Short racemic syntheses of calvine and epicalvine
نویسندگان
چکیده
The intramolecular Pd(II)-catalysed carbonylation of aminoalkenitol was used as a key step in the short racemic syntheses of the ladybird beetle alkaloids calvine and epicalvine. The title compounds have been prepared in 26% overall yield over four steps starting from hexanal and pentenyl bromide. 2007 Elsevier Ltd. All rights reserved. (+)-Calvine 1 and (+)-2-epicalvine 2 are bicyclic piperidine alkaloids found in the haemolymph of the ladybird beetles Calvia 10-guttata and Calvia 14-guttata (Coccinellidae) (Fig. 1). When molested or disturbed, beetles release small droplets of yellow ‘blood’ containing a toxic chemical cocktail at their knee joints (reflex bleeding). As these insects are
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