Biomolecules

L-isomer of tetrose \(\mathrm{X}\left(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{4}\right)\) gives positive Schiff's test and has two chiral carbons. On acetylation, '\(\mathrm{X}\)' yields triacetate. '\(\mathrm{X}\)' also undergoes following reactions

'\(\mathrm{X}\)' is