A compound of formula (I): ##STR1## in which R is optionally substituted phenyl; C.sub.3-8 cycloalkyl; C.sub.5-8 cycloalkenyl; C.sub.1-8 alkyl which may be straight or branched; C.sub.2-8 alkenyl which may be straight or branched; 5- or 6-membered heterocyclyl; or optionally substituted phenyl C.sub.1-4 alkyl, each of Y and Z, which may be the same or different, is oxygen or sulphur; and X is --CH.sub.2 -- or oxygen, a process for the preparation of such compounds and their use in human and veterinary medicine.
化合物的公式(I):##STR1## 其中R是可选取代的苯基;C.sub.3-8环烷基;C.sub.5-8环烯基;C.sub.1-8烷基,可以是直链或支链;C.sub.2-8烯基,可以是直链或支链;5-或6-成员杂环基;或可选取代的苯基C.sub.1-4烷基,Y和Z中的每一个,可以相同或不同,是氧或
硫;X是--CH.sub.2--或氧,一种制备这种化合物的方法以及它们在人类和兽医学中的应用。