Transformations in carbohydrate chemistry part 1 -: 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(R), montmorillonite K-10, LiClO4 (0.07 M) in dichloromethane and Pd(PPh3)(4) as catalysts. Exclusive alpha or beta 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 alpha -methylene-delta -valerolactones in good yields in one step using m-CPBA in the presence of BF3. Et2O. (C) 2000 Elsevier Science Ltd. All rights reserved.