Aspidospermidine, 1,2-dehydro

Furanones are a class of chiral dienophiles very reactive in thermal cycloadditions. For example, (5R)-5-(/-menthyloxy)-2-(5H)-furanone (28) underwent Diels Alder reaction with cyclopentadiene (21) with complete re-face-selectivity (Equation 2.10), affording a cycloadduct which was used as a key intermediate in the synthesis of dehydro aspidospermidine [27]. 

The indolenine corresponding to aspidospermidine was also isolated (28,51a). It was denominated Alkaloid 280A [later named 1,2-dehydro-aspidospermidine (51)] and has structure IX. This compound had previously been obtained by the zinc dust distillation of quebrachamine (18, Section II, B) and was subsequently found in R. stricta (51). It is... 

Acid-catalysed hydrolysis of pycnanthinine (195) gives (+)-pleiocarpamine (196), (—)-6,7-dehydro-aspidospermidine (211), and formaldehyde. Reductive... 

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