In an attempt to convert β-(9-phenanthryl)-propionic acid to its 9:10-dihydride by high pressure hydrogenation, only β-(9-s-octahydrophenanthryl)propionic acid was obtained. β-(9-Phenanthryl)propionic acid was prepared, by standard reactions, from 9-chloromethyl phenantbrene, which was itself obtained by chloromethylation of phenanthrene. A small amount of 1-chloromethylphenanthrene was also isolated from this reaction. Cyclisation of β-(1:2:3:4-tetrahydro-9-phenanthryl) propionic acid has been found to give 3'-keto-9:10-cyclo-penteno-1:2:3:4-tetrahydrophenanthrene . In another attempt to synthesise 10-methoxy-3:4-benzpyrene, l-methoxyperinaphthan-7-one was condensed with o-chlorophenylmagnesium bromide to give I-methoxy-7-(o-chloro-phenyl) perinaphthan-7 ol. Attempted dehydration of this carbinol resulted in demethylation as well, with formation of 4-(o-chlorophenyl) perinaphthan -7- one. The mechanism of this reaction is discussed with regard to bond Mobility in the perinaphthene system. 1-Methoxyperinaphthan-7-one was prepared by cyclisation of β-(2-methoxy-l-naphthyl)-propionic acid. The latter compound was obtained from l-chloromethyl-2-methoxynaphthalene by the malonic ester synthesis. It has been found by other workers in this Department that β-(9-s-octahydroanthranyl)propionic acid under- goes rearrangement and cyclisation in presence of anhydrous hydrofluoric acid to give 1'-keto-9:10-cyclopenteno-3-octa-hydrophenanthrene. In an investigation of this rearrangement, the behaviour of several derivatives of s-octahydro-anthracene when treated with this reagent has been studied. A similar rearrangement has been observed in the case of l-(9-s-octahydroanthranyl) butyric acid, wiich is almost quantitatively converted to 4-ketododecahydrotriphenylene when treated with hydrofluoric acid at room temperature. All the other compounds tested were unaffected under these conditions. It seems likely that cyclisation of an acid side chain is concerned in these rearrangements of the octahydroanthracene nucleus, and that they are the first recorded examples of anew type of alkylbenzene isomerisation, brought about by displacement of an alkyl group by cyclisation of an acid chain into that position of the benzene ring. Several new derivatives of s-octahydroanthracene were prepared. The Friedel-Crafts reaction between s-octa-hydroanthracene and succinic anhydride, in carbon disulphide, was found to give β-(9-s-octahydrophenanthroyl)propionic acid. In tetrachlorethane, a mixture of this and β-(9-s-octahydroanthranoyl)propionic acid was obtained. Attempts to repeat the synthesis of santonin described by Paranjape, Phalnikar, Bhide and Nargund (77) have been unsuccessful. Treatment of ethyl Δ2-cyclohexen-1-one-3-methyl malonate and ethyl α-(Δ2-cyclohexen-l-one-3)propionate with 6N sulphuric acid In 50% aqueous alcohol did not yield the lactone of α-(2-hydroxy-3-ketocyclohexyl)propionic acid as they state. In every case the completely decarboxylated product 3-ethyl-Δ2-cyclohexene was obtained.