Short Protecting Group-free Syntheses of Camptothecin and 10-Hydroxycamptothecin Using Cascade Methodologies

A convergent protecting group-free total synthesis route of camptothecin and 10-hydroxycamptothecin has been developed in this work. Cascade oxidation of 3-(hydroxymethyl)furan-2(5H)-one and in situ intermolecular oxa Diels-Alder reaction with vinyl ether was developed and applied to construct the E-ring, and TMSCl-promoted cascade closure of the D-ring delivered the whole skeleton of the alkaloids in the total synthesis. The new short syntheses were advantageous with regard to step economy, low cost, easily available starting materials and reagents, and convenient operations.