Biomolecules

Concept:The artificial sweetener $\mathbf{X}$ is sucralose. It is formed by an $\alpha$‑1,2‑glycosidic linkage between 4‑chloro‑4‑deoxy‑$\alpha$‑D‑galactose (pyranose form) and 1,6‑dichloro‑1,6‑dideoxy‑$\beta$‑D‑fructose (furanose form).Explanation:Step 1: Identify the galactose derivative. In D‑galactose, the $\mathrm{OH}$ at $\mathrm{C}$‑4 is replaced by chlorine ($\mathrm{Cl}$).Step 2: Identify the fructose derivative. In D‑fructose, the $\mathrm{OH}$ groups at $\mathrm{C}$‑1 and $\mathrm{C}$‑6 are replaced by chlorine atoms.Step 3: The linkage is between the anomeric carbon of galactose ($\mathrm{C}$‑1, $\alpha$ configuration) and the anomeric carbon of fructose ($\mathrm{C}$‑2, $\beta$ configuration). This is the same glycosidic bond as in sucrose.Step 4: Among the given options, look for a structure where:• The galactose ring (pyranose) has $\mathrm{Cl}$ at $\mathrm{C}$‑4, and $\mathrm{OH}$ groups at $\mathrm{C}$‑2, $\mathrm{C}$‑3, $\mathrm{C}$‑6 (all equatorial except $\mathrm{C}$‑4 is axial with $\mathrm{Cl}$).• The fructose ring (furanose) has $\mathrm{Cl}$ at $\mathrm{C}$‑1 and $\mathrm{C}$‑6, and $\mathrm{OH}$ at $\mathrm{C}$‑3, $\mathrm{C}$‑4 (both oriented for $\beta$‑D‑fructofuranose).• The linkage is $\alpha$‑1,2: the $\mathrm{C}$‑1 of galactose (with $\alpha$ configuration) is connected to $\mathrm{C}$‑2 of fructose (with $\beta$ configuration).Step 5: Check the provided image options. Option A shows exactly these features: galactose unit with $\mathrm{Cl}$ at $\mathrm{C}$‑4, fructose unit with $\mathrm{Cl}$ at $\mathrm{C}$‑1 and $\mathrm{C}$‑6, and the correct $\alpha$‑1,2 linkage.Answer:Option A.