14-Hydroxycaryophyllene 4,5-oxide — A new sesquiterpene fromBetula pubescens
A new sesquiterpene — 14-hydroxycaryophyllene 4,5-oxide — has been isolated from the unsaponifiable part of an ethereal extract of the leaves ofBetula pubescens, and its structure has been established on the basis of chemical and spectral characteristics.
Base-catalyzed intramolecular displacements on certain 1,2-epoxides
Intramolecular displacement by hydroxyl on the 1,2-epoxide group under basic or neutral conditions has been studied for seven of the stereoisomeric 1,2-diols derived by oxidation of the exocyclic double bond of 1. In six of the examples (the seventh is ambiguous) the single or largely predominant product is that one of the less strained cis-fused isomers which has the fewer unfavourable steric interactions leading to it, without regard to whether the displacement occurs at the secondary or tertiary epoxide carbon.
A new type of germacranolide from Vernonia species
From several South African Vernonia species, a considerable number of sesquiterpene lactones has been isolated. Together with known compounds, seven members of a new type with an enol lactone ring have been found, their structures being elucidated by spectroscopic methods and some chemical transformations. Furthermore two new derivatives of costunolide are present in two species, and three new guaianolides have been found. From some species, however, no lactones could be isolated. Together with a new bisabolene derivative, a known eremophilone has been isolated, probably for the first time, from a member of the tribe Vernonieae.