The reactivity of Δ3- and Δ2-3-bromomethylcephems toward carboxylate nucleophiles has been studied. The Δ3-bromomethylcephem 1, less reactive than the Δ2-analogue 4, is converted in high yields into 3-acyl-oxymethyl-3-cephems 2a-d, generally with no isomerization of the double bond, only within a narrow range of conditions. In particular, the Δ3-7-aminocephalosporanic acid (7-ACA) derivative 2a has
Δ的反应3和Δ - 2朝向
羧酸的亲核试剂-3- bromomethylcephems进行了研究。的Δ 3 -bromomethylcephem 1,比Δ反应性较低的2 -analogue 4,被转换以高产率成3-酰基-氧甲基-3-头孢图2a-d ,一般用无异构化的双键的,仅在一个窄的范围内条件。特别地,Δ 3 -
7-氨基头孢烷酸(
7-ACA)衍
生物2a中已经获得如在91%产率的唯一产品通过处理1在
乙酸与
三乙基乙酸铵。