Reduction of sugar lactones to hemiacetals with lithium triethylborohydride

Reduction of ribono-1,4-lactones and gulono-1,4-lactone as well as ribono-1,5-lactone and glucono-1,5-lactones with LTBH (1.2 equiv.) in CH2Cl2 at 0 °C for 30 min provided the corresponding pentose or hexose hemiacetals in high yields. Commonly used in carbohydrate chemistry protecting groups such as trityl, benzyl, silyl, acetals and to some extent acyls are compatible with this reduction. [Display omitted] •Lithium triethylborohydride reduces lactones to pentose or hexose hemiacetals.•Reduction is higher yielding when lactone has a larger number of hydroxyl groups.•Reduction is more efficient in CH2Cl2 solution.•Reduction is compatible with protecting groups commonly used in sugar chemistry.