Complex sentence: An aldose-ketose isomerization of 2 forms dihydroxyketone 3 with can react with 2 to form ribulose 4 and through another isomerization ribose 5 or with formaldehyde to tetrulose 6 and then aldoltetrose 7.
Split into simpler sentences: An aldose-ketose isomerization of 2 forms dihydroxyketone 3 which can react with 2 to form ribulose 4, and through another isomerization ribose 5. Molecule 3 also can react with formaldehyde to produce tetrulose 6 and then aldoltetrose 7.