Synthesis of an ether-linked alkyl 5a-carba-β-D-glucoside, a 5a-carba-β-D-galactoside, a 2-acetamido-2-deoxy-5a-carba-β-D-glucoside, and an alkyl 5a′-carba-β-lactoside

For the purpose of providing biologically stable building blocks for the biocombinatorial synthesis using a living cell, some ether-linked alkyl 5a-carba-β-D-glycoside primers were prepared. The key step of the synthesis was coupling of 1-bromo-n-alkanes with the 1-OH unprotected derivatives of 5a-carba-sugar analogues of D-glucose, D-galactose, and 2-acetamido-2-deoxy-D-glucose (N-acetyl-D-glucosamine), in DMF in the presence of sodium hydride. Alternatively, alkyl carba-lactoside was synthesized by incorporation of a 5a-carba-β-D-galactose residue into the 4-position of dodecyl β-D-glucopyranoside. A strong and specific inhibition of β-galactosidase (K_i 0.67 μM, bovine liver) was found for dodecyl 5a-carba-β-D-galactopyranoside.