Concise, efficient new synthesis of pipercide, an insecticidal unsaturated amide from Piper nigrum, and related compounds

Pipercide and piperolein A, unsaturated amides from Piper nigrum, were prepared in overall yields of 21% and 35% respectively, by a new, short and efficient strategy, in which the key step was the aldol-Grob-type fragmentation sequence recently reported by Sakai et al.. (but using propylene- rather than ethylene glycol). The nor-homologues of these natural products were similarly prepared. In the final steps, the amides could be prepared directly from the esters by Roskamp's method involving treatment with Sn[N(TMS)2]2 and the appropriate amines, or from the corresponding carboxylic acids by conventional methodology.