Alkene Epoxidations Mediated by Mn-Salen Macrocyclic Catalysts

Three new chiral Mn macrocycle catalysts containing 20 or 40 atoms in the macrocycle were synthetized and tested in the enantioselective epoxidation of cis-β-ethyl-styrene and 1,2-dihydronathalene. The effect of the presence of a binaphtol (BINOL) compound in the catalyst backbone has been evaluated, including by Density Functional Theory (DFT) calculations.

Enabling Highly (R)-Enantioselective Epoxidation of Styrene by Engineering Unique Non-Natural P450 Peroxygenases

Unlike the excellent (S)-enantioselective epoxidation of styrene performed by natural styrene monooxygenase (ee >99%), the (R)-enantioselective epoxidation of styrene has not yet achieved a comparable efficiency using natural or engineered...

An Alginate-Confined Peroxygenase-CLEA for Styrene Epoxidation

Oxyfunctionalisation reactions in neat substrate still pose a challenge for biocatalysis. Here, we report an alginate-confined peroxygenase-CLEA to catalyse the enantioselective epoxidation of cis-β-methylstyrene in a solvent-free reaction system achieving...

Concise asymmetric syntheses of streptazone A and abikoviromycin

Streptazone A and abikoviromycin are related alkaloids that both feature an unusual arrangement of reactive functionalities within an underlying compact tricyclic ring system. Here, we report a highly concise asymmetric synthesis of both natural products. The developed route first constructs another member of the streptazones, streptazone B1, using a rhodium-catalyzed distal selective allene-ynamide Pauson-Khand reaction as the key transformation. A regio- and enantioselective epoxidation under chiral phase-transfer catalytic conditions was then achieved to directly make streptazone A in 8 steps overall. A chemoselective, iridium-catalyzed reduction of the enaminone-system was employed to make abikoviromycin in one additional step. Studies of the intrinsic reactivity of streptazone A towards the cysteine mimic, <i>N</i>-acetylcysteamine, revealed unanticipated transformations, resulting in thiol conjugation to both the hindered tertiary carbon of the double allylic epoxide and in bis-thiol conjugation which may proceed via formation of a cyclopentadienone intermediate. With flexible access to these compounds, studies aimed to identify their direct biological targets are now possible.

Concise asymmetric syntheses of streptazone A and abikoviromycin

Streptazone A and abikoviromycin are related alkaloids that both feature an unusual arrangement of reactive functionalities within an underlying compact tricyclic ring system. Here, we report a highly concise asymmetric synthesis of both natural products. The developed route first constructs another member of the streptazones, streptazone B1, using a rhodium-catalyzed distal selective allene-ynamide Pauson-Khand reaction as the key transformation. A regio- and enantioselective epoxidation under chiral phase-transfer catalytic conditions was then achieved to directly make streptazone A in 8 steps overall. A chemoselective, iridium-catalyzed reduction of the enaminone-system was employed to make abikoviromycin in one additional step. Studies of the intrinsic reactivity of streptazone A towards the cysteine mimic, <i>N</i>-acetylcysteamine, revealed unanticipated transformations, resulting in thiol conjugation to both the hindered tertiary carbon of the double allylic epoxide and in bis-thiol conjugation which may proceed via formation of a cyclopentadienone intermediate. With flexible access to these compounds, studies aimed to identify their direct biological targets are now possible.