재연구정보센터
Journal of the American Chemical Society, Vol.142, No.1, 589-597, 2020
Asymmetric Synthesis of alpha-Aminoboronates via Rhodium-Catalyzed Enantioselective C(sp(3))-H Borylation
alpha-Aminoboronic acids, isostructural boron analogues of alpha-amino acids, have received much attention because of the important biomedical applications implicated for compounds containing this structure. Additionally, the inherent versatility of alpha-aminoboronic acids as synthetic intermediates through diverse carbon-boron bond transformations makes the efficient synthesis of these compounds highly desirable. Here, we present a Rh-monophosphite chiral catalytic system that enables a highly efficient enantioselective borylation of N-adjacent C(sp(3))-H bonds for a range of substrate classes including 2-(N-alkylamino)heteroaryls and N-alkanoyl- or aroyl-based secondary or tertiary amides, some of which are pharmaceutical agents or related compounds. Various stereospecific transformations of the enantioenriched alpha-aminoboronates, including Suzuki-Miyaura coupling with aryl halides and the Rh-catalyzed reaction with an isocyanate derivative of alpha-amino acid, affording a new peptide chain elongation method, have been demonstrated. As a highlight of this work, the borylation protocol was successfully applied to the catalyst-controlled site-selective and stereoselective C(sp(3))-H borylation of an unprotected dipeptidic compound, allowing remarkably streamlined synthesis of the anti-cancer drug molecule bortezomib and offering a straightforward route for the synthesis of privileged molecular architectures.