A compound of the formula: ##STR1## wherein Z.dbd.H, halo, C.sub.1 -C.sub.20 alkyl, cycloalkyl, lower alkoxy, alkoxycarbonyl, cyano, wherein thealkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups;R.dbd.C.sub.1 -C.sub.25 alkyl, cycloalkyl, ##STR2## or halo-lower-alkyl; each of which may be optionally substituted with halo, fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy, (CR.sub.1 R.sub.2).sub.p -(CR.sub.3 .dbd.CR.sub.4).sub.m Q, or (CR.sub.1 R.sub.2).sub.p --C.tbd.C-Q;R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently H, or lower-alkyl, optionally substituted with halo;x is 1-4;n is [1-5]1-4;m is 1-15;p is 1-20; andQ is H, lower-alkyl, lower-alkenyl, lower-alkynyl, lower-alkylene, aryl, these compounds are useful as X-ray contrast agents or aryl-lower alkyl.