New type of di-amino alcohol-catalyzed enantioselective crossed aldol reaction of acetaldehyde with isatins: A concise total synthesis of antitumor agents

An enantioselective crossed aldol reaction of isatin derivatives and acetaldehyde has been developed using a series of simple and novel di-amino alcohol-type catalysts, affording 3- substituted 3-hydroxyindolin-2-ones in high chemical yields (up to 95%) and optical purity (up to 92% ee). The synthetic potential of present protocol has been demonstrated by a concise, enantioselective, protecting group-free and transition metal-free total synthesis of tryptanthrin architecture antitumor and antiviral agents i.e phaitanthrin B and cephalanthrin A along with biologically active indolidine alkaloids i.e chimonamidine, donaxaridine and formal synthesis of CPC-1. The highly enantioselective outcome of this catalytic crossed aldol reaction was evaluated by calculating the Gibbs free energy of possible transition states.

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