Studies of cholesterol biosynthesis. 2. Distribution of acetone carbon in the ring structure

The same sequence of reactions as that described in the previous paragraph was carried out on pure recrystallized s-amino-n-heptanoic lactam, m.p. 910.Liquid-vapour partition chromatography (James & Martin, 1952) of the final mixture of fatty acids showed them to be present in the following molar proportions: n-valeric and acetic 99 % each, n-butyric and propionic 1 % each.In a similar series, the mother liquor from the first light petroleum crystallization of the Schmidt reaction mixture was taken, and the crude product (m.p. 58-65°), obtained by evaporating to dryness in vacuo, was used as starting material.The following molar proportions of fatty acids were finally detected: n-valeric and acetic 67 % each, n-butyric and propionic 33 % each.SUMMARY 1.A new method for the degradation of the ring structure of cholesterol is described.This involves the opening of ring B by oxidation and the splitting off of ring A as 2-methylcyclohexanone by pyro- lysis.2. Carbon atom 6 is obtained as carbon dioxide from the decarboxylation of 5:6-8ecocholestan-5:7dion-6-oic acid.From the further degradation of 2-methylcyclohexanone, carbon atoms 4 and 5 of cholesterol are obtained as acetic acid and carbon atoms 19, 10, 1, 2 and 3 as valeric acid; by a side reaction carbons 19, 10 and 5 were isolated as propionic acid accompanied by carbons 4, 3, 2 and 1 as butyric acid.3. Two different ways are described for carrying out the early stages of the degradation: the first method starts from cholesterol ozonide, the second and more efficient method from cholest-5-ene.