SYNTHESIS OF HIGHLY FUNCTIONALIZED BIOLOGICALLY ACTIVE TETRACYCLIC DITERPENOIDS FROM ENT-KAUR-16-EN-19-OIC ACID UNDER MODIFIED PRÉVOST-WOODWARD REACTION CONDITIONS

Abstract

A procedure has been developed for the synthesis of highly functionalized tetracyclic diterpenoids from natural ent-kaur-16-en-19-oic acid under modified Prévost–Woodward reaction conditions. The reaction follows an unusual pathway which leads mainly to bromination or rearrangement products. The transforma­tion of ent-kaur-16-en-19-oic acid afforded a mixture of (16ZE)-17-bromo-ent-kaur-16-en-19-oic, (15R,16E)-17-bromo-15-acetoxy-ent-kaur-16-en-19-oic, (16S)-17-bromo-16-acetoxy-ent-kaur-19-oic, (15S)-15-acetoxy-ent-kaur-16-en-19-oic, and (15S)-15-hydroxy-ent-kaur-16-en-19-oic acids, the latter two being reported previously. The newly syn­thesized compounds were evaluated for their cytotoxicity against two cancer cell lines, HeLa and BxPC-3.