Constitution of P h e l h d r a l . d-, I-, and dl (Synthetic)-Phellandric Acids.Further evidence for the accepted constitution of phellandral has been obtained. THE constitution of phellandrd (4-isopropyl-A~-cycZohexene-l-aldehyde, Al-tetrahydrocuminal) is a matter of interest, as the evidence on which the accepted structure rests (Schimmel, Semi-annual Reps., Oct./Nov., 1904, 90) cannot be regarded as a rigid proof. Additional support for this structure follows from the conversion of phellandric acid into hexahydrocuminic acid, the epimeric forms of which have already been characterised by Cooke and Macbeth (J., 1939, 1245). The 1 : 4 positions of the substituents in phellandral are thus established, and the position of the ethylene linkage is fixed by the synthesis of dl-PheZZandric acid from a-bromohexahydroc.minic acid, which is also now described.To complete the proof the resolution of the synthetic acid into antipodes identical with the active acids derived from d-and Lphellandral is required, but this has not yet been achieved. The conversion of the natural aldehydes into the corresponding active acids is conveniently brought about by oxidation with silver oxide.EXPERIMENTAL. d-Phellundvic A cid.-The spontaneous aerial oxidation of phellandral to phellandric acid is slow and gives rise to gummy products, so the change is better brought about by the action of silver oxide, following the method of DelCpine and Bonnet (Compt.
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