Enantioselective Access to Tetrahydroxanthones via Copper-bis(oxazoline)-Catalyzed [4 + 2] Cycloaddition

Area of Science:

• Organic Chemistry
• Asymmetric Catalysis

Background:

• Xanthone derivatives exhibit diverse biological activities.
• Efficient synthesis of chiral tetrahydroxanthones remains challenging.

Purpose of the Study:

• To develop a highly enantioselective method for tetrahydroxanthone synthesis.
• To explore the utility of tetrahydroxanthones as intermediates for bioactive molecules.

Main Methods:

• Copper-bis(oxazoline)-catalyzed [4+2] cycloaddition of chrom-4-one and Danishefsky's diene.
• Organotin-mediated quasi-Krapcho decarboxylation of β-keto ester cycloadducts.

Main Results:

• Achieved highly enantioselective synthesis of oxo-dihydroxanthone adducts with up to 98% yield and 89% ee.
• Developed a novel decarboxylation method for tetrahydroxanthone synthesis with stereochemical retention.
• Demonstrated tetrahydroxanthone as a versatile intermediate for saturated xanthones.

Conclusions:

• Established an efficient catalytic asymmetric route to valuable tetrahydroxanthone scaffolds.
• The developed methodology enables access to diverse, biologically relevant saturated xanthones.