Covering: 2009 to 2022The Stemona alkaloids, which are found in plant species from the family Stemonaceae, represent a tremendously large and structurally-diverse family of natural products. This review presents and discusses a selection of case studies, grouped by alkaloid class, that showcase the key strategies and overall progress that has been made in the synthesis of Stemona alkaloids and related compounds since 2009. Structural reassignments that have been reported over this period are also identified where necessary.
This report investigates the fundamental basis for rather surprising patterns of reactivity in Brønsted acid-mediated cyclizations of pyrrole substrates bearing pendant Michael acceptors that were identified during syntheses of Stemona alkaloids. Integrated experimental and theoretical studies reveal the profound influence that substituent effects have on the viability of these transformations. Additionally, we identify that electronic effects, in addition to barrier-lowering secondary orbital interactions within transition states, account for the exclusive preference for 7-endo-trig cyclizations over 6-exo-trig cyclizations.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
(R)-Harmonine was synthesised in 15 % overall yield via a six-step sequence exploiting a Z-selective cross-metathesis reaction as its centrepiece. By this strategy, the cis-olefin present in the target could be installed exclusively. The use of an alcohol and an ester as the amine precursors was crucial for isolating the cross-metathesis product from the self-metathesis products. This method was also used to prepare two novel analogues of harmonine.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The natural product parvistemoamide was isolated in 1991 and has ostensibly eluded synthesis. Its distinctive assigned structure represents the first and only Stemona alkaloid within its class. For over 30 years, this structure has influenced biosynthetic proposals concerning this family of natural products. Following synthetic studies and comprehensive analysis of relevant literature, a revised structure of parvistemoamide is proposed that is consistent with the fundamental Stemona alkaloid stemoamide.
Abstract Natural products isolation studies were performed on Dodonaea viscosa plant individuals sampled across seven different populations, which revealed considerable intraspecific variation in the terpene profiles across D. viscosa . In total, 14 ent‐ labdane diterpenoids (seven of which are previously unreported), four ent‐ kauranes (one which is previously unreported), one rare norhopene, and two previously unreported monoterpenoid wax esters were isolated. Exceedingly few terpene wax esters have been reported in Nature and the isolation of these unusual secondary metabolites is particularly notable for this reason. In each case, the proposed structures were elucidated employing various standard one‐ and two‐dimensional NMR ( 1 H, 13 C, NOESY, COSY, HSQC, HMBC) spectroscopic techniques and complemented by IR spectroscopy, mass spectrometry, and polarimetry, where appropriate. Synthetic derivatization and X‐ray crystallographic analysis were also employed to further support or secure structural assignments.
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