CH2OH CH2OH CH2OH C=0 HO-C OH HO-C-H HO-C-H HO-C-H H-C-OH H-C-OH or H-C-OH H-C-OH H-C- H-C- CH2OH CH2OH CH2OH D-Fructose B-D-Fructose a-D-Fructose 果糖的环形和异头结构D-Fructose β-D-Fructose α-D-Fructose 果糖的环形和异头结构 CH2OH O CH2OH C HO C H H C OH H C OH O CH2OH C HO C H H C OH H C CH2OH CH2OH H C HO H C OH HO C H C OH CH2OH O or