A new germacranolide from Ageratina vernalis

Area of Science:

• Natural Product Chemistry
• Phytochemistry
• Organic Chemistry

Background:

• Ageratina species are known sources of bioactive compounds.
• Germacranolides and guaianolides are important classes of sesquiterpenoids with diverse biological activities.

Purpose of the Study:

• To isolate and characterize chemical constituents from the aerial parts of Ageratina vernalis.
• To explore the chemical transformation of isolated compounds.

Main Methods:

• Phytochemical investigation involving extraction and isolation techniques.
• Structure elucidation using spectroscopic methods including 1D and 2D NMR.
• Determination of absolute configurations using vibrational circular dichroism (VCD) spectroscopy.
• Acid-catalyzed cyclization reaction.

Main Results:

• Isolation of a new germacranolide, 1,10-epoxydeltoidin A (3).
• Identification of known compounds: hopane-6α,22-diol (1), deltoidin A (2), and 15-hydroxydeltoidin A (4).
• Synthesis of a new guaianolide (5) via pTsOH catalyzed cyclization of deltoidin A (2).
• Complete assignment of 1D and 2D NMR data for compounds 2-5.
• Determination of the absolute configurations of compounds 2, 4, and 5 using VCD spectroscopy.

Conclusions:

• The study expands the phytochemical knowledge of Ageratina vernalis by identifying novel and known sesquiterpenoids.
• The chemical modification demonstrated a pathway to access different sesquiterpenoid skeletons.
• Spectroscopic techniques, particularly VCD and NMR, were crucial for comprehensive structure determination.