Platinum catalyzed 7-endo cyclization of internal alkynyl amides and its application to synthesis of the caprazamycin core.

The scope and limitations of the platinum catalyzed 7-endo cyclization of internal alkynyl amides were investigated. Substitution of the alkyne with an aryl group gave better results, presumably because it stabilized the transition state. Applying the reaction to a secondary amide, the caprazamycin core was successfully synthesized from commercially available material in eight steps.

Synthetic study toward ecteinascidin 743: concise construction of the diazabicyclo[3.3.1]nonane skeleton and assembly of the pentacyclic core.

Synthesis of the pentacyclic core of ecteinascidin 743 is described. This synthesis features concise construction of the diazabicyclo[3.3.

Gold(I)-catalyzed tandem reactions initiated by hydroamination of alkynyl carbamates: application to the synthesis of nitidine.

As a convenient and direct synthesis of 1,2-dihydroisoquinolines, the gold(I)-catalyzed intramolecular hydroamination of (2-alkynyl)benzyl carbamates has been developed. The reaction with cationic gold(I) complex [AuCl(PPh(3))/AgNTf(2)] proceeded at room temperature, giving the desired 6-endo adducts. The addition of alcohol efficiently promoted the reaction, and the amount of the catalyst could be reduced to 1 mol %.