The correct statement about the following disaccharide is

Options

A. Ring (A) is pyranose wiht `alpha`-glycosodoc link
B. Ring (A) is furanose with `alpha`-glycosidic link
C. Ring (B) is furanose with `alpha`- glycosidic link
D. Ring (B) is pyranose with `beta`-glyscosidic link.

Answer

A

Explanation

The monosaccharide represented by ring (A) is in the pyranose form since it has six atoms in the ring. Further , since the glycosidic carbon , i.e., `C_1` is towards right to the ring oxygen atom , therefore is belongs to D-series. In the D -series , if in the Haworth projection , the OH at the glycosidic carbon is below the ring , the glycosidic linkage is `alpha`. In other words , ring (A) is pyranose with `alpha`. glycosidic link and hence , option (a) is correct. The monosaccharide ring (B) is in the furanose form since it has five atoms therefore, it belongs to L-series , In the L-series it the OH at the glycosidic carbon is below the plane of the ring, the glycosidic linkage is `beta`. In other words, ring (B) is furanose with `beta`-glycosidic link and hence all the options (b), (c) and (d) are incorrect.