作者:Katarzyna Borsuk、Arkadiusz Kazimierski、Jolanta Solecka、Zofia Urbańczyk-Lipkowska、Marek Chmielewski
DOI:10.1016/s0008-6215(02)00139-8
日期:2002.11
The [2 + 2] cycloaddition of chlorosulfonyl isocyanate to (Z)-4-O-propenyl ethers 16, 17, 29 and 30 proceeds with an excellent stereoselectivity in the case of ether 16 and with moderate stereoselectivity in remaining cases. Adducts were transformed into corresponding oxacephams: 37 in the first case, a mixture of 37/40 in the second and third case, and a mixture of 50/51 in the last case. In all instances
氯磺酰基异氰酸酯与(Z)-4-O-丙烯基醚16、17、29和30的[2 + 2]环加成反应在醚16的情况下具有出色的立体选择性,在其余情况下则具有中等的立体选择性。加合物被转化为相应的乙草胺:第一种情况为37,第二种和第三种情况为37/40的混合物,最后一种情况为50/51的混合物。在所有情况下,除了烯烃的硅烷侧以外,都占主导地位。桥头碳C-5a上具有相反R-构型的乙草胺41和52可以通过基于4-乙烯基氧氮杂环丁烷-2-one中的氮被保护的6-O-三氟甲磺酸酯24或25烷基化的替代方法获得,然后通过乙烯基氧基的分子内置换实现环化。化合物37、40、41、50,