Chapter 10 The Amaryllidaceae Alkaloids

Abstract

Publisher Summary Several notable advances have been made in the analytical aspects of alkaloids. Most alkaloids have proven amenable to separation and identification by gas phase, paper, and thin-layer chromatography. Recent structural studies have provided two new types of alkaloids based on the 6,11-methanomorphanthridine and the biphenyl ring systems. However, the structures of most new alkaloids are merely substitutional variants within the ring systems. Although the structures of most major alkaloids have been established with certainty by chemical methods, infrared (IR)-, nuclear magnetic resonance (NMR)-, and mass spectroscopy have proved invaluable in confirming many structures and in exploring subtle points of stereochemistry. These same instruments offer the greatest hope for the structural elucidation of the numerous minor components. Many of the alkaloids that have been reported with meager or ambiguous experimental data are discussed in this chapter. It provides many structures of known relative and absolute configuration. X-ray data have now provided the absolute configurations of galanthamine and lycorine. Because of numerous interconversions between the lycorine and lycorenine types of alkaloids, the absolute configurations of many of the latter also are known with certainty. The absolute configuration of the alkaloids in the chemically interrelated crinine, tazettine, and montanine groups rests on the applicability of Mills' rule for allylic alcohols. The assignments of absolute configuration within these three alkaloidal systems by this rule are consistent with the known chemical correlations.