Collect. Czech. Chem. Commun. 1985, 50, 114-131

Oxidation and epoxidation of 4,4-dimethyl-A-homo-5-cholesten-4a-ols

Helena Velgová and Jaroslav Zajíček

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6


Oxidation of four stereoisomeric 3-acetoxy-4,4-dimethyl-A-homo-5-cholesten-4a-ols I-IV with Sarett's and Jones's reagent was investigated. 4αβ-Hydroxy derivatives II and IV afforded corresponding enones V and XVI as the main products, while in the case of 4aα-hydroxy derivatives I and III the formation of 5β,6β-epoxides was observed both in the oxidation according to Jones and in the oxidation with the Sarett's reagent. The study of the stereochemistry of epoxidation of olefins I-IV and their derivatives showed that the epoxidation of the 5,6-double bond takes place preferentially from the β-side of the cyclic system. On the basis of 1H NMR data the preferred conformation of the seven-membered ring A in the allylic alcohols I-IV was determined; on its basis the effects leading to different behaviour of epimers I, III and II, IV during oxidation are discussed.