C日 CH: CH: CH; CH CHC[CH=CH-CH一CH CH-CHCH-CH--CH CH; CH CH H C 紫外线 230-300nm HO 麦角固酵CH幻OH (argosterol) 柱生D2,岁角钙化醉C2sH4O1I (ergocaleiferol) CHa CHa CH, CH CH.CH-CH,-CH2--CH2-CH CH >CH-CHz-CH2-CH2-CH CH: CH 紫外线 230-300nm HO HO 7-脱氧胆固醇C2?H0H 维生素D,胆钙化醇C2,H,OH (7-dehydrocholesterol) (cholecalciferol)