苄基氯

The synthetic route starts from penicillin G, peroxyacetic acid(8.5%) as Oxidizing Agent to get penicillin G sulfoxide; esterifided with p-nitrobenzyl bromine to synthesize penicillin G sulfoxide ester; we synthesize 3-exomethylenecepham sulfoxide ester with phthalimide potassium and 4A molecular sieve as acid scavenger to open the ring, SnCl_4 as catalyzation to close the ring. The yield is over 60%.

本研究采用的合成路线为：以青霉素G钾盐为原料，选用工业过氧化氢制备的过氧乙酸(22.3%)稀释至8.5%为氧化剂，氧化得青霉素亚砜；采用对硝基溴苄为酯化试剂，制备青霉素亚砜酯；以NCP(N-氯代邻苯二甲酰亚胺)为开环试剂，酞酰亚胺钾和4A型分子筛为酸清除剂，顺利开环；再经无水SnCl_4催化闭环得3-环外亚甲基头孢亚砜酯，最终产率在60%以上。

Now, however, all children continue in "comprehensive" schools, and the eleven-plus determines which courses of study the child will follow.

然而现在，所有的孩子都要在综合学校继续学习，所以这次考试只是决定他们将要学习哪些课程。

Cultivatable land , and led to a general recognition that development must not be carried at the cost of agriculture .

城区的迅速扩大在很多情况下侵占了宝贵的可耕地，使人们普遍认识到发展不能以牺牲农业为代价。