Alkaloids Robinson-Schopf condensation

The advantages of Robinson s concept was confirmed in numerous total syntheses of alkaloids. One of the most illustrative examples is served by Stevens synthesis of the tricyclic compound coccinelline 45 (Scheme 3.10), the pheromone of the ladybug (ladybird). As was acknowledged in Stevens review article, in less time than it took to write this paragraph, we had developed on paper an attractive approach that relies on one of the oldest reactions known in alkaloid synthesis, namely the classical Robinson-Schopf condensation . This approach involved the retrosynthetic transformation of 45 into the ketopiper-idine derivative 46, which is amenable to disconnection in accordance with the same logic as used by Robinson in the analysis of tropinone. 

Due to its remarkable simplicity, many early approaches to tropane alkaloids utilized the Robinson-Schopf condensation. As pointed out by Sheehan, the... 

As shown before vida supra), the seminal application of the Robinson-Schopf condensation to natural product synthesis was the concise preparation of tropinone (4). In pondering the biogenesis of tropane alkaloids, Robinson put forth a bold hypothesis By imaginary hydrolysis at the points indicated by the dotted lines, the substance may be resolved into succindialdehyde, methyl amine, and acetone, and this observation suggested a line of attack of the problem which has resulted in a direct synthesis. ... 

Pseudopelletierine has been obtained from the bark of the pomegranate tree (Punica granatum L.).2-5 The synthesis of the alkaloid from glutaraldehyde, methylamine, and calcium acetonedicarboxylate was first achieved by Menzies and Robinson.6 The synthetic method subsequently was improved by Schopf and Lehmann,7 and others.8 9 The condensation of a dialdehyde with an amine and acetonedicar-boxylic acid to form a heterobicyclic compound (an alkaloid or alkaloid analog, usually employing mild or so-called physiological conditions) is sometimes referred to as a Robinson-Schopf synthesis. 

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See also in sourсe #XX -- [ , , , , ]

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