Stereochemical Study of the Super Large Tetrakis Alkaloid Alasmontamine A by Means of an Advanced Computational NMR

Abstract

1H and 13C NMR chemical shifts of the tetrakis monoterpene indole alkaloid alasmontamine A, with a molecular formula of C84H91N8O12, have been calculated within the DFT framework. Six minimum energy conformers of this alkaloid were identified, and three key configurations that contribute to its NMR shielding constants were established. Several ambiguities in the reported assignment of the NMR chemical shifts of alasmontamine A have been resolved.

Stereochemical and NMR computational study of some natural dimeric bisindole alkaloids

“…At that, the development of complex multistage syntheses is associated with significant material and time costs. Another peculiarity deals with the fact that even in the present "golden age" of NMR, it is far from being uncommon to establish the structure of the erroneously identified newly isolated natural products, resulting in numerous revisions and reestablishments of the originally proposed structures [19,20].…”