From α‐1,2‐Anhydrosugars to C‐Glycosides: The Influence of Lewis Acids and Nucleophiles on the Stereochemistry
摘要:
Ring opening of the epoxide function in alpha-1,2-anhydrosugars with alkynyl zinc and titanium compounds proceeds with retention of configuration to afford alpha-C-alkynylglycosides in reasonable to good yields, while the use of the corresponding alkynyltrifluoroborates results in the formation alpha/beta mixtures. Vinyl nucleophiles predominantly afford alpha-products, whereas allyl and allenyl species almost exclusively yield beta-C-glycosides.
From α‐1,2‐Anhydrosugars to C‐Glycosides: The Influence of Lewis Acids and Nucleophiles on the Stereochemistry
摘要:
Ring opening of the epoxide function in alpha-1,2-anhydrosugars with alkynyl zinc and titanium compounds proceeds with retention of configuration to afford alpha-C-alkynylglycosides in reasonable to good yields, while the use of the corresponding alkynyltrifluoroborates results in the formation alpha/beta mixtures. Vinyl nucleophiles predominantly afford alpha-products, whereas allyl and allenyl species almost exclusively yield beta-C-glycosides.