COOH(CH3 COhO COOH OH OCOCH3 乙酰水杨酸 COOH CHOH CooCH OH OH 水杨酸甲酯 COOH△ OH OHCOOH OH (CH3 CO) 2 O COOH OCOCH3 乙酰水杨酸 COOH OH CH3 OH COOCH3 OH 水杨酸甲酯 COOH OH OH