The synthesis of pyrrolizidine alkaloids

The pyrrolizidine alkaloids constitute an exceptionally large class of naturally occurring compounds. A number of the alkaloids are hepatotoxic and carcinogenic, but some derivatives have potentially useful physiological properties;A promising but seldom used reaction in alkaloid synthesis is the amidoalkylation of enolizable carbonyl derivatives. The reaction involves electrophilic attack on the enol by an (alpha)-acyliminium ion. This results in formation of a new carbon-carbon bond (alpha) to the nitrogen. This potentially useful reaction was used for the synthesis of several pyrrolizidine alkaloids;The simple pyrrolizidines, trachelanthamidine and isoretronecanol, were prepared from succinimide. The synthesis required only five steps and proceeded in good overall yield. The synthesis is the most direct and operationally convenient route yet reported;An intermediate for the synthesis of heliotridine was also prepared. The synthetic route gave good stereochemical control of the key asymmetric centers. Completion of the synthesis requires only reduction of a methyl ester and removal of a mesityl protecting group

Facile synthesis of N-acyl-2-pyrrolines

In conjunction with our studies of the amidoalkylation reaction,\u27 multigram quantities of N-acyl-2-pyrrolines (1) were needed. Interestingly, only a few methods for the synthesis of this class of compounds had been reported. Stille and co-workers prepared 1 by a novel transition metal mediated isomerization of N-acyl-3-pyrrolines2 and also cyclized (acy1amino)butyraldehydes to produce le3 Although these methods are excellent for qmall-scale preparation, large-scale reactions would entail considerable expense

Conversion of lactones into ethers

Although tetrahydrofurans and tetrahydropyrans are important structural subunits of many classes of natural products,l comparatively few general synthetic methods are known? Since y- and &lactones are readily available: an efficient and versatile transformation to the ether would significantly extend current methodology. The conversion of a lactone to an ether has been accomplished by hydride reduction to a diol followed by cyclization by way of a monotosylate4 or other activated ester.

High temperature affects olive fruit fly populations in California's Central Valley

Olive fruit fly commonly infests olives in California’s Central Valley. Field studies indicate that trap counts for olive fruit fly adults in pesticide-free sites decrease in mid- and late summer and then rebound from September to November. Part of this decline is associated with heat stress that the flies experience in mid-July and August. Studies have shown that adult flies will die within a few days if they cannot access adequate amounts of water and carbohydrates. Flight ability is dramatically reduced when resources are unavailable. Olive fruit fly adults may use black scale honeydew as a carbohydrate source to help them survive hot periods. Heat also affects the fly’s reproduction and immature stages within olive fruit. Geographic information system (GIS) maps may be useful for predicting the risk of olive fruit fly infestation

Biological controls investigated to aid management of olive fruit fly in California

The widespread and rapid establishment of the olive fruit fly in California required immediate changes in integrated pest management (IPM) programs for olives. After finding that resident natural enemies did not provide adequate control, researchers began a worldwide search for parasitoids, with exploration in the Republic of South Africa, Namibia, India, China and other countries. Parasitoids were shipped to California, and most were studied in quarantine to determine the best species for release. Two parasitoid species — Psyttalia lounsburyi and Psyttalia humilis — are now being released throughout the state’s olive-growing regions, and researchers are studying their effectiveness

The synthesis of pyrrolizidine alkaloids

The pyrrolizidine alkaloids constitute an exceptionally large class of naturally occurring compounds. A number of the alkaloids are hepatotoxic and carcinogenic, but some derivatives have potentially useful physiological properties;A promising but seldom used reaction in alkaloid synthesis is the amidoalkylation of enolizable carbonyl derivatives. The reaction involves electrophilic attack on the enol by an (alpha)-acyliminium ion. This results in formation of a new carbon-carbon bond (alpha) to the nitrogen. This potentially useful reaction was used for the synthesis of several pyrrolizidine alkaloids;The simple pyrrolizidines, trachelanthamidine and isoretronecanol, were prepared from succinimide. The synthesis required only five steps and proceeded in good overall yield. The synthesis is the most direct and operationally convenient route yet reported;An intermediate for the synthesis of heliotridine was also prepared. The synthetic route gave good stereochemical control of the key asymmetric centers. Completion of the synthesis requires only reduction of a methyl ester and removal of a mesityl protecting group.</p

Facile synthesis of N-acyl-2-pyrrolines

In conjunction with our studies of the amidoalkylation reaction,' multigram quantities of N-acyl-2-pyrrolines (1) were needed. Interestingly, only a few methods for the synthesis of this class of compounds had been reported. Stille and co-workers prepared 1 by a novel transition metal mediated isomerization of N-acyl-3-pyrrolines2 and also cyclized (acy1amino)butyraldehydes to produce le3 Although these methods are excellent for qmall-scale preparation, large-scale reactions would entail considerable expense.Reprinted (adapted) with permission from The Journal of Organic Chemistry,46(23); 4791-4792. Doi: 10.1021/jo00336a036. Copyright 1981 American Chemical Society.</p

Conversion of lactones into ethers

Although tetrahydrofurans and tetrahydropyrans are important structural subunits of many classes of natural products,l comparatively few general synthetic methods are known? Since y- and &lactones are readily available: an efficient and versatile transformation to the ether would significantly extend current methodology. The conversion of a lactone to an ether has been accomplished by hydride reduction to a diol followed by cyclization by way of a monotosylate4 or other activated ester.5Reprinted (adapted) with permission from The Journal of Organic Chemistry, 46(11); 2414-2419. Doi: 10.1021/jo00324a050. Copyright 1981 American Chemical Society.</p