Selective skeletal and peripheral editing of the pyridine moiety has broadly expanded the chemical space. While C-H functionalization at C2 and C4 positions are enabled by the inherent reactivity of this heteroarene, selective derivatization at the C3 position has long posed a significant challenge. Recently, based on a dearomatization-rearomatization sequence, involving Zincke imine intermediates, selective halogenation (-Br, -Cl, and -I) and isotopic labelling were accomplished. Here, we report a mild and regioselective method for C3-amination that relies on the photochemical reaction of Zincke imine with an amidyl radical generated from N-aminopyridinium salts. Mechanistic and theoretical studies indicate that radical intermediates are involved and explain the C3 regioselectivity of the reaction.

Carbasugars represent an important category of natural products possessing a broad spectrum of biological activities. Lots of effort has been done to develop gram scale synthesis. We are presenting a new approach to gram scale synthesis of the carbasugar skeleton via intramolecular seleno-Michael/aldol reaction. The proposed strategy gave gram amounts of 6-hydroxy shikimic ester in a tandem process in 36% overall yield starting from D-lyxose. We have attempted to demonstrate the synthetic utility of 6-hydroxyshikimic acid derivatives by covering the important synthetic modifications and related applications, namely synthesis of protected (−)-gabosine E, (−)-MK7606, (−)-valienamine and finally unprotected methyl (−)-shikimate.

Selective skeletal and peripheral editing of the pyridine moiety broadly expanded the chemical space. While CH functionalizations at the positions C2 and C4 are enabled by the inherent reactivity of this heteroarene, selective derivatization at C3 has long posed a significant challenge. Recently, based on dearomatization-rearomatization sequence, involving Zincke imine intermediates, selective halogenation (-Br, -Cl, -I) and isotopic labelling was accomplished. Here, we report a mild and regioselective method for C3 amination that relies on the photochemical reaction of Zincke imine with an amidyl radical generated from N-aminopyridinium salts. Mechanistic and theoretical studies confirmed radical intermediates involved and explains C-3 regioselectivity of the reaction.

Simple and efficient carbasugar synthesis from d-aldopentoses via temporary protection of the hydroxyl moieties with TMS groups followed by consecutive intramolecular tandem Michael/aldol cyclisation.