HOOKER : LOMATIOL (HYDROXYISOLAPACHOL). 138 1 LXXXVII1.-Lomatiol (Hydroxyisolapachol). By S m u m C. HOOKER, IN an interesting paper published last year (Trans., 1895, 784), Rennie gives the resnlts of his study of the yellow colouring matter which surrounds the nuclei of the seeds of two species of the Australian lomatia, and expresses the belief that the compound is a, hydroxylapachol, recording, in support of his conclusions, its conver- sion into hydroxy-P-lapachone.* Dr. Rennic has very kindly for- warded to me small specimens of his substances, and a careful comparison enables me to confirm his conclusions, and to state positively that the hydroxy-P-lapachone received is identical with that previously obtained by me (Trans., 1892, 649) from dihydroxy- h ydrolapachol. Having established the intimate relation existing between lapachol and the lomatia colouring matter, Dr.Rennie suggested formuls for the various substances obtained in the course of his work, which were based upon what appeared to be at that time the most probable structure of lapachol. Since, however, it is now necessary to modify this (see preceding paper), corresponding changes must also be made in the structure of the lomatia compounds. To prevent confusion with the hydroxyisolapachol described in the preceding paper, I shall refer to the lomatia colouring matter as lomatiol. Since the formula of hydroxy-/3-lapachone must now undoubtedly be written O p - 1 and further, since lomatiol, C15H110d, when submitted to the action of concentrated sulphuric acid, appears to be first converted into an anhydride, C,,H,,Os, which, by the absorption of 1 mol.of water, becomes hydroxy-P-lapachone, it is evident that. the hydroxyl in the f The melting point of hydroxy-B-lnpachone previously given by me is, as Renuie ha3 surmised, too low. 4 2 21382 HOOKER : LOMATIOL (HYDROXYISOLAPACHOL). side chain of lomatiol must be attached to the same carbon atom, as are also the two methyl groups. The hydroxyl group being thus located, there is only one position possible for the double bond, namely, that between the first and second carbon atoms of the chain. We have therefore the following changes as the result of the action of conoentrated sulphuric acid. Lometiol, C15H1404* It is thus apparent not of lapachol itself. 0-, Dehydrolepachone, C15H1203. 0 Hy dror y-B-lapachone.that lomatiol is a derivative of isolapachol, C1SH1404* and By the action of a boiling aqueous solution of caustic potash on dehydrolapachone, the regeneration of lomatiol might be expected, but Rennie states that an isomeric hydroxylapachol, which may be called isolomatiol, is formed instead. This can probably be best explained by the supposition that the latter and lomatiol are stereo- isomeric compounds, and that lomatiol does not pass directly into dehydrolapachone, but is first converted into ieolomatiol, a. change which may be regarded as a necessary preliminaq to the anhydride formation. Thus H O*CioH,( 0,) *C *H H*C * C I o H 4 ( 0,) *OH II CH3 II CH3 H~C-CLOH - H.CG/OH ‘CH, \CH, Lomatiol. Isolomatiol. After making due allowance for the change in the structure of lapachol, the above interpretation of the facts which Rennie’s experi- ments have furnished differs in some minor details from that suggested by Rennie himself. The want of material unfortunately renders impossible an experimental inquiry as t o its Talue at the present time; the existence, however, of substances in the lapachol group isomeric with, but entirely distinct from, the lomatiol compounds, reduces the number of formula which might otherwise have been available, and gives weight to the relations suggested above.RUHEMANN AND WOLF: THE &KETONIC ACIDS, 1383 As Dr. Rennie has very kindly left to me the further investigation of these compounds, and has promised his assistance in securing the necessary material, I shall hope to return to the consideration of this subject in the future. Philadelphia, U.8. A.