- A practical and efficient synthetic route to dihydropipercide and pipercide
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Dihydropipercide 1 and Pipercide 2 are examples of hydrophobic insecticidal isobutylamide derivatives isolated from Piper Nigrum L. which have received synthetic attention over the past decade. Novel structural features combining the N-isobutyldieneamide array, found in related natural products such as Pellitorine, with the 3,4-methylenedioxyphenyl moiety, found in insecticide synergists including Piperonyl Butoxide and Sesamex, render these as attractive targets for synthesis. Although a variety of synthetic routes to related natural products have appeared in the literature, practical methods for the preparation of the title compounds were lacking. Convenient and convergent 10-11-step protocols were developed which provided access to gram quantities of the targets. Methyl 6-oxohexanoate 4 was prepared from cyclohexanone enol acetate 3 via a tandem ozonolysis, methanolysis, hydrolysis process. Subsequent olefination and olefin isomerization steps followed by further elaboration provided the targets 1 and 2. Noteworthy features of this methodology include the convenient synthesis of oxoester intermediate 4 and the phenythio radical-induced olefin isomerization of intermediate 6 which afforded high yields of >99.5% E-olefin 13. These are both somewhat uncommon but potentially useful processes which may find further application in organic synthesis.
- Rotherham, Lloyd W.,Edward Semple
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p. 6667 - 6672
(2007/10/03)
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- Concise, Efficient New Synthesis of Pipercide, an Insecticidal Unsaturated Amide from Piper nigrum, and Related Compounds
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Pipercide and piperolein A, unsaturated amides from Piper nigrum, were prepared in overall yields of 21percent and 35percent, 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 Sn2 and the appropriate amines, or from the corresponding carboxylic acids by conventional methodology. - Key Words: Piper; insecticides; aldol; fragmentation; bistin(II).
- Strunz, George M.,Finlay, Heather
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p. 11113 - 11122
(2007/10/02)
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- SYNTHESIS OF NATURAL POLYENE ISOBUTYLAMIDES. STEREOCHEMISTRY OF THE WITTIG REACTIONS
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Unsaturated isobutylamide synthons are employed to make seven natural amides.The (Z)-selectivity of the Wittig reaction towards the newly formed olefinic bond in the seven examples is estimated by 13Cmr.
- Crombie, Leslie,Fisher, David
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p. 2481 - 2484
(2007/10/02)
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- INSECTICIDAL AMIDES. SYNTHESIS OF NATURAL 2(E),4(E),10(E)-PIPERCIDE, ITS 2(E),4(E),10(Z)-STEREOMER, AND RELATED ISOBUTYLAMIDES
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Natural pipercide and its 2(E),4(E),10(Z)-stereomer are synthesised, the latter having superior insecticidal potency and knock down. 10,11-Dihydro- and 10,11-dehydropipercides are also prepared.
- Crombie, Leslie,Denman, Raymond
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p. 4267 - 4270
(2007/10/02)
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