one or more substituents e g hydroxy groups halogen atoms or trifluoromethyl groups we prefer that p should be 1 and that r 3 should represent an alkyl group most preferably methyl ethyl propyl isopropyl butyl or hexyl an optionally substituted benzyl group most preferably benzyl 4 methylbenzyl 4 methoxybenzyl or 4 chlorobenzyl or an optionally substituted phenacyl group most preferably phenacyl 4 methylphenacyl 4 methoxyphenacyl or 4 bromophenacyl representative examples of compounds of the invention are given in the following list the above compounds all exist as both u03b4 4 and u03b4 4a isomers and may be provided as individual isomers or as mixtures thereof of the compounds of the invention the most preferred are the sodium salts i e compounds nos 3 and 4 of the above list the compounds of the invention have been found to inhibit cholesterol biosynthesis in the liver and thus may be used for the treatment of hypercholesteraemia or the prevention of arteriosclerosis in the same way as are the compounds disclosed in u s patent application ser no 256 243 filed 21st april 1981 now u s pat no 4 361 515 or u s patent application ser no 270 846 filed 5th june 1981 now u s pat no 4 346 227 and the compounds of the invention show an ability to inhibit cholesterol biosynthesis which is broadly comparable with that exhibited by the compounds disclosed in these two u s patent applications however the compounds of the invention have the significant advantage over the compounds disclosed in the aforementioned u s patent specifications that they are metabolised with much greater difficulty after administration and are thus less readily deactivated this means that the activity of the compounds of the invention is more.