Radical Cyclization of Sugar-Derived β-(Alkynyloxy)acrylates: Synthesis of Novel Fused Ethers
摘要:
Tributyltin radical mediated cyclization of carbohydrate-derived beta-(alkynyloxy)acrylates leading to highly functionalized cis and trans-fused bicyclic ethers of various ring sizes is described. The efficacy of the radical cyclization is nicely illustrated in the iterative construction of a trans-fused tricyclic tetrahydropyran.
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.