Abstract: Novel 3-formyl-4-methyl-pentanoic acid derivatives of the formula ##STR1## wherein Y is an aromatic group, R.sub.2 and R.sub.3 are individually alkyl of 1 to 4 carbon atoms or taken together with the carbon atom to which they are attached form a carbon homocycle of 3 to 6 carbon atoms, the Rs are alkyl of 1 to 6 carbon atoms or together form a polymethylene of 2 to 3 carbon atoms and Z' is selected from the group consisting of --COOH and Z and Z is selected from the group consisting of cyano and --COOR.sub.1 wherein R.sub.1 is alkyl of 1 to 6 carbon atoms and their preparation which are useful for the preparation of 3-formyl-4-R.sub.2 R.sub.3 -but-3-ene-1-oic acid which is an intermediate for the preparation of a compound of the formula ##STR2## wherein R.sub.4 is hydrogen or the remainder of an alcohol of the formula R.sub.1 OH by the process of copending, commonly assigned U.S. patent application Ser. No. 153,338 filed May 27, 1980.

Abstract: A compound of the formula ##STR1## or a pharmaceutically acceptable salt thereof, wherein: G is hydroxymethylene or carbonyl;R is hydrogen or alkanoyl having from one to seven carbon atoms;R.sub.1 and R.sub.2 are each methyl or ethyl;R.sub.3 is an alkyl of from five to seven carbon atoms;m is 0 or 1; andn is 1, 2 or 3.A preferred compound is one in which m is zero, n is one or G is hydroxymethylene. Also preferred are compounds in which R.sub.1 and R.sub.2 are methyl. Additional preferred compounds include those where R is hydrogen or acetyl. A preferred compound is Z-3-(4'-(dimethyl-n-hexylsilyl)-2'-hydroxyphenyl)cyclohexanol.The invention further comprises pharmaceutical compositions containing these compounds. In accordance with the present invention, these compounds when administered in an effective amount to mammals are useful as CNS agents including analgesics, tranquilizers, sedatives, anticonvulsants, antidiarrheals, antiemetics and antianxiety agents.