Total synthesis of Palau-amine

Abstract

Palau-amine has received a great deal of attention in the past two decades as an attractive synthetic target by virtue of its intriguing molecular architecture and significant immunosuppressive activity. Here, we report the total synthesis of Palau-amine characterized by the Hg(OTf)2- catalyzed construction of tetra-substituted carbon center at the C16 position and the construction of an ABDE tetracyclic ring core including a trans-bicylo[3.3.0]octane skeleton at a middle stage of total synthesis. The ABDE tetracyclic ring core is constructed by a cascade reaction of a cleavage of the N-N bond, including simultaneous formation of imine, the addition of amide anion to the resulting imine (D-ring formation), and the condensation of pyrrole with methyl ester (B-ring formation) in a single step. The present synthetic route has the potential to help elucidate a pharmacophore as well as the mechanistic details of immunosuppressive activity Palau-amine has received a great deal of attention in the past two decades as an attractive synthetic target by virtue of its intriguing molecular architecture and significant immunosuppressive activity. Here, we report the total synthesis of Palau-amine characterized by the Hg(OTf)2-catalyzed construction of tetra-substituted carbon center at the C16 position and the construction of an ABDE tetracyclic ring core including a trans-bicylo[3.3.0]octane skeleton at a middle stage of total synthesis. The ABDE tetracyclic ring core is constructed by a cascade reaction of a cleavage of the N-N bond, including simultaneous formation of imine, the addition of amide anion to the resulting imine (D-ring formation), and the condensation of pyrrole with methyl ester (B-ring formation) in a single step. The present synthetic route has the potential to help elucidate a pharmacophore as well as the mechanistic details of immunosuppressive activity.