Combination of Machine Learning and Empirical Computation for the Structural Validation of Trirosaline, a Natural Trimeric Monoterpene Indole Alkaloid from Catharanthus roseus.

Chemical investigation of the emblematic Catharanthus roseus led to the discovery of trirosaline (1), the first example of a tris-ajmalicine-type monoterpene indole alkaloid and the first natural trimeric MIA ever reported from this deeply dug plant species. Its structure was primarily elucidated based on NMR and HRESIMS analyses, and the nature of its unique intermonomeric linkages was firmly confirmed based on a combination of empirical computation and ML-J-DP4 study. Its absolute configuration was mitigated by comparison of experimental and TDDFT-simulated electronic circular dichroism (ECD) spectra. A possible biosynthetic pathway for trirosaline (1) was postulated.

Structure elucidation of an aspidofractinine-type monoterpene indole alkaloid from Melodinus reticulatus.

The structure and complete NMR assignments of aspidoreticulofractine, an aspidofractinine N-oxide, are reported. Its structure was elucidated based on a combination of spectroscopic techniques including 1D and 2D NMR, high-resolution mass spectrometry, and electronic circular dichroism.

Unifying the configuration of historical alkaloids from Borreria capitata through an extensive spectroscopic reinvestigation.

Reinvestigation of the structure of borrecapine and borreline through extensive spectroscopic analysis of their authentic samples led to the assignment of their absolute configurations. Newly acquired spectroscopic data determined that the previously assigned relative configuration for borrecapine was incorrect and that the claimed absolute configuration of borreline should be revised to its enantiomer.