Synthesis of C-2 Methylene O- and C-Glycosides and Sugar Derived α-Methylene-δ-valerolactones from C-2-Acetoxymethyl Glycals

C-2-Methylene O- and C-glycosides are readily synthesized from C-2-acetoxymethyl glycals using Nafion-H®, montmorillonite K-10, LiClO4 (0.07 M) in dichloromethane and Pd(PPh3)4 as catalysts. Exclusive α or β selectivities have been observed with various primary, secondary and tertiary alcohols, phenols and diethyl malonate. Further, C-2-acetoxymethyl glycals are also converted into corresponding α-methylene-δ-valerolactones in good yields in one step using m-CPBA in the presence of BF3·Et2O.