Abstract: A class of novenl compounds represented by the formula (I) ##STR1## wherein R.sub.1 s are the same or different groups and each represents hydrogen atom or alkyl group having 1 to 4 carbon atoms; R.sub.2 is phenyl group, naphthyl group, or either phenyl or naphthyl substituted with at least one hydroxyl, alkyl having 1 to 4 carbon atoms or alkoxy having 1 to 4 carbon atoms; R.sub.3 is hydrogen atom, alkyl group having 1 to 4 carbon atoms or CH.sub.2 COOR.sub.4 group, in which R.sub.4 is hydrogen atom or alkyl group having 1 to 12 carbon atoms; n is 0 or 1, the configuration of 5-methylene group includes both E-isomer and Z-isomer, providing excepting the case wherein R.sub.1 is hydrogen or methyl, R.sub.2 is 3,5-di-t-butyl-4-hydroxyphenyl, R.sub.3 is hydrogen and n is 0 or pharmacologically acceptable salts thereof when R.sub.3 or R.sub.4 is hydrogen atomThe invention also concerns preparation methods thereof.