Phytochemistry of the mopane, Colophospermum mopane

Area of Science:

• Phytochemistry
• Organic Chemistry
• Natural Products Chemistry

Background:

• The heartwood of Colophospermum mopane (mopane) is known for its complex polyphenolic composition.
• This includes various monomeric flavonoids, dimeric proanthocyanidins, and unique pyran ring-rearranged compounds.

Purpose of the Study:

• To elucidate the diverse and complex polyphenolic pool of mopane heartwood.
• To establish the constitution and absolute stereochemistry of conventional and rearranged di- and tri-meric proanthocyanidins.
• To understand the mechanisms of pyran ring rearrangement reactions.

Main Methods:

• Biomimetic-type syntheses were employed for structure elucidation.
• Detailed analysis of interflavanyl bonding positions in proanthocyanidins.
• Investigation of pyran ring rearrangement mechanisms and stereochemistry.

Main Results:

• Identified a wide array of monomeric flavonoids, dimeric proanthocyanidins (proguibourtinidins, profisetinidins, etc.), and triflavanoids.
• Characterized functionalized tetrahydropyrano- and hexahydrodipyrano-chromenes (phlobatannins) arising from rearrangements.
• Established the structural diversity and stereochemistry of these compounds, influenced by 5-deoxy flavan-3-ols.

Conclusions:

• The polyphenolic composition of mopane heartwood is exceptionally diverse, featuring unique rearranged structures.
• Biomimetic synthesis and mechanistic studies were crucial for unambiguous structure determination.
• The study provides significant insights into the biosynthesis and chemical complexity of mopane polyphenols.