Monoterpene alkaloid

Tietze and coworkers used this process to synthesize the monoterpene alkaloids bakankosin (2-950) and xylostosidine (2-952), as well as analogues starting from se-cologanin (2-951) (Scheme 2.213) [486]. 

Scheme 4.6 The common core structure of many indole monoterpene alkaloids might be accessed through a tetracyclic Zincke aldehyde-derived building block...

We became particularly interested in strychnine when we noticed that the tetracycle 21 (Scheme 4.6), which might be readily available by an intramolecular Diels-Alder cycloaddition of a tryptamine-derived aminodiene, contains much of the complexity of this popular alkaloid target. In fact, this tetracycle is common to many indole monoterpene alkaloids including members of the Strychnos, Aspidosperma, and... 

A synthesis of the monoterpene alkaloid ( )-actinidine has been accomplished through the intramolecular cycloaddition of a substituted pyrimidine (81JCS(P1)1909). Condensation of the diester (756) with formamidine provided the pyrimidine precursor (757) which when heated at its melting point (203 °C) underwent cycloaddition with elimination of isocyanic acid to produce the pyridone (758). Conversion of the pyridone into the chloropyridine was effected with phosphoryl chloride. The chlorine atom was then removed by hydrogenoly-sis over palladium on charcoal to afford the racemic alkaloid (759 Scheme 175). 

A variety of alkaloids based on mono-, sesqui-, di-, and tri-terpenoid skeletons have been characterized, but information about their formation in nature is still somewhat sparse. Monoterpene alkaloids are in... 

Gentianine (Figure 6.123) is probably the most common of the monoterpene alkaloids, but it is... 

Cordell GA (1999) The monoterpene alkaloids. The Alkaloids, Chemistry and Biology (ed Cordell GA) Vol 52. Academic, San Diego, pp 261-376. 

Species in a relatively small number of herbivorous families dominate the list of plant feeders associated with alkaloid-rich foods. Lepidoptera (butterflies and moths) have catholic tastes when it comes to alkaloid-fortified plants, being represented by the families Nymphalidae (calystegine A-3, pyrrolizidine alkaloids lycopsamine type, harman), Arctiidae (senecionine type), Papilionidae (synephrine, isoquinolines), and Pterophoridae (monoterpene alkaloid rhexifoline).6 In addition, beetles (Chrysomelidae) sequester PAs (senecionine), grasshoppers (Acrididae) store senecionine, and aphids (Aphididae) sequester QAs (sparteine and diterpene alkaloids). 

Alangium lamarckii is a medicinal plant that accumulates tetrahydroisoquinoline monoterpene alkaloids for the production of compounds such as emetine, a constituent of ipecacuantha emetic mixture that is used to for the treatment of drug overdose. Historically, this mixture has also been used to treat amoebic dysentery by South American Indians. 

Asymmelric kydroboradon. A key step in an asymmetric synthesis of loganin (I), a key intermediate in the biosynthesis of indole and monoterpene alkaloids, involved... 

Sammes and his group (77JCS(P1)663 78JCS(P1)1293 81JCS(P1)1909) attempted the thermal intramolecular cycloaddition of the substituted pyrimidine 507 possessing an alkyne to produce a monoterpene alkaloid ( )-actinidine (511)(Scheme 64). Upon thermolysis of the pyrimidine 507 at 200°C in a sealed tube, using dimethylformamide as solvent, intramolecular cycloaddition led to the known pyridone 509 in 87% yield by the loss of the amide bridge from intermediate 508. Conversion of the pyridone 509 into the chloropyridine followed by reductive dechlorination afforded racemic actinidine 511. 

Velerianine (546), a monoterpene alkaloid, was synthesized by using a Diels-Alder cycloaddition of heterodiene 542 with enol ether 543 (Scheme 69) (70AG(E)891). Heating cyclopentenecarbaldehyde 542 with the enol ether at 200-203°C afforded a 47% yield of the dihydropyranyl ether 544, which consisted of three diastereomers. Hydrolysis of the ether 544 with acid gave iridodial (545), which was condensed with a nitrogen source to afford racemic valerianine (546). 

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