What are disclosed are compounds, useful as intermediates in the preparation of substituted penem compounds, of the formula ##STR1## wherein R is a removable esterifying group, R.sup.1 is lower alkyl or phenyl, R.sup.2 is hydrogen, lower alkyl, lower alkoxyalkyl, lower alkanoyloxyalkyl, or tri-lower alkylsilyloxyalkyl, and R.sub.a, R.sub.b, R.sub.c, R.sub.d, and R.sub.e are hydrogen, aliphatic cycloaliphatic hydrocarbon, free or esterified carboxyl, halo, or cyano, and any two of R.sub.a -R.sub.e, taken together, may form a cycloaliphatic ring.
所披露的化合物是替代型青霉烷化合物的中间体,其
化学式为##STR1## 其中R是可移除的酯化基团,R.sup.1是较低的烷基或苯基,R.sup.2是氢,较低的烷基,较低的烷氧烷基,较低的烷酰氧烷基或三较低烷基
硅氧烷基,而R.sub.a,R.sub.b,R.sub.c,R.sub.d和R.sub.e是氢,脂肪环烷基烃,自由或酯化羧基,卤素或
氰基,R.sub.a -R.sub.e中的任意两个,可以形成环状脂环烷基。