J.A. Lamberton

The influence of allylic oxygen on the CD of skew dienes

Abstract The CD of eight compounds each containing a conjugated diene system is discussed. In five of these the sign of the Cotton effect attributable to the lowest energy diene absorption band is at variance with the sign predicted by the rules relating sign to diene helicity. Each of the five compounds incorporates one or more oxygen substituents (hydroxyl, methoxyl, (1-carboxyvinyl)oxy) allylic to the diene system. If its is assumed that the helicity of the system OCCC may have a larger influence on the CD than the helicity of the diene system itself, these results are consistently explained.

Mearsine, a unique isoquinuclidine alkaloid: x-ray crystal structure of mearsine picrate

Abstract X-ray crystallography shows that mearsine, a minor alkaloid of the north Queensland plant Peripentadenia mearsii , has the novel isoquinuclidine structure 1, which permits charge transfer to take place between carbonyl and an azomethine group.

Alkaloids of peripentadenia mearsii. II: Minor bark alkaloids

Abstract The structures of the three minor alkaloids dinorperipentadenine, peripentamine and anhydroperipentamine have been established as til2 , til5 , and til6 respectively.

The absolute molecular structure of podopetaline

Abstract X-ray analysis of crystals of podopetaline hydrobromide, C 20 H 33 N 3 ·HBr, has established the absolute structure of podopetaline, an alkaloid from Podopetalum ormondii F. Muell. The crystals are orthorhombic, with unit cell dimensions, a = 6·619, b = 10·907, c = 26·806 A, Z = 4, the space group being P2 1 2 1 2 1 . The intensity data were measured with CuKα radiation on a single-crystal diffractometer. The crystal structure was solved by the heavy atom method and refined by difference and least-squares procedures to a final R index of 0·069 for the 849 observed terms. The absolute chirality has been defined by Bijvoets technique. Podopetaline (I) therefore provides an absolute chirality reference for Ormosia alkaloids which was not previously available.