Terpenoids: I. The Constitution and Stereochemistry of Ceanothic Acid

Ceanothic acid, a substance previously isolated by Julian, Pikl, and Dawson (J. Am. Chem. Soc. 60, 77 (1938)), has been shown to be a triterpenoid related to the lupeol–betulin group, but in which ring A is five-membered. It has been degraded to the keto ester A norbetulonic acid methyl ester, a substance of defined constitution and stereochemistry. The hydroxyl and carboxyl groups attached to ring A have been shown by spectroscopic studies to be trans, the stereochemistry of ceanothic acid being that represented by (XII).