Treatment of serine-derived N-(α-haloacetamido)dehydroalanine derivatives with tributyltin hydride in boiling benzene or toluene afforded pyroglutamates in 47–84% yield. The radical cyclisation reaction, which proceeded regioselectively in a disfavoured 5-endo-trig manner, was found to be most efficient when dichloro- and trichloroamides were employed as starting materials.
在沸腾的苯或
甲苯中用氢化三
丁基锡处理
丝氨酸衍生的N-(α-卤代乙酰胺基)脱氢丙
氨酸衍
生物可得到焦谷
氨酸,收率为47-84%。当以二
氯和三
氯酰胺为起始原料时,发现自由基环化反应以不利的5-内-trig方式区域选择性地进行,是最有效的。