De novo consecutive chemo/regioselective IBX mediated oxidation of andrographolide and its derivatives

Abstract

A new IBX mediated protocol for regio/chemoselective oxidation of andrographolide (1), a labdane diterpenoid isolated from Andrographis paniculata, is developed. After the initial success of this protocol with andrographolide (1) to provide 19-dehydroandrographolide (5) or 3,19-didehydroandrographolide (6) as major products, the procedure was further applied for the oxidation of hydroxyl functionality in andrographolide derivatives, namely 2, 3, 14, and 16. The process was equally suitable on scales of milligram to gram with ease. Deprotection of C-19-OTBDMS in compounds 15 and 18 was achieved using TBDMS-Cl in acetonitrile-water (8:2) system in good yields.

GRAPHICAL ABSTRACT

KEYWORDS:

• Andrographolide
• chemo/regioselective oxidation
• isolation
• labdane diterpenoid
• 2-Iodoxybenzoicacid (IBX)

Acknowledgments

The authors are thankful to the Department of Chemistry, CFRD Osmania University, Hyderabad, Telangana, India for providing facilities. We wish to thank UGC, New Delhi for the award of Senior Research Fellowship to Mokenapelli Sudhakar.

Additional information

Funding

We are grateful to UGC New Delhi for providing financially support under UGC-CPEPA (Centre with Potential Excellence in Medicinal Chemistry), project no. [8-2/2008(NS/PE)].