CONH2 维生素B12 CH2 CH2 CH3 钴胺素 NH,CO-CH, CH2-CONH2 H:C A R CH2-CH2-CONH2 cyanocobalamine H.C Co CH NH,CO-CH2 CH: CH CO-CH>-CH2 CH3 CH:CH2-CH2-CONH2 NH CH2 N CH: CH-CH: 0=-0 0、 CH 0 OH HOH,C维生素B12 钴胺素 cyanocobalamine