Alkaloids of Darlingia darlingiana

Abstract

The structures of eleven alkaloids isolated from Darlingia darlingiana (F. Muell.) L. A. S. Johnson, a Queensland proteaceous tree, have been determined. They comprise a tropene, two pyranotropanes, and eight pyrrolidine alkaloids.

Brønsted Acid Enabled Nickel‐Catalyzed Hydroalkenylation of Aldehydes with Styrene and its Derivatives

“…Evaluation of electronic and loading effects did not lead to significant improvements.S urprisingly,s ubsequent experiments using PhB(OH) 2 as the activator revealed that various alcoholic solvents,i ncluding primary,s econdary,a nd tertiary alcohols,dramatically promoted the reaction (entries [12][13][14][15][16][17][18][19]. Ethanol was optimal, affording the desired product in 90 % yield (entry 17).…”

“…[13] Starting from styrene and aliphatic aldehyde 5,t he natural product darlinine (6) [14] was obtained in 30 %o verall yield [a] Yields of isolated product and diastereoisomer ratios in parentheses determined by 1 HNMR of crude products. First, the hydroalkenylation method could easily be carried out on agram scale with excellent yields.For instance,the reaction of amino acid derived aldehyde 2i with styrene afforded 1.59 g of allylic alcohol 3i (90 %y ield), which could be further transformed into various biologically active molecules.…”

Nicotinic Agonists, Antagonists, and Modulators From Natural Sources

“…The corresponding tertiary amine was not tested. Other alkaloids, including darlingine, have been isolated from Darlingia species (Bick et al, 1979a), but apparently have not investigated for nicotinic activity.…”

Enantiodivergent Combination of Natural Product Scaffolds Enabled by Catalytic Enantioselective Cycloaddition

“…Despite the importance of optically enriched tropanes 1 as building blocks in organic synthesis, [7,8] only afew asymmetric catalytic methods have been developed for the synthesis of compounds based on the tropane scaffold. [9, 12c] In particular, although there are several reports on the [5+ +2] cycloadditions of 3-oxidopyrylium betaines with alkenes for the synthesis of tropanes, [14,15] the corresponding catalytic enantioselective version has remained elusive.T oo ur delight, the kinetic resolution of racemic starting material under the conditions of the enantioselective [3+ +2] cycloaddition described above is very efficient ( Table 2).…”

“…Thet ropane scaffold, that is, 8 -azabicyclo[3.2.1]octane, defines the core structure of more than 600 alkaloids with multiple bioactivities (Figure 1), [7] and tropanes have been subjected to numerous synthetic and biological studies. [8] However,m ost of the synthesis methods yield racemic compounds,and general methods for the asymmetric catalytic synthesis of functionalized tropanes are in high demand.…”