Relationship between Picrotin and Picrotoxinin

Abstract

THE relationship between picrotin, C₁₅H₁₈O₇, and picrotoxinin, C₁₅H₁₆O₆, the two components of the molecular compound picrotoxin, has long been a matter for speculation. While picrotoxinin is unsaturated, picrotin is saturated; and there is some indirect evidence that the relationship may be that of an olefin to its (chemical) hydrate; but no direct dehydration of picrotin has hitherto been accomplished. This has now been achieved by heating picrotin under controlled conditions with oxalic acid. When the reaction mixture is dissolved in water and brominated, a mixture of substances is precipitated in small yield which may be separated with some difficulty into two main fractions, (a) and (b). When finally purified, (a) melts at 264° and shows no mixed melting point depression with an authentic sample of bromoneopicrotoxinin. The identity of the two specimens is further confirmed by a crystallographic study, for which we are indebted to Mr. J. J. Reed, petrologist to the Geological Survey, New Zealand Department of Scientific and Industrial Research. The descriptions of the two specimens are identical: (b) has not yet been obtained in a state of purity, but it appears to contain a bromo compound different from any previously described.