Carbon‐13 NMR spectra of some tetra‐ and pentacyclic triterpene methyl ethers

The carbon‐13 NMR spectra have been recorded for representatives of three previously unexamined classes of pentacyclic triterpenes—lupanes, fernanes and arboranes. In addition to the spectra of lupeol methyl ether, cylindrin and arundoin, the spectra of a number of other triterpene methyl ethers are also recorded. The effect of methyl ether formation on the shilding values for carbons in the 3β‐hydroxy‐4,4‐dimethyl‐ ring A system is defined.