Abstract Delcosine (lucaconine) and its derivatives have all been shown to lose one mole of water, upon treatment with acetyl chloride, thus giving an anhydro compound. On the basis of the observation of the infrared spectra of anhydro-diacetyldelcosine, anhydro-oxodelcosine, and anhydro-1, 10-didehydro-oxodelcosine, it may be concluded that, in each compound, dehydration takes place between two tertiary hydroxyl groups, with a ketone carbonyl group being formed. Based on a tentative structure for delcosine proposed by Marion and his co-workers, structures for anhydro-diacetyldelcosine and anhydro-oxdelcosine are proposed. On hydrogenation over platinum in acetic acid, anhydro-diacetyldelcosine yielded anhydro-dihydro-diacetyl-delcosine. Anhydro-oxodelcosine was inert under these reduction conditions. On the basis of these experimental results, a possible mechanism of this novel hydrogenation is proposed. The ultraviolet spectrum of anhydro-diacetyldelcosine, with a new type of chromophore, is also shown.