The acid-catalysed dehydration of 13α-Substituted-13β-methylpodocarpan-8β-ols

Abstract

Acid-catalysed dehydration of each of the 8β-hydroxy compounds (1a) and (1b) gives initially the Δ⁷ (3), Δ⁸⁽¹⁴⁾ (4) and Δ⁸ (5) olefins. After extended reaction times the rearranged 8α-Δ⁵(16), 8α-Δ⁵⁽¹⁰⁾ (14) and 8β- Δ⁵⁽¹⁰⁾ (15) olefins are major products; the 8β-Δ⁵⁽¹⁰⁾ olefin (15) is the only significant product of long-term acid treatment of the 8β-alcohol (1b) or of the other olefins (3b), (4b), (5b), (14b) and (16b).