Efficient synthesis of new N-alkyl-D-ribono-1,5-lactams from D-ribono-1,4-lactone

Abstract d -Ribono-1,4-lactone was treated with ethylamine in DMF to afford N -ethyl- d -ribonamide 9a in quantitative yield. Bromination of amide 9a by the system SOBr 2 in DMF or PPh 3 /CBr 4 in pyridine led, after acetylation, to epoxide 7 . However, treatment of amide 9a with acetyl bromide in dioxane followed by acetylation gave 2,3,4-tri- O -acetyl-5-bromo-5-deoxyl -N -ethyl- d -ribonamide 10a . Methanolysis of 10a , with sodium methoxide, afforded the N -ethyl- d -ribonolactam 11a in 51% overall yields. Using this method, N -butyl, N -hexyl, N -dodecyl, and N -benzyl- d -ribonolactams 11b – e were obtained in good yields (48–53%).