The title furan-oditerpenoid, known as fibaruretin B (systematic name: 2β,3α-dihy-droxy-2,3,7,8α-tetra-hydro-penianthic acid lactone), C(20)H(24)O(7), was isolated from the roots of Arcangelisia flava. The absolute configurations at positions 2, 3, 4, 4a, 7, 9, 10a and 10b of fibaruretin B are S, R, S, R, S, S, S and S, respectively. In the crystal structure, the mol-ecules are linked into infi...

PLAWALOGENS are a group of aldehydogenic substances widely distributed in nature in both the animal and plant kingdom. 4 Their chemical structure is that of a c&l(alk-l’enyl) ether of a 2-acyl-3glycerylphosphate (I) where R” may be derived from choline, ethanolamine or serine. Hydrogenation and acid hydrolysis8 yielded chimyl and batyl alcohols (IIa and IIb), while enzymic hydrolysis followed b...

Detailed practical and numerical information is provided for undertaking and evaluating absolute-structure and absolute-con®guration determinations. The interpretation of numerical values of x, the Flack [Acta Cryst. (1983), A39, 876± 881] parameter, and its standard uncertainty u are explained in terms of the inversion-distinguishing power. Moreover, the conditions to obtain reliable values of...