The chemical constitution of carcinolipin.

1. The neutral portion of the molecule of carcinolipin was found to be cholesterol by comparison of mixed melting points with cholesterol, its dibromide and its acetate. 2. The fatty acid present in carcinolipin was subjected to oxidative degradation by chromic acid and permanganate. Butan-2-one was the main neutral degradation product resulting from both these procedures. A mixture of dibasic acids was obtained after the oxidation with chromic acid. Permanganate oxidation yielded a complete homologous series of branched-chain C(5)-C(17) fatty acids. 3. The mass spectrum of the acid was characteristic for a saturated C(17) acid. The alcohol prepared by lithium aluminium hydride reduction of the original acid showed a mass spectrum typical for an anteiso compound. 4. Comparison of mixed melting points, gas-liquid-chromatographic behaviour and mass spectra of the fatty acid isolated from carcinolipin with an authentic sample of 14-methylhexadecanoic acid demonstrated the identity of these compounds. Cholesterol esters synthesized from authentic cholesterol and the fatty acid isolated from carcinolipin or synthetic 14-methylhexadecanoic acid showed an identical stimulating effect on the incorporation of labelled algal-protein hydrolysate into rat liver transfer RNA in vitro. 5. Mass spectra, results of oxidative degradations and comparisons with an authentic sample, as well as biological activity of the synthetic cholesterol 14-methylhexadecanoate, provided good evidence that carcinolipin is cholesterol (+)-14-methylhexadecanoate.