β-Oxy-α-diazo-carbonyl compounds. Part 6: Synthesis and reactivity of 3-deoxy-2-diazo-esters derived from monosaccharides. Applications in the synthesis of 2-C-alkyl-KDO analogues and related compounds

Reactions of 6-O-protected diazo derivatives 8, 9 and 10 with transition metals Rh(II) and Cu(II) under a variety of different conditions of solvents and temperatures, were studied in order to obtain 2-C-alkyl analogues of KDO. In fact, these types of products (11, 12) were obtained in good yields when Rh(II) was used as a catalyst in benzene. The interesting seven-membered ring products (13) were obtained only for 8 and 9, as single diastereoisomers and their formations were favored when Cu(II) catalysts were used.