Synthesis of new A-conjugated Quinolone and Spiroindole Dammaranes by the Ozonolysis of 2,3-Indolodipterocarpol

Abstract

An one-step and efficient access to the new dammarane A-quinolones by ozonolysis of 2,3-indolodipterocarpol at 0°C through the 1,3-dipolar cycloaddition of ozone to the C2-C3 double bond of the triterpenoid core is reported. In the case of oxidation in AcOH, two spiroindoles were identified as a result of 1,2-cycloaddition of ozone to the C2-C3 double bond with following intramolecular rearrangements of 2,3-epoxy-intermediate. The structures of four new compounds were established by 1H, 13C NMR, COSY, NOSY, HMBC and HSQC analyses.