问题
多项选择题
紫杉醇的结构特点和性质包括（）
A.含有N原子，具有碱性
B.含有酯键，对碱不稳定
C.含有苷键，对酸不稳定
D.容易还原，丧失活性
E.含有环氧丙烷环，具有抗癌活性
答案
参考答案：B, E
解析：
注意紫杉醇含有的N原子处于酰胺状态，不显碱性；紫杉醇结构中无苷键，对酸相对稳定；紫杉醇可与MnO2发生氧化反应，且不易还原。
搜题请搜索小程序“爱下问搜题”
紫杉醇的结构特点和性质包括（）
A.含有N原子，具有碱性
B.含有酯键，对碱不稳定
C.含有苷键，对酸不稳定
D.容易还原，丧失活性
E.含有环氧丙烷环，具有抗癌活性
参考答案：B, E
解析：
注意紫杉醇含有的N原子处于酰胺状态，不显碱性；紫杉醇结构中无苷键，对酸相对稳定；紫杉醇可与MnO2发生氧化反应，且不易还原。
| 完形填空。 | ||||
| It was already late when we set out for the next town, 1 according to the map was about fifteen miles away on the other side of the 2 . There we felt 3 that we would find a bed 4 the night. Darkness fell soon after we left the village, but luckily we met 5 as we drove fast along the narrow winding road that 6 the hills. As we climbed 7 , it became colder and rain began to fall, 8 it difficult at times to see the road. I asked John, my companion, to drive more 9 . After we had traveled for about twenty miles, there was still no sign of the town which was 10 on the map. We were beginning to get 11 . Then without warning the car stopped. A quick 12 showed that we had run out of petrol (汽油). Although we had little food with us, we decided to 13 the night in the car. Our meal was soon over. I tried to go to sleep at once, 14 John, who was a 15 sleeper, got out of the car after a few minutes and went for a walk 16 the hills. Soon he came back. From the top of the hill he had seen, in the valley below, the 17 of the town we were looking for. We at once unloaded (卸) all our luggage (行李) and with a great effort (努力), 18 to push the car to the top of the hill. Then we went back to the luggage, loaded the car again and set off down the hill. 19 . less than a quarter of an hour we were in the town, where we found a 20 quite easily. | ||||
|